河床沉积物中有机质对其垂向渗透系数的影响分析

采用水头下降立管法对渭河5个区域的河床渗透系数进行测定,并在室内分析其粒径分布及有机质含量。运用SPSS18.0软件分析不同类型的沉积物中有机质含量与其垂向渗透系数的关系。结论为:有机质主要通过改变黏土的结构从而改变沉积物的结构,进而影响垂向渗透系数值的大小;有机质对垂向渗透系数的影响关系与沉积物中有机质含量及黏土含量的组合关系密切相关。     

浅层地热能勘察和评估应用研究

对浅层地温能工程场地进行勘察和应用条件评估是地源热泵系统方案设计的重要环节。以南京板桥地产浅层地热能勘探应用为例,介绍多功能地下水能量测井仪的功能及其在浅层地热能勘探中的应用,探讨水文地质前期勘探工作对浅层地热能资源开采的作用与意义。该测井仪能够在单井中,一次性完成对浅层地热能参数:地下水的水量、温度、电导、各含水层的静水头高度、储水量、地下水的水平和垂向运动流速和方向、地层渗透系数、导水系数等的定量测量,查明地下水的层间补给关系,为热泵选型、埋深和分布密度提供平面矢量、垂向断面高程等多种高精度参数。     

庆阳工业废弃物填埋场渗水试验及防治措施

渗水试验是野外测定包气带非饱和松散岩(土)层渗透系数常用的简易方法,试验的结果更接近实际情况。通过对第四系下更新统午城黄土表层风化层和未风化层上进行3组渗水试验,确定包气带岩性的垂向渗透系数,为填埋场内包气带渗透性评价提供参数依据,根据渗水试验结果提出两水截排及防渗处理措施,同时加强地下水监测工作,以防地下水环境污染。     

渭河河漫滩宏观弥散度计算

宏观弥散度的确定对地下水溶质运移至关重要。利用竖管法野外现场测定900个点的垂向饱和渗透系数Kv值,然后进行统计分布检验,运用地质统计学中负指数模型在有块金效应影响的条件下拟合出ln Kv的空间相关尺度λ值,进而利用λ与宏观弥散度关系式求解渭河漫滩非饱和带的宏观弥散度。结果表明,研究区整体Kv平均值为0.012cm/s,方差为1.33,表明Kv空间差异性较大;垂向渗透系数基本服从对数正态分布规律,满足宏观弥散度计算条件;估算整体纵向宏观弥散度为21.27m,各排计算结果约2.11~4.65m。     

基于数值模拟的岩溶地下水源保护区划分技术研究

以山东省邹城市某岩溶水源地为例,研究数值模拟方法在岩溶地下水水源地保护区划分中的应用,以及水文地质参数对于水源地保护区划分结果的影响。基于GMS软件构建了研究区三维非稳定流地下水数值模型,采用质点追踪技术,通过反向追踪示踪粒子在运移100 d、1 000 d以及25 a后的位置及迁移轨迹,对该岩溶水源地进行保护区划分;改变数值模型中的主要水文地质参数,以变化后的保护区面积作为衡量参数敏感度的指标,并计算各参数的敏感度系数,研究水文地质参数对于保护区划分范围的影响。结果表明:当参数改变幅度在20%范围内时,一层垂向渗透系数(VK1)的敏感度系数最大可达到2.63×10-3,二层垂向渗透系数(VK2)的敏感度系数最大可达到3.64×10-3;垂向渗透系数的敏感度明显高于其他参数,说明垂向渗透系数对保护区划分范围的影响最大。因此,在应用数值模拟法对岩溶地下水源地进行保护区划分时,应尤其注意模型中各含水层垂向渗透系数取值的准确性和合理性。      

注水试验与放水试验求取渗透系数的差异

基于矿井涌水量计算及水资源评价需要,本文运用注水试验代替抽水试验,求取了太原组灰岩含水层的渗透系数。根据后期同一含水层井下放水试验资料,利用VISUAL MODFLOW建立了水文地质三维非稳定流数值模型,通过分区拟合调参,获得了含水层分区水文地质参数。通过对这两种试验求得的渗透系数进行比较,得出在裂隙介质中注水试验是放水试验所得渗透系数值的35.6%~50.8%。建议在不具备进行抽（放）水试验的条件下,可使用注水试验代替,所得渗透系数值乘以校正系数,用校正后的渗透系数来计算矿井涌水量。     

大坡度地质露头高分辨率无人机影像采集方法与建模实践*

野外地质露头的观察、研究能够最直接、最有效地获取地下地层信息,为地质科学研究提供最直观、最真实的一手地质资料。然而传统的露头研究,尤其针对大坡度、人员无法到达区域的露头研究,主要依赖坡底部考察、测量和拍照等方式记录露头信息,难以精细、准确地表征整个地质体。消费级无人机具有机动性好、适应性强和成本低等优势,且能够近距离、多视角、变高度地获取露头影像。本研究对无控制点情况下的大坡度地质露头影像采集方法与模型构建精度进行探讨,利用消费级无人机垂向航线采集影像,然后构建模型。结果证明倾斜摄影测量技术结合消费级无人机能够有效地构建具有毫米分辨率精度的大坡度地质露头模型。构建的模型具有分辨率高、分辨率均一、量测精度可达毫米等特点,可有效降低野外考察的工作难度,降低人员安全风险,真实准确地复现野外大坡度露头情况,为大坡度露头剖面解译、分析和量测提供真实可靠的数据基础。     

张家港暨阳湖湖底沉积物渗透系数的现场测定

在湖水与地下水相互作用的定量研究中 ,湖底沉积物的渗透系数是极其重要的参数之一。湖底沉积物渗透系数的传统测定方法主要为实验室分析法。该方法不能进行渗透系数的现场测定。竖管测定法可现场测定湖底沉积物的渗透系数。在张家港暨阳湖已开挖的湖区约 0 .3km2 的范围内进行了 2 9个点的野外现场测定。其垂向渗透系数的平均值为 2 .76× 10 -7cm/s。暨阳湖湖底沉积物的渗透性等级为极微透水     

考虑自愈合效应的泥岩巷道开挖扰动区渗透性反演分析

泥岩自愈合特性是核废料库选址评价及储库安全稳定性分析的一项重要研究内容。以某泥岩高放废物处置库为研究背景,在室内和现场试验的基础上,采用指数模型建立了巷道围岩渗透性分布模型和裂隙渗透性自愈合模型;结合巷道围岩孔隙水压力的多年观测资料,通过建立能够反映实际施工过程的水-力耦合计算模型,采用精确罚函数法以及Nelder-Mead算法相结合的有限元优化反分析程序,对巷道围岩渗透性参数进行反演研究。结果表明：反演所得的围岩渗透系数量级与试验值量级均为10-12 m/s,反演孔隙水压力值与实测值比较接近;围岩垂向渗透系数的扰动程度和范围明显大于水平向渗透系数,垂向渗透系数提高了2个数量级,扰动范围约为25 m,渗透性恢复到初始水平时间约需5 a。     

内蒙古开鲁盆地水文地质实体结构分析与判识

本文根据大量的野外地质钻探、水文地质试验、岩性调查等资料 ,从区域地下水形成的地质条件入手进行分析。查明了研究区第四纪地质实体各期岩相古地理、沉积构造特征、地层空间结构、沉积物粒度的空间变异 ,据此进行了地层分区。为研究区含水层系统的分析与辩识 ,研究垂向水交替 ,准确测定有关参数提供可靠的地质依据。     

Multi-scale aquifer characterization and groundwater flow model parameterization using direct push technologies

Direct push (DP) technologies are typically used for cost-effective geotechnical characterization of unconsolidated soils and sediments. In more recent developments, DP technologies have been used for efficient hydraulic conductivity (K) characterization along vertical profiles with sampling resolutions of up to a few centimetres. Until date, however, only a limited number of studies document high-resolution in situ DP data for three-dimensional conceptual hydrogeological model development and groundwater flow model parameterization. This study demonstrates how DP technologies improve building of a conceptual hydrogeological model. We further evaluate the degree to which the DP-derived hydrogeological parameter K, measured across different spatial scales, improves performance of a regional groundwater flow model. The study area covers an area of ~60 km² with two overlying, mainly unconsolidated sand aquifers separated by a 5–7 m thick highly heterogeneous clay layer (in north-eastern Belgium). The hydrostratigraphy was obtained from an analysis of cored boreholes and about 265 cone penetration tests (CPTs). The hydrogeological parameter K was derived from a combined analysis of core and CPT data and also from hydraulic direct push tests. A total of 50 three-dimensional realizations of K were generated using a non-stationary multivariate geostatistical approach. To preserve the measured K values in the stochastic realizations, the groundwater model K realizations were conditioned on the borehole and direct push data. Optimization was performed to select the best performing model parameterization out of the 50 realizations. This model outperformed a previously developed reference model with homogeneous K fields for all hydrogeological layers. Comparison of particle tracking simulations, based either on the optimal heterogeneous or reference homogeneous groundwater model flow fields, demonstrate the impact DP-derived subsurface heterogeneity in K can have on groundwater flow and solute transport. We demonstrated that DP technologies, especially when calibrated with site-specific data, provide high-resolution 3D subsurface data for building more reliable conceptual models and increasing groundwater flow model performance.     

Analytical solutions for consolidation aided by vertical drains

Soil disturbance caused during the installation of vertical drains reduces the in situ hydraulic conductivity of soft deposits in the immediate vicinity of the drains, resulting in a slower rate of consolidation than would be expected in the absence of disturbance. Experimental investigations have revealed the existence of two distinct zones, a smear zone and a transition zone, within the disturbed zone around the vertical drain. The degree of change in the hydraulic conductivity in the smear and transition zones is difficult to assess without performing of laboratory tests. Based on the available literature, four different profiles of hydraulic conductivity versus distance from the vertical drain were identified. Closed-form solutions for the rate of consolidation for each of these four hydraulic conductivity profiles were developed. It is found that different variations of the hydraulic conductivity profiles in the disturbed zone result in different rates of consolidation.     

Development and parameterisation of a complex hydrogeological model based on high-resolution direct-push data

Ongoing developments in geological and hydrogeological investigation techniques, especially direct-push methods, have led to an increase in the quality, density and spatial resolution of data available from such investigations. This has created new challenges in the development of numerical models in terms of accurately and efficiently translating detailed and complex conceptual models into effective numerical models. Suitable geometrical and numerical modelling tools are essential in order to meet these challenges. This paper describes the development of a three-dimensional hydrogeological flow model for a contaminated site near Berlin, Germany, based on high-resolution geological data obtained principally using direct-push methods. The available data were first interpreted to construct a detailed GIS-based geological model, which formed the basis of the conceptual site model. The conceptual model was then translated into a geometrical model, which was used to create a finite element numerical model. An innovative geometry object-based approach enabled the complex structural details of the conceptual model to be accurately reproduced in the numerical model domain. The resulting three-dimensional steady-state unconfined flow model was successfully calibrated using external automated calibration software, whereby parameter values for groundwater recharge and hydraulic conductivity were determined.     

Thermal tracer testing in a sedimentary aquifer: field experiment (Lauswiesen,Germany) and numerical simulation

An active and short-duration thermal tracer test (TTT) was conducted in a shallow sedimentary aquifer at the Lauswiesen test site, near Tübingen, Germany. By injecting 16  m³ of warm water at 22°C, a thermal anomaly was created, which propagated along the local groundwater flow direction. This was comprehensively monitored in five observation wells at a few meters distance. The purpose of this well-controlled experiment was to determine the practicability of such a TTT and its suitability to examine hydraulic characteristics of heterogeneous aquifers. The results showed that the thermal peak arrival times in the observation wells were consistent with previous observations from alternative field testing such as direct-push injection logging (DPIL). Combined analysis of depth-dependent temperatures and peak arrival times, and comparison with a numerical heat transport model, offers valuable insights into the natural flow field and spatial distribution of hydraulic conductivities. The study was able to identify vertical flow focusing and bypassing, which are attributed to preferential flow paths common in such sedimentary sand and gravel aquifers. These findings are fundamental for further development of experimental designs of active and short-duration TTTs and provide a basis for a more quantitative analysis of advective and conductive transport processes.     

不同饱和黏性土渗透系数预测方法的应用与对比:以苏北沿海平原黏土为例

渗透系数(K)是水文地质、岩土工程领域的重要参数,而低渗透介质的结构较为复杂,在实际应用中,场地的尺度、介质的扰动程度等均会对K的确定产生影响.利用δ18O化学示踪法、室内试验及经验公式法估算饱和黏性土的垂向渗透系数,并对比分析不同预测方法的适用性.以苏北沿海平原第四纪厚层黏土为例,δ18O化学示踪法预测厚层黏性土的渗透系数低于10-11 m/s,室内法测得渗透系数为2.61×10-8~9×10-12 m/s,经验法预测值较大,是室内法的几倍到几十倍.δ18O化学示踪法是表征天然条件下长时间的实验结果,除了反映数十米厚层黏性土的等效渗透性能,还可预测黏土孔隙水的渗流时间;结合测定黏土样品液塑限等室内实验参数,室内实验和经验公式法可以提供系列剖面黏土的渗透系数,更清晰地说明厚层黏土剖面不同渗透系数预测方法的差异性.      

Investigating spatial variability of vertical water fluxes through the streambed in distinctive stream morphologies using temperature and head data

Investigating the interaction of groundwater and surface water is key to understanding the hyporheic processes. The vertical water fluxes through a streambed were determined using Darcian flux calculations and vertical sediment temperature profiles to assess the pattern and magnitude of groundwater/surface-water interaction in Beiluo River, China. Field measurements were taken in January 2015 at three different stream morphologies including a meander bend, an anabranching channel and a straight stream channel. Despite the differences of flux direction and magnitude, flux directions based on vertical temperature profiles are in good agreement with results from Darcian flux calculations at the anabranching channel, and the Kruskal-Wallis tests show no significant differences between the estimated upward fluxes based on the two methods at each site. Also, the upward fluxes based on the two methods show similar spatial distributions on the streambed, indicating (1) that higher water fluxes at the meander bend occur from the center of the channel towards the erosional bank, (2) that water fluxes at the anabranching channel are higher near the erosional bank and in the center of the channel, and (3) that in the straight channel, higher water fluxes appear from the center of the channel towards the depositional bank. It is noted that higher fluxes generally occur at certain locations with higher streambed vertical hydraulic conductivity (K _v) or where a higher vertical hydraulic gradient is observed. Moreover, differences of grain size, induced by stream morphology and contrasting erosional and depositional conditions, have significant effects on streambed K _v and water fluxes.     

Determination of the anisotropy of an upper streambed layer in east-central Nebraska, USA

Information on the anisotropy of streambed hydraulic conductivity (K) is a necessity for analyses of water exchange and solute transport in the hyporheic zone. An approach is proposed for the determination of K, developed from existing in-situ permeameter test methods. The approach is based on determination of vertical and horizontal hydraulic conductivity of streambed sediments on-site and eliminates the effects of vertical flow in the hyporheic zone and stream-stage fluctuation, which normally influence in situ permeameter tests. The approach was applied to seven study sites on four tributaries of the Platte River in east-central Nebraska, USA. On-site permeameter tests conducted on about 172 streambed cores for the determination of vertical hydraulic conductivity (K _v) and horizontal hydraulic conductivity (K _h) at the study sites indicate that the study sites have relatively small anisotropic ratios, ranging from 0.74 to 2.40. The ratios of K _h to K _v from individual locations within a study site show greater variation than the anisotropic ratios from the mean or median K at each of the study sites.     

Regional fracture network permeability using outcrop scale measurements

Estimating the hydraulic properties of fractured aquifers is challenging due to the complexity of structural discontinuities that can generally be measured at a small scale, either in core or in outcrop, but influence groundwater flow over a range of scales. This modeling study uses fracture scanline data obtained from surface bedrock exposures to derive estimates of permeability that can be used to represent the fractured rock matrix within regional scale flow models. The model is developed using PETREL, which traditionally benefits from high resolution data sets obtained during oil and gas exploration, including for example seismic data, and borehole logging data (both lithological and geophysical). The technique consists of interpreting scanline fracture data, and using these data to generate representative Discrete Fracture Network (DFN) models for each field set. The DFN models are then upscaled to provide an effective hydraulic conductivity tensor that represents the fractured rock matrix. For each field site, the upscaled hydraulic conductivities are compared with estimates derived from pumping tests to validate the model. A hydraulic conductivity field is generated for the study region that captures the spatial variability of fracture networks in pseudo-three dimensions from scanline data. Hydraulic conductivities estimated using this approach compare well with those estimated from pumping test data. The study results suggest that such an approach may be feasible for taking small scale fracture data and upscaling these to represent the aquifer matrix hydraulic properties needed for regional groundwater modeling.     

Comparison of approaches for the characterization of contamination at rural megasites

The present work focuses on approaches for the characterization of subsurface contamination, which need to be reliable and cost-effective, particularly for extended and remote areas aimed at being redeveloped. Requirements are discussed with respect to specific conditions at megasites, in order to enable site valorization. In a case study, two approaches are compared, comprising (1) conventional site investigation based on historical surveys and concentration measurements at monitoring wells installed in areas suspected of being polluted and (2) the use of direct push (DP) methods covering the complete area. The DP investigation provided information on the contamination distribution and yielded also important information on hydraulic conditions. Statistical analysis of the results applying indicator kriging revealed that the conventional approach is markedly risky when decision-making relies solely on historical and sparse data. The DP campaign remarkably reduced the uncertainty concerning the estimated occurrence of polluted groundwater at the whole site. Furthermore, monitoring measurements are analyzed showing the possible importance of temporal variability. Taking economical consideration into account, DP-based groundwater screening is recommended to obtain either first or complementary information on the entire site. Based on these data, also locations for a long-term monitoring could be selected if temporal variability is assumed relevant.     

Confined groundwater near the rockhead in igneous rocks in the Mid-Levels area, Hong Kong, China

It is customary in Hong Kong to assume that the hydraulic conductivity of weathered igneous rocks decreases with depth or as the rock mass becomes less weathered. Such a hydraulic conductivity pattern can only lead to an unconfined aquifer. This paper presents a case study in the regions in and around the Mid-Levels area in Hong Kong regarding a possible relatively high hydraulic conductivity (K) zone and confined groundwater along the rockhead. The Mid-Levels area is located at the lower part of the north-facing slopes of Victoria Peak on Hong Kong Island and is prone to landslides. Although this site has a long history of geotechnical studies because of extensive urban development along the coast and public concern on slope stability, hydrogeology of the site remains poorly understood. This paper reexamined the hydraulic conductivity data in 7 boreholes conducted in the 1970s and found that 4 of them indicate an increase in K at the rockhead. Groundwater conditions revealed by tunnel construction at the coast suggest that K close to the rockhead is about 10 times greater than above rockhead. A careful analysis of storm response of a piezometer group with tips in different depths indicates that there was an upward flow from the bedrock to the colluvium. A field study of two overflow standpipes conducted by the authors showed that the water level can be 0.64 and 3.73 m above the ground surface, which illustrates that the deep groundwater is significantly artesian. A search of the archived site investigation reports from the government and private companies has led to an identification of about 24 sites with overflow boreholes, which suggests that overflow phenomenon is quite common in the study area. The paper then concludes that in the study area there is a relatively high K zone along the rockhead and the groundwater in the zone is confined. It is recommended that geotechnical engineers should carry out a more careful field study on an overflow borehole because such a borehole indicates a confined groundwater condition important for slope stability study and foundation design.