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Abstract Surrounding rock of Anyuan highway tunnel through coal strata is made of carbonaceous shale，coal line and mudstone weak interlayer. The uniaxial compressive strength of the carbonaceous shale specimens are 3.9–4.8 MPa. The geostress measurement is carried out，and the results show that the maximum horizontal principal stress is 8–10 MPa，and the horizontal principal stress is dominant in the area of tunnel. Based on the on-site monitoring and numerical simulation，the characteristics of surrounding rock deformation are analyzed. The reasons for large deformation are summarized as follows：(1) The strength of surrounding rock is low and the rock swells easily；(2) The level of geostress is high as to the low strength of rockmass；(3) Water effect；(4) Improper construction. The mechanism of large deformation is discussed also. The countermeasures are proposed as follows：the tunnel face should be closed quickly after excavation，then the temporary support is set up，long bolts and grouting pipe are used to control the deformation，the arch is replaced after deformation become stable，the spacing of steel arch is reduced，and finally，invert and inner lining are applied timely. According to the measurement results，it is shown that the treatment measures are effective.
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Received: 18 June 2012
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2013, Vol. 32 
