The formation of orthogonal joint systems and cuboidal blocks:New insights gained from flat-lying limestone beds in the region of Havre-Saint-Pierre(Quebec,Canada)
作者机构：Département des Génies CivilGéologique et des MinesÉcole Polytechnique de MontréalMontréalQuébecH3C 3A7Canada Department of GeologyLakehead UniversityThunder BayOntarioP7B 5E1Canada
出 版 物：《Journal of Rock Mechanics and Geotechnical Engineering》 (岩石力学与岩土工程学报（英文版）)
年 卷 期：2023年第15卷第12期
页 面：3079-3093页
核心收录：
学科分类：08[工学] 080104[工学-工程力学] 0815[工学-水利工程] 0801[工学-力学（可授工学、理学学位）]
主 题：Plato's cuboids Orthogonal joints Fracture spacing Limestone Layered rock mechanics Appalachian geology
摘 要：Vertical orthogonal joints are a common feature in shallow crustal *** are several competing theories for their formation despite the *** examined the exceptional exposures of orthogonal joints in flat-lying Ordovician limestone beds from the Havre-Saint-Pierre Region in Quebec,Canada(north shore of Saint-Lawrence River)to test conceptual models of joint formation in a natural *** the region,the spacing of cross-joints is consistently larger than the spacing of systematic joints by a factor of 1.5 *** joint-spacing-to-bed-thickness ratios(s/t)are much larger in these beds(s/t=4.3 for systematic joints,and 6.4 for cross-joints)than those in higher strained strata along the south shore of the Saint-Lawrence River(s/t=1),highlighting the effect of tectonic strain in decreasing fracture spacing and block *** high values of s/t indicate that cross-joint formation was unlikely caused by a switch from compression to tension once a critical s/t ratio for systematic joints was reached(as hypothesized in previous studies).We proposed a new model for the formation of orthogonal joint systems where the principal stress axes locally switch during the formation of systematic *** presence of ladder-shaped orthogonal joints suggests a state of effective stress withσ_(1)^(∗)≫0σ_(2)^(∗)σ_(3)^(∗)and whereσ_(2)^(∗)-σ_(3)^(∗)is within the range of fracture strength variability at the time of *** research provides a new mechanical model for the formation of orthogonal joint systems and cuboidal blocks.
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