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Soil conditioning tests on sandy soil for earth pressure balance shield tunneling and field applications
Highlights The selected anionic-nonionic foam agent has higher foam expansion rate (FER) and half-life time (H-T) values than that of the anionic foam agent. The effect of polymer on foaming properties and the specific characteristics of polymer-foam-conditioned soil are investigated. The polymer has the most obvious effect on reducing the permeability of the sandy soil compared with foam and bentonite slurry. Gas loading was used to simulate the pressure environment of the shield soil bin instead of Jack pressure loading in rotational torque tests.
Abstract When performing earth pressure balance (EPB) shield tunneling in a sandy stratum, spewing and incomplete soil discharge often occur. Soil conditioning agents are needed to modify the excavated soil so that it has flow plasticity. Conditioned sandy soil and conditioning agents from Nanchang Metro Line 4 were evaluated using laboratory and performance tests. The results show that the foam expansion rate (FER) and half-life time (H-T) increase with increasing foam agent concentration (cf) up to a critical concentration of 5%. A high molecular weight polymer inhibits the FER and H-T of the foam. However, when the VR (the volume ratio of the polymer and foam agent) exceeds 0.3, the polymer increases the viscosity of the foam agent solution, which reduces the foam drainage rate and increases the foam stability. The reduction of the soil permeability by the polymer is the most obvious effect. When FIR = 40%, VR = 0.1 and SIR = 30%, the conditioned sand undergoes an appropriate state with good flow plasticity, with relatively low rotational torque and SD because the agglomeration effect of the polymer improves the homogeneity of the sandy soil. The engineering application of this soil conditioning scheme, which was based on laboratory test results, ensured the smooth completion of the tunnel.
Soil conditioning tests on sandy soil for earth pressure balance shield tunneling and field applications
Highlights The selected anionic-nonionic foam agent has higher foam expansion rate (FER) and half-life time (H-T) values than that of the anionic foam agent. The effect of polymer on foaming properties and the specific characteristics of polymer-foam-conditioned soil are investigated. The polymer has the most obvious effect on reducing the permeability of the sandy soil compared with foam and bentonite slurry. Gas loading was used to simulate the pressure environment of the shield soil bin instead of Jack pressure loading in rotational torque tests.
Abstract When performing earth pressure balance (EPB) shield tunneling in a sandy stratum, spewing and incomplete soil discharge often occur. Soil conditioning agents are needed to modify the excavated soil so that it has flow plasticity. Conditioned sandy soil and conditioning agents from Nanchang Metro Line 4 were evaluated using laboratory and performance tests. The results show that the foam expansion rate (FER) and half-life time (H-T) increase with increasing foam agent concentration (cf) up to a critical concentration of 5%. A high molecular weight polymer inhibits the FER and H-T of the foam. However, when the VR (the volume ratio of the polymer and foam agent) exceeds 0.3, the polymer increases the viscosity of the foam agent solution, which reduces the foam drainage rate and increases the foam stability. The reduction of the soil permeability by the polymer is the most obvious effect. When FIR = 40%, VR = 0.1 and SIR = 30%, the conditioned sand undergoes an appropriate state with good flow plasticity, with relatively low rotational torque and SD because the agglomeration effect of the polymer improves the homogeneity of the sandy soil. The engineering application of this soil conditioning scheme, which was based on laboratory test results, ensured the smooth completion of the tunnel.
Soil conditioning tests on sandy soil for earth pressure balance shield tunneling and field applications
Li, Shuchen (author) / Wan, Zeen (author) / Zhao, Shisen (author) / Ma, Pengfei (author) / Wang, Manling (author) / Xiong, Bin (author)
2021-11-10
Article (Journal)
Electronic Resource
English
Soil Conditioning Tests on Sandy and Cobbly Soil for Shield Tunneling
| Springer Verlag | 2021