A characteristic feature of the "solid" rock is that it has an inhomogeneous structure and is divided up Into separate structural elements of various orders in which the rocks differ tndenslty, strength, and deformability.Inhomogeneity in rocks is due to various geological-tectonic causes, including stratification, folding, large fractures with zones of influence, and regions of increased jointlng. These factors give rise to the primary lnhomogeneity; near exposures this Is supplemented by zones of lithification (compaction and cementation), weathering, load relief, and deconsolidation. The thickness of the zones of deconsolidation varies from the first few meters near mine workings to several tens of hundreds of meters in the sides of quarry slopes and bases. The rocks in these zones have increased Dinting, marked water permeability, low strength, and low modulus of elasticity.The inhomogeneity of the mechanical properties of the rock causes a complex stress distribution in It. In the solid rock there are centers of concentration and regions of low stress; their distribution is governed by the stiffness of the neighboring blocks. Ifinsucha rock, acted on, say, by a uniform compressive load, we distinguish some region, then the stress distrtbutiono, along the middle cross sectionAB will be as shown in Fig. 1. The structural blocks with higher deformation and strength characteristics are subjected to higher loads and are centers of stress concentration; conversely, the blocks with lower characteristics are partly relieved of load. An important part is played by the shape, size, orientation, and position of each block.In research on the state of stress of the solid rock, the need to take account of the inhomogenetty isgoverned by the relative sizes of the test region and the elements of the tnhomogeneity. Thus the inhomogeneity due to the crystalline structure, the granular structure, and fine stratification and fissuring will not much influence the general laws of distribution of stresses near the exposed rock. In this case the rock mass can be regarded as quasthomogeneous, and the stress distribution in it can be regarded as uniform.A marked influence on the stress distribution in the solid rock can be exerted by lnhomogenelty due to interbedding of rocks of different compositions, to the presence of horizons with different structures, zones of deconsolililliilillllil ~I I ~,.~,.#,~71 i~/ll.?J'g~!. ,I',, 11 ' I e, e,.~e,
II i l~i"tPl t i f ~ y r i Fig. 1. Distribution of vertical stresses in inhomogeneous rock. The E i are the moduli of deformation of the rocks in the separate structural blocks.dation, tectonic faults and fissures, and to large inclusions of rocks with different properties.Inhomogeneity of the solid rock can be of two types [1,2,8]i it may be randomly distributed, or regularly varying. The former is due to random variations of the conditions of formation on the rock; the latter is due to regular spatial variation in these conditions. The state of stress wilt correspondingly depend on the spa...
