Analysis On Deformation Of Expansive Soil Tunnel And Influence On Adjacent Buildings Under Humidification Condition

With the acceleration of the construction of infrastructure such as railways,subways,and highways in China,as a widely distributed expansive soil condition,the construction of many tunnels cannot avoid expansive land layer.Expansive soil is a highly plastic clay with water absorption volume expansion and strength attenuation,water loss volume shrinkage and easy to produce cracks.Under humidified conditions,the moisture content of the expansive soil increases,the strength of the soil decreases and expansion occurs,resulting in a decrease in the stability of the surrounding rock oftunnel,and easily lead to a decrease in the reliability of the supporting structure and excessive deformation of tunnel.When serious,the tunnel will collapse.Therefore,under humidification conditions,studying the deformation of expansive soil tunnels has important engineering practical significance.This paper mainly considers the expansion characteristics and strength attenuation characteristics of the expansive soil after humidification,combined with the indoor test of the expansive soil,and based on the fluid-solid coupling theory,the expansive soil tunnel in Hefei area is studied by the method of establishing a calculation model with ABAQUS software.The specific research content and conclusions are as follows:(1)Taking soil samples from the construction site for a series of laboratory tests,the basic properties of expansive soil in the study area were defined,including basic physical properties,expansion and contraction indexes,and mechanical indexes.Through direct shear tests under different water content,the change law of the strength of expansive soil with water content is measured,and mathematical empirical formulas are established.The matric suction of expansive soil in Hefei area was measured by filter paper method under different water content,which provides the required data for the numerical simulation.(2)Based on the theory of fluid-solid coupling,using the seepage module of ABAQUS to simulate the unsaturated seepage of expansive soil,obtain the soil moisture-stress field,and verify its correctness.Combining the humidity field of the soil and the temperature field module of ABAQUS and writing Python subroutines can realize the humidification expansion and strength attenuation of expansive soil.(3)Using the above method,the model of a two-way expansive soil tunnel in Hefei is established.Considering the three humidification situations of rainfall infiltration,the increase of water content around the tunnel and the rise of groundwater level,different working conditions are set for different humidification conditions,and the effects of various internal and external factors on expansive soil tunnels under different humidification conditions are comprehensively analyzed.The deformation of the surrounding rock and the force characteristics of the supporting structure are affected.The main conclusions are as follows:(1)Under the condition of rainfall infiltration,the surrounding rock of the tunnel will eventually be transformed from vertical extrusion to horizontal extrusion;after considering excavation disturbance,the force impact on the supporting structure is very large,and with the disturbance With the increase of the degree,the maximum bending moment of the support increases significantly.(2)When the water content around the tunnel increases,the surrounding rock displacement increases as a whole,and at the same time the force characteristics of the vault position of the supporting structure change.(3)When the groundwater level rises,the initial height of the water level has a greater impact on the bending moment at the side wall of the supporting structure.As the water level rises higher,the bending moment of the supporting structure becomes larger.(4)Taking a certain section of Hefei subway as the engineering background,combined with the above-mentioned expansive soil humidification simulation method,the impact of expansive soil tunnel excavation on neighboring buildings is analyzed.The results show that if the humidification of the surrounding rock of the tunnel is considered,the deformation of adjacent buildings will increase significantly,and the application of anchor rods at the invert can greatly reduce the deformation of adjacent buildings.