In-situ Test For Shear Strength Of Platy Rock Mass And Numerical Simulation Of Mechanical Effect Of Platy Planes

Strength of a rock mass is largely determined by the strength of structure planes in the rock mass, and this is especially true to platy rock mass. It is significant to get the strength parameters of structure planes in the rock mass directly by test in situ both for the stability analysis of rock mass and for engineering design. In order to control test loads, traditional test method needs a set of cumbersome reaction equipment, which results in a high cost and bring more difficulties in the test, especially for the test in mountain area.In order to understand the strength property and the mechanical influence of platy rock mass and offer some practical references for the design of extra high voltage network foundation or other anchor foundation, a load test in situ for the strength of the platy planes in dolomite platy rock mass near Xiaoyouying of Fangshan District in Beijing is carried out, and a test method utilizing local tectonic stress in the tested rock mass is researched in this test. Based on this test, a set of numerical simulation are developed in the mechanical influence of structure plane.In this thesis, the regional geological conditions and tectonic stress of the test site are collected, through in-situ investigations and related tests. Then the relationship between rock mass structure and the tectonic stress is found out. Thereby rock mass basic quality is classified to IV, the performance characteristics of a relatively hard and relatively broken ~broken rock. A new method to test shear strength of structure plane is designed according to regional conditions.According to the relationship between the attitude of platy planes and the direction of tectonic stress in the rock mass, three test rock blocks, laterally disconnected from their mother rock in different forms, are dug out vertically on the horizontal ground of the test site. Beside two parallel vertical free surfaces, a certain free room is left between test block and its mother rock. This room is just a reaction frame for loading, in which a jack and steel pads can be put and horizontal test loads can be applied vertically to the free surface of the test block. This makes our test get rid of cumbersome reaction equipment totally. The state of the tectonic stress in the test block changes with the forms of block disconnection from its mother rock, and the varied tectonic stresses in different states, adding upon the stresses caused by horizontal test loads, forms different normal and tangential stresses in the preconcerted shear plane at last. By means of test method mentioned above, our test is successfully completed with same gains as follows. The strength parameters of the platy rock mass (c, ?) are obtained. It is a useful attempt, which will be a helpful reference for the design of extra high voltage network foundation and for the stability analysis of engineering rock masses in mountain areas with similar platy rock mass.Meanwhile, the rock anchor mechanism studies pay less attention to the changes of stress and strain and the stability of rock mass in the uplifting process. Thus, based on the rock mass shear strength values (c,φ), the uplifting process is simulated in the use of ANSYS, FLAC3D. The models are designed to be the same rock layer and unified lithology parameter. The Relation of stress and displacement is simulated in the uplifting process, when the dip angle of structure plane is changed or the spacing of structure plane is changed. Some disciplines are summarized, which structure plane have effect on mechanical properties of rock mass, that's mechanical influence of structure plane. The final displacement actually appears level change, when dip angle of rock mass changes. The greater the spacing is, the greater the ultimate displacement is, and being a stable value. Accordingly, it offers a useful reference to bearing capacity of anchor uplifted, the premise for the stable of rock mass.