Influence of cyclic loading history on small strain shear modulus of saturated clays

Small strain shear modulus G_max is an essential parameter in soil dynamics, and it is usually estimated based on the Hardin and Richart equation. However, many previous researches on sands have indicated that the Hardin and Richart equation does not consider the influences of cyclic loading history on G_max. In this paper, effects of cyclic loading history on G_max of saturated clays under undrained conditions are studied using a combination device of piezoelectric-ceramic bender element system and cyclic triaxial apparatus. The dynamic pre-loading includes both relatively high amplitudes of cyclic stresses and cyclic strains. G_max without cyclic loading history is also investigated for the comparison purpose. Test results show that, at the same effective stress, both cyclic strain history and cyclic stress history will induce reduction of G_max compared to the corresponding G_max values with non-cyclic loading effects. In strain-controlled tests, the reduction of G_max is slight and relatively stable; while in stress-controlled tests, the reduction of G_max increases suddenly and remarkably when the effective stresses degrade to a certain degree. The comparison between double amplitude axial strain and residual excess pore water pressure behaviors show that the remarkable reduction of G_max can demonstrate the cyclic failure of saturated clays.     

Typology of Municipal Wastewater Treatment Technologies in Latin America

This paper presents an analysis of the wastewater treatment plants in six Latin American and Caribbean countries. Based on a sample of 2734 municipal treatment facilities, the applied processes are classified by sizes (influent flow) and type of technologies. The distribution of the technologies is also presented for each of the six countries. In addition, a representative municipal wastewater characterization, based on influent data from 174 treatment plants, is proposed. Results show that stabilization ponds, activated sludge, and the upflow anaerobic sludge blanket reactors represent 80% of the treatment facilities of the sample, providing treatment to 81% of the total flow considered. Moreover, 67% of the plants in the sample are small (flow <25 L/s) and the very small facilities (influent flow <5 L/s) are extensively applied in the region (34% of the sample), especially in Mexico and Brazil. The use of very small treatment plants may result in low energy efficiency systems and on possible incompliance of the discharge standards. This common practice in several countries in Latin America should be revised in order to improve the environmental performance of such facilities.     

地震勘探中小尺度非均匀性的描述及长波长理论

地球物理成像解释的一个重要问题是,地震波传播时其本身受到地质体中小尺度非均匀性的影响,对该问题的研究具有重要的意义且备受关注. 据此,本文首先从统计意义上的表示形式来描述小尺度非均匀性,给出一种拓展了小尺度非均匀性择优取向的随机介质建模新方法,重点阐述了建模过程中对误差处理的重要性. 其次讨论了地震波在水平层状介质中传播时的长波长理论,并指出对该理论的适用条件进行研究的重要意义.且还基于1D随机层状介质,从局部各向异性因子曲线的角度对长波长理论进行了研究,并讨论了密度及泊松比扰动对曲线形态的影响. 最后,从对1D和2D随机介质进行数值模拟的角度重点研究长波长理论不能满足的情况下地震记录的特点,为了便于对比分析,文中也计算了1D随机介质在不同平均化长度下,通过长波长理论得到的等效介质的理论走时(走时的计算是在弱各向异性假设条件下完成的),并给出有指导意义的结论.     

Investigation of the applicability of standardised growth curves for OSL dating of quartz from Haua Fteah cave,Libya

The establishment of standardised growth curve (SGC) for equivalent dose (D_e) determination can substantially reduce the amount of instrument time required for OSL measurements. In this study, we investigated the applicability of SGC for the optically stimulated luminescence (OSL) signal from single grains and small aliquots of sedimentary quartz from Haua Fteah cave, in Libya. The samples exhibit large inter-grain and inter-aliquot variation in the shape of their single grain and small aliquot dose response curves (DRCs) constructed from a range of sensitivity-corrected regenerative dose signals (L_x/T_x), which prevents the establishment of a single common SGC among different grains or small aliquots. Instead, the DRCs for the small aliquots can be divided into a minimum of three groups using the Finite Mixture Model, with the DRC saturating at a different dose level for each group. In order to establish a common DRC, or SGC, for each group, we propose a new normalisation method, the so-called least-squares normalisation procedure (‘LS-normalisation’), which largely reduces the variation between aliquots within the same group and allows the establishment of a common DRC, or SGC, for each group. In order to apply the SGC method for these samples, two regenerative dose points are needed for each aliquot to attribute it to one of the groups based on the ratio of the L_x/T_x signals for two sensitivity-corrected regenerative dose points. Equivalent dose (D_e) values for each aliquot can be estimated using the fitting parameters calculated for the SGC of the relevant group to which it belongs, together with measurements of the natural signal (L_n), one regenerative dose signal (L_x1) and their corresponding test dose signals (T_n, T_x1). For the samples investigated from Haua Fteah, we found that D_e estimates obtained from the SGCs are consistent with those obtained using a full SAR procedure. Our results suggest that small single-aliquot and single-grain D_e values obtained from application of the SGC may be underestimated if there is a significant proportion of early-saturating grains present in the sample; such grains or aliquots are mostly rejected due to saturation when analysed using the full SAR procedure. In this case, it is necessary to calculate the D_e values based only on those grains or aliquots that have relatively high saturation levels.     

弹性岩石层、区域重力异常和上地幔小尺度对流

在小尺度地幔对流模型的基础上 ,建立了顾及岩石层与地幔耦合的地幔对流模型。考虑到岩石层对上地幔小尺度对流的弹性响应 ,将上地幔视为一均匀的等粘滞系数的牛顿粘滞流体 ,其对流能量来源于下地幔 ,用热流体动力学基本方程得到的上地幔对流在壳幔边界处的垂向应力作为弹性板弯曲方程的垂直加载 ,来耦合弹性岩石层和可流动地幔。推导了两者耦合下区域重力异常和上地幔小尺度对流的相关方程 ,用以反演上地幔小尺度对流流场模式和岩石层底部拖曳力场格局。对比了有、无弹性岩石层影响的模型之间的差异 ,并对模型应用范围 ,特别是板块边界水平构造力可能产生的影响 ,作了进一步探讨。     

高空间分辨率卫星遥感地质微构造及蚀变信息识别应用研究

高空间分辨率卫星遥感数据的获取已有十几年的时间,积累了很多存档数据。研究发现,小尺度范围一些典型蚀变信息及小节理、断裂（群）、岩脉（墙）及小岩株多期次侵入相等在高分辨率遥感影像上具有独特反映,这些信息往往与矿床具有密切关系,以此信息进行遥感找矿分析,可为快速找矿提供一种重要方法。     

Quasiperiodic small meanders of the Kuroshio off Cape Ashizuri and their inter-annual modulation caused by quasiperiodic arrivals of mesoscale eddies

A quasiperiodic variation of 100–110 days in the Kuroshio path off Cape Ashizuri, resulting from the passage of small meanders, was detected by observation with moored current meters during 1993–1995. TOPEX/POSEIDON altimeter data covering 9 years showed that the quasiperiodic variation period was not persistent and modulated twice, with a ∼110-day period from mid-1993 to late 1996, a ∼150-day period from late 1996 to mid-1999, and a ∼110-day period from mid-1999 to late 2001. The quasiperiodic variations of the Kuroshio path migration were contemporaneous with the quasiperiodic arrivals of mesoscale eddies from the east along 27–32°N over the same ∼110- and ∼150-day period quasiperiodic variations. The periodic arrivals of the eddies configure the periodic variations of the Kuroshio path and its inter-annual modulation.     

多源降水数据的小流域水文模拟效用评估

小流域是研究小微尺度水文水资源系统演变规律的理想对象,是用于计算河流产水产沙 的最小单元,是水文及水土流失研究与管理的最佳地域尺度。通过遥感技术,气候模式获得降水 数据,并驱动分布式水文模型,模拟和预测水文过程,是流域水文水资源研究的必然趋势。以 NO? AA-CPC-US 降水作为参照,在美国不同地区的 9 个小流域,评估卫星降水产品 PERSIANN,PERSI? ANN-CDR,TRMM-3B42V7,GPM-IMERG,雷达降水 StageIV 以及气候模式 ERA5 降水产品的精度, 并用这 7 种降水产品驱动 CREST 分布式水文模型,评估了 7 种降水产品的水文模拟效用。研究表 明：各降水产品与 NOAA-CPC-US 降水吻合程度从高到低,依次是 StageIV 雷达降水,PERSIANN- CDR 和 GPM-IMERG 次之,再次是 PERSIANN 和 ERA5,最后是 TRMM-3B42V7。各降水产品在美 国北部高纬度地区和西部山地等区域的小流域降水估算精度略低,在美国中部,南部,东部的小流 域有较好的降水精度。在水文模拟效用评估中,设定相同率定期,分别使用 7 种降水产品率定 CREST 模型参数,得到率定参数集后,在相同验证期对流域日径流过程进行模拟。结果表明：NO? AA-CPC-US 和 Stage IV 雷达降水在各小流域水文模拟中效果较好,在美国北部和西部地区,使用 PERSIANN,PERSIANN- CDR,GPM- IMERG,ERA5 降 水 进 行 水 文 模 拟 时 需 要 谨 慎 。 TRMM- 3B42V7 的小流域水文模拟效果不理想。     

滇中晚新生代陆相小型湖盆层序地层学研究

运用层序地层学的理论和方法，进行小型陆相湖盆地层研究时，发现昆明盆地存在三个超层序（二级旋回）：盆地断陷沉积超层序，盆地扩张超层序及盆地萎缩超层序。各超层序内部还可以划分2－3个层序（三级旋回）。实践证明：层序地层理论不仅可以在小型陆相湖盆中得到很好 的运用，还可以根据层序内部的体系域组成的不同区分构造层和气候层序。而且，小型湖盆的层序地层研究取得的成果，可以广泛运用于天然气勘探，构造研究等领域。     

涡动相关系统和小孔径闪烁仪观测的森林显热通量的异同研究

涡动相关系统和闪烁通量仪都是评价局地到区域尺度的地表显热通量的有效途径.以ChinaFLUX千烟洲人工林生态系统2倍和3倍冠层高度的2套涡动相关(EC)系统和通量塔及其东偏南方向距离通量塔约70 m处1.2倍冠层高度安装的1套小孔径闪烁通量仪(SAS)为基础,重点对比分析了EC系统和SAS系统观测的显热通量的异同.研究表明,2倍和3倍冠层高度EC系统与SAS系统的显热通量的观测值有非常好的相关关系与一致性.在季节尺度和日尺度上,在降水正常的季节里SAS测定的显热通量值高于2倍和3倍冠层高度EC系统的测定值.但是在干旱胁迫条件下,SAS测定的显热通量低于2倍和3倍冠层高度EC系统的显热通量值.按16方位风向进行的相关分析表明,以南到南偏西和北偏东到东偏北2个与盛行风向垂直的方位相关性最高.在白天条件下,2倍和3倍冠层高度EC系统与SAS测定的显热通量值均显示出较高的相关性.但夜间无论是2倍还是3倍冠层高度EC系统与SAS测定的显热通量值之间相关性均很低.EC系统与SAS观测的显热通量的差异主要与通量覆盖区的差异以及各自的局限性有关.