Initiation and formation of folds and the Kazerun high-angle fault zone, in the Zagros fold-and-thrust belt, were related to the continuing SW–NE oriented contraction that probably initiated in the Late Cretaceous, and intensified, starting in Miocene, when the Arabian and Eurasian plates collided. The contraction that led to folding and thrusting of the Phanerozoic sequence in the belt has led to the strike–slip reactivation of basement faults that formed during the Precambrian. Two major systems of fractures have developed, under the same regional state of contraction, during the folding and strike–slip faulting processes. Folding led to the formation of a system of fold-related fractures that comprises four sets of fractures, which include an axial and a cross-axial set that trend parallel and perpendicular to the confining fold axial trace, respectively, and two oblique sets that trend at moderate angles to the axial trace. Slip along high-angle, strike–slip faults formed a system of fractures in the damage zone of the faults (e.g., Kazerun), and deformed folds that existed in the shear zone by rotating their axial plane. This fault-related fracture system is made of five sets of fractures, which include the two sets of Riedel shear fractures (R and R′), P- and Y-shear fractures, and an extensional set.
Remote sensing analysis of both fracture systems, in a GIS environment, reveals a related kinematic history for folding outside of the Kazerun shear zone and faulting and deformation (fracturing and rotation of folds) within the Kazerun fault zone. Rotation of the folds and formation of the five sets of the fault-related fractures in the Kazerun shear zone are consistent with a dextral motion along the fault. The mean trends of the shortening directions, independently calculated for the fold- and fault-related fracture systems, are remarkably close (N53 ± 4°E and N50 ± 5°E, respectively), and are perpendicular to the general NW–SE trend of the Zagros fold-and-thrust belt. Although segments of the Kazerun fault are variably oriented within a narrow range, the angular relationships between sets of fault-related fractures and these segments remain constant. 相似文献
Summary This paper describes development of a generic nonlinear, dynamic modelling technique to simulate discrete rock fractures due
to blasting using the finite element method. The element elimination technique together with a brittle, Rankine failure-type
material model are used as a means to simulate the initiation and growth of fractures in the rock under the effect of blast-induced
dynamic pressure pulse. Dynamic loads representing ideal and non-ideal detonations are simulated and a new method, termed
as optimised pressure profile, is proposed to approximate the pressure-time profile of the blast load to model the dynamic
load. Comparison of numerical model results with previously reported observations from the literature reveals the ability
of the model as a predictive tool and supports the validity of the developed modelling procedure.
Author’s address: Hani S. Mitri, Department of Mining, Metals and Materials Engineering, McGill University, 3450 University
Street, Montreal, Canada H3A 2A7 相似文献
Tectonic fractures are important factors that influence oil and natural gas migration and accumulation within “buried hill” reservoirs. To obtain a quantitative forecast of the development and distribution of reservoir fractures in the Damintun Depression, we analyzed the characteristics of regional structural evolution and paleotectonic stress field setting. A reasonable geological model of the research area was built based on an interpretation of the geological structure, a test for rock mechanics, and experiment on acoustic emission. Thereafter, a three-dimensional paleotectonic stress field during the Yanshan movement was simulated by the finite element method. Rock failure criterion and comprehensive evaluation coefficient of fractures were used to determine the quantitative development of fractures and predict zones that are prone to fracture development. Under an intense Yanshan movement, high stress strength is distributed in the south and northeast parts of the study area, where stress is extremely high. The fracture development zones are mainly controlled by the tectonic stress field and typically located in the same areas as those of high maximum principal and shear stresses. The predicted areas with developed fractures are consistent with the wells with high fracture linear density and in locations with high-producing oil and gas wells. 相似文献