Surface settlements caused by shield construction of gas-bearing soils based on column hole shrinkage theory

Relying on the actual project of Hangzhou Metro Tangqing Line shield crossing the gas-bearing stratum, the column hole shrinkage theory is modified, and the formula for calculating the surface settlement caused by the construction of the shield structure of the gas-bearing stratum based on the column hole shrinkage theory is proposed for the first time, and the influences of burial depth of tunnel, excavation radius, matrix suction on the surface settlement caused by the construction of the shield of the gas-bearing stratum are analyzed based on the actual engineering parameters. The results show that the calculated results of the column hole shrinkage theory are in good agreement with the measured data, which can better reflect the surface settlement characteristics caused by shield excavation in gas-bearing strata. Different from that in saturated soils, when the double-line shield passes through the gas-bearing stratum, the surface settlement caused by the leading line is greater. The matrix suction in unsaturated soils such as gas-bearing soils affects the soil characteristics by changing the friction angle and cohesion in the soil, but compared with that of the cohesion of the soil, the change of friction angle of the soil has a greater impact on the surface settlement caused by the shield crossing the gas-bearing strata.