Deformation Characteristics Analysis Of Yuejia Mansion Foundation Pit In Consideration Soil Unloading Mechanical Properties

In the context of China's growing economic scale,the modernization process continues to grow.With the development of underground space,a large number of technical problems in foundation pit engineering have emerged.The impact of the stress path on the soil is one of them.Especially in the foundation pit engineering,different excavation and support methods correspond to different stress paths.However,the stress path test form of the foundation pit engineering to obtain soil parameters is not uniform.In this paper,the support method of concrete foundation pit engineering is extracted,and the change law of stress state of soil is obtained by simulating foundation pit excavation.Three kinds of unloading test schemes are proposed.In the lateral unloading,axial loading,invariance and unloading are considered respectively.Three unloading test schemes were compared with conventional triaxial tests,and the following conclusions were obtained:the internal friction angle obtained by the unloading test and the conventional triaxial test is not much different,but the cohesion is reduced.In the unloading test,the cohesive force measured by the unloading test considering axial unloading is the smallest;the soil exhibits strong shear strength and deformability in the conventional triaxial test,and in the unloading test,the soil Under a small principal stress difference,the failure condition is reached.With the increase of the consolidation confinement force of the soil,the shear strength of the soil increases,and the deformation capacity decreases with the increase of the consolidation confining pressure.The current constitutive model is analyzed to reflect the characteristics of the soil.Combined with the results of the triaxial test,it is considered that the HS model is more suitable for the characteristics of the soil in the foundation pit process.The parameter meaning of the constitutive model is introduced.And the two test methods are unloaded,and the three E₅₀^ref,E_oed^ref and E_ur^ref stiffness parameters required for the model are analyzed.The numerical analysis of the soil strength parameters obtained from the test shows that different test parameters have little effect on the deformation law of the foundation pit soil,but have a great influence on the deformation of the foundation pit soil,which considers the unloading of axial unloading.The soil parameters obtained from the test have the greatest influence on the deformation of the foundation pit,and the rationality of the numerical simulation results is compared with the monitoring data of the foundation pit.