粉砂地层泥水盾构刀盘脱困工程实例分析

CASE STUDY OF RELIEVING A SLURRY SHIELD?S CUTTER HEAD FROM BEING TRAPPED IN SILTY SAND LAYERS

杭州粉砂地层中,杭州沿江大道运河隧道工程施工中因泥水盾构刀盘被砂土裹牢受困无法转动而被迫停工。分析该工程盾构刀盘受困的原因,介绍处理措施及其环境影响,在此基础上提出预防泥水盾构刀盘在砂性土层掘进束缚受困的措施。分析表明:泥水盾构刀盘粉砂土地层中束缚受困后,切口正前方地面开槽,通过高压喷射水流冲射刀盘上附着砂土使其离散脱落的措施是安全可行的;开槽时应加强对周围环境的监控,避免开槽引起周围土层和已建成隧道结构的位移过大。泥水盾构在粉砂土层中掘进时,为避免刀盘被砂土束缚而无法转动,应保证泥水循环的通畅连续,确保泥膜质量,并适当提高泥水压力以维持开挖面稳定,提高泥水携带砂土的能力;盾构非掘进状态下,应定时转动刀盘,避免长时间停机、开挖面无泥水循环时砂土塌落沉淀附着刀盘。

During slurry shield tunnelling in silty sands during construction of Hangzhou Canal Tunnel, the cutter head of shield was trapped by sand adhesion. Due to the additional torque imposed by adherent sands, the cutter head stopped to rotate. The reasons for trap of shield＇s cutter head were analyzed, and the measures taken to relieve the cutter head were described. Based on experiences and lessons learned from this case study, measures to avoid trap of slurry shield＇s cutter head by adhesion of sands in silty sands were presented. In order to relieve the trapped cutter head, a pit was excavated at the front ground, and then high-pressure water jetting was used to clear sands adhered to the cutter head. Practice shows that the measures taken in this case were safe and effective for relieving the trapped shield＇s cutter head. Attention should be paid to ensure the safety of surrounding environments, especially the completed tunnel nearby when the pit is excavated. To avoid the cutter head of slurry shield being trapped by sands while tunnelling in silty sands, unobstructed and continuous slurry circulation should be maintained, high-quality slurry should be guaranteed to balance the excavating face, the ability to sweep away sands should be enhanced, and the cutter head should be rotated at set intervals when the shield stops to assemble the segmental linings.