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Rock Mech Rock Eng (2012) 45:433438 DOI 10.1007/s00603-011-0197-7
TECHNICAL NOTE
Experimental Study on Viscoelastic Behavior of Sedimentary Rock under Dynamic Loading
L. F. Fan F. Ren G. W. Ma
Received: 9 September 2011 / Accepted: 19 October 2011 / Published online: 5 November 2011 Springer-Verlag 2011
Keywords Sedimentary rock Dynamic viscoelastic
model Experimental study Pressure bar
Stress wave propagation
1 Introduction
Rocks with micro defects do not always behave elastically but sometimes viscoelastically under dynamic loading. Attenuation and dissipation occur when stress wave propagates through an intact rock with micro defects, which cannot be described using traditional elastic rock models (Jaeger et al. 2007). A proper viscoelastic model of rocks is thus important once the stress wave propagation caused by earthquakes, blast, and impact forces is under concern.
A variety of equipments have been used to obtain the dynamic properties of rocks, for example, drop towers, Split Hopkinson Pressure Bars (SHPB), spalling and yer plates (ASM Int 2000). Among these set-ups, the SHPB has been widely used to test the rock dynamic strength, rock fracture, and fragmentation for their easy operation, good repeatability, and accurate results (Li et al. 2005; Li and Ma 2009; Zhou et al. 2010). However, most of these dynamic experiments were conducted with the aims of investigating the strain rate effect and rock failure behavior. The pre-failure behavior of defected rocks under
dynamic conditions is still not clear. Although some viscoelastic constitutive models have been introduced in analyzing stress wave amplitude attenuation, waveform dissipation (Pyrak-Nolte et al. 1990; Jaeger et al. 2007; Li et al. 2010), and mechanical energy dissipation (Perino et al. 2010) in jointed rock mass, these viscoelastic models were mainly proposed for the consideration of the joint effect in jointed rock mass. There still lacks an effective method to determine the viscosity and parameters in the theoretical models for rocks with micro defects.
The present technical note introduces an experimental method to determine the viscoelastic behavior of a sedimentary rock. It is found that a modied three-element viscoelastic model can best t the experimental results. The wave propagation coefcient (wave attenuation coefcient and wave number) of the sedimentary rock are determined. The frequency dependence of the viscoelastic storage modulus and loss modulus is obtained. Discussions of the rock...