The Optimal Study Of The Support Structure Of The Underground Works On Weak Rock

Based on diversion tunnel project of QIAOQI hydroelectric station, this thesis gives clear definition and classification of weak rock, and a comprehensive study has been made on the mechanism of weak rock damage. It makes decision on instability state of surrounding rock according to surveying data, and grey model is formed. This model can predict latter displacement of country rock. Deeper analysis is also been conducted on countermeasure and mechanism of weak rock tunnel, and gradation analysis method is applied to select the optimum bracing plan. Main contents and characters of the paper are as follows:(1) It explains definition and classification of weak rock. It gives analysis on geologic and engineering characters of weak rock.(2) It deeper discussion on damage causes of weak rock of the underground works. It also shows the mechanism of the damage.(3) It studies the bracing method and its mechanism of present weak rock underground project. The bracing countermeasure are made from deformation mechanism and engineering practice. Gradation model is used to decide the optimum bracing plan.(4) Based on the APH method, the gradation model is used to decide the optimum bracing plan.