盾构隧道开挖过程中土的应力路径试验研究

Test Study on the Stress Path of Soil during Shield Tunnelling

相比于填方工程,隧道开挖过程中土的应力路径具有明显的特殊性。针对这一问题,文章采用模型试验的方法,在一个长2000 mm、宽1000 mm、高1500 mm的模型箱中开展盾构开挖模型试验,通过埋设在隧道周围不同位置处的三维土压力盒,测得开挖引起的土体应力状态的变化规律。试验结果表明:隧道开挖过程中,拱顶处的平均正应力逐渐减小,且主应力方向发生突变;拱肩处的应力路径随塌陷范围的扩大发生转折;在拱腰和拱底处,应力路径分别接近于等平均正应力路径和常规三轴压缩路径;在预测隧道开挖引起的地层沉降时,应当选取合适的本构模型以考虑复杂应力路径的影响。

Compared with the filling engineering,tunnel excavation will cause apparently special stress paths in the soil.In response to this problem,scholars at home and abroad have done a lot of work using theoretical analysis and numerical simulation methods,but little study of model test has been carried out.A shield excavation model test is performed in a model box with 2000 mm long,1000 mm wide and 1500 mm high.Through the three-dimensional earth pressure boxes that are buried at different positions around the tunnel,variation of the soil stress state induced by the excavation is measured.Test results show that the mean normal stress at the arch top increases gradually while the principal stress direction changes abruptly.At the arch shoulder,a sudden turn appears to the stress path with the expansion of the collapse range.Besides,the stress paths at the arch waist and the arch bottom are close to the constant mean stress path and the conventional triaxial compression path,respectively.Therefore,when the tunnelling-induced ground settlement is predicted,an appropriate constitutive model should be chosen to consider the effect of the above complex stress paths.