Research Of Active Earth Pressure On Calculation Retaining Wall

The active earth pressure of calculation method for retaining wall is a classics issue in the field of soil mechanics. So far, the calculation of active earth pressure is still exist many problems. Such as, the active earth pressure calculation results can’t consider the influence of the retaining wall displacement mode on calculation results. At the same time, We need to assume that shape of the critical slip surface. Furthermore, the simple calculation model cause the problem such as fitness for use is limited. In view of the above problems, this paper using the method of limit equilibrium of variational problem of active earth pressure and using oblique slice method to calculate the distribution of active earth pressure,we can get the following conclusions.(1) according to the different properties of cohesive soil and cohesiveless soil,we calculated them in different methods.from the wall sliding wedge overall equilibrium equtation we can obtain active earth pressure model of isoperimetric functional extremum for slope is deduced for the upper slope,a uniform surcharge,wall back tilt and rough. Through solving the extremum isopermetric problem of active earth pressure, we get the cohesive soil and cohesive soil slip crack surface function who is logarithmic spiral and slip crack surface normal stress function, the solution of active earth pressure can be converted to optimization problem about two Lagrange multiplier, we obtain critical slip surface location and the active earth pressure through searching.(2) By an example analysis which shows that the calculation of cohesive soil cracking depth z0 can be get the accurate results of crack depth by searching, stress of the critical slip surface endpoint can be used to termination conditions for the search program.(3) Combined with the example to analysis, the results show that there are upper and lower limit point location of the coefficient for the cohesive soil and cohesive soil, only within the scope, the retaining wall can reach the limit equilibrium state; With the increase of force location, the active earth pressure increase nonlinear. Compared with the theory of coulomb showed that the minimum active earth pressure is very close to the results of coulomb theory. but the force position coefficient is higher than the coulomb theory. who assumes that force position coefficient is 1/3, the calculation results also illustrate the safety coefficient of the results is larger than the coulomb theory is adopted to compute overturning resistant stability.(4) assumed normal stress and shear stress is uniform, we use the thin-layer element method to calculate the active earth pressure distribution. for a given force location point, each active earth pressure of the thin-layer element can be obtained based on the condition of static equilibrium, we can get the active earth pressure distribution for retaining wall. Then compared model test with the active earth pressure distribution for cohesive soil and cohesive soil to validate and verify the applicability of the calculation results, the comparison results show that the trend of the calculation result and model test for active earth pressure distribution is roughly consistent, which can reflect the actual distribution of active earth pressure. as a result, we can say that the thin-layer element method is a feasible way to calculate active earth pressure distribution.(5) this paper use the calculation method for an engineering project to select an optimal retaining wall form, which include downward oblique retaining wall, reclining on the slight slope retaining wall, balance weight retaining wall three kinds of types. the results suggest that balance weight retaining wall has a good safety and economics. In a word, the calculation method in the paper can be a reference for the design of retaining wall.In a word, based on the variational method of limit equilibrium of active earth pressure calculation method can effectively estimate the active earth pressure of retaining structure and the force location, which contains the retaining wall movements of all the possible cases of active earth pressure and the point position; using the oblique slice method with soil stress under the uniform assumptions on the active earth pressure under limit state can be obtained more accurate distribution the calculation method in the paper can be a reference for the design of retaining wall.