Study On Dynamic Analysis And Seismic Design Of Slope Protected By Soil Nailing Retaining Wall Under Earthquake

There are a number of mountains and valleys in the west of China, therefore flat lands are extended to provide platforms for buildings, roads and other infrastructures when these facilities are constructed in this region. This frequently requires cutting of slopes and filling of valleys. In order to ensure that these facilities work in the right way it is essential for us to adopt retaining wall to prevent landslides and debris flow from occurring. Our country is an earthquake region and the geological condition is complicated. Thus, a lot of the highways and railways will pass through the region of high earthquake intensity. So, it is necessary to study the characteristics of the slope protected by soil nailing under the earthquake. Moreover, the slope protected by soil nailing is different to the pure soil slope. Not only the interaction and work together of surrounding soil and soil nailing but also the interaction of the soil and the facing are considered in the systems. So its characteristic of vibration is much more complicated than the pure soil slope. The comprehensive theoretical analysis and the numerical simulation have been carried out for the soil nailing flexible supporting structure under earthquake. The main work and conclusions gained are listed as follows:(1) A dynamic calculation model of soil nailing protected structures for the slope is proposed. The interaction between soil and soil nailing is treated with linear spring and damped system related with velocity. The influence of the facing upon soil nailing is simplified for equivalent mass. Under the condition of horizontal earthquake excitation equation of vibration response is established in according with being mentioned ahead, the analytical solutions are obtained for steady vibration. The method is applied to a case record for illustration of its capability, in order to verify the method 3-D nonlinear FEM (ADINA) is used to analyze the seismic performance of this case, the comparative results show that the design and the analysis are safe and credible using the proposal method. The calculation model provides a new approach for earthquake analysis and antiseismic design of slope protected by soil nailing.(2) Corresponding to design method of tall-building seismic design, the request of three levels seismic design and the design way of two stages are proposed for the slope protected by soil nailing. Considering seismic excitation property, soil property and slope height, occurring shear displacement under horizontal excitation, a simplified dynamic calculation model of soil nailing protected structures for the slope is proposed. Based upon the hypothesis which the lateral displacement of the stability soil and instability soil is nearly in phase and the lateral interaction between them is ignored under horizontal excitation, the instability soil and facing is treated as study object. Because the facing is flexible, its lateral displacement depends on the lateral displacement of instability soil. The soil nailing is served as the elastic supports. Under the condition of horizontal earthquake excitation equation of vibration response is established in according with being mentioned ahead, the analytical solutions are obtained for simple harmonic vibration. The soil nailing axial force response near failure surface, elastic lateral displacement time history and vertical seismic response distribution can be obtained by this method. The method and 3-D nonlinear FEM (ADINA) are applied to a case record for illustration of its capability, the comparison of results, using the proposed approach and FEM shows good agreement. This method can be used the first stage seismic design and analysis for the slope protected by soil nailing.(3) Under the situation of considering the soil nailing effects on stability of soil side-slope, according to the damage model of the slip surface, the limit equilibrium theory and pseudo static approach, the seismic stability model is set up. Errors should be induced in calculating horizontal seismic inertial force and anti-sliding moment according to vertical slice. The seismic stability analysis method of slope protected by soil sailing is improved by using horizontal and vertical slice method. A dynamical search model is set up for the critical slip surface determination of soil nailing wall, and the dynamical stability analysis of soil nailing wall is realized. By calculating, it is showed that the location of critical slip surface is varied with the design parameters of soil nailing wall. Soil nails have great effect on the slope stability. Compared with the experience methods, it is a good method for the stability analysis of soil nailing wall based on the dynamical search model of slip surface, and can overcome the irrationality without considering the effect of soil nails. Calculation of the stability of slip surface is carried out by using the genetic algorithms. It can avoid getting in local minimum in optimal design. Finally, using object-oriented programming language VC++, a computing program is implemented to make the optimization course reality.(4) Based on the analysis model of seismic stability, the permanent displacement calculation model of slope protected by soil nailing is established under earthquake. The total permanent displacement consisted of two parts of the earthquake displacement and the post-earthquake displacement is proposed. The solution of average acceleration adopts the elastic dynamic calculating model of Chapter 3 to improve the rigidity assumptions of Newmark method. Using genetic algorithms to search yield acceleration can achieve the permanent displacement of slope under earthquake. Using principle of works and energy, the calculating model of post-earthquake permanent displacement is established and solved. According to soil nailing characteristic which is flexible, after the earthquake the "folding steps" slip deformation mechanism is proposed to calculate the sliding friction works of soil nailing. The dynamic design philosophy and procedural steps of the soil nailing structure are given based on the control of the permanent displacement of the slope. The analysis results show that the ratio of post-earthquake displacement and seismic displacement is great, post-earthquake displacement can not be ignored.(5) Combined with the reality highway slope protected by soil nailing project, nonlinear FEM (ADINA) is used to analyze the seismic performance of slope protected by soil nailing retaining wall. On the base of works together and interaction between loess and flexible retaining wall, 3-D nonlinear FEM model is formed. A model that is capable of simulating the nonlinear static and dynamic elastic-plastic behavior of soil is used to model the soil, and a bilinear elastic-plastic model that has hardening behavior is used to model the soil nailing. Friction-element is employed to describe the soil-structure interaction behavior. By calculating, comparing and parametric analysis, some useful conclusions is drawn, these conclusions can be for reference in constructing some similar engineering and the design.