Study On The Moisture Infiltration Law And Collapse Deformation Of Pipeline Leaking In Loess Site

The urban transport water pipe network is an important infrastructure of the city,due to various factors,there are often a large number of hidden long-term leakage points.The resulting pipeline leakage has become the main cause of foundation collapse of loess buildings.This paper is based on investigation of the seepage water condition of the pipeline,and the infiltration laws of water and deformation characteristics of the loess foundation are studied.Firstly,the distribution and leakage data of the transmission water network in Xi'an were collected and arranged.After multi-phase construction,Xi'an urban water supply pipelines and rainwater sewers were laid over a total of more than 5,000 kilometers,with a very dense distribution.Due to a variety of factors,the aging of the pipeline network is prominent,and the operating pressure is high.All of these factors lead to a high leakage rate and frequent occurrence of leaks.Subsequently,through the intact loess depression test and field immersion test study,the water infiltration law and the deformation characteristics of collapse were studied.By analyzing the settlement monitoring results,the lower limit depth of self-weight collapsible loess is determined at the bottom interface position of Q3 loess layer.It is suggested that the correction coefficient of self-heavy collapsing amount of Q3 loess should be taken as 0.9.Finally,the numerical simulation of the leakage infiltration of the pipeline and the collapsing deformation of the foundation was carried out.A anumerical analysis was used to systematically analyze the influencing factors of water infiltration in pipelines.It was found that many factors,such as soil compaction degree,initial water content,pipeline water pressure,size of pipe leakage,depth of groundwater level,etc.,will have different effects on leakage infiltration rate and water infiltration range of pipelines.Based on this,the water infiltration range and collapse deformation of the rainwater sewer and tap water pipeline under the most unfavorable conditions were simulated.When the invasion range was maximum,the maximum deformation on surface of the rainwater sewer pipe leakage is 32.0mm,and the deformation influence range is 7m,and the maximum deformation of the tap water pipe is 36.2mm,and the influence range is 10 m.According to the results of the study,it is recommended that the correction factor of the loess dead weight of the site loess should be taken as 0.4 and 0.5 when considering the leakage of rainwater and tap water pipes leakage only,and the protection distances of the pipe laying on the test representative site should be taken as 8m and 11 m,respectively.Then,this paper give some prevention and control suggestions for avoiding collapse deformation of foundation caused by water leakage.