基于北京既有排水管道的病害产生及渗漏机理

Mechanism of Disease and Leakage of Existing Drainage Pipes in Beijing

随着北京地下水位的上升和排水管道服役时间的增加,早期投入使用的排水管道已经陆续出现各种问题,其中,排水管道结构损伤问题尤为突出。为了探究排水管道病害机理,基于对北京既有排水管道的病害调研,分析管道结构产生损坏的原因,得到背后脱空、地下水位变化、地面车辆荷载3种关键因素,并分析了事故产生机理。通过工程实例进行数值模拟,计算分析水平位移、竖向位移、安全系数等相关参数,以此为基础进行病害机理的研究。研究发现:造成排水管道事故的关键性因素是管线渗漏水,原因主要有生存环境、施工扰动、承载能力;管线事故中,有70%是由于管线生存环境导致,此外施工扰动占25%,管线自身原因仅占5%。自然环境以及施工质量问题易导致管线周围形成小范围非密实区,进而演化为空洞等严重非稳定体;排水管道背后脱空的出现会导致管道结构安全系数出现较大折减;地下水位上升会影响排水管道结构的安全性能,使得既有管线的安全系数降低;当路面车辆荷载正交于排水管道作用时,结构受到荷载影响最大,同时结构上部安全系数显著小于其余工况。在实际运营中应当重视背后脱空对双线管线结构的影响,同时,对于与地面交通线正交的排水管线,要勤加观察和测量,采取措施维护管道结构安全,防止渗漏病害产生。

The drainage pipelines put into use in the early stage have been faced with various problems with the rising of groundwater level and the increase of service time of drainage pipelines in Beijing,among which the failure of drainage pipeline structure is particularly prominent.In order to study the failure mechanism of the drainage pipeline structure,the causes of the failure of the drainage pipeline structure were analyzed based on the site investigation on the diseases of the existing drainage pipelines in Beijing.Three key factors including the backside empties,the change of groundwater level and the load of ground vehicles were obtained,and the influences of these three factors on the failure mechanism of pipelines were further investigated.Based on the parameters of a practical project,a series of numerical simulations were carried out to calculate and analyze the related parameters of pipelines such as horizontal displacement,vertical displacement and safety factor so as to investigate the failure mechanism of pipelines.The results show that the key of drainage pipeline accidents is pipeline leakage,and the main reasons are living environment,construction disturbance,bearing capacity,respectively.Moreover,70%of pipeline accidents are caused by pipeline living environment,and 25%of that are caused by construction disturbance,while only 5%are caused by pipeline itself.Besides,the natural environment and construction quality problems easily lead to the formation of a small range of non-dense areas around the pipeline,which then evolve into serious unstable bodies such as voids.The appearance of voids between the drainage pipelines and the soil will lead to a large reduction in the safety factor of pipeline structure.The rise of groundwater level will affect the safety performance of the drainage pipeline structure and reduce the safety factor of the using drainage pipeline.When the road vehicle load is orthogonal to the drainage pipeline,the influence of the vehicle load on pipeline structure is the most,and the safety factor of the upper part of the structure is significantly smaller than that of other conditions.Therefore,more attention should be paid to the influence of voids between the drainage pipelines and the soil on the structure of drainage pipelines.And line,the main measurement and treatment measures should be adopted for the drainage pipeline orthogonal to the ground traffic to maintain the safety of the pipeline structure and prevent leakage and disease.