Numerical Research On Impact Of Metro Excavation Failure On Adjacent Masonry Building In Soft Soil Area

The metro excavation failure involves soil large deformation,not only the safety of the foundation pit will decline,but also surrounding buildings will be cracking damage due to uneven settlement and their normal function will be affected,which has negative social impact.Therefore,it is important to analyze the failure mechanism of the metro excavation failure and the influence rule of the surrounding building to avoid the metro excavation failure and the secondary damage to the surrounding critical building.By using the material point method,problems based on the different failure modes of the subway foundation pit are studied,and the main conclusions are as follows:(1)For the kick-in of the excavation,the excavation depth can produce significant effect on the foundation pit kicking when the insertion ration of diaphragm keeps unchangeable.With the length of diaphragm getting shorter,the kick-resistant stability decreases.As the stiffness of diaphragm increases,the deformation of foundation pit decreases.(2)For the overturn of the excavation,with the stiffness of the bracing decreasing,the maximum lateral displacement of the diaphragm wall increases,which means the degree of the overturn increases,thus the soil displacement increases.With the stiffness of the diaphragm wall increasing,the maximum lateral displacement of the diaphragm wall decreases,which means the degree of the overturn decreases,thus the soil displacement decreases.But when the stiffness of the diaphragm wall increases to a certain degree,the deformation of the diaphragm wall itself is very small,and it almost presents a whole rigid motion.And the soil displacement also keeps about the same.(3)When the maximum lateral displacement of the retaining structure for both the kick-in and the overturn are the same,the influenced zones of the ground surface displacement for the kick-in of the excavation is larger than the overturn of the excavation.And the scope of the influenced zones decreases as the depth increases for the kick-in and the overturn of the excavation.The main influenced zones of the kick-in are the soil around the bottom of the wall,while the main influenced zones of the overturn are the shallow soil close to the excavation.(4)For both the kick-in and the overturn of the excavation,the first floor of the surrounding masonry building presents different width of tensile crack,while the second floor presents a whole rigid motion.(5)when the stiffness of the masonry building is small,the constraints and coordinating to the soil displacement are small.Therefore,for the kick-in and the overturn of the excavation,the deformation of the masonry building itself is large.With the stiffness of the masonry building increasing,the constraints and coordinating to the soil displacement get enhanced.Thus,for the kick-in and the overturn of the excavation,the deformation of the masonry building itself is getting smaller.