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Abstract This paper presents the in-situ test results on the basis of the previous research. The in-situ tests showed that the deformation，the stress change and the microcrack initiation occurred in the the rock mass at didtance of 1.2 times of the diameter of diversion tunnel ahead of the excavation front，and the stress changed greatly in the rock mass 2–10 m behind tunnel front. The data of acoustic emission indicated that the rock mass in the range from 5 m ahead of the tunnel frount to 10 m behind the tunnel front produced the most acoustic emission energy during tunnelling and the acoustic emission was largely stable when the tunnel front was 10 m ahead of the acoustic emission monitoring section. The results of the optical fiber Bragg grating monitoring indicated that some closed cracks the rock mass close to the wall with serious excavation damage and subcritical crack growth reopened or further propagated even when the tunnel face effect disappeared. The most serious excavation damage occurred on the right spandrel and the damage zone was about 3 m in depth. The results from the multipoint displacement meter monitoring showed that the deformation of surrounding rock during tunnel excavation was not siginificant. The monitoring of deep tunnelling should therefore mainly focused on the measurement of excavation damage zone，stress in the rock bolts，stress in rocks，optical fiber Bragg grating and acoustic emission measurement and supplemented with a small number of multi-point displacement meters.
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Received: 28 May 2013
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2014, Vol. 33 
