金华山软岩铁路隧道施工过程围岩屈服接近度分析

YIELD APPROACH INDEX ANALYSIS OF SOFT AND WEAK ROCK MASS SURROUNDING JINHUASHAN RAILWAY TUNNEL DURING CONSTRUCTION

隧道施工过程中围岩处于复杂应力状态下,隧道围岩屈服区演化特征的确定对于围岩稳定性分析和开挖支护方案优化具有重要的意义。采用屈服接近度指标衡量围岩破坏接近程度可以合理地描述复杂应力状态下围岩的应力危险性,对Mohr-Coulomb类岩体材料的屈服接近度函数进行了相应的推导,并在非线性有限元用户子程序上编程予以实现。介绍了赣州-龙岩铁路DKl33＋095～DKl38＋237段软弱围岩单线隧道正台阶步施工方案以及湿喷纤维混凝土支护方案。为了对该隧道施工过程中隧道围岩屈服区的演化特征进行合理评价,采用非线性有限元法对软弱围岩条件下的铁路隧道施工过程进行了数值模拟,分析了施工过程中隧道围岩屈服接近度分布特征,判定了隧道台阶步施工过程中隧道围岩的稳定性。分析结果表明：该隧道施工过程中围岩破坏区主要发生在下台阶步施工过程中;屈服接近度指标比传统的塑性区分布提供的信息更加丰富,有利于工程技术人员定量地评价隧道开挖支护方案。

The tunnel rock mass has a complex stress state. It is important for tunnel rock mass stability analysis that the rock mass failure region distribution during construction is evaluated appropriately. The yield approach index is proposed in the paper to evaluate the rock mass failure extent, which is suitable for the rock mass stress failure probability under complex stress state. The Mohr - Coulomb type rockmass material is used in the paper to deduce corresponding calculation equations for yield approach index. The numerical method for the calculation of yield approach index is implemented in nonlinear finite element software user subroutine. In the Ganzhou - Longyan mongline railway tunnel construction process between DK133 ＋095 and DK138 ＋ 237, the wet- sprayed fiber reinforced concrete lining structure is used as the first stage lining structural and the step tunnel excavation lining construction process is used. To evaluate the tunnel rock mass failure zone evolution during tunnel construction, the nonlinear finite element analysis with consideration of rock mass yield approach index is performed for the railway tunnel first stage lining construction process using the wet - sprayed fiber reinforced concrete lining structure. The rock mass failure index evolution during construction process is analyzed and the tunnel rock mass stability is determined during step tunnel excavation lining construction process. The numerical result shows that the rock mass fail- ure zone mainly exists during the bottom step construction process. The yield approach index for rock mass failure estimation provides more information than that of common rock mass plastic zone distribution. This index is useful for the engineers to evaluate the tunnel excavation and lining plan quantitatively.