隧道开挖引起砂性地层变形及破坏的模型试验研究

Model Test on Deformation and Failure of Sand Stratum Caused by Shield Tunnel Excavation

为更好利用城市地下空间,修建地铁解决地表交通问题成为趋势,但在砂性地层中修建隧道易发生塌方事故。本文通过模型试验,对砂性地层中隧道开挖引起的地层变形、地表沉降及土体应力变化规律进行研究,分析了地层损失率、砂土粒径及隧道埋深对地表沉降及地层变形的影响。结果表明:隧道开挖引起地层沉降曲线基本符合Peck曲线,验证了本试验的可行性。(1)随着地层深度增加,最大沉降值提高,沉降槽宽度减小;洞周0.75 D范围内土体应力变化明显。(2)地层损失率越大,地表沉降值及沉降槽宽度系数越大,且地层损失率到达一定值后,洞周1.0 D范围内地层沉降明显;(3)砂土粒径越小,地表沉降越大,沉降槽宽度系数越小,当砂土粒径比大于10倍时,地层变形扰动范围小;(4)隧道埋深越小,地表沉降越大,沉降槽宽度越小,且地层扰动范围也从拱腰处缩小至拱肩处。

In order to make better use of urban underground space,the construction of subway to solve the problem of surface traffic congestion has become a trend,but the construction of tunnels in sand stratum is prone to collapse accidents.Based on the model test,the ground deformation,surface settlement and soil stress variation law caused by tunnel excavation in sand stratum are studied,and the influence of ground loss ratio,sand particle size and tunnel cover depth on surface settlement and ground deformation is analyzed.The results show that the settlement curve due to tunnel excavation basically conforms to Peck curve.With the ground depth increasing,the maximum settlement value increases,and the width of settlement trough decreases.The soil stress changes obviously in the range of 0.75 D around the tunnel.The larger the ground loss ratio is,the larger the surface settlement value and the width coefficient of settlement trough are.When the ground loss ratio reaches a certain value,the ground deformation is obvious in the 1.0 D area around the tunnel.The smaller the sand particle size is,the larger the surface settlement is,and the smaller the width coefficient of settlement trough is.When the sand particle size ratio is more than 10 times,the disturbance range of formation deformation is small.The smaller the depth of the tunnel is,the larger the surface settlement is and the smaller the width of the settlement trough is.As the depth of tunnel decreases,the range of stratum disturbance decreases from the hance to the spandrel.