水下砂卵石地层盾构隧道越江段注浆压力研究

近年来,江(海)底盾构隧道建设日益增多,对于水下段而言,由于地层渗透性强、埋深浅等因素影响,盾尾同步注浆压力的合理控制显得尤其重要,而探明盾构隧道在施工过程中孔隙水压力的分布对工程实践意义重大。本文依托常德沅江过江隧道工程,结合工程现场地形、地质、气候以及水文条件,采用FLAC^3D有限元分析软件对盾构施工扰动下的地层孔隙水压力分布进行系统分析。研究结果表明:(1)综合考虑各种因素确定渗流场中削减边界为20 m,即模型构建时沿开挖方向前后多取20 m长度,可使模拟结果更能真实反映越江隧道围岩各处孔隙水压力的变化规律;(2)盾构隧道掘进过程中,拱顶、拱底和左右拱腰处的动水压随掘进距离的变化趋势大致相同,拱底动水压量值最大,左右拱腰次之,拱顶最小,并根据区间动水压力变化规律给出满足岸边段和水下段要求的注浆压力。

Study on Grouting Pressure of Cross-river Section of Shield Tunnel in Underwater Sandy Cobble Ground

In recent years,the construction of shield tunnels at the bottom of the river(sea)is increasing.For the underwater section,due to the influence of strong permeability and shallow depth of the formation,the reasonable control of the simultaneous grouting pressure of the shield tail is particularly important.The distribution of pore water pressure during the construction of the shield tunnel has important significance for engineering practice.Based on the Changde Yuanjiang River Crossing Tunnel Project,combined with the site topography,geology,climate and hydrological conditions,FLAC^3D finite element analysis software was used to systematically analyze the pore water pressure distribution under the disturbance of shield construction.The results show that:(1)comprehensively considering various factors to determine the cut boundary of the seepage field is 20 m,so each numerical simulation model will build a length of 20 m along the excavation direction,and the simulation results will more accurately reflect the change rule of pore water pressure around the surrounding rock of the cross-river tunnel.(2)During the tunneling process of the shield tunnel,the dynamic trend of the moving water raft at the vault,the arch bottom and the left and right arch waists is about the same as that of the tunneling distance,and the maximum value of the dynamic water at the arch bottom is the largest,followed by the left and right arch waists,and the vault is the smallest.In addition,the slurry pressure that meets the grouting requirements of the shore and underwater sections is given according to the variation law of the dynamic water pressure in the interval.