类矩形盾构穿越既有隧道引起土体沉降的模型试验研究

Model tests on soil settlement caused by quasi-rectangular shield passing through adjacent existing tunnels

类矩形盾构邻近既有隧道施工的土体变形控制是今后隧道工程要面对的难题,但目前该方面的研究较少。通过开展室内缩尺寸模型试验模拟类矩形盾构邻近既有隧道施工,探究了新旧隧道不同间距以及正交、斜交、重叠、夹穿等工况下由于土体损失导致的地表和深层土体纵向变形情况;对Peck公式进行了拓展,将无既有隧道沉降值与既有隧道造成土体二次扰动沉降值叠加得到适用于类矩形盾构穿越既有隧道的地表沉降计算方法。研究结果表明:随着新建隧道的施工,地表沉降逐渐增大,最后趋于稳定;地表沉降与深层土体沉降趋势基本一致,深层土体沉降值大于地表沉降;相比正交、斜交工况,重叠工况对地表沉降影响最大,其最大沉降值比其余2组最大沉降值大1倍;斜交工况与正交工况地表沉降最大值基本相同,但斜交工况沉降槽形状为W形,正交为V形,斜交工况沉降槽宽度大于正交工况,说明对土体的影响范围更大;重叠工况由于隧道自重造成的地表沉降的效果远比遮拦效应大;对比并择优了能够计算类矩形盾构施工造成的沉降槽宽度的方法,理论计算结果与实测数据基本吻合;Peck公式适用于既有隧道造成土体二次扰动的地表沉降计算。

The soil deformation control in rectangular shield construction adjacent to existing tunnels is a challenge for future tunnelling projects. However, there is less research in this field at present. Through the indoor reduced size model tests to simulate the construction of quasi-rectangular shield adjacent to the existing tunnel,the longitudinal deformation of surface and deep soil caused by soil loss under different spacing between old and new tunnels and orthogonal, skew, overlapping and pinch through conditions were explored. The Peck formula was extended. The surface settlement calculation method suitable for quasi rectangular shield tunneling through existing tunnels was obtained by superimposing the settlement value without existing tunnels and the settlement value of secondary disturbance of soil caused by existing tunnels. The results show that with the construction of new tunnels, the surface settlement gradually increases and finally tends to be stable. The trend of surface settlement is basically consistent with that of deep soil, and the settlement value of deep soil is greater than that of surface settlement. Compared with orthogonal and skew working conditions, the overlapping working condition has the greatest impact on surface settlement, and the maximum settlement value is twice as large as that of the other two groups. The maximum value of surface settlement under skew condition is basically the same as that under orthogonal condition. However the settlement shape is W-shaped for the skew condition and V-shaped for the orthogonal condition. The width of settlement tank under skew condition is greater than that under orthogonal condition, indicating that it has a greater impact on the soil. The effect of surface settlement caused by the selfweight of the tunnel under overlapping conditions is much greater than the blocking effect. The methods that can calculate the width of settlement trough caused by similar rectangular shield construction aree compared and optimized, and the theoretical calculation results are basically consistent with the measured data. The Peck formula is applicable to the surface settlement calculation of soil secondary disturbance caused by existing tunnel.