State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University
State and Local Joint Engineering Laboratory of Methane Drainage in Complex Coal Gas Seam, Chongqing University

为了研究砂岩在渗流−应力耦合作用下的变形局部化破坏特征，利用可视化三轴伺服控制试验系统，结合三维数字图像相关技术（three-dimensional digital image correlation,简称3D-DIC），开展不同排水条件下的砂岩三轴压缩试验，对岩石力学、渗流及其变形局部化特性进行分析，并利用电镜扫描对砂岩破坏后其破裂面微观形貌进行分析。结果表明：排水条件下砂岩的峰值强度和弹性模量高于不排水条件下的值，且随着渗透水压增大，砂岩的峰值强度、弹性模量和泊松比均随之增大，出现贯通裂纹的时间点和渗透率最大值出现的时间点则会提前；当渗透水压相同时，不排水条件下砂岩表面变形场云图的局部化带比排水条件下的更宽，即岩石的宏观裂纹更明显，排水条件下水流将岩石内部的矿物颗粒带走，形成孔洞，其破裂面的表面比不排水条件下更光滑，而不排水条件下颗粒表面明显有片状岩屑附着；所有排水条件下径向变形局部化启动点始终高于轴向变形局部化启动点，平均提高了1.23%，变形局部化径向、轴向启动应力水平均随渗透水压的增大而增大，即启动的时间点更提前，排水条件下砂岩的径向启动应力水平、轴向启动应力水平均高于不排水条件下的值，平均分别提高了1.85%和2.21%，渗透水压相同时，不排水条件下启动应力及应力水平受水压的影响比排水条件更明显。

In order to study the deformation localization failure characteristics of sandstone under the coupling action of seepage and stress, the triaxial compression tests of sandstone under different drainage conditions were carried out using the visualized triaxial servo control test system combined with three-dimensional digital image correlation (3D-DIC). The rock mechanics, seepage and deformation localization characteristics were analyzed, and the micro-morphology of fracture surface after sandstone failure was analyzed using electron microscope scanning. The results shown that the peak strength and elastic modulus of sandstone under drainage condition were higher than those under undrained condition, the peak strength, elastic modulus and Poisson's ratio of sandstone increased with the increasing seepage water pressure, the time point of penetration crack and maximum permeability would be advanced. When the seepage water pressure was the same, the localized zone of deformation field cloud map of the sand surface was wider in the undrained condition than that in the drained condition, i.e., the macroscopic crack of rock was more obvious. Water flow under drained condition took away the mineral particles inside the rock and formed holes, the rupture surface of which was smoother than that under undrained condition, whereas flakes cuttings were obviously attached to the surface of the particles under undrained condition. The initiation point of radial deformation localization was consistently higher than that of axial deformation localization for all drainage conditions, with an average increase of 1.23%. The initiation stress levels of the radial and axial deformation localization increased with increasing seepage water pressure, i.e., the initiation time point was earlier. The radial and axial initiation stress level of sandstone under drainage condition were higher than those under undrained condition, with an average increase of 1.85% and 2.21% respectively. When the water pressure was the same, the initiation stress and stress level were more significantly affected by water pressure in the undrained condition than in the drained condition.

国家自然科学基金资助项目（51974041）；中央高校基本科研业务资助项目（2022CDJQY-011）

许　江，曹　琦，彭守建，等. 排水条件对砂岩力学及其变形局部化特性影响试验研究[J]. 煤炭科学技术，2023，51（9）：189−201

XU Jiang，CAO Qi，PENG Shoujian，et al. Experimental study of the influence of drainage conditions on sandstone mechanics and its deformation localization characteristics[J]. Coal Science and Technology，2023，51（9）：189−201