卵砾石地层潜孔锤同心跟管钻具的研究

卵砾石地层是钻探工程中常见的一种典型的不稳定地层。通过分析目前在卵砾石地层的钻进方法，并针对这一地层的特点，提出了潜孔锤同心跟管钻具在该地层中应用的可行性，并分析设计了钻具的原理、结构及特点。结合实验结果，认为潜孔锤同心跟管钻具在卵砾石地层中具有广阔的应用前景。     

Characterization of water bursting and discharge into underground mines with multilayered groundwater flow systems in the North China coal basin

A conceptual framework for characterization of water bursting and discharge into underground mines with multilayered groundwater flow systems is presented, based on the features of the site conditions and analyses of the water bursting and mine inundation events of the North China coal basin. Comprehensive analyses of the hydrogeological conditions for establishment of the three-dimensional groundwater flow systems of the North China coal basin revealed different vertical hydraulic connection paths or channels. These connections include karst collapse columns, fault or fracture zones, buried weathering zones, and fracture networks in aquitards, within the multilayered groundwater flow systems. Also examined, was the effect of the primary features of the flow system and those different connection paths on water bursting and discharge into the underground coal mines. It was demonstrated that appropriately identifying and adequately understanding the three-dimensional multilayered groundwater flow systems and those various vertical hydraulic connection mechanisms are critical for appropriately preventing water bursting hazards and predicting water discharge into underground mines. A valuable guideline is presented on characterization of water bursting and discharge into underground mines with multilayered groundwater flow systems.

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Resumen Un cadre de travail conceptuel pour la caractérisation du jaillissement et de la vidange des eaux dans les mines à plusieurs niveaux d'écoulement est présenté, basé sur les conditions et l'analyse sur site du jaillissement des eaux et des inondations dans les bassins charbonneux du Nord de la Chine. L'analyse compréhensive des conditions hydrogéologiques des systèmes d'écoulement tridimensionnel de ces bassins, révèle des trajets ou des chenaux qui sont autant de connections hydrauliques verticales. Ces connections comprennent des effondrement karstiques en colonne, des zones de fractures et de failles, des zones d'altération, des réseaux de fractures dans les aquitards, dans le système hydrogéologique multicouche. L'influence des caractéristiques primaires du système d'écoulement et de ces différentes connections sur le jaillissement et la vidange dans les mines, est également examiné. Il a été démontré que l'identification appropriée et la compréhension adéquate du système d'écoulement souterrain multicouche et tridimensionnel, et des mécanismes variés de connection hydraulique verticale est critiquée pour prévenir de manière appropriée les risques de jaillissement et de vidange dans les mines. Des guidelines valorisables sont présentées, pour la caractérisation du jaillissement et de la vidange dans de tels systèmes.

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Résumé Se presenta un marco conceptual para la de caracterización de la despresurización y descarga de agua a minas subterráneas con sistemas de acuíferos de múltiples niveles, el cual se basa en las condiciones del sitio, análisis de la despresurización de agua e inundaciones de minas en la cuenca de carbón del norte de la China.Un análisis comprehensivo de las condiciones hidrogeológicas para el establecimiento de los sistemas de flujo de agua de tri-dimensionales en la cuenca de carbón del norte de la China ha revelado diferentes canales hidráulicos verticales. Estas conexiones incluyen columnas de karst colapsadas, fallas o zonas de fracturas, zonas de regalita hundida y redes de fracturas en zonas de poca permeabilidad dentro de los sistemas de flujo de múltiples niveles.También se investigó el efecto de los rasgos primarios del sistema de flujo y los diferentes canales conectivos sobre la despresurización y descarga de agua a minas subterráneas. Se demostró que el entendimiento e identificación adecuada de los sistemas de acuíferos de múltiples niveles en tres dimensiones es crítico para prevenir apropiadamente la despresurización y descarga de agua a minas subterráneas. Se presentan lineamientos valiosos en relación con la despresurización y descarga de agua a minas subterráneas en sistemas de flujo de múltiple nivel.

     

科尔沁沙地土地利用与耕作方式对土壤风蚀的影响

土壤风蚀造成的直接生态后果是土地资源的退化。在春播前两次沙尘暴事件中,对科尔沁沙地几种具有代表性的土地类型的土壤风蚀量及土壤特性进行了野外测定、分析,结果表明:(1)在同一沙尘暴天气下,由于土地利用和耕作方式的不同,土壤风蚀量存在着差异,新垦农地和翻耕农地的风蚀量显著高于未垦草地、免耕农地和麻黄地;免耕农地则与未垦草地的风蚀量相差不大,风蚀危害较轻;麻黄地几乎不受风蚀侵害。新垦农地、翻耕农地、免耕农地、未垦草地、麻黄地两次观测的土壤风蚀量平均值依次为24.59、15.60、2.26、1.46和0.22 g/h.cm2。(2)基于土壤特性计算的土壤退化指数结果表明,新垦农地和翻耕农地发生了较为严重的退化。     

Estimating the minimum in-stream flow requirements via wetted perimeter method based on curvature and slope techniques

Under the assumptions of triangular cross section channel and uniform stable flow, an analytical solution of the minimum ecological in-stream flow requirement (MEIFR) is deduced. Based on the analytical solution, the uncertainty of the wetted perimeter method is analyzed by comparing the two techniques for the determination of the critical point on the relationship curve between wetted perimeter, P and discharge, Q. It is clearly shown that the results of MEIFR based on curvature technique (corresponding to the maximum curvature) and slope technique (slope being 1) are significantly different. On the P-Q curve, the slope of the critical point with the maximum curvature is 0.39 and the MEIFR varied prominently with the change of the slope threshold. This indicates that if a certain value of the slope threshold is not available for slope technique, curvature technique may be a better choice. By applying the analytical solution of MEIFR in the losing rivers of the Western Route South-to-North Water Transfer Project in China, the MEIFR value via curvature technique is 2.5%-23.7% of the multi-year average annual discharge, while that for slope technique is 11%-105.7%. General conclusions would rely on the more detailed research for all kinds of cross-sections.     

Palaeovariations in the East-Asian Monsoon Regime Geochemically Recorded in Varved Sediments of Lake Sihailongwan (Northeast China, Jilin Province). Part 1: Hydrological Conditions and Dust Flux

The varved sediments of the dimictic Lake Sihailongwan (Long Gang mountain area, Jilin Province, Northeast China) represent a palaeoclimatic archive which documents the local precipitation frequency during the summer monsoon, and variations in the aeolian flux of dust with their remote sources in the arid and semi-arid regions of inner Asia. Based on a detailed discussion of sediment genesis in Lake SHL, dust flux rates and palaeohydrological conditions were reconstructed on a decadal scale over the past 220 years. The aeolian influx by dry and wet deposition was quantified and characterised in its chemical composition. Photosynthetic production in the lake is positively correlated with the inflow of nutrient-rich groundwater. The groundwater discharge largely reflects the strength of the summer monsoon. Net accumulation rates for biogenic silica were determined for annually laminated sediments from the centre of the U-shaped lake basin based on sediment data. In a Si-balance model of the modern lake, the depositional flux of biogenic silica could be independently quantified on the base of hydrochemical monitoring data. Comparison of the both estimates allowed to asses the focussing of the particle flux in the lake. Though water retention in Lake SHL is rather high (ca. 30 years), changes in the hydrological conditions are sensitively recorded in the sediments because (i) nutrient-rich groundwater discharges into the productive zone of the lake, (ii) a substantial proportion of the total dissolved Si-inventory of the mixed lake (ca. 30%) is annually consumed by diatom growth, and (3) sediment accumulation is substantially focussed towards the flat bottom of the lake basin. The bulk siliciclastic sediment fraction (ca. 75 wt.%) largely originates from influx of dust of remote provenance. In sediment thin-sections, the dry-deposited dust fraction is microscopically identifiable as seasonal silt layer. Aeolian input by wet-deposition shows a distinctly higher variability than the influx of dust by dry-deposition. As diatom production, wet-deposition of dust is positively correlated with the rainfall during the summer monsoon. The inferred positive correlation between rainfall and dust flux during the summer monsoon implies that dust deposition is determined by the out-wash efficiency of mineral particles for a permanent high atmospheric dust concentration over Northeast China in the last 220 years.