| Jointed rock mass in underground engineering is the most common type of nonhomogeneous, non-continuous complex media, and there are often a lot of joints and cracks in such media, bringing the stability of underground structures constructed in the rock mass with the security risks. Therefore, the mechanical characteristics and characteristics of fracture evolution of jointed rock mass has long been one of the hot and difficult problems in the study of rock mechanics. This paper, in combination with the National Natural Science Foundation of China(51404255), integrated use of physical modeling and numerical simulation, studied preliminarily the mechanical, acoustic properties and fracture evolution characteristics of jointed rock mass with different joints parameters under uniaxial compression, in order to lay the foundation for further study on the evolution of the internal three-dimensional fracture in large-scale model tests. The main results and conclusions are as follows:(1) Detecting ultrasonic velocity and monitoring acoustic emission of three groups of rocklike material, it obtained variation characteristics of velocity, amplitude and ringing count. With the increase of aggregate proportion in similar material, the velocities of three similar material emerged gradually decreasing trends, and have different fuctional relations with the ratio of the elastic modulus and density, compressive strength and tensile strength. Focusing mainly range of acoustic emission amplitude decreases and the occurrence of maximum amplitude is lagger than peak intensity. The strength order of acoustic emission signal when three similar materials are destroying is that S class> H class> F class.(2) Through uniaxial loading tests of single jointed rock mass model, the study obtains the relationship between different jointed parameters and the peak intensity. When the thickness of joint increases from 0.5mm to 3.0mm, the peak intensity decreases 36.09%. When the joint angle increases from 0° to 90°, the peak strength of jointed rock mass exhibits firstly decreases and then increases. In the joint angle is 45°, the peak intensity obtains the minimum. When the penetration of joint increases from 0.2 to 1.0, the peak intensity decreased 30.47%.(3) By analysis of positioning of acoustic emission and digital photography during rupture process, the study obtains events location of acoustic emission and fracture characteristics under different parameters of joints.When the joint thickness is between 1.0mm and 1.5mm, the surface of specimen will form a penetrating tension-type rupture surface. In other cases on the surface of the samples there is often compression-shear and tension with complex fracture plane. When the pre-joint angle is less than 30°, the specimen surface will form a large shear fracture surface through the pressure. When the joint angle is greater than 45°, fracture surface of the specimen is vertical and through tensioning. When the penetration of joint is between 0.2 and 0.4, the main fracture surface is vertical tension and oblique compression-shear fracture plane. When the joint of penetration is between 0.6 and 1.0, crack fracture surface is mainly vertical tension rupture surface.(4) Based on tests of physical models, the single jointed rock mass had been calculated by ansys numerical software, focusing on the influence law of equivalent stress distribution of a single joint jointed rock mass with different parameters, Which reveals stress evolution of internal space of the jointed rock mass under uniaxial compression. |
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