砂岩渗透作用下声发射及分形特征研究

地下围岩经常处于渗透场-应力场的耦合作用中,为分析在相同渗透压、不同围压下砂岩的变形特性、渗透特性、声发射特征及基于声发射空间分布的分形维数特征,对取自某在建工程的砂岩进行了三轴渗透及声发射试验。研究结果表明:砂岩的抗压强度及变形能力随着围压的升高而增大;渗透率在不同围压下有着相似的演变特征,均是随着应变增大而先减小后增大,并随着围压的升高逐渐减小;声发射的演化过程反映了渗透率大小的变化趋势,渗透率随着渗透试验过程呈阶段性变化,围压越大,声发射现象越滞后;基于柱状分形理论,得到砂岩的分形维数随着试验进行逐渐减小,表明砂岩经历了一个从无序到有序的损伤演化过程,围压越大,对应的分形维数越小。研究结果有助于认识和理解砂岩渗透性的变化机制。

Acoustic Emission Characteristic and Fractal Characteristicof Sandstone under Osmosis

Underground rock mass is often under the coupling action of seepage field and stress field.In the aim of analyzing sandstone''s deformation characteristic, permeability characteristic, acoustic emission characteristic and fractal dimension characteristics based on the spatial distribution of acoustic emission under the same seepage pressure and different confining pressures, the author conducted triaxial seepage and acoustic emission tests on sandstone from a project under construction.Results show that 1) the compressive strength and deformation capacity of sandstone increase with the increasing of confining pressure;2) permeability evolution is similar under different confining pressures, decreasing first and then increasing as strain grows, and decreasing gradually as confining pressure rises;3) the evolution process of acoustic emission reflects the variation trend of permeability, which changes during the penetration test process, and the larger the confining pressure is, the more acoustic emission lags behind;4) based on columnar fractal theory, the fractal dimension of sandstone decreases gradually during the test process, indicating that the sandstone undergoes a damage evolution process from disorder to order, and the larger the confining pressure is, the smaller the corresponding fractal dimension is.The above findings could help understand the variation mechanism of the permeability of sandstone.