| Municipal pipelines are widely distributed in the underground space,playing an irreplaceable role in the normal operation of the city.Tunnel excavation will disturb the adjacent soil,which will cause additional stress and deformation of buried pipelines,and even cause engineering accidents.Therefore,it is necessary to analyze the impact of tunnel excavation on pipelines to provide guarantee for the safe operation of buried pipelines.The method of treating the pipeline as Euler Bernoulli beam and the foundation as Winkler model has been widely recognized by scholars and engineers because of its clear concept,simple calculation and the accuracy of its results can also meet the engineering needs.However,most of the current researches do not fully consider the properties of pipeline joints,and there is no simplified evaluation method for engineering application;the research on the load-displacement curve of the pipeline relative to the soil moving in different directions is very limited;the nonlinear analysis of the pipe-soil interaction It is not deep enough;the analysis of the pipe-soil interaction when the pipe-tunnel is inclined is also insufficient.In view of the above problems,this paper adopts the methods of theoretical analysis and model test to carry out the research on the response buried pipelines by tunnel excavation.The main contents include the following aspects:(1)A theoretical method that can consider the position of joints is proposed by considering the relative stiffness of pipe and soil,the relative stiffness of joints and the position of joints,and a simplified linear elastic evaluation method for the influence of tunnel excavation on discontinuous buried pipelines is established.Based on the improved Winkler foundation model and considering the influence of joint offset distance,the governing equations of discontinuous pipeline considering any joint position and different soil settlement are obtained.The rationality of the theoretical calculation method is illustrated by comparison with the elastic theory,field test and centrifugal test.The influence of parameters such as the relative stiffness of the pipe and soil,the relative stiffness of the joint,and the relative length of the pipe section on the response of the pipeline is analyzed in detail.Based on the results of parameter analysis and the ratio relationship between the bending moment at the corresponding position of discontinuous pipeline joint and continuous pipeline,a simplified evaluation method considering the influence of various parameters on pipeline is established.The applicability of the simplified evaluation method is verified by comparing the results of field test and centrifugal test.(2)Model tests were carried out to pull buried pipelines in sand along different directions,and the load displacement curves and soil displacement distributions under different buried depths and moving directions were obtained.Using self-designed model device,a series of experimental studies are carried out on15 cases where the buried depth of the pipeline is 1.5,3 and 6 times of the pipe diameter and the relative movement angles are 0 °,45 °,90 °,135 ° and 180 °.The load displacement curves of the interaction between the pipeline and soil during the test are recorded and fitted;During the test,a high-definition camera was used to record the displacement change process of the soil during the test.When the relative displacement of the pipeline soil was 9.4,18.8,28.1,and 37.5 mm,the soil displacement was analyzed using PIV technology,and the displacement vector diagram and deformation cloud map were drawn,and the soil displacement law is analyzed and summarized.(3)Based on the hyperbolic double spring foundation model of pipe-soil interaction,a nonlinear analysis method for the influence of tunneling on continuous pipelines is established,and the normalization law of bending moment and pipeline stiffness of continuous pipelines is obtained.Normalization analysis for inclined intersection between the pipe and the tunnel is then conduced.The fourth-order deflection differential equation and its difference method for hyperbolic nonlinear model of continuous pipeline under passive displacement are introduced in detail,and a hyperbolic nonlinear model considering the change of foundation modulus is introduced.Computational differences between the elastic method and the hyperbolic nonlinear method are discussed through a field test analysis.The common engineering parameters in municipal engineering are selected to study the bending moment and pipeline stiffness under various conditions,and the distribution pattern of normalized bending moment with normalized pipeline stiffness is obtained.Field tests and two groups of centrifugal tests are selected to analyze the applicability of the normalized graph.Finally,the normalized analysis and application are made to the situation where the pipeline and the tunnel are inclined and intersected.(4)A nonlinear analysis method and equivalent linear simplified evaluation method for the influence of tunneling on discontinuous buried pipelines is established.Calculation formulas for the ultimate bearing capacity of pipelines in different directions of movement are then obtained,which are applied to the simplified evaluation of discontinuous pipelines when a pipeline intersects a tunnel obliquely.Based on the theoretical analysis method of jointed pipeline in tunnel excavation,combined with the hyperbolic nonlinear model,the hyperbolic nonlinear theoretical calculation method of discontinuous pipeline is proposed.The equivalent elastic modulus fitting formula is obtained through the analysis of examples,and the equivalent linear simplified evaluation method for discontinuous pipelines is established;the model test results are fitted,and the ultimate bearing capacity formula considering the relative movement angle of pipe and soil is obtained.Furthermore,an analysis method of decomposing the soil displacement on the inclined plane and then synthesizing the response results of the pipeline under the action of the decomposed displacement is proposed.The feasibility of the method is illustrated by a numerical example,and the method is used to calculate the case of pipe-tunnel oblique intersection. |
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