Soil slip/debris flow localized by site attributes and wind-driven rain in the San Francisco Bay region storm of January 1982

GIS analysis at 30-m resolution reveals that effectiveness of slope-destabilizing processes in the San Francisco Bay area varies with compass direction. Nearly half the soil slip/debris flows mapped after the catastrophic rainstorm of 3–5 January 1982 occurred on slopes that face S to WSW, whereas fewer than one-quarter have a northerly aspect. Azimuthal analysis of hillside properties for susceptible terrain near the city of Oakland suggests that the skewed aspect of these landslides primarily reflects vegetation type, ridge and valley alignment, and storm–wind direction. Bedrock geology, soil expansivity, and terrain height and gradient also were influential but less so; the role of surface curvature is not wholly resolved. Normalising soil-slip aspect by that of the region's NNW-striking topography shifts the modal azimuth of soil-slip aspect from SW to SE, the direction of origin of winds during the 1982 storm—but opposite that of the prevailing WNW winds. Wind from a constant direction increases rainfall on windward slopes while diminishing it on leeward slopes, generating a modelled difference in hydrologically effective rainfall of up to 2:1 on steep hillsides in the Oakland area. This contrast is consistent with numerical simulations of wind-driven rain and with rainfall thresholds for debris-flow activity. We conclude that storm winds from the SE in January 1982 raised the vulnerability of the Bay region's many S-facing hillsides, most of which are covered in shallow-rooted shrub and grass that offer minimal resistance to soil slip. Wind-driven rainfall also appears to have controlled debris-flow location in a major 1998 storm and probably others. Incorporating this overlooked influence into GIS models of debris-flow likelihood would improve predictions of the hazard in central California and elsewhere.     

Changes in structural style of normal faults due to failure mode transition: First results from excavated scale models

The effects of failure mode transition from tensile to shear on structural style and fault zone architecture have long been recognized but are not well studied in 3D, although the two modes are both common in the upper crust of Earth and terrestrial planets, and are associated with large differences in transport properties. We present a simple method to study this in physical scale models of normal faults, using a cohesive powder embedded in cohesionless sand. By varying the overburden thickness, the failure mode changes from tensile to hybrid and finally to shear. Hardening and excavating the cohesive layer allows post mortem investigation of 3D structures at high resolution. We recognize two end member structural domains that differ strongly in their attributes. In the tensile domain faults are strongly dilatant with steep open fissures and sharp changes in strike at segment boundaries and branch points. In the shear domain fault dips are shallower and fault planes develop striations; map-view fault traces undulate with smaller changes in strike at branches. These attributes may be recognized in subsurface fault maps and could provide a way to better predict fault zone structure in the subsurface.     

超宽带室内多径传播成簇特性

分析了超宽带室内信号的传播规律,即多径分量成簇到达.在实测数据的基础上,研究了信道模型参数的一般规律:簇的到达率Λ应该远小于径的到达率λ,簇的衰减系数Γ应该大于径的衰减系数γ,并修正了IEEE 802.15.3a信道模型CM2环境下的模型参数.仿真结果表明:修正参数后的CM2信道模型优于原模型,更能体现出多径分量成簇到达特性,与实测数据相比较,能更好地拟合实测数据.     

X射线荧光光谱法在耐火材料成分分析中的应用

采用熔融法制样,用X射线荧光光谱法对耐火材料中的Na2O、MgO、Al2O3、SiO2、K2O、CaO、TiO2、Cr2O3、MnO、Fe2O3、ZrO2、HfO2组分进行测定,使用康普顿散射线作内标和经验系数法校正基体效应,经标准物质检验与标准值吻合,大部分组分的RSD<5%(n=10)。     

Simultaneous topology and sizing optimization of viscous dampers in seismic retrofitting of 3D irregular frame structures

A new methodology for performance‐based optimal seismic retrofitting using a limited number of size groups of viscous dampers is presented. The damping coefficient of each size group of dampers is taken as a continuous variable and is determined by the optimization algorithm. Furthermore, for each potential location, a damper of a single size group is optimally assigned, if any. Hence, the formulation presents a large step forward towards practical optimal design of dampers. The key for achieving an efficient optimization scheme is the incorporation of material interpolation techniques that were successfully applied in other structural optimization problems of discrete nature. This results in a very effective optimization methodology that is expected to be very efficient for large‐scale structures. The proposed approach is demonstrated on several example problems of 3D irregular frame structures. Copyright © 2014 John Wiley & Sons, Ltd.     

大兴安岭中段闹牛山铜金矿床的硫铅同位素地球化学特征与成矿物质来源

通过对闹牛山铜金矿床硫、铅同位素的系统研究,探讨了其成矿物质的来源。同位素测试结果表明,δ(~(34)S)=2.0×10~(-3)~3.5×10~(-3),均为正值,呈塔式分布,峰值出现在2.0×10~(-3)~2.5×10~(-3),具幔源硫和陨石硫的特征;矿石铅~(206)Pb/~(204)Pb=18.169~18.510,~(207)Pb/~(204)Pb=15.484~15.646,~(208)Pb/~(204)Pb=37.877~38.431,铅同位素组成较为均一,具正常铅的组成特点;且μ值和ω值偏低,表明矿石铅源区富钍亏铀。在Zartman铅同位素构造模式图解中,投点主要落于地幔与造山带之间和造山带演化线附近;在Δβ—Δγ成因分类图解上,12件测试样品落入上地壳与地幔混合的俯冲带岩浆作用成因铅同位素源区,4件样品落入地幔源铅的范围内,但与两源区界限临近。由此认为,闹牛山铜金矿床的成矿物质主要来源于地幔,并有上地壳物质的混染,这种认识对研究大兴安岭中南段铜多金属矿带的成矿规律具有指导意义。     

土壤界限含水率标准物质研制

界限含水率是细粒土定名分类、评价土的工程性质的重要依据,也是黏土矿勘查和工业利用的重要评价指标。不准确的界限含水率测试结果将可能导致严重的工程安全事故,造成人身和经济财产损失。标准物质是保障分析数据准确、可比和有效的重要手段,但当前国内外尚无土壤界限含水率标准物质,可见研制土壤界限含水率标准物质具有重要的现实意义。基于以上原因,本文严格按照《一级标准物质技术规范》(JJF 1006-1994)和《标准物质定值的通用原则及统计学原理》(JJF 1343-2012)等规范和标准,研制了5个土壤界限含水率标准物质(GBW07969、GBW07970、GBW07971、GBW07972、GBW07973)。候选物样品分别采自安徽淮北、山西大同及江苏南京等地,经人工粗碎、烘干、灭菌等加工处理后,采用大型球磨机将候选物样品细碎至粒径小于0.25mm。混匀、分装后每个候选物随机抽取25瓶进行均匀性检验,F实测值均小于临界值F0.05(24,25)=1.96,相对标准偏差(RSD)介于1.16%~2.67%之间,表明均匀性良好。12个月的考察期内进行的5次长期稳定性检验和考虑两种极端环境温度(60℃、-20℃)的短期稳定性检验,均未发现统计学意义的明显变化,候选物样品稳定性良好。经9家实验室采用2种经典土壤界限含水率测试方法联合定值,10mm液限、塑限和塑性指数3个定值指标的标准值分别介于26.3%~39.9%、16.3%~22.2%、10.0%~17.7%之间,梯度系列显著,涵盖了粉质黏土和黏土两种黏性土类别。该系列标准物质可用于仪器设备校准、质量监控、能力验证等技术质量活动,为水工环地质勘查、岩土工程勘察、黏土矿勘查等工作对土壤界限含水率测试数据准确性的要求提供了保障。     

黄土高原南缘午城黄土底部火山碎屑的来源和成因

一种与多类撞击记录共存的灰黑色碎屑，发现于黄土高原南缘段家坡黄土地层剖面午城黄土底部Ｇａ／Ｍ边界（２．４８ＭａＢ．Ｐ．）附近，通过对此碎屑的矿物学和地球化学特征研究，表明它们最初是源自青藏高原北部及其邻近地区碱性玄武质火山喷发的碎屑物，后来又在表生条件下与黄土层一起经历了包括水解、成土化和氧化等作用在内的风化改造。此外，本文更为强调的是，在火山碎屑形成过程中存在具有富Ｎｉ和Ｃｅ，高Ｓｍ／Ｎｄ比以及低Ｅｕ／Ｓｍ比等特点的地外物质的参与，据以论证这种火山活动确系Ｎ／Ｑ界面撞击事件引发。在黄土地层中，深入研究各种类型的火山碎屑，无疑对全面探讨第四纪环境变迁有着十分重要的意义。关键词午城黄土底部松山－高斯边界火山碎屑风化作用地外物质新近的研究表明，第四纪气候和环境变迁往往与起因于撞击和火山事件的大量尘埃物质有关［１］，而地外物体的撞击又常能引发火山活动［２、３］，因此第四纪沉积物中的火山喷发空落堆积物研究，无疑应该引起更大的关注。火山学发展至今，对各种火山碎屑物质，已有十分详尽的研究［４、５］。从国内第四纪火山碎屑的研究现状来看，虽然丁国瑜等早在１９６４年就曾在河北平原及太行山东麓的黄土地层中，首次发现了火山碎屑堆。