Stability is the main problem in underground excavations that can result in rock-related accidents or closure of mines. This is often controlled by the geological condition of the rockmass and the in situ stress field where excavation is being carried out. Over the years, conventional support systems such as bolts, shotcrete and mesh have been the standard support systems used in difficult ground conditions to maintain stability of underground openings. The novel Thin Spray Liner (TSL) is a technology with an improvement in terms of support capabilities for difficult geological conditions. This technology is predicted to replace conventional support systems, as it offers a significant yielding capacity that is better than that of the traditional techniques of controlling strata. The performance of the TSL lies between that of shotcrete and wire mesh. The TSL has numerous advantages regarding rock reinforcement such as rapid curing period, fast application, high tensile strength, high adhesion properties that prevent movement of rock keyblocks, improved cycle times, reduction in material-handling compared to shotcrete, and a significant ability to penetrate joints. These advantages increase the allowance for mechanisation and improvement of safety in excavations. Despite various benefits of TSLs, there are shortcomings which make end-users to be sceptical about the technology. This study provides a detailed review of the mechanism, properties, composition and types, as well as the general and mining applications of TSLs. It also describes the challenges faced by the mining industry and other end-users in accepting the technology as a solution for stability issues in underground openings. In addition, some insightful suggestions are made as recommendations for future work on the development of suitable, effective and efficient thin surface rock support technology within limitations/constraints.
Landslides - Assessment of the spatial probability of future landslide occurrences for disaster risk reduction is done through landslide susceptibility modelling. In this study, we investigated the... 相似文献
Landslides - India ranks first in the world in terms of fatal landslides. Large vulnerable area (0.42 million km2), high population density and monsoon rainfall make India’s landslide... 相似文献
With oblique rifting, both extension perpendicular to the rift trend and shear parallel to the rift trend contribute to rift formation. The relative amounts of extension and shear depend on α, the acute angle between the rift trend and the relative displacement direction between opposite sides of the rift. Analytical and experimental (clay) models of combined extension and left-lateral shear suggest the fault patterns produced by oblique rifting. If α is less than 30°, conjugate sets of steeply dipping strike-slip faults form in rifts. Sinistral and dextral strike-slip faults trend subparallel and at large angles to the rift trend, respectively. If α is about 30°, strike-slip, oblique-slip and/or normal faults form in rifts. Faults with sinistral and dextral strike slip trend subparallel and at large angles to the rift trend, respectively. Normal faults strike about 30° counterclockwise from the rift trend. If α exceeds 30°, normal faults form in rifts. They have moderate dips and generally strike obliquely to the rift trend and to the relative displacement direction between opposite sides of the rift. If α equals 90°, the normal faults strike parallel to the rift trend and perpendicularly to the displacement direction.The modeling results apply to the Gulf of California and Gulf of Aden, two Tertiary continental rift systems produced by combined extension and shear. Our results explain the presence and trends of oblique-slip and strike-slip faults along the margins of the Gulf of California and the oblique trend (relative to the rift trend) of many normal faults along the margins of both the Gulf of California and the Gulf of Aden. 相似文献
We report broadband infrared photometry of comets P/Stephan-Oterma and Bowell between 1 and 20 μm. Their JHK colors are similar to P/Meier and P/Tuttle and are compatible with scattering of sunlight by micron-sized grains. The thermal emission from P/Stephan-Oterma showed an effective temperature significantly higher than that expected from a blackbody in equilibrium. The thermal emission can be models be fit by models of the dust coma consisting of micron-sized grains. Most of the flux at all observed wavelengths comes from the dust grains rather than form the nucleus. 相似文献
We consider the inverse problem of permeability estimation for two-phase porous-media flow. The novel approach is based on
regularization by zonation, where the geometry and size of the regions are chosen adaptively during the optimization procedure.
To achieve this, we have utilized level-set functions to represent the permeability. The available data are sparsely distributed
in space; hence, it is reasonable to confine the estimation to coarse-scale structures. The level-set approach is able to
alter the boundaries between regions of different permeability without strict restrictions on their shape; however, when the
data are sparse, a reasonable initial guess for the permeability is required. For this task, we use adaptive multiscale permeability
estimation, which has the potential of identifying main permeability variations. These are described by a piecewise constant
function, where the constant values are attained on rectangular zones. In the current work, we develop a level-set corrector
strategy, assuming adaptive multiscale permeability estimation as a predictor. 相似文献
We present a comparison between the peculiar velocity fields measured from a recently completed l -band Tully–Fisher survey of field spirals (SFI) and that derived from the IRAS 1.2-Jy redshift survey galaxy distribution. The analysis is based on the expansion of these data in redshift space using smooth orthonormal functions, and is performed using low- and high-resolution expansions, with an effective smoothing scale which increases almost linearly with redshift. The effective smoothing scales at 3000 km s−1 are 1500 and 1000 km s−1 for the low- and high-resolution filters. The agreement between the high- and low-resolution SFI velocity maps is excellent. The general features in the filtered SFI and IRAS velocity fields agree remarkably well within 6000 km s−1. This good agreement between the fields allows us to determine the parameter β = Ω0.6 / b , where Ω is the cosmological density parameter, and b is the linear biasing factor. From a likelihood analysis on the SFI and IRAS modes we find that β = 0.6 ± 0.1, independently of the resolution of the modal expansion. For this value of β, the residual fields for the two filters show no systematic variations within 6000 km s−1. Most remarkable is the lack of any coherent, redshift-dependent dipole flow in the residual field. 相似文献
Rb-Sr whole rock isochron ages of 1950 m.y. and 1725 m.y. obtained on rock units of the Hagar migmatite sheet indicate that it is an early Proterozoic gneiss complex and not part of a mobile Caledonian infrastructure. New isotopic ages and recent fieldwork give no support to the concept of mobile Caledonian migmatitic masses rising into the suprastructure as envisaged in the classic stockwerke model for the East Greenland Caledonian fold belt. However, K-Ar mineral ages ranging from 415–462 m.y. indicate a significant Caledonian thermal event. Relationships between the Hagar sheet and bordering metasediments are discussed, including evidence for a middle Proterozoic group of sediments metamorphosed before deposition of the late Precambrian Petermann Series and Eleonore Bay Group. 相似文献
