隧道施工引起的松砂土层与地表结构响应

Responses of loose sand ground and surface structure caused by tunnel construction

通过4组离心试验,模拟相对深度(埋深-直径比)分别为1.3和2.0的隧道在砂质土层中施工,分析了土层与地表建筑的位移与变形规律;通过抽取模型隧道内部的液体模拟隧道施工导致的土层体积损失,并设计了2层铝制框架结构模型,利用粒子图像测速技术测量了隧道施工引起的土层与结构移动数据,分析了地表与建筑筏板基础的水平与垂直位移、深部土层的移动与剪切变形、框架结构剪切变形与分类,以及结构剪切变形的修正系数与相对抗剪刚度。研究结果表明:隧道相对深度从1.3增加到2.0时地表沉降槽宽度从3.4 m增加到5.6 m,地表建筑的最大沉降从32.3 mm增加到49.5 mm,但变形程度有所降低;隧道施工影响下地表框架结构的变形主要表现为剪切变形,弯曲变形所占比重可以忽略不计;隧道施工引起松砂土层发生收缩变形,导致地表土层体积损失率始终大于隧道体积损失率,且隧道越深,差异越大;较浅隧道试验中建筑筏板基础与土层间存在较大间隙(27 mm),而较深隧道间隙几乎为0,从而增大了建筑筏板基础对地表土体水平移动的约束范围;建筑的剪切变形修正系数随隧道体积损失率的增加逐渐降低,且浅隧道的变化速率更大;2种隧道相对深度的建筑剪切变形修正系数-相对抗剪刚度数据点均位于已有经验包络线的内部,表明该修正系数也适用于较深隧道。

Four centrifuge tests were performed to simulate the construction of tunnels with the relative depths(burial depth-diameter ratio)of 1.3 and 2.0 in the sand ground,and the migration and deformation laws of soil layers and ground buildings were analyzed.The ground volume loss caused by tunnel construction was modelled by extracting the liquid from the model tunnel,and a two-storey aluminum frame structure model was designed.The movement data of the strata and structure caused by tunnel construction were measured by particle image velocimetry(PIV),and the horizontal and vertical displacements of the surface and building raft foundation,the movement and shear deformation of the deep ground,the shear deformation and classification of the frame structure,as well as the shear deformation modification factor of the building and relative shear stiffness were analyzed.Research results show that the surface settlement trough width increases from 3.4 m to 5.6 m when tunnel relative depth increases from 1.3 to 2.0,and the maximum settlement of ground building increases from 32.3 mm to 49.5 mm,but the deformation degree decreases.The deformation of ground frame structure due to tunnel construction mainly exhibits shear deformation,and the proportion of bending deformation is negligible.The contractive deformation of loose sand soil due to tunnel construction leads to the fact that the volume loss of surface ground is always greater than the tunnel,and a deeper tunnel indicates a greater difference.A large gap(27 mm)exists between the building raft foundation and the ground in the shallow tunnel test,whereas no gap forms in the deep tunnel test,thereby increasing the constraint of the building raft foundation on the horizontal movement of the surface soil.The building shear deformation modification factor decreases gradually with the increase in tunnel volume loss,and the change rate of shallow tunnel is greater.The data of building shear deformation modification factor-relative shear stiffness for the two relative tunnel depths are within the existing empirical envelopes,indicating that the shear deformation modification factor is also applicable to the deep tunnel.