盾构法隧道推进引起周围土体的附加应力分析

Additional stress of surrounding soil caused by propelling of shield tunneling

基于弹性力学Mindlin解,推导了盾构推进时正面推力、盾构与土体间的摩擦力引起的周围土体附加应力沿圆周方向的计算表达式,并运用Gauss-Legendre公式,结合庆春路过江隧道工程进行了数值分析,得到了周围土体附加应力沿圆周方向的分布规律,可以为盾构推进控制及壁后注浆提供参考。通过分析得出:土体中附加应力关于90°/270°轴,即隧道轴线严格对称;σx在90°与270°位置即圆周顶与底达到最大值,且顶部值比底部略大;在腰部偏下位置达到最小值;σy最大值分别在90°与270°位置,即圆周顶与底,且顶部值比底部更大,最小值分别在0°与180°位置,即圆周腰部,整个图形呈眼镜形;σz最大值分别在圆周腰部略偏上位置,最小值分别在90°与270°位置,即圆周顶与底,整个图形呈"8"形;摩阻力引起的土体附加应力的分布规律类似于正面推力引起的土体附加应力的分布规律,但其值远大于正面推力引起的土体附加应力,因此不可忽略摩阻力的影响。

The formula for additional stress of surrounding soil versus angle is deduced based on the Mindlin solution,which is induced by bulkhead pressure and friction force during the propelling of shield tunneling.The distribution rules of additional stress versus angle are obtained by analyzing of the data from the Qingchun Road River-Crossing Tunnel Project using the Gauss-Legendre formula.The conclusions can be references for the control of shield tunneling and grouting.The distribution rules are as follows： the additional stress is strictly symmetric to the tunnel axis or 90°/270° axis;the maximum values of σx and σy are both obtained when the angels are 90° and 270° or at the positions of the top and bottom of the circle,and the value from the top is larger than that from the bottom;the minimum value of σx is obtained at the position of the lower-waist of the circle,but the minimum of σy is obtained when the angels are 0°and 180° or at the waist of the circle;the graphic of σy is glasses type;the maximum value of σz is obtained at the position of the higher-waist of the circle,and the minimum one is obtained when the angels are at 90° and 270° or at the positions of the top and bottom of the circle,and the graphic is ＂8＂ type;and the distribution rules of the additional stress induced by the friction is similar to that induced by the positive push,but the value of the former is much larger than that of the latter.So,the influences of the friction cannot be ignorable.