| One reason for 90% deep foundation pit incidents in Wuhan, was failure of controlling underground water. Among them, confined water aquifer is very common in the First Yangtze River's terrace, the aquifer is thick, and the water head is high, which is very typical in deep foundation ditch project of Wuhan. Therefore, studying on change law of land subsidence and foundation stability caused by precipitation and excavation is of important practical significance.The major works are as follows:(1) Based on groundwater seepage calculation and three dimensional Biot consolidation theory, fluid-solid coupling effect of precipitation and excavation about deep foundation pit is analyzed. Seepage field and stress field coupling calculation model is established. And the fluid-solid coupling calculation model by using FLAC3D was studied. (2) Groundwater type and disaster of First Yangtze River's terrace in Wuhan foundation are summarized and analyzed, and the confined water are studied mainly. Then the construction process of a shaft excavation are simulated by using FLAC3D, The numerical simulation results show good agreement with the monitoring data, which verify rationality of the FLAC3D fluid-solid coupling model and the programming ideas. (3) Finally, seepage-stress coupling simulation of Gongye station's precipitation and excavation is carried out with FLAC3D, and all the results of settlement, pore pressure, swell of pit bottom, hydrodynamic pressure are stydied. Then the affect of changes in diaphragm wall depth, confined water level, coupling or no coupling are compared.The results show that, Surface subsidence show a settlement groove of quadratic function curve, causing precipitation than the settlement due to excavation of a large; confined water head is high at Wuhan First Yangtze River's terrace, swell of pit bottom is large; Seepage velocity is largest under the diaphragm wall, prone to infiltration and sabotage, as the wall height increases, longer flow paths, will lead to increased head loss and flow rate decreases; Confined water of Wuhan First Yangtze River's terrace is closely associated with the river, confined water head is higher, surface subsidence is larger; Compared to no coupling, coupling the results considering the actual rule is more consistent with the project, can play a better prediction and information for construction. This paper makes up for preliminary study on seepage and groundwater control of Wuhan First Yangtze River's terrace. It provides a theoretical basis for waterproof and reinforcement design in foundation construction process, and it provides an experience and reference for design and construction of similar projects in future. |
