Theoretical Study On Earth Pressure Of Underground Structure Under The Condition Of Limited Soil

In recent years,with the rapid development of urban underground space and the increasing density of underground buildings,the soil behind the retaining structure of foundation pit often can not meet the conditions of semi-infinite soil.Compared with the semi-infinite soil,the active earth pressure of the limited width soil on the retaining structure of the foundation pit will be much smaller,while the passive earth pressure will be much larger,so it is necessary to study the active earth pressure and passive earth pressure of the limited width soil.On the basis of summarizing the previous research results,the theoretical study of the calculation of the active earth pressure and passive earth pressure of the limited clay,the limited sand considering the interlaminar shear stress and the limited sand considering the spatial effect are focused in this thesis,the main contents are as follows(1)Taking the limited range clay behind the retaining wall as the research object,considering the influence of soil arching effect and non-limit state,and based on the upper limit theory of plasticity and the hypothesis of multiple slip surfaces under the limited soil,the variation law of the angle of the fracture surfaces and the coefficient of lateral earth pressure is given,and the formula of the active earth pressure and passive earth pressure of the finite soil is derived by the thin-layer element analysis method,which can also be reduced to the formula of the active earth pressure and passive earth pressure of the semi infinite soil.Compared with the model tests in semi-infinite soil and finite soil,the theoretical solution in this thesis is in good agreement with the experimental value,which proves the rationality of the solution in this thesis.The parameter analysis also reveals the influence of the change of soil parameters on the angle of the sliding surface and the distribution of the active earth pressure and passive earth pressure.(2)Considering the influence of soil arching effect and inter-laminar shear stress in the non-limit state,based on the influence of multi-channel slip surface of finite soil on the coefficient of lateral earth pressure,the solution of active earth pressure and passive earth pressure for sandy under the limited soil is derived,which can also be reduced to the solution of active earth pressure and passive earth pressure under semi-infinite soil.Compared with the model test results of finite soil,the theoretical solution of considering the interlaminar shear stress is more consistent with the test value for passive earth pressure,but opposite for the active earth pressure.The parameter analysis shows that the active earth pressure is inversely related to the aspect ratio and the angle of internal and external friction,while the passive earth pressure is positively related to the aspect ratio and the angle of internal and external friction.(3)Taking the limited range sand behind the retaining structure as the research object,the soil space behind the retaining wall is divided into four parts by considering the soil arching effect under the non-limit condition and the influence of the assumption of multi-channel slip surface under the limited soil on the lateral earth pressure coefficient.The stress analysis is carried out by the thin-layer element analysis method,and the solution of the active earth pressure and passive earth pressure of the limited soil considering the space effect are derived.The results show that it is necessary to consider the influence of space effect on earth pressure when the length height ratio of retaining wall is small.