The Calculation Method And Numerical Simulation Of Earth Pressure For Limited Soil Between Existing Basement And Foundation Pit

With the rapid development of high and super-high building,building density increasing,in practical design of deep foundation pit,distance between excavated foundation pit and existing building basement is relatively close.So as to excavation pit supporting structure and existing building basement formed finite width of soil and this part of soil generally can not be excavated.at this time,the earth pressure acting on the retaining structure belongs to limited soil pressure,while classical earth pressure theory is based on the semi infinite assumption,which is not suitable for limited soil.In this paper,theoretical analysis and numerical simulation are carried out for the calculation of active earth pressure of foundation pit in basement of existing building.The main work and conclusions are as follows:1.Based on principle of limit equilibrium theory,established a method for calculating the active earth pressure of finite soil considering influence of reaction force of existing basement wall.Preliminary analysis of relationship between the coefficient of active earth pressure and soil parameters.When the friction coefficient of soil parameters is constant coefficient of active earth pressure increases with the increase of soil aspect ratio.When increases to a certain value gradually tend to be stable and active earth pressure coefficient is decreases with the increase of angle of internal friction.When the cohesion of soil parameters is constant active earth pressure coefficient decreases with the increase of aspect ratio of limited soil and active earth pressure coefficient is decreases with the increase of cohesion.In addition,the friction angle between two sides of soil interface has some influence on active earth pressure coefficient.2.By using method of numerical simulation study distribution of finite earth pressure behind wall.According to results of numerical simulation,it is found that lateral wall of existing building always acts on the side pressure of soil in process of earth pressure from static earth pressure to active earth pressure.The earth pressure distribution between static soil pressure curve and Rankine active earth pressure,when soil behind wall reaches limit state,the wall soil pressure reaches minimum value and nonlinear distribution of drum type.The distribution curve is close to the calculated results of active soil pressure of limited soil considering influence of reaction force of existing basement wall.It is verified that the correctness and validity of the method.3.Numerical simulation method is used to analyze variation law of soil pressure of retaining structure during excavation.With excavation of soil,soil at bottom of foundation pit is unloaded and earth pressure of supporting structure is gradually changed from a linear distribution to a non-linear distribution.By comparing with the results of theoretical calculation,it can be seen that numerical simulation results are close to the results of active earth pressure considering influence of wall reaction of basement,while the classical Rankine's active results significantly larger.Therefore,it is feasible to calculate the earth pressure on the side of foundation pit supporting structure of existing building basement by using the calculation method of active earth pressure considering the reaction force of basement wall.