共查询到16条相似文献，搜索用时 93 毫秒
1.
通过对一个滨海多层含水层系统的考察,该含水层系统由上、下弱透水层和介于中间的承压含水层组成,海底露头处被淤泥层覆盖.建立了描述该系统中地下水水头随潮汐波动的数学模型,并得到其解析解.该解析解与六个基本参数有关,分别是承压含水层的海潮传播参数,淤泥层的无量纲透水系数,上下弱透层与承压含水层贮水率的比率 (无量纲)和上下弱透层的无量纲越流.当这些参数取某些特殊值时,我们的解便化简为前人考虑的几种简单情形对应的解.分析表明,承压含水层中地下水水头波幅是上、下弱透水层贮水率和越流系数的减函数,是淤泥层相对透水系数的增函数;波动相位(时滞)是上、下弱透水层贮水率和越流系数的增函数,是淤泥层相对透水系数的减函数. 相似文献
2.
滨海地区社会与经济的发展引发了各种各样的水文地质问题, 因此对滨海地区的水文地质条件, 尤其是地下水与海水之间的水力联系的研究尤为重要.本文考察了海底露头处具有淤泥层的滨海含水层系统中由海潮引起的水头波动.该系统由潜水含水层、承压含水层和介于其间的弱透水层构成.建立了该系统的数学模型, 得到了该模型的解析解.该解析解包含2个无量纲参数: 弱透水层的相对越流系数和淤泥层的相对透水系数.解析解表明, 淤泥层使各处的水头波幅被缩小了一个常数倍(波幅缩减因子), 并使各处的波动相位产生了一个不超过45°的正位移常数(时滞).该时滞对半日潮不超过1.5h, 对全日潮不超过3h.波幅缩减因子和正位移常数只与弱透水层的相对越流系数和淤泥层的相对透水系数有关.当这两个无量纲参数取某些特殊值时, 本次研究的解和前人考虑的几种较简单情形所对应的解一致.承压含水层中水头波幅随着淤泥层的相对透水系数的递增而严格递增, 随弱透水层的相对越流系数的递增而严格递减; 波动相位随着这2个无量纲参数的递增均严格递减.分析表明弱透水层的越流和淤泥层的存在均对承压含水层水头波动有显著影响. 相似文献
3.
综合考虑了海底淤泥层的弹性储水系数、海潮荷载效应和渗透性,对海底露头处具有淤泥层的滨海承压含水层系统中海潮引起的水头波动进行分析,给出了相应的数学模型,并推导出其解析解,讨论了淤泥层弹性储水对于水头波动的影响.分析表明,当淤泥层的厚度或弹性储水系数较小时,或者其渗透性较好时,可以忽略其弹性储水效应,从而把整个淤泥层简化为第三类边界条件来处理.文章还考虑了承压含水层和淤泥层中可能存在的垂向流动,对垂向剖面二维地下水流动方程进行了数值模拟,将二维数值解与忽略垂向流动的一维解析解进行了比较,结果表明该含水层系统的垂向流动是可以被忽略的. 相似文献
4.
海潮波动可以引起海岸带有越流的承压含水层地下水头发生波动。建立了基于有限差分法的滨海地区一维承压含水层地下水运动数值模型。通过将潮汐波动概化为正弦波,分别对初始水头水平及线性倾斜的承压含水层模拟了滨海地区有越流的承压含水层地下水头随潮汐波动的变化。通过对两种情形下的变化比较,结果表明,受海潮影响的滨海承压含水层地下水头与海潮有相似的波动特征,但变幅减小,受海潮的影响程度与离海岸的距离有关,随着离海岸距离的增加,地下水头的变幅及潮汐效率呈负指数函数衰减,水头倾斜情形下变幅更小,潮汐效率更小,滞后时间更短,地下水头对海潮的滞后时间随距离呈线性增加。 相似文献
5.
6.
运用三维变密度潮汐效应模型确定滨海含水系统的海底等效边界——山东烟台夹河中下游地区为例 总被引：3，自引：1，他引：3
确定咸淡水界面的位置是滨海地区海水入侵研究的主要任务之一。对于天然条件承压含水层而言，含水层顶板向海底延伸的距离直接影响了咸淡水界面的位置，它可以通过承压含水层中地下水的潮汐效应信息来确定。考虑到咸淡水之间密度的差异，建立了山东省夹河中下游地区滨海含水系统地下水三维变密度潮汐效应模型。通过反复对比潮汐效应观测中的地下水水头波动与模型计算出的水头波动，确定了滨海承压含水系统的海底边界。同时，也初步估计出海区与近海陆区含水层的水文地质参数。 相似文献
7.
工程建设中当距离抽水井r=rb处水位基本没有变化或不受抽水影响时,或当此处存在止水帷幕时,含水层系统视为侧向有限延伸,rb为有限半径。为此,构建更加符合工程实际的侧向有限延伸的典型弱透水层-承压水层系统中非完整井非稳定流计算模型,同时考虑井径和井储效应的影响,应用Laplace变换和分离变量法得到了水位降深在拉氏空间下的解析解,并应用拉氏数值逆变换Stehfest法得到真实空间下的水位降深。新建立的解析解可以进一步退化为诸多已有解,并进一步将其与已知解和有限元数值解进行对比,验证了所得解的正确性和可靠性。基于新建解重点分析了侧向边界和井的完整性对承压水层水位降深的影响。结果表明:含水层系统的侧向有限边界仅对抽水后期的水位降深影响明显,含水层系统侧向无限延伸情况下的水位降深要大于情形1(在r=rb处为定水头边界)且明显小于情形2(在r=rb处为不透水边界)下的水位降深,rb越小,两者之间的误差越大;抽水井的完整性对整个抽水期间不同情形下的水位降深均有明显的影响,承压含水层顶板处的水位降深随着抽水井滤管的长度和埋深的增加而减小。 相似文献
8.
海潮波动可以引起海岸带地下水位发生波动。建立了基于有限差分法的滨海地区一维承压含水层地下水运动数值模型。将潮汐波动概化为正弦波,模拟了滨海地区地下水位随潮汐波动的变化。通过与初始水位水平的承压含水层水位变化的比较表明,受海潮影响的滨海承压含水层地下水位与海潮有相似的波动特征,但变幅减小,受海潮的影响程度与离海岸的距离有关,随着离海岸距离的增加,地下水位的变幅及潮汐效率呈负指数函数衰减,但比前者变化程度稍缓,地下水位对海潮的滞后时间随距离呈线性增加。 相似文献
9.
传统承压含水层井流理论都假定承压水层顶面总应力不变，其隐含的意义是忽略含水层顶板的刚度，从而忽略了顶板弯曲对含水层释水的影响。指出考虑顶板弯曲时，抽水井周围承压含水层顶部的总应力将减小，从而产生比传统理论估计更大的地下水降深，并结合弹性板理论对Theis井流模型作出了改进，新模型的解析解证明Theis模型计算的地下水龙头降深偏低。 相似文献
10.
通过潮汐效应确定延伸到海底的承压含水层顶板长度 总被引：2，自引：0，他引：2
李国敏 《水文地质工程地质》1988,(4)
延伸到海底的承压含水层顶板长度是影响海水入侵淡含水层的重要条件之一。陆地区承压水头的潮汐动态提供了有关顶板长度的信息。本文在Jocob和Van der Kamp等人的工作基础上,建立了滨海地区承压水头天然潮汐动态的数学模型,从地下水流的连续性原理出发,求出承压水头动态的一般公式,并以此公式为理论依据,首次提出直接和用承压水头的天然潮汐动态确定延伸到海底的承压含水层顶板长度,文中给出了该方法的应用实例。 相似文献
11.
Xun Zhou 《Environmental Earth Sciences》2014,71(3):1311-1317
In a coastal zone an understanding of the distance of the fresh water–salt water interface and its extension inland is important for prevention of sea water intrusion. In this article estimating methods are described for calculating the distance of a fresh water–salt water interface in a coastal confined aquifer based on the submarine fresh groundwater discharge. This groundwater discharge is controlled not only by the aquifer properties and hydraulic head difference, but also by the position of the fresh water–salt water interface in the coastal zone. A homogeneous and isotropic coastal confined aquifer is considered and fresh groundwater flow in the confined aquifer is thought to be at a steady state. Two observation wells at different distances in a profile perpendicular to the coastline are required in calculation of the distance of the interface toe in the coastal zone. Four coastal confined aquifers with horizontal and sloping confining beds and with varying thickness are also considered. Reasonable results are obtained when examples are used to illustrate the application of the methods. The methods require hydraulic head data at the two wells and thickness of the confined aquifers, but the hydraulic conductivity and fresh groundwater flow rate of the confined aquifers are not needed. 相似文献
12.
Tide-induced head fluctuations in a coastal aquifer: effects of the elastic storage and leakage of the submarine outlet-capping 总被引：1，自引：1，他引：0
This paper considers the tidal head fluctuations in a single coastal confined aquifer which extends under the sea for a certain distance. Its submarine outlet is covered by a silt-layer with properties dissimilar to the aquifer. Recently, Li et al. (2007) gave an analytical solution for such a system which neglected the effect of the elastic storage (specific storage) of the outlet-capping. This article presents an analytical solution which generalizes their work by incorporating the elastic storage of the outlet-capping. It is found that if the outlet-capping is thick enough in the horizontal direction, its elastic storage has a significant enhancing effect on the tidal head fluctuation. Ignoring this elastic storage will lead to significant errors in predicting the relationship of the head fluctuation and the aquifer hydrogeological properties. Quantitative analysis shows the effect of the elastic storage of the outlet-capping on the groundwater head fluctuation. Quantitative conditions are given under which the effect of this elastic storage on the aquifer’s tide-induced head fluctuation is negligible. Li, H.L., Li, G.Y., Chen, J.M., Boufadel, M.C. (2007) Tide-induced head fluctuations in a confined aquifer with sediment covering its outlet at the sea floor. [Fluctuations du niveau piézométrique induites par la marée dans un aquifère captif à décharge sous-marine.] Water Resour. Res 43, doi:10.1029/2005WR004724 相似文献
13.
Concurrent bulk ground conductivity mapping and direct measurements of seepage rates were carried out near a pier at Shelter
Island, New York, U.S.A. A shallow sediment layer was identified to provide confinement for lower aquifer units. The conductivity
and seepage rate data indicate that pilings of the pier apparently pierce this shallow sediment layer, producing a comparatively
high seepage rate driven by the hydraulic head of the (partially) confined aquifer, resulting in a substantial increase in
submarine groundwater discharge (SGD) near the pier. Seepage rate measurements made close to the pier, which runs perpendicular
to the shoreline, cannot be considered representative for the area. At the study site, the magnitude of SGD depends both on
the distance from shore and on the distance from the pier, a rmding that confounds the commonly observed patterns of decreasing
SGD with increasing distance from shore. This alteration of a groundwater flow pattern is a previously undescribed effect
of anthropogenic perturbation in a coastal system. 相似文献
14.
某深大基坑位于长江下游岸边,场地地层为典型的二元结构,基坑开挖涉及的两层承压含水层间的弱透水层局部缺失,之间水力联系密切,基坑场地地质条件极为复杂,基坑施工降水直接关系到基坑工程的安全。这里将基坑分3个区,分别进行降水设计。具体降水方案:Ⅰ区两层承压含水层和Ⅱ区第一承压含水层被围护结构隔断内外水力联系,采用疏干井降水;Ⅱ区第二承压含水层未被围护结构隔断,Ⅲ区两层承压含水层水力联系密切,针对这两个区域设计了两套降水方案,方案一在Ⅱ区和Ⅲ区均布置有降水井,在Ⅱ区对第二承压含水层降水,在Ⅲ区对第一承压含水层降水;方案二仅在Ⅲ区布置降水井对第一承压含水层降水。为了更好地对降水方案进行对比分析,验证方案的可行性,对此进行了数值模拟分析,计算结果显示,两种方案均能满足降水要求,不过方案二布井数量少,基坑外水位降深较小,对周边环境影响更小,优于方案一。 相似文献
15.
H. Carey M. K. Lenkopane A. D. Werner L. Li D. A. Lockington 《Australian Journal of Earth Sciences》2013,60(8):1165-1179
Previous studies of coastal groundwater resources have not properly explored the hydraulic conditions at coastal and estuarine boundaries, despite recognised influences of oceanic and estuarine water-level fluctuations (e.g. tides and waves) on groundwater near these boundaries. Such influences may have important implications for determining submarine groundwater discharge and seawater intrusion. In this paper, oceanic and estuarine controls on the hydrology of coastal aquifers are characterised for a macrotidal system—the Pioneer Valley coastal plain, northeastern Australia. The tidal water-table over-height (tide-induced increase in average water-table height at the coastline) is quantified at three locations and compared with theoretical estimates, which assume simplified physiographical conditions compared with those encountered at the field sites. The results indicate that local geological conditions, beach morphology and characteristics of tidal forcing control the behaviour of nearshore groundwater within the system. Existing analytical and numerical solutions that are commonly applied as first-pass estimates are found to be insufficient for predicting observed tidal water-table over-height in the Pioneer Valley, due to the sediment heterogeneities, non-uniform beach slopes and large tidal ranges of the system. The study reveals the spatial and temporal variability in tidally influenced hydraulic heads at the estuarine and coastal boundaries of the aquifer, and provides estimates of tidal water-table over-height up to 2.41 m during spring tides. These findings highlight the complexity of coastal groundwater systems, and the need to incorporate appropriate nearshore and near-estuary boundary conditions in models of regional groundwater flow in coastal aquifers. 相似文献
16.
A new analytical solution is developed for describing groundwater level fluctuations in a coupled leaky confined aquifer system
which consists of an unconfined aquifer, confined aquifer, and an aquitard in between. The aquifer system has a tidal boundary
at the seashore, a no flow boundary at remote inland side, and a confined aquifer extending under the sea and terminated with
an outlet-capping. This new solution has shown to be a generalisation of most existing analytical solutions for a tidal aquifer
system which includes single confined and leaky confined aquifers. In addition, the solution is used to explore the influences
of the dimensionless leakance of the outlet-capping, the dimensionless hydraulic diffusivities, and the leakages of the inland
and offshore aquitards on the head responses in the leaky confined aquifer. 相似文献