共查询到18条相似文献，搜索用时 109 毫秒
1.
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
2.
水资源和环境工程中水平井研究简介 总被引：1，自引：0，他引：1
简单介绍了水平井在水资源和环境工程中的近期研究进展, 重点介绍了在不同含水层(如承压含水层、潜水含水层、越流含水层及河下含水层) 中, 水平井抽水条件下降深的半解析解, 同时分析了降深随抽水时间变化的标准曲线和微分标准曲线.这些半解析解可用于分析小流量水平井在中长时段的降深特性.分析了用于排水和供水的大流量水平井的水力学特征, 并介绍了求解渗流-管流耦合井流系统的一种新方法.同时介绍了在非饱和含水层中水平井抽取气体的动力学特征, 并分析了地面覆盖和未覆盖2种情况下的气体清除效率, 报告了在不同饱和含水层条件下水平井的捕获区和捕获时间的计算. 相似文献
3.
刘毅 《水文地质工程地质》1991,(2)
实际抽水试验暴露出了环状承压含水层的特点,本文依据作者1987年提出的扇环承压含水层扇顶井流模型,以及1988年提如的非均质效应假定,通过数学推导得出了在不同抽水阶段的降深解析式,又通过数值模拟归纳出了其三种s_1——lgt过渡曲线类型,最后以此s_1——lgt曲线特点及非均质效应临界降深(s_c),建立了环状非均质含水层的s_1——lgt求参方法,并应用它较好地解决了海泉含水层的实际求参问题。 相似文献
4.
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
5.
(一) 模拟承压含水层抽水试验的基本原理 应用电网络模拟抽水试验反求水文地质参数,与解析解一样是针对轴对称(井)问题,以二维流偏微分方程的极座标形式为基础,然后依据该方程与电流方程的相似性进行模拟试验。 1.基本方程的变换和差分方程 如图(1) 设ρ=1gγ,则承压含水层二维渗流偏 相似文献
6.
《岩土力学》2021,(3)
采用悬挂式止水帷幕结合坑内减压降水的墙-井系统可有效减小坑内降水量或坑外水头降深。将基坑按面积相等等效为井壁进水的大直径承压水非完整井,幵令流入井内的水量等于止水帷幕内坑底承压水含水层内的竖直向渗流量,以此建立坑内减压抽水量与坑外承压水头降深的关系式。该理论公式计算结果在止水帷幕插入比大于0.6且基坑半径与承压含水层厚度之比小于2.0时与有限元计算结果比较接近。因未考虑渗流方向变化时的水头损失,数值计算结果和工程案例实测数据均表明理论公式计算结果偏大。利用参数分析研究承压含水层渗透系数各向异性、基坑平面面积、止水帷幕插入长度等因素对减压降水的影响规律。坑内减压抽水量或坑外水头降深与墙-井系统三维渗流场有关,渗流场越接近竖向渗流,坑外水头降深越小,水位接近初始状态。相比数值分析,理论公式简便直观,可用于减压降水的初步分析。 相似文献
7.
建立了具有代表性的双层含水层抽水概念模型,基于等效渗透系数法建立了井筒—含水层耦合数值模拟模型,利用该模型模拟了双层抽水试验中观测井井筒及周边水头降深的分布、观测井内部水流的垂向分布、含水层与观测井的补给关系。分析了井筒效应的发生机理及观测井井筒内径和径距对井筒效应的影响规律,得出以下主要结论:在双层含水层中利用不完整井抽水时,同一水平位置不同高度处的水头降深不一样,由此导致的垂直方向的水头差会导致观测井内产生垂向水流,水流的流量受观测井井径和径距影响,井径越大流量越大,径距越大流量越小;观测井中的垂向流量会导致井筒周边含水层水头的重分布,此即井筒效应。距离观测井越近,受井筒效应影响越大。同时井筒效应的影响程度和影响范围受观测井井径和径距决定,井径越大影响程度和范围越大,径距越大影响程度和范围越小。 相似文献
8.
汤邦义 《水文地质工程地质》1988,(4)
单井稳定抽水试验是水文地质勘察中取得含水层参数的重要手段之一。依照裘布依水井理论,承压井的降深与流量成正比。但是,在水井动力场中,由于径向流速的不断增大,过滤器的阻力以及三维流等作用,使两者之间往往呈非线性关系,形成不同的涌水量曲线类型,即产生所谓井损。因此,利用单井抽水资料计算含水层参数,首先必须消除井损。单井抽水的井损消除,目前一般采用抛物线方程 相似文献
9.
抽水井附近由于流速过快往往发生非达西流,而远离抽水井随着流速下降又变为达西流.为了描述这些特征,建立了承压含水层中非完整井附近“非达西-达西”两区渗流模型,即距离抽水井较近的区域由于流速较快假设发生非达西渗流,并利用Izbash公式刻画,而距离抽水井较远由于流速较慢假设仍然满足达西定律,含水层中垂向流速较小也利用达西定律描述.通过线性化近似方法结合Laplace变换和有限Fourier余弦变换对模型进行了求解,分析探讨了该两区模型下水位降深曲线特征.结果表明:抽水初期,非达西渗流区域水位降深与全非达西渗流模型结果吻合,而抽水后期两区模型非达西渗流区域的水位降深与全达西模型水位降深基本一致,但大于全非达西渗流模型的水位降深;抽水初期,两区模型中达西渗流区域的水位降深比全达西渗流模型结果大,但比全非达西渗流模型结果小;对不同时间的水位降深随井距变化曲线分析发现非达西渗流区域水位降深随Izbash公式中的幂指数n增大而减小,而在达西渗流区域水位降深基本不受n值的影响.研究成果对非完整井抽水试验参数反演具有重要理论意义. 相似文献
10.
根据流体运动的能量变化计算单井稳定流抽水涌水量 总被引：1，自引：0，他引：1
赵文玉 《水文地质工程地质》1991,18(1):58-58
在抽水过程中,如果已知某一降深地下水通过井壁周围岩层的孔隙和裂隙流入井内的速度V、过水断面W,可以求出这一降深的涌水量Q=WV。就如图1所示承压井而言,此承压井含水层厚度为M,井半径为v,水位降深为S,抽水前的稳定水位距含水层底板的距离为H_1,抽水后井内的水位距含水层的底板的距离为H_2,设含水断面的有效孔隙率为n_e(即多孔介质 相似文献
11.
Analytical solutions for constant-rate test in bounded confined aquifers with non-Darcian effect 
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下载免费PDF全文 Yi-jie Zong Li-hua Chen Jian-jun Liu Yue-hui Liu Yong-xin Xu Fu-wan Gan Liang Xiao 《地下水科学与工程》2022,10(4):311-321
This paper proposes a simplified analytical solution considering non-Darcian and wellbore storage effect to investigate the pumping flow in a confined aquifer with barrier and recharge boundaries. The mathematical modelling for the pumping-induced flow in aquifers with different boundaries is developed by employing image-well theory with the superposition principle, of which the non-Darcian effect is characterized by Izbash’s equation. The solutions are derived by Boltzmann and dimensionless transformations. Then, the non-Darcian effect and wellbore storage are especially investigated according to the proposed solution. The results show that the aquifer boundaries have non-negligible effects on pumping, and ignoring the wellbore storage can lead to an over-estimation of the drawdown in the first 10 minutes of pumping. The higher the degree of non-Darcian, the smaller the drawdown. 相似文献
12.
用水位恢复数据反演越流承压含水层参数 总被引：1，自引：0，他引：1
水文地质勘测中,由于水位恢复阶段没有人力和机械因素干扰,由测量数据可以画出平滑的曲线,更适宜于分析水文地质参数,但经典非稳定流Theis公式和Theis水位恢复法所依据的若干假设条件在实际中难以满足。针对越流承压含水层具有补给条件而很快稳定以及非稳定抽水阶段流量常“抖动”的特点,论证了利用稳定流量和Hantush-Jacob越流模型计算的可行性,并用扩展的卡尔曼滤波器反演水文地质参数,经文献中历史数据和实地抽水试验检验结果表明,由该方法反演的预测值和实测值吻合良好。 相似文献
13.
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
14.
The effects of simplifying hydraulic property layering within an unconfined aquifer and the underlying confining unit were assessed. The hydraulic properties of lithologic units within the unconfined aquifer and confining unit were computed by analyzing the aquifer-test data using radial, axisymmetric two-dimensional (2D) flow. Time-varying recharge to the unconfined aquifer and pumping from the confined Upper Floridan aquifer (USA) were simulated using 3D flow. Conceptual flow models were developed by gradually reducing the number of lithologic units in the unconfined aquifer and confining unit by calculating composite hydraulic properties for the simplified lithologic units. Composite hydraulic properties were calculated using either thickness-weighted averages or inverse modeling using regression-based parameter estimation. No significant residuals were simulated when all lithologic units comprising the unconfined aquifer were simulated as one layer. The largest residuals occurred when the unconfined aquifer and confining unit were aggregated into a single layer (quasi-3D), with residuals over 100% for the leakage rates to the confined aquifer and the heads in the confining unit. Residuals increased with contrasts in vertical hydraulic conductivity between the unconfined aquifer and confining unit. Residuals increased when the constant-head boundary at the bottom of the Upper Floridan aquifer was replaced with a no-flow boundary. 相似文献
15.
The Thiem equation of radial groundwater flow to a well is more than 100 years old and is still commonly used. Here, deviations caused by some of its simplifications are quantified by comparing the analytical to a numerical model that allows the implementation of more complex geometries. The assumption of horizontal flow in the Thiem equation, which necessitates uniform inflow over the entire screen length of the fully penetrating well, was found to cause deviations from actual pumping wells where the pump is placed above the screen, resulting in non-uniform inflow and additional drawdown. The same applies to partially penetrating wells, where inflow peaks and additional drawdown occur, especially when the well is screened in the lower part of the aquifer. The use of the Thiem equation in the near-field of a well should thus be restricted to situations where the screen inflow is relatively uniformly distributed, e.g. when it covers large portions of the aquifer thickness. The presence of a gravel pack and a background gradient, on the other hand, are of limited importance. 相似文献
16.
Effects of horizontal strain in estimating specific storage and compaction in confined and leaky aquifer systems 总被引：6，自引：1，他引：5
T. J. Burbey 《Hydrogeology Journal》1999,7(6):521-532
Mathematical and numerical distinctions are made between developments of governing equations involving groundwater flow and
granular displacement where (1) only vertical strain and no change in total normal load are assumed, and (2) such limitations
are eliminated. The former is referred to here as the Jacob-Terzaghi method; the latter is referred to as the Biot method.
Numerical comparisons of drawdown, compaction, and strain are made for hypothetical confined and leaky aquifer systems for
one- and three-dimensional strain problems. Simulation results indicate that incorporation of horizontal strain results in
reduced drawdowns. Vertical compaction for a specified stress distribution is greatly reduced when horizontal strain is invoked.
The distribution of strain components indicates that approximately two-thirds of the total volume strain originates from horizontal
compaction in pumped aquifers. Incorporation of horizontal strain also affects the distribution of flux through the overlying
confining layer as a function of distance from the pumping well and may ultimately affect the interpretation of aquifer-test
data.
Received, January 1999 / Revised, May 1999, August 1999 / Accepted, August 1999 相似文献
17.
Estimating aquifer hydraulic properties using sinusoidal pumping at the Savannah River site,South Carolina,USA 总被引：1，自引：0，他引：1
A framework for estimating aquifer hydraulic properties using sinusoidal pumping is presented that (1) derives analytical solutions for confined, leaky, and partially penetrating conditions; (2) compares the analytical solutions with a finite element model; (3) establishes a field protocol for conducting sinusoidal aquifer tests; and (4) estimates aquifer parameters using the analytical solutions. The procedure is demonstrated in one surficial and two confined aquifers containing potentially contaminated water in coastal plain sediments at the Savannah River site, a federal nuclear facility. The analytical solutions compare favorably with finite-element solutions, except immediately adjacent to the pumping well where the assumption of zero borehole radius is not valid. Estimated aquifer properties are consistent with previous studies for the two confined aquifers, but are inconsistent for the surficial aquifer; conventional tests yielded estimates of the specific yield—consistent with an unconfined response—while the shorter-duration sinusoidal perturbations yielded estimates of the storativity—consistent with a confined, elastic response. The approach minimizes investigation-derived wastes, a significant concern where contaminated fluids must be disposed of in an environmentally acceptable manner. An additional advantage is the ability to introduce a signal different from background perturbations, thus easing detection. 相似文献
18.
Non-Darcian flow to a well in a leaky aquifer was investigated using a finite difference method. Flow in the leaky aquifer is assumed to be non-Darcian and horizontal, while flow in the aquitard is assumed to be Darcian and vertical. The Forchheimer equation was employed to describe the non-Darcian flow in the aquifer. The finite difference solution was compared with the solution of Birpinar and Sen (2004). The latter overestimates the drawdown at early times and underestimates the drawdown at late times; also, the impact of β D on the drawdown depends on the value of B D, where β D is a dimensionless turbulent factor in the Forchheimer equation and B D is the dimensionless leakage parameter. The impact of leakage on drawdown is similar to that of Darcian flow. A sensitivity analysis indicated that the drawdown is very sensitive to the change in the dimensionless well radius r cD when B D is relatively large, while it is sensitive to the change in B D when B D is relatively small. The numerical solution has been applied to analyze the pumping test data in Chaj-Doab area of Pakistan. Birpinar ME, Sen Z (2004) Forchheimer groundwater flow law type curves for leaky aquifers. J Hydrol Eng 9(1):51??9 相似文献