Abstract
To study the disturbance characteristics of double-line shield tunnel excavation on sand bodies in grouting-reinforced water-rich sand stratum, a similar model test was carried out. Firstly, the physical parameters and strength indexes of the overlying soil strata of the tunnel in the water-rich sand stratum were determined by laboratory tests. The similar soil and tunnel support structures of each stratum were prepared. Then, considering the different seepage modes of upper and lower soil strata under the influence range of tunnel excavation, the model test of double-line shield tunnel excavation in a grouting-reinforced water-rich sand stratum is conducted. The variation rules of sand deformation, surface settlement, and sand body stress during the excavation of a double-line shield tunnel are analyzed utilizing monitoring and analyzing systems such as a flowmeter, micro earth pressure sensors, and dial indicators. It is found that during the excavation of the double-line tunnel, the self-stabilization ability of the grouting reinforced sand bodies is strong under the action of stable seepage. Under the influence of grouting reinforcement, the seepage path around the tunnel structure will change, the fluid-solid coupling effect will decrease, and the sand stratum will be uplifted to varying degrees. The sand body will change its mechanical properties due to the influence of seepage. The fluid-solid interaction effect will be enhanced. The fluid-solid coupling effect of soil particles and water will be further enhanced when the excavation of the subsequent tunnel is carried out. The effect of unsaturated seepage in the overlying soil stratum leads to greater stress at the arch waist of the arch tunnel. In the actual construction process, the grouting amount and grouting time should be strictly controlled. The tunnel basement is supported by anchor spray support to prevent the tunnel structure and surface uplift.
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