| In recent years,the accidents of urban road collapse occur frequently at home and abroad,which results in a huge loss of people’s lives and properties.In all the causes of the collapse accidents,the impact of pipeline leakage occupies a large proportion.So the analysis and study on collapse mechanisms of roads caused by leakage of urban underground pipeline is of great significance to guarantee the safety of people’s lives and properties.In this paper,the mechanisms of road collapse and the influencing factors of the road collapse were studied by means of percolation theory,laboratory model test and numerical simulation.(1)According to the different damage forms of the soil around the pipeline,the critical depth downrange of groundwater and the critical groundwater velocity,and the critical seepage velocity of the water are deduced when the infiltration of the water destroy the soil around the pipeline.(2)The relationships between the critical span of underground cavity and the exterior load,the thickness of overlaying soil,the cohesion and internal friction angle of the soil are deduced.(3)Through the laboratory model test,the underground cavity shape of the seepage failure of groundwater is conical cylinder,and the underground cavity shape of the soil’s erosion destruction is ellipsoidal.The development of the underground cavity form was studied through changing the forms and the size of the pipeline leakage.(4)Through the numerical simulation of FLAC3 D,it was considered that the critical span resulting in the endosmosis underground cavity collapse is 6m,when the thickness of overlaying soil is over 5m.The critical thickness of the overlaying soil resulting in cavity’s collapse is 4m,when cavity span is 3m.The decrease of the soil’s cohesion and internal friction angle leads to the decrease of soil strength and the instability of the underground cavity.When the cohesion is 13 kPa and the internal friction angle is 14°,the underground cavity will be unstable.(5)Through the numerical simulation of FLAC3 D,it was considered that the critical span resulting in the exosmosis underground cavity collapse is 4m,when the thickness of overlaying soil is over 5m.The critical thickness of the overlaying soil resulting in cavity’s collapse is 6m,when cavity span is 4m.The decrease of the soil’s cohesion and internal friction angle leads to the decrease of soil strength and the instability of the underground cavity.When the cohesion is 10 kPa and the internal friction angle is 14°,the underground cavity will be unstable. |
