Study On The Influence Of Multiple Factors On The Deformation Characteristics Of The Pipeline Near The Excavation

The foundation pits of subway stations are usually constructed by cut and open,and the impact of the excavation of the foundation pit on the pipelines around the foundation pit is often very significant,resulting in more complicated stress and deformation of the pipeline.At present,the deformation laws of pipelines are not systematic.This paper studies the influencing factors of pipelines near the excavation of foundation pits by means of model tests,on-site data analysis,and numerical simulation,and the following conclusions are preliminarily drawn:Through the model test combined with the sensitivity analysis of the range method,the law is drawn: the pipeline displacement decreases with the increase of the distance from the foundation pit wall,depth,and pipe diameter.The maximum vertical and horizontal displacement of the pipeline appears in the middle of the foundation pit.It is the most sensitive to the change of the distance from the pit wall,followed by the buried depth,and the change of pipe diameter has the least influence on the pipeline deformation;According to the analysis of the measured data,the law is drawn: as the excavation of the foundation pit progresses,the settlement value of the pipeline gradually increases,and the construction of supports can effectively reduce the settlement value of the pipeline.When the pipeline is parallel to the width direction of the foundation pit,the maximum settlement value of the pipeline appears Near the middle of the end well;Through numerical simulation,the law of multi-factor analysis is obtained: the maximum vertical displacement of the pipeline increases with the increase of the width of the foundation pit,and the maximum vertical displacement appears in the middle of the foundation pit;among the supporting materials,steel supports have the best suppression effect on pipeline deformation.;Among different pipeline materials,the displacement value of the steel pipe is the smallest,and the displacement value of the PVC pipe is the largest;the displacement of the pipeline changes with the distance from the foundation pit and the division of the affected area of the foundation pit is consistent,when the distance between the pipeline and the foundation pit is near 0.7H The maximum value;the vertical displacement of the pipeline first increases and then decreases with the buried depth of the pipeline;the diameter-to-thickness ratio and internal pressure change have little effect on the pipeline deformation and can be ignored;the increase in the rigidity of the foundation pit floor can effectively reduce the pipeline displacement;The displacement of the pipeline decreases with the increase of the thickness of the ground connecting wall and the soil penetration ratio;Taking the maximum vertical displacement of the pipeline as the evaluation index,the sensitivity analysis of all factors is carried out using the single factor sensitivity analysis method,and the sensitivity of each factor is obtained: the sensitivity coefficient of the distance between the pipeline and the foundation pit is the largest,and the sensitivity coefficient of the internal pressure The bottom;the order of the sensitivity of the three factors of distance from the foundation pit wall,buried depth,and pipe diameter is the same as that calculated by the range method in the model test.The above analysis has certain practical engineering significance and theoretical value,and can provide a certain reference for actual engineering.