Study On The Influence Of Water Supply Pipeline Leakage On The Excavation Deformation Of Loess Foundation Pit

The soil strength of loess decreases rapidly after water exposure,so it is easy to cause engineering safety accidents after water immersion of loess foundation pit.At present,there are few reports on the stability of loess foundation pit excavation by water immersion.In this paper,the calculation method of excavation deformation considering humidification is established,and the study of deformation stability of loess foundation pit under humidification condition has important engineering guiding significance.Based on the fluid-structure coupling theory,a model of immersed foundation pit in loess area is established,and the influence of the quantitative relationship between soil strength parameters and water content on the deformation rule of foundation pit excavation is innovatively considered.The following conclusions are reached:(1)Based on unsaturated soil seepage theory,soil consolidation theory and fluid-structure coupling theory,the deformation of support structure in loess excavation under water immersion is analyzed.The results show that the excavation deformation is greatly affected by soil moisture disturbance.(2)Based on the experimental data of shear strength of unsaturated loess in Xi ’an,Yulin,Lanzhou,Xining and Golmud,the quantitative relationship between soil strength parameters and water content applicable to Xi ’an area is obtained.(3)According to the engineering investigation report,the finite element software COMSOL Multiphysics was used to establish the foundation pit water immersion excavation model,and Richards seepage theory was applied to calculate the foundation pit water field.The quantitative relationship between soil strength parameters and water content was applied to correlate the water field and the mechanical field.The influence of pipeline leakage on the horizontal displacement of foundation pit supporting pile,the surface settlement outside the pit and the change and rule of anchor cable axial force is analyzed.(4)According to the different design parameters of the supporting structure,such as pile diameter,embedment depth,anchor cable prestress,anchor cable inclination Angle and vertical distance of anchor cable,the influence of supporting structure design parameters on the horizontal displacement of the supporting pile and the surface settlement outside the pit is studied by setting various working conditions.(5)The influence of load and distance of adjacent buildings on horizontal displacement and surface settlement of waterlogged foundation pit is analyzed.