摘要
实际岩石比如沉积形成的岩石往往是裂隙和孔隙并存的孔隙介质.由于扁状的裂隙与近似球形或圆管形的孔隙具有不同的可压缩性,当孔隙介质受压时,液体会从易压缩的裂隙中挤出流入不易压缩的孔隙中,这种挤喷流会引起弹性模量的频散和能量的耗散.着重研究了裂隙挤喷流和液体可压缩性对孔道变形的影响,推导出了动载荷作用下排水体积模量的表达式.与挤喷流相关的裂隙附加柔度会引起排水体积模量随频率变化,使得孔隙介质呈现黏弹性.频率越高,模量的实部越大,岩石抵抗变形的能力越强.而模量的虚部体现了挤喷流对能量的耗散.裂隙密度主要决定模量频散的幅度以及能量耗散的强度,且裂隙密度越大,模量频散幅度越大,能量耗散也越强.裂隙的纵横比主要决定模量频散速率最快或能量耗散最强时对应的特征频率.若孔隙介质中不含有裂隙,即裂隙密度是0时,排水体积模量退化为Biot理论中的排水体积模量.
Sedimentary. rocks are typical porous media which usually contain both cracks and pores. Liquid in rocks will be squeezed out of flat cracks and then flow into spherical pores when rocks are under pressure because cracks are much softer than pores. This kind of flow between cracks and pores is squirt-flow which usually induces elastic modulus dispersion and wave attenuation. This paper studies the effects of squirt-flow as well as the liquid compressibility on the deformation of pore space and derives the expression of drained bulk modulus under dynamic loads. There exists a crack compliance in the expression of drained bulk modulus. The crack compliance contains both the contribution of squirt-flow which is caused by pressure difference between cracks and pores and the contribution of the compressibility of the liquid in cracks. The additional compliance brings about dispersion on drained bulk modulus. The real part of drained bulk modulus increases as frequency increases which means that at high frequency rock becomes stiffer, the imaginary part of drained bulk modulus represents the energy loss in the squirt-flow. Crack density mainly decides the modulus dispersion amplitude and the squirt-flow intensity. The crack aspect ratio mainly decides the characteristic frequency of squirt-flow. The expression of drained modulus in this paper reduces to Biot expression when crack density equals zero.
出处
《力学学报》
EI
CSCD
北大核心
2013年第3期395-405,共11页
Chinese Journal of Theoretical and Applied Mechanics
基金
国家自然科学基金资助项目(41174110)~~
关键词
裂隙
孔隙介质
挤喷流
排水体积模量
附加柔度
模量频散
crack, porous medium, squirt flow, drained bulk modulus, additional compliance, modulus dispersion
