土压平衡盾构不满舱掘进开挖面渗透破坏试验研究

Study on Seepage Failure of Excavation Face of EPB Shield Tunneling with Non-Full Chamber

为进一步提高土压平衡盾构掘进效率,常采用非满舱掘进模式进行隧道施工。而富水地层中非满舱掘进常常遇到开挖面失稳引起超挖量大等问题,针对非满舱掘进过程中开挖面渗透稳定的问题,结合济南地铁R2线某标段发生的开挖面失稳现象开展研究。首先,通过自制开挖面渗透破坏试验装置研究了渗流条件下非满舱掘进开挖面渗透破坏的条件以及类型。然后,分析了不同渗透破坏类型的出砂规律。最后,按照土体可移动细颗粒含量设置了6种不同级配的地层,探究土体级配与临界水力梯度的关系。研究结果表明:1)渗流作用下,在该地层会发生渗透破坏,其非发展型和发展型渗透破坏发生的临界水力梯度分别为0.5和0.8;2)非发展型渗透破坏出砂质量先增大后逐渐平稳,而发展型渗透破坏的出砂质量持续增大,成渐进破坏的特点;3)建立了可移动填料含量Pf与其临界水力梯度的关系式。

In order to improve the efficiency of EPB shield tunneling,non-full chamber tunneling mode is often used in tunnel construction.While the non-full chamber tunneling mode in water-rich strata often encounters problems such as large over-excavation due to instability of excavation face.Aiming at the seepage stability of excavation face during nonfull chamber tunneling,the study is carried out combined with an instability phenomenon of excavation surface at a bid section of Jinan metro line R2.First,the self-made excavation surface seepage failure test apparatus are used to study the seepage failure conditions and types under seepage condition and non-full chamber tunneling.Second,the sand production rules for different seepage failure types are analysed.Last,six types of strata with different gradation are set according to the content of movable fine particles in soil,and the relationship between soil gradations and critical hydraulic gradient is investigated.The results show that:(1)Seepage failure occurs in the formation under the action of seepage,and the critical hydraulic gradients of seepage failure for non-development type and development type are 0.5 and 0.8 respectively.(2)The sand quality of non-development seepage failure increases first and then becomes stable gradually,while the sand quality of development seepage failure continues to increase,which is characterized by gradual failure.(3)The relation between movable filling content Pf and its critical hydraulic gradient is established.