西南交通大学研究生2015-2016学年 第(1)学期期末考试试卷 课程名称 研究生学术英语读写译 课程代码 51321001 考试形式 课程论文院 系 学 号 姓 名 密封装订线 密封装订线 密封装订线KEY WORDS: circular tunnel; stress state; analytical method; numerical method1 INTRODUCTIONAccording to Li (2004), the definition of tunnel was officially proposed by Organization for Economic Co-operation and Development (OECD) at a tunnel conference in 1970, at which tunnel was defined as ‘A underground cavity, whose cross -sectional area is larger than 2, that is constructed by an arbitrary method in accordance with the prescribed shape and scale’. The tunne l can be differently sorted out in terms of its function, depth, location, sectional area, length and geological condition separately (Tan, 2001). However, this research focuses on the traffic tunnel, including hig hway tunnel and railway tunnel…The software ANSYS and FLAC3D are used in the numerical methods and t he shape of tunnel is circular…2 ANALYTICAL METHODThis chapter will explore the stress and displacement in wall rock at every step on the basis of elastic and plastic mechanics. Specific expressions of them will be given.2.1 Initial stress stateGenerally speaking, the initial stress is mainly constituted by gravity stress and tectonic stress. It is also related to the tectonic geometry, depth, and history of tectonic movement. According to Guan (1993), the initial stress can be calculated by:=Z T σσσ+ (1)where is the gravity stress; is the tectonic stress (Guo, Ma, & Xue, 1983).The tectonic stress is so complicated that…This paper ignores tectonic stress, in other words, the initial stress is equal to gravity stress.When the ground is horizontal and the rock mass is an isotropic semi-infinite body...The test indicates the Poisson's ratio of most rocks ranges from 0.15 to 0.35, so the horizontal gravity stresses are less than the vertical ones.2.2 Secondary stress stateThe factors that can affect the secondar y stress state are complicated…The practicable strategy is to take the main factors into consideration.The state in wall rock can be totally elastic or partly plastic. For the former, the stress in wall rock … For the latter, the stress in surrounding wall rock… is less than the strength.To simplify the problem, some assumptions are made as follows:1) The wall rock can be regarded as a homogeneous isotropic continuum;2) The initial stress is equal to gravity stress, if ignoring the tectonic stress;3) The shape of tunnel is circuit and it is a deep-buried tunnel;4) The plane strain conditions are satisfied.2.3 Totally elasticThe principle of elastic mechanics shows that the secondary stress field in wall rock can employ the following model (in which the gravity is ignored and whose scale is 2 to 3 times larger than the tunnel diameter) shown in Figure 1, when the depth is 10 times bigger than the tunnel diameter.Figure 1. The analysis model of stress in wall rock In Figure 1, 、 are both the gravity stress in the center of tunnel. They are calculated by: z c H σγ= (4) z x σλσ= (5) where is the depth of the center of tunnel …the solution of stress and relative tunnel; E is the elastic modulus; is the Poisson’s ratio…3 NUMERICAL METHODThe software ANSYS10.0 is used to simulate the factors which can affect the initial stress state. FLAC3D is used to get the stress and displacement of secondary stress state and third stress state. Then comparison between the numerical solution and the analytical one is made.3.1 Initial Stress StateAccording to Guan (1993), the initial stress state is related to the following factors: depth, tectonic movement (fault and fold), the surrounding terrain, and so on.3.1.1 DepthThe scale of the model is . The parameters of the rock are .the radius of plasticity zone is smaller than the one of secondary stress state …4 CONCLUSIONThe stress and displacement in wall rock during tunnel construction are analyzed through analytical method and numerical method in this paper. The elastic-plastic mechanics theory, the ANSYS and FLAC3D software are used to generate the solutions.ANSYS is a kind of suitable software to simulate the tectonic fold and fault, which is in line with the mechanical principle.FLAC3D can well model the wall rock in terms of its stress and displacement fields. When radial distance is smaller than 5 to 6 times of the tunnel radius … The impact of lateral pressure coefficient has not been studied. The software of ABAQUS can be used to solve this problem …ACKNOWLEDGEMENTSMy deepest gratitude goes first and foremost to my supervisor, for his constant encouragement and guidance. I am also greatly indebted to the professors and teachers from the School of Civil Engineering. I equally owe my sincere gratitude to my friends and my fellow classmates who gave me their help and help me work out my problems and overcome difficulties in the study i .i Several scholars have offered their explanations on…。