基于组合赋权理想点法的高切坡安全评价

选取高切坡的黏聚力、内摩擦角、高切坡类型、地形坡度、边坡高度作为评价指标,结合理想点法的基本原理,建立高切坡安全评价模型。针对指标权重评价中存在主观影响因素过多、评价指标权值不确定等问题,运用组合赋权法来确定其权重系数,并对实际工程的高切坡进行安全评价。结果表明,所选高切坡的评价结果与实际评价结果基本一致,证明该方法用于高切坡的安全评价合理、有效。     

围岩稳定性评价的改进物元可拓模型与应用

为弥补现有地下工程围岩稳定性评价方法的不足,建立了改进的物元可拓模型。通过构造一种新的关联函数,解决了因传统的物元可拓模型的关联函数是一个分段函数而存在的不便于计算的缺陷,以及评价指标间的互不相容性问题,拓宽了物元可拓法的应用范围。将改进的物元可拓模型应用于某地下工程围岩的稳定性评价,结果表明,样本1、2、5属于Ⅱ级(较稳定),样本3、4属于Ⅰ级(稳定)。通过将其评价结果与传统可拓法及模糊数学综合评判结果进行比较分析,证明该评价方法的正确性。研究表明,改进的物元可拓模型的评价结果与实际工程地质情况更为吻合,准确度更高,能够反映各因素对围岩稳定性的影响,其合理性和可行性得到了验证。     

含多弱层复合边坡滑坡治理三维数值分析

白音华二号矿滑坡区边坡治理工程是针对稳定性差的南帮非工作帮和南排土场构成的复合边坡进行的。滑坡体受多层弱层控制,治理过程中易导致边坡失稳,所以治理工程采取分区开采的条采方案,充分利用边坡治理的三维效应来进行边坡的失稳破坏研究和稳定性分析。选取滑坡区的典型剖面作为研究对象,基于强度折减方法(SRM),应用有限差分FLAC3D软件,在两种开挖条件下,对含多弱层的复合边坡的稳定性规律和破坏机制进行了数值模拟分析,揭示了多弱层对复合边坡的失稳破坏及稳定性的影响。研究结果表明,治理工程中,弱层被揭露一定宽度,滑体沿煤底板弱层水平错动、竖直方向拉裂破坏;随弱层暴露宽度的增加,边坡稳定性明显降低,说明治理边坡具有三维效应;开挖至3-3煤层底板,开挖坡角20°,弱层暴露宽度为400m,边坡的稳定系数刚好达到安全储备系数1.1,建议矿方首选此方案,可以最大限度的回收煤炭资源。     

Effect of urea on detonation characteristics and thermal stability of ammonium nitrate

A study has examined the effect of urea on the thermal stability and detonation characteristics of ammonium nitrate (AN). The thermal decomposition temperature and surface morphology of samples were investigated by differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). For further research on the thermal sensitivity and shock sensitivity of the samples, the Koenen test and UN gap test were conducted. The results indicate that urea can substantially increase the thermal stability of AN (the greatest exothermic peak is increased by more than 100 °C) and reduce the thermal sensitivity of AN. However, AN-50wt. % urea mixtures can still produce a steady detonation in the UN gap test. Urea cannot reduce the ability to propagate a detonation. Possible explanations for these results are discussed.     

Application of a hydroxylamine nitrate stability model to plutonium purification process equipment

A mathematical model that predicts hydroxylamine nitrate (HAN) (NH₂OH·HNO₃) stability is applied to aqueous solutions containing HAN, nitric acid and plutonium that are used in plutonium purification processes. The model estimates the stability of these solutions with respect to the rapid, hazardous, autocatalytic reaction of HAN with nitric acid that generates heat and gas. It also accounts for reaction kinetics, temperature changes, gas generation rates, solution volumes and flow rates, and distribution of plutonium and nitric acid between aqueous and organic phases. The model is applied to three typical process vessels used in solvent extraction purification of plutonium – a countercurrent aqueous/organic plutonium stripping column, an oxidation column used for HAN and hydrazine destruction, and a plutonium rework tank. Both normal and off-normal process scenarios are modeled. Two of the off-normal scenarios lead to the rapid autocatalytic reaction of HAN with nitric acid where heat and gas are generated and that could lead to damage of the process equipment and/or release of hazardous plutonium solution from the vessel. In these two cases, stationary aqueous solutions containing HAN, Pu(III), and nitric acid were allowed to slowly react until conditions for the autocatalytic reaction were reached.     

土壤颗粒对纳米TiO_2悬浮稳定性作用机制的实验研究

在不含表面活性剂和含有表面活性剂两种条件下,研究了土壤颗粒对纳米TiO2(nTiO2)悬浮稳定性的影响.结果表明,土壤颗粒降低了nTiO2在水相中的悬浮稳定性.当体系中不含表面活性剂时,nTiO2在土壤大颗粒上的沉积是导致nTiO2脱稳沉淀的主要原因.在含有表面活性剂的溶液中,土壤颗粒降低nTiO2悬浮稳定性的作用变得更加明显了.一方面,表面活性剂加速了土壤颗粒本身的沉降从而增强了nTiO2在其中的沉降,另一方面,表面活性剂在土壤上的强烈吸附促进了表面活性剂-nTiO2在土壤上的沉积.扫描电镜显示,nTiO2不仅吸附在土壤大颗粒上,还会吸附在土壤小颗粒表面.3种表面活性剂中,十六烷基三甲基溴化铵(CTAB)悬浮的nTiO2与土壤颗粒共沉淀现象最明显.除了土壤对CTAB的吸附作用之外,XDLVO/DLVO能量计算显示CTAB体系中土壤颗粒与nTiO2之间存在显著第二极小值,表明nTiO2能够在第二极小值位置与土壤颗粒结合,从而与土壤颗粒一起快速沉淀.     

城市空气污染影响因素的灰色斜率关联度分析研究

城市空气污染严重影响着城市的发展和人民的健康,为了研究城市空气污染的影响因素对于污染的影响程度和类型,采用了灰色系统理论中灰色关联分析方法的斜率关联度模型.以广州、西安和乌鲁木齐为研究对象,选取了几个具有典型的空气污染因素.结果表明:对于这三个城市而言,燃煤都是空气污染的最主要污染因素,而对于不同的城市,其他污染因素对于不同污染物有着不同的影响,在污染治理的时候要分析城市具体所存在的首要污染物以对症下药.     

基于分形维数的斜坡非饱和带土体大孔隙分布研究

对取自于云南省昭通市头寨滑坡滑源区附近的两个大尺度(25cm×25cm×50cm)土柱样品进行CT扫描,选取典型剖面切片,通过CT值范围将大孔隙分离从而研究土体中的大孔隙分布;计算大孔隙分布分维数(盒维数),研究其大孔隙的不规则特征,结果表明:土体中大孔隙的盒维数随深度增加呈单调递减规律,且与大孔隙度具有显著正相关关系;但大孔隙度只能表征在某一深度上大孔隙的分布多少,而大孔隙的不规则特征则需盒维数表征;最后得到大孔隙的累积大孔隙度与大孔隙孔径(在盒维数为常数时)符合幂函数规律,研究结果有利于利用分形理论建立大孔隙模型,从而研究水分在大孔隙中运动过程。     

混凝-超滤处理径流雨水效果——以华南地区为例

采用超滤膜(UF)为核心,以混凝作为预处理措施,对混凝-超滤工艺处理径流雨水的特性和膜通量变化与污染现象进行了研究,并对聚合硫酸铁(PFS)单独混凝、UF、PFS-UF组合工艺进行了对比;在优化混凝基础上,考察了混凝-UF对常规水质指标及总磷、生物可同化有机碳(AOC)、可生物降解溶解性有机碳(BDOC)等生物稳定性指标的去除效果.结果表明,混凝可有效去除TOC、UV254和总磷,混凝剂投加量与污染物去除近似呈线性关系.各混凝剂除浊效能均良好.综合考虑混凝处理效率与经济性,实验采用混凝方案为10 mg·L-1的PFS.PFS、UF、PFS-UF工艺除浊率均在95%以上,PFS和UF对TOC和UV254的去除较为接近,采用PFS-UF可提高去除率13%—15%;PFS-UF处理后雨水的AOC、BDOC分别降低至61.8μg·L-1、0.19 mg·L-1,残余总磷可降至3.8μg·L-1,雨水生物稳定性明显提高.PFS、UF和PFS-UF对颗粒物的去除率分别达80.5%、99.6%和99.9%.膜通量的变化和SEM图分析表明,混凝在一定程度上减轻了UF膜污染;形成的凝胶层具有一定整体强度,水力清洗时易于清除,膜通量恢复较好;但同时凝胶层的产生也增大了透膜阻力,PFS-UF工艺的周期内膜通量衰减有增加的趋势.     

Assessing slope stability in unplanned settlements in developing countries

Unplanned housing in developing countries is often located on steep slopes. Frequently no building code is enforced for such housing and mains water is provided with no drainage provision. Both of these factors can be particularly significant in terms of landslide risk if, as is so often the case, such slopes lack any planned drainage provision. There is thus a need to develop a model that facilitates the assessment of slope stability in an holistic context, incorporating a wide range of factors (including surface cover, soil water topographic convergence, slope loading and point source water leakage) in order that appropriate advice can be given as to the general controls on slope stability in such circumstances. This paper outlines a model configured for this specific purpose and describes an application to a site in St. Lucia, West Indies, where there is active slope movement in an unplanned housing development on relatively steep topography. The model findings are in accord with the nature of the current failure at the site, provide guidance as to the significance of slope drainage and correspond to inferences drawn from an application of resistance envelope methods to the site. In being able to scenario test a uniquely wide range of combinations of factors, the model structure is shown to be highly valuable in assessing dominant slope stability process controls in such complex environments.