Transport behavior of nZnO in geosynthetic clay liner used in municipal solid waste landfills under temperature effect

The transport process of nZnO in geosynthetic clay liner (GCL), an anti-seepage material used in municipal solid waste (MSW) landfills, under different seepage temperature conditions was conducted. The transport behavior of nZnO in GCL was analyzed. Results showed that the retardation performance of current GCL used in MSW landfills anti-seepage system against nZnO pollutants was poor. nZnO successfully permeated the GCL and entered external soil–groundwater environment, posing health threats to the life of organisms. Although seepage temperature exerted a small effect on nZnO suspension leakage volume, change in seepage temperature affects the mass of transported nZnO in GCL by redispersion of nZnO in suspension. As the seepage temperature increases, the mass of nZnO that permeated the GCL increases, reaching a maximum at 50 °C, and then decreases.     

Hydro-thermal coupled analysis for health monitoring of embankment dams

Measuring and analyzing internal dam temperature may provide insight into evaluating the integrity of earthen dams. Temperature in a dam, with the advent of modern distributed temperature sensing (DTS) technique, is conveniently measured. The analysis of the temperature is conducted based on a hydro-thermal coupled analysis technique. In this study, DTS-based temperature data and VS2DHI (a finite difference code for analyzing two-dimensional heat transport in porous media) were used to analyze the hydro-thermal coupled behavior in a dam. The results of this analysis show that the temperature variation in an earthen dam is closely related to seepage conditions. Additionally, a localized high-temperature (26 °C) zone found in the measured data of the dam, which raised concern to engineers on site, is explained through either hot water infiltration into the foundation layer or lower permeability of the foundation layer than the magnitude that appeared in the design document. These findings demonstrate that hydro-thermal coupled analysis has the potential for evaluating the integrity of earthen dams.     

Characterizing groundwater recharge using oxygen and hydrogen isotopes: a case study in a temperate forested region,South Korea

In the cool temperate region of South Korea, oxygen and hydrogen isotopes of groundwater, lake water, and precipitation were studied to determine the season of groundwater recharge. All the groundwater samples, irrespective of season, on δ¹⁸O–δ²H scale plotted along the summer precipitation, suggesting summer precipitation largely modulates recharge. The deuterium excess values of groundwater (d-excess) show clear seasonal difference, higher in winter (> 18‰) and lower in summer (< 10‰). And its resemblance to the summer precipitation d-excess value further suggests dominant role of summer precipitation in groundwater recharge. Based on the mass balance equation, with end-member d-excess values of seasonal precipitation and groundwater as input variables, groundwater is composed of 66% summer and 34% winter precipitation. Despite the study area being heavily forested, summer rainfall contribution higher than winter suggests that evapotranspiration effect is minimal in the region; may be due to thin sand–gravel-based porous soil overlying highly weathered granitic rock system.     

Comparison between the TOPMODEL and the Xin’anjiang model and their application to rainfall runoff simulation in semi-humid regions

To study the application of the TOPMODEL and the Xin’anjiang model to rainfall runoff simulation in semi-humid regions, the Holtan excess infiltration runoff module was added to the TOPMODEL structure. The basin of the Heihe Jinpen Reservoir in Shaanxi Province, China, was selected as the study area. Rainfall and runoff data and digital elevation models were collected. The watershed topographic parameters and 21 floods that occurred from 2005 to 2013 were obtained to simulate rainfall runoff. Results show that the improved TOPMODEL and the Xin’anjiang model can effectively stimulate rainfall runoff. The average values of their Nash coefficient are 0.84 and 0.83, respectively, upon calibration, and 0.78 and 0.80, respectively, upon validation. The Xin’anjiang model performs slightly better than the improved TOPMODEL. The results of large flood peaks are better than those of ordinary floods. Both results can be used to simulate the rainfall runoff of a watershed.     

Experimental and numerical investigation on coal drawing from thick steep seam with longwall top coal caving mining

Steep coal seam mining activities will frequently occur during the next few decades in China. In this study, both experimental and numerical methods are employed to investigate the coal drawing from thick steep seam with longwall top coal caving mining. A series of analyses is performed to investigate the features of the drawing body, the distribution of top coal recovery ratio and the shape of the rock flow under steep conditions. The results indicate that the drawing body of top coal develops prior to upper side of the panel face obviously, and the top coal in the central part of the panel has a higher recovery ratio than that in the lower and upper parts in steep coal seam with caving mining method. The flow paths of the fragmented top coal are nearly straight lines moving towards the drawing window, and the fastest path maintains a constant angle with the plumb line. The spatial shape of the rock flow indicates “bidirectional asymmetry,” which results from the presence of the shield beam and dip angle of the coal seam; thus, this is the root cause of the appearance of the drawing body’s prior development towards the upper side of the panel. The field observation data indicates the same distribution of top coal recovery as that in the physical experiment and numerical simulation. Furthermore, suggested measurements are proposed to improve top coal recovery in steep seam mining based on the engineering practice of Dayuan coal mine.     

渝东北城口地区Y1井页岩有机地球化学特征及勘探前景

基于钻井资料,以总有机碳(TOC)、干酪根显微组分、等效镜质体反射率(Ro)及碳同位素等测试数据系统分析了渝东北城口地区Y1井五峰组—龙马溪组页岩的有机地球化学特征,利用页岩流体包裹体的显微特征、均一温度及激光拉曼数据深入分析了Y1井页岩气成藏特征。结果表明:Y1井上奥陶统五峰组—下志留统龙马溪组炭质页岩发育,TOC含量2%的富含有机质页岩厚度达83 m,干酪根类型以Ⅰ型干酪根为主,处于湿气生烃阶段。页岩裂缝脉体中大量烃包裹体和富含甲烷气体的含烃盐水包裹体证实城口地区五峰组—龙马溪组页岩发生了充足页岩气供给,具有高均一温度、高盐度的伴生盐水包裹体表明城口地区页岩气成藏时期的保存条件良好。这些Y1井页岩有机地球化学特征研究成果揭示了城口地区下古生界具备良好的页岩气勘探前景。     

贵州省复杂地层地热深井钻探工艺

贵州省地矿局组织实施了“贵州省地热深井钻探技术攻关”项目,研究了喀斯特地区复杂地层情况下地热深井钻探中螺杆钻井工艺和空气钻井工艺的适应性,攻克了两种工艺在该地区应用受地层特性限制的相关技术难题。螺杆马达平均寿命达到200小时以上,螺杆钻井工艺较常规钻井工艺钻进机械钻速提高2～3倍;空气潜孔锤单井应用深度超过1500m,空气潜孔锤钻井工艺较常规钻井工艺机械钻速提高10～29.5倍。同时研究了单井多工艺转换接力钻进技术,以及与上述工艺配套使用的钻井液体系。最终形成了一套适合贵州省地质条件地热深井钻探施工并能显著提高钻井效率和经济效益的组合工艺技术体系。该成果能将1口2000m以上地热深井施工周期由原来的8~12个月缩短至4~6个月,将单井平均施工成本由450万元降低至410万元以下。     

基于MODIS数据的青藏高原冰川反照率时空分布及变化研究

冰川反照率对冰川融化具有重要影响,以2000-2013年MODIS的MOD10A1逐日积雪反照率数据资料为基础,分析了青藏高原冰川反照率的时空分布及变化。结果表明：冰川年平均反照率变化范围是0.42（枪勇冰川）~0.75（PT5冰川）,其中夏季平均反照率变化范围是0.45（来古冰川）~0.69（东绒布冰川和古里雅冰川）。冰川反照率空间分布并没有明显的规律性,而冰川反照率的变化速率空间分布规律明显——南部较大往北减小,北部反照率出现增大现象。研究区内大部分冰川反照率呈波动降低的趋势,年平均反照率和夏季平均反照率变化速率最大值都出现在枪勇冰川,分别是-0.015 a^-1和-0.019 a^-1。木吉和木孜塔格冰川年平均和夏季平均冰川反照率都增大,木吉冰川是由于2012年的高反照率引起的,而木孜塔格冰川主要与该地区气温降低、降水增多有关。     

A review of advances in China’s flash flood early-warning system

This paper summarizes the main flash flood early-warning systems of America, Europe, Japan, and Taiwan China and discusses their advantages and disadvantages. The latest development in flash flood prevention is also presented. China’s flash flood prevention system involves three stages. Herein, the warning methods and achievements in the first two stages are introduced in detail. Based on the worldwide experience of flash flood early-warning systems, the general research idea of the third stage is proposed from the viewpoint of requirements for flash flood prevention and construction progress of the next stage in China. Real-time dynamic warning systems can be applied to the early-warning platform at four levels (central level, provincial level, municipal level, and county level) . Through this, soil moisture, peak flow, and water level can be calculated in real-time using distributed hydrological models, and then flash flood warning indexes can be computed based on defined thresholds of runoff and water level. A compound warning index (CWI) can be applied to regions where rainfall and water level are measured by simple equipment. In this manner, flash-flood-related factors such as rainfall intensity and antecedent and cumulative rainfall depths can be determined using the CWI method. The proposed methodology for the third stage could support flash flood prevention measures in the 13th 5-Year Plan for Economic and Social Development of the People’s Republic of China (2016–2020). The research achievements will serve as a guidance for flash flood monitoring and warning as well as flood warning in medium and small rivers.