Modelling of landslides with the material-point method

A numerical model for studying the dynamic evolution of landslides is presented. The numerical model is based on the Generalized Interpolation Material Point Method. A simplified slope with a house placed on top is analysed. An elasto-plastic material model based on the Mohr–Coulomb yield criterion is employed for the soil. The slide is triggered for the initially stable slope by removing the cohesion of the soil and the slide is followed from the triggering until a state of static equilibrium is again reached. Parameter studies, in which the angle of internal friction of the soil and the degree of discretisation are varied, are presented.     

Spinning with the dinosaurs: the fossil record of spiders

When most people hear the word 'fossil' they tend to conjure up images of giant dinosaurs such as Tyrannosaurus rex or shelled marine invertebrates. Prior to the Hollywood blockbuster movie Jurassic Park , which was based on recreating dinosaurs through extracting their DNA from fossil mosquitoes preserved in amber, few non-palaeontologists would entertain the notion that small, soft-bodied organisms such as insects occur in the fossil record. However, insects and spiders are common as fossils in amber, where they are often preserved with life-like fidelity, and they also occur to a lesser degree in carbonate rocks.     

Meteorological factors associated with floods in the north-eastern part of the Iberian Peninsula

The main meteorological features of catastrophic rainfall events in Catalonia are described. Data come from several sources listed in the text. Surface and upper air synoptic and some subsynoptic conditions under which these events occur are described. Two kinds of events are identified, depending on the amount of forced lift required to release potential instability: Type A events, which take place on the coastal area when the forcing due to littoral and prelittoral hills is enough, and type B events require a large forced lift and occur near the Pyrenees. Local topographical and mesoscale meteorological conditions turn out to have a relevant role in connection with such events.     

Investigation of bauxites with the help of electron-probe

Summary 25 representative karstic and lateritic bauxite samples from Europe, Asia and Africa were studied by a JEOL-JXA-5 electron-probe X-ray microanalyser. The main directions of the investigation were: determination of the microtextures and the distribution of the main elements in bauxite (Al, Fe, Ti, Si). Conclusions on the genesis of the textural constitution and on bauxitization are given. Further possibilities of using the electron-probe in solving different problems connected with bauxites are enumerated.

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Bauxit-Untersuchungen mit der Elektronstrahl-Mikrosonde

Zusammenfassung Es wurden 25 typische Karst- und Lateritbauxite aus Europa, Asien und Afrika mit Hilfe einer JEOL-JXA-5 Elektronstrahl-Mikrosonde untersucht. Die Hauptrichtungen der Untersuchung waren die Bestimmung der Mikrostruktur und die Verteilung der Hauptelemente in den Bauxiten (Al, Fe, Ti, Si). Es wurden mehrere Schlüsse bezüglich der Entwicklung der Strukturelemente und der Bauxitbildung gezogen. Weitere Anwendungs-möglichkeiten zur Lösung verschiedener Bauxit-Probleme werden angegeben.

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With 30 Figures     

含不同半径孔洞的颗粒体模型的力学行为数值模拟

本文通过编程建立了非连续介质(颗粒体材料)模型,采用FLAC软件模拟了静水压力条件下不同半径的巷道围岩中的剪切应变增量、最小主应力及最大主应力的分布规律。研究表明,随着孔洞半径的增大,呈圆环形的剪切应变增量与最小主应力的高值区的圈数、呈辐射状的最大主应力的高值区的延伸范围及剪切应变增量的最大值都呈先慢后快的增长趋势。模型中最大的拉应力接近于在模型四周所施加的压应力,而最大的压应力约为所施加的压应力的5～10倍。模型内部的剪切应变增量、最小主应力及最大主应力的分布是高度不均匀的。具有较高的差应力的位置与具有较高的剪切应变增量的位置具有很好的一致性。     

加筋土挡土墙边坡的稳定性分析

加筋挡土墙边坡是一种新型的复合边坡加固技术,用传统的方法很难设计这种复杂的结构。以一工程实例叙述了采用弹塑性有限元法预测加筋土边坡的稳定性的方法;给出了不同设计方案下的位移;分析了土体力学参数对边坡最大水平位移的影响。结果表明,土体的弹性模量、内摩擦角与粘聚力是影响边坡位移的重要因素。这些土力学参数与边坡最大水平位移是非线性关系,且有呈现临界点的趋势。因此,适当控制填土的力学性能参数有助于达到安全节省的设计目标。      

Selected aspects of the stability assessment of slopes with the assumption of cylindrical slip surfaces

A comprehensive analysis of maintaining stability by model homogeneous and stratified slopes, with possible surcharge loading, is carried out within the article. Calculations are performed by the Swedish method of Fellenius under the assumption of a cylindrical slip surface passing through the slope foot. Proposals for searching for the reach of the break-off wedge of a potential slip surface are put forward. An analysis of the effect of surcharge load location on general slope stability is also made, providing the capability to determine the safe distance of positioning of an excavator on the surcharge of a non-encased excavation.     

Structure of the circumbinary envelopes of young binary stars with elliptical orbits

The results of two-dimensional gas-dynamical numerical simulations of the structure of matter flows in the envelopes of a number of T Tauri binary systems with elliptical orbits are considered. The main flow elements in inner regions of protoplanetary disks of these stars are described. The influence of shocks on the size of the gap—a rarified region in the inner parts of the protoplanetary disk—is analyzed. A method is proposed for estimating the size of this gap from the numerical simulations, and the gap sizes for the studied stars are determined and compared with observational results. The flow dynamics in the gap is considered, and the periodic variations of the gap size on time scales of several orbital periods are analyzed. Possible observational manifestations of the studied flows are discussed.     

Coping with water scarcity: the case of the Calnistea catchment (Romania)

The Calnistea catchment lies in the southern part of Romania in a region that has been confronted lately with serious water scarcity problems generated primarily by summer heat waves and long periods of drought. The high temperatures, excessive evapotranspiration and scant precipitation have a negative impact on water resources and especially on the river system, which is at the mercy of meteorological conditions, because all the streams in the area originate in the plain. Consequently, mean annual discharges are very low and more often than not, many rivers run dry. In order to avoid such an unwanted phenomenon people have built earth dams across the valleys thus creating chains of ponds, which are used to regulate the flow. Even so, however, most of the years the rivers look like mere threads of water oozing gently through their sediments. Under the circumstances, it is no wonder that irrigation systems are missing, which explains the low agricultural productivity. The most important asset of the region is the groundwater, as it represents the only source of drinking water for the population. Groundwaters are stored in superposed aquifers, most of them confined, generally having good hydrogeological properties. Water quality complies with the standards for drinking water and that is why groundwaters are used as such for domestic consumption. The problem is that in the past years, population increase has put more pressure on this resource and consequently water table sank. The growing depletion of groundwaters has brought about thirst, famine, poverty and despair, sad realities that local authorities are striving to control. Given this necessity the present study aims at making several proposals of what could be done on a short and middle term in order to increase the water supplies of the region and thus alleviate the people??s suffering.     

Researching the geography of health and health care: Connecting with the Third World

In the context of doing research on the geography of health and health care, ‘connecting’ takes on multiple meanings. First, there are the connections between research topics although the political and socio-economic realities of the various geographical contexts can lead to foci on different aspects and social and geographic processes. There are then the connections between researchers from developed and developing countries who share an interest in the geography of health and health care, who perhaps transfer or refine research methods to look at the different contexts and even different topics. Finally, in this context, there are the connections between researchers and the IGU Commission on Health, Environment and Development (HED) promoted by the HED for the past eight years through its activities. This paper uses examples from the literature and the activities of HED to illustrate these various connections. It argues that if the geography of health and health care is to continue to develop, these three sets of connections must continue to grow and strengthen. This revised version was published online in July 2006 with corrections to the Cover Date.     

Soft numbers: problems with the quality of official data

There is a worsening crisis in official statistics in most if not all countries. Agency resources have been strained for many years, while they are faced with demands for more information faster. Politicians have become ever more concerned with getting ‘good’ numbers. These forces impinge negatively on the quality of data even where computerization has increased and become more sophisticated. Further, individuals and firms are increasingly reluctant to supply sensitive data or even any data. This paper examines the data quality situation at international, national, and local scales from the viewpoint of data users. A distressing finding is that they are ordinarily unable to obtain quality information disaggregated geographically or socially. Examples from the US, the Netherlands, Portugal, and Finland are presented. Less detailed information on quality problems and responses by international organizations and other national agencies is summarized. Techniques for remedial action and suggestions for actions by users follow. This revised version was published online in July 2006 with corrections to the Cover Date.     

遗传算法在边坡地震稳定性分析中的应用

基于遗传算法和拟静力简化毕肖普法提出搜索地震作用下最危险滑动面及相应的最小安全系数的方法。阐述了应用遗传算法搜索最危险滑动面的计算过程和原理。开发了基于遗传算法的拟静力简化毕肖普数值法的计算和数据处理程序。在固定一个出逸点的情况下,分别绘制了有地震作用及没有地震作用下的安全系数分布图。数值算例表明,所建立的基于遗传算法的岩土边坡地震稳定性分析方法,是一种全局优化搜索算法,能够有效克服经典搜索方法易陷入局部极小值的缺点。从安全系数分布图可以看出,地震对安全系数分布情况影响很小,但扩大了安全系数低值区。     

日本结晶片岩滑坡的活动特点及与降雨的关系

日本四国地区分布有大量具有独特地质条件和活动特征的结晶片岩滑坡。长期的实地观测结果表明,季节性的集中降雨是影响此类滑坡活动的主要因素。文章基于对此类滑坡活动观测资料和降雨资料的综合分析,阐述了结晶片岩滑坡的活动特点以及集中降雨对其的影响作用。通过对有效雨量和滑坡位移等反映降雨影响和滑坡活动状况参数的分析,揭示了集中降雨与滑坡活动之间的关系,并且确定了对该地区滑坡活动产生影响的降雨特征,为此类滑坡灾害的防治与管理提供了依据和评价指标。     

水压致裂法测量裂隙岩体的地应力研究

通过对水压致裂法形成的钻孔印模分析,运用Taylor公式和最小二乘法迭代算法,计算纵向和横向裂隙岩体地应力大小及其误差。首先确定大地、裂隙和钻孔坐标系,根据印模曲线确定裂隙方位;然后用Taylor公式和最小二乘法迭代算法,计算应力分量;最后计算出主应力大小及其误差。将此方法应用于雪峰山隧址区ZK6钻孔的地应力场计算,得出其最大水平应力为13 MPa,方位113°左右,这与地质构造法实测的应力场相吻合,说明这一方法合理可行,具有较好的实用价值。      

花岗岩矿物组成与其单轴抗压强度的相关性研究

花岗岩体是很多重要工程地基或围岩的首选。选取高放废物地质处置阿拉善预选区巴彦诺日公花岗岩样品,开展薄片鉴定,获得各花岗岩样品的矿物含量和粒径;通过单轴压缩试验,获得花岗岩的单轴抗压强度。通过对比各组样品矿物含量和粒径与单轴抗压强度,研究二者之间的关系。结果表明:对花岗岩单轴抗压强度影响最大的矿物是钾长石和黑云母,斜长石和石英的影响不明显;矿物粒径与单轴抗压强度的相关性不明显,但与某一结构岩石单轴抗压强度的相关性明显;花岗岩的强度不仅仅取决于组成矿物含量和粒径,对于其内部结构的细节（如微裂隙、矿物排列、胶结等）非常敏感。     

高填土地基强夯夯击能的使用研究

结合广东某电厂高填土地基强夯的实践，对夯击能的使用问题提出几点看法，并根据现场孔隙水压力和变形监测及夯后检测等资料。说明如何正确选用夯击能以达到更好的加固效果。     

Optimization with the Gradual Deformation Method

Building reservoir models consistent with production data and prior geological knowledge is usually carried out through the minimization of an objective function. Such optimization problems are nonlinear and may be difficult to solve because they tend to be ill-posed and to involve many parameters. The gradual deformation technique was introduced recently to simplify these problems. Its main feature is the preservation of the spatial structure: perturbed realizations exhibit the same spatial variability as the starting ones. It is shown that optimizations based on gradual deformation converge exponentially to the global minimum, at least for linear problems. In addition, it appears that combining the gradual deformation parameterization with optimizations may remove step by step the structure preservation capability of the gradual deformation method. This bias is negligible when deformation is restricted to a few realization chains, but grows increasingly when the chain number tends to infinity. As in practice, optimization of reservoir models is limited to a small number of iterations with respect to the number of gridblocks, the spatial variability is preserved. Last, the optimization processes are implemented on the basis of the Levenberg–Marquardt method. Although the objective functions, written in terms of Gaussian white noises, are reduced to the data mismatch term, the conditional realization space can be properly sampled.     

宁镇山脉小壳化石层时代的新认识

最新研究表明，句容仑山的小壳化石层和南京幕府山的一样，其层位都相当于下寒武统沧浪铺阶Ｐａｏｋａｎｎｉａ带，为我国下寒武统层位最高的一个小壳化石组合带。句容仑山当时位于台地边缘，缺失了早寒武世早期至沧浪铺期中期的沉积。     

远破波作用数值模拟的CLEAR-VOF模型

在非结构化网格基础上,采用三阶精度的三步有限元方法离散N-S方程,CLEAR-VOF方法追踪运动水体自由表面,建立了数值波浪水槽模型.模拟了远破波冲击位于倾斜底坡上直立堤的过程.对直立堤上波压力和堤前流场的数值结果与模型实验结果做了比较.结果表明,远破波波浪力和流场的数值结果同PIV实验结果吻合较好,该数值波浪水槽模型可较好地模拟远破波的破碎冲击过程.     

高压喷射灌浆构筑垂直防渗板墙围井试验的几个问题

在简要介绍高压喷射灌浆技术原理的基础上，重点介绍了采用高压摆喷灌浆构筑垂直防渗板墙的围井试验情况，详细分析了围井开挖、注水试验及高喷墙体样品的检验结果，并提出了高压喷射灌浆技术在酸性水、动水、超深孔、含有大块石地层等条件下的应用问题。