共查询到20条相似文献，搜索用时 31 毫秒
1.
河谷深厚覆盖层工程地质特性及其评价方法 总被引：2，自引：1，他引：2
河谷深厚覆盖层广泛分布于我国大江大河中，其研究对加我国水利水电工程建设具有重大。意义。文中以川西河流为例，论述河谷深厚覆盖层的基本特征及工程地质特性，并重点论述河谷深厚覆盖层的承载力、变形 、强度参数及渗透特性的评价方法。 相似文献
2.
David J. Grimes Walter H. Ficklin Allen L. Meier John B. Mchugh 《Journal of Geochemical Exploration》1995,52(3)
Ground-water, alluvium, and bedrock samples were collected from drill holes near the Chimney Creek, Preble, Summer Camp, and Rabbit Creek disseminated gold deposits in northern Nevada to determine if Au and ore-related metals, such as As, Sb, and W, are being hydromorphically mobilized from buried mineralized rock, and, if they are, to determine whether the metal-enriched ground water is reacting with the alluvial material to produce a geochemical anomaly within the overburden.Results of chemical analyses of drill-hole water samples show the presence of hydromorphic dispersion anomalies of Au, As, Sb, and W in the local ground-water systems associated with these deposits. Background concentrations for Au in the ground water up-gradient from the buried deposits was less than 1 nanogram per liter (ng/L), near the deposits the Au values ranged from 1 to 140 ng/ L, and in drill holes penetrating mineralized rock, concentrations of Au in the ground water were as high as 4700 ng/L. Highest concentrations of Au were found in ground-water samples where the measured Eh and the distribution of arsenic species, arsenite [As(III)] and arsenate [As(V)], indicated oxidizing redox potentials. Similarly, As, Sb, and W concentrations in the ground water near the deposits were significantly enriched relative to concentrations in the ground water up-gradient from the deposits. In general, however, the highest concentrations of As, Sb, and W occurred in ground-water samples where the measured Eh and the distribution of arsenic species indicated reducing conditions. Arsenic concentrations ranged from 9 to 710 micrograms per liter (μg/L); Sb, from less than 0.1 to 250 μg/L; and W, from 1 to 260 μg/L.In addition, analysis of sequential dissolution and extraction solutions of drill cuttings of alluvium and bedrock indicate geochemical anomalies of gold and ore-related metals in the overburden at depths corresponding to the location of the present-day water table. This relationship suggests that water-rock reactions around these buried deposits are active and that this information could be very useful in exploration programs for concealed disseminated gold deposits. 相似文献
3.
Engineering-geological mapping of tropical soils for land-use planning and geotechnical purposes: A case study from Jamaica, West Indies 总被引：2，自引：0，他引：2
An area of a Tertiary and Cretaceous deposits, 100–310 m above sea level and on predominant 20–45°, highly dissected, concave slopes was investigated to assess its geotechnical characteristics and land use planning implications. Lithologies include turbidites, fluvial conglomerates, breccias, sandstones, mudrocks, carbonates, granodiorite, acid dykes, chloritized and epidotized volcanics, andesite and Holocene fluvial deposits. Bedrock is highly fractured and sheared, hydrothermally altered and highly weathered. Soils are quite variable, with a strong geological control on soil properties. Soils are generally sandy to gravely, with local silts and clays in mudrocks, within Holocene alluvium or in hydrothermally altered and sheared granodiorites. The soils are composed of 0.14–80.00% gravel; 5.36–62.50% sand, 2.33–50.55% silt, 0.17–51.50% clay, and total fine content between 2.50 and 94.50%, with natural moisture between 4 and 44% during the dry season, plastic limit between 6 and 35%, liquid limit between 19 and 83% and plasticity index between 1 and 59%. Sandy soils have residual friction angles between 19 and 39°, PI values less than 35% with cohesion between 1.00 and 5.27 KN/m2 for cohesive samples. ASTM classification of soils include soil groups GC, GM, GW, GP, SP, SM, SC, SM, SC, ML, CL and CH.
Based on the characteristics of the terrain, the geotechnical and land use planning problems include high landslide frequency and susceptibility, soil erosion, fluvial and reservoir sedimentation, high debris flow hazard, cut slope failures, potentially expansive clays and silts, seepage erosion and soil piping, differential settlement in interlayered competent and incompetent lithologies, high solution erosion and potential subsidence over limestones, waste water disposal problems and groundwater pollution and seismic induced settlement and ground failures. These phenomena suggest that systematic site investigations should be conducted prior to the utilization of these areas for construction and development in order to minimize the deleterious effects resulting from ground failure. 相似文献
4.
This paper presents a preliminary study of time evolution and spatial accumulation of progressive failure for ancient landslide deposits in Xinhua slope. According to the geological response after impoundment, the Xinhua slope has shown the spatial accumulation of deformation, such as ground cracks in the rear edge, toe collapse, local shallow slides in intense rainfall, and progressive creep displacement. Approximately 2 years of monitoring was performed for the Xinhua slope with the assistance of the global navigation satellite system (GNSS), unmanned aerial vehicles (UAVs), and field investigations. The deformation process of a reservoir landslide is considered to be a comprehensive and complicated combination of geological influence from various adverse factors. Field investigations and monitoring indicate that the major serious influence after completion of dam construction comes from the initial large-scale impoundment, the fluctuation of water level, and the existence of a flood season. The creep/slip deformation of slope deposits is a result of integration with adverse hydraulic conditions, e.g., strong rainfall, intense currents and transient seepage flow inside the slope deposits, and activation by water level fluctuation, which can be verified from the twofold evident deformation in the flood season. For the reservoir with daily regulation ability, the occurrence of evident deformations in July highlights that the regulation plan for water level in the flood season is important for controlling the deformation of slope deposits, where the fluctuation of the water level is no more than 10 m in the operation period. 相似文献
5.
潜蚀是深厚覆盖层渗透稳定性问题中比较主要和突出的一种表现型式,开展深厚覆盖层潜蚀问题的相关试验及理论研究,对于保障中国已建、待建重大水电工程的安全均具有重要的理论和实际意义。首先,区分了潜蚀与向后侵蚀管涌,指出潜蚀与向后侵蚀管涌的发生机制完全不同,两者不能混淆在一起。与向后侵蚀管涌相比,潜蚀更具隐蔽性,其发生发展机制更加复杂。其次,从潜蚀发生的几何条件、水力条件及潜蚀数学模型等3个方面详细梳理总结了潜蚀研究的相关进展。最后,结合雅鲁藏布江下游水电开发等国家重大工程,提出未来应着重加强对原状覆盖层土体内部稳定性评价,对极端条件、复杂渗流条件、复杂地层条件下潜蚀发生发展机制,潜蚀时间效应及其长期影响的评价和控制,对潜蚀本构关系及其数学模型等方面的试验及理论研究。 相似文献
6.
内蒙古查汗套海滩生态建设区地下水潜水流动系统由上更新统冲积层孔隙潜水流动子系统（Q3al）、中更新统冲积层孔隙潜水流动子系统（Q2al）、基岩孔隙潜水流动子系统、全新统风成砂孔隙潜水流动子系统（Q4eol）以及全新统冲积孔隙潜水流动子系统（Q4al）组成.其中主要开采地下水目的层为Q3al,其他子系统都为Q3al子系统地下水的补给系统之一.Q3al、Q4eol及基岩潜水流动子系统都接受大气降水入渗补给,最终通过Q3al的东侧边界排入黄河.在天然条件下,Q3al子系统在洪峰、凌汛期受黄河水补给,其他时期排泄于黄河. 相似文献
7.
8.
在分析研究坎儿井主要技术特点的基础上,结合河流冲洪积扇地形地貌特征、储水构造以及水资源转化特点,提出了建设山前凹陷带"横坎儿井式"地下水库的具体思路,并以台兰河地下水库示范工程为例,对构筑"横坎儿井式"地下水库的可行性及其"引渗回补"调蓄系统、"横坎儿井"集水系统、"自流虹吸"输水系统三大工程组成部分的结构设计原理进行了初步的探讨.山前凹陷地下水库是非常理想的应急抗旱水源工程,其研究和示范工程,为干旱区内陆河流域地表水与地下水联合调度、水资源高效利用探索出了一种新模式. 相似文献
9.
Summary. The magnitude and distribution of ground deformations around a tunnel are often monitored during construction and provide
key information about ground-support interaction and ground behavior. Thus it is important to determine the effects of different
parameters on ground deformations to accurately and effectively evaluate what contributes to ground and support behavior observed
during excavation. This paper investigates one such relation: the effects of seepage on radial deformations. A number of numerical
analyses have been conducted with the following assumptions: deep circular unsupported tunnel, elastic ground, isotropic far
field stresses, dry ground or saturated ground with steady-state water seepage. The analyses cover a wide range of tunnel
sizes, effective stresses, and pore pressures. Results from the numerical simulations confirm previous analytical solutions
for normalized radial deformations behind the face (i.e. on the tunnel side of the face) of a tunnel excavated in dry ground,
and have been used to propose a new analytical formulation for normalized radial displacements ahead and behind the tunnel
face for both dry and saturated ground with water flow. Water seepage substantially increases the magnitude and distribution
of the normalized radial deformations ahead of the face and at the tunnel face, but does not change much the displacement
distribution behind the tunnel face. 相似文献
10.
11.
12.
高土石坝在施工期心墙会产生超静孔隙水压力,且难以有效消散,蓄水后心墙从非稳定渗流状态到稳定渗流状态,因此,渗流特性异常复杂。目前,有限元方法进行渗流计算不能考虑施工期引起的孔隙水压力,因而不能完全了解土石坝的渗流特性。长河坝为砾石土心墙堆石坝,最大坝高为240 m。利用离心模型试验技术,通过分析长河坝施工期和运行期心墙的孔隙水压力的产生和消散变化规律研究大坝心墙的渗流特性。试验结果表明,心墙孔隙水压力经历施工时的增长期、竣工后的消散期、非稳定渗流时的增长期和消散期、稳定渗流时的稳定期5个阶段。心墙高程不同、填筑含水率不同,各阶段的孔隙水压力和历时也不同。心墙位置越高或填筑含水率越大,施工期孔隙水压力系数越大,形成稳定渗流所需时间越短。心墙位置越高或填筑含水率越小,心墙位势越大,非稳定渗流期心墙位势大于稳定渗流期。研究成果对高心墙堆石坝设计和施工具有指导意义。 相似文献
13.
Gregory R. Brooks 《Sedimentology》2003,50(3):441-458
Abstract The Red River, Manitoba, is a mud‐dominated, meandering stream that occupies a shallow valley eroded into a clay plain. The valley‐bottom alluvium is the product of incision and lateral migration of river meanders. As revealed by a transect of five boreholes located across the floodplain at each of two successive river meanders, the alluvial deposits range from about 15 to 22 m thick and are composed primarily of silt. Sedimentary structures in the cores are weakly defined and consist mostly of beds of massive silt, thick (>0·4 m) massive silt and disturbed silt. Interlaminated sand and silt, and sand beds form relatively minor deposits, principally within the lower half of the alluvium, and thin beds of medium‐coarse sand and pea gravel can be present locally within the lower metre of the alluvium. The alluvium is interpreted to consist of overbank deposits from 0 to 2–3 m depth, oblique accretion deposits from 2–3 to 8–12 m depth and oblique accretion and/or channel deposits from 8–12 m to the base of the sequence. The massive bedding within the oblique accretion deposits is interpreted to represent the remnants of couplet deposits that were initially composed of interbedded, muddy silt and sand‐sized silt aggregates, as is consistent with the contemporary bank sedimentation. The post‐depositional disintegration and/or compaction of the aggregates has caused the loss of the sand‐sized texture. The disturbed silt beds are interpreted as slump structures caused by large‐scale rotational failures along the convex banks. Overall, the Red River represents a portion of a continuum of muddy, fine‐grained streams; where the alluvium lacks a distinct coarse unit, oblique accretion deposits form a majority of the floodplain, and large‐scale slump features are present. 相似文献
14.
Artificial ground freezing is an environmentally friendly technique to provide temporary excavation support and groundwater control during tunnel construction under difficult geological and hydrological ground conditions. Evidently, groundwater flow has a considerable influence on the freezing process. Large seepage flow may lead to large freezing times or even may prevent the formation of a closed frozen soil body. For safe and economic design of freezing operations, this paper presents a coupled thermo-hydraulic finite element model for freezing soils integrated within an optimization algorithm using the Ant Colony Optimization (ACO) technique to optimize ground freezing in tunneling by finding the optimal positions of the freeze pipe, considering seepage flow. The simulation model considers solid particles, liquid water and crystal ice as separate phases, and the mixture temperature and liquid pressure as primary field variables. Through two fundamental physical laws and corresponding state equations, the model captures the most relevant couplings between the phase transition associated with latent heat effect, and the liquid transport within the pores. The numerical model is validated by means of laboratory results considering different scenarios for seepage flow. As demonstrated in numerical simulations of ground freezing in tunneling in the presence of seepage flow connected with the ACO optimization algorithm, the optimized arrangement of the freeze pipes may lead to a substantial reduction of the freezing time and of energy costs. 相似文献
15.
山区公路工程建设对地下水渗流的影响 总被引：1，自引：0，他引：1
分别就公路路堤、路堑、半挖半填等路基结构和隧道结构对周围岩土体的渗透性、渗流路径、地下水位等方面的影响进行了分析,以对公路工程建设对地下水环境的影响和与水文地质有关的灾害和损害的分析评价有所帮助。 相似文献
16.
17.
长江中下游地区矿产丰富,不少矿区为冲洪积物所覆盖。基于烃汞气体挥发性、穿透性强以及迁移距离远的特点,文章利用烃汞综合气体测量法针对冲洪积物覆盖的特殊景观区开展了探索性的找矿试验研究。通过对长江中下游地区烃汞背景值和不同矿床类型烃汞异常场的研究,以及典型矿床烃汞测量找矿的有效性试验,结合烃类组分微观结构对比分析等方面的研究,发现长江中下游地区大部分矿床在成矿过程中伴随形成烃类气体原生异常场,同时,地表冲洪积物中含有与深部矿床同源的烃类异常信息,初步显示了烃汞测量法在冲洪积物覆盖区应用于找矿是可行的。 相似文献
18.
Davut Yılmaz Fatih Babuçcu Serhat Batmaz Fatih Kavruk 《Geotechnical and Geological Engineering》2008,26(2):211-224
Beydag dam is under construction on Kucukmenderes River for irrigation purposes. Due to the scarcity of core material and
liquefaction of alluvium at the dam site, the original design was changed to Roller Compacted Concete (RCC) from rockfill
dam with claycore. Although the new design was safer, it nearly doubled the cost of the dam, so the owner, State Hydraulic
Works of Turkey, (DSI) set out to find more economical but equally safe alternative. Since jet-grouting is a cheap ground
improvement tool in Turkey, such an alternative was developed for the ground improvement against liquefaction together with
concrete face rockfill dam sitting on top of improved ground. This paper presents a detailed discussion of how the new alternative
was developed and evaluated: it discusses the determination of jet grouting pattern, the placement of jet grouted blocks,
and the assesment of liquefaction. On one hand the soil cement strength of jetgrout columns, internal friction angle of alluvium
and rockfill were important in determining the dimensions of the blocks, on the other hand the location of the blocks were
highly affected by the areas where liquefaction occurred. One of the most important parameter that has a considerable influence
in delineating the boundary betweeen liquefaction and non-liquefaction was the value of stress reduction coefficient (r
d), being primarily sensitive to the weight of overburden, which is calculated by the height from the face of dam to the depth
where the calculation was made. This approach is justified by two-dimensional ground response analysis. Most importantly,
this paper shows that there exists an alternative solution for building dams on the liquefaction prone sites without removing
alluvium by using a well known jet grouting technique for improving ground at only selected places. 相似文献
19.
G. F. Ufimtsev 《Lithology and Mineral Resources》2008,43(1):76-80
Some rare types of small clinoforms found in the latest continental deposits of lowland platform and mountain regions are described. The clinoforms are represented by prodelta deposits of mountain lakes, oblique-bedded horizons of floodplain alluvium of strongly meandering rivers, thick and short lenses of mountain alluvium, and alluvium horizons of great lowland rivers with oblique bedding grading into horizontal bedding. Such structures bear information on paleogeographic, morphological, and lithodynamic features of continental sedimentation. 相似文献
20.
Assessment and prediction of contaminant migration in ground water from chromite waste dump 总被引：3，自引：0，他引：3
Sukinda chromite valley is one of the largest chromite deposits of the country and produces nearly 8% of chromite ore. It
greatly contributes towards the economic development but at the same time deteriorates the natural environment. It is generally
excavated by opencast mining method. In the Sukinda mining area, around 7.6 million tons of solid waste have been generated
in the form of rejected minerals, overburden material/waste rock and sub-grade ore that may be resulting in environmental
degradation, mainly causing lowering in the water table vis-à-vis deterioration in surface and ground water quality. The study
conducted in and around one of the chromite mine of the valley reveals that the concentration of hexavalent chromium is found
in the water samples of ground and surface water, mine effluents and seepage water. Hexavalent Chromium (Cr+6) have been found varying between 0.02 mg/l and 0.12 mg/l in mine effluents and 0.03–0.8 mg/l in shallow hand pumps and 0.05
and 1.22 mg/l in quarry seepage. The concentration of Cr+6 in Damsal nalah, the main surface water source in the area, is found varying between 0.03 mg/l and 0.14 mg/l and a increasing
trend, which is in the downstream of mining activities, has been observed. Leachate study clearly shows that the soil lying
in the vicinity of mine waste dump shows highest concentration of Cr+6. Contaminant migration in ground water depends upon various geohydrological conditions of the area. The study shows that
aquifer resistivity varies between 15 Ωm to 150 Ωm and aquifer depth varies from 4 m to 26 m below ground level. The ground
water flow and mass transport models were constructed with the help of geo-hydrological and geophysical informations using
Visual Modflow software. Contaminant migration and path lines for 20 years have been predicted in two layers model of ground
water. The study provided an insight into the likely migration of contaminant in ground water due to leaching from overburden
dump of chromite ore and will be helpful in making strategic planning for limiting the contaminant migration in the ground
water regime in and around the mining areas. 相似文献