Fixed Pier-Soil Shear Test And Earth Pressure Calculation Under Small Displacement Conditions In Heating Pipe Project

With the continuous expansion of the scale of cities,urban central heating tends to be universal.Large-diameter and high-pressure heating pipes produce large horizontal thrust,which causes the fixed pier to undergo micro displacement.Under the action of the micro displacement,the soil around the fixed pier is soiled.Pressure calculation and stability analysis of fixed piers have always been difficult issues in research.This subject will start from the stress form of fixed piers of urban heating pipelines,analyze the influence of heating pipelines on the stability of fixed piers during normal operation,and explore a safer and more accurate calculation method for fixed piers of pipelines.First,by analyzing the basic theory of the stability of the fixed piers of urban heating pipelines,using the method of comparative analysis before and after optimization of the fixed piers,comprehensively considering the influence of design thrust,micro-displacement,torsion and other factors,the corresponding calculation formulas are derived.Build a calculation system for fixed piers before and after optimization.According to the specific force form of the fixed pier before and after the optimization,the calculation formula for the stability of the fixed pier of the urban heating pipeline is revised.Secondly,with the help of indoor shear test methods,the soil-structure interaction of fixed piers before and after the optimization of urban heating pipelines was analyzed and discussed.The shear test is mainly divided into three parts,the direct shear test of the soil,the shear test of the outer protective layer of the heating pipe and the soil,and the external frictional shear test of the wall and soil considering the effect of micro-displacement.The direct shear test of the soil is used to analyze the shear strength of the soil;the shear test of the outer protective layer of the heating pipe and the soil explores the frictional resistance between the outer protective layer of the pipeline and the soil under the action of temperature,and then solves the problem.The horizontal thrust of the pipeline;consider the external frictional shear test of the wall and soil under the action of micro-displacement to solve the frictional resistance between the fixed pier and the soil and the development and change law between the external friction angle and the translational displacement.The latter is in the translational mode Lay the foundation for solving the non-limiting earth pressure.Finally,on the basis of the non-limit state earth pressure theory,combined with theoretical derivation,a method for calculating the non-limit state earth pressure of a fixed pier was proposed.It mainly included the solution of non-limiting active earth pressure under fixed pier translation mode,non-limiting passive earth pressure and non-limit state earth pressure under fixed pier rotation mode.The factors considered in this theory are more comprehensive and more in line with the actual situation of the project,and the stability of the fixed pier is analyzed with the research method and the standard method.