Joint (geology)

Summary

A joint is a break (fracture) of natural origin in a layer or body of rock that lacks visible or measurable movement parallel to the surface (plane) of the fracture ("Mode 1" Fracture). Although joints can occur singly, they most frequently appear as joint sets and systems. A joint set is a family of parallel, evenly spaced joints that can be identified through mapping and analysis of their orientations, spacing, and physical properties. A joint system consists of two or more intersecting joint sets. The distinction between joints and faults hinges on the terms visible or measurable, a difference that depends on the scale of observation. Faults differ from joints in that they exhibit visible or measurable lateral movement between the opposite surfaces of the fracture ("Mode 2" and "Mode 3" Fractures). Thus a joint may be created by either strict movement of a rock layer or body perpendicular to the

Official source

https://en.wikipedia.org/wiki/Joint_(geology)

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A Numerical Study on Wave Transmission Across Multiple Intersecting Joint Sets in Rock Masses with UDEC

Jian Zhao, Jianbo Zhu

This paper presents a numerical study on wave transmission across jointed rock masses with UDEC, where multiple intersecting joint sets exist. The capability of UDEC of studying wave transmission across rock joints is validated through comparison with analytical solutions and experimental data. Through parametric studies on wave transmission across jointed rock masses, it is found that joint mechanical and spatial parameters including joint normal and shear stiffnesses, nondimensional joint spacing, joint spacing ratio, joint intersecting angle, incident angle, and number of joint sets together determine the wave transmission. And for P wave incidence, compared with other parameters, joint normal stiffness, nondimensional joint spacing, and joint intersecting angle have more significant effects on wave transmission. The physical reasons lying behind those phenomena are explained in detail. Engineering applications and indications of the modeling results are also mentioned.

Springer Verlag2013

Discontinuities in rock masses greatly influence stress wave transmission. Before performing numerical modeling on complicated cases, benchmarking modeling must be performed first to validate the numerical code through comparison with theoretical solutions or experiment results. The accuracy of numerical results generally increases with decreasing mesh size. However, with an extremely fine mesh size, substantial computational time will be consumed. 3D plane wave propagation across a single joint or a joint set can be treated equivalently to a corresponding 2D case, as shown both analytically and numerically. However, it should be noted that when the incident wave is not a plane wave or there are unparallel joints and joint sets, a 3D case cannot be equivalent to a 2D case.

Springer Vienna2012

Analytical study of S-wave propagation across saturated joints in rock masses

Gaofeng Zhao, Jianbo Zhu

Joints are important mechanical and hydrological features of rock masses, and they can greatly affect wave propagation and attenuation across jointed rock masses. Joints often contain liquid, and the presence of liquid will change the mechanical behaviors of the joint. The saturated joint can be modeled as nonwelded interfaces. Stresses across the joint are continuous, but particle displacements and velocities are not In this paper, with the recently introduced concept of Virtual Wave Source (VWS) and analytical solution of reflection and transmission coefficients for harmonic plane S-wave across one saturated joint, normally incident S-wave propagation across one saturated joint set is studied. Parametric studies of S-wave propagation across one saturated joint set are performed. It is found that the magnitude of transmission coefficient across one saturated joint set is controlled by normalized shear joint stiffness, normalized joint viscosity, number of joints and nondimensional joint spacing. In addition, the waveforms of transmitted waves are discussed in detail in order to explain the phenomena above.

Crc Press-Taylor & Francis Group, 6000 Broken Sound Parkway Nw, Ste 300, Boca Raton, Fl 33487-2742 Usa2010