The Analysis Of Multi-stage Foundation Pit Based On M-method

With the development of our country, the process of urbanization is faster andfaster. The resource constraints of land have become increasingly prominent. In orderto strive for the building space, the development from the multi-storey to high-risebuilding has become a trend. To ensure the building stable and earthquake-resistant,also to make effective use of underground space, the foundation depth is more andmore deep. It has saved many land resources, but it also contributes to the muchmore difficult design and construction for the foundation pit.Under the conditions of the site, we can construct the foundation pit engineeringwith the multi-stage excavation. Then a big deep foundation pit is disassembled intoseveral small shallow ones. So that the difficulty of construction project is reduced,so as the support loading pressure on the retaining structure. This kind of deepfoundation engineering design can be named multi-stage foundation pit. Althoughthis form of excavation has already been applied in a number of projects, themechanism and the deformation behaviors of the retaining structures have beenrarely reported. Most of the designers calculate them still based on multipleindependent foundation pits, in which their mutual impacts are ignored.In this paper, the multi-stage foundation pit is resolved though m-method, whichis included in the elastic foundation beam method. After that, an analysis ofdeformation behaviors of the retaining structures has been studied. The main workincludes:1. Systematically reviewed the deep excavation works both at home and abroad,discussed the status of theoretical analysis and calculation method.2. Elaborated the theory of earth pressure, analyzed and discussed the soilpressure on retaining structures, then obtained the distribution form for thecalculation in this paper.3. By assuming displacement relationships between the two piles in the twosmall foundation pits, set up a solving model, which is solved by m-method and giveout the analytical solutions.4. Based on the analytical solution, the standard examples were analyzed in thisstudy. With the calculation result, expounded the influences between the two-pitsupport system at large. Many factors were considered, including the soil properties,the support stiffness, the excavation depth, the buried length of the shoring piles, thepile diameter, the width of platform, and so on. After that, their impact rules weregained.5. By using the Fujian Grand Theater engineering as the project example, thecalculation presented in this paper was verified. After comparing with the detailed monitoring data, the method was proved effective and reasonable, then proposedsome meaningful conclusions and recommendations for the design and constructionof the multi-stage foundation pit.The whole work of this paper was summarized in rear, and pointed out someshortcomings, which may be improved some day. Finally, the future developmenttrend was prospected.