Experimental Study On The Deformation And Damage Of Underground Pipeline Caused By The Settlement And Collapse Of Soil

In recent years, geological disasters such as the settlement and collapse of soil have occurred frequently, which have caused very serious damage to the urban underground pipeline system and brought a great deal of inconvenience to the life of urban residents. At present, our awareness to geological disasters is not yet comprehensive and in-depth, which makes the prevention and maintenance of urban underground pipeline system before and after geological disaster have many difficulties and often result in large security risks and economic losses. Predecessors have made some research on this subject and achieved some results, however, the most previous research focused on computer simulation by using finite element software. Due to the uncertainty of the various computer model parameters, such research method is still in the immature stage. In view of this, this paper has researched the deformation and damage of underground pipeline caused by the settlement and collapse of soil through the experimental simulation and achieved the following conclusions:The axial and circumferential deformation of PE pipe:1. The slope of the deformation changing with time at the upper portion of pipeline cross-section is bigger than the middle upper portion; the slope of the deformation changing with time at the lower portion of pipeline cross-section is bigger than the middle lower portion, the slope of the deformation changing with time at the middle portion of the pipeline cross-section is the least.2. The slope of the deformation changing with time at the middle cross-section and the end cross-section of pipeline are bigger than the slope of the deformation changing with time at a quarter of pipeline span cross-section.3. From the view of the axial deformation of the pipeline, the axial deformation at a quarter of the pipeline span is mostly the tensile deformation, the axial tensile deformation of the entire pipeline is much more than the axial compressive deformation, and the axial tensile deformation of the entire pipeline is obvious, especially in the constraints of fixed ends.4. Generally, the mechanical deformation state of the circumferential deformation at each portion of every pipeline cross-section is just opposite with the axial deformation in the same portion of the pipeline cross-section. From the view of the circumferential deformation of the pipeline, the circumferential deformation at a quarter of the pipeline span cross-section is mostly the compressive deformation, the circumferential compressive deformation of the entire pipeline is much more than the circumferential tensile deformation. Due to the axial tensile deformation of the entire pipeline, the necking phenomenon of the pipe cross-section is obvious, especially in the constraints of fixed ends. The properties and the ageing of the deformation and damage of the pipelines with different wall thickness:1. The PE pipeline has a large range of plastic deformation and an excellent recovery ability of flexural deformation. However, with the wall thickness of the pipeline increased, the plastic deformation ability of the PE pipeline gradually weakened, the pipeline even could appear tensile failure in short-time load.2. When the pipelines which have different wall thickness are in the same deflection, the greater wall thickness the pipeline has, the greater strain the pipeline produces.3. When the central deflection of the pipeline is less than20cm, the change of the wall thickness of the pipeline has little impact to the relationship between the force and the deflection of pipeline. When the central deflection of the pipeline is more than20cm, the change of the wall thickness of the pipeline has obvious impact to the relationship between the force and the deflection of pipeline.4. In the short-term load, PE pipeline will occur great flexural deformation but generally not destruction, and If unloaded timely, PE pipeline can recover most of the flexural deflection. However, if the load is not removable for a long time, the PE pipeline will eventually appear destruction and quit work due to the role of the long-term load.