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扬州瘦西湖隧道采用泥水盾构穿越全断面硬塑性黏土地层,施工停机后多次出现地表塌陷事故。利用室内试验研究硬塑性黏土浸水条件下的崩解、软化特性,结合现场实测数据分析该工程地表塌陷的原因,进一步讨论此类破坏发生的过程,据此提出泥水盾构在全断面硬塑性黏土地层施工时地表塌陷的预防措施。研究表明:泥水盾构停机使开挖面硬塑性黏土在泥水浸润下发生崩解、软化,使开挖面上方形成局部孔洞;随着时间延长,局部孔洞逐渐向上发展直至地表,最终形成地面局部塌陷。泥水盾构在硬塑性黏土地层施工时,应当避免停机;当必须停机时,应尽量缩短停机时间,避开建筑地段,同时加强地面监测,必要时应在开挖面上方地层进行注浆加固,防止坍塌破坏。
The Slender West Lake Tunnel in Yangzhou adopts muddy water shields to cross the hard plastic clay strata in the entire cross-section, resulting in many surface subsidence accidents after construction shutdown. The disintegration and softening properties of hard plastic clay under water immersion were studied by laboratory tests. The causes of surface collapse of the project were analyzed based on field measurements. The process of such failure was further discussed. Preventive measures of surface subsidence during formation construction. The research shows that the mud shield tunneling causes the hard plastic clay in the excavation surface to disintegrate and soften under the condition of muddy water infiltration, forming local holes above the excavation surface; as time goes on, the local holes gradually develop up to the surface and finally form the ground part Collapse. Slurry shield in the hard plastic clay strata should be avoided when downtime; when it is necessary to shut down, should minimize downtime, to avoid the construction lot, while strengthening the ground monitoring, if necessary, should be grouting reinforcement above the excavation surface strata, Prevent collapse damage.