基于ABAQUS的立井降水数值模拟

立井降水在立井施工中起着重要的作用,在分析疏干半径大小、抽水井井深对立井周围降水影响,抽水井抽水速度对立井周围渗流场影响,回灌井井圈半径及其井深对渗流场和应力场影响等的基础上,针对某实例立井降水工程运用ABAQUS进行建模分析,给出了抽水井与回灌井的分布和几何参数、抽水速度、降水的时间历程以及地面沉降分布,为工程实施提供了参考。     

承压含水层中抽水井附近非达西流的近似解析解

本文将线性化方法和Laplace变换相结合研究承压含水层中单一抽水井附近的非达西流问题,得到了水位降深在抽水后期和抽水稳定阶段的近似解析解,并对抽水后期近似解析解的适用性进行了讨论.通过Stehfest数值Laplace逆变换得到了任意时刻任意位置水位降深的半解析解,并采用数值解对线性化方法所得到的近似解进行了验证.研究结果表明:在抽水后期,水位降深随着Izbash定律中的两个常数的增大而减小;在抽水后期,水位降深近似为时间的幂函数,在抽水稳定阶段,水位降深可以近似为距离的幂函数;在抽水后期,线性化方法所得到近似解与数值解吻合很好,而在抽水初期线性化方法则存在一定误差,会低估水位降深.     

第二类越流系统中抽水井附近非达西流近似解析解

该文研究了第二类越流系统中抽水井附近非达西流问题,主含水层中的水流假设为非达西流且方向为水平方向,弱透水层中的水流假设为达西流且方向为竖直方向,假设可以采用Izbash定律描述非达西流。利用线性化方法得到了非达西流情况下的近似解析解并给出了相应的计算算例,以及对计算结果进行了分析。研究结果表明:Izbash定律中的n值越大,在整个抽水时期的水位降深越小;Izbash定律中的k值越大在抽水初期水位降深越大,而在抽水后期水位降深越小;弱透水层的渗透系数在抽水初期对主含水层中的水位降深几乎没有影响,而在抽水后期弱透水层的渗透系数越大,水位降深越小。     

阶梯状抽水试验水文地质参数确定

针对传统阶梯状抽水试验参数计算过程中,通常只选择抽水阶段的部分试验数据等问题,应用Theis公式及叠加原理,利用抽水试验所有降深数据(抽水和水位恢复阶段全部资料)求解水文地质参数,利用承压含水层抽水试验数据计算得出导水系数、储水系数,利用潜水含水层抽水试验数据计算得出渗透系数和给水度,此外在低效率抽水井中利用抽水试验数据计算得出井损系数和井流量指数。计算过程中,利用Excel计算并绘制计算水位降深和观测水位降深的拟合曲线,计算过程简单快捷。整个抽水试验过程中,不必再分别提出抽水、水位恢复期的计算公式,可以避免人为选择单个水位降深数据对参数求解带来的影响。     

第一类越流含水层系统中非完整井附近非达西渗流近似解析解

研究了第一类越流含水层系统中非完整井附近非达西渗流问题,得到主含水层抽水井附近水位降深拉氏空间近似解析解及抽水后期近似解析解。抽水井附近主含水层中渗流概化径向渗流和垂向渗流,径向渗流由于流速较大由非达西渗流公式Izbash公式来刻画,垂向渗流由于流速较小用达西定律表示,通过线性化方法简化非达西非线性项,然后结合Laplace变换和有限余弦Fourier变换对水流模型进行求解。结果表明:主含水层中水位降深对称于滤水管中轴线,且在中轴线处最大;在抽水后期,主含水层水位降深随着弱透水层渗透系数的增大而减小,且随着Izbash公式中非达西经验指数n值增大,主含水层得到越流补给的水量减小。     

越流含水层中抽水井附近非达西流动模型的数值解

该文研究了以Forchheimer定律为基础的越流含水层中抽水井附近非达西流问题,获得了该条件下水位降深的数值差分解,分析了非达西流、越流和井储对水位降深的影响.结果表明:在不考虑井储影响时,抽水初期越流补给对水位降深影响较小,不同越流补给情况下的水位降深曲线相互重合;抽水后期,越流补给强度越大,水位降深越小.考虑井储影响后,在抽水初期不同越流补给和非达西流动条件下的水位降深曲线相互重合且在双对数坐标下为一直线,含水层的水位降深规律与不考虑井储情况下一致.非达西流动剧烈程度对水位降深的影响与越流补给强度有关.当越流补给较小时,紊动越剧烈(即非达西流动越明显),抽水初期的水位降深越小,而在抽水后期的水位降深越大;当越流补给较大时,整个抽水过程中紊动越剧烈水位降深越小.     

数值模拟技术在工程降水中的应用研究

在掌握场地水文地质条件和抽水试验成果的基础上,利用Modflow建立了较为合理的渗流数值模型,分析了某工程井点降水中承压含水层水位随时间的下降过程.结果表明:①砂砾石层渗透系数为90 m/d,弹性释水系数为0.002 m-1,计算结果与5口长期观测井的观测数据对比误差较小;②将降水区域扩大为3 000 m×3 000 m,采用第二类边界条件并增加5口降水井进行降水模拟,降深效果非常好.     

受潮浪和径流影响滨海承压层抽水数学模型及其解析解

为研究滨海承压含水层地下水在潮浪、抽水井流扰动及径流和越流补给综合影响下的渗流和水位变化,建立了滨海承压水抽水不稳定流的数学模型,并得到其解析解。通过实例计算和分析可知：潮浪的波动作用与抽水的井流作用将相互影响,潮位升高时承压水水位上升,减缓了抽水引起的水位下降量,而潮位降低时承压水水位下降,将加剧抽水引起的水位下降;越流和径流作用可以减缓承压水水位下降;当承压水径流朝向海洋时,径流作用使水位降“漏斗中心”逆着水流而朝远离海岸线方向移动,并且承压水径流补给对减缓地下水水位下降的作用随时间越来越明显,因此径流作用可以减轻井水受潮浪和海水入侵的影响程度;如井设置在距海岸较远处,潮浪对抽水水位降“漏斗”形状改变不明显;受潮浪和抽水共同作用时的地下水水位-时间曲线围绕仅受抽水作用时的地下水水位-时间曲线上下波动。     

基于改进节点虚流量法的渠道工程施工期渗流场分析

利用求解有自由面渗流的改进节点虚流量法,对大型渠道工程施工期渗流场进行三维有限元模拟,得到不同条件下渠道渗流场的水头分布、浸润线、抽水量以及水力坡降。对施工期不同的降排水方案进行分析和评价,并在控制降水井水位的情况下对各方案进行分析,给出各方案下降水井抽水水位与渠底地下水位和单井抽水量的关系。结果表明,改进节点虚流量法能较好地模拟渠道渗流,可较为准确地判定方案是否满足工程实际要求,为实际工程提供理论和技术支撑。     

基于ADINA的地下水库抽水效应数值模拟

随着经济的发展,地下水库抽水引起的建筑物周围地面沉降和地基沉降问题,已成为重大环境灾害问题之一。本文分析了沉降产生的机理,借助有限元软件ADINA模拟了地下水库抽水对沉降的影响,分别模拟了不同流量的单井抽水对沉降的影响,不同抽水井数(单井、双井、三井)抽水对沉降的影响,以某工程实例进行了模拟,得出以下结论:沉降量与抽水流量、抽水井点数、井点间距等有关。抽水流量越大,孔隙水压力就越大,地下水库沉降量也越大;抽水井点数越多,沉降量也越大,井点间距越大,沉降量越小。     

Alternatives to Reduce Pumping Effects in Glacial Stratified Drift Aquifers During Periods of Low Stream Flow

Low stream flows in the Fenton River, part of a hydrogeological setting characterized by glacial stratified drift, forces the University of Connecticut to frequently reduce groundwater withdrawals during the months of June–October. The objective of this study was to investigate stream/aquifer interactions in such a hydrogeologic system in order to increase water withdrawals while minimizing adverse impacts to in-stream flow. A groundwater flow model was developed using MODFLOW to investigate the influence of well location and pumping timing on in-stream flow in the vicinity of the water supply wells. The numerical model comprised detailed geophysical data and decadal hydrologic data (2000–2009) to assess well placement, rest periods and cyclical pumping. The relocation of a water supply well up to 228 m from the river had a positive but minimal improvement to stream flows (<2.83 L/s). When the well field was shut off for more than 45 days, stream flows returned to the no pumping condition with only slight impact at 30 days, whereas a 30 day rest period gave 4 weeks of dampened pumping influence on stream flows. A management scenario of 1 week cyclical pumping between two water supply wells following a 45 day rest period can allow for current restriction thresholds to be reduced by 28.3 L/s with minimal impact to stream flows (7.36 L/s) and would allow additional water to be pumped for all years in which there was a demand for water.     

基于水动力河网模型的引江泵站规模论证研究

以江苏省南通市引江供水区为例,建立了水动力河网模型,论证了新建泵站的必要性和泵站规模。研究结果表明:仅靠目前五大引水闸自流引江不能满足规划用水的要求;泵站规模越大,抽水量越大,但泵站规模大于180 m~3/s时,内河最低水位的抬高会导致水闸自流引江时间、引水量相应减小,而自引、抽引总水量增加并不明显。从增加供水量、抬高河网水位和影响水闸自流引江量多个方面进行综合考虑和分析,认为新建规模为150 m~3/s的九圩港泵站经济、合理且可行,满足规划用水要求。计算结果较好地反映了滨海感潮河网地区长江潮位、水闸自引、泵站抽引以及河网输水能力与内河水位之间的复杂关系,可为类似区域供水工程的设计提供技术参考。     

Delineating Capture Zone of a Pumping Well in a Slanting Regional Groundwater Flow to a Stream with a Leaky Layer

In this study, analytical and semi-analytical solutions are derived to delineate capture zone of a pumping well near a stream where a leaky layer exists between the aquifer and the stream. A groundwater regional flow is considered in the aquifer and allowed to have different angles with respect to the stream axis. Three critical pumping rates are introduced. At the first pumping rate, capture zone boundary tangents the interface between the aquifer and the leaky layer; called the in-homogeneity boundary. At the second pumping rate, capture zone boundary tangents the stream boundary and if the rate is increased, a part of pumped water would be withdrawn from the stream. The third pumping rate, which may be smaller or larger than the other two, is defined as the rate at which stream water begins to enter the leaky layer; it may or may not be captured by the pumping well. Four different capture zone configurations (cases) are analyzed for different values of pumping rates, groundwater flow directions, and leaky layer’s thickness and hydraulic conductivity. The first three cases analyze hydraulic situations whereby capture zone does not reach the stream, and hence, no pumped water is withdrawn from the stream. With the lowest pumping rate in the first case, no stream water enters the leaky layer. It enters the leaky layer but not the aquifer in the second, and enters the leaky layer and the aquifer in the third case. In the fourth case, where capture zone boundary intersects the stream, the fraction of pumped stream water to total pumped water is delineated.     

黄土潜水含水层深井抽水时水跃值变化特性

水跃值的变化比较复杂,与抽水井深度、半径、井出水量以及抽水持续时间等因素有关,其中井出水量影响最大。本文根据抽水试验资料总结了黄土潜水井水跃值的变化规律并分析了其成因;总结了水位降深随抽水时间的变化关系,并建立了经验公式;提出了公式中参数的确定方法。     

多级串联梯级泵站扬程优化分配研究

为了使梯级泵站群整体以效率最高状态运行,降低输水成本,确定不同工况下梯级泵站群的最优运行调度方案,开展了针对南水北调来水调入密云调蓄工程梯级泵站不同的梯级净扬程组合下的扬程优化分配研究,即当首级泵站进水侧水位和末级泵站出水侧水位(即梯级净扬程)一定时,各级泵站间的扬程分配。在满足各渠段水力联系、各级泵站进、出水侧水位约束等多个条件的前提下,利用动态规划法进行求解,得出各级扬程分配的最优解,使整个梯级输水系统运行效率最高,从而得出梯级泵站系统联合运行扬程优化分配方案。     

含水层抽水试验水位恢复过程数据的直线图解分析法

提出了一种分析含水层抽水试验水位恢复过程数据的新方法。该法对水位恢复阶段降深表达式中的两个井函数分别采取了不同的简化方式。对由于持续抽水引起的降深项，保留了井函数级数展开式中的前两项；对由于在停抽时刻开始的虚拟注水而引起的降深项，保留了展开式中的前三项。在这样的简化方式下，分别推导了具有降深-时间和降深-距离两种数据情况下的参数计算公式。与现有方法相比较，本方法具有使用条件容易得到满足，不需要水泵停抽时刻的降深观测值即可计算含水层的贮水系数，仅利用一个观测孔的资料且进行一次直线图解或线性回归计算，就可进行参数计算等优点。     

石首市取水工程设计

在对湖北省石首市取水泵站取水点处长江河段的基本情况、水文特性、河床演变等分析调研的基础上,经多方案技术经济比较,选择了安全可靠、运行管理方便的固定湿井式取水泵房方案。介绍了取水口、自流管及取水泵站的设计情况。投产2年多来,运行情况良好,效益明显。     

求解黄土含水层水文地质参数的流量-时间配线法

利用基于割离井法的流量-时间配线法反求抽水过程黄土含水层水文地质参数,并与裘布依公式法、割离井公式法的求解结果进行对比。计算结果表明,黄土含水层水文地质参数的求解选用流量-时间配线法求解精度高,可以减少繁琐的计算,结果是可靠的。根据稳定流井流理论,抽水过程观测孔的水位降深值S和观测孔到主井的距离的对数lgr存在一定的关系。利用Dpp软件包的图像处理功能,对实测点据在平面内进行拟合,确定了抽水井影响半径为172 m,确定了抽水过程Q-S、q-S关系曲线方程。     

Managing Saline Water Intrusion in the Lower Indus Basin Aquifer

In view of the declining surface water sources for irrigated agriculture in Pakistan, farmers are compelled to extract groundwater in order provide to security against uncertain canal supplies during critical crop growth periods. However saline water intrusion can be a major hindrance to the sustainable groundwater development. Against this background, a study was conducted with a three dimensional finite element model (FEMGWST) based on the Galerkin weighted residual method being developed to simulate groundwater flow and the saline water intrusion from underlying poor quality aquifer in response to groundwater pumping through low capacity partially penetrated wells. The model was calibrated with field data collected in the district Khairpur of the Lower Indus Basin. The stability of the model for transient groundwater flow and solute transport against different time marching schemes were evaluated. This study showed that the explicit and the Crank-Nicolson time marching schemes developed the numerical oscillating, the global error and the convergence problem. The calibrated model was applied to predict the impacts of different well configurations on the pumped water quality and on the development of saline water mound at the bottom of the well. It was observed that the saline water intrusion into the fresh groundwater layer was directly related to the well discharge, pumping time and inversely to the thickness of fresh-saline water interface and the number of well strainers installed. The model results suggested that intermittent pumping through multi strainer wells could effectively be used to suppress the saline water intrusion. However multi strainers wells were found to induce saline water intrusion when the thickness of fresh-saline water interface was reduced to 4 m.     

Conserving One Water Source at the Expense of Another: The Role of Surface Water Price in Adoption of Wells in a Conjunctive Use System

One potential side-effect of irrigation water rate reform is groundwater substitution. As surface water prices rise, irrigators may find it cheaper to rely on on-farm wells than a regional irrigation district. The impact of surface water price on well adoption is examined in a conjunctive use system where both surface water and groundwater are used to meet irrigator demand. Results indicate that as the price of surface water approaches 62% of the marginal cost of pumping groundwater, irrigators are more likely to have on-farm pumping capabilities. This result suggests that proposed water rate reforms by the United States Bureau of Reclamation may result in irrigators substituting groundwater for surface water by adopting on-farm wells.