Real-time pore water pressure measurements have been made automatically and continuously with tensiometer (GT), Thermal Conductivity (TC) and capacitance (MP) sensors in laboratory compacted clay columns. Although GT, TC and MP sensors have been commonly used in many applications, there has rarely been any attempt to compare the measurements made by the different sensors or to evaluate their long-term performance, especially for application in compacted clay in a high salinity environment and under a high hydraulic gradient. In this study, GT, TC and MP sensors were calibrated and subsequently installed at various elevations in 303 mm diameter by 300 mm high compacted clay columns subjected to wetting by a 100 kPa saline water pressure, followed by subsequent drying. The calibration and measurement results showed that the GT sensors allowed measurements not only of negative pore water pressure, but also of positive pore water pressure. While the GT sensors allowed the measurement of pore water pressure down to -80 kPa, the TC and MP sensors were able to measure much higher negative pore water pressures. The TC and MP sensors were, however, found to have large sensor-to-sensor variations, hysteretic behaviour upon drying and wetting, and slow equilibration times. Unlike the GT and TC sensors, the long-term performance of the MP sensors was found to be affected by the salinity of the compacted clay.
{"title":"Comparison of tensiometer, thermal conductivity and capacitance sensor measurements of pore water pressure in compacted clay columns","authors":"I. Indrawan, David J. Williams, A. Scheuermann","doi":"10.1201/B17034-232","DOIUrl":"https://doi.org/10.1201/B17034-232","url":null,"abstract":"Real-time pore water pressure measurements have been made automatically and continuously with tensiometer (GT), Thermal Conductivity (TC) and capacitance (MP) sensors in laboratory compacted clay columns. Although GT, TC and MP sensors have been commonly used in many applications, there has rarely been any attempt to compare the measurements made by the different sensors or to evaluate their long-term performance, especially for application in compacted clay in a high salinity environment and under a high hydraulic gradient. In this study, GT, TC and MP sensors were calibrated and subsequently installed at various elevations in 303 mm diameter by 300 mm high compacted clay columns subjected to wetting by a 100 kPa saline water pressure, followed by subsequent drying. The calibration and measurement results showed that the GT sensors allowed measurements not only of negative pore water pressure, but also of positive pore water pressure. While the GT sensors allowed the measurement of pore water pressure down to -80 kPa, the TC and MP sensors were able to measure much higher negative pore water pressures. The TC and MP sensors were, however, found to have large sensor-to-sensor variations, hysteretic behaviour upon drying and wetting, and slow equilibration times. Unlike the GT and TC sensors, the long-term performance of the MP sensors was found to be affected by the salinity of the compacted clay.","PeriodicalId":294644,"journal":{"name":"Unsaturated Soils: Research & Applications","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124699806","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2020-09-23DOI: 10.1201/9781003070580-38
T. Ishikawa, T. Tokoro, D. Nakamura, S. Yamashita
{"title":"Evaluation on air-permeability of unsaturated soils subjected to freeze-thaw action","authors":"T. Ishikawa, T. Tokoro, D. Nakamura, S. Yamashita","doi":"10.1201/9781003070580-38","DOIUrl":"https://doi.org/10.1201/9781003070580-38","url":null,"abstract":"","PeriodicalId":294644,"journal":{"name":"Unsaturated Soils: Research & Applications","volume":"164 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114924256","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Y. Ma, G. Yan, A. Scheuermann, Ling Li, S. Galindo‐Torres, D. Bringemeier
The coal seam gas and underground coal gasification industry has caused concerns with the risk of potential groundwater contamination. Gases leaked from coal seams are thought to be a source of groundwater pollution. However, the basic principles and controlling parameters for gases seepage from deep ground formations to the surface are not fully understood. Microbubble transport, as a possible mechanism for gases transport in the subsurface, is investigated here through a laboratory-scale experiment. Microbubbles were generated from a bubble diffuser and released into a 2D artificial transparent porous medium. The point source of bubble injection was used to simulate the release of gases from geological faults/fractures. The medium's transparency enabled a clear visualization of the bubble pathways. Images captured by cameras were used to facilitate analyses on the bubble transport behavior affected by advection and dispersion.
{"title":"Discrete microbubbles flow in transparent porous media","authors":"Y. Ma, G. Yan, A. Scheuermann, Ling Li, S. Galindo‐Torres, D. Bringemeier","doi":"10.1201/B17034-177","DOIUrl":"https://doi.org/10.1201/B17034-177","url":null,"abstract":"The coal seam gas and underground coal gasification industry has caused concerns with the risk of potential groundwater contamination. Gases leaked from coal seams are thought to be a source of groundwater pollution. However, the basic principles and controlling parameters for gases seepage from deep ground formations to the surface are not fully understood. Microbubble transport, as a possible mechanism for gases transport in the subsurface, is investigated here through a laboratory-scale experiment. Microbubbles were generated from a bubble diffuser and released into a 2D artificial transparent porous medium. The point source of bubble injection was used to simulate the release of gases from geological faults/fractures. The medium's transparency enabled a clear visualization of the bubble pathways. Images captured by cameras were used to facilitate analyses on the bubble transport behavior affected by advection and dispersion.","PeriodicalId":294644,"journal":{"name":"Unsaturated Soils: Research & Applications","volume":"115 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132731678","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
C. Gonzales, T. Baumgartl, A. Scheuermann, A. Soliman
A soil cover isolates possibly acid-forming mine wastes from atmospheric interaction and thereby mitigate acid rock drainage. The availability of suitable soil cover materials is a problem, especially in arid/semi-arid environments where weathering rates are low. Moreover, these regions may be affected by monsoonal weather patterns adding a further challenge to soil cover design. This paper discusses an inclined soil cover configuration that constitutes waste rocks and blended tailings. The materials' hydrological properties were determined from in situ measurements and laboratory experiments. Preliminary results of the numerical modeling of its soil moisture profile indicated that a rocky substrate approaches near-saturated conditions during rainfall events but the use of blended tailings as hydraulic barrier may enhance lateral drainage, thereby reducing deep drainage. Consequently, the description of the transient soil moisture flow of this soil cover configuration will be validated by field data sets during the wet season.
{"title":"Soil moisture profile of a water-shedding cover design in central Queensland","authors":"C. Gonzales, T. Baumgartl, A. Scheuermann, A. Soliman","doi":"10.1201/B17034-205","DOIUrl":"https://doi.org/10.1201/B17034-205","url":null,"abstract":"A soil cover isolates possibly acid-forming mine wastes from atmospheric interaction and thereby mitigate acid rock drainage. The availability of suitable soil cover materials is a problem, especially in arid/semi-arid environments where weathering rates are low. Moreover, these regions may be affected by monsoonal weather patterns adding a further challenge to soil cover design. This paper discusses an inclined soil cover configuration that constitutes waste rocks and blended tailings. The materials' hydrological properties were determined from in situ measurements and laboratory experiments. Preliminary results of the numerical modeling of its soil moisture profile indicated that a rocky substrate approaches near-saturated conditions during rainfall events but the use of blended tailings as hydraulic barrier may enhance lateral drainage, thereby reducing deep drainage. Consequently, the description of the transient soil moisture flow of this soil cover configuration will be validated by field data sets during the wet season.","PeriodicalId":294644,"journal":{"name":"Unsaturated Soils: Research & Applications","volume":"37 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122316277","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Modeling field load tests in lateritic unsaturated soil","authors":"R. Rodrigues, G. B. Georgetti, O. Vilar","doi":"10.1201/B17034-218","DOIUrl":"https://doi.org/10.1201/B17034-218","url":null,"abstract":"","PeriodicalId":294644,"journal":{"name":"Unsaturated Soils: Research & Applications","volume":"64 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123769106","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Assessment of soil texture influence on nitrates leachability in unsaturated soils","authors":"I. Popescu, G. Déak, G. Dorobantu","doi":"10.1201/b17034-163","DOIUrl":"https://doi.org/10.1201/b17034-163","url":null,"abstract":"","PeriodicalId":294644,"journal":{"name":"Unsaturated Soils: Research & Applications","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128461173","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The conventional laboratory compression testing of geo-materials is carried out in a water bath to create near-saturated materials. The aim of this is reduce the materials to two phases: solids and water, which are both essentially incompressible. This makes the results of the testing easier to interpret, since if highly compressible air were present the pore volume, degree of saturation and hence matric suction would change continuously during compression. Testing under saturated conditions will also generally represent a worst case situation, inducing greater compression than testing under unsaturated conditions. In addition, the limited scale of conventional laboratory test apparatus restricts the maximum particle size that can be tested. This necessitates that coarse-grained materials, such as coal mine spoil, be scalped to enable laboratory compression testing. Australian coal mine spoil materials selected to cover a range from essentially uncemented rocks to cemented sandstones, were prepared loose in a 150 mm diameter by 150 mm high, 10 MPa oedometer, and subjected to incremental compression under dry (assampled moisture content) and wet (in a water bath) conditions. The dry state represents the as-dumped condition, while the wet state represents the ultimate wetting-up of the material in the spoil pile due to rainfall infiltration and groundwater inflow. In the dry state, the air in the voids of the specimens is free to compress, leading to an increase in the degree of saturation and a decrease in the matric suction. The initial and final moisture contents and densities of the specimens were recorded. In the paper, the results for uncemented and cemented coal mine spoil materials tested under dry and wet conditions are presented and compared with data from the literature.
{"title":"Laboratory compression of scalped coal mine spoil materials tested under dry and wet conditions","authors":"David J. Williams, A. Kho","doi":"10.1201/B17034-227","DOIUrl":"https://doi.org/10.1201/B17034-227","url":null,"abstract":"The conventional laboratory compression testing of geo-materials is carried out in a water bath to create near-saturated materials. The aim of this is reduce the materials to two phases: solids and water, which are both essentially incompressible. This makes the results of the testing easier to interpret, since if highly compressible air were present the pore volume, degree of saturation and hence matric suction would change continuously during compression. Testing under saturated conditions will also generally represent a worst case situation, inducing greater compression than testing under unsaturated conditions. In addition, the limited scale of conventional laboratory test apparatus restricts the maximum particle size that can be tested. This necessitates that coarse-grained materials, such as coal mine spoil, be scalped to enable laboratory compression testing. Australian coal mine spoil materials selected to cover a range from essentially uncemented rocks to cemented sandstones, were prepared loose in a 150 mm diameter by 150 mm high, 10 MPa oedometer, and subjected to incremental compression under dry (assampled moisture content) and wet (in a water bath) conditions. The dry state represents the as-dumped condition, while the wet state represents the ultimate wetting-up of the material in the spoil pile due to rainfall infiltration and groundwater inflow. In the dry state, the air in the voids of the specimens is free to compress, leading to an increase in the degree of saturation and a decrease in the matric suction. The initial and final moisture contents and densities of the specimens were recorded. In the paper, the results for uncemented and cemented coal mine spoil materials tested under dry and wet conditions are presented and compared with data from the literature.","PeriodicalId":294644,"journal":{"name":"Unsaturated Soils: Research & Applications","volume":"203 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124548184","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Strength/volume change behaviour of compacted silty sand using a novel double-walled suction-controlled triaxial system","authors":"U. Patil, A. Puppala, L. Hoyos","doi":"10.1201/b17034-252","DOIUrl":"https://doi.org/10.1201/b17034-252","url":null,"abstract":"","PeriodicalId":294644,"journal":{"name":"Unsaturated Soils: Research & Applications","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127659088","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Scheuermann, S. Galindo‐Torres, D. Pedroso, David J. Williams, Ling Li
The Soil Water Characteristic Curve (SWCC) is the most important information needed to analyse, describe and compute the hydraulic and mechanic behavior of unsaturated soils. Using conventional laboratory testing methods, usually the SWCC is measured for equilibrium conditions by controlling either the pressure in the air or water phase. Already since several years it is well known that during transient processes dynamic effects are existing leading to an overshoot of the SWCC during drainage and an undershoot during imbibition. Against this background, the validity of the conventionally measured SWCC for describing transient processes is at least to be questioned. Measurements conducted during transient multi-step-inflow- And -outflow-experiments have revealed another manifestation of dynamic effects in form of accumulation of water with repeating imbibition and drainage cycles. These observations were possible only by simultaneous measurements of water content profiles using a novel measurement method based on Time Domain Reflectometry and local pore water pressure measurements using micro tensiometers. Calculations with a Lattice Boltzmann Method based code confirms the existence of this new kind of dynamic effects for unsaturated soils.
{"title":"Dynamics of water movements with reversals in unsaturated soils","authors":"A. Scheuermann, S. Galindo‐Torres, D. Pedroso, David J. Williams, Ling Li","doi":"10.1201/B17034-153","DOIUrl":"https://doi.org/10.1201/B17034-153","url":null,"abstract":"The Soil Water Characteristic Curve (SWCC) is the most important information needed to analyse, describe and compute the hydraulic and mechanic behavior of unsaturated soils. Using conventional laboratory testing methods, usually the SWCC is measured for equilibrium conditions by controlling either the pressure in the air or water phase. Already since several years it is well known that during transient processes dynamic effects are existing leading to an overshoot of the SWCC during drainage and an undershoot during imbibition. Against this background, the validity of the conventionally measured SWCC for describing transient processes is at least to be questioned. Measurements conducted during transient multi-step-inflow- And -outflow-experiments have revealed another manifestation of dynamic effects in form of accumulation of water with repeating imbibition and drainage cycles. These observations were possible only by simultaneous measurements of water content profiles using a novel measurement method based on Time Domain Reflectometry and local pore water pressure measurements using micro tensiometers. Calculations with a Lattice Boltzmann Method based code confirms the existence of this new kind of dynamic effects for unsaturated soils.","PeriodicalId":294644,"journal":{"name":"Unsaturated Soils: Research & Applications","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123919406","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Busse, A. Scheurmann, S. Galindo‐Torres, D. Bringemeier, Ling Li
Micropores and the cleat network of coal provide the principal source of permeability for fluid flow. The flow behavior of fluids under varying total stress and different environmental conditions are examined in field and laboratory experiments. Based on the measurements a multi-scale, two-phase flow model to describe and quantify the various effects of the mine operation will be developed with a focus on the challenge of extrapolating point based results from a small scale to a regional scale.
{"title":"In-situ and laboratory measurements of coal matrix and cleat permeability","authors":"J. Busse, A. Scheurmann, S. Galindo‐Torres, D. Bringemeier, Ling Li","doi":"10.1201/B17034-208","DOIUrl":"https://doi.org/10.1201/B17034-208","url":null,"abstract":"Micropores and the cleat network of coal provide the principal source of permeability for fluid flow. The flow behavior of fluids under varying total stress and different environmental conditions are examined in field and laboratory experiments. Based on the measurements a multi-scale, two-phase flow model to describe and quantify the various effects of the mine operation will be developed with a focus on the challenge of extrapolating point based results from a small scale to a regional scale.","PeriodicalId":294644,"journal":{"name":"Unsaturated Soils: Research & Applications","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-09-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125394040","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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