The Slope Seismic Stability Analysis Pseudo-static Method Improvement

In foundation engineering construction in our country at present period of great prosperity development, such as highway, railway and water conservancy project construction, all need to build the slope. Slope engineering construction of our country’s national economy has important influence incalculable. Artificial slope for infrastructure to provide powerful guarantee as well as provided more convenient production and living, however the slope stability problems are also serious influence to highway, railway and water conservancy engineering construction cost, construction safety and operation safety. Our country in the world’s two largest concentration of the earthquake zone,(the Himalayan Mediterranean seismic zone and ring Pacific seismic zone), and by the Indian plate and the Philippine sea plate and Indian plate squeeze each other, resulting in the development of the earthquake fault zone. Therefore, the slope stability analysis under seismic action is very important and necessary, and has great practical significance. Especially after our country has experienced the Wenchuan earthquake in 2008, the earthquake for the damage mountain landslide makes more and more scholars attach importance to study the stability of the slope in the seismic action. Therefore, in this paper, the slope seismic stability analysis pseudo-static method improvement did some preliminary research work.In this paper, the main contents and conclusions are as follows:①First of all, the paper puts forward the theoretical basis for slope stability analysis, and respectively in this paper, the slope stability under the action of static and earthquake under the action of analysis method. Based on analysis of slope stability under the action of static and seismic research status points out the advantages and disadvantages of quasi static analysis under seismic action, which lead to this paper research content;②Comprehensive analysis was carried out on the pseudo-static method, in view of the article in the vertical time-sharing calculation error of the horizontal seismic force and anti-sliding moment when carries on the analysis to the following conclusion: calculate the seismic inertia force, there is a lot of error and anti-sliding moment calculation results than real anti-sliding moment is low. People too much damage of horizontal seismic force on the slope, while ignoring the influence of vertical seismic force, therefore this thesis earthquake acceleration is inclined to consider. Under the condition of considering the oblique acceleration, improved quasi static method: article by vertical seismic inertial force and soil slip torque caused by gravity and sliding resistance moment, adopting vertical article points calculation; By horizontal seismic inertia force caused by sliding moment and sliding resistance moment, use level article points calculation; And then to overlay;③Using the finite element analysis and the rationality of the relationship between stress and strain of soil, using strength subtraction to quasi static strength subtraction analysis stability of the slope. Using the improved quasi static method with strength subtraction to analyze the same example, compare the calculated results found strength subtraction small safety factor. Through analysis on the model of strength subtraction seismic inertia force in the horizontal seismic force and the vertical earthquake force is for the entire model, and in improved quasi static method does not consider the most dangerous arc at the bottom of the sliding surface of toxoplasm seismic force, article simply analyzes the arc sliding surface above article points soil by horizontal seismic force, vertical seismic force and gravity. This means that improved quasi static method still need to improve;④Based on improved quasi static method compared with strength subtraction found problems, put forward a new calculation method, namely through the rotation of the coordinates of the original seismic force and gravity are vector synthesis, mix, set up in the direction of the force on a new X coordinates, perpendicular to the force of seismic slope stability problem into after the soil parameters and slope geometry correction form new slope, only new slope static analysis can be. To verify the feasibility of the new method, using the improved quasi static method and strength subtraction for the same example to calculate. The results were compared with the previous two safety coefficient. Found that conclusions and the strength subtraction method of rotating coordinate conclusion close, scales are small, shows that the rotating coordinate method is adopted to avoid improved quasi static method does not consider the most dangerous arc sliding surface lower seismic force, the analysis method is feasible, and have no effect on the pseudo-static analysis method itself;⑤In order to improve the practicability of rotating coordinates, consider the underwater slope under the action of earthquake safety coefficient calculation, using the rotating coordinate method, the static calculation method compared with traditional methods, such as theoretical derivation formula, analysis the accuracy of the result. Found by comparing the numerical analysis method and theory analysis method the conclusion were similar, indicating that under the rotating coordinate method of underwater slope seepage can be used for analysis of water level slope under seismic action;⑥To the practical slope as an example, the use of transfer coefficient method for calculating the slope stability under the general conditions and improved quasi static method and rotating coordinate method is used to check the stability of slope under seismic loading. Results show that the rotating coordinate method to get the stability coefficient of smaller than improved quasi static method, calculation more scientific.