Regional Joint Patterns Research Articles

Ground movements caused by deep underground mining in Guan-Zhuang iron mine, Luzhong, China

It is difficult to calculate the accurate ground movement due to deep underground mining because of the complexity of the geotechnical environment. Guan-Zhuang iron mine is a pillarless sublevel caving mine operated by Luzhong Metallurgical Mining Company, south-east of Jinan, PR China. It mines the Zhangjiawa Seam at a depth of approximately 520m. Although the towers are outside the conventional 'angle of draw’ subsidence influence criteria, and have seen only negligible vertical displacement as a result of deep mining, there has been widespread evidence of regional horizontal displacement of the land surface, large distances away from the mining area. Possible explanations of these displacements include one or a combination of mechanisms such as pre-mining stress relaxation, regional joint patterns, soft rock strata, displacement toward active goaf areas. Luzhong Metallurgical Mining Company have been making precise measurements of distances near the shaft towers in the Guan-Zhuang iron mine since 2003. The results show horizontal displacements of up to 96mm occur even when underground mining is about 0.8km from the survey displacements. From an analysis of these and other survey results it is concluded that mining effects extend a long way from deep mining. The results also show that ground horizontal displacements are typically at least as great as the vertical component, that the maximum horizontal displacement occurs soon after undermining.

Regional joint pattern in the Taurus-Zagros range, Northern Iraq : Ameen, M S Proc Conference on Fractured and Jointed Rock Masses, Lake Tahoe, 3–5 June 1992P140–149. Publ California: Lawrence Berkeley Laboratory, 1992

Regional joint pattern in the Taurus-Zagros range, Northern Iraq : Ameen, M S Proc Conference on Fractured and Jointed Rock Masses, Lake Tahoe, 3–5 June 1992P140–149. Publ California: Lawrence Berkeley Laboratory, 1992

Landsat imagery interpretation as a tool in the exploration for groundwater in the Federal Capital Territory of Nigeria

Fracture traces or lineaments visible on landsat imageries covering the new Federal Capital Territory of Nigeria have been studied with the objective of using the data as prospecting guide in locating zones of increased weathering, solutioning and permeability. The Gvvagwa plains underlain by metamorphic rocks mostly granitic gneisses and migmatites showed the highest concentration of lineaments oriented in the NW-SE, NE-SW and N-S directions. Several prospective borehole locations have been determined based on the zones of intersections of the lineaments. A close relationship exists between the mapped lineament traces and the regional joint pattern and structural trend in the area.

The structure and emplacement of the Rio Fortaleza Centred acid complex, Ancash, Peru

The Rio Fortaleza centre is one of four known centred complexes of the Coastal Batholith and is a hypabyssal ring-dyke complex. Subterranean cauldron subsidence is represented by a bell-jar pluton, while a later ring-dyke may have produced subaerial pyroclastics associated with a caldera. Inclusion screens represent the remnants of spalled-off country rock and ring-fault mylo-nites, tuffisites and gas breccias with limited hydrothermal mineralizations are indications of its high-level nature. The two ring-dykes, some 22 km in diameter, are structurally controlled with polygonal outcrop patterns related to the regional joint pattern. At depth, the intersections of major wrench fractures may have focussed the magmas and delimited the symmetrical disposition of the four centres. The centred complexes show a close relation between plutonism and vulcanism and prob­ably represent the basal remnants of caldera volcanoes that supplied some of the extrusive envelope of the batholith.

Jointing in the Appalachian Plateau of Pennsylvania

The Appalachian Plateau, extending from the Folded Appalachians to the Central Stable Interior, contains Pennsylvanian and Permian cyclic sedimentary rocks which permit study of joints in coal and shale throughout a region of deformation that diminishes to the northwest. The basic unit of jointing is the fundamental joint system, comprised of an approximately orthogonal systematic and nonsystematic set of joints. Complex systems of jointing arise from overprinting of two or more fundamental systems, each of which may occur alone in adjacent areas. In north-central Pennsylvania, the local and regional joint patterns of coals and shales differ: systematic joints in coals are tangent to an arc, convex to the south, with a center of curvature at approximately 78° W. long., in northern Pennsylvania; systematic joints in shales strike north or northwest grossly transverse to northeast-trending fold axes of the Folded Appalachians and Appalachian Plateau. Locally, systematic joints in shale extend into underlying coals and have been overprinted upon the older arcuate pattern of joints in coal. Although systematic joints in shale are grossly transverse to fold axes, no one set of joints remains perpendicular to folds, which bend from N. 30° E. to N. 70° E., throughout the region. Rather, the regional joint pattern consists of overlapping joint trends of remarkably uniform orientation, each trend being dominant (showing greatest size, frequency, and persistence) where it is most nearly perpendicular to fold axes. The joint pattern of the region is cumulative, presenting a record of all events which have produced stress differences sufficient to induce fracture. Systematic joints formed early, independent of folds and faults. This is evinced by the complete independence of joints in coal and fold axis trends, by greater consistency of regional strike of joints in shale than of fold axis orientation, by the rotation of joints adjacent to faults, and by the presence of systematic joints west of folds of Appalachian trend. Although systematic joints may be polygenetic, their mutual relations, relations to nonsystematic joints, surface character, open, lensing nature, and lack of lateral movement suggest that they are of extensional origin. Nonsystematic joints of the special type, here called “truncated joints,” are also of extensional origin although they are probably late release-type fractures resulting from a combination of residual tectonic stress differences and surficial stress differences arising in blocks between successive systematic joints during erosion and unloading.

Regional Study of Jointing in Comb Ridge-Navajo Mountain Area, Arizona and Utah

The spatial relations of joints and, in particular, structural details of individual joints, offer clues of their origin. Important features of joints have been largely neglected in previous joint studies and the present study is an attempt to determine more closely the true nature of joints in sedimentary rocks and to suggest a mode of origin more in line with field observations than is present theory. The study area comprises about 2,000 square miles of the Colorado Plateau in northeastern Arizona and southeastern Utah where sedimentary rocks ranging from Pennsylvanian to late Cretaceous in age are exposed. A simple, non-genetic joint classification is presented based on the spatial relations of joints and the plumose structures on joint faces. Joints are grouped as systematic or non-systematic with cross-joints defined as an important variety of non-systematic joints. Plumose structures on joint faces indicate that joints are initiated at some structural inhomogeneity within the rock and propagated outward, thus precluding movement in the direction of the joint faces at the time of formation. Spatial relations of systematic joints point to formation at or near the earth's surface in a remarkably homogeneous stress field. The regional joint pattern is composed of a complex series of overlapping joint trends. The pattern as a whole extends through the entire exposed rock sequence. Intersecting joint trends have no visible effect on each other and may terminate independently in any direction. Each joint trend of the regional pattern crosses several folds of considerable magnitude but does not swing to keep a set angular relation to a fold axis as the axis changes direction. Hypotheses stating that joints are related genetically to folding are rejected for the mapped area. The shear, tension, or torsion theories of jointing require that only one or two sets of joints be considered as the result of a particular stress condition. Where more sets are present, different stress conditions must be postulated for each set or pair of sets believed to be related genetically. The joint pattern in the mapped area can not be interpreted in such terms without making these assumptions, Alternatively, in accord with theoretical and experimental evidence, semi-diurnal earth tides are considered as a force capable of producing joints in rocks through a fatigue mechanism. Field observations suggest that joints form early in the history of a sediment and are produced succes ively in each new layer of rock as soon as it is capable of fracture. The joint pattern in pre-existing rocks may be reflected upward into new, non-jointed rock, and so control the joint directions. Much critical data from areas with different geologic histories are needed before a quantitative evaluation of this hypothesis can be made. The question of the ultimate origin of the regional joint pattern and its genetic relation, if any, to other structure at depth can not be answered on data now available.