Abstract:

The onshore section of Nanhulu Xiangjiang river crossing tunnel in Changsha has different types of foundation pits. Proper retaining structures should be selected for these different types of foundation pits so as to avoid accidents during construction and, on the other hand, to minimize the construction cost. In the paper, the selection and design of proper retaining structures for these different types of foundation pits are presented. Conclusions drawn are as follows: 1) For opencut foundation pits under urban roads, especially for foundation pits interfered with concentrated utility lines and buildings, retaining structures consisting of rowed piles (or diaphragm walls) and internal bracing should be adopted so as to control the lateral deformation; 2) For neighboring foundation pits with almost the same depths and some distance in between, tying retaining structures should be adopted; 3) For alignmentcomplex foundation pits with great depth difference and small spacing, retaining structures with common short piles and open cutting should be adopted.

Key words: Xiangjiang river crossing tunnel, foundation pit adjacent to building, shield launching/arriving shaft, retaining structure