The Barton-Bandis model for the nonlinear shear strength of rock joints is the most commonly used strength criterion in rock engineering practice. There have been advancements in determination of Joint Roughness Coefficient (JRC), such as the use of laser scanning; however, the equally important Joint Wall Compressive Strength (JCS) parameter has not been significantly advanced. The JRC and JCS are effectively linked, to some extent. A sensitive rebound hardness index test, the Leeb Hardness (LH) test, was investigated to provide a quantifiable and repeatable method of JCS determination that offers increased accuracy relative to current methods. The LH test value (LD) correlation to Unconfined Compressive Strength (σc) is proposed for JCS determination. In addition, this study investigates the Influence Zone of the LH test on surfaces with graded hardness profiles (e.g., weathered surfaces). This was done using a series of artificial composite plaster-rock specimens of known hardness to provide insight into the influence effects on the surface LD reading due to underlying material of contrasting hardness. In addition, a collection of natural rock specimens with variable joint wall hardness were collected and LD profiles were obtained by sequential surface grinding and testing. These natural rock specimens included those with wall surface materials softer and harder relative to the underlying intact rock. A Hardness Contrast Type was proposed for classification of hardness contrast conditions. The study findings showed the LH test is a suitable tool for predicting JCS and a proposed methodology was presented.

中文翻译：

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里氏硬度测试作为节理壁抗压强度 （JCS） 评估的工具


岩石节理非线性剪切强度的 Barton-Bandis 模型是岩石工程实践中最常用的强度准则。在确定关节粗糙度系数 （JRC） 方面已经取得了进展，例如使用激光扫描;然而，同样重要的接缝壁抗压强度 （JCS） 参数并没有得到显著的提升。在某种程度上，JRC 和 JCS 实际上是相互联系的。研究了一种灵敏的回弹硬度指数测试，即里氏硬度 （LH） 测试，以提供一种可量化且可重复的 JCS 测定方法，相对于当前方法，该方法具有更高的准确性。提出了 LH 测试值 （LD） 与无侧限抗压强度 （σc） 的相关性用于 JCS 测定。此外，本研究还调查了 LH 测试对硬度梯度分布的表面（例如，风化表面）的影响区。这是使用一系列已知硬度的人造复合石膏岩石标本完成的，以深入了解由于对比硬度的底层材料对表面 LD 读数的影响。此外，收集了一组具有可变节理壁硬度的天然岩石试件，并通过顺序表面研磨和测试获得了 LD 轮廓。这些天然岩石标本包括那些壁表材料相对于下面的完整岩石更软和更硬的标本。提出了一种 Hardness Contrast Type 用于硬度对比条件的分类。研究结果表明，LH 测试是预测 JCS 的合适工具，并提出了一种建议的方法。