裂隙的剪胀特性及其演化规律对于认识裂隙岩体的变形特性、水–力耦合特性和锚固机制具有重要意义。尽管裂隙剪胀与其塑性变形、法向应力及尺寸效应之间的关系已得到初步揭示,但对裂隙剪胀的发挥过程和演化规律还缺乏深入的研究。以往的研究多采用介于0°~20°的常剪胀角模型或峰值内摩擦角剪胀模型描述裂隙的剪胀特性,但这些模型既可能低估较小剪切位移条件下的剪胀变形,又可能高估较大剪切变形条件下的剪胀变形。采用N.Barton建立的峰值剪胀角公式和负指数形式的滑动剪胀角模型,较好地描述硬质裂隙的峰后剪胀特性及其演化规律。该模型得到一系列室内剪切试验成果的验证,可为裂隙岩体的变形特性、渗透特性和锚固机制研究提供借鉴。
The dilatancy and its evolution of fractures under normal and shear loads are essential to understanding deformation behavior,coupled hydromechanical behavior and anchorage mechanism of fractured rock masses. Although the dependencies of joint dilatancy on plasticity,normal stress and scale effect have been demonstrated in the literature,the evolution of dilatancy remains an open issue for rock fractures. Existing studies commonly adopted a constant dilatancy angle between 0° and 20° or the internal friction angle to characterize the dilatancy behavior. As a result,the normal deformation of rock fractures induced by dilatancy may either be underestimated at small shear displacements,or be overestimated at relatively large ones. The post-peak dilatancy behavior and its evolution are better modeled by the formulae for peak dilatancy angles of rock fractures proposed by N. Barton and a mobilized dilatancy evolution model in negative exponential form. The proposed model have been validated by a number of existing laboratory shear tests;and it may provide a useful expression for investigating the deformation,seepage flow and reinforcement behaviors of jointed rock masses.