There is potential danger of conical shear failure surface in karst cave roof under pile foundation load. To understand the mechanical and failure characteristics of rocks under such conditions. In this study, an auxiliary device consisting of an indenter and a hollow support combined with a servo-controlled mechanical equipment was used to perform mixed compression-shear tests. The laboratory tests were studied numerically by finite difference methods. This study set up 4 groups of height variables 20, 30, 40, 50 mm and 3 groups of aperture variables 20, 30, 40 mm. AE (acoustic emission) tests are adopted to study the failure characteristics of specimen. The experimental results show that the peak load increases with the sample height while decreases with the aperture of support. This paper defines an apparent elastic modulus in terms of displacements and loads, which increases with height by 42.12, 51.7, and 49.00 KN/mm for apertures from 20 to 40 mm. The AE data show that the ratio of RA (ratio of rise time to maximum amplitude) to AF (average frequency of AE count) gradually increases as the support aperture increases, indicating that the aperture is approximately close to the radius of the indenter and that shear damage is approximately significant. The numerical simulation results show that the shear stress is the largest at the position where the upper surface of the specimen contacts with the indenter, and the displacement is the largest at the position where the lower surface of the specimen overlaps with the support hole. The extrusion phenomenon caused by dilatation is the main reason for the tensile failure detected during the experiment.

溶洞顶板在桩基荷载作用下存在圆锥剪切破坏面的潜在危险。了解岩石在这种条件下的力学和破坏特征。本研究采用由压头和空心支撑件组成的辅助装置与伺服控制的机械设备相结合来进行混合压剪试验。通过有限差分方法对实验室测试进行了数值研究。本研究设置了 4 组高度变量 20、30、40、50 mm 和 3 组孔径变量 20、30、40 mm。采用AE（声发射）试验来研究试件的失效特征。实验结果表明，峰值载荷随样品高度的增加而增大，随支撑孔径的增大而减小。本文定义了位移和载荷方面的表观弹性模量，对于 20 至 40 mm 的孔径，表观弹性模量随高度增加 42.12、51.7 和 49.00 KN/mm。AE数据显示，随着支撑孔径的增大，RA（上升时间与最大幅度的比值）与AF（AE计数的平均频率）的比值逐渐增大，表明孔径近似接近压头半径，并且剪切损伤大约是显着的。数值模拟结果表明，试件上表面与压头接触位置剪应力最大，试件下表面与支撑孔重叠位置位移最大。膨胀引起的挤压现象是实验中检测到的拉伸破坏的主要原因。