| Goaf collapse, landslides are typical geological disasters, the loss due to them is very great, therefore, the goaf collapse, landslide issues are important subjects of research in the field of geotechnical engineering. In Yangshan mine area of Suzhou, the ground collapse and ground fissures had occurred, and leaded to landslides. A proposed tunnel project will across the Yangshan, these goaf, ground collapse, ground fissures, landslides and other geological disasters will have an impact on the tunnel project.the construction conditions of Yangshan tunnel project are very complex. As the background to this project, the influence of goaf, landslides, ground fissures, ground collapse and other factors on the tunnel project was studied, the tunnel and the nearby mountain slope stability was evaluated in this paperr. Obviously, this study plays an important role in guiding the engineering design and construction of the proposed tunnel. The premise of stability evaluation for the tunnel and slope is finding a correct way to obtain physical and mechanical parameters of rock mass. The currently used methods is the field test method and empirical estimation method, the operation of field test is complex, time-consuming, but also the field trials data can not avoid the size effect, the selection of mechanical parameters is not necessarily accurate. The empirical estimation method depends mainly on rock mass quality evaluation system does not take into account large-scale trials, but it must identify the rock mass structure type, control surface of the rock mass and need a certain number of rock strength parameters, such as rock uniaxial compressive strength, shear strength.The analysis of preferred plane and rock strength test methods is the basis of engineering stability evaluation, therefore, according to the analysis of preferred plane and field engineering geology survey, rock strength test method was researched mainly. A kind of rock strength tester was self-developed, the tester can be a convenient method for testing rock uniaxial compressive strength, tensile strength and cohesion. Then combine the analysis of preferred plane and the system of rock mass quality evaluation to estimate the physical and mechanical parameters. Finally, the stability of goaf collapse, landslide, and tunnel was calculated and analyzed. To sum up, the main results of this paper can be summarized as follows:(1) The investigation of engineering geology and preferred plane analysis for Yangshan tunnel project show that the engineering field was controlled by compressive fracture, and produced extremely broken rock mass. The important influence factors of tunnel project are fault broken zone, dykes, landslides and ground collapse. The preferred plane controlling the stability of tunnel and slope are fault broken zone, dike zone and the NE structure surface. The quality evaluation of Yangshan rock mass shows that the relation of BQ and Q, RMR and Q is logarithmic, BQ and RMR showed a linear relationship. The physical and mechanical parameters of rock mass were calculated by Hoek-Brown method, and these parameters can be used for the numerical calculation. The impact analysis of the shear strength of jointed rock mass by structure surface showes that, the normal stress is greater and the impact of strength ratio by joints connectivity rate is smaller. The impact of strength ratio by normal stress decreases with the increase of joints connectivity rate.(2) The existing rock strength testing methods was analyzed and summarized, the self-developed rock strength tester can be used to test uniaxial compressive strength, tensile strength, and cohesion, the total weight is about30Kg, it is facilitate to the field testing. The indoor and outdoor rock uniaxial compressive strength, point load strength, rebound strength tests were also tested in this paper, and regression analysis was used to establish the mathematical relationship of the three strength. Proving Ring method was invented to test the basic friction angle of rock, and the average error is only4.38%when contrast with the slide method.(3) According to the field geological survey and engineering geology analysis, Qingshan mine area had finished mining, and it is far from the mountain, ground collapse had completed, the possibility of catastrophic collapse and landslide is lower. Yangxi mine area has a larger goaf area and shallow depth, there are already multiple collapse pits, and caused landslide in the west side of the mountain, while the mine area is still mining, it’s a serious threat to the stability of the mountain. Therefore, the Yangxi mine area should improve great importance to monitor for landslide,take drilling and geophysical to determine the sliding surface further. The numerical results show that Yangxi mining area, the goaf1#,2#,3#and4#formed a few meters of settlement, the rock mass above goaf has been completely passed through by shear strain, indicating that the slope had slidied, which is consistent with the actual situation.(4) Under goaf condition, the influence of landslide to tunnel is mainly reflecting on amplification for horizontal displacement, generally increased about10%. Therefore, when tunnelling to the west side of the mountain, the slope and tunnel should be intensified monitoring. In the numerical model, the cross-section of X=1020m, landslide has a small impact on the tunnel, when the cross-section move to west side, the impact of landslide was significantly increased, therefore, when tunneling to X=1020m, and the west should improve great importance, and fault fracture zone and dykes zone also needs adequate attention. |
PDF Full Text Request