Abstract：
The 10 220 m long Xianghe tunnel, which is classified as one with grade I risk on the railway from Guangtong to Dali, has a parallel adit excavated at the right side of tunnel. During construction severe deformations were usually encountered, especially at the sections of intrusive rock, granite porphyry, diabase, fault breccias and carbonaceous shale since the tunnel passed through nine faults and the lithology changed frequently, rock mass were found to be broken and soft. In this paper, such countermeasures as advance geological forecast, inner contour adjustment from straight wall to curved wall, advance support, ground water drainage, increasing of rock mass strength, primary support and clear spacing between parallel adit and main tunnel were put forward based on analyzing of geological characteristics and influential factors of rock mass deformation, and safe driving of parallel adit in soft rock mass is guaranteed.
2016, Vol. 53 