裂隙概化模型的非饱和渗流试验研究

借鉴多孔介质非饱和渗流试验的研究成果,研制出一套可同时测定单裂隙毛细压力-饱和度以及非饱和渗透系数-毛细压力关系的试验装置.为检验试验装置的可信度和试验原理的正确性,并初步探讨单裂隙非饱和渗流的机理,特制作了一阶梯开度的裂隙概化模型(本文称之为“S-H”裂隙模型),并在上述试验装置上进行了“S-H”裂隙模型的非饱和渗流试验,初步阐明了单裂隙非饱和渗流的一些基本水力特性,同时试验结果也表明本文试验装置和试验原理合理可靠.     

青藏高原中部北北东向深部负磁异常带的成因及其意义

根据最新测量获得的青藏高原中西部航磁异常图 ,经不同高度向上延拓后 ,发现在测区东部 ,即青藏高原中部自柴达木向西南延伸的广大地区 ,出现一条极为明显的北北东向负磁异常带。从对航磁区域场的分析 ,并结合人工地震、重力计算莫霍面深度、热水活动、最新火山岩活动、地貌特征和天然地震活动等多种资料的解释 ,认为负异常带是由于深部热流沿北北东向上升引起局部岩浆熔融 ,使上地壳下部具有较高的地温 ,导致磁性层底部消磁作用的结果。与此同时也加快了青藏高原隆升的幅度 ,为高原形成和演化的研究提供了新的证据     

基岩水的壁间运动及基本特征

本文通过对基岩水与孔隙水的比较分析，介绍了基岩水的分布、水动力学和水化学特征，指出了基岩水运动具有均位趋势、选择流动及汇流特性，得出了渗流理论不宜用于基岩水的结论。     

滑坡-碎屑流冲击导引结构的离散元模拟

滑坡碎屑流对拦挡结构的直接冲击常产生较高的峰值冲击力和冲击能量,导致结构发生破坏而失效;而导引结构通过改变碎屑流的运动路径,可减缓其冲击效应,提高结构抗冲击能力。文章运用三维离散元模拟软件,结合室内休止角试验的结果,校准数值模拟参数,以三种不同导引结构(凹型圆弧、直线型、凸型圆弧)为变量进行数值模拟分析。研究结果表明:凹型圆弧结构B1可以有效地将碎屑流颗粒的冲击力进行转化,结构所受的法向力最小,切向力最大,对颗粒的导引作用最大。经过三种不同导引结构后,颗粒与滑槽之间的碰撞和摩擦是导致颗粒动能减小的主要原因;而三种不同导引结构对颗粒动能的耗散效果无显著差异。导引结构的作用对于颗粒堆积体积分布有显著的影响,主要影响区是靠近坡脚处,对导引结构之后的堆积区域的颗粒体积分布影响不显著。通过对冲击效应和堆积特性的研究,得到凹型圆弧结构形式最优,可以为碎屑流的防护工程抗冲击设计提供参考。     

滨海城市地表水资源可利用量分析——以广西钦州市为例

以钦州市为例,根据1956～2016年月降雨、径流数据,采用双累积曲线(DMC)模型和蒸发差值法计算地表水资源量,采用剔除入海河流感潮河段水量及汛期河道内最小生态水量的改进扣损法和直接法综合分析地表水资源可利用量。结果表明:钦州市地表水资源量在106.573～111.216×10~8m~3范围内,地表水资源可利用量为38.444×10~8m~3,占比地表水资源总量的34.6%。钦州市水量相对丰富,但水资源可利用量并不富裕且时空分布不均。空间上,独流入海河流分区地表水资源可利用量最多,南流江分区次之,郁江干流分区最少;时间上,19条流域汛期水量高达81.949×10~8m~3,其中难以控制利用量为62.272×10~8m~3,有35.823×10~8m~3经入海河流直接外排入海;4.973×10~8m~3为感潮河段咸水难以利用;调水工程的规划与建设为改善河道环境、缓解供需矛盾方面起到积极作用。     

Determination of Zirconium, Niobium, Hafnium and Tantalum at ng g-1 Levels in Geological Materials by Direct Nebulisation of Sample HF Solution into FI-ICP-MS

We have developed a rapid and accurate method to determine Zr, Nb, Hf and Ta (denoted as HFSE) in geological samples by inductively coupled plasma-mass spectrometry fitted with a flow injection system (FI-ICP-MS). The method involves sample decomposition by HF followed by HF dissolution of HFSE coprecipitated with insoluble M and Ca fluoride residues formed during the initial HF attack. This HF solution was directly nebulized into an ICP mass spectrometer. An external calibration curve method and an isotope dilution method (ID) were applied for the determination of Nb and Ta, and of Zr and Hf, respectively. Recovery yields of HFSE were > 96% for peridotite, basalt and andesite compositions, apart from Zr and Hf for peridotite (> 85%). No matrix effects for either signal intensities of HFSE or isotope ratios of Zr and Hf were observed in basalt, andesite and peridotite solutions down to a dilution factor of 100. Detection limits in silicate rocks were 40, 2, 1 and 0.1 ng g-1 for Zr, Nb, Hf and Ta, respectively. This technique required only 0.1 ml of sample solution, and thus is suitable for analysing small and/or precious samples such as meteorites, mantle peridotites and their mineral separates. We also present newly determined data for the Zr, Nb, Hf and Ta concentrations in USGS silicate reference materials DTS-1, PCC-1, BCR-1, BHVO-1 and AGV-1, GSJ reference materials JB-1, -2, -3, JA-1, -2 and -3, and the Smithsonian reference Allende powder.     

Key signatures of turbidite and sandy debris and core examples in Liaohe Basin

Gravity flow is a widely-distributed fluid type in nature. Various classification schemes of gravity flow are proposed by different researchers from different viewpoints. The scheme of turbidity flow and debris flow is adopted in this paper. The sedimentary characteristics of turbidite and sandy debrite are summarized and discussed to clarify most typical facies marks of these two rock types. The study shows that turbidite and sandy debris can be identified by the following typical characteristics during the outcrop and core observation: If the graded bedding is developed in sandstone,it should be identified as turbidite;if the muddy rip-up clast or no bedding structure(massive sandstone)is developed in sandstone,it should be identified as sandy debris. These characteristics are the most reliable signatures to distinguish turbidite and sandy debris. In addition,some other sedimentary structures such as deformation bedding,climbing ripple cross bedding,wavy bedding,parallel bedding,scouring surface,lithologic abrupt interface,and flute cast also have certain indicative significance. It is necessary to make a comprehensive judgment based on the sedimentary background,vertical combination of lithofacies,geophysics and other materials when these characteristics are presented in the study.     

GIS Spatial-Temporal Modeling of Water Systems in Greater Toronto Area, Canada

Modeling landscape with high-resolution digital elevation model (DEM) in a geographic information system can provide essential morphological and structural information for modeling surface processes such as geomorphologic process and water systems. This paper introduces several DEM-based spatial analysis processes applied to characterize spatial distribution and their interactions of ground and surface water systems in the Greater Toronto Area (GTA), Canada. The stream networks and drainage basin systems were derived from the DEM with 30 m resolution and the regularities of the surface stream and drainage patterns were modeled from a statistical/multifractal point of view. Together with the elevation and slope of topography, other attributes defmed from modeling the stream system, and drainage networks were used to associate geological, hydrological and topographical features to water flow in river systems and the spatial locations of artesian aquifers in the study area. Stream flow data derived from daily flow measurements recorded at river gauging stations for multi-year period were decomposed into “drainage-area dependent“ and “drainage-area independent“ flow components by two-step “frequency“ and “spatial“ analysis processes. The latter component was further demonstrated to relate most likely to the ground water discharge. An independent analysis was conducted to model the distribution of aquifers with information derived from the records of water wells. The focus was given on quantification of the likelihood of ground water discharge to river and ponds through flowing wells, springs and seepages. It has been shown that the Oak Ridges Moraine (ORM) is a unique glacial deposit that serves as a recharge layer and that the aquifers in the ORM underlain by Hilton Tills and later deposits exposed near the steep slope zone of the ridges of ORM provide significant discharge to the surface water systems (river flow and ponds) through flowing wells, springs and seepages. Various statistics (cross- and auto-correlation coefficients, fractal R/S exponent) were used in conjunction with GIS to demonstrate the influence of land types, topography and geometry of drainage basins on short- and long-term persistence of river flows as well as responding time to precipitation events. The current study has provided not only insight in understanding the interaction of water systems in the GTA, but also a base for further establishment of an on-line GIS system for predicting spatial-temporal changes of river flow and groundwater level in the GTA.     

静止环境中有阻力圆盘浮力射流特性的研究——(II)流场特性分析

在数值计算成果的基础上,对阻力圆盘浮力射流的流场进行了分析和总结,基于轴线流速的变化规律将盘后流场分为3个区域:回流区、过渡区和自相似区。得到了回流区的长度随弗劳德数F0、孔口直径D/d以及盘离孔口的距离H/d的变化规律,并得到了工况为H/D=1,D/d=2,6和H/D=3,D/d=2在不同弗劳德数F0条件下的横截面上的流速分布和达到自相似区的最小长度;结果表明弗劳德数F0的大小是决定绕流流态的主要因素;同时分析了由正常绕流发展到非正常绕流的压力场变化,发现由于弗劳德数F0的增大而导致流场中出现的第三个负压中心的大小和位置与绕流是否能正常发生存在密切的关系。     

Curie Point Depths Beneath Precordillera Cuyana and Sierras Pampeanas Obtained from Spectral Analysis of Magnetic Anomalies

A gravity and magnetic survey has been carried out with the purpose of investigating geophysical features of the crusts beneath three geological provinces in western Argentina: Cuyo Precordillera, the Sierras Pampeanas of San Juan and La Rioja, and Famatina System, the results of which are displayed in three maps: Bouguer anomaly, total field magnetic anomaly and total field reduced to the pole.

The top and bottom boundaries of the magnetized crust were calculated from power-density spectra of the total-field anomalies from our terrestrial database in 90 2D windows. The depths obtained for the bottom of magnetized crust are assumed to correspond to Curie point depths. The values thus obtained for the Precordillera range between 29 and 40 km, whereas for the Sierras Pampeanas, in the Sierra de Pie de Palo, and other mountain chains along the Bermejo-Desaguadero lineament or Valle Fértil lineament, such depth ranges between 20 and 35 km. These results are consistent with Curie point depths determined on different continental regions in the world.

A map of regional heat flow has been prepared in the present work based on the depth of the Curie point isotherm, which shows that heat flow patterns in Precordillera are different from those found in Sierras Pampeanas.

A significant heat flow extending in Northeast-Southwest direction seems to be directly related to Juan Fernández Ridge trace.

The results of the present investigations also point out a possible relationship between the base of the magnetized crust and the boundary separating the brittle from the ductile crustal regime.