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。     

傍河地下水位监测断面的优化设计

为了对傍河地下水位监测断面进行优化设计,更好地掌握地下水位动态时空变化特征,以安徽省亳州市河水-地下水监测断面为例,分别采用克里金法和时间序列法,通过分析监测断面上9口地下水位观测井及河水位观测点在1982年1月—1998年12月的水位观测数据,对观测井空间布局、井数和观测频率进行优化。结果表明：空间布局优化后的观测井数量由原来的9减少到3,平均相邻井距为1 000 m,优化后的水位克里金估计标准误差平均值为0.019 2 m,误差波动范围较小;观测频率优化后由5日一测变为10日一测,能够满足观测精度要求。     

华北平原地下水水位微动态变化周期特征分析

地下水位动态变化是外界影响因素的反映,微观动态也受到外界长期周期性影响。根据在华北平原设置的自动监测设备监测的高频率水位资料,利用频谱分析方法分析了地下水位微观动态,确定了周期变化特征。与天体潮汐所体现出的周期特征对比,说明华北平原(北京除外)大多数观测孔都受到天体潮汐作用的周期影响:其中沿海的部分浅层含水层地下水与海潮潮汐作用有关,个别观测孔受蒸散发作用影响体现出日变化;内陆大多数深层观测孔和个别浅层观测孔微动态受固体潮汐作用影响,反映了不同地区的含水层以及岩性特征。     

华北平原地下水位微动态变化周期特征分析

地下水位动态变化是外界影响因素的反映,微观动态也受到外界长期周期性影响。根据在华北平原设置的自动监测设备监测的高频率水位资料,利用频谱分析方法分析了地下水位微观动态,确定了周期变化特征。与天体潮汐所体现出的周期特征对比,说明华北平原(北京除外)大多数观测孔都受到天体潮汐作用的周期影响:其中沿海的部分浅层含水层地下水与海潮潮汐作用有关,个别观测孔受蒸散发作用影响体现出日变化;内陆大多数深层观测孔和个别浅层观测孔微动态受固体潮汐作用影响,反映了不同地区的含水层以及岩性特征。     

关于混合水位问题的探讨

对揭穿两个或两个以上含水层(或组)的观测孔,如未采取分层隔水措施,所观测的水位都是混合水位。目前地下水位观测中有相当部分为混合水位。从我们获得的长观资料看,同一地点(或距离很近)的长观井,在井深不同时,水位动态变化有很大差     

复杂滑坡体地下水分层观测技术与应用

滑坡勘测与防治工程实践证明, 地下水是滑坡体稳定性分析的敏感因子.因此, 获取滑坡体地下水位是滑坡勘测的重要目的之一.由于滑坡体组成物质的多样性与透水性差异, 滑坡体存在不同类型的地下水, 即多层地下水位.钻孔终孔水位所代表的是滑坡体综合水位, 不能区分滑坡体中存在的多层地下水位.应用地下水分层观测技术可以解决上述问题.系统地介绍了滑坡体地下水分层观测技术, 并以三峡工程库区和平广场、黄腊石滑坡为例, 分析了地下水分层观测成果对滑坡防治工程的意义.      

淄博地区深层地下水水质恶化问题浅析

本文在对山东淄博地区地下水水位长期观测和水质监测的基础上.分析了深层地下水水位动态和水质变化的规律,指出地下水位持续下降会引起水质变劣及其原因。     

华北东部平原深层抽水井水跃值计算方法及其规律研究

文章分析了目前常用的几种水跃值计算方法的适用性与不足,认为在华北东部平原地下水位变化强烈的漏斗区,这些方法均难以应用。同时提出了C—G法,即一次定流量抽水同步观测抽水井和观测井的水位,合理地解决了区域背景水位对水跃值计算的影响。研究表明,与修正后的多次定流量试验法——两次定流量抽水法相比,C—G法计算结果可靠。然后探讨了如何间接获取抽水期间抽水层区域背景水位动态资料的方法,校正背景水位波动对抽水水位的影响,采用自动水位计(DIVER)同步监测井中大气压对地下水位的影响。最后分析水跃值随时间和抽水井水位降深的变化规律。     

海潮及其影响下海岸带地下水位时间序列的周期性和滞后性

运用谱分析原理，对广西北海市海潮及受海潮影响的滨海含水层地下水位时间序列进行分析，求出海潮和观测孔水位变化的周期及地下水位滞后于海潮的时间，分析水位滞后时间与离海岸的垂直距离之间的关系。结果表明，北海市海潮和海岸带地下水位有约344．82h（14．37d）的长周期变化和约24．7h、12．5h的短周期波动，距海岸2175、2350、2375m的3个观测孔地下水位对海潮的滞后时间分别为5．5、6．25和7h，滞后时间随离海岸的距离增大大体上呈线性增加。     

基于长观水位及历史降雨量的建筑抗浮水位取值研究

以贵阳市地铁2号线三桥站主体结构基坑抗浮为研究对象,根据长观孔3~5年地下水位与降雨量关系对地下水位动态变化进行分析,提出一种定量计算抗浮水位的取值方法:抗浮水位值包括三个部分,勘察期间场区地下水最高水位（Hkmax）、可能的意外补给造成该层地下水位的上升值（ΔH0）及该层地下水相对勘察时的最大变幅值（ΔHe）;长观孔地下水位呈雨季升高、枯季下降的变化规律,最高水位出现在6、7月份;通过对4、5、6月份的降雨量与观测孔水位进行线性拟合,得到地下水位变化量与月降雨量变化量的线性变化关系;结合历史降雨量推测场区地下水位的最大升幅为2.26 m,进而计算场区的抗浮水位为1 128.46 m。      

The depth vs. depth plot: An aid to selecting piezometer installation depths in boreholes

Dick, R.C., 1976. The depth vs. depth plot: an aid to selecting piezometer installation depths in boreholes. Eng. geol., 10: 37–42.The location of the piezometric surface within a soil or rock mass is often the critical factor in stability analysis and in evaluations of reservoir watertightness. Sealed piezometers are now almost universally used to measure water pressure within the mass. The location of these piezometers must be decided immediately upon completion of each borehole. A common aid to making this decision is a plot of borehole depth and borehole water level as functions of time. This paper introduces the reader to another way to evaluate the same data, with the borehole water depth plotted as a function of borehole depth. Anomalies can be detected more easily, and piezometers installed within these zones. Examples are given.     

Calculation of barometric efficiency in shallow piezometers using water levels, atmospheric and earth tide data

The variation in atmospheric pressure at Baldry in New South Wales, Australia (32^°52′ S, 148^°32′ E), has been determined using a 4-year record of hourly measurements. Fourier analysis of this data shows clear diurnal and semi-diurnal variation in atmospheric pressure caused by atmospheric tides. The semi-diurnal component of the tide changes little with the seasons and induces a barometric response in shallow confined piezometers. The piezometer response is shown to be contaminated by an earth-tide component that has to be removed before accurate barometric efficiencies can be calculated. Data from three piezometers installed in a region of fractured and weathered granite are described in this paper. The results show that piezometers installed in shallow bedrock can have barometric efficiencies of close to unity and that only a small quantity or thickness of lower permeability material is sufficient to cause confining conditions. This observation has important implications for the interpretation of recharge processes in shallow aquifers.     

Dynamic response and pore pressure model of the saturated soft clay around the tunnel under vibration loading of Shanghai subway

This paper studies the saturated soft clay around the tunnel between Jingansi Station and Jiangsu Station of Shanghai subway line No.2. The continuous dynamic monitoring is conducted by means of embedded earth pressure piezometers and pore piezometers around the tunnel. The response frequency and stress amplitude of the saturated soft clay are studied with the distance from the tunnel due to the subway vibration loading. A formula is proposed for the attenuation of the dynamic pressure response in the soil. Then, based on the continuous field monitored data, and using the laboratory GDS (Global Digital System) test apparatus, the developing law of the pore water pressure of the saturated soft clay around tunnel is explored with the distance. By the GDS test, the model of the increasing pore water pressure of the saturated soft clay is put forward under the vibration loading. It is also amended by field monitored data. Finally the model is obtained. The result offers a valuable reference to the design, construction and the safe operation of the subway tunnel.     

Combined climatic and geological forcings on the spatio-temporal variability of piezometric levels in the chalk aquifer of Upper Normandy (France) at pluridecennal scale

The temporal variability of water-level fluctuations in the chalk aquifer of Upper Normandy, France is constrained by natural climate fluctuations and is closely linked to the regional geological patterns. The chalk plateaus are covered with 5–50 m thick semi-permeable surficial formations; the thickness of the underlying chalk aquifer varies from 50 to 300 m. The relationship among climate oscillations, piezometric levels, and geologic structure were investigated by correlation, Fourier spectral, and continuous wavelet analyses of selected piezometric time-series data. Analysis focused on two piezometers located on the uplifted side of a major fault and two piezometers on the downthrown side. After generalization to other piezometers in the region, it was deduced that, in the downthrown compartments, a substantial aquifer and surficial formations thickness would imply a strong attenuation of annual variability, while multi-year variability is clearly expressed. Conversely, in the uplifted compartments, a thin layer of surficial formations and small thickness of the chalk authorizes strong variations on the annual mode with respect to the contribution of long-term climatic oscillations (multi-year variability). The results then demonstrated—and proposed a spatial determination of—the differential influence of geological patterns on the filtering of climate-induced oscillations in piezometric variability.     

Basic relationships in distribution of modern siliceous sediments and their connection with climatic zonation

This is the third installment of the Lisitsyn monograph which began in the May IGR (v. 9, no. 5). The fourth and concluding installment will be published in August.     

Bias in hydraulic head measurements from multilevel vibrating-wire piezometers with excessively permeable backfill

Hydrogeology Journal - An extensive network of multilevel vibrating-wire piezometers (VWP) was recently created to monitor the spatial and temporal variation of pore pressure (and hydraulic head)...     

挡土墙填土边坡水文响应过程分析以赖屋山挡土墙填土边坡为例

深圳赖屋山的一挡墙表面出现数条裂缝,为了深入研究其变形破坏机制,在挡墙背后填土区布置自动监测仪器,主要包括渗压计、张力计与水分计及固定式测斜仪。通过对渗压计、张力计和水分计的监测数据分析表明:填土内地下水位埋深大,降雨对其影响小; 土体中孔隙压力和体积含水量对强降雨响应随着埋深存在不同程度的滞后性,强降雨入渗深度大于3m,并且在3m处形成瞬态饱和地下水,抗剪强度降低,易于引起边坡的浅层变形破坏。      

Development of unconfined conditions in multi-aquifer flow systems: a case study in the Rajshahi Barind,Bangladesh

Identifying flow processes in multi-aquifer flow systems is a considerable challenge, especially if substantial abstraction occurs. The Rajshahi Barind groundwater flow system in Bangladesh provides an example of the manner in which flow processes can change with time. At some locations there has been a decrease with time in groundwater heads and also in the magnitude of the seasonal fluctuations. This report describes the important stages in a detailed field and modelling study at a specific location in this groundwater flow system. To understand more about the changing conditions, piezometers were constructed in 2015 at different depths but the same location; water levels in these piezometers indicate the formation of an additional water table. Conceptual models are described which show how conditions have changed between the years 2000 and 2015. Following the formation of the additional water table, the aquifer system is conceptualised as two units. A pumping test is described with data collected during both the pumping and recovery phases. Pumping test data for the Lower Unit are analysed using a computational model with estimates of the aquifer parameters; the model also provided estimates of the quantity of water moving from the ground surface, through the Upper Unit, to provide an input to the Lower Unit. The reasons for the substantial changes in the groundwater heads are identified; monitoring of the recently formed additional water table provides a means of testing whether over-abstraction is occurring.     

Measurement and Analysis of Pore Water Pressure in Large Caverns and Shafts in a Hydro-electric Project

With an objective to understand the behaviour of pore water pressure around large underground openings, piezometers were installed in the rock around the desanding chambers, surge shaft, its drainage galleries, and the transformer cavern of a large hydro-electric project. The monitored data indicated that the pore water pressure was insignificant in the rock surrounding the desanding chambers prior to lining. On completion of the concrete lining of the chambers, the maximum pore water pressure was about 50 kPa as the flow of water was restricted. When one of the desanding chambers was charged with water, the piezometers around it indicated an excessive increase in the pore water pressure due to seepage of water from the chamber. Thus the piezometer readings were useful in taking appropriate remedial measures. In the surge shaft, higher values of pore water pressure were recorded on the hill side of the shaft as compared to the valley side. In one of the drainage galleries, the pore water pressure gradually increased to 450 kPa, which was released by drilling relief holes in the area. In the other drainage gallery, no significant change in the pore water was recorded. In the transformer cavern, the recorded pore water pressures were within 20 kPa.     

Comparative tracing experiments in a porous aquifer using bacteriophages and fluorescent dye on a test field located at Wilerwald (Switzerland) and simultaneously surveyed in detail on a local scale by radio-magneto-tellury (12–240 kHz)

This article presents an example of a tracing experiment using two bacteriophages, T7 and f1, and a fluorescent dye (naphthionate), in a saturated porous environment. The test field was equipped with an injection borehole and 22 sampling piezometers set in three concentric half-circles. The distribution of permeabilities and the thickness of the aquifer were indirectly determined by Radio-Magneto-Tellury (RMT, 12–240 kHz). The results reveal a good correlation between the distribution of permeabilities obtained by RMT and the breakthrough curves and speed of migration of all three tracers. The restitution levels are far superior (by two to three orders of magnitude) in the more permeable zones, as opposed to those observed in th piezometers situated in less permeable areas. The speed of migration of the biological tracers is much greater than that of the naphthionate. In the most extreme case, the T7 bacteriophage migrated about 3.15 times faster than the chemical solution. These results indicate that bacteriophages are able to travel considerable distances along permeable gravel channels. They may be used as biological tracers and as models for the migration of pathogenic viruses. The simultaneous use of tracing techniques and appropriate geophysical methods leads to a better knowledge of the hydrogeological parameters of the underground terrain. This combination allows for a better interpretation both of the speeds of migration and of the maximal concentrations of the tracers, and thus considerably increases the interpretability of hydrogeological impact studies.