Stability and sensitivity analysis of Himalayan road cut debris slopes: an investigation along NH-58, India     

T. Siddque  S. P. Pradhan 《Natural Hazards》2018,93(2):577-600

The complex geological environment due to active tectonics and varied lithology with multiple phases of deformation and metamorphism led to a rugged topography and large destabilization of slopes in the Himalayan region. However, the ever-rising activities due to various ongoing developmental and urbanization processes in the region are contributing to instability of slopes. The significant number of causalities and massive economic loss is deliberately endangering Himalayan ecosystem due to landslide-related phenomena. Transportation corridors within Himalayan terrain experience frequent landslides, particularly the sections manifested by debris slopes. From several decades, the national highway-58, in Uttarakhand, Himalayas, has been endangered due to diverse and incessant slope failures. The present investigation demonstrates the stability appraisal along the strategic transportation corridor. These studies incorporate the various issues and causes pertaining to debris slides from Rishikesh to Devprayag, Uttarakhand. The numerical simulation assessment was undertaken by deterministic and sensitivity analyses by conventional limit equilibrium methods which is being augmented by much advanced and robust finite element tool. Factor of safety for each slope was determined, and correspondingly, best efficient slope stabilization remedies were proposed to enhance the stability of slopes. It is recommended that such strategic slope stability assessment should be performed within different vulnerable sections of the Himalayas and likewise regions for fruitful and sustainable step toward disaster mitigation.  相似文献   

Characterization of fluid inclusions from mineralized pegmatites of the Damara Belt,Namibia: insight into late-stage fluid evolution and implications for mineralization     

Ashworth  Luisa  Kinnaird  Judith Ann  Nex  Paul Andrew Martin  Erasmus  Rudolph Marthinus  Przybyłowicz  Wojciech Józef 《Mineralogy and Petrology》2018,112(6):753-765

Mineralogy and Petrology - Mineralized NYF and LCT pegmatites occur throughout the northeast-trending Neoproterozoic Damara Belt, Namibia. Mineralization in the pegmatites varies geographically,...  相似文献   

Tellurium,selenium and cobalt enrichment in Neoproterozoic black shales,Gwna Group,UK: Deep marine trace element enrichment during the Second Great Oxygenation Event          下载免费PDF全文

Joseph G. T. Armstrong  John Parnell  Liam A. Bullock  Magali Perez  Adrian J. Boyce  Jorg Feldmann 《地学学报》2018,30(3):244-253

Black shales of the late Neoproterozoic Gwna Group (570–580 Ma), UK, contain enrichments of tellurium (Te), selenium (Se) and cobalt (Co) relative to average shale compositions. The Te and Co enrichments bear comparison with those of ferromanganese crusts in the modern deep ocean. Gwna Group deposition coincides with the Second Great Oxidation Event, which had a significant effect on trace element fixation globally. Selenium and Te concentrations within these black shales indicate increased continental weathering rates, high biological productivity and corresponding increases in atmospheric O₂ concentrations. Cobalt, nickel (Ni) and arsenic (As) enrichments in this succession are secondary mineralisation phases. Demand for many of the trace elements found enriched in the Gwna Group black shales make their mechanisms of accumulation, and variations through the geological record, important to understand, and suggests that new resources may be sought based on black shale protoliths from this period.  相似文献   

Effect of Fly Ash and Rice Husk Ash on Index and Engineering Properties of Expansive Clays     

B. R. Phanikumar  T. V. Nagaraju 《Geotechnical and Geological Engineering》2018,36(6):3425-3436

Many innovative ameliorating techniques including chemical stabilization have been in practice for improving the behaviour of problematic, highly expansive clays. This paper presents a comparative study on the effect of fly ash (FA) and rice husk ash (RHA) on index and engineering properties of an expansive clay. Liquid limit (LL), plastic limit, plasticity index (PI) and free swell index (FSI), and coefficient of permeability (k), unconfined compressive strength and swelling pressure were determined at varying quantities of FA and RHA. Coefficient of permeability, swelling pressure and unconfined compressive strength of the FA-clay and the RHA-clay blends were determined at their respective OMC and MDD obtained from Proctor compaction tests. LL, PI and FSI decreased significantly with increasing FA and RHA contents. Coefficient of permeability, however, increased with additive content. Further, swelling pressure of the blends decreased with increasing additive content.  相似文献   

The development of the subduction channel and “turning on” of slab-to-mantle material exchanges at the start of subduction: insights from eruptive serpentinites (IODP Exp 366) from the forearc of the Mariana subduction system     

Jeffrey G. Ryan  Raymond Johnston  P. Fryer  C.G. Wheat  T. Williams 《《地质学报》英文版》2018,92(Z1):167-167

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EarthScope:Accomplishments and Legacy     

Jeffrey T. Freymueller 《《地质学报》英文版》2018,92(Z1):9-9

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Rupture of the Indian slab in the 2011 Mw 6.9 Sikkim Himalaya earthquake and its tectonic implications     

T. C. Sunilkumar  Anil Earnest  K. Silp  Ronia Andrews 《《地质学报》英文版》2018,92(Z1):58-58

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Generation and Development of Structures and Their Controls on Ore Mineralization in the Lehong Zinc-lead Deposit,Northeastern YunnanEI北大核心CSCD     

Cui J.  Han R.  Wang J.  Ren T.  Wu Y.  Zhao D. 《大地构造与成矿学》2018,(4):664-680

The Lehong zinc-lead deposit is one of the new-found large Zn-Pb deposits in the Sichuan- Yunnan-Guizhou Zn-Pb poly-metallic mineralization area. The ore-bodies of the Lehong deposit are strictly controlled by structures, and the fault tectonites can be divided into four groups which include morbruk rock, cataclastic rock and tectonic breccia. The mechanical properties of the faults suggest that there are five tectonic systems formed in the Caledonian-early Hercynian, Indosinian-early Yanshanian, mid-Yanshanian, late Yanshanian and Himalayan periods, respectively. The Lehong fault and the Qiaojia-Lianfeng fault are two important ore-controlling structures which might have acted as channel ways of the ore fluids. The ores are hosted in the subordinary fracture zone, joint fracture zone and interlayer fault zones in trailing folds of the Lehong fault and the Baobaoshang syncline and Jinjiagou anticline. Hence, the Lehong deposit is a tectonic -controlled ore deposit. These research do not only lay a foundation for studying deposit genesis and ore-finding direction in the Lehong deposit, but also provides important enlightenments for the ore-finding prognosis of lead-zinc deposits in northwestern Guizhou ore concentration district. © 2018, Science Press. All right reserved.  相似文献   

Hydrogeology of a montane headwater groundwater system downgradient of a coal-mine waste rock dump: Elk Valley,British Columbia,Canada     

Jakub T. Szmigielski  S. Lee Barbour  Sean K. Carey  John Kurylo  A. F. McClymont  M. Jim Hendry 《Hydrogeology Journal》2018,26(7):2341-2356

Steelmaking-coal waste rock placed in mountain catchments in the Elk Valley, British Columbia, Canada, drain constituents of interest (CIs) to surface water downgradient of the waste rock dumps. The role of groundwater in transporting CIs in the headwaters of mountain catchments is not well understood. This study characterizes the physical hydrogeology of a portion of a 10-km² headwater catchment (West Line Creek) downgradient of a 2.7-km² waste rock dump placed over a natural headwater valley-bottom groundwater system. The study site was instrumented with 13 monitoring wells. Drill core samples were collected to determine subsurface lithology and geotechnical properties. The groundwater system was characterized using field testing and water-level monitoring. The valley-bottom sediments were composed of unconsolidated glacial and meltwater successions (<64 m thick) deposited as a series of cut and fill structures overlying shale bedrock. An unconfined basal alluvial aquifer located above fractured bedrock was identified as the primary conduit for groundwater flow toward Line Creek (650 m from the toe of the dump). Discharge through the basal alluvial aquifer was estimated using the geometric mean hydraulic conductivity (±1 standard deviation). These calculations suggest groundwater discharge could account for approximately 15% (ranging from 2 to 60%) of the total water discharged from the watershed. The residence time from the base of the waste rock dump to Line Creek was estimated at <3 years. The groundwater system was defined as a snowmelt (i.e., nival) regime dominated by direct recharge (percolation of precipitation) across the catchment.  相似文献   

The First Hop: Use of Beaufort Sea Deltas by Hatch-Year Semipalmated Sandpipers     

Roy T. Churchwell  Steve Kendall  Stephen C. Brown  Arny L. Blanchard  Tuula E. Hollmen  Abby N. Powell 《Estuaries and Coasts》2018,41(1):280-292

River deltas along Alaska’s Beaufort Sea coast are used by hatch-year semipalmated sandpipers (Calidris pusilla) after leaving their terrestrial natal sites, but the drivers of their use of these stopover sites on the first “hop” of fall migration are unknown. We quantified sandpiper temporal distribution and abundance as related to food resources at three river deltas during the beginning of their fall migration (post-breeding period) to compare the habitat quality among these deltas. We conducted population counts, sampled invertebrates, and captured birds to collect blood samples from individuals for triglyceride and stable isotope analyses to determine fattening rates and diet. Patterns of sandpiper and invertebrate abundance were complex and varied among deltas and within seasons. River deltas were used by sandpipers from late July to late August, and peak sandpiper counts ranged from 1000 to 4000 individuals, of which 98% were hatch-year semipalmated sandpipers. Isotopic signatures from blood plasma samples indicated that birds switched from a diet of upland tundra to delta invertebrate taxa as the migration season progressed, suggesting a dependence on delta invertebrates. Despite differences in diet among deltas, we found no differences in fattening rates of juvenile sandpipers as indicated by triglyceride levels. The number of sandpipers was positively associated with abundance of Amphipoda and Oligochaeta at the Jago and Okpilak-Hulahula deltas; an isotopic mixing model indicated that sandpipers consumed Amphipoda and Oligochaeta at Jago, mostly Chironomidae at Okpilak-Hulahula and Spionidae at Canning. Regardless of the difference in sandpiper diets at the Beaufort Sea deltas, their similar fattening rates throughout the season indicate that all of these stopover sites provide a critical food resource for hatch-year sandpipers beginning their first migration.  相似文献