One of the most common basic structural assemblages includes joints and pressure solution seams (PSS). These are described under structure assemblages. Zhou and Aydin (2012) used the configuration in Figure 1 which is based on localized volume reduction structure (LVRS) of Katsman et al. (2006) to investigate the formations of the common structural assemblages of joints and pressure solution seams: orthogonal PSS sets, orthogonal PSS-Vein sets, and parallel PSS-Vein sets.

Figure 1. Geometric configuration of a basic mechanical model of an elliptical LVRS with an aspect ratio of a/b subjected to remote stress (designated by superscript r) parallel (x-direction) and perpendicular (y-direction) to it. Epsilon is the initial plastic strain (designated by superscript p) and E and v are Young's modulus and Poisson's ratio, respectively, with I used for the PSS inclusion and m for the surrounding rock matrix. Also shown are the dimensionless form of the function used to evaluate the influence of various geometric, stress, volumetric strain, and elastic moduli on the formation of various assemblages. Zhou and Aydin (2012).

As summarized in a table (Figure 2) various remote stresses, internal plastic strains, stiffness ratios, and geometries of LVRSs are considered. It is found that when PSSs have perfect elliptical shapes and smooth flanks, the conditions for generating fundamental assemblages are highly restrictive. However, there are a wide variety of loading and geometric factors favoring the formation of a specific type of structural assemblage. Among these are: (1) PSSs with roughness on their flanks and PSSs with overall irregular geometry are much more favorable for generating fundamental structural assemblages; (2) higher ratios of remote stresses are favorable for orthogonal PSSs; and (3) higher internal plastic strains enhance parallel PSS and vein formation.

Figure 2. Table summarizing the major influence of various factors, remote loading, initial plastic strain within the structure, geometry of the PSS, ratio of Young's modulus inside the structure and the rock matrix in favoring the formation of certain structure assemblages, including orthogonal PSSs, orthogonal PSS and vein, and parallel PSS and vein. Zhou and Aydin (2012).

Other assemblages such as fault and joint assemblages and deformation band and joint assemblages are described under 'Splay Joints' and 'Splay Pressure Solution Seams.'