基于强度分层计算的弱胶结软岩冻结壁变形分析

 弱胶结软岩具有低强度、低冻胀性和高流变性的特点。以平均温度代替冻结温度场径向温度梯度分布以及以冻结壁平均强度参数代替力学参数径向层状分布的传统计算方法不能准确反映弱胶结软岩冻结壁的变形特性。基于幂律蠕变本构模型推导分层计算模型的有限差分形式，并给出分层计算模型在FLAC3D中的实现途径。通过实例计算表明，分层计算结果与实测数据更吻合。根据不同工况下的模拟结果，分析弱胶结软岩冻结凿井井帮最大径向位移点为(0.36～0.42) h，空帮径向变形对掘砌段高较敏感，随着段高的增加，围岩变形显著增加，且沿纵向冻结围岩深部发展。通过容许空帮时间分析，在段高大于4.5 m时，正常冻结凿井作业循环时间内，不能保证工作面施工安全。

FROZEN WALL DEFORMATION ANALYSIS IN WEAKLY CEMENTED SOFT ROCK BASED ON LAYERED CALCULATION OF STRENGTH

The weakly cemented soft rock has the characteristics of low strength，low frost heaving ratio and high theology effect. Traditional calculation method which substitutes average temperature for radial temperature gradient distribution of the frozen temperature field and substitutes average strength parameters for mechanical parameters radial hierarchical distribution can not reflect the deformation characteristic of the frozen wall in weakly cemented soft rock. The finite difference equation of layer model is given based on the model of power law constitutive relationship；and the implementation method of layer calculation model in FLAC3D is also given. The example analysis indicates that the results of layered calculation model are good agreement with the measured data. Based on the calculation result analysis in different working cases，the maximal displacement point of shaft wall in weakly cemented soft rock freeze sinking shaft is in the ranges of 0.36 h to 0.42 h. The h is the section height. The radial displacement of the free shaft wall is sensitive to the height of digging. With the increment of section height，surrounding rock deformation increases remarkably，and extends to deep freezing surrounding rock. An analysis of admissible free rib time shows that working face construction safety could not be assured during the normal shaft sinking time when the section height is more than 4.5 m.