Transform Coefficient Of Soil Layer Strain To Underground Structure During Earthquakes

Recently, underground structures such as underground squares and shield tunneling with complicated and large-scale cross-sections, increase so fast that the seismic design for the cross-sections becomes more and more significant. However, proper methodologies of lateral seismic design for underground structures are not well-fledged. Based on this idea, the following points are discussed in this thesis:1. The necessity of seismic design for soil-underground structure interaction is stated first. The seismic risk cases of soil-underground interaction are summarized and some of the influencing aspects are analyzed. Some comments on the existing analytical methodologies of soil-underground structure interaction and their disadvantages are given. Finally some computer software for the soil-underground structure interaction dynamic analysis is introduced.2. The advantages and disadvantages of the underground structure seismic design methods are analyzed and the deformation methodology as the key for the underground structural seismic design is designated. Also the lateral-strain-transform numerical model which is employed in underground structure dynamic analysis is proposed and the crucial points to be solved in the model is illuminated, seeing the formulae and computations respectively. And the estimate for the influence aspects is provided. Furthermore, the strain transform coefficient (STC) is defined.3. The two-dimensional nonlinear dynamic FEM program suitable for the larger deformation of clay, namely home-code SD4, for the seismic design of underground structures is improved. At the same time, ANSYS to link up SD4 on pre-processing and post-processing in order to simulate the lateral-strain-transform numerical model which the author proposed before is redeveloped, as well as the feasibility and reliability of this model is verified.4. On the basic of lateral-strain-transform numerical model, the effects of variation of the parameters including the input earthquake motion, the soil property and soil layer as well as the feature of the underground structure on the STC and the structure dynamic response are investigated by the improved SD4 program.5. A simplified-method which is applicable to the seismic design of rectangle underground structures is proposed. And the formula of this method is given as well as its feasibility and precision is demonstrated.