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1.
With the increasing adoption of the surface mining of coal, problems associated with spoil pile instability, which affects
resource recovery, mining cost, and safety and presents environmental hazards, have become a matter of prime concern to mine
planners and operators. The study of geotechnical aspects is thus very important in the rational planning for the disposal,
reclamation, treatment and utilization of spoil material. A strip coal mine, one of the largest open pit mines in Turkey,
is located in Central Anatolia and provides coal to a thermal power station. Coal production is carried out in two adjacent
open pits, the Central Pit and South Pit. A large-scale spoil pile instability over an area of 0.3 km2 occurred within the dumping area of the Central pit. In addition, small-scale movement occurred in the outside dumping area.
This paper outlines the results of field and laboratory investigations to describe the mechanisms of the spoil pile instabilities
and to assess deformations monitored over a long period following the failure. Shear test results indicate that the interface
between the floor and spoil material dumped by dragline has a negligible cohesion and is the most critical plane of weakness
for spoil pile instability. Back analyses based on the method of limit equilibrium and the numerical modelling technique,
and observations in the pit revealed that failure occurred along a combined sliding surface consisting of a circular surface
through the spoil material itself and a planar surface passing along the interface between the spoil piles and floor. The
analyses also indicated that pore water pressure ratios of about 0.25 satisfy limiting equilibrium condition and that rainfall
about one month before the failure may be a contributing factor to the instability. Movement monitoring data obtained following
the failure over a 1.5-year period suggested that the ongoing deformations were mainly due to compaction of the spoil material.
Based on the monitoring data and the results of the analyses, the failure mode of the local instability occurring at the outside
dumping area was considerably similar to that of the large instability. 相似文献
2.
Analytical solutions are developed for the prediction of the load–settlement response of a compressible axially loaded cast in situ pile in rock. The principal input parameters are derived from the τ–z curve which applies to the contact zone between the pile shaft and the embedment material. For larger diameter piles in rock, these τ–z curves can differ markedly from curves that apply to piles in clay and may include a significant strain hardening region prior to reaching peak strength. In addition to the complete analyses which would normally require the use of a computer, simplified solutions suitable for hand calculations have been derived for the peak load and the pile head displacement to peak. An example of the application of these simplified design calculations is presented. 相似文献
3.
We examined the effects of dredged material disposal on benthic macroinvertebrates in Galveston Bay, Texas, USA, while investigating the utility of estimating secondary production with estimation methods that have less rigorous data requirements than most classical techniques. Production estimates were compared to estimates of benthic consumption by blue crabs, shrimp, and epibenthic fish. There was no evidence that dredged material disposal had a detrimental impact on benthic production; however, production was low throughout the entire bay the year following dredged material disposal, which may have obscured an assessment of the impact of disposal. In fact, disposal sites yielded both the highest production estimates and species richness in both the upper and lower bay areas 2 yr after disposal. Of the five estimation methods used, two that incorporated environmental parameters (temperature and depth) yielded similar and moderate results, ranging from 1.1 g ash-free dry weight m2 yr1 to 26.9 g ash-free dry weight (AFDW) m?2 yr?1 over the 4 yr studied. Daily food ration estimates applied to fishery-independent trawl-survey data yielded overall benthic consumption estimates ranging from 1.1 g AFDW m?2 to 1.7 g AFDW m?2. A second method of estimating consumption, which used transfer efficiency estimates and annual fisheries statistics produced slightly lower benthic consumption estimates (0.72–1.13 g AFDW m?2). The average consumption estimate exceeded benthic production in the upper bay in one of the 4 yr for which benthic production was estimated. In years with high benthic production, the estimated benthic food requirement of epibenthic predators was roughly 10–15% of benthic production. Variation in annual benthic production estimates was two to three times greater than the variation in consumption estimates. 相似文献
4.
This paper presents the main results from an investigation into the slope stability of unsaturated waste rock piles with various configurations and surface recharge conditions. The analyses first consider waste rock piles with different internal and external configurations, under steady-state conditions to evaluate the effect of the pile geometry on the factor of safety. Transient analyses are then conducted to evaluate the influence of rainfalls of different intensities and durations. For six waste rock pile configurations, the results illustrate how the external geometry of the pile influences the factor of safety. The results presented here show how surface infiltration (water recharge), external geometry, and internal pile features affect unsaturated water flow, pore water pressure (matric suction), and material strength, which in turn influence slope stability. Despite the relatively large imposed recharges, following major precipitation events, the results indicate that the decrease of the factor of safety FS is relatively small when compared with the effect of other influential factors. The results also demonstrate that the external geometry of the waste rock pile has the most significant impact on the factor of safety, indicating that pile stability can be controlled with an appropriate design. Waste rock piles with a uniform slope (single bench) should be avoided as this construction method leads to the lowest factor of safety. The overall results clearly demonstrate that the best way to improve the stability of waste rock piles is to use a design and construction method with benches of limited size.
相似文献5.
Summary Slope stability problems exist within the Appalachian Basin as a result of the emplacement of coal mine waste materials on mine outslopes. Prevention or elimination of slope instability problems can be costly. In an attempt to test alternative methods of slope stabilization, the United States Bureau of Mines determined some physical characteristics and shear strengths of ungrouted and polyurethenegrouted samples of coal refuse, coal spoil and natural soils collected at a number of mine outslope sites in Pennsylvania and West Virginia. The particle size distribution, per cent field porosity, per cent field water content and shear strengths of the materials were determined in the laboratory. Fifty drained direct shear strength tests were performed with the sample materials using a 0.06 m3 shear box. Tests were done at field moisture, 100% saturation and grout-infused conditions. Normal loads of 103 kN m–2, 206 kN m–2 and 416 kN m–2 were used. The grout-infused tests generally showed strength increases. An infinite slope model was used to demonstrate the potential effectiveness ofin situ grouting for a variety of field slope conditions. This modelling suggests thatin situ grouting has the potential of stabilizing slopes of up to 35° at depths of 14 m for refuse material and 30° at depths of 5 m for spoil and soil materials. The validity of these increases in material strength by grout injection will require field testing for confirmation. 相似文献
6.
A field experiment is being carried out at the Diavik diamond mine in northern Canada to investigate the influence of unsaturated flow behavior on the quality of drainage from mine waste rock piles in a region of continuous permafrost. This paper is part of a series describing processes affecting the weathering of waste rock and transport of reaction products at this site; here the focus is on unsaturated water flow and its role in mass loading. Two 15 m-high instrumented test piles have been built on 60 m by 50 m collection systems, each consisting of lysimeters and a large impermeable high-density polyethylene (HDPE) liner. Collection lysimeters are installed nearby to investigate infiltration in the upper 2 m of the waste rock. Porosity, water retention curves, and hydraulic conductivity functions are estimated from field measurements and for samples ranging in size from 200 cm3 to 16 m3. Net infiltration in 2007 is estimated to have been 37% of the rainfall for mean annual rainfall conditions. Early-season infiltration freezes and is remobilized as the waste rock thaws. Wetting fronts migrate at rates of 0.2–0.4 m d−1 in response to common rainfall events and up to 5 m d−1 in response to intense rainfall. Pore water and non-reactive solutes travel at rates of <10−2 to 3 × 10−2 m d−1 in response to common rainfall events and up to 0.7 m d−1 in response to intense rainfall. Time-varying SO4 mass loading from the base of the test piles is dictated primarily by the flow behavior, rather than by changes in solute concentrations. 相似文献
7.
Cross-valley fills composed cf waste rock from mining operations pose environmental concerns related to their long-term stability. A large (2.06×107 m3) phosphate waste dump in southeastern Idaho was monitored from 1981 to 1988 for subsidence and horizontal displacement in conjunction with different surficial rock types and long-term precipitation patterns. Most of the 19 surveyed benchmarks on the dump face moved in the northeast direction during the 7-yr study period, roughly the same orientation as the aspect of the fill face. Average vertical subsidence rate decreased exponentially with time from a high of 0.15 m/yr in 1981–1982 to a fairly stable level of 0.008 m/yr by 1988. Net displacement similarly decreased from 0.19 m/yr shortly after dump construction to 0.023 m/yr by 1988. Both subsidence and net displacement were initially higher in the shale cap on the west side of the chert-filled dump; however, by 1986–1988 subsidence and displacement rates were actually lower in the shale material. Subsidence and net displacement appeared unaffected by temporal precipitation patterns; both subsidence and net displacement rates declined significantly during the very wet snowmelt seasons of 1983 and 1984. The temporal patterns of movement at the dump site suggest that the breakdown of the rock (especially shale) occurs primarily during the first 1.5 yr following dump construction. Periodic saturation of the upper 6 m of spoil occurred in nine of 60 neutron access tubes, normally during the spring snowmelt seasons. Saturation occurred at depths 1.8 m and is thought to be associated with uneven compaction or heterogeneities in the fill. Overall, the dump appeared to be internally well drained with rates of rock creep unaffected by seasonal water inputs. 相似文献
8.
Pinki Hazarika Amrita Yadav Sukanta Roy 《Journal of the Geological Society of India》2017,90(6):728-732
The Koyna region located in the west coast of India is a classic example of reservoir triggered seismicity (RTS) that started soon after the impoundment of the Koyna reservoir in 1962. Previous studies have shown that RTS can be explained in terms of stress and pore pressure changes due to poroelastic response of the rock matrix. The permeability of rock matrix is a key parameter for pore pressure diffusion which is mainly responsible for generation of stress perturbation related to seismicity. Based on the poroelastic theory, we employ 2-D finite element models to simulate the evolution of pore pressure up to 5 years after the reservoir impoundment in 1962, using a range in permeability, 10?16–10?14 m2. Constraints on material properties of Deccan basalt and granitic rocks were taken from available studies. The results show the formation of pore pressure front and its propagation with depth and time since the reservoir impoundment as a function of permeability. While a permeability of 10?16 m2 does not produce any significant change in pore pressure, a ten-fold increase in permeability produces significant changes up to a depth of 2 km only beneath the reservoir after 5 years of impoundment. Permeability values between 10?15 m2 and 10?14 m2 are required to induce critical pore pressure changes in the range 0.1–1 MPa up to depth of 10 km, capable of triggering earthquakes in a critically stressed region. Studies on core samples of granitic basement rock down to a depth of 1522 m in the Koyna region provide evidences of fracture zones that may contribute to water channelization. Direct measurements of material properties through the ongoing deep drilling programme would help to develop more realistic models of RTS. 相似文献
9.
The formation of colloids during the weathering of phyllite was investigated by exposing ground phyllite to Milli-Q water. Secondary mineral colloids of 101–102 nm were detected in significant concentrations. At pH of about 8.5, the solution concentration of these colloids reached up to 10 mg/L (however, acidification to pH 4.0 prevented the formation of the colloids). The mineralogical composition of the secondary mineral colloids is assumed to be a mixture of ferrihydrite, manganese oxyhydroxides, aluminosilicates, amorphous Al(OH)3 and gibbsite with possible additions of iron silicates and␣iron-alumino silicates. The colloids were stable over longer periods of time (at least several weeks), even in the presence of suspended ground rock. Direct formation of iron-containing secondary mineral colloids at the rock–water interface by the weathering of rock material is an alternative to the well-known mechanism of iron colloid formation in the bulk of water bodies by mixing of different waters or by aeration of anoxic waters. This direct mechanism is of relevance for colloid production during the weathering of freshly crushed rock in the unsaturated zone as for instance crushed rock in mine waste rock piles. Colloids produced by this mechanism, too, can influence the transport of contaminants such as actinides because these colloids have a large specific surface area and a high sorption affinity. 相似文献
10.
《Applied Geochemistry》2006,21(2):377-403
Predictions of mine-related water pollution are often based on laboratory assays of mine-site material. However, many of the factors that control the rate of element release from a site, such as pH, water–rock ratio, the presence of secondary minerals, particle size, and the relative roles of surface-kinetic and mineral equilibria processes can exhibit considerable variation between small-scale laboratory experiments and large-scale field sites.Monthly monitoring of mine effluent and analysis of natural geological material from four very different mine sites have been used to determine the factors that control the rate of element release and mineral sources and sinks for major elements and for the contaminant metals Zn, Pb, and Cu. The sites are: a coal spoil tip; a limestone-hosted Pb mine, abandoned for the last 200 a; a coal mine; and a slate-hosted Cu mine that was abandoned 150 a ago. Hydrogeological analysis of these sites has been performed to allow field fluxes of elements suitable for comparison with laboratory results to be calculated. Hydrogeological and mineral equilibrium control of element fluxes are common at the field sites, far more so than in laboratory studies. This is attributed to long residence times and low water–rock ratios at the field sites. The high water storativity at many mine sites, and the formation of soluble secondary minerals that can efficiently adsorb metals onto their surfaces provides a large potential source of pollution. This can be released rapidly if conditions change significantly, as in, for example, the case of flooding or disturbance. 相似文献
11.
Rock socketed piles have a number of features which differentiate them from other types of piles. The generally stubby geometry leads to more even distribution of capacity between shaft and base. However, the low ratio of pile modulus to rock modulus leads to high compressibility and this, coupled with a tendency for the load transfer response along the shaft to exhibit strain-softening, gives rise to an overall response where the shaft capacity may be fully mobilized, and potentially degraded, before significant mobilization of base load. The paper presents results of finite element analyses of the response of rock-socketed piles, with particular attention to the shaft response with and without intimate base contact. The shaft interface uses a model, developed from principles of tribology, that includes dilation (and strain-hardening) prior to peak shaft friction, followed by strain-softening at larger displacements. The results of the study are shown to be consistent with field measurements, and to capture effects of the absolute pile diameter on the peak shaft friction. It is also shown that intimate base contact mitigates significantly the degree of strain-softening of the shaft response. 相似文献
12.
为探究砾石对工程堆积体土壤侵蚀的影响与其作用机制,通过室内模拟降雨研究了连续降雨下不同砾石含量的重壤质堆积体水蚀过程。结果表明:①堆积体砾石含量增加,坡面产流历时延长,产流率线性减小,土壤剥蚀率降低;②连续降雨下,堆积体所含砾石主要通过对坡面产流历时、坡面产流率、砾石覆盖率的多重影响发挥减沙作用,主成分回归方程可表达多个变量与平均土壤剥蚀率的关系;③一定砾石含量下,堆积体坡面砾石覆盖率随表土的剥离而增大,导致土壤剥蚀率呈指数函数递减趋势,并与累积土壤侵蚀总量存在较好的函数关系。工程堆积体所含砾石对土壤侵蚀程度的削减可为生产建设项目下垫面水土保持治理提供重要参考。 相似文献
13.
C.O. Okagbue 《Engineering Geology》1986,22(4):317-333
Spoil piles in coal mine areas in north-central West Virginia suffer from numerous landslide problems. An investigation to determine the causes of these slides showed that the stratigraphic composition, the nature of the foundation soils, the seasonal high water table and the mining technique contributed to the instability. The presence of red shales is identified as a key problem.
Several models of failure were investigated based on inclinometer data. These data suggest that multiple failure surfaces may develop in spoil piles. In such cases, the initial failure surface is better defined than other movement surfaces, which either represent subsequent failures that occur in response to placement of additional spoil materials, or are shear zones of readjustment following initial failure. Results show that failures are most likely initiated along the spoil-natural ground interface and propagate slowly into the spoil mass. 相似文献
14.
Kaneohe Bay, Hawaii, is an estuary used as a harbor for a military installation and for recreation, fishing, and research
purposes. Rapid shoaling of the bay had been reported and attributed to increased stream erosion and sedimentation from the
newly suburbanized watershed. Comparison of a 1976 bathymetric survey of Kaneohe Bay with that of a 1927 survey indicates
an average shoaling of the lagoonal area of 1.0 m. Average shoaling for the north and middle bay at 0.6m/49 years (1.2 cm
yr−1 is lower than for the south bay at 1.5m/49 years (3.1 cm yr−1). The total lagoonal fill in the 49-year period is about 1.95× 107 m3, assigned as follows: 64% carbonate detritus from the reefs as well as growth of living coral and unrecorded dredging spill,
9% recorded dredging spoils, and only 27% terrigenous sediment. Seismic reflection profiles distinguish spoil from natural
sediment and show that the infilling sediment is trapped between, burying reef structures built during Quaternary lower stands
of the sea. There had been little obvious change between 1882 and 1927 surveys. All information suggests that increased shoaling
rates since 1927 are due to reported and unreported disposal of dredge spoil, mainly from 1939 to 1945 for ship and seaplane
channels in the south bay, and not from increased runoff and urbanization around the south bay.
Hawaii Institute of Geophysics Contribution No. 1257. 相似文献
15.
Lai Qiyi Zhao Jianjun Huang Runqiu Wang Dujiang Ju Nengpan Li Qingmiao Wang Yunsheng Xu Qiang Zhao Weihua 《Landslides》2022,19(2):331-349
The Chada rock avalanche is a prehistoric high-elevation giant rock landslide located in the Boshula Mountains, Lhorong County, Southeast Tibet. It is composed of conglomerates with a volume of 6.62?×?106 m3 and has a height difference of 1450 m and a transport distance of 3155 m. The accumulational landform shows characteristics indicating rock avalanches. With a unique red conglomerate as the marker of landslide movement, we combined the results of geological surveys, aerial surveys, and engineering geological drilling to determine the entrainment and geomorphic features of the rock avalanche. The rock avalanche was divided into the main scarp, entrainment zone (residual deposit, mixed deposit, and impact fragmentation areas), transport zone (compressed, local landslide, and longitudinal ridge areas), and deposit zone. The sequence of deposits in the valley indicates that the rock avalanche formed before the first-stage terrace and after the second-stage terrace. Combined with 3D numerical simulation, four movement stages were obtained: (1) the rock mass was broken and disintegrated due to progressive failure, initiating high-speed sliding; (2) the sliding mass scraped the thick previous slope material and formed oblique ridges by forward extrusion and lateral friction; (3) the 4.95?×?106 m3 sliding mass was compressed and decelerated to form bending ridges, and the 1.67?×?106 m3 sliding mass continued to move through the channel; and (4) the sliding mass extended to form longitudinal ridges in the channel and hummocks in the valley. The rock avalanche accelerated three times and decelerated three times during its motion.
相似文献16.
注浆技术在治理烧变岩区煤层涌水中的应用 总被引：1，自引：0，他引：1
烧变岩储水空间开阔,补泄通畅,富水性强,是陕北侏罗纪煤田采煤区特殊而重要的含水层。基于火烧区分布范围、烧变岩物性特征和矿井主斜井涌水特征的研究,总结出其涌水规律。根据井巷布置和涌水特征,认为对烧变岩区煤层涌水的治理应采取井下注浆和地面注浆相结合的方法,并对各种方法在注浆时注浆孔的布局、结构,注浆材料及其配方、注浆参数等进行了详细说明。注浆效果显示：主斜井、1^#副斜井井壁进行壁后注浆处理后．井壁涌水量控制到3m^3／h以下,封水效果明显;3^-1煤中央胶运大巷及辅运大巷进行超前预注浆后,巷道出水量一直控制在50m^3／h以下．从而保证了巷道掘进的正常进行。顺利的通过了火烧区的富水段。 相似文献
17.
Shipping activities in the Port of New York-New Jersey are currently threatened by restrictions on dredging of navigational channels and private berthing areas becaused of concerns about the environmental effects caused by ocean disposal of the dredged material. Current proposals for solutions to the problem include ocean disposal of uncontaminated material, use of confined disposal facilities (both upland facilities and containment islands), subaqueous barrow pits, and processing and treatment for contaminated materials. A project to produce a complete “treatment train” for processing and decontaminating dredged material is described. The work is divided into several phases: treatability studies of commercial and nonproprietary technologies at volumes of 19 liters (bench scale) and up to 19 m3 (pilot scale); specification of a treatment train; and implementation of a large-scale facility that can process 76,000–382,000 m3 of dredged material per year. The goal is to achieve operational status for the facility by the end of 1999. 相似文献
18.
Ireland has large water resources. Only 5.3% of developable waters are as yet developed, to supply some 650 I/day/per capita to the population of some 3.37 million people. State of development varies in each of the seven water resources regions. Precipitation is fairly evenly distributed over the year, but the percentage infiltrating to form groundwater varies quite sharply. Some 61% of infiltration occurs in the four winter months November to February, when agricultural activities are low. Only 10% infiltrates in the four summer months, May to August, when agricultural activities are high. In all, annual groundwater amounts to some 24.8 km3, of which 50% is considered to be recoverable. Capital groundwater reserves must be large, but are unquantified. Under these conditions, the impact of agriculture on groundwater quantities is negligible. Of the annual extraction of some 170 × 106m3 of groundwater, some 66 × 106m3/year are used in different agricultural activities. Drainage operations, however, have effects on Irish groundwater. Such lands may overlie impermeable strata or pans, or may receive concealed or visible groundwater discharge. Their drainage will affect the groundwater in various ways. There has been a considerable impact of agriculture on groundwater quality. The effects on the atmosphere and on precipitation are not identifiable. Effects of diffuse infiltration are treated with respect to: (a) application of ground limestone (lime); (b) application of K.N.P. inorganic fertilizer; (c) spreading of organic slurries; (d) development of organic nitrogen in soils, mainly after ploughing of grasslands; and (e) residues from herbicides, fungicides, and pesticides. The infiltration of these substances spread on the land is closely related to the interaction between times of ground-water recharge and times of fertilizer application. Effects of concentrated infiltration are treated under seven sub-heads: (a) infiltration of polluted surface waters; (b) localized farm infiltration; (c) concentrated waste disposal from feedlots; (d) concentrated waste disposal from silage; (e) concentrated waste disposal from agro-industries; (f) disposal through sinkholes and quarries; and (g) disposal by deep well injection. These operations are deliberate, and not related to times of groundwater recharge. They are often into the limestone aquifers, and so doubly dangerous. 相似文献
19.
Alex L. Croft Lynn A. Leonard Troy D. Alphin Lawrence B. Cahoon Martin H. Posey 《Estuaries and Coasts》2006,29(5):737-750
The objective of this study was to determine if the placement of dredged material on sediment-starved back barrier marshes
in southeastern North Carolina could offset submergence without negatively affecting function. Clean sediment was placed in
thickness from 0 to 10 cm, on deteriorated and non-deteriorated marsh plots. Original stem densities were greater, in non-deteriorated
plots (256 stems m−2) compared to deteriorated sites (149 stems m−2). By the second growing season (after sediment additions), stem densities in the deteriorated plots (308 stems m−2) approached levels in the non-deteriorated plots (336 stems m−2). Sediment additions to, both nos-deteriorated and deteriorated plots resulted in a higher redox potential with plots receiving
the most sediment exhibiting the highest Eh values. In deteriorated plots, placement of dredged material had the greatest effect on plant density, but also affected
soil oxidation-reduction potential and sediment deposition (or mobility). Following sediment placement, substrate texture
and composition incrementally returned to prefill conditions due to a combination of bioturbation and sedimentation. Where
infaunal differences occurred, they were generally less abundant in deteriorated plots, but responses to sediment addition
were variable. Sediment addition had little effect on the non-deteriorated plots, suggesting that the disposal of certain
types of dredged material in marshes may be useful to mitigate the effects of marsh degradation without adversely affecting
non-deteriorating marsh. 相似文献
20.
《Applied Geochemistry》2001,16(13):1481-1497
The maximum contents of Pb (360 mg l−1), Zn (360 mg l−1) and Ag (7.9 mg l−1) in formation waters from the Alberta basin were high enough to suggest that it would be of interest to test the concept of recovering these metals by passing natural gas through the water, thereby precipitating the metal sulphides as the result of contact with hydrogen sulphide. The idea was to see if these metals could be recovered from formation water co-produced with crude oil prior to disposal of the water in deep formations, with the possibility of the sale of the metals partially offsetting the cost of disposal. It was proposed to use natural gas with a relatively small amount of hydrogen sulphide (insufficient for sulphur recovery) that must be removed by flaring before the gas is utilized. Accordingly, a database of 694 formation waters with major, minor and trace components was searched for appropriate analyses for detailed study. Of the nine analyses selected the majority were from Devonian and Granite Wash aquifers in the Peace River Arch area of northern Alberta, Canada. Modelling with PATH.ARC showed that there is a consistent set and order of precipitation reactions, in spite of the differences among the formation waters. As would be expected intuitively, acid gas addition makes the formation water more acidic, and metallic sulphide minerals are precipitated. Depending on the initial composition, the end minerals are any of galena, sphalerite, acanthite, covellite and pyrite. These are the minerals that must be beneficiated to recover the metals. A preliminary evaluation of the dollar value of the recovered metals shows that although the absolute values are low, there may be an advantage to recovering the metals if the waters are already being handled at the surface. 相似文献