不同充填度结构面抗剪强度尺寸效应试验研究

Experimental study on size effect of shear strength of joints with different infill ratios

针对现有岩体结构面抗剪强度尺寸效应研究较少考虑充填程度差异影响的不足,首先基于渐进扩大法选取平均起伏差和平均起伏角相近的4种连续尺寸天然结构面形貌,并通过3D打印技术制作结构面面板,然后结合类岩石材料配制方法和毫米级充填装置制备5种充填度的充填结构面,最后通过课题组自主研发的大型结构面直剪试验系统开展3种法向应力条件下的室内直剪试验,获得充填结构面的剪切力学与破坏特征,并分析临界充填度和抗剪强度尺寸效应特性。结果表明:随着充填度的增加,结构面剪切破坏模式主要由“岩-岩”剪断破坏逐渐转变为“岩-土界面”滑动破坏,且结构面归一化峰值抗剪强度逐渐减小,直至达到临界充填度时趋于稳定;随着结构面尺寸的增加,临界充填度逐渐增加,变化范围为1.6~2.0;无充填结构面抗剪强度存在较明显的正尺寸效应,而充填结构面抗剪强度尺寸效应较不明显。通过尺寸效应机理分析发现,在不考虑结构面平均起伏角的影响下,平均起伏高度是影响临界充填度和抗剪强度尺寸效应的主要因素。上述研究可为充填结构面抗剪强度尺寸效应模型建立奠定试验基础。

To address the shortcomings of the existing studies on the size effect of shear strength of rock joints,which do not consider the effects of differences in the filling degree.Firstly,four continuous-size natural joint morphologies with the similar average asperity height and average undulation angle are selected based on the progressively magnifying method,and the joint panels are produced by using the 3D printing technology.Secondly,the infilled joints with five infill ratios are prepared by combining the rock-like material preparation method and the millimeter-level filling devices.Finally,using the direct shear test system for large-scale joints independently developed by the anthors-research group,the laboratory direct shear tests under three normal stress conditions are carried out to obtain the shear mechanics and damage characteristics of the infilled joints.The size effects of the critical infill ratio and shear strength are analyzed.The results show that as the infill ratio increases,the shear damage mode of the joint is mainly changed from"rock-rock"shear fracture to"rock-soil interface"sliding damage,and the normalized peak shear strength gradually decreases until it reaches the critical infill ratio and tends to be stable.As the size of the joints increases,the critical infill ratio gradually increases,ranging from 1.6 to 2.0.There is a more obvious positive size effect on the shear strength of the unfilled joints,while the size effects on the shear strength of the infilled joints are not obvious.Through the analysis of the size effect mechanism,without considering the influences of the average undulation angle of the joints,it is found that the average undulation height is the main factor affecting the size effects of the critical infill ratio and shear strength.The above research can lay an experimental foundation for establishing the size effect model for shear strength of the infilled joints.