Study On Deformation Behavior Of Soils Considering Stress Path During Deep Excavation

At present, due to the tension of urban soil resources, the foundation pit engineering is characterized by "more, large, near and deep". The design of foundation pit engineering changes from strength control to deformation control, with the constant expansion of the scale of the foundation pit excavation, and the depth of the foundation pit, the deformation control is more and more strict. However, the surrounding environment is more and more complex, many foundation pit supporting structure is not destroyed, but due to the deformation of large or surrounding ground subsidence is too large, it is leaded to occur the phenomena of cracking and damaging in the construction of surrounding buildings, pipelines and so on. The main reason of this phenomenon is that the deformation behavior of surrounding soil is influenced by the complex stress path. So the stress path is very necessary to study the deformation behavior of soil.The main studies in this dissertation are listed as follows:1. In order to achieve the purpose of the test of the axial radial independent control and unloading, the axial load system of the fully automatic three axis stress and strain shear tester was developed and reformed. The operation, accuracy and safety of the axial radial independent control and unloading test system with multiple sets of three axis and unloading tests are carried out.2. The numerical simulation of the whole process of foundation pit excavation is carried out, the stress path variation and shear strength parameters of soil around the excavation process are obtained; The deformation law of soil around the foundation pit is obtained by simulating the stress path of the foundation pit excavation; and the conventional three axis compression test and the stress path test are carried out.3. According to the test results, the stress strain function including the incremental ratio of the stress is established. The calculation formula and the method of calculating the relevant parameters of the stress strain function are given. The stress strain function is verified by the test and the conclusion of related literature.4. The model module which considers the stress path in the embedded PLAXIS software is developed. The model of stress path has been used to simulate the deep foundation pit engineering. Comparison of the actual monitoring data and calculation data of soil horizontal displacement and surface settlement during the excavation of foundation pit:The stress path model has a good effect on the horizontal displacement of foundation pit and soil surface settlement prediction of foundation pit.