湖南煤炭坝矿区岩溶水害特征及防治对策

煤炭坝矿区是全国闻名的大水矿区,矿区最大涌水量已超过12000m^3／h,年排水费用达1．2亿元,吨煤成本达150元,并呈上升趋势,严重影响了煤矿的安全生产。本文在详细论述煤炭坝矿区水文地质特征的基础上提出了切实可行的治理思路,治理方法,并进行了效益预测。对矿区防治水患具有指导性作用。     

Environmental tracers as indicators of karst conduits in groundwater in South Dakota,USA

Environmental tracers sampled from the carbonate Madison aquifer on the eastern flank of the Black Hills, South Dakota, USA indicated the approximate locations of four major karst conduits. Contamination issues are a major concern because these conduits are characterized by direct connections to sinking streams, high groundwater velocities, and proximity to public water supplies. Objectives of the study were to estimate approximate conduit locations and assess possible anthropogenic influences associated with conduits. Anomalies of young groundwater based on chlorofluorocarbons (CFCs), tritium, and electrical conductivity (EC) indicated fast moving, focused flow and thus the likely presence of conduits. δ¹⁸O was useful for determining sources of recharge for each conduit, and nitrate was a useful tracer for assessing flow paths for anthropogenic influences. Two of the four conduits terminate at or near a large spring complex. CFC apparent ages ranged from 15 years near conduits to >50 years in other areas. Nitrate-N concentrations >0.4 mg/L in groundwater were associated with each of the four conduits compared with concentrations ranging from <0.1 to 0.4 mg/L in other areas. These higher nitrate-N concentrations probably do not result from sinking streams but rather from other areas of infiltration.     

Evaluation of distributed recharge in an upland semi-arid karst system: the West Bank Mountain Aquifer,Middle East

Assessment of recharge in a structurally complex upland karst limestone aquifer situated in a semi-arid environment is difficult. Resort to surrogate indicators such as measurement of spring outflow and borehole discharge, is a common alternative, and attempts to apply conventional soil moisture deficit analysis may not adequately account for the intermittent spate conditions that arise in such environments. A modelling approach has been made using the West Bank Mountain Aquifer system in the Middle East as a trial. The model uses object oriented software which allows various objects to be switched on and off. Each of the main recharge processes identified in the West Bank is incorporated. The model allows either conventional soil moisture deficit analysis calculations or wetting threshold calculations to be made as appropriate, and accommodates both direct recharge and secondary recharge. Daily time steps enable recharge and runoff routing to be calculated for each node. Model runs have enabled a series of simulations for each of the three aquifer basins in the West Bank and for the whole of the West Bank. These provide recharge estimates comparable to those prepared by earlier workers by conventional means. The model is adaptable and has been successfully used in other environments.     

Chernobyl radiocaesium in a karst system,Marble Cave,Crimea

 Surface contamination with radioactive caesium introduced into the environment after the accident at the Chernobyl nuclear plant was high enough in the Crimean Mountains to allow using radiocaesium as an indicator of penetration of radioactive contamination into a karst system. Caesium concentrations have been studied in soils above Marble Cave, Tchatyrdag Plateau, in percolation waters and in sediments transported by percolation waters within the cave. Contamination of the daylight surface with ¹³⁷Cs is about 30 kqB m^–2 which is approximately 13 times higher than the density of global fallouts. Besides ¹³⁷Cs, almost all samples showed presence of ¹³⁴Cs with the ¹³⁷Cs/¹³⁴Cs ratio close to that of Chernobyl contaminations. Concentrations of ¹³⁷Cs range from 9 to 15 mBq l^–1 in the present percolation waters in the cave. In sediments related to percolation waters ¹³⁴Cs is detected in some samples besides ¹³⁷Cs, although the effect of ²²⁸Ac is not ruled out. Surprisingly, the highest concentrations of radiocaesium were measured in "old" sediments in the cave's lower series. These sediments are not associated with modern percolation and are represented by a clay/moonmilk alternating sequence deposited in an old dried cave lake. Moonmilk layers have higher caesium content than clay. It is assumed that Chernobyl caesium was transported into the cave with aerosols which were then deposited mainly in areas where condensation occurs. The sampling site is located just in the boundary between two microclimatic zones with a temperature gradient of 0.5  °C. Active condensation processes occur in this area. Caesium was not detected in another similar sampling site (old lake deposits) located within homogeneous microclimatic conditions. If the above interpretation is correct, these results show the geochemical significance of the aerosol-condensation mechanism of mass transport and localisation. Received: 1 June 1995 · Accepted: 4 December 1995     

Sector collapse,sedimentation and clast population evolution at an active island-arc volcano: Stromboli,Italy

Sciara del Fuoco is the subaerial part of a partially filled sector-collapse scar that extends to 700 m below sea level on Stromboli volcano. The collapse occurred <5000 years ago, involved 1.81 km³ of rock and is the latest of a series of major collapses on the north-west flank of Stromboli. A north-east trending arc-axial fault system channels magmas into the volcano and has caused tilting and/or downthrow to the north-west. The slope of the partial cone constructed between the lateral walls of the collapse scar acts as a channelway to the sea for most eruptive products. From 700 m below sea level and extending to >2200 m and >10 km from the shore to the NNW, a fan-shaped mounded feature comprises debris avalanche deposits (>4 km³) from two or more sector collapses. Volcaniclastic density currents originating from Sciara del Fuoco follow the topographic margin of the debris avalanche deposits, although overbank currents and other unconfined currents widely cover the mounded feature with turbidites. Historical (recorded) eruptive activity in Sciara del Fuoco is considerably less than that which occurred earlier, and much of the partial fill may have formed from eruptions soon after the sector collapse. It is possible that a mass of eruptive products similar to that in the collapse scar is dispersed as volcanogenic sediment in deep water of the Tyrhennian basin. Evidence that the early post-collapse eruptive discharge was greater than the apparent recent flux (2kg/s) counters suggestions that a substantial part of Stromboli's growth has been endogenous. The partial fill of Sciaria del Fuoco is dominated by lava and spatter layers, rather than by the scoria and ash layers classically regarded as main constituents of Strombolian (cinder) cones. Much of the volcanic slope beneath the vents is steeper than the angle of repose of loose tephra, which is therefore rapidly transported to the sea. Delicate pyroclasts that record the magmatic explosivity are selectively destroyed and diluted during sedimentary transport, mainly in avalanches and by shoreline wave reworking, and thus the submarine deposits do not record well the extent and diversity of explosive activity and associated clast-forming processes. Considerable amounts of dense (non-vesicular) fine sand and silt grains are produced by breakage and rounding of fragments of lava and agglutinate. The submarine extension of the collapse scar, and the continuing topographic depression to >2200 m below sea level, are zones of considerable by-passing of fine sand and silt, which are transported in turbidity currents. Evidently, volcanogenic sediments dispersed around island volcanoes by density currents are unlikely to record well the true spectrum and relative importance of clast-forming processes that occurred during an eruption. Marine sedimentary evidence of magmatic explosivity is particularly susceptible to partial or complete obliteration, unless there is a high rate of discharge of pyroclastic material into the sea.     

A multivariate statistical and geostatistical study on the geochemistry of allochtonous karst bauxite deposits in Hungary

A geochemical evaluation of the Szc-Halimba-Kisld area, Hungary, covering an area of more than 200 km² is presented using different statistical and geostatistical methods. The study area is a representative example of allochtonous karst bauxite accumulation. The three groups of deposits studied here have been explored and mined since 1950. Several thousand boreholes have been drilled, and bauxite cores were analyzed for the five main chemical components. A total of 80,000 pleces of analytical data were processed, followed by a geological examination of borehole logs and of mining excavations.The quantitative geochemical evaluation of the data set led to both geochemical and practical results: The geochemical behavior of the allochtonous, clastic karst bauxite deposits differs essentially from that of the autochtonous and parautochtonous ones, as well as that of the lateritic bauxite deposits. The deposits of the study area can be split into several subsequent geochemical-sedimentological units, each representing an event of bauxite transport and accumulation. Clear regional patterns can be revealed in the composition of these units. The geostatistically measured chemical variability of the geochemical units is rather different, the lowest units showing the smallest variability. The interrelations of the main chemical components are weaker and more irregular in the studied deposits than in the autochtonous lateritic bauxite deposits. Additional local genetic features, such as transport routes, can be delineated by the methods applied. Within each deposit, local changes of chemical composition and of its variability can be determined more precisely. These results can be used in bauxite prospecting and exploration, because areas of high or low bauxite quality can be predicted.     

Hydrology and hydrogeology of Sakaryabaşı Karstic springs, Çifteler, Turkey

The Sakarya River is one of the largest rivers in Turkey and is fed mainly from Sakaryabaşı springs. The Sakaryabaşı springs are located in the Central Anatolia and issue from confined/semi-confined karst having a thermal component and therefore, having quite different hydrogeological characteristics as compared to the Taurus Karst region, a typical example of the Mediterranean type of karst. The karstic carbonate rocks that form the groundwater reservoir are overlain by a thick semi-pervious overburden of mainly clastics of Neogene age. Tectonics is the major factor controlling the occurrence of the karst springs in the area where topography is rather flat. This study aimed at explaining the occurrence and movement of the karst groundwater within the system by use of hydrogeological, chemical, and isotopic tools. Isotopic composition of the waters revealed that all waters in the region are of meteoric origin and the thermal component is due to deep circulation. The catchment area of the hydrogeological system extends to the south and groundwater movement is towards the outlets, which are in a depression along a major fault. The movement of the groundwater, based on analysis of remotely sensed images, is controlled mainly by structural elements.     

自重湿陷性黄土地区桩基设计探讨

根据自重湿陷性黄土的特点、《湿陷性黄土地区建筑规范》（GB50025—2004）和《建筑桩基技术规范》（JGJ94—94）中关于桩基设计的对比分析，通过自重湿陷性黄土场地工程实例分析计算，依据负摩擦产生的机理——中性点理论，论述了自重湿陷性黄土场地中桩基设计应考虑中性点，而不应全部计入负摩阻的观点。     

Soil quality changes in land degradation as indicated by soil chemical, biochemical and microbiological properties in a karst area of southwest Guizhou, China

Not only the nutritional status and biological activity but also the soil ecological functioning or soil health has been impacted profoundly by land degradation in the karst area of southwest China where the karst ecosystems are generally considered as extremely vulnerable to land degradation under intensified land-use changes. The objectives of this study are to elucidate the changes in overall soil quality by a holistic approach of soil nutritional, biological activity, and soil health indicators in the karst area as impacted by intense cultivation and vegetation degradation. Topsoil samples were collected on selected eco-tesserae in a sequence of land degradation in a karst area of southwest Guizhou in 2004. The soil nutrient pools of organic carbon (C_org), extractable extracellular carbon (C_ext), total soil nitrogen (N_t), alkali-hydrolyzable nitrogen (N_ah), total phosphorus (P_t), available phosphorus (P_a) were analyzed by wet soil chemistry. The soil biological properties were studied by means of measurements of microbial biomass carbon (both by fumigation–extraction, FE-C_mic, and by calculation from substrate-incubation respiration, SIR-C_mic) of respiration [respiration without addition of substrates, basal respiration (BR), and potential respiration (PR) with substrate-incubation] and of soil enzyme activities (invertase, urease, and alkaline phosphatase). Soil health status was assessed by simple indices of C_mic/C_org and BR/C_mic in conjunction with bacterial community structures determined by polymerase chain reaction and denaturing gradient gel electrophoresis. While the nutritional pool parameters, such as C_org and C_ext, described basically the changes in soil life-supporting capacity with cultivation interference and vegetation declined, those parameters of biological activity such as FE-C_mic, SIR, and SIR-C_mic as well as bacterial community structures measured by molecular method evidenced well the changes in soil functioning for ecosystem health with the land degradation.     

Karst groundwater protection in the Kupa River catchment area and sustainable development

One of the most significant water resources in the Republic of Croatia is the catchment area of the Kupa River, located in the region bordering the Republic of Slovenia. About 88% of the total amount of water in this catchment originates in Croatia and just 12% from Slovenia; therefore, the largest part of the catchment area (about 1000 km²) is on the Croatian side of the border. It is a typical karst area of the Dinarides with aquifers characterized by a relatively rapid water exchange, high groundwater flow velocities and aquifers open to human impact from the surface. Consequently, the aquifers are highly vulnerable and at risk. Due to the availability of large quantities of high-quality spring water (about 6 m³/s), the entire area has a strategic importance within the context of any future development strategy pertaining to the western part of Croatia. The catchment area on the Croatian side was investigated using a wide range of research methods that included a classical hydrogeological approach, the detailed hydrologic calculation of water balance to the hydrogeochemical analyses and modelling. The objective was to determine protection zones and protection measures for the whole area. The difficulties are increased due to the fact that the karst catchment area is crossed by major traffic corridors, oil pipelines and a railway and that many settlements and a highly developed wood industry are present. The combination of protecting water resources with adequate prevention measures and necessary remedial activities that should satisfy the very strict requirements necessary for the protection of the karst aquifers while still allowing for present and future human activities is difficult – but not impossible – to achieve. One good example is the present highway with a closed dewatering system and waste water treatment before the water passes into the karst underground system.