泥水平衡盾构开挖面失稳特征模拟试验研究

Simulation Test Study on Instability Characteristics of Slurry Balance Shield Excavation Face

为研究泥水平衡盾构施工过程中开挖面的失稳过程与特征,使用泥水盾构模型装置,通过室内试验模拟泥水盾构开挖面的掘进失稳过程,分析地层水土应力变化规律,总结了不同水位下泥水盾构在砂土地层中开挖面主动失稳的破坏形式。研究结果表明:盾构刀盘前方土压力、超孔隙水压随着支护力减小先缓慢下降后加速下降并保持稳定,此时开挖面失稳破坏;在无水头压力的情况下泥水盾构开挖面主动破坏后上部地层可保持稳定,在有水头压力的情况下破坏区不断向上发展,并延伸至地表;泥水盾构施工过程中产生的超孔隙水压会抵消一部分泥水压力,使泥浆产生的有效支护力降低。

In order to study the instability process and characteristics of the excavation surface during the construction of slurry balance shield,a slurry shield model device was used to simulate the excavation instability process of slurry shield excavation surface through laboratory tests. The variation law of formation water and soil stress was analyzed,and the failure forms of active instability of slurry shield excavation surface in sandy soil layer under different water levels were summarized. The results show that the earth pressure and excess pore water pressure in front of the shield cutterhead decrease slowly at first,then accelerate and maintain stability with the decrease of support force. At this time,the excavation surface is unstable and damaged. Under the condition of no head pressure,the upper stratum can remain stable after the active failure of the excavation surface of slurry shield. Under the condition of water head pressure,the failure area continues to develop upward and extends to the surface. The excess pore water pressure generated during the construction of slurry shield will offset part of the slurry pressure and reduce the effective support force generated by slurry.