Hanging-wall Slopes Research Articles

Effect Of Open-Pit Blasting Vibrations on a Hanging-Wall Slope: A Case Study of the Beizhan Iron Mine in China

With the increase in the depth of large-scale open-pit mining, many mines have to face problems such as what is the effect of open-pit blasting on the rock slope and how to ensure the stability of a high-steep slope. The east slope of the Beizhan iron mine in Hejing County, Xinjiang, belongs to the typical open-pit high and steep slope of mined hanging-wall ore. To study the effect of open-pit blasting vibrations on hanging-wall slope stability, the intelligent blasting vibration detector was used to monitor the open-pit blasting wave of the Beizhan iron mine and the corresponding numerical model was established. We fitted the transmission law of slope blasting vibration by Sodev’s regression formula and calculated stress, strain, and vibration velocity of the whole slope by numerical simulation. The result showed that the fitting functional relationship was correct and could be the basic rule of predicting the maximum charge amount per delay interval and minimum safe distance for this area. The estimated open-pit blasting charge weight was reasonable and blasting vibrations would have little effect on the hanging-wall slope. The research method and conclusions in this article have numerous reference values for studying the hanging-wall slope’s kinetic stability.

Geotechnical study for optimizing the slope design of a deep open-pit mine, India

The study was undertaken to determine the optimal overall slope angle of a lead–zinc mine, which could extend down to a depth of 170 m. Detailed geotechnical investigations were conducted, including geotechnical mapping of existing benches to establish the geometrical and mechanical properties of the discontinuities, the drilling of eight boreholes and the establishment of the physico-mechanical properties of the intact rock. Based on these data, limit equilibrium and numerical simulation techniques were applied to assess the stability of the slopes and determine an optimal slope angle. It was concluded that the overall foot-wall and hanging-wall slopes should be 42 and 48° respectively.

Facies pattern of the middle Permian Barren Measures Formation, Jharia basin, India: The sedimentary response to basin tectonics

In the Lower Gondwana succession of the Jharia basin of eastern India, the Barren Measures Formation is characterized by the cyclic disposition of fine-grained lacustrine deposits and relatively coarse-grained fluvial deposits. The cyclic variation in the rate of coarse clastic input is attributed to the sedimentary response to basin tectonics. The sandstone-shale alternations of the Barren Measures succession can be correlated with the tectonic cyclothems developed on the hangingwall dip-slope and adjoining trough in a continental half-graben setting. Enhancement of the gradient of the hangingwall dip-slope during reactivation of the basin margin faults led to progradation of the existing fluvial system towards the half-graben trough and deposition of the coarser clastics on the fine-grained lacustrine deposits of the trough. Peneplanation of the hangingwall slope and slow increase in the lake level caused lacustrine transgression and retrogration of the fluvial system on the hangingwall block. The fluvial sediments were onlapped by the fine-grained lacustrine deposits. Episodic rejuvenation of the basin margin faults thus caused development of tectonic cyclothem on the hangingwall block. The paleocurrent pattern indicates that a persistent northward paleoslope was maintained during Barren Measures sedimentation. The inferred depositional settings were much more extensive than the present limit of the outcrop. The faults, presently defining the northern limit of the Barren Measures Formation, were possibly emplaced after Barren Measures sedimentation. The final movement along these fault planes caused preservation of the downthrown hangingwall block and the Barren Measures sediments on the footwall block were eroded during subsequent denudation. The Southern Boundary Fault came into existence after the deposition of the Barren Measures sediments.

Incised submarine canyons governing new evidence of Early Triassic rifting in East Greenland

Regional studies of the uppermost Permian and lowermost Triassic successions in central East Greenland have shown that sedimentation took place in half-grabens during two phases of active rifting. The Permian–Triassic boundary locally contains submarine canyons, up to several kilometres wide and several tens of metres deep formed in latest Permian or earliest Triassic times. Sandy and conglomeratic turbidites filling the canyons are highly variable in architecture depending on the structural setting and the geometry of the submarine canyons. Bounding surfaces also change character because of an asymmetric subsidence pattern of tilted fault-blocks. The submarine canyons have been studied on Wegener Halvø, where exposures allow tracing of several canyons from the slope to the basin floor setting. The canyons are interpreted to have developed from fluvial incised valleys furthest updip on the fault-block and from turbidity-current erosion further downdip. The canyons have a SE–NW elongation, while palaeocurrents were unimodal towards the NW reflecting the dip of the rotated fault-block. The canyon fill turbidites were deposited by consequent drainage on a NW-dipping, ramp-like hangingwall slope within a half-graben. In areas between the canyons, the Permian–Triassic boundary is onlapped by Triassic mudstones of offshore marine origin. The studied succession is grouped into two facies associations: (1) submarine gravity-flow sandstones and conglomerates; and (2) suspension-deposited shales and mudstones. Traced down-dip, the submarine canyon fills display a change from chaotic, conglomeratic and coarse sandy high-density turbidites proximally to organised sandy turbidites basinwards. Farthest basinward, a remarkable basin-floor fan with well-developed giant-scale foresets is observed. This trend reflects canyon widening and a decrease in gradient at the basin-floor. Progradation of the turbidites was probably controlled by westward tilting of the fault-block causing a steeper slope and subaerial exposure of a larger part of the proximal hangingwall above the fulcrum. This resulted in erosion of the crestal area of the block, that is, Upper Permian and older successions, and led to an increase in sediment supply to the downdip area. Accommodation space was created below fulcrum and downdip transgression governed back-filling of the submarine canyons. The observed eastward onlap of ammonite zones in shales and mudstones between the canyons was contemporaneous with the filling of the canyons. A later drowning of the updip catchment caused decrease or shut-off of sediment supply leading to deposition of shales and mudstones blanketing the sandy turbidites in the canyons. The tilt of the studied fault-block is interpreted to have caused simultaneous transgression below the fulcrum and regression, with bypass or erosion, above the fulcrum. It is concluded, that the tilted fault-block setting has important consequences for sequence stratigraphic interpretations due to the asymmetric subsidence causing drastic changes in bounding surface character. Tectonism and sediment supply were the main controls on the stratigraphic architecture of the studied Lower Triassic succession on Wegener Halvø.

Optimization of slope angle of a lead-zinc mine

The present study represents an attempt to optimize the overall slope angle of a lead-zinc mine in Rajasthan state, which could extend to a depth of 170 m during the first phase of mining. Detailed geotechnical investigations were conducted. These included geotechnical mapping, determination of the physio-mechanical properties of intact rock, determination of the rock mass rating and estimation of rock mass properties. Information was collected from mapping of benches and borehole logs. Based on these data, limit equilibrium and numerical simulation techniques were applied in order to assess the stability of the slopes and determine an optimum slope angle. From these investigations it has been inferred that the overall footwall and hangingwall slopes should be 42° and 48° respectively.

Slope design based on geotechnical study and numerical modelling of a deep open pit mine in India

ABSTRACT A detailed geotechnical study and numerical modelling were done for optimum slope design of a deep(170 m) open pit mine in Rajasthan state of India. The study includes physical characterization of the discontinuities in and around the mine, geomechanical propertis of the slope materials, estimation of Rock Mass Rating and rock mass properties. The data related to different geotechnical parameters were collected from the benches of the partially developed mine and logs of the boreholes. Further, numerical modelling was done for slope stability and sensitivity analyses, based on which optimum slope angle was determined. The study revealed 42° and 48° overall footwall and hangingwall slope angles respectively. Sensitivity analysis shows that ground water is detrimental to the slopes. Hence, every attempt should be done to control the ground water condition.

Pliocene Burdur basin, SW Turkey: tectonics, seismicity and sedimentation

The Pliocene Burdur Formation of SW Turkey was deposited in a NE-SW trending half-graben with a major basement fault along its SE margin. Hangingwall-sourced fans were confined proximally by basement topography. Distally, they developed 'ideal' fan geometries. These fans became submerged by the lake that occupied the centre of the basin. This transgression was caused by the migration, with time, of the hangingwall pivot away from the basin-controlling fault. Footwall-sourced fans exhibit three distinctly different geometries. At the northern end of the basin a wide braidplain developed due to the rapid erosion of both penecontemporaneous volcaniclastic deposits to the east and the footwall crest of a newly formed fault within the basin. Along the footwall scarp in the central part of the basin a narrow bajada formed. In the south, a large alluvial fan had its source in the relay structure between two left-stepping en echelon fault segments. The small size of footwall-sourced fans compared with those sourced on the hangingwall slope was due to rapid subsidence of the basin floor adjacent to the footwall scarp. Although this suggests high levels of seismicity, the general paucity of wet-sediment deformation within the Burdur Formation indicates that seismicity in the Burdur region during the Pliocene was more subdued than at present.