再生水干湿交替入渗过程中添加碳源对包气带脱氮的影响

干湿交替的回灌方法常被用于解决再生水地表回灌的堵塞问题,但干湿交替回灌可能造成硝态氮被淋洗进入地下水.通过室内土柱模拟入渗实验,对比研究了以葡萄糖作为碳源的低碳氮比再生水干湿交替回灌、干期前蒸馏水淋洗、干期前添加甲醇溶液和干期后添加甲醇溶液4种条件下对包气带氮素迁移转化和脱氮效果的影响.实验表明,对于碳氮比为2.5∶1...     

土建筑遗址干湿耐久性研究

选择新疆交河故城原状生土试样和重塑土试样进行了干湿循环试验,之后进行了风洞试验和强度试验,研究土建筑的干湿耐久性。试验结果表明,在试样原始含水率比较低的情况下,试样首先经历了一个质量增大的过程,3个干湿循环后,试样的质量变化进入一个相对稳定的范围。随着增湿与脱湿过程中伴随的水分质量的变化,试样质量的整体趋势是减小的。随干湿循环次数增大,原状试样的强度减小,风蚀量增大,即耐久性持续变差。相反,随干湿循环次数增大,重塑样的强度反而增大,风蚀量减小,即耐久性有所提高。重塑样由于重塑过程中其微观结构受到破坏,强度弱化。干湿循环在某种意义上对重塑土起到“陈化作用”,愈合损伤的微结构。初期重塑土强度随干湿循环次数的增加逐渐增强,而后强度逐渐衰减抗风蚀能力减弱。     

Positivity-preserving high order well-balanced discontinuous Galerkin methods for the shallow water equations

Shallow water equations with a non-flat bottom topography have been widely used to model flows in rivers and coastal areas. An important difficulty arising in these simulations is the appearance of dry areas where no water is present, as standard numerical methods may fail in the presence of these areas. These equations also have still water steady state solutions in which the flux gradients are nonzero but exactly balanced by the source term. In this paper we propose a high order discontinuous Galerkin method which can maintain the still water steady state exactly, and at the same time can preserve the non-negativity of the water height without loss of mass conservation. A simple positivity-preserving limiter, valid under suitable CFL condition, will be introduced in one dimension and then extended to two dimensions with rectangular meshes. Numerical tests are performed to verify the positivity-preserving property, well-balanced property, high order accuracy, and good resolution for smooth and discontinuous solutions.     

废弃水基钻井液低温干燥处理实验研究及经济性评价

废弃水基钻井液是石油钻井工程作业过程中的废弃物,若直接排放,不但会使钻井液成本居高不下,而且还会对环境造成极为不利的影响。对废弃水基钻井液进行低温干燥处理后再利用,是既经济又符合现代发展趋势的处理方法之一。通过对聚合物钻井液体系、磺化钻井液体系及四川2口页岩气井钻井液体系低温干燥技术实验研究及经济性评价,结果表明：聚合物钻井液体系在120℃条件下干燥处理后性能恶化严重,降低干燥温度能降低其恶化程度;磺化钻井液体系及四川2口页岩气井钻井液体系在120℃条件下干燥处理后性能基本保持不变。这说明低温干燥处理技术能够实现废弃水基钻井液回收再利用,且处理成本低,处理后固体物质便于储存与运输,能够大幅降低钻井液成本。同时,还能够减少废弃钻井液排放量,降低石油钻井工程污染环境的风险。     

四川盆地龙马溪组页岩孔隙度实验方法分析

孔隙度是页岩气藏勘探、评价的关键参数,快速、准确测定页岩孔隙度对于储量计算至关重要。目前有氦气法、液体饱和法、图像分析法应用于页岩孔隙度测定,但方法间、实验室间比对效果欠佳。本文选取69件四川盆地下志留统龙马溪组页岩样品,应用X射线衍射、氩离子抛光-扫描电镜、压汞-氮气吸附等分析测试技术研究样品特征,开展方法间的孔隙度测定比对实验,分析各方法的适用性。结果表明：①龙马溪组页岩黏土含量高、有机质孔隙多、孔喉细小、渗流能力差,导致了外来液体和气体难以快速进入孔隙中,对岩心图像资料的分辨率有很高要求;②液体饱和法(酒精法)使用20MPa压力饱和样品24h,导致了岩心损伤,测得的孔隙度偏离真实值;图像分析法因忽略了矿物基质中的微孔(孔径 < 2nm)和介孔(孔径 < 50nm)等因素使孔隙度测定结果不可靠;③氦气法孔隙度测定结果与烘干温度、稳定时间密切相关,温度越高则测得的孔隙度越大,稳定时间过短会使孔隙度结果偏小。在60℃下烘干岩心24h以上至恒重状态后,通过设置合理的稳定时间,氦气法可获得准确的孔隙度结果,适当提高注入压力有助于加快实验速率。     

Measurements and calculations of seasonal evaporation rate from bare sandstone surfaces: Implications for rock weathering

Evaporation from porous rock plays an important role in weathering processes. In the case of salt weathering, the evaporation rate controls supersaturation of salt solutions within pores and the amount of precipitated aggressive salts, therefore weathering occurs mostly in places with intense evaporation. Evaporation also strongly affects frost, hydric and biogenic weathering, as these are influenced by water content and its temporal changes. Despite its importance, evaporation from porous rocks has seen little scientific focus. We present a study on evaporation from bare sandstone, one of the most common rocks affected by weathering. A new method that measures the evaporation rate from the surfaces of sandstone samples under field microclimate was developed and tested. Also, a simple calculation of 1D evaporation rate from bare sandstone surfaces based on Fick's law of diffusion is presented. The measurement was performed using sandstone cores (with a set depth of the vaporization plane) in a humid continental climate and measured on a roughly monthly interval for about 1 year. For the calculations, a laboratory-measured water-vapour diffusion coefficient of the sandstone, in-situ seasonally measured vaporization plane depth, and values of air humidity and temperature were used. The sensitivity analyses showed that the most important factor controlling the evaporation rate was the vaporization plane depth, while seasonal and spatial changes of air humidity and temperature were of lesser importance. The calculated evaporation rate reasonably follows measured values. For its simplicity and the small number of parameters required, the proposed method has the potential to improve knowledge of weathering and living conditions of endolithic and epilithic organisms. Further research should focus on factors affecting the evaporation rate (wind, hygroscopicity, hydrophobicity, etc.) to improve the accuracy of the calculations, as well as to test the applicability of the method for other lithologies and climates. © 2020 John Wiley & Sons, Ltd.     

Influence of cyclic wetting and drying on swelling behavior of mudstone in south west of Iran

Mudstone experience periodic swell and shrink behavior due to alternate wetting and drying cycles at arid and semi-arid regions with distinctive seasonal changes. This paper examines the influence of cyclic wetting and drying on swelling strain and swelling pressure to simulate the behavior of such rocks under heavy structures (such as building foundations) and behind the stiff support systems (such as concrete linings). Mudstone samples from Bakhtiari formation of Masjed-Soleiman region in south west of Iran were chosen to perform the laboratory tests. The swelling strain under different dead pressures and also swelling pressure under oedometeric condition were measured over time. The maximum swelling strain and pressure increased with each cycle but it had a bound. Increasing the number of wetting and drying cycles reduces the time required to reach ultimate swelling of mudstone. This is a very important conclusion which helps to determine ultimate swelling behavior in a faster way as opposed to performing standard swelling tests for very long periods. The laboratory’s results are also in good correspondence with field measurements.     

东亚冬季风演变和亚洲内陆干旱化信号的多尺度分析

对中国灵台黄土剖面1MaB.P.粒度时间序列和赵家川剖面3.6Ma风尘通量时间序列进行经验模态分解,探讨东亚冬季风和亚洲内陆干旱化的演变特征,发现,1)1MaB.P.以来,东亚冬季风波动主要周期是100ka,40ka和20ka,其中100ka的周期为主导周期;2)在100ka,40ka和20ka周期即偏心率周期、黄赤交...     

温度对藨草(Scirpus triqueter)分解的影响

在5℃、15℃和25℃温度下,研究蔗草(Scirpus triqueter)烘干样品和鲜样品的分解状况,探讨夏季受淹死亡的藨草分解动态及其与正常凋落物分解的差异.结果表明,5个月后,25℃处理下,藨草剩余干物质质量分别为初始时的31.20％(烘干样品)和19.30％(鲜样品);5℃处理下,蔗草剩余干物质质量分别为初始时的65.15％(烘干样品)和62.12％(鲜样品);25℃处理下的蔗草剩余干物质质量明显低于5℃处理下的蔗草剩余干物质质量;藨草的前处理亦会影响其分解过程,在5℃和15℃处理下,藨草鲜样品在前期的分解速度低于藨草烘干样品,但它们后期的分解速度无明显差别,而在25℃处理下,蔗草鲜样品的分解速度明显大于烘干样品.因此,在夏季丰水期,具有明显水文动态的河流中的矮小水生植物,在受淹死亡后,其分解速度较快,能对生态系统的物质循环和水质环境产生影响.     

羊庄盆地土壤水分变化规律研究

羊庄盆地地下水资源丰富,是枣庄市和滕州市的主要供水水源之一。该文采用中子法和烘干法相结合的监测方法,对羊庄盆地不同位置、不同深度和不同时间段的土壤水分进行了监测,分析了土壤水分在空间和时间上的变化规律;土壤水分监测为求取有关水文地质参数和地下水资源评价提供了基础性数据。