剪胀对地下工程岩体位移的影响——以加拿大Donkin-Morien隧道为例

根据建立的岩石剪胀角模型,分析岩石峰值内摩擦角和剪胀角的关系,得出岩石在零围压时的峰值剪胀角小于并近似等于峰值内摩擦角,并假设岩石和岩体的剪胀角遵循相似的变化趋势,结合Hoek-Brown强度准则和GSI岩体分级系统,实现剪胀角模型从完整岩石到岩体的转化。采用程序语言在FLAC3D中编写岩体剪胀角模型程序模块。以加拿大Donkin-Morien隧道为工程实例,研究围压和塑性剪切应变依赖的岩体剪胀对隧道渐进开挖过程中围岩位移的影响,论证恒定的剪胀角值不能准确表达隧道开挖边界附近的岩体位移,而考虑围压和塑性剪切应变为影响因素的岩体剪胀角模型能够合理描述围岩的位移分布,模拟结果与实际测量值具有很好的一致性。研究成果可为岩体非线性力学行为的研究和地下工程岩体的稳定性控制提供理论和实践基础。

INFLUENCE OF DILATION ON ROCK MASS DISPLACEMENT AROUND UNDERGROUND EXCAVATIONS-A CASE STUDY OF DONKIN-MORIEN TUNNEL IN CANADA

Based on the established rock dilation angle model considering both confining pressure and plastic shear strain from previous study by authors，the relationship between peak internal friction angle( ) and dilation angle( ) for different rocks is established. Based on the conclusion of  ＜  and  at the zero confining pressure from theoretical analysis and experimental observations，an important assumption is made，i.e. the dilation behavior of a rock mass resembles that of the intact rock. The rock dilation angle model is generalized for rock mass using Hoek-Brown criterion and GSI system；and subsequently the proposed rock mass dilation angle model is implemented in FLAC3D using VC++ language. Utilizing extensometer data from Donkin-Morien tunnel project in Canada，the dilation angle model is verified by investigating the ground deformation near the excavation boundary. It is demonstrated that constant dilation angle values can not capture the displacement distributions near the excavation boundary satisfactorily. However，when the confining pressure and plastic shear strain dependent rock mass dilation are considered，the predicted rock mass displacements induced by gradual excavation are in good agreement with the field measurement results. This model provides a reasonable means to consider dilation during rock mass failure near the excavation boundary.