基于流-固耦合的盾构隧道开挖面稳定性研究

Numerical Study of Working Face Stability of Shield Tunnel Based on Fluid-Solid Coupling Effect

利用FLAC3D建立三维数值模型,对考虑完全流-固耦合效应的盾构隧道开挖面失稳过程进行模拟和验证,并进一步分析水位高度、渗流时间对开挖面变形、地表沉降和孔隙水压力的影响。研究表明:开挖面变形随支护压力比的减小经历3个阶段的变化,且与土体塑性区的发展密切相关;相比于无水状态,考虑流-固耦合效应的开挖面稳定性显著降低,随水位的升高、渗流时间的增大,开挖面发生失稳破坏的支护压力比明显增大;支护压力比(表征支护压力)的减小将导致开挖面前方一定范围的孔隙水压力减小,靠近开挖面的孔隙水压力受扰动程度加剧,形成"漏斗状"的影响区;开挖面失稳导致土体位移场延伸至地表,引起地表产生明显的沉降变形,在不同的变形阶段开挖面中心点位移与最大地表沉降分别呈抛物线相关和线性相关。

A 3 D numerical model is established by FLAC3 D based on fluid-solid coupling effect,so as to simulate and verify the process of instability of tunneling face; moreover,the influences of water level and seepage time on tunneling face deformation,ground settlement and pore pressure are discussed. The study results show that: 1) The developing process of tunneling face deformation can be divided into 3 stages relating with expansion of soil plastic zone. 2)Compared to the case without hydraulic pressure,the stability of tunneling face accounting for fluid-solid coupling effect is significantly reduced; with the increase of water level and seepage time,the limiting supporting pressure to maintain stability increases gradually. 3) The support pressure is characterized by support pressure ratio; the reduction of the supporting pressure would induce the decrease of pore pressure at the front of tunneling face; the pore pressure near tunneling face is affected much more,which features funnel-shaped influence zone. 4) When collapse occurs to tunneling face,the significant settlements and soil displacement field of the ground would extend to ground level; and the horizontal displacement at the center of tunneling face correlates with the maximum ground settlement,showing parabolic correlation and linear correlation at different stages.