大直径越江盾构隧道各向异性渗流应力耦合分析

ANALYSIS OF COUPLED ANISOTROPIC SEEPAGE AND STRESS OF LARGE DIAMETER RIVER-CROSSING SHIELD TUNNEL

上海长江隧道的直径和一次连续掘进距离迄今均为世界之最。隧道平均覆土9.0 m,最浅覆土仅6.8 m。为控制高水头下浅覆土中特大径盾构推进时管片的上浮,采用单液同步注浆工艺。用能够考虑土体渗透系数随应力状态变化的弹塑性各向异性渗流应力耦合模型,对上海越江隧道东线江中段的施工过程进行数值分析。结合实测数据,揭示盾构推进时管片上浮量和管片外侧孔隙水压力的变化规律,研究变形稳定后管片外侧及拱顶正上方各点孔隙水压力的分布状况,分析不同水深时地下水渗流对地表沉降和管片受力的影响。研究结果表明,目前采用的单液同步注浆材料及工艺能很好控制管片的上浮,管片变形稳定时壁后各点孔隙水压力与静水压力比值随深度增加而增大,水的作用使管片受力趋于均匀,但应注意高水位引起的高孔隙水压力对管片受力带来的消极影响。

Shanghai Yangtze Tunnel is the largest diameter and longest once-driving distance shield tunnel in the world until now. The average covering soil is 9.0 m, and the shallowest covering soil is only 6.8 m. In order to control the floating of segment during large diameter shield driving under high water head and shallow covering soil, a single-liquid synchronous grouting process is adopted. The construction process of Shanghai Yangtze Tunnel east line river-crossing part is numerically simulated with a 3D elastoplastic coupled anisotropic seepage and stress model which could consider the soil permeability varying with volumetric strain. Combining with the measured data, the change laws of tunnel segment＇s rising displacement and the pore water pressure outside the segment during tunnelling are revealed; and the pore water pressure distribution outside the segments and above the crown when the deformation has been stable are studied. Moreover the influences of groundwater seepage on surface settlement and segment internal forces under different water depths are analyzed. The results show that the current single-liquid synchronous grouting material and technology can effectively control the floating of segment; the ratio of pore water pressure outside the segment to hydrostatic pressure increases with the depth when the segment deformation has been stable： and the action of groundwater improves the segment＇s forced state; but the negative impaction of high pore water pressure caused by the high water level on the segment force should be paid more attention to.