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Geological Structures
Published in F.G.H. Blyth, M. H. de Freitas, A Geology for Engineers, 2017
F.G.H. Blyth, M. H. de Freitas
The name monocline is given to a flexure that has two parallel gently dipping (or horizontal) limbs with a steeper middle part betwen them; it is in effect a local steepening of the dip (Fig. 8.5), and differs from an anticline in that the dips are in one direction only. Large monoclines are sometimes developed in sedimentary rocks overlying a rigid basement when the latter has been subject to fault movement.
Segmentation and fault–monocline relationships in the Lapstone Structural Complex, Sydney Basin, New South Wales
Published in Australian Journal of Earth Sciences, 2023
C. L. Fergusson, P. J. Hatherly
The LSC is a 95 km-long association of faults and fault-propagation monoclines in the western Sydney Basin that is related to a basement thrust fault dipping to the west and underlying the Blue Mountains. The LSC has numerous segments that link at depth into the thrust fault. In the southern part of the complex, the main segments are characterised by a single west-dipping thrust (e.g. Bargo Fault) with relatively small offset (∼60 m) or a high-angle reverse fault (e.g. Nepean Fault) that presumably is listric and dips less steeply at depth also with minor offset (∼100 m). From Nortons Basin northward, the LSC is characterised by a single main monocline (the Lapstone Monocline) and is divided into two segments, a southern segment with a monocline that developed as a fault-propagation fold above the west-dipping thrust at depth, and a northern segment with a wider central limb of the monocline and shortening at depth accommodated by inferred imbricate thrust faults, each with minor offset and linking at depth into the main thrust fault. The Kurrajong Fault System represents the western extent of the fault-propagation fold. The main west-dipping controlling thrust of the LSC is seismogenic, as shown by earthquakes in the Blue Mountains in contrast to their lower abundance in the Sydney region east of the LSC.
Low-temperature oxidation and self-heating accelerated spontaneous combustion properties of a Yima formation bituminous coal with various moisture contents
Published in International Journal of Coal Preparation and Utilization, 2022
Gang Li, Wen-Hao Huangfu, Fei You, Ze-Yang Song, Wen-Da Wang, Yuan-Shu Zhu
Gengcun coalfield has complex geological structures as shown in Figure 2 (Shen 2006). It consists of gentle folds and multitudinous faults. Since the influence of F16 fault to the reverse fault, the syncline axis is only intermittently remained in the west of the 45 line, resulting in the fault contact with the Triassic System in the southern coal system. Thus, the main Gengcun coalfield shows a monocline structure at the north wing of the Yima syncline which is on the whole inclined to the south. The monoclinic structure is gentle, the dip angle is generally between 11° and 16°, and the formation is only locally erected or reversed near the F16 fault. Under the above conditions, the Yima coal samples are inherently different and own their features in spontaneous combustion processes.
Risk assessment of gas outburst in tunnels in non-coal formation based on the attribute mathematical theory
Published in Geomatics, Natural Hazards and Risk, 2019
Kai Zhang, Wenbo Zheng, Cong Xu, Shougen Chen
In the survey phase, the seismic exploration was applied to obtain the geological structure information for the tunnel. Probe boreholes were drilled to obtain geological information, including formation lithology, the inclination angle of rock formation, the integrity of rock mass and flow rate of groundwater, and the gas-related information, including gas concentration and gas pressure. The tunnel zone is located in monocline formation, and no fault crosses the tunnel zone. The inclination angle of rock formation changes from 2° to 8°. The main geologic formations crossed by the tunnel are composed of sandstone, mudstone, and mudstone intercalated with sandstone. Figure 3 shows the engineering geology for the tunnel. Gas was found in two boreholes that were drilled at chainage 635,165 and 637,745 m. The maximum concentration tested in borehole was 6500 and 2730 ppm, respectively, and the maximum gas pressure was 0.2 and 0.12 MPa, respectively. Based on the geological structure information and the gas-related information obtained in the survey phase, the risk of the gas outburst at chainage 635,165 m and 637,745 m was assessed by using the proposed attribute synthetic evaluation system.