科创中国

The generation and evolution of zonal disintegration are analyzed by means of numerical simulation. Based on maximum tensile stress criterion and strain energy density theory, the element failure criteria have been developed in terms of mesoscopic level. Then the elastic damage mechanics is considered to simulate the failure behavior of rock. In the specific numerical modeling process, the released energy caused by the excavation of underground workings must be large enough to bring about dynamic phenomenon of the surrounding rock. In other words, the excavation process can be considered as dynamic process. Based on the above concepts, the zonal disintegration code has been developed by the FISH of FLAC^3D. Then it was used to determine the failure pattern of the rock mass around the deep roadways and the quantity and width of the zonal disintegration also have been obtained. The results of numerical simulation are in good agreement with the in-situ monitoring results.

Li Shuchen;Feng Xianda;Li Shucai;Yuan Chao;Li Wenting;Sun Qian

Yanshilixue Yu Gongcheng Xuebao Chinese Journal of Rock Mechanics and Engineering

2011

The theory of thermal diffusion in surrounding rocks affected by mining around the water-bearing structure is studied. The new style advanced model test device and similar material of typical hydro-mechanical coupling is used and the monitoring system of grating temperature and displacement is improved. The coal mining around the water-bearing structure is simulated by tests. The variation laws of seepage and temperature fields induced by deformation of overburden rock during mining are analyzed. There is obvious abnormal temperature feature in the intact rock mass around the water-hearing structure before mining. The temperature of rock mass reduces gradually with the mining. Temperature response feature of water inrush is obvious in layered rock mass upper the gob. The temperature fitting curve of rock mass is concluded with the data of the model test. It provides the theoretical foundation for the forecasting water with rock mass temperature method.

Zhang Qingsong;Gao Yang;Li Shucai;Li Liping;Yuan Xiaoshuai;Zhao Jiangang;Li Zhipeng

Yanshilixue Yu Gongcheng Xuebao Chinese Journal of Rock Mechanics and Engineering

2011

According to the characteristics of old in-use tunnels of Shenyang-Dandong railway, an investigation on defects like water leaking has been carried out by sketch of tunnel damage and ground penetrating radar (GPR) scanning. The features of defects such as tunnel lining cracking, surface corrosion, water infiltration, freeze-thaw, lining vacuousness, collapse and rockfall of the entrance, etc. are studied and analyzed carefully. The degradation mechanism of tunnels is briefly analyzed from the physical factors and chemical factors. Based on the above, combining the relevant data and operating characteristics of the railway tunnel in cold regions, the flow chart of tunnel maintenance and the main repair methods are given. And these methods are carried out in the Fenshuiling tunnel maintenance works at last. The paper provides theoretical basis for integrated maintenance of tunnels and contributes to the guidance for engineering practice.

Yuan Chao;Li Shuchen;Li Shucai;Li Wenting

Yanshilixue Yu Gongcheng Xuebao Chinese Journal of Rock Mechanics and Engineering

2011

According to the characteristics of old in-use tunnels managed by Shenyang Railway Bureau, a investigation on defects like water leaking has been carried out by video recording, unfolded drawing and Ground Penetrating Radar (GPR) scanning. The features of defects such as tunnel lining cracking, surface corrosion, freeze-thaw, water infiltration, etc. are studied carefully. Based on the above, this paper summarizes the detecting methods for water leaking, voids, debonding, delaminations and moisture, and then analyses the defects features, which lays a theoretical foundation for tunnel defects testing and treatment. The conclusion also provides guidance for engineering practice and integrated maintenance of tunnels. © 2011 ASCE.

Yuan Chao;Li Shuchen;Li Shucai

Geotechnical Special Publication

2011

Based on the construction of Changchengling double-arch tunnel with heavily jointed soft rock mass, a model test was carried out to analyze the stress characteristics during the excavation. With the help of monitoring instruments, the datas of stress, strain and pressure were collected and analyzed. Then a numberical simulation was carried out with FLAC3D, and its results verify the conclusions of model test. Combining with numerical analysis, the results of the model test reveals the variation laws of the tunnel surrounding rock stress and the change trends of pressure above and below the middle wall.

Li Shu-Chen;Yuan Chao;Li Shu-Cai;Li Xin-Zhi;Feng Xian-Da;Li Wen-Ting

Meitan Xuebao Journal of the China Coal Society

2012

A new numerical simulation method for water flow in a porous medium is proposed. A porous medium is discretized graph-theoretically into a discrete pipe network. Each pipe in the oriented network is defined as a weighted element with a starting node and an ending node. Equivalent hydraulic parameters are derived based on the Darcy's Law. A node law of flow rate and a pipe law of pressure are derived based on the conservation of mass and energy, as well as the graph-theoretic network theory. A unified governing equation for both the inner pipes and the boundary pipes are deduced. A conversion law of flow rate/velocity is proposed and discussed. A few case studies are analyzed and compared with those from analytical solutions and finite element analysis. It shows that the proposed Graph-theoretic Pipe Network Method (GPNM) is effective in analyzing water flow in a porous medium. The advantage of the proposed GPNM is that a continuous porous medium is discretized into a discrete pipe network, which is analyzed same as for a discrete fracture network. Solutions of water pressures and flow rates in the discrete pipe network are obtained by solving a system of nonhomogeneous linear equations. It is demonstrated with high efficiency and accuracy. The developed method can be extended to analyzing water flow in fractured and porous media in 3-D conditions. © 2013 Elsevier Inc.

Xu Z. H.;Li S. C.;Ma G. W.

International Journal of Heat and Fluid Flow

2014

In order to simulate water flow in discrete fracture networks, a Graph-theoretic Pipe Network Method (GPNM) is proposed. Firstly, identification of water flow pathways is considered and a tree cutting technique is adopted. Then each fracture in a discrete fracture network is treated as a weighted pipe with a starting node and an ending node in an oriented graph. A node law of flow rate and a pipe law of pressure in discrete fracture networks are derived based on the conservation of mass and energy, respectively. Boundaries and fractures are unified with the same form of a unified governing equation. Solutions of water pressures and flow rates in discrete fracture networks are obtained by solving a system of nonhomogeneous linear equations. Since no discretization is needed, GPNM is demonstrated with high efficiency. In addition, a few case studies are implemented and compared with those from analytical solutions or numerical analysis using the software, Universal Distinct Element Code (UDEC). It shows that the proposed Graph-theoretic Pipe Network Method (GPNM) is effective in analyzing water flow in discrete fracture networks. Moreover, GPNM is promising for more engineering applications, and can be used for large scales of water simulation problems with numerous fractures. © 2014 Elsevier Ltd.

Li S. C.;Xu Z. H.;Ma G. W.

Tunnelling and Underground Space Technology

2014

Discrete fracture network has significant effects on the thermal-hydraulic-mechanical-chemical coupling analysis in a highly fractured medium. Due to the complex configuration of interior fracture network, generation of a high resolving mesh is crucial in achieving accurate numerical results. An adaptive mesh refinement method is developed for generating adaptive meshes in a domain with discrete fracture networks. An optimized size function is embedded into Persson's mesh generator. The constrained Delaunay triangulation algorithm is integrated into the analogous force equilibrium method. An assessment method of mesh size quality is proposed. Fractures are pre-meshed with a user-specified length in advance. The whole domain is then adaptively meshed using a constrained Delaunay method in a locally relaxation manner. Varying meshes can be generated with fine meshes around fractures and coarse meshes in the domain. Two case studies are carried out and compared with those obtained from conventional methods. Results show that the present method is advantageous in generating a high resolving mesh. Finer meshes are adaptively generated around fractures and gradually changed to sparser meshes away from fractures. Smoothly and gradually varying meshes are generated with little sacrifice of the size and angle quality. The adaptive mesh refinement method can be used for a wide range of thermal, hydraulic, mechanical, chemical simulations and their numerical coupling system in a fractured medium. © 2014 Elsevier B.V.

Li S. C.;Xu Z. H.;Yang W. M.;Ma G. W.

Finite Elements in Analysis and Design

2014

The process of thermal diffusion in rock masses influenced by excavation around the water-bearing structure was investigated. Similarity material for typical H-M (hydro-mechanical) coupling experiments was perfected and the monitoring system of fiber brag grating (FBG) temperature sensors and FBG seepage pressure sensors were improved and used in this experiment. The roadway excavation around the water-bearing structure was simulated. The variation of the seepage field and temperature field caused by the rock deformation and change of seepage boundary conditions were analyzed. The rock mass adjacent to the water-bearing structure has low-temperature comparing with the far-field rock mass. During the excavation, the seepage pressure around the water-bearing structure decreases and the thermal convection increases. As a result, the temperature of rock mass reduces gradually with small changes in the scope affected by the water with the excavation. A new method for the forecast of water inrush is proposed by analyzing the Peclet value. The temperature fitting curve of rock mass is concluded in the end. It provides the theoretical foundation for the forecasting water with rock mass temperature.

Gao Yang;Zhang Qingsong;Li Shucai;Jiang Yujing

Zhongnan Daxue Xuebao Ziran Kexue Ban Journal of Central South University Science and Technology

2014

DDARF (Discontinuous Deformation Analysis for Rock Failure) is an improved method of DDA (Discontinuous Deformation Analysis method), while there are only uniform grids in the original DDARF, and multi-scale grid meshing method cannot be realized. A multi-scale grid meshing method for DDARF is proposed to rock failure analysis, which balances off between the calculation accuracy and computation time. Simulations with multi-scale grid model and uniform grid model are established respectively, and compared with the laboratory tests; this multi-scale grid meshing method is applied to progressive failure process for jointed surrounding rock, and influence on crack propagation by the different lateral pressure coefficients K0 of in situ stress is analyzed. It is concluded that this multi-scale grid meshing method for DDARF is feasible and the calculation accuracy can be improved with the same grid number. The proposed method is able to increase the computation efficiency by reducing the computation time when simulating underground cavern excavations, at the same time maintain the calculation accuracy. With increase of the lateral pressure coefficient K0 of in situ stress, the main cracks propagating zones are moved gradually from both sidewalls of the cavern to the arch crown and floor. This method improves the DDARF to large projects, and it can analyze the progressive failure process of rock more effectively. © 2014 Elsevier Ltd.

Zhu Wei-shen;Chen Yun-juan;Li Shu-cai;Yu Song;Li Yong;Yin Fu-qiang

Tunnelling and Underground Space Technology

2014