岩石–混凝土界面峰值剪切强度经验公式试验研究

Experimental study on empirical formula of peak shear strength for rockconcrete interface

为研究岩石-混凝土界面剪切承载能力与岩石和混凝土力学特性的关系,采用劈裂法制取细砂岩、粉晶大理岩、花岗岩和粗晶大理岩非规则节理试样,使用三维形貌扫描仪获取岩石节理形貌参数后,在岩石节理表面浇筑混凝土制成岩石-混凝土界面试样。采用RDS-200岩石节理剪切试验系统,开展不同法向应力下岩石-混凝土界面直剪试验。结果表明:整体上岩石-混凝土界面和混凝土节理峰值剪切强度都随法向应力增大而增大,同一法向应力下前者增大速率始终大于后者;界面峰值剪切强度平均值与界面峰前剪切刚度平均值具有较好的指数关系;随着岩石与混凝土弹性模量之差的增大,岩石-混凝土界面内摩擦角呈线性降低趋势,界面黏聚力呈线性增加趋势,岩石-混凝土界面峰值剪切承载方式由以摩擦承载方式为主逐渐转变为摩擦和黏结共同承载方式,由此提出了符合莫尔-库仑准则形式的岩石-混凝土界面峰值剪切强度经验公式;基于岩石-混凝土界面压缩强度中混凝土壁面分担系数与岩石节理基本摩擦角的幂函数关系,提出新的岩石-混凝土界面压缩强度JCSab的确定方法,建立符合JRC-JCS模型形式的界面峰值剪切强度经验公式。通过岩石-混凝土界面峰值剪切强度计算值与试验值的对比验证,发现提出的2个经验公式能够较好地预测岩石-混凝土界面峰值剪切强度,且参数易于获取,可为工程实践中岩石-混凝土界面峰值剪切强度的估计提供参考。

In order to study the relationship between the shear bearing capacity of the rock-concrete interface and the mechanical properties of rock and concrete,the irregular joint specimens of fine-grained sandstone,silty-grained marble,granite and coarse-grained marble were prepared by using a splitting method,the rock joint morphological parameters were obtained by a three-dimensional topography scanner,and then the rock-concrete interface specimens were made by pouring concrete on the rock joint surface.Finally,direct shear tests were carried out on rock-concrete interface specimens under different normal stresses by using the RDS-200 rock joint shear test system.The results show that the peak shear strength of rock-concrete interface and concrete joint increases with the increase in normal stress,and the former always increases faster than the latter under the same normal stress;the average peak shear strength of the rock-concrete interface has a good exponential correlation with the average prepeak shear stiffness of rock-concrete interface.With the increase of the difference between the elastic modulus of rock and concrete,the internal friction angle of the rock-concrete interface decreases linearly,the cohesion of the rock-concrete interface increases linearly,and the peak shear bearing mode of the rock-concrete interface gradually changes from the friction bearing mode to the combined bearing mode of friction and cohesion.Therefore,an empirical formula of the peak shear strength of the rock-concrete interface in the form of Mohr-Coulomb criterion is proposed.Based on the power relationship between the concrete wall sharing coefficient in the rock-concrete interface compressive strength and the basic friction angle of rock joint,a new method for determining the rockconcrete interface compressive strength JCSab is proposed,and an empirical formula of peak shear strength of rockconcrete interface in the form of JRC-JCS model is established.Through the comparison and verification between the calculated values and the test values of the peak shear strength of the rock-concrete interface,it is found that the two newly proposed empirical formulas can better predict the peak shear strength of the rock-concrete interface,and the parameters are easy to obtain,which can provide a reference for the estimation of the peak shear strength of the rock-concrete interface in engineering practice.