Thrust On Retaining Walls With Narrow Backfill Based On Unified Strength Theory And Optimization Design Of Retaining Wall

With the development of the city, the land resource is cutting down,There appears that the proposed retaining wall to buildings is very close to the basement wall of existing buildings. Retaining wall which is built in mountainous areas is often formed by narrow filling because it is close to the rock slope.Obviously, it is inappropriate to calculate earth pressure with Coulomb’s earth pressure theory or Rankine’s earth pressure theory in the case of narrow filling. Therefore, it is urgent to calculate finite earth pressure beside retaining wall and study the optimization design of retaining walls. At the same time, it has a broad prospect.This text discusses the earth pressure and the optimization design of retaining walls deeply. The follows are the main contents:Firstly, Assuming the slip surfaces of backfill beside retaining wall are of multiple wedges. This chapter bases on limit equilibrium theory.Considering the narrow backfill, tilt and rough wall covering.as well as the effects of overloading and the earthquake. On the basis of these conditions.This text calculates active earth pressure of sand soil.As the filling wall width decreases, the failure mechanism change from single wedge to double wedges, and transform to three wedges, it makes calculation more flexible.The results show that with the decrease of the backfill width, earth pressure reduces.It is less than coulomb’s value.When friction angle between soil and wall is big, the results are equal to coulomb’s theory.This is due to the increasing of the top surface width with the increasing of friction angle.It makes the failure mechanism tend to be more close to coulomb’s theory.Secondly, Assuming that the sliding surfaces of backfii beside retaining wall is double slider plane.It is based on the Morh-Coulomb strength theory.and the limit analysis theory.We calculate active earth pressure of sandy soil. The results show the method gets the distribution of earth pressure is nonlinear. The earth pressure intensity increases with depth. While its growth decreases gradually at the bottom of the wall.Thirdly, Assuming that the sliding surfaces of backfii beside retaining wall is combination of logarithmic spiral surface and plane through the heel of wall.It is based on unified strength theory and the limit analysis theory. When the material shear stress coefficient B=2, the unified strength theory comes to Morh-Coulomb strength theory.The results show that the coefficient of earth pressure is greater than the method which is based on the limit equilibrium theory.This is because the results which is based on the limit analysis theory is the top solution of earth pressure.At the same time, the resultant force of earth pressure point is changing all the time.It is not always in the point of 1/3 wall height.Finally, The objective function is area of gravity retaining wall.The constraint condition is the anti-sliding stability, resistance to overturn stability, stress of the basement and structure requirements.The text uses some parameters to build optimization mathematical model of gravity retaining wall.Through the MATLAB optimization of genetic algorithm,We can get intelligent optimization design of the narrow backfill beside gravity retaining wall.To apply this method to the retaining walls in a power plant in Guizhou province. The analysis find that the optimization design saves area of 38% in the condition of satisfy the sliding resistance and resistance to overturn.It is good for the finance.