Kevin M. Briggs, Yuderka Trinidad González, William Powrie, Simon Butler, Nick Sartain
The empirical interpretation of cone penetration test (CPT) cone factors ( N k ) can be subject to considerable variability for clays derived from weathered mudstones, leading to significant deviations in the estimation of undrained shear strength ( S u ). This paper presents a comparison of triaxial and CPT data from a site investigation in clays derived from weathered mudstones in central England. Corrected cone factors ( N kt,UU ) were derived from a one-to-one comparison of 94 pairs of unconsolidated, undrained triaxial and CPT data from equivalent depths. The performance of the cone factors was evaluated using a training set (75 pairs) and a test set (19 pairs). A parametric study was used to explore the variability of N kt,UU , quantified using the coefficient of variation (COV Nkt,UU ), for varied separation distance thresholds ( D s ) between individual triaxial and CPT data. The absolute deviation between the laboratory shear strength ( S u(Lab) ) and that predicted from CPT profiles (S u(CPT) ) was not sensitive to N kt,UU values in the range 25 < N kt,UU < 31. The parametric study showed that D s could be increased from 50 to 250 m, to include more data pairs for estimates of N kt,UU , without substantially increasing COV Nkt,UU .
{"title":"Quantifying CPT cone factors in clays derived from weathered mudstone","authors":"Kevin M. Briggs, Yuderka Trinidad González, William Powrie, Simon Butler, Nick Sartain","doi":"10.1144/qjegh2023-014","DOIUrl":"https://doi.org/10.1144/qjegh2023-014","url":null,"abstract":"The empirical interpretation of cone penetration test (CPT) cone factors ( N k ) can be subject to considerable variability for clays derived from weathered mudstones, leading to significant deviations in the estimation of undrained shear strength ( S u ). This paper presents a comparison of triaxial and CPT data from a site investigation in clays derived from weathered mudstones in central England. Corrected cone factors ( N kt,UU ) were derived from a one-to-one comparison of 94 pairs of unconsolidated, undrained triaxial and CPT data from equivalent depths. The performance of the cone factors was evaluated using a training set (75 pairs) and a test set (19 pairs). A parametric study was used to explore the variability of N kt,UU , quantified using the coefficient of variation (COV Nkt,UU ), for varied separation distance thresholds ( D s ) between individual triaxial and CPT data. The absolute deviation between the laboratory shear strength ( S u(Lab) ) and that predicted from CPT profiles (S u(CPT) ) was not sensitive to N kt,UU values in the range 25 < N kt,UU < 31. The parametric study showed that D s could be increased from 50 to 250 m, to include more data pairs for estimates of N kt,UU , without substantially increasing COV Nkt,UU .","PeriodicalId":20937,"journal":{"name":"Quarterly Journal of Engineering Geology and Hydrogeology","volume":"76 5","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135088524","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Kang Zhao, Qizheng Huang, Jun Wu, Yajing Yan, Jian Yang, Fujin Ning, Xiangqing Tian, Lang Liu, Yongbo Ji
To reduce the economic cost of backfilling a mine, layers of cemented materials with different ash sand ratios are often used to backfill the void. In this study, we explored the damage evolution mechanism from the energy consumption point of view for backfill and rock combination with different ash sand ratios, and introduced the strength dissipation rate, damage value parameter and elastic strain energy rate to achieve the definition of damage in the specimens, as well as the characterization of the energy accumulation effect. In addition, the layered backfilling of the assemblage was simulated using FLAC 3D software. The results show that: (1) the elastic strain energy rate can reflect the accumulation ability of the strain energy of the specimen; the larger the strain energy rate, the stronger the accumulation ability; (2) the damage evolution of the backfill–backfill combination is divided into stages: initial damage repair stage, damage stable development stage, damage accelerated development stage and residual damage stage; and (3) the top layer with an ash/sand ratio of 1:4, the middle layer with an ash/sand ratio of 1:8 and the bottom layer with an ash/sand ratio of 1:10 is the optimal backfilling scheme. This study can provide a theoretical reference for the backfilling of a hollow area.
{"title":"Analysis of energy dissipation characteristics and numerical simulation of surrounding rock control for backfill combinations with different ash-sand ratios","authors":"Kang Zhao, Qizheng Huang, Jun Wu, Yajing Yan, Jian Yang, Fujin Ning, Xiangqing Tian, Lang Liu, Yongbo Ji","doi":"10.1144/qjegh2023-057","DOIUrl":"https://doi.org/10.1144/qjegh2023-057","url":null,"abstract":"To reduce the economic cost of backfilling a mine, layers of cemented materials with different ash sand ratios are often used to backfill the void. In this study, we explored the damage evolution mechanism from the energy consumption point of view for backfill and rock combination with different ash sand ratios, and introduced the strength dissipation rate, damage value parameter and elastic strain energy rate to achieve the definition of damage in the specimens, as well as the characterization of the energy accumulation effect. In addition, the layered backfilling of the assemblage was simulated using FLAC 3D software. The results show that: (1) the elastic strain energy rate can reflect the accumulation ability of the strain energy of the specimen; the larger the strain energy rate, the stronger the accumulation ability; (2) the damage evolution of the backfill–backfill combination is divided into stages: initial damage repair stage, damage stable development stage, damage accelerated development stage and residual damage stage; and (3) the top layer with an ash/sand ratio of 1:4, the middle layer with an ash/sand ratio of 1:8 and the bottom layer with an ash/sand ratio of 1:10 is the optimal backfilling scheme. This study can provide a theoretical reference for the backfilling of a hollow area.","PeriodicalId":20937,"journal":{"name":"Quarterly Journal of Engineering Geology and Hydrogeology","volume":"63 10","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135092444","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Kang Zhao, Jiale Chen, Jun Wu, Yajing Yan, Qizheng Huang, Qiang Nie, Weiling Xiao
Weathering of granite leads to weakening of its crushing and mechanical properties, as well as changes in mineral composition. In order to investigate the correlation between the effects of weathering on granite and the characterization of the pore structure at the micro- and fine-scale, in this paper the pore structure of weathered granite is tested by the NMR technique. The pore distribution characteristics of weathered granite were explored in conjunction with T 2 spectral relaxation time and fractal theory. The microstructure of weathering-prone granite was monitored using scanning electron microscopy equipment. The results show that the pores can be classified into the three categories of small, medium and large pores based on their pore size distribution characteristics. Weathered granite has fractal features in the mesopores and macropores. Compared with unweathered granite, weathered granite has significantly more small pore throats and fewer medium and large pore throats, which expand into microfissures and micropores under conditions of weathering. The microstructure of weathered granite is mainly flaky and shell-like, with good connectivity, resulting in the poor overall structure of weathered granite.
{"title":"Cross-scale study of pore fractal characteristics and pore structure of weathered granite","authors":"Kang Zhao, Jiale Chen, Jun Wu, Yajing Yan, Qizheng Huang, Qiang Nie, Weiling Xiao","doi":"10.1144/qjegh2023-075","DOIUrl":"https://doi.org/10.1144/qjegh2023-075","url":null,"abstract":"Weathering of granite leads to weakening of its crushing and mechanical properties, as well as changes in mineral composition. In order to investigate the correlation between the effects of weathering on granite and the characterization of the pore structure at the micro- and fine-scale, in this paper the pore structure of weathered granite is tested by the NMR technique. The pore distribution characteristics of weathered granite were explored in conjunction with T 2 spectral relaxation time and fractal theory. The microstructure of weathering-prone granite was monitored using scanning electron microscopy equipment. The results show that the pores can be classified into the three categories of small, medium and large pores based on their pore size distribution characteristics. Weathered granite has fractal features in the mesopores and macropores. Compared with unweathered granite, weathered granite has significantly more small pore throats and fewer medium and large pore throats, which expand into microfissures and micropores under conditions of weathering. The microstructure of weathered granite is mainly flaky and shell-like, with good connectivity, resulting in the poor overall structure of weathered granite.","PeriodicalId":20937,"journal":{"name":"Quarterly Journal of Engineering Geology and Hydrogeology","volume":" 24","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135293553","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
There are many site investigation projects used for the urban planning of a city. They are archived in hard copy or scanned in image files stored on computers. In this study, geological, geotechnical and geophysical data obtained from different site investigation projects in the Acıpayam district were evaluated in the same coordinate system using a geological and geotechnical information system (GEO-GIS) computer program. The Acıpayam GEO-GIS database includes field tests in 82 boreholes, 85 observation pits, laboratory test results of soil samples, 99 seismic refraction measurements and 70 microtremor measurements. Required information from the database can be displayed at its spatial coordinates on a base map and new maps can also be drawn using the GEO-GIS database system. Resultant maps drawn using the Acıpayam GEO-GIS database show that in the northern and eastern parts of the Acıpayam district, where the Oğuz, Kırca, Yassıhöyük, Apa, Ovayurt, Karahüyük, Ucarı and Gedikli villages are located, weak soil layers exist. This means that some damage may be caused to adobe and masonry buildings in the villages during shaking associated with strong earthquakes, as observed after the 5.5 (M w ) earthquake that occurred on 20 March 2019. The Acıpayam GEO-GIS database system is a useful tool for engineers and planners that can assist in drawing GIS-produced maps for geotechnical evaluations of the basin. These maps can be used in decision-making projects for urban planning. Thematic collection: This article is part of the Leading to Innovative Engineering Geology Practices collection available at: https://www.lyellcollection.org/topic/collections/leading-to-innovative-engineering-geology-practices
一个城市的城市规划中有许多现场调查项目。它们以硬拷贝的形式存档，或者扫描成图像文件存储在计算机中。在本研究中，利用地质与岩土信息系统(GEO-GIS)计算机程序，在同一坐标系下对Acıpayam地区不同站点调查项目获得的地质、岩土和地球物理数据进行了评价。Acıpayam GEO-GIS数据库包括82个钻孔的现场试验、85个观测坑、土壤样品的实验室试验结果、99次地震折射测量和70次微震测量。数据库所需的资料可以在底图上以其空间坐标显示，也可以利用地理信息系统数据库系统绘制新的地图。利用Acıpayam GEO-GIS数据库绘制的结果图显示，在Acıpayam区的北部和东部，Oğuz、Kırca、Yassıhöyük、Apa、Ovayurt、karah y k、ucaryi和Gedikli村所在的地方，存在薄弱的土壤层。这意味着，在2019年3月20日发生的5.5级地震后观测到的强震期间，村庄的土坯和砖石建筑可能会受到一定程度的破坏。Acıpayam GEO-GIS数据库系统是工程师和规划人员的一个有用工具，可以协助绘制地理信息系统制作的地图，以便对盆地进行地质技术评价。这些地图可用于城市规划的决策项目。专题合集:本文是Leading to Innovative Engineering Geology Practices合集的一部分，可在https://www.lyellcollection.org/topic/collections/leading-to-innovative-engineering-geology-practices找到
{"title":"A Geological and Geotechnical Information System (GEO-GIS) for urban planning and its application to the Acıpayam Basin (Denizli-Turkey), with some observations from Mw 5.5 earthquake on 20 March, 2019","authors":"Halil Kumsar, Tuğba Sarayköylü","doi":"10.1144/qjegh2022-065","DOIUrl":"https://doi.org/10.1144/qjegh2022-065","url":null,"abstract":"There are many site investigation projects used for the urban planning of a city. They are archived in hard copy or scanned in image files stored on computers. In this study, geological, geotechnical and geophysical data obtained from different site investigation projects in the Acıpayam district were evaluated in the same coordinate system using a geological and geotechnical information system (GEO-GIS) computer program. The Acıpayam GEO-GIS database includes field tests in 82 boreholes, 85 observation pits, laboratory test results of soil samples, 99 seismic refraction measurements and 70 microtremor measurements. Required information from the database can be displayed at its spatial coordinates on a base map and new maps can also be drawn using the GEO-GIS database system. Resultant maps drawn using the Acıpayam GEO-GIS database show that in the northern and eastern parts of the Acıpayam district, where the Oğuz, Kırca, Yassıhöyük, Apa, Ovayurt, Karahüyük, Ucarı and Gedikli villages are located, weak soil layers exist. This means that some damage may be caused to adobe and masonry buildings in the villages during shaking associated with strong earthquakes, as observed after the 5.5 (M w ) earthquake that occurred on 20 March 2019. The Acıpayam GEO-GIS database system is a useful tool for engineers and planners that can assist in drawing GIS-produced maps for geotechnical evaluations of the basin. These maps can be used in decision-making projects for urban planning. Thematic collection: This article is part of the Leading to Innovative Engineering Geology Practices collection available at: https://www.lyellcollection.org/topic/collections/leading-to-innovative-engineering-geology-practices","PeriodicalId":20937,"journal":{"name":"Quarterly Journal of Engineering Geology and Hydrogeology","volume":" 15","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135293671","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The largest environmental remediation project in human history has begun, that of removing hundreds of billions of tonnes of carbon dioxide (CO 2 ) from the atmosphere over the coming century. This removal, together with deep and rapid emissions reduction, will be essential in preventing dangerous climate change. This briefing introduces the field of geochemical CO 2 removal (gCDR), which proposes to accelerate the natural reaction of atmospheric CO 2 with rocks or anthropogenic materials. It also explores the critical role geoenvironmental engineers and geoscientists will have in researching and deploying these technologies. While currently at an early stage of development, it is possible that gCDR will operate at a global scale (billion tonnes of CO 2 per year) by mid/late-century, resulting in an industry that generates $100s billions to $1 trillion in annual revenue, equivalent in scale to the present day oil industry. The core technical competencies of this industry will be derived from geoscience disciplines requiring the contribution of thousands and possibly tens of thousands of workers globally. To realise these opportunities, our community needs to lead in the development of gCDR, help to pioneer its deployment, create standards for monitoring, and verification, and incorporate gCDR into existing education programmes and professional development. Thematic collection: This article is part of the Climate change and resilience in Engineering Geology and Hydrogeology collection available at: https://www.lyellcollection.org/topic/collections/Climate-change-and-resilience-in-engineering-geology-and-hydrogeology
{"title":"Remediating the sky: the role of geoenvironmental engineers and applied geoscientists in geochemical carbon dioxide removal","authors":"P. Renforth","doi":"10.1144/qjegh2023-053","DOIUrl":"https://doi.org/10.1144/qjegh2023-053","url":null,"abstract":"The largest environmental remediation project in human history has begun, that of removing hundreds of billions of tonnes of carbon dioxide (CO 2 ) from the atmosphere over the coming century. This removal, together with deep and rapid emissions reduction, will be essential in preventing dangerous climate change. This briefing introduces the field of geochemical CO 2 removal (gCDR), which proposes to accelerate the natural reaction of atmospheric CO 2 with rocks or anthropogenic materials. It also explores the critical role geoenvironmental engineers and geoscientists will have in researching and deploying these technologies. While currently at an early stage of development, it is possible that gCDR will operate at a global scale (billion tonnes of CO 2 per year) by mid/late-century, resulting in an industry that generates $100s billions to $1 trillion in annual revenue, equivalent in scale to the present day oil industry. The core technical competencies of this industry will be derived from geoscience disciplines requiring the contribution of thousands and possibly tens of thousands of workers globally. To realise these opportunities, our community needs to lead in the development of gCDR, help to pioneer its deployment, create standards for monitoring, and verification, and incorporate gCDR into existing education programmes and professional development. Thematic collection: This article is part of the Climate change and resilience in Engineering Geology and Hydrogeology collection available at: https://www.lyellcollection.org/topic/collections/Climate-change-and-resilience-in-engineering-geology-and-hydrogeology","PeriodicalId":20937,"journal":{"name":"Quarterly Journal of Engineering Geology and Hydrogeology","volume":"3 6","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135634289","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Forest roads are crucial for economic development and resource accessibility, especially in regions with extensive wood demand driven by construction growth. These roads require consistent maintenance to prevent structural issues, even though they experience lower traffic. Traditionally, gypsum has been used for soil stabilization due to its cation exchange capability with clay minerals and flocculation properties. However, its water solubility in wet conditions necessitates innovative solutions. This study explores a novel approach by combining gypsum with rice husk ash (RHA), an abundant agricultural waste, to address the challenges posed by expansive and low-bearing clay soils in forest road construction. In this study, an expansive soil with high plasticity and swelling potential is treated with varying combinations of RHA (5%-20%) and gypsum (2%-6%), followed by curing for 7, 15, and 30 days. Mechanical property tests revealed reduced plasticity and swelling pressure, alongside increased unconfined compressive strength. Microscopic analysis illustrated the formation of a calcium silicate hydrate (CSH) gel and Calcium Alumino Silicate Hydrate (CAH) gel, which possibly contributes to improved stability. This research underscores the potential of sustainable soil stabilization using gypsum and RHA synergy to fortify forest roads against expansive clay soil challenges, promoting eco-friendly and resilient infrastructure solutions.
{"title":"Gypsum and rice husk ash for sustainable stabilization of forest road subgrade","authors":"Ebrahim Sharifi Teshnizi, Mehdi Mirzababaei, Jafar Karimiazar, Reza Arjmandzadeh, Kamran Mahmoudpardabad","doi":"10.1144/qjegh2023-008","DOIUrl":"https://doi.org/10.1144/qjegh2023-008","url":null,"abstract":"Forest roads are crucial for economic development and resource accessibility, especially in regions with extensive wood demand driven by construction growth. These roads require consistent maintenance to prevent structural issues, even though they experience lower traffic. Traditionally, gypsum has been used for soil stabilization due to its cation exchange capability with clay minerals and flocculation properties. However, its water solubility in wet conditions necessitates innovative solutions. This study explores a novel approach by combining gypsum with rice husk ash (RHA), an abundant agricultural waste, to address the challenges posed by expansive and low-bearing clay soils in forest road construction. In this study, an expansive soil with high plasticity and swelling potential is treated with varying combinations of RHA (5%-20%) and gypsum (2%-6%), followed by curing for 7, 15, and 30 days. Mechanical property tests revealed reduced plasticity and swelling pressure, alongside increased unconfined compressive strength. Microscopic analysis illustrated the formation of a calcium silicate hydrate (CSH) gel and Calcium Alumino Silicate Hydrate (CAH) gel, which possibly contributes to improved stability. This research underscores the potential of sustainable soil stabilization using gypsum and RHA synergy to fortify forest roads against expansive clay soil challenges, promoting eco-friendly and resilient infrastructure solutions.","PeriodicalId":20937,"journal":{"name":"Quarterly Journal of Engineering Geology and Hydrogeology","volume":"63 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135778659","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abdul-Kareem H. Al-Rubaiee, Mohanad R. A. Al-Owaidi
The current research focused on the use of some geotechnical characteristics for the initial assessment of soil liquefaction in the sites of the city of Hilla, Babylon Governorate. Five sites were chosen in the city center and relatively close to the Shatt Al-Hilla. Geotechnical properties data were used to separate soils that can be classified as liquefiable from those that are not. The Criteria used in this study included two types: the second Chinese standard, which is based on the natural water content and liquid limit, and the modified Chinese standard, which depends on the clay content and liquid limit on the liquefaction potential of the soil. The results of this study showed that the risk of soil increases with an increase in the natural water content and a decrease in the liquid limit in the second Chinese standard, but in the modified Chinese standard, the liquefaction potential increases with a decrease in each of the clay content less than 10%, the liquid limit is less than or equal to 32%.
{"title":"Initial Assessment of Soil Liquefaction Potential for Selected Sites in Hilla City, Babylon Governorate, Iraq","authors":"Abdul-Kareem H. Al-Rubaiee, Mohanad R. A. Al-Owaidi","doi":"10.1144/qjegh2023-076","DOIUrl":"https://doi.org/10.1144/qjegh2023-076","url":null,"abstract":"The current research focused on the use of some geotechnical characteristics for the initial assessment of soil liquefaction in the sites of the city of Hilla, Babylon Governorate. Five sites were chosen in the city center and relatively close to the Shatt Al-Hilla. Geotechnical properties data were used to separate soils that can be classified as liquefiable from those that are not. The Criteria used in this study included two types: the second Chinese standard, which is based on the natural water content and liquid limit, and the modified Chinese standard, which depends on the clay content and liquid limit on the liquefaction potential of the soil. The results of this study showed that the risk of soil increases with an increase in the natural water content and a decrease in the liquid limit in the second Chinese standard, but in the modified Chinese standard, the liquefaction potential increases with a decrease in each of the clay content less than 10%, the liquid limit is less than or equal to 32%.","PeriodicalId":20937,"journal":{"name":"Quarterly Journal of Engineering Geology and Hydrogeology","volume":"248 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136013390","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Nicol E. Flandes, Felipe A. Villalobos, Robert King
The effect of rock weathering on geotechnical parameters can become substantial in geotechnical design. The weathering degree WD has been normally divided in five levels from fresh rock to completely weathered rock. In this study, the above five WDs are adopted to analyse the variation of several regularly used geotechnical properties. To that aim, a series of laboratory tests to a Chilean granitic rock in different stages of weathering was carried out. The results of the tests have been analysed by normalising each geotechnical parameter respect to the value obtained for slightly weathered samples instead of the fresh rock samples, which is usually adopted. In this way, it was found that the results of unconfined compressive strength UCS reduces steadily and considerably with each WD, which has been previously reported. Conversely, the modulus of deformation and P-wave velocity tend to stabilise the rate of reduction for highly and completely weathered rock samples, which does not agree with the trend and higher rate reductions found by other authors. This stabilisation reduction rate with WD was also found for compaction density, friction angle and Poisson's ratio.
{"title":"The effect of weathering on the variation of geotechnical properties of a granitic rock from Chile","authors":"Nicol E. Flandes, Felipe A. Villalobos, Robert King","doi":"10.1144/qjegh2023-022","DOIUrl":"https://doi.org/10.1144/qjegh2023-022","url":null,"abstract":"The effect of rock weathering on geotechnical parameters can become substantial in geotechnical design. The weathering degree WD has been normally divided in five levels from fresh rock to completely weathered rock. In this study, the above five WDs are adopted to analyse the variation of several regularly used geotechnical properties. To that aim, a series of laboratory tests to a Chilean granitic rock in different stages of weathering was carried out. The results of the tests have been analysed by normalising each geotechnical parameter respect to the value obtained for slightly weathered samples instead of the fresh rock samples, which is usually adopted. In this way, it was found that the results of unconfined compressive strength UCS reduces steadily and considerably with each WD, which has been previously reported. Conversely, the modulus of deformation and P-wave velocity tend to stabilise the rate of reduction for highly and completely weathered rock samples, which does not agree with the trend and higher rate reductions found by other authors. This stabilisation reduction rate with WD was also found for compaction density, friction angle and Poisson's ratio.","PeriodicalId":20937,"journal":{"name":"Quarterly Journal of Engineering Geology and Hydrogeology","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-09-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43086261","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Tropical residual soils are often reported to exhibit highly variable geotechnical characteristics, due to formation by rock weathering under hot, humid conditions. Less is known about the engineering properties of tropical reworked (i.e. transported) soils. The latter soil type is also encountered in tropical regions, but can exhibit sorting and include weak structures formed during transport and deposition, causing instability when exposed in road/rail cuttings. We report a case study of geochemical and engineering properties of tropical reworked soils from the slopes of Mt Lekoumou (Republic of the Congo), a Banded Iron Formation (BIF) ridgeline overlain by loose, unconsolidated clayey gravel. Aside from the upper-most slopes, the area is overlain by colluvium of varying thickness, the target of testing, here. Goethite, kaolinite and hematite are dominant minerals, and the colluvium displays moderately high liquid limits, but comparatively low plasticity index values. Effective cohesion (c') values were 0 and 31 kPa and effective friction angles (ϕ') were 26°-39°. Considerable variation in matric suction pressures for the same sample sites, at the same moisture contents, occurs. Thus, as with tropical residual soils, determining test values that are ‘representative’ of site conditions in tropical transported soils can be problematic, but remains important.
{"title":"Engineering properties of tropical transported soils: case study from the Republic of the Congo","authors":"G. Brink, M. Brook","doi":"10.1144/qjegh2021-134","DOIUrl":"https://doi.org/10.1144/qjegh2021-134","url":null,"abstract":"Tropical residual soils are often reported to exhibit highly variable geotechnical characteristics, due to formation by rock weathering under hot, humid conditions. Less is known about the engineering properties of tropical reworked (i.e. transported) soils. The latter soil type is also encountered in tropical regions, but can exhibit sorting and include weak structures formed during transport and deposition, causing instability when exposed in road/rail cuttings. We report a case study of geochemical and engineering properties of tropical reworked soils from the slopes of Mt Lekoumou (Republic of the Congo), a Banded Iron Formation (BIF) ridgeline overlain by loose, unconsolidated clayey gravel. Aside from the upper-most slopes, the area is overlain by colluvium of varying thickness, the target of testing, here. Goethite, kaolinite and hematite are dominant minerals, and the colluvium displays moderately high liquid limits, but comparatively low plasticity index values. Effective cohesion (c') values were 0 and 31 kPa and effective friction angles (ϕ') were 26°-39°. Considerable variation in matric suction pressures for the same sample sites, at the same moisture contents, occurs. Thus, as with tropical residual soils, determining test values that are ‘representative’ of site conditions in tropical transported soils can be problematic, but remains important.","PeriodicalId":20937,"journal":{"name":"Quarterly Journal of Engineering Geology and Hydrogeology","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43037672","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The Dubaydib wellfield in Southern Jordan comprises 55 wells up to 600 m in depth, and exploits the fossil Ram sandstone aquifer. It has an average output of 100 MCM a -1 and well yields of 51 - 80 l s -1 . Drilling fluid has affected well performance with lowest specific capacities of 1.56 l s -1 m -1 in bentonite drilled wells, highest ( 5.46 l s -1 m -1 ) in water drilled open hole constructions and in the middle range ( 3.07 l s -1 m -1 ) in polymer drilled wells. Well loss coefficients and skin effect values confirm these results. The productivity of bentonite drilled wells has not improved during production indicating that the damage has been irreversible. Well efficiency evaluations have been found to be sensitive to the method of calculation and not to provide a reliable measure of productivity. During the course of wellfield operation (2013-2021) specific capacities declined from an all well average of 3.78 to 3.13 l s -1 m -1 or c.17 %. The decline reflects the deepening of groundwater levels as a result of aquifer response rather than well deterioration. As groundwater extraction is from storage, specific capacities will continue to fall, tentative estimates suggesting to 2.56 l s -1 m -1 after 25 years and 2.16 l s -1 m -1 after 50 years.
位于约旦南部的Dubaydib井田由55口井组成，井深达600米，主要开采拉姆砂岩含水层。它的平均产量为100 MCM a -1，井产量为51 - 80 l s -1。钻井液影响井的性能，膨润土井的比容最小，为1.56 ls -1 m -1，水钻裸眼井的比容最大，为5.46 ls -1 m -1，聚合物井的比容中等，为3.07 ls -1 m -1。井损系数和集肤效应值证实了这些结果。在生产过程中，膨润土钻井的产能并没有得到提高，说明这种损害是不可逆的。人们发现，井效评价对计算方法很敏感，不能提供可靠的产能衡量标准。在井场运行过程中(2013-2021年)，比容量从所有井的平均3.78升/立方米/立方米下降到3.13升/立方米/立方米，降幅为17%。这种下降反映了由于含水层响应而导致的地下水位加深，而不是水井恶化。由于地下水是从储存中提取的，具体容量将继续下降，初步估计25年后为2.56升/ 1立方米/ 1,50年后为2.16升/ 1立方米/ 1。
{"title":"Well performance in relation to design, construction and wellfield operation: a case study from the fossil Ram sandstone aquifer in Southern Jordan","authors":"A. Charalambous, B.R. Burnet","doi":"10.1144/qjegh2023-039","DOIUrl":"https://doi.org/10.1144/qjegh2023-039","url":null,"abstract":"\u0000 The Dubaydib wellfield in Southern Jordan comprises 55 wells up to 600 m in depth, and exploits the fossil Ram sandstone aquifer. It has an average output of 100 MCM a\u0000 -1\u0000 and well yields of 51 - 80 l s\u0000 -1\u0000 . Drilling fluid has affected well performance with lowest specific capacities of 1.56 l s\u0000 -1\u0000 m\u0000 -1\u0000 in bentonite drilled wells, highest ( 5.46 l s\u0000 -1\u0000 m\u0000 -1\u0000 ) in water drilled open hole constructions and in the middle range ( 3.07 l s\u0000 -1\u0000 m\u0000 -1\u0000 ) in polymer drilled wells. Well loss coefficients and skin effect values confirm these results. The productivity of bentonite drilled wells has not improved during production indicating that the damage has been irreversible. Well efficiency evaluations have been found to be sensitive to the method of calculation and not to provide a reliable measure of productivity. During the course of wellfield operation (2013-2021) specific capacities declined from an all well average of 3.78 to 3.13 l s\u0000 -1\u0000 m\u0000 -1\u0000 or c.17 %. The decline reflects the deepening of groundwater levels as a result of aquifer response rather than well deterioration. As groundwater extraction is from storage, specific capacities will continue to fall, tentative estimates suggesting to 2.56 l s\u0000 -1\u0000 m\u0000 -1 \u0000 after 25 years and 2.16 l s\u0000 -1\u0000 m\u0000 -1\u0000 after 50 years.\u0000","PeriodicalId":20937,"journal":{"name":"Quarterly Journal of Engineering Geology and Hydrogeology","volume":" ","pages":""},"PeriodicalIF":1.4,"publicationDate":"2023-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45631160","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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