Research On Deep Foundation Pit Support By Cut-and-Cover Method In Tazi Mountain Park Station

Owing to the development of the subway construction in recent years in China, it isimportant to design the deep foundation pit bracing structure for metro station and research itsdeformation laws. Many scholars and experts who are at home and abroad do a lot of research.They have acquired some achievements by some methods, such as theoretical analysis, themodel test, the field test and numerical simulation, but it,s uncertain and complex, so theresearch of supporting deep foundation pit still need to be deeply.This paper takes “the subway station of TaZi Mountain in Chengdu” as a studytarget. Because there is a kind of clay in Chengdu more stickier than the average clay,therefore, it,s based on the information and data collecting, sorting and analyzing, this articledesigns the system of the deep excavation pile anchor bracing, and establishes theelastic-plastic model by the numerical simulation software. The main research work andresults as follows:According to the geological engineering data, and combining the conditions andexperience of the deep foundation pit supporting type selection in subway station in Chengdu,the article chooses the pile anchor bracing as deep foundation pit supporting system, and dosome designs, includes the calculation of earth pressure, the choice and calculation ofretaining piles, the calculation of anchor and so on.According to the engineering conditions, it builds2d model using numericalsimulation soft way, which is easy to calculate and analyze. Using DP elastic-plastic modelfor soil model, by comparing the deformation of foundation pit and the shear and bendingmoment of pile, which the anchor bolt is in clay layer and pebble clay layer, it is found thatthe deformation of foundation that the anchor bolt is in clay layer is smaller than that is inpebble clay layer, and the shear and bending moment of pile is more uniform. In Chengdu,using the pile anchor bracing, the anchor that is embedded in the sticky soil is safer and moreeconomic for foundation pit than that is in pebble clay soil layer.Based on the“element birth and death method”in numerical analysis software, it hasthree steps to excavate the foundation pit. In addition, it needs to analyze the stress and strainof foundation pit, the supporting pile of shear and blending moment when the foundation pitis excavated before and after each step, and gets the corresponding deformation laws. Thedeformation of foundation pit is based on the depth of excavation, first increases, thendecreases, it achieves maximum when the pile gets about2meters, the hunch of pit bottom isbigger and bigger, and the middle of pit decreases towards both sides.Arranging and analyzing the monitoring data, especially, the lateral displacement ofretaining pile and the settlement of the ground surface, furthermore, comparing with the results of numerical simulation, it concludes that the surface settlement is relative to thedistance that the edge of the foundation pit excavation, rainfall and the load. Meanwhile, thenumerical simulation and field data are coincident. It indicates that the numerical simulationcan reflect the change laws of actual condition.The research conclusion is of some reference value for design of the deep foundation pitbracing in subway station in Chengdu. It can supply some useful information for practicalengineering.