科研之友
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摘要
Research purposes: In the process of pile foundation construction and earth excavation of lateral foundation pit in karst region, the shallow buried box metro tunnel structure has sudden subsidence, especially the deformation joint performed significantly. This paper depends on the displacement monitoring data along the box metro tunnel and on both sides of the deformation joint to analyze the causes of sudden subsidence of tunnel structure, and studies the effect of subsidence control measures including the shallow layer recharge water, deep layer recharge water and grouting reinforcement. Research conclusions:(1) The maximum cumulative settlement of shallow buried box tunnel induced by support pile construction is 3.3 mm, which should be paid attention to in karst area.(2) The sudden settlement of lateral shallow buried box tunnel structure is mainly caused by the exposure of karst cave and the burst of confined karst water in the construction of foundation pit rock-socketed engineering pile.(3) The shallow recharge water can replenish the stratum in a short time, uplift the tunnel and restrain the steep settlement of the tunnel; long-term implementation of deep recharge and pile foundation mud wall protection construction can maintain the underground water level and control the subsidence of side tunnel, but there are problems that deep recharge water may enter the karst cave through karst cracks or aisles and decrease the replenishment efficiency of recharge water.(4) The maximum horizontal displacement of the tunnel under the effective control of "double row pile + steel strand + symmetrical excavation" is 3.0 mm. (5) Vertical and oblique grouting around box tunnel can reinforce and stop water, and the grouting pressure should be controlled in consideration of the sensitivity of deformation joints.(6) The research results can be used as a reference for the lateral foundation pit engineering of shallow buried box tunnel in similar karst areas.
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