Abstract:

Large deformation is inevitable during the construction of tunnels in soft ground with high ground stress. It is of great necessity to perform dedicated studies and tests so as to select reasonable reinforcement measures and to effectively bring the deformation under control. During the construction of Dazhangou inclined shaft of Muzhailing tunnel, 9 trial sections are established on basis of the site conditions so as to investigate on the deformation control technology. The test indicates that the combination of stress resistance and stress releasing should be adopted to control the large deformation in soft ground with high ground stress. As the cover of the inclined shaft increases, the ground stress increases. Therefore, the strength and rigidity of the primary reinforcement structures should be increased, otherwise collapse may occur. The secondary lining of the inclined shaft can effectively bring the deformation under control. The pilot tunnel and the superlong largediameter horizontal boreholes installed are favourable to the releasing of the high ground stress.

Key words: inclined shaft, high ground stress, large deformation of soft ground, pilot tunnel, stress releasing by drilling large diameter boreholes