绕坝渗流地下水位的时空分布模型研究

许多大坝的失事是由于高地下水位引起坝肩失稳所致。绕坝渗流是影响坝肩高地下水位的主要因素。为此通常将大坝基础防渗帷幕延伸到坝肩岸坡内一定距离,以减小绕坝渗流影响。而防渗帷幕运行性态随时间变化,为了评价坝肩防渗帷幕和地下水位的运行性态,首先分析了地下水位观测资料和水位、降水、温度、时效等时空影响因素及其表达式,随后基于岸坡地下水位观测资料,利用最小二乘法建立了大坝岸坡地下水位的时空分布模型。通过比较模型剩余标准差和测点的剩余标准差,可以确定坝肩地下水位的异常测点,分析岸坡防渗薄弱部位,掌握坝肩岸坡渗流场时空分布规律,监控绕坝渗流的性态。     

大坝渗流基流的分析模型研究

深入研究了库水位等变化对渗流变化滞后效应,探讨了渗流的滞后模型,利用该模型进行优化分析,确定了渗流滞后天数和影响天数以及上游有效水深等参数;并借助于上游有效水深,将非稳定渗流计算问题转化为稳定渗流的求解问题,简化了计算;在此基础上,结合实测资料及渗流分析,建立了大坝渗流基流的分析模型。算例表明：建立的模型能较好地反映基流的变化性态。     

地下水渗流场对库区滑坡稳定性影响的数值模拟——以白马库区羊角滩滑坡为例

针对库水位变化条件下滑坡的稳定性定量评价复杂问题,考虑降雨和库水位变化对地下水渗流场变化规律的影响机制,采用饱和-非饱和渗流的基本理论,运用渗流模拟有限元法,对重庆市武隆区羊角滩滑坡在6种不同工况下的库区滑坡的稳定性开展了模拟研究。结果表明: ①降雨工况下,降雨对地下水渗流场都有影响,滑坡中部位置受地下水位影响最大,前后部影响小,降雨条件下,滑坡稳定性随着降雨历时的增加而变小,到达一定阶段后,滑坡已经滑动,滑坡稳定性系数不再变化; ②库水位工况下,主要影响滑坡前缘,地下水位是随库水位变化而迅速变化的,随着库水位的上涨,滑坡稳定性系数呈现先减小后增大的趋势; ③地下水位的骤升对浮托作用影响有限,对压坡作用影响较大,同时降低了渗流力的影响,对滑坡稳定起到了积极作用,地下水位的骤降增大了渗流力,减弱了前缘库水位的压坡作用,滑坡失稳的可能性最大。可为库区该类滑坡的稳定性现状及发展趋势预判提供科学依据。     

基于人工神经网络的钻压优化模型的建模方法

提出卫种新的钻压优化模型建模方法－－神经网络法,它可以克服传统方法需要建立数学模型的缺陷,满足自动送钻对实时性的要求。给出了利用反向传播神经网络（ＢＰ网络）建立钻压优化模型的方法,计算机仿真研究表明：利用这种新方法建立的模型不但能够满足自动送钻实时优化钻压的要求,而且也可以用于离线的钻压参数优选。     

地下水渗流与地面沉降耦合模拟

为了准确模拟由地下水开采导致渗流场和应力场发生变化而引起的地面沉降问题,根据Terzaghi有效应力原理,建立了地下水三维渗流与一维垂向固结的地下水渗流与地面沉降耦合数值模拟模型和以比奥固结理论为基础,并结合土体非线性流变理论,将土体本构关系推广到粘弹塑性,同时考虑土体力学参数及水力参数的动态变化关系的地下水渗流与地面沉降三维全耦合数值模拟模型.通过对比分析,结果表明:基于Terzaghi有效应力原理建立的地下水三维渗流与一维垂向固结地下水渗流与地面沉降耦合数值模拟模型模拟所得地面沉降与地下水位呈现出同步变化的趋势,并且当地下水位逐步回升至初始水位时,地面沉降也逐步回升到初始的零沉降状态.而以比奥固结为基础建立的地下水渗流与地面沉降三维全耦合数值模拟模型模拟所得的地面沉降变化趋势滞后于地下水位的变化趋势,并且当地下水位逐步回升至初始水位时,地面沉降虽也逐步得到回升,但回不到初始的零沉降状态,存在一个永久的残余沉降量.在土体参数变化方面,土体的孔隙度、渗透系数及泊松比均呈现先减小后增大的变化趋势,而弹性模量则呈现先增大后减小的变化趋势,与地面沉降的变化相对应.      

基于FEFLOW的地下水热源渗流温度研究

为研究地下水"热"源对于渗流场的影响,选取某水库水源地辐射取水区及部分扩张区为研究范围,使用地下水通用软件FEFLOW对单一地下水热源作用下的Y型河道的渗流场和温度场进行研究,得出地下水热源对渗流场和温度场的影响规律,结果显示:地下水位受水源的影响,在不同位置水位不同,含水层内随着到水源点距离的增加,水位逐渐降低,到达某个位置时会保持稳定不变;靠近地表的地下水温会随着到水源点距离的增加逐渐降低,在垂向上,含水层内地下水温随着高程的降低逐渐降低,而在库水区,受库水的影响垂向水温变化规律则刚好相反,研究结论可为实际工程提供理论指导。     

Seepage problems in the right abutment of the Shahid Abbaspour dam, southern Iran

In this study, seepage phenomena through the right abutment of Shahid Abbaspour dam are investigated. The Shahid Abbaspour dam is a 200 m high arch dam, which regulates the waters of the Karun River, serves power generation, and flood control and irrigation needs. The dam site lies in the Zagros Mountains of southern Iran. This region presents continuous series of mainly of karstic limestone, marl, shale and gypsum ranging in age from Jurassic to Pliocene. The region has subsequently been folded and faulted. Seepage from the Shahid Abbaspour reservoir occurs mainly through the karstic limestone.The basic foundation treatment of the dam consisted of consolidation grouting, a high-pressure grout curtain and a drainage curtain. Moreover, a 144 m high and 30 m wide concrete cutoff wall was built to prevent reservoir seepage through a clay-filled fracture zone in the right abutment. The grout curtain penetrates the “Principal Vuggy Zone” only beneath the central portion of the dam and below the cutoff wall. In the right abutment fan curtains were constructed to reduce drainage flows, but the seepage problem could not be solved. In order to determine the seepage direction and karstification pattern, hydrogeological studies have been carried out. Additional investigation boreholes have been drilled to monitor fluctuations in groundwater level. Besides these, water chemistry, dye tracer, pinhole and XRF tests have been carried out. As a result of these studies, seepage paths have been identified in the karstic limestone in the right abutment of the dam.     

Groundwater level and chemistry changes resulting from tunnel construction near Matsumoto City, Japan

 Before tunnel construction began, the groundwater chemical compositions and levels around the tunnel were studied to determine if water compositions could predict whether surface water will be influenced by tunnel construction. When the chemical composition of the well and springwater was similar to that of the tunnel seepage water, and the altitude of the well and spring was above the tunnel level, the groundwater level in the well and spring was influenced by draining tunnel seepage water. Therefore, comparing the chemical compositions of surface water and groundwater may be used for predictive purposes. However, the results of this study showed there was no noticeable chemical composition change in springwater prior to changes in groundwater level at a particular site. The changes in the hydrology of the plateau caused by tunnel construction were also studied, using measurements of the changes in groundwater chemistry as well as changes in groundwater levels. Prior to tunnel construction, river discharge was greater. Following tunnel construction, some river discharge decreased because springwater was drained as tunnel seepage water and the spring in the catchment dried up. Tritium concentration indicated that 3 years after tunnel construction, surface water did not reach tunnel levels in spite of groundwater level lowering and remaining unconfined groundwater being drained. Received: 17 January 1996 · Accepted: 10 July 1996     

某水利枢纽厂房大型基坑开挖渗流研究

渗流,特别涉及到自由面或浸润线的确定是岩土工程的重点和难点问题。借鉴砂土坝的渗流分析方法,采用经典分段组合法理论得到基坑开挖边坡渗流简化模型Ⅰ。在此基础上将土层分层,应用土层分界面上的渗流折射定律,得到简化模型Ⅱ。分别求解两种模型得到正常水位和最大水位条件下的渗水量,与工程实际的渗水量进行对比发现,计算渗水量大于实际渗水量,这是由于忽略了围堰对渗水的阻隔作用。在正常水位条件下,模型Ⅱ的结果优于模型Ⅰ。     

碳酸盐岩区大型水库蓄水后地下水渗流场特征及岩溶演化趋势

碳酸盐岩区大型水库蓄水引起的地下水渗流场及岩溶环境变化的研究,既是一个工程实际问题,同时也是岩溶环境学的理论问题．以高坝洲和隔河岩水库为例,运用数值模拟方法模拟了水库蓄水前后地下水渗流场的平面和剖面流网特征以及地下水渗透流速的空间变化规律．在此基础上,应用扩散边界层（ Ｄ Ｂ Ｌ） 理论模型分析了研究区不同部位的岩溶环境演化趋势．结果表明,由于库水位的大幅度抬升和防渗帷幕的实施,使得研究区防渗帷幕上游岩溶作用的强度减弱;而防渗帷幕下游岩溶作用的强度加强,并发生方解石的沉积作用．这一现象在隔河岩水库蓄水后已经被验证     

Impact of impoundment on groundwater seepage in the Three Gorges Dam in China based on CFCs and stable isotopes

It is a common concern that the groundwater flow field caused by the Three Gorges Dam changes the regional seismic activity and environment. The changes in the seepage region could be effectively reflected through the analysis of the groundwater age using chlorofluorocarbons (CFC)-based techniques. In this study, the influences of the reservoir water on groundwater and the seepage region boundary of the reservoir were investigated using CFCs, stable isotopes, and water level in groundwater, reservoir water, and spring water during the water storage process of the Three Gorges Reservoir. The results show that the water supplied by the groundwater is older, whereas the water supplied by the reservoir and the springs is younger. With an increase in the water level of the reservoir, the water in well W3, which is located at the vice dam of the head region, becomes older due to the reservoir loading effect, whereas the water in well W4 become younger due to the lateral seepage of reservoir water. This finding indicates that the groundwater seepage regions in wells W3 and W4, which are located at upstream of the reservoir, are all influenced by the Three Gorges Reservoir. In contrast, the sampling points in the northern section of the Xiannvshan fault zone, which is farther from the dam, did not exhibit any direct hydraulic connection between the groundwater and the reservoir water; thus, the reservoir seepage effects may not affect the northern part of the Xiannvshan fault zone. These research results provide important reference data that can be used to analyze the effects of the Three Gorges reservoir storage on the regional environment.     

Electrical and electromagnetic surveys to locate possible causes of water seepage to ground surface at a quarry open pit near Helwan city,Egypt

Water seepage to ground surface at a limestone quarry located at Wadi Garawy about 20 km south-east of Helwan city in Egypt posed a real threat to the mining activity at the quarry. The quarry area is known to be very dry for decades and away from water utilities and infrastructures that may cause water leaks to the quarry. Geophysical investigation including 1D Vertical Electrical Sounding (VES), 2D Electrical Resistivity Tomography (ERT) and 1D Transient Electromagnetic (TEM) surveys were conducted to characterize the rock sequence and locate what could be a possible source of water seepage to the quarry. The resistivity profiles generated from the VES and TEM surveys mapped the rock units in the area down to depths exceeded 100 m. The ERT profiles acquired from the quarrying zone close to the water seepage spot have imaged the top of groundwater level at few meters below the ground surface at the quarry open pit. The spot of groundwater seepage seemed to occur at an area of limestone dissolution that were filled by finer sediments. The finer sediments acted as a hydrological conduit that allowed an upward seepage of groundwater to ground surface under the capillary action effect.     

龙凤山水库土石坝渗流混水现象研究

龙凤山土石坝在运行的很长一段时期内,坝后排水沟出现严重的混水现象,该现象白天呈周期性变化。利用原子吸收法和X-荧光光谱分析法,对坝后排水沟中的水及析出物进行化学成分分析,研究坝基析出物化学成分的演变规律。研究表明,水质中富含Ca,析出物中富含Fe和Mn。在坝基地下水渗流过程中,地下水与坝基岩石产生物理化学作用,从而导致化学潜蚀。地下渗流水的化学潜蚀作用与坝基岩石性质密切相关。在基性类岩石中,由于富含铁、锰等深色元素,在酸性环境中很容易迁移,因而排水沟中出现Fe2O3和MnO2絮凝状沉淀物,导致排水沟出现混水现象。     

黄河聊城段侧渗分析研究

黄河在山东境内属地上河,常年补给两侧地下水,是沿河地带地下水资源的重要组成部分.依据黄河聊城段东阿县境内的艾山侧渗断面1986～1994年地下水位资料,在分析水文地质条件和地下水流态的基础上,应用水均衡原理分析计算导水系数T,并通过同位素示踪试验得到了验证.利用达西公式计算单侧年侧渗量,建立艾山水位、年径流-侧渗量关系,并与应量平衡法和地下水非稳定流公式计算的成果作了对照分析.     

Groundwater and surface-water interactions and impacts of human activities in the Hailiutu catchment,northwest China

The interactions between groundwater and surface water have been significantly affected by human activities in the semi-arid Hailiutu catchment, northwest China. Several methods were used to investigate the spatial and temporal interactions between groundwater and surface water. Isotopic and chemical analyses of water samples determined that groundwater discharges to the Hailiutu River, and mass balance equations were employed to estimate groundwater seepage rates along the river using chemical profiles. The hydrograph separation method was used to estimate temporal variations of groundwater discharges to the river. A numerical groundwater model was constructed to simulate groundwater discharges along the river and to analyze effects of water use in the catchment. The simulated seepage rates along the river compare reasonably well with the seepage estimates derived from a chemical profile in 2012. The impacts of human activities (river-water diversion and groundwater abstraction) on the river discharge were analyzed by calculating the differences between the simulated natural groundwater discharge and the measured river discharge. Water use associated with the Hailiutu River increased from 1986 to 1991, reached its highest level from 1992 to 2000, and decreased from 2001 onwards. The reduction of river discharge might have negative impacts on the riparian ecosystem and the water availability for downstream users. The interactions between groundwater and surface water as well as the consequences of human activities should be taken into account when implementing sustainable water resources management in the Hailiutu catchment.     

Role of geological structures in seepage from Lar dam reservoir

The main objective of this paper is to estimate the water seepage from Lar dam reservoir based on a combination of the geological structure study results and identification of the flow conduits in the right bank of the reservoir. From the beginning of impounding the dam in 1980, heavy seepage was observed at two karstic springs, Haraz and Galugah, located about 9 km downstream of the dam. During the first impounding, the discharge of the Haraz spring abruptly increased from 0.5 m³/s to around 5 m³/s. The results of piezometers and dye tests indicate that seepage occurs mainly through the right abutment of the dam where there is a structural wedge between the north dipping North Tiz Kuh and the south dipping Lar Valley faults. F1, F2, and F3 faults are the most important faults in vicinity of the structural wedge. Based on the dye test results, the North Tiz Kuh and F3 faults along which caves No. 1 and 2 are formed are regarded as two isolated conduits for seepage and conveyance into Lar Valley Fault at downstream of Lar dam. After identifying the conduits, water seepage from the Lar dam reservoir has been calculated using finite element method. According to the results of numerical method, when the reservoir water level is at 2485 m a.s.l, the average of water seepage is around 8.51 m³/s (this amount of water is related to the seepage along the Lar Valley Fault). The average discharge of springs downstream of the dam has been used to verify the numerical method. The results show a very close relation between estimated and observed discharge.     

充气位置及压力对边坡截排水效果的影响

充气截排水主要依据非饱和渗流理论,通过向坡体后缘压入气体驱除部分地下水,形成非饱和帷幕带,降低土体的渗透性,截排斜坡后缘地下水的入渗,降低潜在滑坡体内地下水位。多孔介质的多相渗流问题相当复杂,模拟技术往往是有效的研究方法。笔者以试验得到的地下水位及渗流量为基础进行数值反演分析,得到土质参数,构建数值计算模型,研究不同充气位置对边坡潜在滑坡区地下水位的影响。结果表明:在坡体后缘压入气体能够降低潜在滑坡区的地下水位线;在坡体后缘充气时,充气点放置在距离潜在滑坡区较近的位置时,截排水效果更好;充气点充气压力越大,潜在滑坡区的地下水位线下降得越多;选择充气点深度时,宜选择较深的充气深度,这样能够选择较大的充气压力。     

卡拉水电站坝区渗流控制效应精细模拟与评价

卡拉水电站坝址区河谷狭窄,岸坡陡峻,地质条件复杂,渗漏问题突出。为减小卡拉坝区渗漏并改善大坝的渗透稳定性,工程设计采取防渗帷幕、排水孔幕和排水洞等防渗排水措施。采用子结构、变分不等式和自适应罚函数相结合的方法（简称SVA方法）,结合典型溢流坝段与坝区整体渗流场分析成果,评价卡拉大坝及坝基渗流控制方案的合理性,并论证其优化的可能性。研究表明：①防渗帷幕有效雍高了帷幕上游侧岩体内的地下水位、增加了绕坝渗流的渗径长度并降低了坝基的扬压力,排水系统则显著降低了坝体内的孔隙水压力以及坝基扬压力;②排水孔幕间距对坝体内的自由面分布有着显著影响,排水孔幕间距取3.0～4.5 m是合适的。     

考虑非饱和渗流作用下三峡库岸滑坡稳定性研究

水库水位的涨落对库岸滑坡稳定性有着显著影响。三峡水库水位涨落引起滑坡体内地下水位的变化,是非饱和到饱和过程。本文就非饱和渗流理论,在库水位涨落过程中,模拟了三峡库区马家沟滑坡暂态渗流场的变化,分析了库水位变动时孔隙水压力的变化。结合有限元强度折减法,将得到的暂态孔隙水压力以荷载方式叠加到有限元中,对该滑坡稳定性进行评价,并探讨了在一个水文周期内水位涨落时滑坡稳定性的变化。结果表明:不论库水位上升或下降,滑坡体的稳定性都显示先减小后增大的趋势。最后对马家沟滑坡提出了在库水位常规下降速度下抗滑桩与地表排水相结合的治理设计方案。     

台风暴雨条件下滑坡地下水渗流特征及成因机制

台风暴雨常引发大量的滑坡灾害,造成生命财产损失,因而研究台风暴雨条件下滑坡地下水渗流特征及成因机制对滑坡的防治、预警预报具有重要意义.以浙江省中林村滑坡为例,采用有限元数值方法,模拟了台风暴雨的两种常见工况（工况1:等强度降雨;工况2:渐变强度降雨）下滑坡地下水的暂态渗流场及稳定性.结果表明:两种工况条件下,滑坡地下水渗流特征基本相同,地下水位响应迅速,地下水位位于强风化和中风化接触面附近,且在坡脚形成溢流;但是工况1较工况2地下水水位上升速度快、幅度大;滑坡稳定系数与地下水水位及降雨强度等密切相关,在高强度降雨条件下,随地下水水位上升稳定系数快速下降,水位稳定以后,稳定系数下降速度减缓;中林村滑坡为典型的滑塌-拉裂-蠕滑缓动型变形破坏模式,台风暴雨引起斜坡岩土体地下水水位上升,基质吸力降低和孔隙水压力增加是其发生变形破坏的主要原因.本文所得结论能够为东南沿海地区台风暴雨诱发滑坡的预测预报与防治提供理论支持.