考虑接触特征的节理峰值剪胀角新模型

A contact characteristics-considered new model of peak dilatancy angle of rock joint

节理形貌是峰值抗剪强度的重要影响因素。基于接触理论,考虑压剪作用下节理的接触特性,且剪切时受到的阻力只是一小部分较陡的区域提供的,提出了一个新的粗糙度指标。新指标以三角形微元面积为权重,计算有效接触区域内的平均视倾角θ_(ef)(σ_(n))。基于三种不同形貌的扫描试验和15组节理直剪试验,由经验拟合公式A(σ_(n))=4.7σ_(n)/(σ_(c)σ_(t))计算得到的有效接触平均视倾角θ_(ef)(σ_(n))可以很好地与峰值剪胀角联系起来,与峰值剪胀角试验值相比发现相对误差为14.3%。新模型综合考虑了节理的接触特征与剪切特征,且数学形式物理意义明确,更容易理解,同时具有较好的预测精度,为进一步研究节理抗剪强度模型提供了参考。

Rock joint morphology is an important factor affecting the peak shear strength of the joint.Based on contact theory,a new roughness index is proposed herein under the consideration of the contact characteristics of joint under compressive shear effect and the consideration that the resistance suffered during shearing is only from a small part of steeper area.For the new index,the area of the triangle infinitesimal element is taken as the weight to calculate the mean apparent dip angleθ_(ef)(σ_(n))within the effective contact area.In accordance with the scanning test of three different morphologies and the direct shear test of a total of 15 sets of joint specimens,the effective contact mean apparent dip angleθ_(ef)(σ_(n))obtained from the calculation made through the empirical fitting formula A(σ_(n))=4.7σ_(n)/(σ_(c)σ_(t))can be better related to the peak dilatancy angle,while the relative error is 14.3%if compared with the experimental value of the peak dilatancy angle.The contact and shear characteristics of rock joint are comprehensively considered by the new model with clear physical meaning of mathematical form,thus the model is more prone to be understood and has a better prediction accuracy as well,which can provide a reference for the further study to be made on the rock joint shear strength model.