Investigations of the sequential excavation and reinforcement of an underground cavern complex using the discontinuous deformation analysis method

摘要

Two modifications are made to enable the use of the discontinuous deformation analysis (DDA) method to investigate the sequential construction of an underground cavern complex. One modification is the "block birth and death" approach. With the aid of a boundary block searching algorithm, this approach excavates the blocks in any closed domain step by step and is verified by a DDA example. The other modification is an updating algorithm of the rock bolt called the dull-reactivating method. In this new algorithm, the coordinates of the ending endpoints of the dull rock bolts are regularly updated and the corresponding rock bolts in the sequential reinforcement region are reactivated. The initial geostress field and the sequential construction of the underground cavern complex of the Dagangshan hydropower station in Southwest China are simulated with the modified DDA method. Valuable results are obtained by analysing the displacement, stress and rock bolt force. In the construction processes, the blocks around each cavern form a bearing capacity system to prevent the block deformation, and the rock bolts jointly support the stress release as a system. At the sidewalls of the main machine building and the downstream side wall of the tail surge chamber, the blocks cut by joints with a high dip angle suffer a strong stress release, and the tension forces of the several rock bolts are so large that they should be noticed, which provides a basis for the construction guidance of the project. (C) 2015 Elsevier Ltd. All rights reserved.