La prospection gravimétrique dans la modélisation d'un substratum sous formation sédimentaire : apport à l'hydrogéologie d'une zone semi-aride du Sud de Madagascar     

Heritiana Rakoto  Pierre Andrieux  Jean-Bruno Ratsimbazafy  Vittorio Iliceto  Eddy Rasolomanana  Louis Pastor  Gian Maria Zuppi 《Comptes Rendus Geoscience》2003,335(4):355-363

A gravimetric survey has been carried out in a sedimentary basin, south of Madagascar, in order to define the bedrock morphology. The bedrock is made up of crystalline and volcanic rocks. The objective of the survey was to demonstrate whether a relationship could be established between bedrock morphology and groundwater mineralisation. Indeed, bedrock morphology has been successfully mapped and it is confirmed that most of the low mineralisation wells are located in areas where the slope of the bedrock is trending to the south-west, which ensures a higher hydraulic conductivity, i.e. a faster water flow, than in the other parts of the survey area. To cite this article: H. Rakoto et al., C. R. Geoscience 335 (2003).  相似文献   

贵州水城曾家包包大型基岩滑坡的成因机制及稳定性     

刘涛  李渝生  汪波 《山地学报》2005,23(3):342-347

从滑坡的地质环境入手，通过地质调研及测绘，分析曾家包包大型基岩滑坡的特征、控制因素及成因机制，并运用sama法及不平衡推理法、毕肖普法对滑坡稳定性极限平衡进行计算分析。在此基础上，对在现今应力场作用下滑坡的稳定性采用了有限元模拟，并对模拟的结果进行分析，得出在天然条件下曾家包包滑坡曾处于稳定状态，岩体中的软弱夹层经长期持续的地下水浸润软化逐渐泥化形成倾角上陡下缓的贯通性滑移面，在雨季降雨异常集中期，岩体排水不畅形成较高的空隙水压力，斜坡岩体就会沿滑移面发生顺层滑移，从而形成大型基岩滑坡。  相似文献   

Bedrock lithology control on contemporaneous alluvial fan facies, Oligo-Miocene, southern Pyrenees, Spain   总被引：1，自引：0，他引：1  

GARY NICHOLS†  BEN THOMPSON 《Sedimentology》2005,52(3):571-585

Climate and tectonics play important roles in controlling processes of transport and deposition on alluvial fans, but the bedrock lithology in the fan catchment area is also a significant, independent factor. Adjacent Oligo-Miocene alluvial fan deposits on the northern margin of the Ebro Basin display contrasting depositional characteristics with one dominated by the deposits of debris flows and the other by deposition from flows of water. A difference in clast compositions indicates that the two studied fans (the Nueno and San Julián fans) had contrasting bedrock lithology in their drainage basins. The proximal facies of the Nueno fan body contains matrix-supported conglomerate beds with up to 80% pebble clasts of gypsum in a matrix of gypsiferous sand, interbedded with gypsarenite beds. The drainage basin of this fan was dominated by Triassic bedrock consisting of beds of gypsum, marl and micritic limestone. The San Julián fan body comprises clast-supported, polymict conglomerate beds containing pebbles from Triassic, Cretaceous and Palaeogene limestone units that are exposed in the adjacent part of the basin margin. The interfingering of the deposits of these two fans demonstrates that they were contemporaneous. Given the consistent climate, the differences in fan depositional processes must therefore be attributed to the contrasting bedrock lithology in their drainage basins. A drainage basin consisting mainly of marl and gypsum bedrock provided sufficient fine-grained material to generate debris flows, whereas more dilute, water-lain processes dominated where the drainage basin was largely limestone strata.  相似文献   

浅埋深、薄基岩、厚松散含水层下煤层综合机械化开采防治水技术应用   总被引：1，自引：0，他引：1  

张文义 《中国煤田地质》2004,16(4):39-41

神东煤炭公司大柳塔矿12404工作面煤层埋深浅，上覆基岩薄、松散含水层厚，且地表有河流横过(工作面长度240m，推进度3900m，其中薄基岩富水段150m)，为了减少工作面搬家次数提高生产效益，采取了地面抽排水、井下泄放水及地面注浆固沙等有效的防治水措施，工作面安全通过了母河沟，该防治水方法的应用改变了以往类似情况进行留煤柱跳采的方法，取得了浅埋深薄基岩厚含水层下煤层综合机械化安全开采经验，比停产跳采节省搬家费用2400万元，获得了显著的经济效益。  相似文献   

Fluoride concentrations in a crystalline bedrock aquifer Marathon County, Wisconsin     

David L. Ozsvath 《Environmental Geology》2006,50(1):132-138

Water samples from 2,789 private water-supply wells in Marathon County, Wisconsin reveal that fluoride concentrations in the crystalline bedrock range from <0.01 to 7.60 mg/L, with 0.6% of the values exceeding the Environmental Protection Agency’s (EPA’s) maximum contaminant level of 4 mg/L, and 8.6% exceeding the EPA’s secondary maximum contaminant level of 2.0 mg/L. Roughly a quarter of the wells contain dissolve fluoride within the range considered optimal for human health (between 0.5 and 1.5 mg/L), whereas 63.3% fall below 0.5 mg/L. Consistent with studies conducted in other regions, felsic rocks have significantly higher fluoride concentrations than mafic and metasedimentary rocks. Syenites yield the most fluoriferous groundwaters, but the highest median concentration occurs in a sodium-plagioclase granite. A relationship between plagioclase composition and fluoride concentrations suggests that dissolved fluoride levels are controlled by fluorite solubility and that higher fluoride concentrations are found in soft, sodium-rich groundwater.  相似文献   

天津城市三维地质结构调查工作方法的应用     

李继军 《华北地质》2006,29(3):233-240

本文中对天津城市三维地质结构调查的工作方法进行了探讨,提出了天津松散层地质结构调查、工程地质结构调查、水文地质结构调查和基岩地质调查的工作思路和技术方法,特别指出利用物探资料进行二次开发研究对深覆盖区三维地质结构调查和建立三维地质结构具有重要的意义,并对其进行了充分地论述。  相似文献   

太仓—奉贤北西向活动断裂带及其地震地质意义初探   总被引：5，自引：0，他引：5  

顾澎涛  邱金波 《上海国土资源》1990,(3):1-6

根据晚新生代以来沉积建造、沉积环境、岩浆活动、岸线变迁、地貌及现代地震等资料判断,太仓—奉贤北西向断裂带是上海及邻近地区一条重要的活动性断裂构造带。  相似文献   

Nonlinear surface ground analysis via statistical approach     

Izuru Takewaki  Nobuyoshi Fujii  Koji Uetani 《Soil Dynamics and Earthquake Engineering》2002,22(6)

A statistical approach is proposed for nonlinear surface ground analysis. In contrast to the conventional method which deals with only a single ground motion for equivalent linearization of soil properties, a design response spectrum defined at the upper level (bottom of the surface ground) of an engineering bedrock can be handled as the target design earthquake in the present paper. The effective shear strain in each soil layer is evaluated by means of a statistical procedure in which the mean peak shear strain is computed in terms of its standard deviation and the corresponding peak factor. The stiffness and damping ratio of each soil layer are obtained iteratively from the nonlinear relation of stiffness reduction factors and damping ratios with respect to the strain level. After the evaluation of the equivalent stiffness and damping ratio of every soil layer, the ground surface response spectrum is transformed from the design response spectrum defined at the upper level of the engineering bedrock via the one-dimensional wave propagation theory. The reliability and accuracy of the proposed analysis method is examined through the comparison with the results by the conventional method (represented by the program) for many simulated spectrum-compatible ground motions.  相似文献   

基岩冲刷的数值模拟   总被引：2，自引：0，他引：2       下载免费PDF全文

邓军  许唯临  杨忠超  曲景学 《水科学进展》2005,16(1):47-51

为了探索采用数值模拟的方法来研究基岩冲刷的可行性,对二维散粒体河床的冲刷进行了试验研究,并采用二维k-ε模型,在贴体非正交曲线坐标系中用控制体积法对散粒体河床的冲刷进行了数值模拟,计算的冲坑深度与试验结果符合很好,结果令人满意.选用相同的控制基岩冲刷的参数,对不同下游水垫深度、不同入射流速时基岩冲刷深度的正确模拟说明,在对基岩特性有了充分的了解后,用数值方法来模拟基岩的冲刷过程及估算冲刷深度是合理、可行的.  相似文献   

潜导水及其在地下工程洞体突水中的作用     

孙峰根  杨立昂 《水文地质工程地质》1998,25(6):19-21

本文提出了潜导水的概念,并通过对潜导水主要特征、潜导水压传递原理、潜导水压大小的分析,阐述了潜导水在地下工程洞体突水中的作用。  相似文献