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Abstract 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.
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Received: 15 April 2010
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2010, Vol. 29 
