{"title":"Leeb hardness test as a tool for joint wall compressive strength (JCS) evaluation","authors":"A.G. Corkum, B. Jeans, D. Mas Ivars","doi":"10.1016/j.enggeo.2024.107851","DOIUrl":null,"url":null,"abstract":"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 (<ce:italic>JRC</ce:italic>), such as the use of laser scanning; however, the equally important Joint Wall Compressive Strength (<ce:italic>JCS</ce:italic>) parameter has not been significantly advanced. The <ce:italic>JRC</ce:italic> and <ce:italic>JCS</ce:italic> 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 <ce:italic>JCS</ce:italic> determination that offers increased accuracy relative to current methods. The LH test value (<mml:math altimg=\"si5.svg\"><mml:msub><mml:mi>L</mml:mi><mml:mi>D</mml:mi></mml:msub></mml:math>) correlation to Unconfined Compressive Strength (<mml:math altimg=\"si1.svg\"><mml:msub><mml:mi>σ</mml:mi><mml:mi>c</mml:mi></mml:msub></mml:math>) is proposed for <ce:italic>JCS</ce:italic> determination. In addition, this study investigates the <ce:italic>Influence Zone</ce:italic> 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 <mml:math altimg=\"si5.svg\"><mml:msub><mml:mi>L</mml:mi><mml:mi>D</mml:mi></mml:msub></mml:math> reading due to underlying material of contrasting hardness. In addition, a collection of natural rock specimens with variable joint wall hardness were collected and <mml:math altimg=\"si5.svg\"><mml:msub><mml:mi>L</mml:mi><mml:mi>D</mml:mi></mml:msub></mml:math> 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 <ce:italic>JCS</ce:italic> and a proposed methodology was presented.","PeriodicalId":11567,"journal":{"name":"Engineering Geology","volume":"43 1","pages":""},"PeriodicalIF":6.9000,"publicationDate":"2024-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Engineering Geology","FirstCategoryId":"89","ListUrlMain":"https://doi.org/10.1016/j.enggeo.2024.107851","RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"ENGINEERING, GEOLOGICAL","Score":null,"Total":0}
引用次数: 0
Abstract
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.
期刊介绍:
Engineering Geology, an international interdisciplinary journal, serves as a bridge between earth sciences and engineering, focusing on geological and geotechnical engineering. It welcomes studies with relevance to engineering, environmental concerns, and safety, catering to engineering geologists with backgrounds in geology or civil/mining engineering. Topics include applied geomorphology, structural geology, geophysics, geochemistry, environmental geology, hydrogeology, land use planning, natural hazards, remote sensing, soil and rock mechanics, and applied geotechnical engineering. The journal provides a platform for research at the intersection of geology and engineering disciplines.