Study On The Active Earth Pressure Under Non-limit Condition And Deformation Calculation Of Foundation Pit

With the development of urban construction,buildings in the city are becoming more dense,and the surrounding environment of the foundation pit is becoming more and more complicated,so that the foundation pit support must not only meet the stability requirements,but also meet the deformation control requirements.For some foundation pits which strict deformation control is required,the deformation of the supporting structure of the foundation pit is very small,and for soil behind the pit it is difficult to reach the limit condition.In places where buildings are dense,the width of soil behind the pit often have limited.The classical earth pressure theory assumes a semi-infinite soil behind the pit and the soil reaches the limit condition,so this theory is inappropriate to this cases.In order to more accurately calculate the active earth pressure in the non-limit condition of the foundation pit,according to the characteristics of the three modes of the foundation pit,a non-limit condition active earth pressure calculation method for the semi-infinite soil body and limited soil body of the foundation pit is proposed.On this basis,considering the interaction between the deformation of the supporting structure and the soil,the deformation calculation method of the supporting structure of the foundation pit is proposed.The main work and conclusions of this paper are as follows:(1)Study the non-limiting active earth pressure of semi-infinite soil in foundation pit under three displacement modes of flat triangle,translation and compound.Based on the existing researches,a quantitative calculation formula for the parameters of shear strength is obtained.The calculation methods of the resultant force of active earth pressure,the angle of slip,the height of the resultant force operating point under three displacement modes are put forward.Combining examples and calculation case,the relationship between the active earth pressure combined force,the slip angle,the height of the combined force operating point,the earth pressure strength and the deformation is analyzed.(2)For the case of limited soil behind the foundation pit,the relationship between the limit deformation required behind the soil reaches the limit condition and the width of the limited soil is analyzed,and the calculation method of the limit soil deformation is proposed.The calculation formula of active earth pressure of foundation pit under three displacement modes of limited soil is given.Combined with examples,the calculated value compared with the test results and classical earth pressure theory.(3)Based on the non-limiting condition active earth pressure theory and earth pressure calculation formula,for the cantilever support structure which triangle displacement pattern often occurs,the calculation formula of the top deformation of the support structure is proposed with considering the interaction between the support structure and the soil.Combined with engineering examples,the similarities and differences between calculated and measured values are compared,and the applicability of the method is initially verified.