Study On Damage Formation Of Buried Water Supply Pipeline Under Earthquake

Since China is located in a seismic belt with frequent earthquakes,the water supply pipeline is buried underground.When the earthquake occurs,the damage of the pipeline cannot be immediately known,which makes it difficult to repair the pipeline.Therefore,it is of great practical significance to study the damage formation of pipelines under the coupling of earthquake action and soil-pipe-water interaction,and to accurately judge the damage of pipelines.This paper comprehensively considers the seismic action and the soil-tube-water coupling effect,and conducts a comprehensive force analysis on the pipeline.The simulation model of buried water supply socket,straight pipe and elbow was established by ADINA.The stress and strain of the pipeline were analyzed.According to the material properties of the pipe,the damage formation of the pipeline was judged based on the stress strain and the stress and strain at the damage was analyzed.The research content of this paper is mainly as follows:1.Considering the seismic action,pipe soil action and fluid-solid coupling to establish the theoretical calculation model of buried water supply pipeline,the calculation of axial displacement,axial tensile stress,axial bending stress and hoop stress of pipeline under various actions is proposed.By comparing the axial displacement and the allowable displacement,the combined stress and the yield strength are used to determine the damage of the pipeline.2.The model of buried socket tube under seismic excitation was established by using ADINA,and the axial direction of the socket was calculated under different pipe diameters,depths and seismic intensities.It was found that the location of the damage to the socket pipe first appeared at the joint.When the intensity is VII,the axial displacement of the pipe decreases with the increase of the pipe diameter,and several common pipe diameters are damaged.The axial displacement of the pipeline decreases with the increase of the buried depth.When the buried depth reaches 1.8m,the axial displacement of the pipeline is within the allowable displacement range,and the pipeline is considered to be in good condition.The axial displacement of the pipeline increases significantly with the increase of the intensity.Only when the intensity is 6,the socket pipe is in good condition.When the intensity is 8(the basic acceleration value of earthquake is 0.3g),the pipeline is destroyed.3.The model of buried water supply straight pipe under seismic excitation was established by ADINA,and the combined stress of straight pipe section under different pipe diameter,depth and intensity was calculated.The position of the straight tube was found to be mainly in the middle of the fixed end and the tube.The time of damage to the pipeline increases with the increase of the pipe diameter.When the pipe diameter is DN500,the pipeline is not damaged.The damage time increases with the increase of the buried depth,when the buried depth reaches 1.8m,the pipeline is in good condition.The damage time decreases with the increase of the intensity,and the pipeline is in good condition only when the intensity is 7(the basic acceleration value of earthquake is 0.15g).4.The model of buried pipe bending under seismic excitation is established by using ADINA,and the combined stress of elbow section under different pipe diameter,depth and intensity is calculated.It was found that the damage position of the elbow was mainly at the bottom of the middle of the elbow.the damage time of the elbow increases with the increase of the pipe diameter.When the pipe diameter is DN300 or DN350,the pipe is destroyed.The damage time increases with the increase of the buried depth.After the buried depth reaches 1.8m,the elbow is in good condition;when the intensity reaches 7th level,the elbow is quickly damaged and then destroyed.5.Comparing and analyzing the damage of socket,straight pipe and elbow under earthquake action,it is found that when the pipe diameter reaches DN500,the pipe is generally not easy to be damaged,and the pipe can operate normally under the damage condition.When the buried depth reaches 1.8m,the pipeline is in normal operation.Therefore,for deep buried pipelines,the buried depth has little effect on the pipeline;the impact of seismic intensity on the pipeline is significant.For strong earthquakes,most pipelines will be damaged.6.According to the actual engineering conditions,the axial displacement and straight pipe combined stress of the socket pipe in the two regions were calculated by ADINA software.The damage formation was judged by the damage judgment criterion.The calculation results were consistent with the actual situation,which verified the feasibility of the damage determination criterion.