粉质黏土堤防漫溢溃决试验          下载免费PDF全文

魏红艳  余明辉  李义天  吴松柏 《水科学进展》2015,26(5):668-675

为研究粉质黏土堤防漫溢溃决破坏过程及其对水流要素和土体性质的响应规律,以河道流量、筑堤土体含水率和孔隙率为变量,在弯道水槽中开展了9组堤防漫溢溃决概化试验.通过试验发现,粉质黏土堤漫溢溃决溃口发展过程可分为垂向侵蚀和横向扩宽两个阶段,垂向侵蚀阶段以"陡坎"后退为主要形式;筑堤土体含水率与孔隙率不仅影响了溃口垂向侵蚀以及横向扩宽速度,而且决定了溃口最终形态,河道流量主要影响堤防溃口的横向扩宽速度;溃口处流速以及下游水位变化受溃口高度的制约.拟合得到土体黏聚力与土体含水率、孔隙率的相关关系式;通过试验数据提出了由土体黏聚力和水流参数表达的"陡坎"侵蚀后退速度计算公式,证明具有一定合理性.  相似文献   

基质吸力变化引起的体积应变研究     

戚国庆  黄润秋 《工程地质学报》2015,23(3):491-497

与降雨有关的边坡表层变形位移,其根源是基质吸力降低引起的非饱和土体积应变。利用某滑坡体的原状样及其重塑样,分别在100kPa、200kPa围压作用下,采用单纯增加基质吸力的应力路径,对基质吸力引起的体积应变,进行试验测试。结果显示: (1)试样的体应变,随基质吸力的增大,单调增大,服从对数函数关系;(2)围压由100kPa增加到200kPa的试样体积模量,随基质吸力的增大,单调增大,服从幂函数关系;(3)与基质吸力有关的体积变化系数,随基质吸力的增大,单调减小,服从幂函数关系;并且当基质吸力大于200kPa以后,随基质吸力增大,体积变化系数接近于常数,约为0.0059左右。在此基础上,本文针对这种由单纯基质吸力变化引起的非饱和土体积应变规律及机理,进行了探讨。  相似文献   

浅谈高温高压实验地球科学:方法和应用     

杨晓志 《矿物岩石地球化学通报》2015,(3)

在过去的二十多年间,高温高压实验地球科学研究得到了蓬勃发展,凭借其高度的灵活性和易于与其他分支学科相结合的优点,在很多不同的研究领域中都取得了令人瞩目的成果,并已发展成为国际地球科学的前沿领域和重要方向之一,同时也是固体地球科学最强有力研究手段之一。相比之下,国内的高温高压实验地球科学研究还显得相对比较薄弱,相关系统性的认识还有待增强。本文对高温高压实验研究的发展历程、方法原理、仪器设备以及在地球科学研究中的一些应用进行简单的介绍,旨在让更多的国内学者对这一领域有更深入的了解。  相似文献   

二氧化碳洗井中相关问题的探讨     

樊小舟  高波  崔秀忠 《中国煤炭地质》2015,(1):62-65

二氧化碳洗井方法具有设备简单、用时少,效果好的特点,但随着钻孔深度和孔径加大,井管材料的更新换代,有时也会难以出现壮观的井喷场面,达不到理想的洗井效果,使用范围受到限制的问题。总结多年的洗井经验,依据二氧化碳洗井原理,运用洗井过程中起动压力和用气量的计算公式,进而对洗井深度和影响用气量的因素进行了分析,结果表明:1该方法比较适用于井深300m左右、孔径Φ325mm以内、泥浆相对密度小于1.1g/cm3的新打水井,对大于300m的深井,可采用分层洗井法或压风机引喷法进行洗井。2井喷形成时的二氧化碳气体用量,与瓶内气体的压力、钻杆的下入深度、环空体积、地面管路的长度与直径、钻杆内径、钻井液的密度等成正比,而与水温、气温等成反比;当井的含水层的水柱高度低于70m时,一般不易形成井喷。3二氧化碳洗井适用于井内下入钢管、铸铁管等抗压强度较高的井。对水泥管、塑料管等强度较低的井管则要视情况具体分析。  相似文献   

A range of fault slip styles on progressively misoriented planes during flexural-slip folding,Cape Fold Belt,South Africa     

《Journal of Structural Geology》2015

Flexural slip folds are distinctive of mixed continuous-discontinuous deformation in the upper crust, as folding is accommodated by continuous bending of layers and localized, discontinuous slip along layer interfaces. The mechanism of localized, layer-parallel slip and the stress and fluid pressure conditions at which flexural slip occurs are therefore distinctive of shear localization during distributed deformation. In the Prince Albert Formation mudstone sequence of the Karoo Basin, the foreland basin to the Cape Fold Belt, folds are well developed and associated with incrementally developed bedding-parallel quartz veins with slickenfibers oriented perpendicular to fold hinge lines, locally cross-cutting axial planar cleavage, and showing hanging wall motion toward the fold hinge. Bedding-parallel slickenfiber-coated veins dip at angles from 18° to 83°, implying that late increments of bedding-parallel shear occurred along unfavorably oriented planes. The local presence of tensile veins, in mutually cross-cutting relationship with bedding-parallel, slickenfiber-coated veins, indicate local fluid pressures in excess of the least compressive stress.Slickenfiber vein microstructures include a range of quartz morphologies, dominantly blocky to elongate-blocky, but in places euhedral to subhedral; the veins are commonly laminated, with layers of quartz separated by bedding-parallel slip surfaces characterized by a quartz-phyllosilicate cataclasite. Crack-seal bands imply incremental slickenfiber growth, in increments from tens of micrometers to a few millimeters, in some places, whereas other vein layers lack evidence for incremental growth and likely formed in single slip events. Single slip events, however, also involved quartz growth into open space, and are inferred to have formed by stick-slip faulting. Overall, therefore, flexural slip in this location involved bedding-parallel faulting, along progressively misoriented weak planes, with a range of slip increments.  相似文献   

Mass Fractions of S,Cu, Se,Mo, Ag,Cd, In,Te, Ba,Sm, W,Tl and Bi in Geological Reference Materials and Selected Carbonaceous Chondrites Determined by Isotope Dilution ICP‐MS          下载免费PDF全文

Zaicong Wang  Harry Becker  Frank Wombacher 《Geostandards and Geoanalytical Research》2015,39(2):185-208

Mass fractions of S, Cu, Se, Mo, Ag, Cd, In, Te, Ba, Sm, W and Tl were determined by isotope dilution sector field ICP‐MS in the same sample aliquot of reference materials using HF‐HNO₃ digestion in PFA beakers in pressure bombs and glassy carbon vessels in a high‐pressure asher (HPA‐S) for comparison. Additionally, Bi was determined by internal standardisation relative to Tl. Because isobaric and oxide interferences pose problems for many of these elements, efficient chromatographic separation methods in combination with an Aridus desolvator were employed to minimise interference effects. Repeated digestion and measurement of geological reference materials (BHVO‐1, BHVO‐2, SCo‐1, MAG‐1, MRG‐1 and UB‐N) gave results with < 5% relative intermediate precision (1s) for most elements, except Bi. Replicates of NIST SRM 612 glass digested on a hot plate were analysed by the same methods, and the results agree with reference values mostly within 2% relative deviation. Data for the carbonaceous chondrites Allende, Murchison, Orgueil and Ivuna are also reported. Digestion in a HPA‐S was as efficient as in pressure bombs, but some elements displayed higher blank levels following HPA‐S treatment. Pressure bomb digestion yielded precise data for volatile S, Se and Te, but may result in high blanks for W.  相似文献   

The shape of the radio wavefront of extensive air showers as measured with LOFAR     

《Astroparticle Physics》2015

Extensive air showers, induced by high energy cosmic rays impinging on the Earth’s atmosphere, produce radio emission that is measured with the LOFAR radio telescope. As the emission comes from a finite distance of a few kilometers, the incident wavefront is non-planar. A spherical, conical or hyperbolic shape of the wavefront has been proposed, but measurements of individual air showers have been inconclusive so far. For a selected high-quality sample of 161 measured extensive air showers, we have reconstructed the wavefront by measuring pulse arrival times to sub-nanosecond precision in 200 to 350 individual antennas. For each measured air shower, we have fitted a conical, spherical, and hyperboloid shape to the arrival times. The fit quality and a likelihood analysis show that a hyperboloid is the best parameterization. Using a non-planar wavefront shape gives an improved angular resolution, when reconstructing the shower arrival direction. Furthermore, a dependence of the wavefront shape on the shower geometry can be seen. This suggests that it will be possible to use a wavefront shape analysis to get an additional handle on the atmospheric depth of the shower maximum, which is sensitive to the mass of the primary particle.  相似文献   

Study of dispersion of mass distribution of ultra-high energy cosmic rays using a surface array of muon and electromagnetic detectors     

《Astroparticle Physics》2015

We consider a hypothetical observatory of ultra-high energy cosmic rays consisting of two surface detector arrays that measure independently electromagnetic and muon signals induced by air showers. Using the constant intensity cut method, sets of events ordered according to each of both signal sizes are compared giving the number of matched events. Based on its dependence on the zenith angle, a parameter sensitive to the dispersion of the distribution of the logarithmic mass of cosmic rays is introduced. The results obtained using two post-LHC models of hadronic interactions are very similar and indicate a weak dependence on details of these interactions.  相似文献   

Specific Relationship between the Surface Air Temperature and the Area of the Terra Nova Bay Polynya,Antarctica   总被引：1，自引：0，他引：1  

Yifan DING  Xiao CHENG  Xichen LI  Mohammed SHOKR  Jiawei YUAN  Qinghua YANG  Fengming HUI 《大气科学进展》2020,37(5):532-544

Antarctic polynyas play an important role in regional atmosphere?ice?ocean interactions and are considered to help generate the global deep ocean conveyer belt.Polynyas therefore have a potential impact on the Earth’s climate in terms of the production of sea ice and high-salinity shelf water.In this study,we investigated the relationship between the area of the Terra Nova Bay polynya and the air temperature as well as the eastward and northward wind based on the ERA5 and ERAInterim reanalysis datasets and observations from automatic weather stations during the polar night.We examined the correlation between each factor and the polynya area under different temperature conditions.Previous studies have focused more on the effect of winds on the polynya,but the relationship between air temperature and the polynya area has not been fully investigated.Our study shows,eliminating the influence of winds,lower air temperature has a stronger positive correlation with the polynya area.The results show that the relationship between the polynya area and air temperature is more likely to be interactively influenced.As temperature drops,the relationship of the polynya area with air temperature becomes closer with increasing correlation coefficients.In the low temperature conditions,the correlation coefficients of the polynya area with air temperature are above 0.5,larger than that with the wind speed.  相似文献   

一次积-层混合云系垂直结构和降水机制的飞机观测资料分析与数值模拟     

刘香娥  高茜  何晖  马新成  毕凯  赵德龙  周嵬 《气象学报》2020,78(2):277-288

积-层混合云是影响北京地区的重要降水云系,运用飞机探测资料结合中尺度数值模式WRF,对2014年9月23日发生在北京地区的一次积-层混合云系的垂直结构和降水机制进行了探测资料分析和数值模拟研究。通过分析云系的雷达回波演变,发现云中的对流泡没有出现爆发式增长,回波在垂直方向上增长不明显,此次过程属于积-层水平混合型云系降水。飞机探测资料分析显示,上、下午探测云系的液态水含量都不高（最大低于1 g/m3）;在云系不同高度,飞机探测到的冰晶形状主要有板状、针柱状、辐枝状和不规则状,由于云中过冷水含量相对较低,聚合冰晶的数量明显多于凇附冰晶,冰晶的聚合是云中粒子增长的主要过程。对模拟云系垂直微物理结构和降水粒子的源、汇项分析得到:高层,由凝华产生的冰晶和雪晶在过冷水含量较低的环境中不断聚并、长大并下落,云系中霰的含量很低,增大的冰晶和雪晶下落至0℃层附近融化是产生地面降水的主要机制。此外,融化层附近,雨滴捕获云滴不断长大并下降至地面也是地面降水的另一个重要来源。   相似文献