Comparison of SEEP/W Simulations with Field Observations for Seepage Analysis through an Earthen Dam (Case Study: Hub Dam – Pakistan)
Comparison of SEEP/W Simulations with Field Observations for Seepage Analysis through an Earthen Dam (Case Study: Hub Dam – Pakistan)
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SEEP/W 模拟与土坝渗流分析现场观测的比较（案例研究：枢纽大坝 - 巴基斯坦）
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发表时间：
2014
期刊：
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通讯作者：
M. M. Babar
中科院分区：
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作者：
I. Arshad;M. M. Babar
目前的研究工作旨在利用有限元方法对土坝进行渗流分析建模。为此，我们对 Hub 坝进行了一项研究，Hub 坝是一座小型土坝，位于巴基斯坦卡拉奇市东北部约 35 公里处。在研究中，计算了主坝主体和下方的渗流量，模拟了不同情况下的潜水线剖面，并与观测数据进行了比较。出于本研究的目的，使用了 Geo-Slope 软件的子程序 SEEP/W。与设计参数和大坝几何形状有关的数据作为软件的输入来计算未知参数。最后通过与观察到的数据进行比较来验证结果。主坝由三种不同河段组成；因此，本研究仅研究了一个带核心墙的河段，即 CH：48+75 处的分区路堤断面。计算分为三种不同的场景，即：最大池水位、正常池水位和最小池水位。材料特性的校准是在误差最小化的基础上进行的，同时将观察到的水头与模拟的水头进行比较。绘制的流网由流线、等势线、显示主要流动（渗流）场的速度矢量和描述枢纽坝渗流行为的潜水线组成。计算整个池塘水位场景和所有选定部分的渗流通量（流量）、出口梯度和最大渗流速度。在最低池塘水位时，发生最小渗漏；在最高池塘水位时，发生最大渗漏。还可以确定出口梯度在允许的范围内，即小于所有场景的统一；因此也符合大坝的安全标准。计算整个池塘水位情景和选定部分的渗流速度；在最低池塘水位处观察到最小渗流速度，在最高池塘水位处出现最大渗流速度。针对不同场景的所有感兴趣部分的剩余水头耗散趋势进行建模和预测。在选定的路段，即 CH 处的分区路堤断面：48+75，对于低池塘水位，遵循稍微平滑的消散率，但是，在较高的池塘水位处，板桩位置处会出现稍微快速的水头消散；这当然说明了板桩的有效性。最初，死耗散遵循较为平滑的趋势，但在核心墙和板桩位置，水头耗散表现出突然上升，这再次表明了两种防渗装置的有效性。任何模型的验证都是通过将模拟结果与观察结果进行比较来进行的；这样做是为了确保模型的适用性。如果这种比较显示出良好的一致性，那么所开发的模型可以推荐用于实践。表 4 包含与观察的测压头和模拟的测压头相关的数据以及相对误差。模型的性能根据统计参数进行评估，即平均误差、均方根误差和模型效率；这些结果列于表 6 中。
The present research work is designed to model seepage analysis of an earthen dam by using finite element approach. For this purpose a research study was conducted on Hub dam, which is a small earthen dam located at about 35 km, north-east of Karachi city , Pakistan. In the study the amount of seepage through and under body of the main dam is computed, profile of phreatic line is simulated for different scenarios and compared with the observed data. For the purpose of this study, SEEP/W the sub-program of Geo-Slope software is used. Data pertaining to design parameters and dam geometry are given as input to the software to compute the unknown parameters. Finally results are validated by comparing them with the observed data. The main dam is composed of three different kinds of reaches ; therefore in this research only one reach with core wall i.e. Zoned Embankment Section at CH: 48+75 is studied. Computations are carried out for three different scenarios, that is: maximum pool level, normal pool level, and minimum pool level. Calibration of the material properties is made on the basis of minimization of error while comparing observed hydraulic heads with the simulated ones. The flownet has been drawn comprising of streamlines, equipotential lines, velocity vectors showing dominant flow (seepage) field and phreatic line depicting seepage behavior of the Hub dam. The seepage flux (discharge), exit gradient and maximum seepage velocity for the entire pond level scenarios and for all the selected section are computed. At lowest pond level minimum seepage occurs at highest pond level maximum seepage occurs. It is also ascertained that the exit gradient is within the permissible limits that is that less than unity for all the scenarios; thus it also conforms to safety criteria of the dam. Seepage velocities for the entire pond level scenarios and for the selected section are computed; at lowest pond level minimum seepage velocity is observed and at highest pond level maximum velocity occurs. Residual head dissipation trend is modeled and predicted for all the sections of interest for different scenarios. At selected section i.e. Zoned Embankment Section at CH: 48+75 for low pond level slightly smoother dissipation rate is followed, however, at higher pond levels a somewhat rapid dissipation of head occurs at sheet pile positions; this of course signifies the effectiveness of sheet pile. Initially dead dissipation follows somewhat smoother trend, however at the position of core wall and sheet pile an abrupt rise in dissipation of head is exhibited, which again signifies the effectiveness of the two seepage control devices. Validation of any model is made by comparing simulated results against the observed ones; this is done to ensure model applicability. If this comparison shows a good coincidence, then the model developed can be recommended for practice. Table 4 contains the data pertaining to observed piezometeric heads and simulated ones and the relative error. Performance of the model is assessed evaluated on the basis of statistical parameters, i.e. mean error, root mean square error and model efficiency; these results are presented in Table 6.