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Experimental Study on the Soil Conditioning in EPB Shield Tunnelling in the Shijiazhuang Sandy Soil Stratum
(1 Key Laboratory of Urban Disaster Prevention and Mitigation of Ministry of Education, Beijing University of Technology, Beijing 100124; 2 China Railway No.17 Bureau Group Sixth Engineering Co., Ltd., Fuzhou 350014)
Abstract Sandy soil is a typical mechanical unstable stratum with poor flow behaviors. When an earth pressure balance shield drives in the sandy soil stratum, it is prone to abnormal wear of the cutterhead and cutters, increase of torque and thrust of the cutterhead, failure and collapse of the working face, blow-out and other problems. In regards to this, taking a certain running tunnel section of Phase 2, Shijiazhuang Metro Line 1 as an example, where the earth pressure balance shield driving in the sandy soil stratum, it first conducts lab tests on soil conditioner, slump and mixing, and then applies the test results to the construction site, finally analyzes the construction parameters after soil conditioning. The results show that the performance of the soil conditioner is better when the foam concentration is 6% and the slurry concentration is 16%, meeting the requirements of shield construction; the best soil conditioning option is the slurry injection ratio of 8% and foam injection ratio of 60%, with the slump in the range of 100- 200 mm, as well as small stirring torque and low fluctuation; within a certain range, with the increase of the foam injection ratio, the indices of torque penetration, screw conveyor torque and soil pressure fluctuation in the soil chamber during tunnelling will be reduced, which is conducive to shield construction, but the foam injection should not be excessive.
Abstract：
Sandy soil is a typical mechanical unstable stratum with poor flow behaviors. When an earth pressure balance shield drives in the sandy soil stratum, it is prone to abnormal wear of the cutterhead and cutters, increase of torque and thrust of the cutterhead, failure and collapse of the working face, blow-out and other problems. In regards to this, taking a certain running tunnel section of Phase 2, Shijiazhuang Metro Line 1 as an example, where the earth pressure balance shield driving in the sandy soil stratum, it first conducts lab tests on soil conditioner, slump and mixing, and then applies the test results to the construction site, finally analyzes the construction parameters after soil conditioning. The results show that the performance of the soil conditioner is better when the foam concentration is 6% and the slurry concentration is 16%, meeting the requirements of shield construction; the best soil conditioning option is the slurry injection ratio of 8% and foam injection ratio of 60%, with the slump in the range of 100- 200 mm, as well as small stirring torque and low fluctuation; within a certain range, with the increase of the foam injection ratio, the indices of torque penetration, screw conveyor torque and soil pressure fluctuation in the soil chamber during tunnelling will be reduced, which is conducive to shield construction, but the foam injection should not be excessive.
WANG Leilei1 YIN Lijun1 GONG Qiuming1 LI Rui2 WU Fan1 BAN Chao1
.Experimental Study on the Soil Conditioning in EPB Shield Tunnelling in the Shijiazhuang Sandy Soil Stratum[J] MODERN TUNNELLING TECHNOLOGY, 2021,V58(3): 182-189
2021, Vol. 58 