管土摩擦和管径对埋地管道破坏的影响分析

如何分析管土摩擦和管径对埋地管道地震破坏的影响,是城市地下管道建设中面临的突出问题。采用AD INA软件的定义体操作来选择体类型,并应用布尔操作实现了管道与土体和断层之间的融合,得到地下管道破坏分析的几何模型。通过模型参数选择,确定了岩土性质、管道特性、断层等模型参数,定义了管土摩擦、地震荷载时间函数、断层位移荷载。依据计算结果,分析了管土摩擦和管径对地下管道地震破坏的影响,找出了提高埋地管道抵抗破坏能力的摩擦系数和管径最优值,给出了几点工程建议。     

Air density effects on aeolian sand movement: Implications for sediment transport and sand control in regions with extreme altitudes or temperatures

Aeolian sand transport results from interactions between the ground surface and airflow. Previous research has focused on the effects on sand entrainment and mass transport of surface features and wind velocity, but the influence of air density, which strongly constrains airflow characteristics and the resulting sand flow, has not been widely considered. In the present study, entrainment, saltation characteristics and transport rates were examined at nine experimental sites ranging in elevation from ?154 m below sea‐level (Aiding Lake) to 5076 m above sea‐level (Tanggula Mountain pass on the Qinghai–Tibetan plateau). At each site, a portable wind tunnel and high‐speed camera system were set up, and the friction wind velocity, threshold friction velocity and sand flow structure were observed systematically. For a given volumetric airflow, lower air density increases the wind velocity. Low air density also creates a high threshold friction velocity. The Bagnold wind erosion threshold model remains valid, but the value of empirical parameter A decreased with decreasing air density and ranged from 0·10 to 0·07, the smallest values reported in the literature. For a given wind velocity, increased altitude reduced total sand transport and creeping, but the saltation rate and saltation height increased. The present results provide insights into the fundamental mechanisms of the initiation and transport of sand by wind in regions with an extreme temperature or altitude (for example, alpine deserts and low‐lying lake basins) or on other planets, including Mars. These results also provide theoretical support for improved sand‐control engineering measures. The data and empirical equations provided in this paper improve the ability to estimate threshold and transport conditions for wind‐blown sand.     

新疆西准噶尔地区不同尺度地质构造的遥感标识特征及找矿意义

哈图金矿、包古图斑岩型铜金钼矿、杨庄铍铀矿及加曼钼钨铜矿等大型矿床的相继发现,使西准噶尔地区的地质找矿工作备受关注。作为重点研究对象,西准噶尔地区的地质构造研究已获得大量成果。但是,该区地域辽阔且地质构造较为复杂,传统的地质学研究方法不可能快速、有效和完全准确的解决地质构造的空间分布及规模等问题。利用多种分辨率的卫星遥感数据,通过遥感标识体系的建立能够客观、准确获取不同尺度地质构造的空间位置及规模。宏观和中等尺度的断裂构造均以明显的直线或弧形等形态特征、光谱特征(色调差异)及断层谷地、断层陡坎等地貌特征为主要标识,但侧重点有所不同;微观尺度即矿集区尺度的断裂构造地貌上为笔直的短小沟谷,常常需用弱信息挖掘方法才能突出构造的线性信息。通过独特的形态特征可快速识别褶皱构造。根据环形影像特征、色调差异及环形水系特征可识别不同尺度的岩体和(或)隐伏岩体。因此,地质构造的遥感识别可为地质构造演化及成矿构造背景分析提供科学依据;为西准噶尔地区成矿带(亚带)划分、遥感找矿模型的建立及高效圈定靶区等提供准确的空间信息依据。     

雅丹地貌研究评述与展望

雅丹地貌是风蚀地貌研究的重要对象,目前研究较为薄弱.雅丹地貌自瑞典探险家斯文赫定命名并开始研究以来,已有百余年的历史.随着科学技术的不断进步和研究方法的更新,已取得了重要进展,但仍存在许多问题.首先对雅丹地貌的科学定义、空间分布、形态特征、形成发育条件、形成发育过程、形成年代、与环境的关系和分类等8方面的进展和问题进行...     

Abundance and characteristics of microplastics in shellfish from Jiaozhou Bay,China

As an emerging pollutant, the presence of microplastics in marine organisms has been concerned increasingly. Shellfish, which are both economically and ecologic...     

内蒙古双尖子山银多金属矿床区域地球化学特征

内蒙古双尖子山银多金属矿床是中国乃至亚洲规模最大的银多金属矿床,本研究在回顾矿床发现史的基础上对双尖子山矿床区域地球化学数据进行再分析。采用19级累积频率法制作研究区39种元素或氧化物的地球化学图,结果发现在双尖子山矿区范围内出现明显高值的有MgO、CaO、Fe₂O₃、Pb、Zn、Ag、V、Cr、Ni等多达22种氧化物或元素,其中主量成分的明显富集特征应受控于研究区的岩性分布情况。采用变值七级异常法制作研究区29种微量元素的地球化学异常图,结果发现在双尖子山矿区及其附近存在W、Sn、Mo、Bi、Pb、Zn、Ag、As、Sb计9种热液成矿元素的异常区,而其他微量元素在双尖子山矿区的明显富集情况可能是由双尖子山矿区及其附近母岩岩性及其风化作用所致。基于地球化学基因技术制作了研究区金矿化基因和钨矿化基因的矿化相似度地球化学图,结果发现在双尖子山矿区及其附近存在金矿化相似度和钨矿化相似度的异常区,表明矿化相似度可以作为该区金属矿产勘查的一种有效指标,认为区域化探工作在该区金属矿产勘查中具有很好的参考价值。     

广东汕头市内海湾沉积物重金属环境质量调查与评价

内海湾底泥沉积物的环境质量状况与水生生物的生存和人体健康关系密切。在广东汕头市内海湾两岸23个点位采集了表层(0~20 cm)和深层(100~120 cm)底泥沉积物样品46件,对其pH值和Cd、Hg、As、Pb、Cr、Cu、Zn计7项重金属及K含量进行测试分析,调查底泥中这些重金属的含量特征,并参照农用地水田土壤污染风险管控标准对重金属环境污染质量进行评价。结果表明汕头内海湾底泥沉积物的pH介于7.00~8.82之间,平均值为7.83,在46件样品中41件样品的pH值大于7.5。内海湾底泥中7项重金属元素的含量均明显低于环境污染风险管制值,即对该区底泥重金属环境污染不需要管制。Cd、As、Pb、Cr这4项重金属含量均低于污染风险筛选值,其污染风险可以忽略。2件表层样品的Hg含量值高于污染风险筛选值,18件样品的Cu和Zn含量值高于污染风险筛选值,因此建议对底泥中Cu、Zn、Hg含量进行环境质量监测。K含量介于0.70%~2.59%,平均值为1.54%。基于表层底泥和深层底泥元素含量对比分析,认为该区Hg污染来源应为人为源;Cu、Zn的污染来源一部分为人为源,另一部分可能为人为源、自然源或二者的混合源。     

青藏铁路沿线砾石方格固沙机理风洞模拟研究

通过对青藏铁路沿线砾石方格内风速特征、固沙效率的风洞模拟实验研究发现,当气流运行至砾石方格前缘,水平风速迅速降低,砾石方格对风速的削弱作用非常显著,达到50%左右。气流在沿砾石方格向下风向移动过程中,水平梯度风速逐渐减小,但其减小幅度比较缓慢。砾石方格中风速随高度的分布遵循对数规律,各方格间风速变化趋势相对稳定。砾石方格地表粗糙度在5.2cm左右,摩阻速度为2.4 cm/s。砾石方格中固沙量随着进口风速的增加而增加,在相同风速下,固沙量随离沙源距离的增加呈指数关系递减。     

Wind tunnel investigation of the influence of surface moisture content on the entrainment and erosion of beach sand by wind using sands from tropical humid coastal southern China

Wind erosion has major impacts on dune growth, desertification, and architecture on sea coasts. The deflation threshold shear velocity is a crucial parameter in predicting erosion, and surface moisture greatly affects this threshold and thus sand stability. Wind tunnel studies have shown that reduced moisture contents decrease entrainment thresholds and increase wind erosion, but field and wind tunnel test data is lacking for tropical humid coastal areas. In this study, we investigated the influence of surface moisture contents (at 1 mm depth) on sand entrainment and erosion using tropical humid coastal sands from southern China. Shear velocities were deduced from velocity profiles above the sand. The threshold shear velocity increased linearly with increasing ln100M (M, gravimetric moisture content). The increase was steepest below a moisture content of 0.0124 (i.e., at M_1.5, the moisture content in the sand at a matric potential of − 1.5 MPa). We compared several popular models that predict threshold shear velocity of moisture sediment, and found substantial differences between their predicted results. At a surface moisture content of 0.0124, the predicted increase in the wet threshold shear velocity compared with the dry threshold shear velocity ranged from 34% to 195%. The empirical model of Chepil and Selah simulated the data well for M < 0.0062 (i.e., 0.5M_1.5), whereas Belly's empirical model simulated the data best for M > 0.0062. Wind erosion modulus increased with increasing effective wind velocity following a power function with a positive exponent at all moisture contents, but decreased with increasing surface moisture content following a power function with a negative exponent. When wind speed and moisture content varied simultaneously, wind erosion modulus was proportional to the 0.73 power of effective wind velocity, but inversely proportional to the 1.48 power of M. The increase in resistance to erosion at low moisture contents probably results from cohesive forces in the water films surrounding the sand particles. At a moisture content near M_1.5, wind erosion ceases nearly for all wind velocities that we tested.     

鲁中南典型岩溶水系统地下水污染预警评价

地下水污染预警是区域地下水资源保护的重要手段.山东双村岩溶水系统是典型的鲁中南单斜构造型岩溶水系统之一,现开采量39.848万m3/d,为特大型岩溶水源地.30余年的水质监测数据表明,岩溶水水质逐渐变差、水化学类型变复杂.在查明水文地质条件、污染源调查和长序列水质监测的基础上,构建了有针对性的地下水污染风险评价指标体系...