EFFECTS OF EXCAVATION SUBSEQUENCE OF BUSBARS TUNNEL ON DISPLACEMENT OF SURROUNDING ROCK MASS
HUANG Qiuxiang1，DENG Jianhui2，3，SU Pengyun4
(1. State Key Laboratory of Geohazard Prevention and Geoenvironment Protection，Chengdu University of Technology，Chengdu，Sichuan 610059，China；2. State Key Laboratory of Hydraulics and Mountain River Engineering，Sichuan University，Chengdu，Sichuan 610065，China；3. College of Water Resource and Hydropower，Sichuan University，Chengdu，Sichuan 610065，China；4. HydroChina Chengdu Engineering Corporation，Chengdu，Sichuan 610072，China)
Abstract：Generally，there are two different schemes about the excavation subsequence of main powerhouse and tunnels that intersect with it at intersecting section. One is that the part of main powerhouse is excavated first，and then the part of tunnel is excavated from side wall of main powerhouse，which is called first side wall then tunnel. While the other is on the contrary，that means the tunnel is excavated first then the part of main powerhouse is excavated from the tunnel，which is called first tunnel then side wall. With Pubugou hydropower station underground powerhouse and the Xiluodu hydropower station underground powerhouse as background，taking main powerhouse as object of study，the effect of the bus tunnel construction sequence use the scheme of first tunnel then side wall or first side wall then tunnel on surrounding rock displacement is analyzed based on monitoring data and by means of numerical simulation. Firstly，with the help of monitoring results，the displacement of surrounding rock mass of top arch，rock anchor beam，upstream side wall，as well as downstream side wall were compared part by part；then by using numerical calculation，in which main factors considered were ground stress and rock types，rock type of II or III，ground stress in high，medium，as well as low level，busbars tunnel was excavated by using the scheme of first tunnel then side wall or first side wall then tunnel，that means 12 different conditions were simulated. The research results from comprehensive analysis of monitoring results and numerical simulation results show that，the effect of bus tunnel construction sequence on surrounding rock displacement is mainly concentrated in the place of anchor beam layer and above parts，especially at layer of rock anchor beam in the downstream. From point of control surrounding rock displacement，in condition of low stress，the influence of excavation subsequence is not obvious，while in the condition of medium and high stress the opinion that tunnels are excavated first is preference. As cavern that intersect with main powerhouse and main transformer house，its excavation subsequence is rational or not has dual significance on schedule control and surrounding rock stability. Therefore，effects of excavation subsequence of busbars tunnel under different geological conditions is a subject being worthy of further investigation.
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2013, Vol. 32 
