Numerical Analysis Of Soil Disturbance In Porous Pipe Jacking Considering Grouting Effect

As a commonly antifriction measure in pipe jacking engineering,injection of thixotropic mud(simultaneous grouting of pipe joints)has been used widely.Especially in the case of complex formation conditions or long jacking distance,by injecting thixotropic mud into the soil layer,a drag reducing layer(commonly known as filtercake)can be formed on the outer wall of the pipe joint to effectively support the surrounding rock of the hole wall,stabilize the over excavation area and improve the jacking efficiency.However,injection of thixotropic mud will aggravate the soil disturbance around the pipeline,resulting in complex mechanical behaviors such as unloading or loading.Therefore,the influence of grouting should be considered when studying the soil disturbance of pipe jacking engineering.In recent years,with the needs of urban underground space development,the number of porous pipe jacking projects with large section and small spacing is gradually increasing,which provides a new research direction for the disturbance of pipe jacking soil considering the influence of grouting.Therefore,taking the porous parallel pipe jacking as the research object,this paper uses the numerical simulation research method to study the distribution and influence law of filtercake and the soil disturbance of porous parallel pipe jacking after considering the influence of grouting.The main research contents and results are as follows:(1)Considering three kinds of grouting hole diameter,five kinds of grouting pressure,three kinds of sand layer permeability and two kinds of sand layer hydrodynamic viscosity,the numerical simulation calculation scheme is designed by using the single factor typical parameter analysis method.Based on the mathematical model of two-phase Darcy’s law seepage field,COMSOL multiphysics finite element software is adopted,The diffusion law of slurry in saturated sandy soil layer and its influence on filtercake thickness under hydrostatic conditions are analyzed.The distribution characteristics of slurry caused by grouting and the applicability of slurry in sandy soil layer are obtained.The results show that the grouting pressure and the diameter of grouting hole have a great influence on the filtercake thickness when other conditions remain unchanged.(2)Taking the actual project as the background,the filtercake thickness under the engineering grouting pressure is calculated by COMSOL multiphysics finite element software,and the filtercake is set as an equivalent layer.The soil disturbance of porous pipe jacking considering the influence of grouting is deeply analyzed by ABAQUS finite element software.The vertical displacement and cumulative settlement of the surrounding rock at different positions away from the excavation face are calculated,the secondary disturbance of the porous jacking to the soil surrounding rock is analyzed,and the laws of transverse disturbance and longitudinal disturbance of the porous jacking soil considering the influence of grouting are obtained.By comparing the cumulative longitudinal settlement and transverse settlement of soil under different jacking sequences,the optimal jacking sequence is obtained.The research results of this paper have certain reference value and significance for the design and construction of porous pipe jacking engineering considering the influence of grouting.Figure[41]table[10]reference[54]...