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Wang H.,China Railway Tunnel Group Co. | Wang H.,Southwest Jiaotong University
Yantu Lixue/Rock and Soil Mechanics | Year: 2011

Combined with engineering geological conditions of bridge foundation slope, deformation and failure process on the condition of natural state and loading is simulated and analyzed by floor-friction test method based on similarity principle qualitatively. The test results indicate that the rock masses of slopes at left and right banks are in stable state under the condition of natural state; under the condition of loading rock mass in left bank is in stable state; but the scattered earth-body in right bank is unstable; so that the right bank slope is in unstable state. A measure is suggested by pre-reinforcement or changing the location of bridge pier. Source


Zhang Y.-J.,CAS Wuhan Institute of Rock and Soil Mechanics | Yang C.-S.,China Railway Tunnel Group Co.
Journal of Central South University of Technology (English Edition) | Year: 2012

The models of stress corrosion, pressure solution and free-face dissolution/precipitation were introduced. Taking a hypothetical nuclear waste repository in an unsaturated dual-porosity rock mass as the calculation objective, four cases were designed: 1) the fracture aperture is a function of stress corrosion, pressure solution and free-face dissolution/precipitation; 2) the fracture aperture changes with stress corrosion and pressure solution; 3) the fracture aperture changes with pressure solution and free-face dissolution/precipitation; 4) the fracture aperture is only a function of pressure solution, and the matrix porosity is also a function of stress in these four cases. Then, the corresponding two-dimensional FEM analyses for the coupled thermo-hydro-mechanical processes were carried out. The results show that the effects of stress corrosion are more prominent than those of pressure solution and free-face dissolution/precipitation, and the fracture aperture and relevant permeability caused by the stress corrosion are only about 1/5 and 1/1000 of the corresponding values created by the pressure solution and free-face dissolution/precipitation, respectively. Under the action of temperature field from released heat, the negative pore and fracture pressures in the computation domain rise continuously, and are inversely proportional to the sealing of fracture aperture. The vector fields of flow velocity of fracture water in the cases with and without considering stress corrosion are obviously different. The differences between the magnitudes and distributions of stresses within the rock mass are very small in all cases. © 2012 Central South University Press and Springer-Verlag Berlin Heidelberg. Source


Liu C.,Fuzhou University | Liu Z.,China Railway Tunnel Group Co.
Modern Tunnelling Technology | Year: 2014

Water inrush often occurs during tunnel construction in karst areas due to their complexity, and this frequently results in surface settlement. This paper proposes an analytical method for construction in a karst development zone in light of water inrush induced surface settlement, namely to analyze the features of the surface settlement with a settlement diagram, to determine the geological structures of the karst development zone, to study the zone's boundary with geological data related to the settlement area, and to analyze the supply relation between the water inrush and rivers according to the relationship between the settlement centre and the rivers. Additionally, using the data of surface settlement induced by water inrush at YDK24 +098 of the Xiangshan tunnel on the Longyan-Xiamen railway, this paper analyzes the geological structures of the karst development zone, the longitudinal boundary of the karst, and the supply relation between the water inrush and the rivers, thereby verifying the feasibility of the above mentioned analytical method. Source


Wu F.-Z.,China Railway Tunnel Group Co. | Fu Z.,China Railway Tunnel Stock Co.
Journal of Railway Engineering Society | Year: 2014

Research purposes: Tongzhai tunnel entrance was affected by the same high stress, and other geological factors carbonaceous slate role in the early stages to I18 steel support parameters based support, the construction of large deformation occurs, arch distortion, shotcrete off, seriously affecting construction safety and progress.This paper is finding solutions to large deformation method to provide a reference for the subsequent construction. Research conclusions: (1)In the stress deformation by the engineering test, take the anti - supporting measures, adhere to the "strong first and optimization late" principle, support in place at a time, so as to control the deformation. (2) Soft surrounding rock after excavation is timely supported, enclosing to ring as soon as possible, and timely radial grouting to effectively strengthen loose rock, improve the surrounding rock properties, reduce rock pressure effected on the supporting structure, the support and surrounding rock stress system has formed, to restrain the deformation of tunnel. (3) Reduce the times of the excavation, set the inverted arch as early as possible, control the initial support closing time strictly. (4) The control measures of deformation of tunnel carbonaceous slate can provide reference for similar engineering. Source


Zhang Y.-J.,CAS Wuhan Institute of Rock and Soil Mechanics | Yang C.-S.,China Railway Tunnel Group Co.
Yantu Lixue/Rock and Soil Mechanics | Year: 2012

On the basis of using the models of stress corrosion and pressure solution established by Yasuhara et al, the solute concentration field is introduced into the 2D FEM code of thermo-hydro-mechanical coupling analysis for dual-porosity medium developed by the authors. Aiming at a hypothetical nuclear waste repository in unsaturated rock mass from which there is a nuclide leak, two computation conditions are designed: (1) the fracture apertures are changed with the stress corrosion and pressure solution (the porosity of intact rock is also a function of stress); (2) the fracture apertures and the porosity of intact rock are constants, then the corresponding two-dimensional numerical simulation for the coupled thermo-hydro-mechano-migratory processes is carried out; and the states of temperatures, rates and magnitudes of aperture closure, pore and fracture pressures, flow velocities, nuclide concentrations and stresses in the rock mass are investigated. The results show that the aperture closure rates caused by stress corrosion are almost six orders higher than those caused by pressure solution; and the two kinds of closure rates climb up and then decline, furthermore tend towards stability; when the effects of stress corrosion and pressure solution are considered, the negative fracture pressures in near field rise very high; the fracture aperture and porosity decrease in the case 1, so the relative permeability coefficients reduce; therefore the nuclide concentrations in pore and fracture in this case are higher than those in case 2 because the effects of negative pore and fracture pressures on the stress balancing are not reckoned in; the magnitudes and distributions of stresses within the rock mass in two calculation cases are almost the same. Source

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