Mechanism of Disease and Leakage of Existing Drainage Pipes in Beijing
The drainage pipelines put into use in the early stage have been faced with various problems with the rising of groundwa-ter level and the increase of service time of drainage pipelines in Beijing,among which the failure of drainage pipeline structure is par-ticularly 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 influ-ences of these three factors on the failure mechanism of pipelines were further investigated.Based on the parameters of a practical pro-ject,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 prob-lems 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 safe-ty 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 struc-ture of drainage pipelines.And line,the main measurement and treatment measures should be adopted for the drainage pipeline orthog-onal to the ground traffic to maintain the safety of the pipeline structure and prevent leakage and disease.
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