A two-grid search scheme for large-scale 3-D finite element analyses of slope stability

It is well known that the trial process for seeking the safety factor in the shear strength reduction finite element method (SSRFEM) is quite expensive, particularly for large 3-D slope stability analyses. The search algorithm for the safety factor is crucial to the entire solution process for the shear strength reduction finite element method, but few studies have attempted to exploit it. Among search algorithms, the commonly used bracketing and bisection search has not been fully optimised. Consequently, to improve the search scheme for the safety factor associated with the shear strength reduction finite element method, two strategies are suggested. First, a generalised bisection search algorithm is proposed to reduce the possibility of encountering non-convergence from a statistical point of view. To further improve the efficiency, a new two-grid scheme, characterised by a coarse mesh search and followed by a fine mesh search, is developed. Based on the drained or undrained analyses of the 3-D slope examples, the new search algorithm can markedly outperform the commonly used bisection search algorithms based on a single finite element mesh.     

Material screening and selection for XENON100

Results of the extensive radioactivity screening campaign to identify materials for the construction of XENON100 are reported. This dark matter search experiment is operated underground at Laboratori Nazionali del Gran Sasso (LNGS), Italy. Several ultra sensitive High Purity Germanium detectors (HPGe) have been used for gamma ray spectrometry. Mass spectrometry has been applied for a few low mass plastic samples. Detailed tables with the radioactive contaminations of all screened samples are presented, together with the implications for XENON100.     

彝良-镇雄铅锌矿矿集区资源潜力分析

矿集区构造、地层、遥感数据等控矿因素结合统计和分析,建立地质综合信息数学信息模型,并据此确定信息量边界值,在矿集区内圈定3个找矿有利靶区,一个A级两个B级。     

基于统计理论方法的水文模型参数敏感性分析

参数敏感性分析是模型不确定性量化的重要环节,有助于有效识别关键参数,减少参数的不确定性影响,进而提高参数优化效率。利用Morris筛选方法定性识别相对重要参数,耦合方差分解的Sobol方法和统计理论的响应曲面模型构建一种新的定量敏感性分析方法——RSMSobol方法。以长江支流沿渡河流域的日降雨径流过程模拟为例,系统分析4种不同目标函数响应条件下新安江模型的参数敏感性。结果表明Morris方法和RSMSobol方法的集成应用极大地提高了全局敏感性分析的效率,Morris定性筛选结果为定量评估减少了模型参数维数,采用代理模型技术的RSMSobol方法减少了模型的计算消耗。     

贵州威宁长坪子铅锌矿区地质特征及控矿因素浅析

贵州威宁长坪子铅锌矿区位于北西向的江子山背斜铅锌成矿带中段,矿床的形成和分布受江子山背斜构造的控制。而矿体受主干构造及其压性纵断层的下盘或层间破碎带控制,或北西与北东向断裂共同控制;矿体主要呈似层状、透镜状;矿体的产出主要受地层、构造条件共同控制。系统地研究了区内的导矿、配矿、容矿构造特征,提出了地质构造是控制矿床形成和分布的主导因素,以便为区内地质找矿理清思路,指明方向。     

皱纹盘鲍(Haliotis discus hannai)肠道潜在益生菌的筛选及对幼鲍生长的影响

采用体外实验筛选益生菌结合16SrDNA序列分析法,从124株不具有溶血作用的皱纹盘鲍(Haliotis discus hannai)肠道细菌中筛选得到5株潜在益生菌并进行了分子鉴定,进一步对5株潜在益生菌进行了安全性实验及体内饲喂实验。结果表明,2株具有拮抗哈维弧菌和灿烂弧菌能力的潜在益生菌分别被鉴定为Shewanella sp.(WA64)和Shewanella sp.(WA65),一株产海藻酸酶和淀粉酶的潜在益生菌被鉴定为Vibrio sp.(WA51),产蛋白酶潜在益生菌被鉴定为Bacillus sp.(FA12),产琼脂酶潜在益生菌被鉴定为Tamlana sp.(FA86);安全性实验表明5株潜在益生菌在107cfu/ml下对皱纹盘鲍没有明显的毒害作用;通过体内饲喂实验发现,潜在益生菌WA64、WA65的复合作用能够显著提高幼鲍增重率和存活率(P<0.05),并在生产条件下能够明显降低幼鲍的死亡量。经抗生素敏感性实验,WA64菌株对15种抗生素均敏感或中度敏感,WA65菌株仅对庆大霉素和链霉素2种抗生素产生耐药。     

重庆市县域综合发展水平差异的时空特征分析

选择重庆市40个县域2001年和2006年的相关统计数据,采用因子分析法建立县域综合发展水平测度模型．运用统计学软件SPSS15．0．对重庆市县域综合发展水平差异进行评价和类型区划．并利用ARCGIS9．2软件分别绘制出2001和2006年40个县域的综合发展水平空间分异图。结果表明．县域综合发展水平的差距依然比较显著．在因子上由2001年的社会发展规模因素转化为2006年的工业化发展因素．空间上呈现出距离区域增长极空间位置的远近和交通可达的难易而逐层递减的圈层分异特点。     

Capture and release zones of permeable reactive barriers under the influence of advective–dispersive transport in the aquifer

The problem of permeable reactive barrier (PRB) capture and release behavior is investigated by means of an approximate analytical approach exploring the invariance of steady-state solutions of the advection–dispersion equation to conformal mapping. PRB configurations considered are doubly-symmetric funnel-and-gate as well as less frequent drain-and-gate systems. The effect of aquifer heterogeneity on contaminant plume spreading is hereby incorporated through an effective transverse macro-dispersion coefficient, which has to be known. Results are normalized and graphically represented in terms of a relative capture efficiency M of contaminant mass or groundwater passing a control plane (transect) at a sufficient distance up-stream of a PRB as to comply with underlying assumptions. Factors of safety FS are given as the ratios of required capture width under advective–dispersive and purely advective transport for achieving equal capture efficiency M. It is found that M also applies to the release behavior down-stream of a PRB, i.e., it describes the spreading and dilution of PRB treated groundwater possibly containing incompletely remediated contamination and/or remediation reaction products. Hypothetical examples are given to demonstrate results.     

Pseudo-Static Analysis of Soil Nailed Excavations

In this paper, a pseudo-static analysis has been presented to investigate the stability of soil nailed vertical/nearly vertical excavations. The failure surface is assumed as the arc of log-spiral passing through the toe of the excavation and intersecting the ground at right angle. The horizontal and vertical seismic forces are taken in terms of horizontal and vertical seismic coefficients. The internal failure mode of the nailed cut is considered either by pull-out or rupture or excessive bending whichever is critical. Expression for the factor of safety is derived using moment equilibrium method. Results have been arranged in tabular form considering ranges of the design parameters usually occur in practice. A typical table for the design of nailed excavation with driven nails is presented in the paper. Analytical results have been compared with the findings of model tests and reasonably good agreement has been observed.     

Techniques for slope stability analysis: Site specific studies from Idukki district,Kerala

The occurrences of slope failures are frequent in Idukki district of Kerala state particularly along the road cuttings and hill slopes causing disruption in traffic, loss of lives and property. This demands a critical evaluation of stability of slopes along the hill roads. This paper deals with stability analysis of a typical hard rock profile at Chuzhappu and a lateritic profile at Kumili along the road connecting Kottayam and Kumili. A large number of factors have been examined and studied; the orientation of discontinuities has been identified as one of the major inherent factors influencing slope instability along Chuzhappu hard rock profile. These have been analysed carefully using stereographic/equal area projection technique in order to determine the vulnerability to slope failure and to understand the type of rock slide that can occur in this profile. The buoyant force of water acting along the discontinuities after heavy rain storm further aids the down slope movement. As the laterite slope is mostly homogeneous, Bishops method and Swedish method were adopted for stability analysis of laterite slope at Kumili. The study also examines the efficacy and applicability of the different methods employed in soil mechanics to assess the stability of laterite slope.The results obtained by this method are compared by actual field conditions. The stability assessment indicates that two sectors at Chuzhappu and one sector at Kumili profile are at the geo-technical threshold of failure, when piezometric head rises during rainstorm. The study indicates that these methods are highly useful in determining the Factor of Safety in profiles with similar geological setting.