Cheng Du Area Expansive Soil Foundation Pit Supporting Design Theory And Design Method Of Cantilever Pile Research

With China western development steps forward, chengdu also has a growing economy, construction engineering to peripheral extended continuously, also appeared a lot of deep foundation engineering, expansive soil deep foundation pit stability problem is increasingly valued. Urban construction of deep foundation pit with the deformation of slope area limited, strict and complicated underground conditions, and with the increase of excavation depth, slope gradually took on a deeper steeper taxis. The expansive soil deep foundation pit supporting design design theory basically used conventional ordinary soil, led to a part of the project. So the study of expansive soil slope of deep foundation pit supporting is very important.A expansive soil deep excavation in chengdu longtan temple as the research object, the cantilever pile test section embedding dip tube, steel bar stress meter, monitoring components such as on pile, pile soil displacement and stress changes after data. On this basis, this paper first through a lot of field investigation and statistical analysis methods in chengdu area of expansive soil slope damage forms and affecting factors of the investigation and study; And then through the east suburb of chengdu longtan temple a test of expansive soil foundation pit supporting the field monitoring of slope, and to the long-term monitoring of the test data of foundation pit supporting structure deformation and stress of the cantilever pile and analysis; Then use can effectively simulate the expansive soil from microscopic particles swelled to macroeconomic expansion deformation process of PFC2 D numerical analysis software foundation model is set up by outside factors influence, rapid excavation to basal, affected by the rainfall factors, influenced by the underground pipe leaking three, to simulate the actual working condition and at the same time comparing with the field test results, verify the software for the effectiveness of the expansion deformation of expansive soil foundation pit slope characteristics, and according to the numerical analysis results of expansive soil slope expansion characteristics of load distribution; Finally using theoretical analysis method is put forward a set of suitable for chengdu expansion of cantilever pile of foundation pit supporting design theory and design method.According to the chengdu area of expansive soil slope damage forms and influence factors, factors influencing the deformation of expansive soil slope damage includes a variety of internal factors and external factors, summed up the form of expansive soil slope deformation and destruction mainly shows the characteristics of \ "three-step\"; According to the numerical analysis results of three kinds of working conditions is simulated deformation data and the results are basically in agreement with field experiment, proved the PFC2 D software to simulate the effectiveness of expansive soil slope deformation characteristics, and through the theoretical analysis and field moisture content measured results determine the foundation pit slope rainfall influence scope, considering the safety and convenience to expansive soil has been put forward under the condition of load distribution characteristics of foundation pit; Finally adopts theoretical analysis method is put forward a set of suitable for chengdu expansion of cantilever pile of foundation pit supporting design theory and design method, and the expansive soil shear strength values and cantilever pile anchorage depth Suggestions and optimization theory is presented. Finally by the water sensitivity characteristics of expansive soil for expansive soil foundation pit supporting some protection and management measures are put forward.By the following main conclusions: the destruction of the expansive soil slope is mainly due to repeated expansion of expansive soil and the intensity attenuation caused by water sensitivity features such as; In the expansive soil foundation pit supporting, if design of expansive soil with ordinary soil, the stability under rainfall condition cannot meet the requirements; By PFC software simulation and compared with the actual situation shows that PFC software to simulate the deformation of expansive soil foundation pit is effective; By using numerical simulation software for simulating foundation pit under different working conditions, and suggests that the role of the expansion force in foundation pit design cannot ignore. Controlled by numerical simulation and actual conditions of the proposed characteristics of expansive soil load distribution according to the practical significance and certain effectiveness; Had significant effect on the expansive force for the design of cantilever pile; The protection of expansive soil slope is mainly stability of the soil moisture content.