Study On Bearing Characteristic Of Gas Pipeline Under Widening Subgrade

Restricted by the technical level and economic level of early road construction,the original road can not meet the existing traffic demand,and road widening has become one of its solutions.The biggest problem of road widening is the uneven settlement between new and old roadbed and a series of problems caused by it.Especially when all kinds of pipelines are buried under the roadbed,such as gas pipelines,the problem becomes more complex.At present,the theoretical research on the load-bearing and deformation characteristics of gas pipeline under widened roadbed is insufficient.Therefore,this paper intends to carry out systematic research through theoretical analysis and numerical simulation combined with engineering examples。Firstly,the settlement of widened roadbed is discussed and divided into three aspects: analytical solution,numerical simulation and field test.The analysis of buried pipeline is summarized.Based on the existing research results,according to the theory of elastic foundation beam,the pipeline is regarded as an elastic foundation beam(i.e.pipeline beam)on Winkler foundation,and the soil and vehicle loads above the pipeline are simplified,which are equivalent to uniform loads.A mechanical analysis model of gas pipeline under widened roadbed is proposed.According to the basic principle of elasticity,the basic differential equation of pipeline beam is deduced and its analytical solution is derived.In addition,for the finite-length beam subjected to arbitrary uniform load,the author analyzed the boundary conditions of the foundation beam,obtained the analytical solutions of the displacement and internal force of the pipeline under five different working conditions,and analyzed the settlement and internal force variation law of the elastic foundation beam under different boundary conditions through an example。The traditional Winkler model does not consider the shear deformation of the interface between the foundation beam and the foundation.Based on Winkler foundation model,this paper considers the shear deformation of the upper and lower surfaces of the pipeline beam,and proposes an improved mechanical model of the elastic foundation beam on Winkler foundation.Considering the condition of small deformation,the differential equations of the beam are deduced according to the principle of mechanics,and the analytical solutions of the unloaded section and the unloaded section are obtained respectively by the differential operator series method.For infinite beams,the above analytical solutions can be used for direct calculation,while for finite beams,the superposition method is used to solve the problem on the basis of infinite beams.The example analysis shows that when Kx = 0,the solution can be reduced to the elastic foundation beam solution without considering the shear deformation of the interface,which verifies the correctness of the solution。Finally,the finite element software ABAQUS is used to establish the numerical model of gas pipeline under widened roadbed for analysis.Pipeline is simulated by three-dimensional solid element,assuming linear elastic material.Mohr-Coulomb model is used for constitutive model of soil material,and pipe-soil interaction is considered.The results show that the widening of roadbed has a certain effect on the deformation of pipeline underneath,and the change is obvious on the widening side,but not on the widening side。At the same time,according to the comparative analysis of finite element and theoretical results,the settlement value of pipeline is closer to that of finite element when considering shear action,and the settlement decreases by 20% when not considering shear action;the result of finite-length beam theory is more conservative when calculating,while the result of infinite-length beam theory is more accurate when considering shear deformation of interface.Through the analysis of parameters such as widening mode and widening width,it is shown that the settlement of pipeline increases by about 30% when the widening width increases from 1 m to 5 m,and the settlement of pipeline increases by about 60% when the widening width increases from 1 m to 5 m。...