Measurement Of Hydraulic Properties Research Articles

Unsaturated hydraulic property measurements of subtropical anthropogenic (purple) soils in China

AbstractMany anthropogenic soils, often referred to as red bed or purple soils, are distributed in various areas of southern China. Purple soils typically are highly weathered and often lead to natural and engineering hazards because of their relatively poor water retention properties. Knowledge of the unsaturated soil hydraulic properties of purple soils is crucial for their optimal management and various assessment studies. In this work, the hydraulic properties of purple soils from southern China were measured in the laboratory over the full moisture range using a combination of evaporation (HYPROP) and psychrometer (WP4C) approaches. Measured data were analyzed in terms of four different unimodal and bimodal soil hydraulic models. The measurements and analyses showed that bimodality was not overly significant for most samples. The good fit of the Peters–Durner–Iden models furthermore suggested that corner and film flows were important under relative dry conditions. Existing soil pedotransfer functions were found to provide a fairly close match for the slope of water retention curves with the exception of near saturated water contents and the saturated conductivity. To the best of our knowledge, this is the first time that unsaturated hydraulic data of purple soils are provided over the full moisture range.

The effect of weathering on cohesion in granitic fault rocks: A case study from the Yeongdeok Fault, South Korea

Weathering can alter fault-rock cohesion, which is an important criterion in the classification of fault rocks, and can also alter fault-rock mechanical and hydraulic properties. To investigate the effects of weathering on fault rocks, we studied relatively fresh and weathered fault rocks collected from a drill core and outcrop, respectively, of a granitic fault zone (the Yeongdeok Fault, a northern branch of the Yangsan Fault) on the southeastern Korean Peninsula. At the studied outcrop, the Yeongdeok Fault has juxtaposed Triassic granite against Cretaceous sedimentary rocks. Granitic fault rocks in the outcrop are incohesive, whereas the drill core includes both cohesive and incohesive granitic fault rocks. A detailed correlation of the fault rocks from the drill core with those from the outcrop reveals that some incohesive fault rocks from the outcrop are weathered cataclasite. Cataclasites from the drill core are composed of feldspar, plagioclase, and quartz fragments embedded in a matrix of quartz, plagioclase, muscovite, and chlorite. Locally, foliation defined by the preferred orientation of muscovite is developed. The weathered cataclasite comprises quartz, plagioclase, and feldspar fragments, with a fine-grained matrix composed mostly of clay minerals. The measured Chemical Index of Alteration (CIA) values for cataclasite and weathered cataclasite are 47–49 and 60–67, respectively. Measurements of hydraulic properties show that weathered cataclasite has higher porosity and permeability compared with unweathered cataclasite. Physical and chemical weathering are interpreted to have increased the fracture density of the weathered cataclasite and enhanced the dissolution of vein minerals, respectively. These processes have not only contributed to the higher permeability and porosity of the weathered (cf. unweathered) cataclasite but have also resulted in a loss of cohesion. When cohesion is lost due to weathering, distinguishing between cataclasite and fault breccia becomes challenging. Our study demonstrates that the cohesion-based classification of fault rocks becomes limited for fault rocks with CIA value more than 60.

Controls on Saturated Hydraulic Conductivity in a Degrading Permafrost Peatland Complex

AbstractPermafrost peatlands are vulnerable to rapid structural changes under climatic warming, including vertical collapse. Peatland water budgets, and therefore peat hydraulic properties, are important determinants of vegetation and carbon fluxes. Measurements of hydraulic properties exist for only a limited number of permafrost peatland locations, primarily concentrated in North America. The impacts of thaw‐induced collapse upon properties such as horizontal saturated hydraulic conductivity (Kh), and thus lateral drainage, remain poorly understood. We made laboratory determinations of Kh from 82 peat samples from a degrading Swedish palsa mire. We fitted a linear mixed‐effects model (LMM) to establish the controls on Kh, which declined strongly with increasing depth, humification and dry bulk density. Depth exerted the strongest control on Kh in our LMM, which demonstrated strong predictive performance (r2 = 0.605). Humification and dry bulk density were influential predictors, but the high collinearity of these two variables meant only one could be included reliably in our LMM. Surprisingly, peat Kh did not differ significantly between desiccating and collapsed palsas. We compared our site‐specific LMM to an existing, multi‐site model, fitted primarily to boreal and temperate peatlands. The multi‐site model made less skillful predictions (r2 = 0.528) than our site‐specific model, possibly due to latitudinal differences in peat compaction, floristic composition and climate. Nonetheless, low bias means the multi‐site model may still be useful for estimating peat Kh at high latitudes. Permafrost peatlands remain underrepresented in multi‐site models of peat hydraulic properties, and measurements such as ours could be used to improve future iterations.

Examination of Measured to Predicted Hydraulic Properties for Low Impact Development Substrates

To counter the impacts of climate change and urbanization, engineers have developed ingenious solutions to reduce flooding and capture stormwater contaminants through the use of Low Impact Developments (LIDs). The soil is generally considered to be completely saturated when designing for the LIDs. However, this may not always be an accurate or realistic approach, as the soil could be variably unsaturated leading to inaccurate designs. To analyse the flow under variably unsaturated conditions, Richards’ equation can be used. To solve the Richards’ equation, two nonlinear hydraulic properties, namely soil water characteristic curve (SWCC) and the unsaturated hydraulic conductivity function are required. Laboratory and field measurements of unsaturated hydraulic properties are cumbersome, expensive and time- consuming. Pedotransfer functions (PTFs) estimate soil hydraulic properties using routinely measured soil properties. This paper presents a comparison between the direct measurement obtained through experimental procedures and the use of PTFs to estimate soil hydraulic properties for two green roof and three bioretention soil medias. Comparison between the measured and estimated soil hydraulic properties was accomplished using two different approaches. Statistical analyses and visual comparisons were used to compare the measured and estimated soil hydraulic properties. Additionally, numerical modelling to predict the water balance at the ground surface was conducted using the measured and estimated soil hydraulic properties. In some instances, the use of predicted hydraulic properties resulted in overestimation of the cumulative net infiltration of as much as 60 % for the green roof substrate, but was considered negligible for the bioretention substrate. Design performance criteria for green roof and bioretention facilities were examined using the measured and estimated soil hydraulic properties under extreme precipitation analysis. Results indicate that there is a high level of uncertainty when using PTFs for LID materials. A percent difference between the measured and predicted properties for the green roof peak time delay under a 2-year storm can be as much as 300%. For the bioretention design criteria of a 25-year storm, the surface runoff was overestimated by 14.7 cm and by 100% for the ponding time percent difference.

Experimental investigation of thermal efficiency and thermal performance improvement of compound parabolic collector utilizing SiO2/Ethylene glycol-water nanofluid.

A compound parabolic collector has been used in the present study to lower operating costs per unit of heat increase compared to other tracker concentrators. This type of collector has been given more attention in industrial and domestic applications in the temperature range of 60 to 300°C. Also, to increase the thermal efficiency, nanofluid containing SiO2 nanoparticles in ethylene glycol-water hybrid base fluid (10-90 vol.%) have been used in three different volumetric fractions. The innovation of this present study includes the utilization of mentioned nanofluids for the first time in this collector, which has good stability and is cost-effective compared to other nanoparticles. In addition, the experimental measurement of thermal and hydraulic properties of nanofluids represents new aspects of the present study. The experiments used three volumetric fractions of 0.5%, 1%, and 1.5% under extensive solar radiation. Thermal performance of the collector at four volumetric flow rates of 1, 1.5, 2, and 2.5 Lit/min have been investigated according to ASHRAE standard 93-2010 (RA2014). According to the experimental data, the thermal efficiency of the collector improved by 5% to 11.6% when the nanofluid was applied. The maximum enhancement of the average Nusselt number of the nanofluid versus the base fluid at the volumetric flow rate of 1 Lit/min and the volumetric fraction of 1.5% was equal to 7.3%. Besides, nanofluid increased the pressure drop, and consequently, the pumping power slightly. Finally, considering both the impacts of heat transfer and pressure drop, performance evaluation criteria and overall efficiency for nanofluid have been analyzed. The results represented that in all volumetric fractions, the values of performance evaluation criteria and overall efficiency enhanced compared to the base fluid. This research provides researchers and engineers with important information to better understand the thermal and hydraulic parameters of the parabolic compound concentrator in the presence of nanofluid to improve its thermal performance. The results also highlight the potential of using SiO2 nanoparticles to improve the thermal efficiency of solar collectors despite their low thermal conductivity compared to other conventional nanoparticles.

SOIL HYDRAULIC PROPERTIES OF A CHROMIC LUVISOL IN KATUMANI, KENYA

<p><strong>Background:</strong> Soil hydraulic parameters in non-saturated conditions are crucial for explaining soil water dynamics in the field. It is therefore necessary to understand the link between soil water potential and hydraulic conductivity in the soil in order to estimate plant available water and hence simulate its movement within the soils. However, measurement of such hydraulic properties in the field and laboratory is somehow difficult, laborious and costly. <strong>Objective</strong>: To determine soil hydraulic properties of Ferro-chromic Luvisols in Katumani using the RETC code based on pedo-transfer functions; % sand, silt, clay and soil bulk density. <strong>Methodology:</strong> Undisturbed soil samples were collected from a profile pit at 0-15, 16-30, 31-45 and 46-60 cm depths using core rings for bulk densities and texture determination. Soil water retention curves and saturated hydraulic conductivities (Ksat) were estimated for all the samples using standard suction apparatus and the constant head method, respectively. The air entry suction (α) and pore size distribution (n) were generated using the RETC code. <strong>Results:</strong> The permanent wilting point and field capacity were at 0.081, 0.102, 0.107 and 0.121 and 0.188, 0.225, 0.241, 0.262 m<sup>3</sup>m<sup>-3 </sup>H<sub>2</sub>O, whilst its soil water diffusivity ranged from a low of 6.39, 6.94, 9.03 to a high of 12.5 cm<sup>2</sup>min<sup>-1</sup> in the 0-15, 16-30, 31-45 and 46-60 cm depth, respectively. Ksat values from RETC code ranged from 29 - 48 cm day<sup>-1</sup>, while the total and readily available water within the soil profile were 330.4 and 214.7 mm H<sub>2</sub>O, respectively. <strong>Implication:</strong> The air entry value (α) and pore size distribution (n) implied an almost even distribution from the top and subsequent horizons. The soils ‘field capacity was achieved at pF 2.0 whilst PWP was arbitrary indicated at pF 4.2 reducing the time it takes to calculate irrigation cycles based on the amount of water available to the crops. <strong>Conclusion:</strong> The data indicates that pedo-transfer functions; especially high bulk densities negatively impact on soil hydraulics conductivity.</p>

Measurement of the hydraulic properties of chalk using centrifuge permeameter; the study of chalk hydraulic properties under accelerated gravitational force

In this study, a geotechnical centrifuge has been used to study the unsaturated hydraulic properties of rock samples from the chalk aquifer, SE England. This method allows rapid measurement of hydraulic properties in a controlled environment, in contrast to previous studies on the chalk unsaturated zone, which required either an extended period (years) of data monitoring in the field or extended experimental periods (weeks) in the laboratory. Three types of specially built sensors were used to monitor water flow through chalk samples: a water pressure transducer to measure matric potential, frequency domain reflectometry probes to measure the volumetric water content and pressure transducers to measure the volume of water passing through the sample. Chalk samples were tested during wetting and draining processes to understand any hysteresis occurring during periodic recharge of the aquifer. Before undertaking physical tests of chalk samples in the centrifuge, a theoretical model of chalk hydraulic behaviour under centrifugal force was developed. This model was used to define and justify the instrumentation plan of the physical model and predict the shape of the soil moisture characteristic (SMC) curve and unsaturated hydraulic conductivity ( K u ) function. The results were then evaluated and compared with the experimental results. These results show that chalk samples can be successfully tested under centrifuge conditions and hydraulic properties can be measured, including soil moisture characteristic curves and hydraulic conductivity. Supplementary material: Calculation spread sheets are available at https://doi.org/10.17033/DATA.00000283

Sensitivity analysis of soil parameters in the Agricultural Production Systems sIMulator (APSIM)

Context The performance of process-based agroecosystem simulation models is highly sensitive to the numerous input parameters, many associated with high variability and uncertainty. Aims Our aims were to: (1) test the accuracy of the Agricultural Production Systems sIMulator (APSIM) model regarding the prediction of soil water storage and movement in a pasture system with a free draining pumice soil based on site-specific soil hydraulic properties; (2) identify sensitive soil hydraulic properties on model outputs; and (3) identify the influence of uncertainty in the description of soil properties on various model outputs. Methods We carried out a sensitivity analysis (SA) to identify sensitive soil hydraulic parameters. We set up APSIM to simulate a pasture system on a free-draining pumice soil in New Zealand. The model was first established with site-specific soil hydraulic properties and outputs were compared with measured soil moisture status and drainage. Next, the model’s sensitivity to the soil hydraulic parameters was assessed for various outputs linked to production and environmental outcomes. Key results Varying the various hydraulic parameters affected soil moisture status, but it had generally little effect on drainage, N leaching, and pasture production in this system. Conclusions The results suggest that for well-drained soils in a high precipitation zone with no water limitation, the model has low sensitivity to soil hydraulic parameters. Further analysis is required for different soils and for drier conditions. Implications For well-drained soils and under non-limiting water conditions the use of general data from databases, rather than site specific measurement of hydraulic properties is justified.

Comparison of hydraulic conductivity of rock matrix and fractured blocks of granitic rocks

Field measurements of hydraulic properties of the rock matrix and in low permeability hard rocks generally require highly accurate and sensitive technical equipment and special methods of measurement. Hydraulic conductivity of intact rocks is mostly measured in the laboratory conditions; field measurements are less common. The Czech geological survey developed equipment, which allows measurements of very low consumption of water during WPT (water pressure tests). This device enables to implement the same testing methodology for all sections of the borehole and subsequently compare the obtained results from low-permeability as well as more permeable sections. Hydraulic conductivity of eight different granitoids was studied in the Bohemian Massif in the Czech Republic. Mean values of hydraulic conductivity of fractured rock are on the order of 10-8 to 10-7 m·s-1, while hydraulic conductivity of rock matrix was most frequently on the order of 10–11 to10-12 m·s-1. The difference of values measured in laboratory and field is caused by scale effect. The significance of scale effect in rock matrix is determined mainly by the connectivity of a network of microfissures. Length and aperture of microfissures govern mainly the connectivity of fissure net in rock matrix. Coarse-grained granitoids have greater length and aperture of microfissures, higher connectivity and hydraulic conductivity, and the scale effect is less significant. The fracture network appearance and hydraulic conductivity of rock matrix is similar and characteristic for different types of granitoid rocks.

Quantifying the hydraulic properties of fractured rock masses along a borehole using composite geological indices: A case study in the mid and upper Choshui River Basin in Central Taiwan

Comprehensive information on vertical variations in hydraulic conductivity along a borehole is indispensable for characterizing the complexity of the hydraulic properties of fractured bedrock aquifers or for use as input data for groundwater modeling. This study presents a practical method for addressing various engineering concerns (e.g., project budget, completion time, manpower, and direct measurement of hydraulic properties from rock core specimens) when obtaining detailed and continuous hydraulic conductivity data along a borehole. Based on in-situ hydrogeological data collected from 26 boreholes located in the Choshui River Basin of Central Taiwan, eight individual and six composite geological indices were investigated to determine their correlations with the hydraulic conductivity of fractured rocks through bivariate analysis. The correlation analysis results indicate that all composite geological indices have higher correlations with the hydraulic conductivity than individual indices do. Moreover, the greater the number of individual geological indices integrated into one composite index, the higher the correlation. Based on the correlation results, quantification models for predicting the hydraulic conductivity using the composite geological indices were developed using regression analysis techniques. The performances of various statistical models were evaluated and compared. The regression analysis results for all six predictive models show that a power law relationship exists between each composite geological index and the hydraulic conductivity, and that the coefficient of determination ranges from 0.77 to 0.88. Therefore, the newly developed models can serve as an alternative for obtaining vertical hydraulic conductivity data when the budget for onsite hydraulic test is limited. • Models for predicting the hydraulic conductivity in boreholes are developed. • Eight individual and six composite geological indices are used. • All composite indices have high correlations with hydraulic conductivity. • The developed models are proven to be reliable.

Conditions of Hydraulic Heterogeneity under Which Bayesian Estimation is More Reliable

Natural heterogeneity of soil hydraulic properties is significant for the design and construction of geotechnical structures, and should be adequately characterized. Accurate measurements of hydraulic properties remain a difficult job and do not always work well for further design and analysis. Field hydraulic monitoring data reflects the overall slope performance and provide a more representative estimation of in-situ soil hydraulic properties for back analysis. The objective of this study is to explore the conditions under which monitoring data can provide reliable estimates of hydraulic parameters. Different distributions of soil heterogeneity generate a total number of 500 sets of synesthetic monitoring data. Bayesian inversion with the integration of Karhunen-Loève (K-L) and polynomial chaos expansion (PCE) is chosen to estimate the spatially varied saturated coefficient of permeability ks. The results show that the method is accurate and reliable, with less than 3% percentage error and 0.08 coefficient of variation (COV) around the monitoring points. There are two characteristics of the best-estimated fields. First, the ranges of ks for best-estimated fields are much narrower than the worst estimated fields. Second, when the larger ks values are distributed in the unsaturated zone of slope crest, it will lead to the best estimation. It is suggested that monitoring data can provide a reliable estimation of heterogeneous ks when the ratio of ground surface flux to ks in the unsaturated zone of slope crest is less than 1/150. Small values of ks in the slope crest result in the response of pressure head far from the responses of homogenous ks in the unsaturated zone. This complex response of the pressure head further causes the ill identification of ks by Bayesian estimation.

Active Layer Groundwater Flow: The Interrelated Effects of Stratigraphy, Thaw, and Topography

AbstractThe external drivers and internal controls of groundwater flow in the thawed “active layer” above permafrost are poorly constrained because they are dynamic and spatially variable. Understanding these controls is critical because groundwater can supply solutes such as dissolved organic matter to surface water bodies. We calculated steady‐state three‐dimensional suprapermafrost groundwater flow through the active layer using measurements of aquifer geometry, saturated thickness, and hydraulic properties collected from two major landscape types over time within a first‐order Arctic watershed. The depth position and thickness of the saturated zone is the dominant control of groundwater flow variability between sites and during different times of year. The effect of water table depth on groundwater flow dwarfs the effect of thaw depth. In landscapes with low land‐surface slopes (2–4%), a combination of higher water tables and thicker, permeable peat deposits cause relatively constant groundwater flows between the early and late thawed seasons. Landscapes with larger land‐surface slopes (4–10%) have both deeper water tables and thinner peat deposits; here the commonly observed permeability decrease with depth is more pronounced than in flatter areas, and groundwater flows decrease significantly between early and late summer as the water table drops. Groundwater flows are also affected by microtopographic features that retain groundwater that could otherwise be released as the active layer deepens. The dominant sources of groundwater, and thus dissolved organic matter, are likely wet, flatter regions with thick organic layers. This finding informs fluid flow and solute transport dynamics for the present and future Arctic.

Soil Physical, Hydraulic, and Thermal Properties in Interior Alaska, USA: Implications for Hydrologic Response to Thawing Permafrost Conditions

AbstractBoreal forest regions are a focal point for investigations of coupled water and biogeochemical fluxes in response to wildfire disturbances, climate warming, and permafrost thaw. Soil hydraulic, physical, and thermal property measurements for mineral soils in permafrost regions are limited, despite substantial influences on cryohydrogeologic model results. This work expands mineral soil property quantification in cold regions through soil characterization from the discontinuous permafrost zone of interior Alaska, USA. Values extend beyond the range of prior measurement magnitudes in analogous regions, highlighting the importance of this data set. Rocky and silty upland soil landscape classifications and wildfire disturbance provided guiding frameworks for the sampling and analysis for potential implications for the hydrologic response to thawing permafrost. Bulk density (ρb), soil organic matter, soil‐particle size distributions (sand, silt, and gravel fractions), and soil hydraulic properties of van Genuchten parameters alpha and N had moderate evidence of differences between silty and rocky classifications. Burned and unburned sites had only moderate evidence of differences for silt fraction. Field‐saturated hydraulic conductivity (Kfs) was more variable at burned sites compared to unburned sites, which corresponded to observations of greater rooting depths at burned sites and observations of root paths in soil cores for Kfs measurement. Soil thermal properties suggested that gravel content may reduce the accuracy of commonly used estimation methods for thermal conductivity. This work provides soil parameter constraints necessary for hypothesis testing and site‐specific prediction with cryohydrogeologic models to examine controls on active layer and permafrost dynamics in upland boreal forests.

Field verification tests of the newly developed flow cone tool—In-situ measurements of hydraulic soil properties

Hydraulic soil properties, and in particular the hydraulic conductivity, is important in a number of geotechnical design cases. However, attention is often drawn towards the method of analysis rather than the quality and validity of the hydraulic properties used as input. Intact samples of sand or silt are difficult or impossible to obtain, and prediction of hydraulic soil properties from available in-situ tools represents a challenge. With the aim of quick and reliable in-situ measurements of hydraulic properties of sands and silts, NGI developed a prototype tool referred to as the flow cone. The tool combines the widely used cone penetration test with an add-on pumping system that allows water to flow into the surrounding sediments during cone penetration and stand-still. By measuring flow rates and pore water pressures, the hydraulic properties of the surrounding soil can be estimated. The flow cone prototype was tested at the NGTS sand site (Oysand, Norway) in September 2018. The aim of this paper is to present the measured and interpreted results. The results are evaluated within the context of available data from the sand site including cone penetration tests, in-situ falling head tests, grain size distributions and constant head tests from laboratory. Recommendations for further work and potential applications in engineering practice are discussed.

Factorial kriging analysis leverages soil physical properties and exhaustive data to predict distinguished zones of hydraulic properties

Measurement of unsaturated hydraulic properties of soil is a time-consuming endeavor which limits the scale of studies. A stratified sampling scheme could enable more efficient use of samples but some information about the strata is needed a priori. The aim of this study is to define zones of soil hydraulic properties using remotely sensed and soil physical inputs. Samples were collected from 50 locations at 4 depth intervals in a 20.8 ha field located along the margin of the Venice Lagoon, Italy, and characterized by paleo-channel structures and highly heterogeneous soils. Water retention curves (WRC) and unsaturated hydraulic conductivity curves (UHC) were determined via inversion of measurements taken in the lab using the Wind method. Factorial kriging analysis (FKA) was applied separately to hydraulic parameters and soil physical properties and the 4 depths treated as independent samples. The mapped principal components (PCs) were used in a fuzzy-c means algorithm to define zones of like properties. To examine the physical significance of these zones, curve parameters and hydraulic curves were investigated. Zonation was able to distinguish between θs (saturated water content), n (shape parameter) and α (inverse of air entry), while θr (residual water content) and Ks (saturated conductivity) were not statistically different between the groups. For curve comparisons, WRCs were found to be significantly different between zones at all tensions while effective saturation curves (Se) differ for the majority of tensions (except at 28 cm), and UHCs did not differ. The spatial relevance of the zones was examined by overlaying hydraulic zones with zones defined using the FKA and fuzzy-c means approach from soil physical properties such as texture and bulk density. The hydraulic zones overlaid the physical property zones with an areal accuracy ranging from 46.66% to 92.41%. The similarity between these zone sets suggests that there is a potential to predict hydraulic zones from zones defined from soil physical properties. This work illustrates the potential to incorporate geospatial statistics in a stratified sampling scheme for hydraulic properties.

Manipulating rainfall to study symptom expression of <i>Botrytis cinerea</i> infection in wine grapes

Manipulating rainfall to study symptom expression of <i>Botrytis cinerea</i> infection in wine grapes

Frictional stability‐permeability relationships for fractures in shales

AbstractThere is wide concern that fluid injection in the subsurface, such as for the stimulation of shale reservoirs or for geological CO2 sequestration (GCS), has the potential to induce seismicity that may change reservoir permeability due to fault slip. However, the impact of induced seismicity on fracture permeability evolution remains unclear due to the spectrum of modes of fault reactivation (e.g., stable versus unstable). As seismicity is controlled by the frictional response of fractures, we explore friction‐stability‐permeability relationships through the concurrent measurement of frictional and hydraulic properties of artificial fractures in Green River shale (GRS) and Opalinus shale (OPS). We observe that carbonate‐rich GRS shows higher frictional strength but weak neutral frictional stability. The GRS fracture permeability declines during shearing while an increased sliding velocity reduces the rate of permeability decline. By comparison, the phyllosilicate‐rich OPS has lower friction and strong stability while the fracture permeability is reduced due to the swelling behavior that dominates over the shearing induced permeability reduction. Hence, we conclude that the friction‐stability‐permeability relationship of a fracture is largely controlled by mineral composition and that shale mineral compositions with strong frictional stability may be particularly subject to permanent permeability reduction during fluid infiltration.

Measurement of hydraulic properties of bentonite cake formation deposited on base soil medium

Bentonite cake and filter cake on the surface of porous media result from the filtration of stabilizing slurry into the adjacent porous formation. This paper provides measurements of hydraulic conductivities of bentonite cake formed on Korean standard sand under various pressure levels. Two types of bentonite (Tixoton and Bentonil GTC4) were used to create the slurries with three different concentrations (4, 6, and 8% by weight). An estimation of the hydraulic conductivity of the bentonite cake based on the filtration theory was carried out. The range of hydraulic conductivities of the bentonite cake was from 2.1×10−11m/s to 5.7×10−10m/s. The hydraulic conductivity of the bentonite cake deposited on Korean standard sand were compared with that of the bentonite cake deposited on filter paper to show the effect of the filter medium. The slurry concentration of 6% seems to be a value that most stimulates the effect of the filter medium on the permeability of the Bentonil GTC4 bentonite cake. In addition, a simple approach was developed to characterize the hydraulic properties of the filter cake, which has usually been confused with the bentonite cake in recently published literature.

In situ Measurement of Hydraulic Properties of the Fractured Zone of Coal Mines

A review of the literature on the water inrush of underground openings under a condition of water flow reveals that insufficient attention has been devoted to the measurement of hydraulic properties of fractured zones, such as faults and zones of plastic damage generated by excavation or mining. A conceptual sketch of the fractured zone is presented in Fig. 1. The zone of floor damage is a zone of deformation and failure of the floor rock formation resulting from mining. In particular, groundwater inrush from aquifers underlying mining coal seams are usually induced when uncovering the fractured zone, which is a geological structure extensively distributed in the coalfields of eastern China (Bai et al. 2013). Moreover, the Ordovician limestone underlying the coal seams of coalfields in eastern China forms a confined karst aquifer containing an abundant supply of water and having very high water pressure (Zhang 2005). In this regard, the hydraulic properties in the fractured zone are important to deep underground engineering, particularly when an aquifer surrounds an excavation, for the reason that most water inrush accidents relate to the fractured zone (Fahimifar and Zareifard 2009; Qiao et al. 2013). Laboratory tests are commonly conducted to determine the hydraulic properties of soft soils and rocks (e.g., Ponziani et al. 2011; Bo et al. 2014). There has been an increasing emergence of in situ testing methods as alternatives to laboratory testing methods for assessing the hydraulic characteristic of the fractured zone in civil engineering (Bo et al. 2014); e.g., the water injection test (WIT) is conducted to determine the hydraulic characteristics of the fractured zone (Mukai and Fujimori 2007; Kitagawa et al. 2007). However, laboratory tests of the fractured zone are subject to uncertainties due primarily to disturbances that cause an important difference in hydraulic conductivity between the in situ and laboratory test methods (Bo et al. 2014). In situ tests are particularly useful in the determination of the in situ hydraulic conductivity of the fractured zone. In situ tests have an advantage over other methods in that they effectively measure the in situ hydraulic conductivity. The key objective of this technical note is to report the measured hydraulic properties in the fractured zone under mutative water pressures by conducting an in situ WIT.

Prevention of Discoloration Events in Water Distribution Systems

Mathematical modeling and simulation techniques represent powerful tools for optimizing the operation of drinking water supply networks. Water quality in the distribution systems is affected by the hydraulic regime in the network (Vreeburg, 2007). An incidental re-suspension of accumulated loose particles is the main cause of discoloration events in the network (Vreeburg, 2010). This article describes two technical tools that are being developed to help water utilities create and maintain programs for preventing the occurrence of discoloration events in their water distribution systems. The first of the two directly applicable tools is a portable measuring device that enables continuous measurement of hydraulic properties and water discoloration in the network. The other tool is a software application ADAM, which uses a non-data-hungry methodology based on a risk analysis approach and utilizes the author's previous experience with mathematical modeling of various water-supply networks. The probability of the presence of sediment accumulation in each pipe section in the network is estimated. Problems relating to uncertainty and poor input data quality are solved by the application of the FMEA/FMECA technique (Tuhovčák, Ručka, 2009). The analysis is performed using ADAM, the newly developed simulation software for hydraulic analysis of water supply networks. The tools presented in this paper have been developed under the framework of “Tools for prevention of water discoloration in water mains”, the current national research project of the Technology Agency of the Czech Republic (registration number TA02020604), a brief outline of which is also presented in this paper.