等值地应力下岩质圆形隧道位移释放系数比较及应用

 隧道前期变形是利用收敛约束法确定支护压力和围岩稳定变形的关键，在分析隧道开挖面空间效应机制的基础上，总结具有代表性的深埋岩质圆形隧道位移释放系数公式，对其进行分类、适用性及空间效应的比较，得到不同位移释放系数、不同支护施作距离和不同控制目标下的收敛约束差异。研究结果表明：以围岩塑性区最大半径为基础的位移释放系数对弹性围岩和各种弹塑性围岩均适用，具有广泛的工程应用前景；弹性位移释放系数仅适用于弹性围岩，常用塑性位移释放系数仅适用于相对半径为2的隧道围岩；不宜将依据距开挖面较远处得到的支护压力而设计的支护结构随意前移构筑，应依据实际工程的围岩特性，合理选择位移释放系数公式，适时施作不同刚度的支护。

COMPARISONS AND APPLICATIONS OF DISPLACEMENT RELEASE COEFFICIENTS FOR A CIRCULAR ROCK TUNNEL SUBJECTED TO ISOTROPIC GEOSTRESSES

The deformation of tunnel at early stage is of critical importance to determine the support pressure and stable deformation of rock mass using the convergence-confinement method. Some typical formulae of displacement release coefficient for deep circular rock tunnels were summarized，classified and compared in terms of the applicability and the spatial effect of tunnel face. The differences from the convergence-confinement analysis due to the different coefficients of displacement release，different positions of support installing and different control objectives were discussed. It was found that the coefficient of displacement release dependent on the ultimate plastic radius of rock mass was applicable to both the elastic and the elasto-plastic rocks and therefore had wide prospects of engineering applications. The coefficients of elastic displacement release were found to be only applicable to the elastic rock，while the commonly used coefficients of plastic displacement release were only suitable for the rock tunnel with a normalized radius of 2. The support designed according to the support pressure distant from the tunnel face could not be moved forward arbitrarily and a reasonable and timely support with different stiffness should be designed according to the properties of rock mass.