基于广义Hoek-Brown准则的隧道纵向变形曲线研究

A study of the longitudinal deformation of tunnels based on the generalized Hoek-Brown failure criterion

纵向变形曲线是隧道开挖面空间约束效应的直观反映,多数纵向变形曲线的研究并未考虑围岩质量和应力水平的影响。基于广义Hoek-Brown准则,采用有限差分法,提出了能够量化不同围岩质量及应力水平下开挖面空间效应差异的纵向变形曲线函数表达式,可以简便地得到不同地质条件下的隧道纵向变形曲线,通过误差分析及与已有研究成果对比,验证了该方法的合理性与普适性。研究结果表明:围岩基本质量指标值相同时,围岩纵向变形曲线随着埋深增加变得更加平缓,即围岩应力及位移的释放过程越缓慢,埋深相同时,随着围岩基本质量指标值的降低,围岩纵向变形曲线显示出同样的趋势,相对于开挖面前方,开挖面后方纵向变形曲线的这种特点更加明显;开挖面处纵向变形也是围岩质量与应力水平的函数,最大值不超过隧道径向变形最终值的30%。

The longitudinal deformation profile（LDP） can reflect the spatial effect of excavation face in tunneling. Most of the previous studies on LDP, however, ignore the influence of surrounding rock quality and stress level. Based on the Hoek-Brown failure criterion and the finite difference method, functions of LDP which can quantify the difference of spatial excavation effect are given. LDP with various surrounding rock qualities and stress levels can be calculated by using these functions. By means of an error analysis, and by comparing with other equations, the rationality and universality of the proposed method are shown. The results indicate that, when basic quality indices（BQ） of rock masses have the same value, LDP tends to become flatten as the tunnel depth increases, implying that the relaxation process of stress and displacement is slowing down. When tunnel depths are the same, LDP also tends to become flatten as the BQ decrease. These features of LDP behind the excavation face are even more salient compared to that at the front of the excavation surface. The longitudinal deformation at the excavation face depends also upon the surrounding rock quality and the stress level, and its maximum value is not more than 30% of the final longitudinal deformation.