Study On Different Forms Of Vertical Reinforcement In Deep Excavated Pit In Soft-clay Area

The foundation pit engineering is an ancient subject, but there're still many problems needing further research. The increase of the pit's depth and size brings some difficulties to the protection of the surroundings The main problem is the ground settlement and the uneven settlement of the buildings around the pit Usually there are some ways to control the displacement, such as strengthening the retaining structures, increasing the stiffness of the bracing system or reinforcing the internal and external soil of the foundation pit. From the Wenzhou New Century Project, It is obvious that in soft clay area the early displacement had significant impact on the final deformation of the retaining structure. So the design based on the traditional method in which this factor is ignored will be unsafe. In this paper, not only the soil of the bottom area, but also the vertical soil of the boundary of the pit and bracing system will be reinforced.As is known to all, the current designing method which is based on the sheet and pile structure has its own shortcomings. The displacement and the moment of the retaining structure changed by the excavating process will not be taken into consideration. And the most popular designing software, such as Li Zheng and Wei Hu Jie Gou Da Quan, still can not consider the function of this reinforcement method either.Firstly, in order to solve this problem, two new concepts will be introduced: the effective solid-bed depth and the equivalent coefficient value of "m". Then the formula which can calculate the function of the new reinforcement method will be deduced. It is necessary to state that this result is based on some assumptions. Subsequently, five different reinforcement programs are designed for Wenzhou New Century Project. And these programs are compared and analyzed by calculating.Finally, In ABAQUS, A two-dimension model which can consider the process of the excavation, the different heights and the different widths of the reinforcement soil, will be established. Through ABAQUS, the respective results of those reinforcement programs will be compared and analyzed.