An Effective Alternative to the Open Trench Method for Mitigating Ground-Borne Environmental Body Waves: Corrugated Cardboard Boxes Reinforced with Balsa Wood

Abstract

This research develops and evaluates a recyclable corrugated cardboard vibration isolation box reinforced with balsa wood as an alternative to traditional open trench methods for mitigating ground-borne environmental body waves. This study includes designing and testing scaled prototypes, laboratory analyses, prototype fabrication, and full-scale field experiments. In soft ground conditions, ensuring slope stability during deep excavations is a key engineering challenge for open trenches. For this purpose, scaled prototypes were subjected to laboratory tests to assess the resistance of the wave barrier’s wall surface. Numerical analyses were also conducted to evaluate the strength of the internal lattice structure under various loads. A prototype was fabricated for on-site experiments simulating real-world conditions. Field experiments evaluated the vibration isolation performance of the proposed barrier. Accelerometer sensors were strategically placed to gather data, analyzing ground surface vibrations for free field motions to assess the vibration shielding efficiency of both the open trench method and the corrugated vibration isolation box, with and without Styrofoam infill. This study concludes that the recyclable corrugated vibration isolation box is a viable alternative, offering comparable or improved vibration isolation efficiency in soft soil conditions while promoting environmental sustainability using recyclable materials.

1. Introduction

The rapid increase in the world population and the inevitable development of technology have increased the need for new industrial facilities and, accordingly, new settlements. As a result of this necessity, ground-borne vibrations generated by the construction activities at the building sites, the machinery used, and the road and rail traffic that provide the transportation of raw materials and personnel to the established industrial zones can have an impact on nearby structures. Concurrently, heightened awareness within modern urban communities regarding environmental concerns stemming from ground-borne vibrations in densely populated areas has led to a greater desire for improved quality of life and safety. Particularly in densely populated or industrially developed areas characterized by soft ground deposits, the substantial ground vibrations generated by man-made sources in close proximity can disrupt daily life, accelerate structural deterioration, and impair sensitive electronic equipment used in various industries. Addressing these concerns necessitates ensuring that vibration levels near facilities sensitive to such disturbances, such as hospitals, laboratories, schools, concert halls, industrial complexes, and historically significant buildings, are maintained below specified limit values outlined in relevant standards. These vibration levels vary depending on many parameters, such as the dynamic characteristics of the ground environment, the frequency of the vibration, and the location of the source and isolator.

There are two types of vibration isolation systems defined by the location of the vibration source. Active isolation systems are installed close to the source to reduce the vibrations generated by the source, while passive isolation systems are placed in the area away from the dynamic source to be protected from vibration. Dynamic load-induced vibrations affecting the ground and adjacent structures include body waves (such as pressure and shear waves) and surface waves (especially Rayleigh waves). Since surface waves are generated away from the vibration source, the passive isolation system is designed with Rayleigh waves in mind. However, P-waves and S-waves dominate the design of the active isolation system due to their proximity to the vibration source [1].

The deployment of an open trench in favorable geotechnical settings is a common strategy to diminish ground surface vibrations caused by man-made sources on nearby structures. However, the use of deep trenches without lateral support in densely populated areas founded on soft soil deposits is not practical for engineering feasibility, and the vibration-absorbing of solid wave barriers is not at the expected level because of its high impedance. It is well known from both previous experimental and theoretical studies that one of the major factors affecting the insulation performance of wave barriers is the impedance value of the barrier material [2]. In this study, the vibration isolation performance of an effective wave barrier model fabricated using low-impedance materials, corrugated cardboard, and balsa wood, under impact loading is investigated. For this purpose, a series of full-scale field experiments were conducted. One of the reasons for preferring corrugated cardboard used in the production of the wave barrier described in this study is its corrugated structure with high energy absorption capability as well as low impedance. Several studies have been conducted in which corrugated structures exhibit excellent energy absorption capacity and controlled collapse behavior, making them highly efficient for energy absorption applications without considering the effect of impedance [3,4,5,6,7,8,9].

Numerous studies in the literature examine the energy absorption properties of corrugated cardboard in different areas, which is utilized in the production of the wave barrier investigated in this study. Corrugated cardboard is widely used in the literature for packaging to protect products during transport and storage due to its high strength, stiffness, and ability to absorb energy [10]. The behavior of multi-layered corrugated paperboard (MCPB) under shock loading is investigated by Sek, M. A., and Rouillard, V. [11]. Experiments have demonstrated that incorporating a sacrificial crumple element made of virgin corrugated paperboard with an optimal contact area ratio significantly reduces the overall level of the resulting shock response spectrum. Wang, D. [12] obtained the energy absorption model of multi-layer corrugated boards by considering the structure factors. It was concluded that in the liner-elastic section, with the increase of load, the energy absorption per unit volume of multi-layer corrugated boards increased gradually; in the sub-buckling section with local collapse, the energy absorption per unit volume increased rapidly with the increase of compressive stress. Wang, Z. W., and Yu-Ping, E. [13] developed a mathematical model to predict the energy absorption properties of MLCPs with different thickness-to-flute pitch ratios under various ambient humidities simulating the actual logistics environment. Both theoretical and experimental energy absorption curves show that the energy absorption properties of MLCP decrease with the increasing RH, and increase with the increasing of the thickness-to-flute pitch ratio. Kang, C. W. et al. [14] investigated the noise reduction potential of corrugated cardboard, and the modified sheets showed excellent sound absorption and insulation performance.

Investigation of the generation mechanism of ground vibrations produced by man-made sources and their propagation characteristics in soft ground conditions; development of isolation barriers to prevent their adverse effects on building safety, human comfort, and sensitive machines operating in industry are important topics of study in the literature [15,16,17,18,19,20,21]. Ahmad et al. [22] proposed an open trench-type wave barrier model to reduce the adverse effects of ground motions from heavy machinery foundations on vibration-sensitive equipment in the vicinity. Adam and Chouw [23] developed a hybrid numerical model using finite element and boundary element methods and simulated traffic load as an external load to impact load and proposed artificial bedrock to reduce vibrations. Adam and Estorff [24] investigated the isolation of a vertical wave barrier from surrounding building vibrations for active and passive cases depending on the control parameters by simulating train traffic passing through a ballasted railway superstructure to periodically acting impact loads. Çelebi et al. [25] tested open trench, water-filled trench, bentonite-filled trench, and concrete-filled trench types to reduce the wave amplitudes generated by foundation vibrations generated by an electro-dynamic device. Alzawi and El Naggar [1], using a mechanical oscillator, investigated the protective effectiveness of open trench and geofoam-filled trench as wave barriers for attenuation of in-situ vibrations caused by machine foundations in a full-scale experimental study and concluded that the geofoam-filled barrier provides up to 68% wave isolation performance.

François et al. [26] reported on a vibration isolation panel made of expanded polystyrene buried in soil and supported by concrete side panels at a test site near the Brussels public transport company in 1995. The polystyrene grid, whose performance was tested by in-situ hammer blows at the test site, was found to have a lower performance than an open trench. Coulier and Hunt [27] investigated the effect of the rigid wave barrier under harmonic vibrations generated by an artificial electro-dynamic shaker. In a field study conducted by Ülgen and Toygar [28], a 4.5 m deep trench was dug in the propagation path of energy waves generated by an artificial impact hammer, and active and passive isolation conditions were investigated. Naghizadehrokni et al. [29] numerically investigated a geofoam-filled trench in a test site with a sand-gravel mixture soil for attenuation of vibrations generated by a load source with a maximum dynamic force amplitude of 15 kN. Li et al. [30] investigated a new generation of seismic artificial material used to screen waves propagating in wide frequency bands for noise and vibration isolation using LS-DYNA software with a finite element method. Toygar and Ülgen [31] conducted a series of full-scale field experiments with artificially generated ground vibrations in the field to determine the effects of parameters such as the type of vibration source, local site conditions, and geometric dimensions of open trenches on vibration isolation.

Combining vibration and noise barriers, Peplow et al. [32] conducted numerical investigations using the semi-analytical finite element method for ground vibration and the boundary element method for sound propagation. It was found that a typical 3 m noise curtain combined with a buried 4 m concrete wall deployed 80 m from the train line resulted in a noise loss of 12 dB and an 8% reduction in vibration amplitudes. De Bold, R., et al. [33] used the impulse response (IR) test method with a 12 lb instrumented hammer to excite a railway track bed ballast consisting of various contaminated ballast to estimate ballast fouling, and the impulse response results were successfully correlated with the assessed Fouling Index of the ballast. Li et al. [34] proposed a new periodic composite rubber-concrete barrier (PCRCB) with prefabricated assembly characteristics for environmental vibration reduction. The results of the laboratory study showed that the depth of the impact load affects the vibration isolation. A study was conducted by Bose et al. [35] on the use of polyurethane foam trenches to mitigate ground-borne vibrations from sources such as construction and traffic. The efficiency of open and infill trenches was analyzed, with findings indicating that trench depth and material properties, especially for low-density infill materials, are critical for effective vibration reduction. Jauhari et al. [36] conducted a study to investigate ground-borne vibration isolation using dual open and in-filled trenches, addressing the limitations of single-trench solutions. Experimental findings indicated that dual trenches, particularly those filled with geofoam, significantly reduced vertical vibrations, achieving up to 76% reduction with normalized depths, thus demonstrating greater efficiency compared to single trenches. Venkateswarlu et al. [37] conducted a study to provide insights into the behavior of geocell-reinforced beds subjected to vibration loads, analyzing both reinforced and unreinforced. The results revealed that the inclusion of geocell reinforcement significantly improved vibration isolation efficacy, with foundation bed strain reduced by 67%, and a proposed mechanism quantified the diffraction angle and dispersion distance of induced vibrations. Cai et al. [38] conducted a study on mitigating surface waves for ground vibration isolation by proposing a composite in-filled trench made of expanded polystyrene (EPS) and concrete arranged as a periodic structure. The investigation revealed that the proposed trenches effectively reduced vibrations when their attenuation zone matched the surface wave frequencies, outperforming trenches made of concrete or EPS alone. Zou et al. [39] conducted a study on the use of trackside wave barriers to isolate vibration transmission from metro train operations into over-track buildings. Their numerical model revealed that open trenches, especially those in-filled with geofoam, offered superior vibration isolation compared to concrete walls and other materials.

Furthermore, the investigation of harmful vibrations that affect the efficiency of construction activities using vibration monitoring methods has been the subject of numerous studies, particularly in recent years [40,41,42].

A review of previous research shows that there are few experimental studies on low-impedance isolation devices that can effectively attenuate ground vibrations produced by man-made vibration sources, especially when soft ground conditions are considered. In this study, a low-cost effective wave barrier model that can be fabricated with simple labor using corrugated cardboard and balsa, which are low impedance, environmentally friendly, and recyclable lightweight materials, is presented as an alternative solution to open trench isolation to reduce ground-borne vibrations. The box wave barrier can be buried in a monolithic form without lateral support in-ground to absorb the vibration energy directly in the propagation area between the dynamic load source and the zone to be protected.

2. Theoretical Approach for Barrier Materials

In vibration isolation applications, maintaining slope stability in soft ground conditions presents a significant engineering challenge. Deep excavations require soil support along the inner surfaces of the open trench to ensure stability. It is important to note that the configuration of the wave barrier, encased by a thin solid wall, can alter the transmission of incident surface waves from the dynamic source to the affected structure, impacting the damping mechanism of radiated vibration energy. The reflection and transmission of Rayleigh waves at different material interfaces rely on the impedance ratio between the surrounding soil and the outer wall material of the isolation barrier. Thus, the material stiffness of the wave barrier relative to the underlying soil greatly influences vibration isolation performance. An alternative solution to traditional open trench applications for ground-borne vibration isolation was developed using a vibration-damping box wave barrier model constructed from cardboard and balsa wood, which have low impedance. Evaluating the vibrational energy transmitted to the protected area, designated as “E_n” in the literature, relied on the barrier’s impedance [2]. Impedance is calculated using shear wave velocity and material density (Equation (1)). Energy transmission, denoted as E_n, is calculated based on the impedance of the barrier and the impedance of the soil (Equation (2)).

(1)${\mathrm{Z}}_{\mathrm{n}}={\mathrm{c}}_{\mathrm{n}}\times {\mathsf{\rho }}_{\mathrm{n}}$

(2)${\mathrm{E}}_{\mathrm{n}}={\displaystyle \frac{4{\mathrm{Z}}_1{\mathrm{Z}}_2}{{({\mathrm{Z}}_1+{\mathrm{Z}}_2)}^2}}$

Theoretically, high insulation performance can be achieved with barrier models exhibiting either very high or very low-impedance values; however, a rigid wall can alter the mechanics of the vibration wave. The design calculations for the vibration wave barrier, referred to as BCCB Trench (Balsa and Corrugated Cardboard Barrier) in this study, determined the approximate unit volume weight to be in the range of 0.1–0.3 t/m³. Using the formula given in Equation (1), it was concluded that the impedance value of the vibration barrier BCCB Trench is in the range of Z₁ = 25–45 t/m²s. The very low unit volume weight of corrugated cardboard (0.09 t/m³) significantly contributed to the low impedance (Z₁) of the barrier. This low impedance ensures that the behavior of vibration waves when they encounter the barrier is similar to their behavior when entering an open trench. The aim is to create a vibration barrier with an impedance close to that of a cavity, Z₀ = 0, achieving isolation comparable to the vibration performance of an open trench without altering the refraction mechanism of ground waves. Additionally, the high modulus of elasticity of the balsa wood used for the main frame, along with the orthogonal design of the internal reinforcement system, allows the barrier to bear the lateral soil pressure. Thus, the BCCB Trench, with its high strength capable of bearing lateral soil pressure, will prevent lateral stability issues that open trenches can cause in soft soil deposits lacking self-supporting properties. Simultaneously, its low impedance will enable it to achieve insulation performance similar to that of an open trench. Based on this approach, instead of focusing only on high-impedance rigid wave barrier models, this study proposes the development of a wave barrier model based on low impedance, environmentally friendly, and recyclable materials as an alternative solution.

3. Design of Recyclable Corrugated Vibration Isolation Box

The vibration isolation box is constructed using balsa and double-wave corrugated cardboard as main materials. These choices were made due to their ability to create environmentally friendly barriers suitable for underground placement. Their low density, fiber-based composition, and recyclability render them ideal options. Corrugated cardboard is formed by layering at least three sheets of paper into a geometric shape, while double-wave corrugated cardboard comprises five layers, including inner, outer, intermediate, and two corrugated layers (Figure 1). Their strength enables them to support heavy loads, making them highly stackable and useful for crafting telescopic boxes or bulk packaging. The unit volume weight of double-wave corrugated cardboard is approximately 0.09 t/m³.

Balsa wood, commonly employed in architectural projects or crafting hobbyist models, originates from the balsa tree, native to the rainforests of South America and classified as a tropical plant species (Figure 2). Known for its swift growth, the balsa tree possesses a characteristic of low density, typically ranging from 0.04 to 0.38 t/m³ in unit volume weight. Despite its lightweight nature, it boasts considerable strength and serves as an excellent insulator against sound, heat, and vibrations. Due to these attributes, it is frequently utilized as a core material in sandwich composites and finds diverse applications in wind turbine blades, sports equipment, aircraft, boat hulls, and bridges. The elasticity modulus of balsa wood fluctuates between 2100 and 6400 MPa [45].

3.1. Study on Scaled Test Model

The structural framework of the vibration-damping box is crafted from balsa wood because of its exceptional strength. Double-wave corrugated cardboard (Dopel-6 mm, B/C Flute) is employed for the outer surfaces to effectively absorb wave vibrations. Additionally, an orthogonal internal grid system was designed to enable the box barrier to withstand lateral soil pressure when placed in the open trench. Therefore, firstly, considering the soil values of the test field, the lateral soil pressure was calculated. In order to determine the optimum design for the box barrier to be able to withstand the calculated lateral soil pressure in the test site conditions, a series of scaled test models with different mesh sizes, internal grid systems, and different thicknesses were produced (Figure 3). The scaled test models were subjected to 3-point bending tests to determine their strength.

The framework for all scaled test models was crafted from balsa wood. In Scaled Model-1, both the frame and internal structure were fashioned using 4 mm balsa wood, with the main frame thickness set at 5 cm (Figure 4a). For Scaled Model-2, the main frame utilized 4 mm balsa wood, while the internal structure was composed of double-wave corrugated cardboard. The main frame thickness was determined to be 3 cm, with an increase in the internal structure grid density (Figure 4b). In Scaled Model-3, the main frame was constructed using 4 mm balsa wood, maintaining a thickness of 5 cm (Figure 4c). Finally, Scaled Model-4 featured a main frame crafted from 3 mm balsa wood, with the main frame thickness adjusted to 3 cm (Figure 4d). All scaled models were produced with dimensions of 20 × 40 cm, which is 0.05 scale of the prototype. During the production phase of the BCCB Trench prototype, the internal grid spacing will be adjusted to accommodate this scaling factor.

3.1.1. Laboratory Tests for Wall Surface Resistance

The strength of the scaled test models was assessed by subjecting them to three-point bending tests, which were performed using a tensile-compression testing machine capable of applying a maximum force of 50 kN (Figure 5). These tests were conducted at the Construction Materials Laboratory of Sakarya University.

The objective of these tests was to determine the design that could withstand the highest strength against the soil pressure expected at the installation site of the wave barrier. The comparison of results from the three-point bending tests is detailed in Table 1. In order to identify the design capable of withstanding the soil pressure at the location of the wave barrier while minimizing impedance, lateral soil pressure calculations were conducted, considering the soil mechanics values of the test site. The calculations resulted in a soil pressure value of 261.53 kN/m² for P_a (Equation (3)). As a result of the three-point bending tests, it was concluded that Scaled Model-4 can bear the calculated lateral soil pressure and, at the same time, has the lowest impedance.

Taking into consideration the groundwater level at the test site, the finalized height of the BCCB Trench is established at 1.5 m. Given this height, computations utilizing a maximum stress value of 950 kN/m², as determined from the findings of Scaled Model-4, reveal that the combined force the vibration box barrier will withstand is 1425 kN/m. This result confirms that the Scaled Model-4 has the optimum internal lattice design to withstand lateral soil pressure.

(3)$P_a={\displaystyle \frac{1}{2}}\times \gamma \times H^2\times K_a-2\times c^{\prime }\times \mathrm{H}\times \sqrt{K_a}$

3.1.2. Numerical Analysis for Assessing the Durability of the Internal Lattice Structure

The strengths of the scaled test models were obtained by three-point bending tests for the design of the BCCB Trench prototype, and the numerical analysis phase was started to evaluate the durability of the internal lattice structure. Using the data obtained from the laboratory tests, a model validation study was carried out using the finite element method. The validated model enables modification of the internal frame design of the prototype without the need for additional experiments. Thus, the strength of the BCCB Trench can be increased when it is necessary to work on soils with lower bearing capacity than the sample soil in the current study or in deeper excavations. The material properties of the Scaled Model-4, which can withstand the lateral soil pressure calculated with the soil properties of the test area and has the lowest impedance, were entered into SAP2000 (v20) software [48], and load definitions were made by providing boundary conditions suitable for 3-point bending tests, and the model was created. The cardboard and balsa layers of the specimen were defined as plate elements in the Shell Section Layer Definition section. In the experimental studies, the force of 0.698 kN, which is the maximum force value that the Scaled Model-4 can carry, was applied vertically to the top plate center point of the specimen. In order to determine the ideal finite element size for the plate element to transfer the load, the mesh density was first investigated, and it was found that the solution moved away from the solution as the number of finite elements decreased (Table 2).

The optimum result was obtained by solving the model using a 40 × 3.4 mm mesh. The variation of top plate midpoint displacement values according to the number of finite elements is given in Figure 6.

Once the optimal number of finite elements was determined, the suggested model underwent analysis. The displacement at the upper plate’s midpoint of the specimen measures 25.09 mm (Figure 7). The maximum shear stress value was found to be 0.001245 kN/mm².

The load-displacement curves obtained with the finite element model and the load-displacement curves of the experimental results were compared (Figure 8). The numerical results matched the experimental results by 95%.

When the comparative graph is examined, it is seen that according to the experimental results, the top plate middle point displacement value is 23.99 mm. Similarly, according to the model results, it is observed that the upper plate middle point displacement value is 25.09 mm. The finite element model was validated with acceptable accuracy.

3.1.3. Environmental Tests for Moisture Resistance

The effectiveness of the BCCB Trench, a wave barrier constructed from corrugated cardboard, in attenuating man-made ground vibrations is being evaluated in this study. Given that structures buried in the ground are susceptible to damage from groundwater, it is crucial to assess the resistance of the barrier to moisture. To achieve this objective, tests were conducted on small samples of the barrier by subjecting them to water curing in a controlled environment. By immersing the samples in a water tank, the conditions they would encounter when buried underground were simulated. Through these tests, an attempt was made to determine the extent to which moisture infiltration can be withstood by the barrier while maintaining its structural integrity. This assessment is considered vital for ensuring the long-term effectiveness and durability of the BCCB Trench in real-world applications. To evaluate the prototype’s waterproofing capability, pre-prepared prototype samples were placed in a curing tank at Sakarya University’s Building Materials and Hydraulics Laboratory. These samples were first covered with two layers of greenhouse nylon insulation before being submerged in the tank (Figure 9).

During the curing test, the specimens were weighed, immersed in the water tank, and left submerged for 104 days. After this period, they were removed, dried, and weighed again to determine water absorption rates. The results revealed a water absorption rate of 2% for samples. Consequently, it was decided to enhance the water resistance of the BCCB Trench prototype using greenhouse nylon insulation material, which is not conventionally utilized for waterproofing. This approach offers an accessible and cost-effective waterproofing solution without compromising the vibration insulation performance.

3.2. Prototype Fabrication for Site Experiments

BCCB Trench (Balsa and Corrugated Cardboard Barrier Trench) is a box barrier that will be used to absorb ground vibrations produced by man-made vibration sources in the propagation area between the dynamic load source and the area to be protected and is produced as an alternative solution to the open trench isolation system. The production phase of the BCCB Trench prototype has started for field experiments simulating real-world conditions. Considering the groundwater level in the ground where the field experiments will be carried out, it was decided to produce the prototype with a total box-like geometry of 3 m wide, which was decided to be 1.5 m high, in 1 m wide modules. The dimensions of the BCCB prototype were determined based on the framework and inner grid design of Scaled Model-4, which has demonstrated the ability to withstand soil pressure and exhibits the lowest impedance. Following the completion of the dimensioning phase, the construction of the prototype commenced. Initially, 3 mm balsa wood was cut into 3 cm wide pieces to create the supporting frame. These cut pieces were then securely fixed together using a two-phase adhesive to form the framework (Figure 10).

The framework of a module in the BCCB Trench prototype was constructed using balsa wood and subsequently affixed onto double-wave corrugated cardboard. Sheets of corrugated cardboard were precisely cut to the required dimensions to create the internal grid system, which enhances the prototype’s structural integrity. These cardboard pieces were then adhered to the fixed frame using an orthogonal design (Figure 11).

To complete the vibration-absorbing surfaces, double-wave corrugated cardboard was precisely cut and affixed onto the BCCB Trench prototype module, which had dimensions of 1–1.5 m and already contained the internal grid system. Thus, the production of one module of the prototype was finalized (Figure 12).

The BCCB Trench prototype is designed with a box-like geometry to withstand the soil pressure of the open trench where it will be placed. Following the completion of the all-modules production, the prototype was constructed in a box shape, 3 m wide and 1.5 m high, by fixing the modules to each other (Figure 13). Two-phase adhesive was used to fix the modules to each other, and they were supported by corner elements made of balsa wood.

To shield the completed BCCB Trench prototype, intended for burial, to evaluate its efficacy in mitigating ground vibrations from groundwater, the waterproofing process commenced. The entire prototype underwent waterproofing by enveloping it with greenhouse nylon insulation material, validated for its insulation effectiveness through prior water curing tests (Figure 14).

4. Field Experiments for Evaluating Vibration Isolation Performance

4.1. Test Site and Soil Characteristics

A series of field experiments were carried out to investigate the isolation performance of the developed open trench-type vertical wave barrier in preventing the propagation of environmental vibrations. Primarily, the choice of the site for conducting field experiments holds significant importance. Specifically, the varied vibration effects originating from different load sources and the mechanical characteristics of the soil environment have a profound impact on wave propagation. These factors also introduce challenges in interpreting and assessing the recorded vibration data. Therefore, in order to clearly and simply reflect the dynamic characteristics of the load source during the field tests, a site in the Pamukova district of Sakarya province, Turkey, where environmental vibration sources and noise are minimized, was selected (Figure 15). The fact that the test site is spread over a large area without any construction or afforestation in the ground soil provides the opportunity to apply different passive insulation methods.

One of the most important factors in the selection of this site was the soil’s mechanical properties. As a result of geotechnical (SPT) and seismic tests (MASW), it was determined that the test site generally consists of soft clay and loose sand with high plasticity (Figure 16). In addition, shear wave velocity V_s(30) = 184 m/s for the first 30 m soil layer was calculated from the performed analyses. The experimental site, which has unfavorable geotechnical properties and soft alluvial characteristics in terms of construction and wave propagation problems, is an important factor in examining the performance of the wave barrier model proposed for the attenuation of environmental vibrations.

4.2. Measurement Setup in the Free Field

To measure the vibration attenuation performance of the developed prototype vertical wave barrier, a series of experiments were conducted at the test site. Initially, the propagation of waves generated by the load source on the ground surface was measured in a free ground environment without a wave barrier. A sledgehammer with a mass of 5 kg served as the load source in the vibration experiments. The choice of this man-made load source is due to its ability to generate surface waves upon impact. The impact energy was transferred directly to the ground environment by a steel rigid plate placed on the surface without loss (Figure 17).

An AC-3HDG 32-bit high-resolution, low-noise accelerometer system capable of measuring low-vibration motion using capacitive force micromachined sensors was utilized to measure the vibration energy transmitted from the load source to the free ground surface. The measurement system comprises three basic parts: a GPS antenna, power source, and accelerometer main box. Within the accelerometer main box are three MEMS sensors, an ADC digitizer, and a memory where the accelerations are recorded (Figure 18).

The accelerometer was positioned at certain distances from the free ground surface of the test area, and the propagation of the impact energy applied to the vibration source with a sledgehammer as a function of distance and the reduction in vibration amplitude in the no trench condition were obtained (Figure 19). When determining the locations of the accelerometers and the distances to the load source, the passive isolation model was taken into account. To achieve passive isolation, Rayleigh surface waves from a load source should propagate a sufficient distance. This distance should be at least the Rayleigh wavelength (λ), especially for small vibration sources. For this purpose, when determining the location of the open trench-type vibration isolation barrier at the test site, the wavelength was calculated to be approximately λ = 4–6 m, depending on the dominant frequency content of the vibration source (30–50 Hz) and the dynamic parameters of the ground environment. In accordance with the aforementioned considerations, the position of the barrier in the free ground vibration propagation tests was planned to be at least 1.5λ from the load source in order to remain within the boundaries of safety, and the accelerometers were positioned accordingly. The free ground vibration data obtained from these field studies provide a reference for evaluating the isolation performance of the wave barrier.

4.3. Details of Passive Isolation and Infilling Material as Styrofoam

The duration of impact loads is quite short. However, considering the high magnitude of these short-duration loads and soft ground conditions, impact loads on such soils can cause significant deformations. This can result in damaging or discomforting consequences for surrounding structures. When subjected to impact, soil mediums resist not with their cross-section but with their volume. Therefore, having a volume and form capable of absorbing a large amount of energy is crucial to reducing the spread of vibrations. In line with these definitions, it is among the measures that can be taken to use vibration barriers by opening trenches in the ground, that is, by artificially changing the volume and form of the environment.

When a wave barrier is placed close to the load source, it is referred to as active isolation, whereas positioning it near the structure or environment to be protected is termed passive isolation. Due to the stability problem on the basis of the load source and the possibility that the waves reflected from the wave barrier may produce undesirable effects on the system generating the vibration, passive isolation is considered more practical. Consequently, this study utilized a passive vertical wave barrier in experimental investigations aimed at reducing the amplitudes of environmental vibrations propagating through the soil under impact load. Based on the information that vibration amplitudes are attenuated by 20% when the excavation depth is 0.2λ in open trench isolation models [49] and considering the groundwater level at the test site, it was determined that the optimal depth for the wave barrier should be 1.5 m.

Considering the alluvial soil conditions with low shear stiffness at the test site where the experiments were conducted, it was necessary to support the wave barrier from the inner surfaces since the stability problem would arise in the excavated ground to form the wave barrier with a certain depth.

The most crucial factor here is that the material providing lateral stability and supporting the soil, like a retaining wall, must have low impedance. For this purpose, double-corrugated cardboard panels supported by balsa were developed (see Section 3.2).

In open trench wave barrier applications, another potential issue is the safety problems that may arise due to the barrier being open. The most effective solution to this problem is to fill the inside of the barrier. It is crucial that the fill material chosen for the open trench wave barrier has low impedance to ensure that the barrier’s isolation performance is not significantly affected. Therefore, waste polystyrene foam (Styrofoam) with a very low density of 0.01–0.03 t/m³ was used as the filling material. The Styrofoam foams used to investigate the effect of these low impedance waste materials on the vibration isolation performance of the wave barrier consist of 42 cm diameter, 2 m long, rolled bundles, each weighing approximately 2 kg, prepared for recycling in a cornice factory (Figure 20).

4.4. Experimental Program

This research encompasses a series of full-scale field experiments aimed at evaluating the vibration isolation performance of the BCCB Trench, a wave barrier fabricated from low-impedance materials, under impact loading. Considering the alluvial soil conditions and groundwater level of the test site, the trench depth was determined to be 1.5 m. This required the inner surfaces of the open trench to be supported. However, the impedance of the support material must be chosen so as not to alter the transmission behavior of ground waves when they encounter an open trench. To achieve isolation performance similar to that of an open trench without altering the refraction mechanism of ground waves, the BCCB Trench, made from low-impedance materials, was placed into the dug trench. Consequently, when the body waves generated by the sledgehammer hitting the impact plate encounter the BCCB Trench, their behavior will be similar to their interaction with an open trench. Additionally, since the BCCB Trench completely surrounds the interior of the open trench, it will prevent lateral stability issues that could arise from an open trench in the test site, which features soft soil deposits lacking self-supporting properties. Experimental measurements at the test site were conducted in four phases, with vibrations recorded at the same measurement points for all conditions to compare isolation performances. The layout of the accelerometers and the position of the BCCB Trench are illustrated in Figure 21.

In the first phase of the field experiments, the free surface movements caused by the impact load were recorded with accelerometers (No Trench). In the second phase, to compare the isolation performance of the BCCB Trench with the wave absorption performance of an open trench, a trench of appropriate dimensions matching the barrier’s geometry was excavated, and the waves generated during the sledgehammer impact on the impact plate were recorded via accelerometers (Empty Trench). Subsequently, the BCCB Trench, which was fabricated in a box shape with dimensions of 3 m in length, 1.5 m in height, and 0.6 m in width, was placed into the dug trench, and the body waves generated by the sledgehammer impacts were recorded (BCCB Trench). The process of trench excavation and the placement of the wave barrier into the trench, suitable to the dimensions of the BCCB Trench, is given in Figure 22. In the final stage of the experimental measurements, to investigate the effect of low-impedance waste materials on the vibration isolation performance of the wave barrier, the BCCB Trench was filled with waste polystyrene foam (Styrofoam) having a very low density of 0.01–0.03 t/m³, and the vibration produced by the impact load was recorded (Styrofoam-filled BCCB Trench).

In this study, vibration field tests were conducted on four different cases to investigate the vibration isolation performance of a box-shaped wave barrier (BCCB) made of balsa wood and corrugated cardboard, which surrounds the open trench on all sides: No Trench, Empty Trench, BCCB Trench, Styrofoam-filled BCCB Trench (Figure 23). These vibrations are surface waves generated by the energy released from the impact of a sledgehammer on the steel plate surface located on the ground. The impact-induced vibrations produced by the sledgehammer were recorded in the East–West (EW), North–South (NS), and Up–Down (UD) directions by accelerometers placed on the free-field surface. The EW, NS, and UD directions represent the directions parallel, perpendicular, and vertical to the dynamic vibration source, respectively.

The need for sensors capable of detecting weak vibrations at very low noise levels to accurately measure impact-induced vibrations is addressed by the DAC-3HDG series of 3-axis high-precision accelerometers (Figure 18). These devices have a frequency response range of 0–200 Hz, a sensitivity of 2.4 V/g, a measurement range of ±2 g, and a self-noise level of 300 ng/√Hz. Furthermore, each accelerometer has a built-in 32-bit digitizer and can operate in the temperature range from −20 to 80 °C [50].

Ground-induced vibrations typically occur in the frequency range of approximately 1 to 100 Hz [51]. The sensors used in this study are capable of precise measurements within this frequency range. The broad frequency range was also examined in the assessment of vibrations caused by impact. Although the vibration test measurements were conducted with sensors positioned away from any external vibration sources, trace noise such as microtremors, distant excessive motions, or electronic noise in signal processing might still be present [31]. To address this, raw acceleration vibration data were corrected for unwanted axis shifts using MATLAB (R2022b) software, and a 5th-order Butterworth Bandpass filter was applied in the 1–100 Hz range to isolate and remove unwanted noise from the measurement data [52].

5. Field Test Results and Discussion

All tests in this study were conducted under consistent conditions, maintaining the same trench dimensions, load source position, and accelerometer locations. The impact energy generated in manual hammer tests, being a man-made vibration source, can be influenced by various factors that may lead to energy losses post-impact. Therefore, a total of 17 tests were conducted, with at least three tests for each scenario, both with and without barriers. The distribution of these tests is as follows: No Trench (3 tests), Empty Trench (6 tests), BCCB Trench (4 tests), and Styrofoam-filled BCCB Trench (4 tests). A single impact test’s acceleration–time responses of all cases in three directions for each accelerometer are presented comparatively in Figure 24.

It is known that the vibration data generated by the impact loading usually has a sudden and short-term character. Spectral magnitudes change in direct proportion to the intensity of the impact. The higher the impact magnitude, the higher the spectral amplitudes become. The energies of the vibration data also change in direct proportion to their amplitudes. When examining the acceleration–time histories in Figure 24, which are plotted by taking a single sample from the impact tests, it is observed that they exhibit a behavior similar to the general characteristics of the vibration responses measured in general impact tests. In more detailed terms, the acceleration data from the sensor (M129) right in front of the load source reaches a peak value in a very short time (0.01–0.02 s) and is damped within a short duration of time, as under conventional impact. This duration during which the vibration energies are concentrated is approximately 0.6 s. The variations in the amplitudes of the vibration data over time in the NS and UD directions, which are parallel to the directions where the vibration direction is dominant and where the hammer application is applied, exhibit approximately the same characteristics in four impacts. These characteristics are also similar in the vibration data of the other impacts. There are small differences in the maximum amplitudes of the vibrations in Figure 24. These differences arise from the difficulty in producing an equivalent magnitude of energy for each impact test. Some adjustments, which will be explained in the subsections, will be made to approximately equalize the energy levels. The slightly different vibration data obtained from the other accelerometer in front of and behind the barrier is related to the presence and characteristics of the barrier.

In order to quantitatively measure the vibration reduction performance, the concept of Amplitude Reduction Ratio (ARR) proposed by Woods (1968) is widely used [53]. This ratio is defined as the ratio between the maximum spectral amplitude obtained at a specific measurement point in the presence of a wave barrier and the amplitude of the same measurement point under free field conditions. Woods also suggested a maximum Amplitude Reduction Ratio (ARR) of 0.25 for an effective wave barrier. Nevertheless, it is possible that a higher or lower ARR may be more appropriate in certain circumstances. Alzawi and El Naggar (2011) proposed that the effectiveness of a barrier can be evaluated based on displacement, velocity, or acceleration data [1,31]. ARR values are calculated according to the formula given in Equation (4). In order to qualify the percentage of vibration mitigation, Vibration Mitigation Performance, VMP, values calculated according to Equation (5) based on ARR values were used.

(4)$\mathrm{A}\mathrm{R}\mathrm{R}={\displaystyle \frac{\mathrm{M}\mathrm{a}\mathrm{x}\mathrm{i}\mathrm{m}\mathrm{u}\mathrm{m}\mathrm{s}\mathrm{p}\mathrm{e}\mathrm{c}\mathrm{t}\mathrm{r}\mathrm{a}\mathrm{l}\mathrm{a}\mathrm{m}\mathrm{p}\mathrm{l}\mathrm{i}\mathrm{t}\mathrm{u}\mathrm{d}\mathrm{e}\mathrm{b}\mathrm{e}\mathrm{f}\mathrm{o}\mathrm{r}\mathrm{e}\mathrm{i}\mathrm{s}\mathrm{o}\mathrm{l}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}}{\mathrm{M}\mathrm{a}\mathrm{x}\mathrm{i}\mathrm{m}\mathrm{u}\mathrm{m}\mathrm{s}\mathrm{p}\mathrm{e}\mathrm{c}\mathrm{t}\mathrm{r}\mathrm{a}\mathrm{l}\mathrm{a}\mathrm{m}\mathrm{p}\mathrm{l}\mathrm{i}\mathrm{t}\mathrm{u}\mathrm{d}\mathrm{e}\mathrm{a}\mathrm{f}\mathrm{t}\mathrm{e}\mathrm{r}\mathrm{i}\mathrm{s}\mathrm{o}\mathrm{l}\mathrm{a}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}}}$

(5)$\mathrm{V}\mathrm{M}\mathrm{P}=\left(1-\mathrm{A}\mathrm{R}\mathrm{R}\right)\times 100$

In this study, the maximum spectral amplitudes used to calculate the vibration attenuation performance through ARR values are derived from the recorded acceleration data’s absolute maximum values (PGA), the absolute maximum value of velocity obtained by integrating the acceleration data once (PGV), and the absolute maximum value of displacement obtained by integrating the acceleration data twice (PGD). However, to accurately assess vibration performance, it is essential to reduce the standard deviation between the maximum amplitudes of vibrations produced by the hammer impact, meaning that the maximum acceleration amplitude of the load source must be equalized for all conditions, and the vibration attenuation performance must be generalized by averaging multiple data points. In this context, the PGA, PGV, and PGD amplitudes obtained from the accelerometer located immediately in front of the load source (M129) were adjusted to be of the same magnitude in all directions. For example, the PGA values of all impacts in the EW direction for the M129 accelerometer are averaged. This average PGA magnitude is then divided by the PGA magnitude of each individual impact in the same direction and on the same accelerometer. The resulting coefficients, calculated specifically for each impact, are multiplied by the PGA values obtained from both M129 and the other accelerometers for that impact. This process ensures that the acceleration data for each impact in the direction of interest is adjusted according to the amplitude generated by the same load source. The described procedures were also performed for all other directions and maximum spectral magnitudes. Both due to the large amount of data and to provide a clearer understanding of the adjustments made, the data in Figure 24 were adjusted and presented in Figure 25.

An example of the procedure applied to organize the vibration data as if they originated from the same load source is given in Figure 25 as an acceleration–time response. When examining all three directions, it is observed that the vibrations reach their peak amplitudes of equal magnitude within a short period (0.01–0.02 s) and then decay within a short time with similar attenuation trends. These characteristics are similarly close for all spectral magnitudes in other impacts as well. Although the isolation performance of the vibration data will be detailed in terms of spectral magnitudes in the section below, some general conclusions can be drawn from the acceleration–time relationships in Figure 25. The first of these is that, especially in the NS direction, the vibration amplitudes measured immediately behind the barrier are lower compared to the no-barrier condition. This indicates that the barriers significantly reduce vibrations. Additionally, it was found that barriers with different characteristics cause differences in the behavior of time-dependent acceleration vibrations. Another observation is that the vibration amplitudes obtained from the accelerometers decrease as the distance from the load source increases, due to both the barrier and the damping effect of the soil relative to the distance.

Secondly, the averages of the adjusted spectral magnitudes from the impact tests were calculated for each direction of each test condition, resulting in the average spectral magnitudes. After obtaining the spectral magnitudes, the ARR values were computed using Equation (4) and are presented in Figure 26.

Figure 26 shows that the BCCB Trench and the Styrofoam-filled BCCB Trench provide a minimum of approximately 50% improvement in overall vibration reduction performance across all cases. However, the vibration reduction performances vary depending on the directions of the load-induced vibrations and the positions of the accelerometers, as calculated from the maximum spectral magnitudes of different test conditions. The NS direction, perpendicular to the vibration barrier, is the primary direction in which vibrations generated by the hammer impact are effective. Vibration isolation was designed considering the impact in this direction. This design’s effectiveness in reducing vibrations is evident when examining the ARR values calculated for the M131 accelerometer positioned directly behind the barrier in the NS direction. Firstly, the vibration reduction performance for all conditions was analyzed in terms of PGA magnitudes. It is well known that an empty trench typically provides better isolation performance than barrier-filled trenches, and this study demonstrated approximately 88% vibration mitigation performance. The vibration reduction performances for the BCCB Trench and the Styrofoam-filled BCCB Trench were calculated to be approximately 88%. Additionally, all three conditions fall within the effective isolation region suggested by Woods, with a maximum ARR value of 0.25. These calculations highlight that the BCCB Trench, which contributes to lateral stability in the open trench condition in the NS direction, exhibits both similar behavior and effective vibration performance to that of an open trench, making it a significant finding for practical applications. The infill material placed inside the BCCB neither contributed to nor negatively affected the vibration mitigation performance of the Empty Trench and the BCCB Trench.

Examining the M130 accelerometer positioned in front of the barrier reveals that the PGA_ARR values calculated for the BCCB Trench and the Styrofoam-filled BCCB Trench are similar and relatively higher than those for the Empty Trench condition. This can be explained by the BCCB Trench’s impact on the reflection of vibration waves recorded by the M130 accelerometer directly in front of the barrier. To express this quantitatively, in the BCCB Trench and Styrofoam-filled BCCB Trench conditions, the vibration amplitudes increased by approximately 30% and 15%, respectively compared to the No Trench condition, due to the combination of reflected and incoming vibration waves. In the Empty Trench condition, the vibration amplitudes decreased by approximately 5% compared to the No Trench condition. The inner filling material placed inside the barrier demonstrated better performance than the BCCB Trench by increasing the vibration amplitudes in front of the barrier less than in the BCCB Trench condition. The PGA_ARR values obtained from the M132 and M133 accelerometers, located 2.6 m and 9.6 m behind the barrier, are approximately the same across all test conditions, averaging 0.35 and 0.63, respectively. When the PGAARR values of the accelerometers are analyzed, it is observed that as the distance of the accelerometers behind the barrier to the barrier increases, the effectiveness of the barrier decreases and the vibration mitigation performance also decreases.

When analyzing vibration mitigation performances in terms of PGV values, similar behavior to PGA values is observed. For the M131 accelerometer located directly behind the barrier, the PGV_ARR values for the Empty Trench, BCCB Trench, and Styrofoam-filled BCCB Trench conditions are 0.14, 0.22, and 0.18, respectively. These values are situated within the effective isolation region suggested by Woods, as observed with the PGA data. When examined in terms of another metric of Vibration Mitigation Performance (VMP), the vibration reductions in the Empty Trench, BCCB Trench, and Styrofoam-filled BCCB Trench cases are 86%, 78%, and 72%, respectively. This means that the best performance in terms of PGV magnitudes is provided by Empty Trench, followed by BCCB Trench and Styrofoam-filled BCCB Trench. The vibration mitigation performance decreases by 8% when BCCB is placed in Empty Trench. However, if Styrofoam material is placed inside the BCCB, the vibration performance is increased by 6% compared to the BCCB Trench case. Hence, the infill material provided additional vibration mitigation performance to the BCCB Trench and made it closer to the performance of the Empty Trench.

Examining the PGV_ARR values obtained from the M130 accelerometer positioned in front of the barrier indicates that, similar to the PGA data, the barrier conditions reflect certain levels of vibration waves, resulting in higher vibrations in front of the barrier compared to the empty trench condition. The PGV_ARR values obtained from the M132 accelerometer, located behind the barrier, are found to be close to those from the M131 accelerometer positioned immediately behind the barrier. This demonstrates that the barrier’s effect is successfully maintained even 2.6 m behind the barrier. The vibration mitigation effect of the barrier decreases with increasing distance. To express these effects in terms of VMP values for the Empty Trench, BCCB Trench, and Styrofoam-filled BCCB Trench: 85%, 75%, and 80% for the M132 accelerometers, and 66%, 53%, and 54% for the M133 accelerometers, respectively. It can be inferred from this information that the Empty Trench case performs better than the other cases even at increasing distances. In addition, the performances of BCCB Trench and Styrofoam-filled BCCB Trench are close to each other. Overall, the vibration performance based on PGV data is better with increasing distance than the PGA data suggests. In quantitative terms, the vibration mitigation performances of the PGV data are about 2%, 11%, and 7% lower than those of the PGA data for the Empty Trench, BCCB Trench, and Styrofoam-filled BCCB Trench cases, respectively.

When considering the vibration reduction performance calculated from PGD data, similar behaviors to those observed in the PGV data are noted. These similarities include the reflection of vibration waves by the barrier in front of the accelerometer, the decrease in vibration mitigation performance with increasing distance behind the barrier, and the advantages/weaknesses of the barrier conditions in terms of vibration mitigation performance compared to each other. An important difference is that the ARR coefficients calculated for the position immediately behind the barrier are slightly higher. For the Empty Trench, BCCB Trench, and Styrofoam-filled BCCB Trench conditions, these values are 0.18, 0.37, and 0.31, respectively. In other words, the VMP values are 82%, 63%, and 79%, respectively. Although good vibration performance is achieved in all barrier conditions in UD, the BCCB Trench and Styrofoam-filled BCCB Trench were slightly outside the effective isolation region commonly accepted in the literature.

In the EW direction, the best isolation performance was observed for PGD and the lowest for PGA, while the opposite behavior was observed in the NS direction. According to PGA values, the Empty Trench case provides the best isolation performance, while the Styrofoam-filled BCCB Trench case has the worst isolation performance compared to the others. The superiority and weaknesses of the barriers in their performance relative to each other are similar for the EW–NS directions according to the PGA results. According to the PGV and PGD data, the best isolation performance was still achieved in the Empty Trench case, while the infill material used in the BCCB Trench improved the vibration isolation performance compared to the BCCB Trench case. In terms of VMP values of the PGA values, the Empty Trench case provides 12% better performance than the BCCB Trench case, while in terms of PGV and PGD data, this performance is about 6% and 2%, respectively. In the BCCB Trench case, the vibration mitigation performances were found to be approximately the same according to the PGA values, while in terms of PGV and PGD values, they were found to be reduced by approximately 9% and 13%, respectively. In addition, if the average mitigation performances of all barrier cases are evaluated in terms of the zone of adequate isolation limits proposed by Woods, the vibration isolation performance for PGD and PGV data is within or very close to these limits, while the PGA values are outside this zone. Barriers reflect vibrations that hit them perpendicularly. Therefore, when examining the ARR values for PGA, PGV, and PGD obtained from the M130 accelerometer positioned in front of the barrier, it can be noted that the vibration waves in the EW direction are not as affected by reflected waves as those in the NS direction. In other words, the barrier in the EW direction does not reflect the waves effectively. Considering the effective direction of vibrations (in NS direction), the isolation performance of the barrier decreases as the distance of the accelerometers behind the barrier increases. However, this behavior in the EW direction is valid up to a certain distance, beyond which other factors come into play. As observed in this study, the ARR values calculated for all spectral magnitudes from the M132 accelerometer located 2.6 m from the barrier increase significantly compared to those calculated immediately behind the barrier. These increases are around 80–90%. However, when examining the ARR values of the spectral magnitudes calculated from the M133 accelerometer located 9.6 m from the barrier, they are lower than those from the M132 accelerometer. This is because the barrier’s performance decreases with distance, and the vibration amplitudes in the EW direction are lower. In other words, vibrations with reduced amplitudes due to the barrier are further attenuated by the ground as the distance increases.

In the UD direction, the average VMPs of all cases according to the PGA, PGV, and PGD values obtained from the sensor right behind the barrier are calculated as 50%, 56%, and 73%, respectively. The performance of the barrier conditions with respect to each other is similar to that in the EW direction. For all spectral amplitudes, the Empty Trench case provides the best isolation performance, while the Styrofoam-filled BCCB Trench case has the worst isolation performance compared to the others. However, according to the M131 accelerometer data behind the barrier, the calculated vibration reduction performance for all spectral magnitudes and each barrier condition is lower than in the EW and NS directions. This suggests that the effectiveness of the barrier in the UD direction is less compared to the other directions. Additionally, vibrations behind the barrier generally decrease with distance. Examining the ARR values calculated from the spectral magnitudes of the M130 accelerometer in front of the barrier indicates that, similar to the EW direction, waves do not effectively reflect off the barrier.

6. Conclusions

This study proposes an innovative and unique vibration barrier to mitigate the impacts of vibrations caused by environmental factors. To evaluate the performance of this low-cost wave barrier, which is easily constructed using low-impedance, environmentally friendly, and recyclable materials such as corrugated cardboard and balsa wood, a series of full-scale field experiments were conducted. To determine the barrier’s resistance to loads arising from lateral soil stability, three-point bending tests were carried out in a laboratory setting. Additionally, the barrier’s durability against environmental conditions at the test site, particularly the effects of groundwater, was ensured through the application of insulation. As an alternative to open trench isolation, this wave barrier aims to reduce ground vibrations generated by human-made sources. With an impedance close to that of a void, the BCCB Trench provides effective vibration isolation without disrupting wave refraction mechanisms. The high modulus of balsa wood and the internal reinforcement design allow the barrier to withstand lateral soil pressure, preventing stability issues in soft soil. Therefore, the BCCB Trench offers robust lateral support while providing isolation comparable to traditional open trenches, demonstrating that low-impedance models are viable alternatives in vibration isolation applications. Furthermore, to investigate the impact of low-impedance waste materials on the wave barrier’s vibration isolation performance, the BCCB Trench was filled with very low-density waste polystyrene foam (Styrofoam). The barrier’s vibration reduction performance was analyzed by calculating the Amplitude Reduction Ratio values derived from the spectral magnitudes obtained from accelerometers placed behind and in front of the barrier in the direction of vibration propagation from the load source.

The measurement metric used to examine the barrier’s vibration reduction performance was the ARR value, calculated with PGA values in the primary vibration direction (NS). It was found that the BCCB Trench and the Styrofoam-filled BCCB Trench demonstrated vibration isolation performance comparable to that of an empty trench, with a reduction performance of approximately 88%, placing them within the effective isolation region suggested by Woods. Additionally, the barrier showed successful vibration isolation properties in terms of both PGV and PGD magnitudes. In the conditions of Empty Trench, BCCB Trench, and Styrofoam-filled BCCB Trench, the PGVARR values for the accelerometer located immediately behind the barrier were found to be 0.14, 0.22, and 0.18, respectively, indicating that these values fall within Woods’ effective isolation region. Additionally, when examining Vibration Mitigation Performance (VMP), it was observed that placing the BCCB Trench in an empty trench only reduced the vibration mitigation performance by 8%. This demonstrates that the BCCB Trench is a viable alternative to an empty trench as a vibration isolation tool. In summary, the newly developed barrier performs within the effective isolation region proposed by Woods, making it a viable alternative to other barriers for practical or field applications.

Examining the data from the accelerometer placed directly in front of the barrier reveals that, with the presence of the BCCB Trench, vibration amplitudes increased by approximately 30% compared to the No Trench condition, due to the combination of reflected and incoming vibration waves. In contrast, the Styrofoam-filled BCCB Trench showed an increase of only 15%. These results indicate that the internal filler material increased the vibration amplitudes in front of the barrier less than the BCCB Trench condition, thereby demonstrating that the Styrofoam-filled BCCB Trench exhibits superior performance.

The strength of the scaled test models for the vibration barrier was determined through three-point bending tests, and it was found that the BCCB Trench was constructed with sufficient strength to withstand the lateral soil pressure of the test site. The box barrier’s load capacity to withstand soil stress will enable its use in trenches of greater depth where lateral stability issues may arise. Additionally, numerical analyses were conducted to evaluate the durability of the barrier’s internal lattice structure. The model, validated using the finite element method, allows for modifications to the prototype’s internal frame design without requiring additional experiments. This enables the BCCB Trench’s strength to be enhanced for use in soils with lower bearing capacity or for deeper excavations compared to the sample soil in the current study.

The most distinguishing feature of the BCCB Trench compared to other vibration isolation methods is its excellent vibration isolation performance combined with the use of recyclable materials easily obtainable from factories. This makes the primary raw materials of the barrier model both readily accessible and economical. Additionally, the BCCB Trench can be produced with simple labor without the need for professional engineering services, easily transported to the field, and installed as a single unit, making it stand out in terms of practical application. Furthermore, in order to evaluate the moisture resistance of BCCB Trench, small samples were tested by water curing, and the decision was made to use a greenhouse nylon for waterproofing, which made the BCCB Trench prototype water resistant. This approach provided an accessible and cost-effective waterproofing solution without compromising vibration isolation performance. While these measures have yielded promising results, further studies will explore additional protective coatings, such as membrane-based layers, to potentially increase long-term performance in diverse environmental conditions. When all the results are evaluated, it is seen that BCCB Trench is an applicable product that has a strong ground vibration isolation performance in the direction it is effective and resistant to environmental conditions.

Author Contributions

Data curation, A.S., M.B.N. and B.İ.; investigation, A.S., E.Ç., M.B.N., O.K. and B.İ.; methodology, A.S. and E.Ç.; project administration, E.Ç.; software, A.S. and M.B.N.; visualization, A.S., M.B.N., O.K. and B.İ.; Writing—original draft, A.S., E.Ç., M.B.N., O.K. and B.İ.; Writing—review and editing, A.S., E.Ç., M.B.N., O.K. and B.İ. All authors have read and agreed to the published version of the manuscript.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The authors are unable or have chosen not to specify which data were used.

Conflicts of Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Footnotes

Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Figures and Tables

Figure 1. Double-wave corrugated cardboard [43,44].

Figure 2. Balsa wood [46,47].

Figure 3. Scaled test models of the vibration box.

Figure 4. Different grid internal frames: (a) Scaled Model-1, (b) Scaled Model-2, (c) Scaled Model-3, (d) Scaled Model-4.

Figure 5. Determination of the strength of scaled models by 3-point bending tests.

Figure 6. The variation of top plate midpoint displacement values according to the number of finite elements.

Figure 7. Analyzing the model of Scaled Model-4 in SAP2000 software.

Figure 8. Comparison of numerical results with experimental results.

Figure 9. Placing the samples in the water tank for curing test.

Figure 10. Framework system of a module of the BCCB Trench prototype.

Figure 11. Creating the internal grid system.

Figure 12. A completed module of the BCCB Trench prototype.

Figure 13. The completion of the BCCB Trench prototype by assembling the modules.

Figure 14. Waterproofing of the BCCB Trench prototype.

Figure 15. The site of the wave barrier vibration performance test.

Figure 16. Soil profile of the test site.

Figure 17. The dynamic load source and application method.

Figure 18. The vibration measurement system.

Figure 19. The vibration measurements under impact loading in the barrier-free condition.

Figure 20. The filling material: polystyrene foam (Styrofoam).

Figure 21. Layout of measuring points from a schematic view of the monitoring field test area with BCCB Trench.

Figure 22. The process of trench excavation and the placement of the BCCB Trench.

Figure 23. A general overview of the experimental measurements: (a) No Trench, (b) Empty Trench (c) BCCB Trench, and (d) Styrofoam-filled BCCB Trench.

Figure 24. Comparative acceleration−time responses of a single impact test for each accelerometer.

Figure 24. Comparative acceleration−time responses of a single impact test for each accelerometer.

Figure 25. Comparative of normalized acceleration−time responses for each accelerometer.

Figure 25. Comparative of normalized acceleration−time responses for each accelerometer.

Figure 26. Comparison of normalized amplitude reduction ratio (ARR) in three components of instruments for (a) PGA, (b) PGV, and (c) PGD values [53].

Table 1

Comparative results of 3-point bending test.

Scaled Model	Dimension (cm)	Internal Frame Type	Max. Force (N)	Max. Displacement (mm)	Max. Shear Stress (N/mm2)	Density (kg/m3)
1	20 × 40 × 6.2	Balsa	2414.06	17.59	1.54	179
2	20 × 40 × 4.2	Corrugated Cardboard	501.56	15.50	0.68	130
3	20 × 40 × 6.2	Corrugated Cardboard	940.63	23.13	0.58	134
4	20 × 40 × 4.2	Corrugated Cardboard	698.44	23.99	0.95	123

Table 2

Optimization of the mesh density.

Mesh Size		Number of Elements	Upper Plate Midpoint Displacement (mm)
a (mm)	b (mm)
8.35	10	960	27.84
16.7	20	240	26.72
33.4	40	60	25.09
100.2	200	4	12.69
200.4	400	1	0

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