| With the fast development of the national economic construction, the space on the ground can't meet our need. And the underground space has been developed gradually. In this condition, open-cutting is impossible. At the working stage, therefore it is important to choose the foundation ditch bracing project for the safety and economic performance of the foundation ditch engineering when the foundation pit is large and the surrounding is complicated.This article takes the foundation ditch bracing engineering of AnDe Mansion in Peking for an example.After the comprehensive consideration about the practical condition of the working site, we have chosen the most economical and feasible soil-nailing wall bracing structure and made an complete introduction about the whole process of the foundation ditch bracing engineering.Based on the development process of the soil-nailing wall, analyzing and researching the soil nails afford the function with the soil in the original place. And it can increase the consolidated function of the border slope's whole rigidity and stability. The soil nails can make the function with other bracing forms and it's suitable to develop itself to the soft soiled district by some sticky soil and unloosing sandy loam.In the part of the design of soil nails bracing structure,it introduces the design methods provided by the standards, including the defining the geometry size and the calculating of the pull-resisting maximum state, and the calculation of the soil nails' length, the anchor-fixing maximum state.And the experimental analysis of the soil-nailing wall displacement. The aim is to exploit a practical designing method to calculate to maximum state based on the method to calculate displacement. The experiment makes use of the limited analytic method to calculate the displacement of the soil-nailing walls exactly. And we find that the calculating result and the measuring result and so similar. The author cites the soil-nailing wall displacement experiment in Franch in 1991 and contrastively analyses that the current norms the methods based on the classical maximum balance method. The limited basic method in the introduction is helpful to develop the soil-nailing wall design towards the surface and more economic direction.In conformity with the safe and economic principle, the author finished the foundation pit bracing project of AnDe Mansion. There are the results:1. Design of foundation pit dewatering .We design it according to the demand of this project and the condition of hydrology and geology.The model of water-gushing in a pit is presumed to be the model of diving intact well near the water-separating boundary in the rainy season. We design the depth of the water level of the pit is 14m,the depth of the well is 26m,the dots of the well are 37.2. Design of earthwork. On the basis of the basic map of AnDe Mansion and the bracing map. We calculate the total digging number is 100 thousand M3 the number of cubic meter of soil to be refilled in is 8404M3 .We also have designed 2 excavators and disposed 23 cars by calculating the excavators. 3. Design of mini pile combined with soil nailing bracing structure. The mini pile combined with soil nailing bracing structure is an improved method according to the project's practical condition. It also bases on the northeast mini pile bracing structure and soil-nailing wall bracing structure. There's the friction between the mini pile and the soil. It affords a function of resisting soil's overturning. By combining the mini pile and the soil nail, we can develop the advantages that reduce the distance of the bracing structure and the reasonable force that the soil nailing bears.And we also can improve the inner stability and safety of the soil nail structure efficiently. To this project because the mini pile is one part of all bracing structure. We can't get a certain model and make the check computations the curve-resisting. So we can't do the check computations of muscle-mating.4. Design of pile with man-excavated shaf...
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