The Experts below are selected from a list of 162 Experts worldwide ranked by ideXlab platform

M Gregory - One of the best experts on this subject based on the ideXlab platform.

  • The effect of surface topography on the stability of coal mine openings
    AAPG Bulletin, 1991
    Co-Authors: Molinda, M Gregory
    Abstract:

    Coal mine roof quality has long been observed to appeared to deteriorate when mining progressed beneath surface valleys. A survey of seven Appalachian coal mines shows a clear correlation between mining beneath stream valleys and hazardous roof conditions. Of all bad-top occurrences in the surveyed mines, 52% of them happened directly beneath the bottom-most part of the valley. This relationship can be due to a number of associations ranging from structural control of drainage to stress concentrations beneath the valley apex. BuMines research has recently produced evidence of valley stress relief as a significant mechanism for the production of Poor Rock Mass quality beneath stream valleys. bedding plane slips and thrust faults, due to horizontal compression perpendicular to the valley trend, have been observed beneath a number of valleys. This valley effect may be due to transfer of load from the adjacent hillsides or relief of regional stress in the valley due to low confinement. Horizontal stress measurements in a coal mine roof beneath a valley with Poor roof conditions confirms partial stress relief. Additionally, numerical modeling of a number of valleys over a single mine property calculates the valley effect on the stress field. The model also demonstrates themore » influence of depth of cover and orientation of the valley to the direction of principal stress on the likelihood of shear failure in the roof.« less

Yilin Fan - One of the best experts on this subject based on the ideXlab platform.

  • in situ observation of failure mechanisms controlled by Rock Masses with weak interlayer zones in large underground cavern excavations under high geostress
    Rock Mechanics and Rock Engineering, 2017
    Co-Authors: Shuqian Duan, Xiating Feng, Quan Jiang, Guofeng Liu, Shufeng Pei, Yilin Fan
    Abstract:

    A weak interlayer zone (WIZ) is a Poor Rock Mass system with loose structure, weak mechanical properties, variable thickness, random distribution, strong extension, and high risk due to the shear motion of Rock Masses under the action of tectonism, bringing many stability problems and geological hazards, especially representing a potential threat to the overall stability of Rock Masses with WIZs in large underground cavern excavations. Focusing on the deformation and failure problems encountered in the process of excavation unloading, this research proposes comprehensive in situ observation schemes for Rock Masses with WIZs in large underground cavern on the basis of the collection of geological, construction, monitoring, and testing data. The schemes have been fully applied in two valuable project cases of an underground cavern group under construction in the southwest of China, including the plastic squeezing-out tensile failure and the structural stress-induced collapse of Rock Masses with WIZs. In this way, the development of Rock Mass failure, affected by the step-by-step excavations along the cavern’s axis and the subsequent excavation downward, could be observed thoroughly. Furthermore, this paper reveals the preliminary analyses of failure mechanism of Rock Masses with WIZs from several aspects, including Rock Mass structure, strength, high stress, ground water effects, and microfracture mechanisms. Finally, the failure particularities of Rock Masses with WIZs and rethink on prevention and control of failures are discussed. The research results could provide important guiding reference value for stability analysis, as well as for rethinking the excavation and support optimization of Rock Masses with WIZs in similar large underground cavern under high geostress.

Xiating Feng - One of the best experts on this subject based on the ideXlab platform.

  • in situ observation of failure mechanisms controlled by Rock Masses with weak interlayer zones in large underground cavern excavations under high geostress
    Rock Mechanics and Rock Engineering, 2017
    Co-Authors: Shuqian Duan, Xiating Feng, Quan Jiang, Guofeng Liu, Shufeng Pei, Yilin Fan
    Abstract:

    A weak interlayer zone (WIZ) is a Poor Rock Mass system with loose structure, weak mechanical properties, variable thickness, random distribution, strong extension, and high risk due to the shear motion of Rock Masses under the action of tectonism, bringing many stability problems and geological hazards, especially representing a potential threat to the overall stability of Rock Masses with WIZs in large underground cavern excavations. Focusing on the deformation and failure problems encountered in the process of excavation unloading, this research proposes comprehensive in situ observation schemes for Rock Masses with WIZs in large underground cavern on the basis of the collection of geological, construction, monitoring, and testing data. The schemes have been fully applied in two valuable project cases of an underground cavern group under construction in the southwest of China, including the plastic squeezing-out tensile failure and the structural stress-induced collapse of Rock Masses with WIZs. In this way, the development of Rock Mass failure, affected by the step-by-step excavations along the cavern’s axis and the subsequent excavation downward, could be observed thoroughly. Furthermore, this paper reveals the preliminary analyses of failure mechanism of Rock Masses with WIZs from several aspects, including Rock Mass structure, strength, high stress, ground water effects, and microfracture mechanisms. Finally, the failure particularities of Rock Masses with WIZs and rethink on prevention and control of failures are discussed. The research results could provide important guiding reference value for stability analysis, as well as for rethinking the excavation and support optimization of Rock Masses with WIZs in similar large underground cavern under high geostress.

Bjørn Nilsen - One of the best experts on this subject based on the ideXlab platform.

  • Characteristics of Water Ingress in Norwegian Subsea Tunnels
    Rock Mechanics and Rock Engineering, 2014
    Co-Authors: Bjørn Nilsen
    Abstract:

    Water ingress represents one of the main challenges in subsea tunnelling, particularly when this occurs in sections with Poor Rock Mass quality. This paper is discussing the main characteristics of water ingress in subsea hard Rock tunnels based on the experience from almost 50 such tunnels that have been built in Norway. Following a brief description of the geological conditions and the basic design of the subsea tunnels, pre-construction investigations and investigations during excavation are discussed with particular emphasis on prediction of water ingress. Two cases with particularly difficult conditions; the Bjorøy tunnel and the Atlantic Ocean tunnel, are discussed in detail. In these cases, large water inflow with pressure of up to 2.4 MPa was encountered at major faults/weakness zones during excavation, and special procedures were required to cope with the problems. Based on the experience from the Norwegian projects, it is concluded that continuous follow-up by experienced engineering geologists, probe drilling with the drilling jumbo and pre-grouting where required are the most important factors for coping with water ingress and ensuring stability.

Molinda - One of the best experts on this subject based on the ideXlab platform.

  • The effect of surface topography on the stability of coal mine openings
    AAPG Bulletin, 1991
    Co-Authors: Molinda, M Gregory
    Abstract:

    Coal mine roof quality has long been observed to appeared to deteriorate when mining progressed beneath surface valleys. A survey of seven Appalachian coal mines shows a clear correlation between mining beneath stream valleys and hazardous roof conditions. Of all bad-top occurrences in the surveyed mines, 52% of them happened directly beneath the bottom-most part of the valley. This relationship can be due to a number of associations ranging from structural control of drainage to stress concentrations beneath the valley apex. BuMines research has recently produced evidence of valley stress relief as a significant mechanism for the production of Poor Rock Mass quality beneath stream valleys. bedding plane slips and thrust faults, due to horizontal compression perpendicular to the valley trend, have been observed beneath a number of valleys. This valley effect may be due to transfer of load from the adjacent hillsides or relief of regional stress in the valley due to low confinement. Horizontal stress measurements in a coal mine roof beneath a valley with Poor roof conditions confirms partial stress relief. Additionally, numerical modeling of a number of valleys over a single mine property calculates the valley effect on the stress field. The model also demonstrates themore » influence of depth of cover and orientation of the valley to the direction of principal stress on the likelihood of shear failure in the roof.« less