Numerical simulation of groundwater flowing to horizontal seepage wells under a river

A horizontal seepage well, consisting of an interconnected vertical well, galleries, chambers and small-diameter radiating bores, is used to acquire relatively clean water that has been filtered through natural alluvial deposits in a riverbed. It has wide application, especially in arid and semi-arid areas. The lack of calculation formulae or models for horizontal seepage wells, up until now, has resulted in several false applications. Based on the analysis of groundwater flow characteristics, it has been concluded that several flow regimes coexist and hydraulic head loss exists in the horizontal seepage well. To avoid the difficulty of confirming the flux or head distribution in such a complex system, the model boundary of the whole horizontal seepage well has been moved to that of just the vertical well, and the well-aquifer system was treated as a heterogeneous medium, where the horizontal seepage well itself is a highly permeability medium. A mathematical model has been developed, based on the coupled seepage-pipe flow, by the introduction of equivalent hydraulic conductivity according to different flow regimes. Then a three-dimensional finite difference numerical model, based on the mathematical model, was developed and applied to a horizontal seepage well in China. The numerical model verified the groundwater flow characteristics of the horizontal seepage well. An erratum to this article can be found at     

不同量剂凹凸棒石粘土对镉污染菜地的修复实验

凹凸棒石具有较大的比表面积和超强的吸附性能,向土壤中施加一定量的凹凸棒石粘土,会使土壤中有毒重金属元素失去活性,并能有效地阻止其向农作物转移,确保农产品安全。本次试验,利用凹凸棒石粘土特有的物化性能,对八卦洲Cd含量超标的土壤进行了修复试验研究。结果表明,在Cd超标的土壤中施加适量的凹凸棒石粘土矿物,能使芦蒿中的Cd含量降低46%,并且土质及农产品的产量均没有受到不良影响。     

A new criterion for strength of frozen sand under quick triaxial compression considering effect of confining pressure

The strength of frozen soils has been one of the most extensively studied aspects in frozen soil mechanics. When carrying out deep excavations using freezing methods, high stress states are often encountered. Therefore, the strength of frozen soils under high confining pressures is of major concern. This paper first reviews the present failure criteria for frozen soils, especially with regard to the effect of confining pressure on the strength. It is suggested that the strength consists of two components, cohesion and friction, and can be expressed by the Mohr–Coulomb criterion and in the framework of the Drucker–Prager criterion. However, these two components are both dependent on the stress state. Duncan’s equation for the friction angle is extended to frozen soils. A frozen Lanzhou fine sand is taken as study subject. The frozen sand is compressed at a high strain rate under three different temperatures and under a wide range of confining pressure. Experimental results have confirmed the generally recognized principle that the strength increases with the confining pressure up to certain value. Thereafter, it decreases with continued increase in confining pressure. Experimental data from our own tests and literature are fitted to the new criterion, which shows its validity.     

高分辨率浅层人工地震勘探探测隐伏断裂实例

利用高分辨率浅层地震勘探反射波法探测了福建某火电厂场址内的隐伏断裂。结果表明断裂显示清楚,为一走向NE40~55°,上断点埋深为11 m和31 m,断距2~4 m的正断层,为工程避让提供较可靠的依据。     

特大地震对震源邻区的增(减)震作用的研究

通过研究中国大陆1910年以来8级以上特大地震和国外几组典型特大地震对震源邻近区域的影响,发现特大地震往往发生在断裂带上,一组或一次特大地震可能使发震断裂部分破裂,而未破裂断裂的构造应力可能增大,又成为大震的空段,该空段短时间内可能会发生大震(起到增震作用);反之,发震断裂完全破裂或没有大震空段,震源邻近区域构造应力可能减小,短时间可能不会发生大震(起到减震作用)。依据这一结果,可对特大地震发生后震源邻近区域的后续大震作短、中期预测。     

Deriving Acceleration from DGPS: Toward Higher Resolution Applications of Airborne Gravimetry

Although airborne gravimetry is now considered a fully operational technique, errors due to motion compensation using differential GPS (DGPS) continue to influence both its accuracy and the range of applications in which it can be used. In typical medium-resolution applications such as airborne geoid mapping, errors due to DGPS contribute considerably to the error budget of an airborne gravity system. At the same time, efforts to increase the resolution of such systems for demanding applications such as resource exploration remain impedded by errors in DGPS. This article has three objectives. The first one is to compare eight industrially relevant DGPS software packages for the determination of aircraft acceleration. The second objective is to analyze and quantify the effect that each relevant portion of the DGPS error budget has on the determination of acceleration. Using data sets that represent a wide range of operational conditions, this is done in the frequency domain over a range of frequencies corresponding to spatial resolution as high as 450 m. The third objective is to use that information to recommend and demonstrate approaches that optimize the estimation of aircraft acceleration for determining the geoid and for resource exploration. It is shown, for example, that the time of day in which the survey is carried out and the dynamic characteristics of the aircraft being used are two of the most crucial parameters for very high-resolution gravity field estimation. It is demonstrated that when following the above-mentioned recommendations, agreements with ground daa of better than 1.5 and 2.5 mGal can be achieved for spatial resolutions (half-wavelengths) of 2.0 and 1.4 km, respectively. ? 2002 Wiley Periodicals, Inc.     

地统计学分析技术及其在气象中的适用性

首先论述了地统计学的一些特点，然后从变异函数和Kriging插值两个方面介绍了地统计学的分析技术，最后讨论了地统计学在气象研究中的适用性。     

正交实验法在测绘中的应用

以检测数字水准仪及标尺综合精度为例，介绍了正交实验法在测绘领域中的应用。     

地球质心运动的频谱分析方法

针对地球质心运动主要是由多种周期运动叠加的特点，依次讨论了谱分析方法中的AR模型谱分析和小波谱分析方法，分别指出：将参数谱分析方法中的AR模型谱分析和非参数谱分析中的小波谱分析相结合产生的小波－AR谱分析以及小波包－AR谱分析方法，在地球质心运动的谱分析中有较好的频率分辨率以及噪声抑制能力。     

正交实验法在测绘仪器检定中的应用

在测绘生产和科研项目中，为了改革旧工艺或对新仪器，新产品,经常需要做多因素实验，如何安排多因素实验，是一个很值得研究的问题，文中以数字水准仪及标尺综合精度的检定为例，介绍了正交实验法在测绘仪器检定中的应用。