QIN Jing 1, LU Wei 1, ZHU Jun-chen 2

1. Engineering Design and Research Center, IWHR, Beijing 100044, China
2. CNNC Sanmen Nuclear Power CO., Sanmen 317112, China

Abstract: The circulating water pump house foundation pit is ultra-deep with the deepest point of 32.3m and is located in a special area where bedrock is shallowly buried and mud and backfill layers in the upper level are deep, so the support requirement for foundation pit is much higher. According to the stratigraphy distribution, three types of side slope of deep foundation pit were divided: complete bedrock, shallowly buried bedrock without sludge layer and deeply buried bedrock with big depth of sludge layer. Three supporting methods were respectively applicated: step-slope excavation for bedrock, piles in row and prestressed anchor cables, and the combination of piles in row and cement-soil wall and prestressed anchor cables, which effectively solved the difficult problem in coastal soft soil region with the higher ground water level, lower c and φ, easier instability of side of foundation pit due to the great horizontal load. The results of typical section analysis show that the maximum tension of prestressed anchor is 361.84kN, the maximum horizontal displacements is 19.26mm, and the maximum positive and negative bending moment value is 711.36kN·m and -787.52kN·m, which meet the standard and design requirements.

Key words: circulating water pump house, ultra-deep foundation pits, supporting design

Published in: Journal of China Institute of Water Resources and Hydropower Research (Vol. 11 No. 2, 2013)