RESEARCH ON ACCUMULATIVE DAMAGE EFFECT OF INTERLAID ROCK IN DAMAOSHAN TUNNEL GROUP WITH SMALL CLEAR DISTANCE
LIU Minggui1，ZHANG Guohua1，LIU Shaobo1，LI Qi2
(1. State Key Laboratory of Geomechanics and Geotechnical Engineering，Institute of Rock and Soil Mechanics，Chinese Academy of Sciences，Wuhan，Hubei 430071，China；2. Wuhan RSM Intelligence Geotechnique Co.，Ltd.，Wuhan，Hubei 430071，China)
Abstract：The blasting construction of small clear distance tunnel inevitably causes accumulative damage of surrounding rocks and its mechanical behaviors will be degenerated. Based on dynamic damage variable and internal displacement of surrounding rock，combining with the monitoring results of Damaoshan tunnel，accumulative damage effects of interlaid rock in tunnel groups with small clear distance are studied. Monitoring results of acoustic velocity and internal displacement show that the newly-built blasting construction has caused damage，breakage and slippage of inter-space rock to a certain degree. However，the internal displacement does not cause instability，and surrounding rocks still possess certain strength. By comparing newly-built tunnel with existing tunnel，damage range caused by construction using two side-wall pilot tunnel method is three times more than the range caused by using whole section excavation. Therefore，accumulative damage effect should be brought to high attention during the construction of small clear distance tunnel. Blasting in upper section will lead to activation of the fissures of rock and significant declines of acoustic velocity；and blasting in lower section will lead to vibration of inter-space rock as wall vibration and significant increase of internal displacement，which causes loosing and slippage of rock mass. The slippage will stop till the blasting stops. Both the changing rate of the acoustic velocity and the displacement should be taken fully consideration in the analysis of the accumulative damage range and degree. If only the changing rate of the acoustic velocity is considered，the analytical results will not be correct. The farther the explosion source is，the bigger the damage degree and the displacement of the surrounding rocks are. The accumulative damage effect has distinct nonlinear characteristics.
刘明贵，张国华，刘绍波，李祺. 大帽山小净距隧道群中夹岩累计损伤效应研究[J]. 岩石力学与工程学报, 2009, 28(07): 1363-1369.
LIU Minggui1，ZHANG Guohua1，LIU Shaobo1，LI Qi2. RESEARCH ON ACCUMULATIVE DAMAGE EFFECT OF INTERLAID ROCK IN DAMAOSHAN TUNNEL GROUP WITH SMALL CLEAR DISTANCE. , 2009, 28(07): 1363-1369.
