The retreat of two road-side cut slopes in weathered gneiss in the Middle Himalaya of east Nepal has been assessed by engineering geological mapping, sequential photography and slope profiling over a 40-year period from 1979 to 2018, allowing approximate degradation rates to be calculated. The rate of removal of completely weathered gneiss and residual soil was about twice that of highly weathered material, primarily reflecting increased micro-cracking and breakdown of feldspars and micas in the weathered fabric. Surface water erosion by rilling and gullying in the summer monsoon wet season was the dominant process affecting the slopes, with landsliding (mainly by soil falls and debris slides) playing a secondary role. Drainage and bio-engineering protection measures applied to the slopes within the first three to 12 years after excavation were effective in reducing the degradation rate by between one to two orders of magnitude once the slopes had developed a moderate vegetation cover. The total volume of material removed from the slopes over four decades is equivalent to average rates of ground lowering in the range of 150 to 320 mm a -1 and 2 to 4 mm a -1 , before and after protection works respectively. The latter range is similar to long-term denudation rates measured in drainage catchments in the region with similar settings. Supplementary material: https://doi.org/10.6084/m9.figshare.c.7005885
{"title":"Degradation and protection of cut slopes in weathered gneiss; a 40-year case study","authors":"R.P. Martin, J.H. Howell","doi":"10.1144/qjegh2023-073","DOIUrl":"https://doi.org/10.1144/qjegh2023-073","url":null,"abstract":"\u0000 The retreat of two road-side cut slopes in weathered gneiss in the Middle Himalaya of east Nepal has been assessed by engineering geological mapping, sequential photography and slope profiling over a 40-year period from 1979 to 2018, allowing approximate degradation rates to be calculated. The rate of removal of completely weathered gneiss and residual soil was about twice that of highly weathered material, primarily reflecting increased micro-cracking and breakdown of feldspars and micas in the weathered fabric. Surface water erosion by rilling and gullying in the summer monsoon wet season was the dominant process affecting the slopes, with landsliding (mainly by soil falls and debris slides) playing a secondary role. Drainage and bio-engineering protection measures applied to the slopes within the first three to 12 years after excavation were effective in reducing the degradation rate by between one to two orders of magnitude once the slopes had developed a moderate vegetation cover. The total volume of material removed from the slopes over four decades is equivalent to average rates of ground lowering in the range of 150 to 320 mm a\u0000 -1\u0000 and 2 to 4 mm a\u0000 -1\u0000 , before and after protection works respectively. The latter range is similar to long-term denudation rates measured in drainage catchments in the region with similar settings.\u0000 \u0000 \u0000 Supplementary material:\u0000 https://doi.org/10.6084/m9.figshare.c.7005885\u0000","PeriodicalId":20937,"journal":{"name":"Quarterly Journal of Engineering Geology and Hydrogeology","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2024-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139381140","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}
Near surface characterization is often challenging using a single geophysical technique. We show that seismic refraction is an effective tool by combining P-and S-wave velocity models in the form of V P /V S and Poisson's Ratio ( σ ) to detect buried targets along with electrical resistivity imaging (ERI). We acquired vertical and horizontal component seismic data along a 2D profile over two known targets. First, is a water pipe of ∼0.8 m diameter located ∼1.5 m below the surface and second, a storm drainage pipe (SDP) of ∼1 m diameter at ∼2 m depth. The first arrival times of vertical and horizontal component data were picked and inverted using grid-based tomography. The resulting velocity models have smoothly varying structures and could not identify any of the target features. However, when combined as V P /V S and Poisson's Ratio models, the features clearly appeared as anomalous zones. A collocated 2D electrical resistivity model shows the presence of anomalies around the same locations. Our study suggests that anomalous V P /V S and Poisson's ratio values derived from seismic velocities are indicative of the relative changes due to the disturbances in the soil because of construction with respect to the background instead of the anomaly.
使用单一地球物理技术进行近地表特征描述往往具有挑战性。我们通过将 V P /V S 和泊松比（σ）形式的 P 波和 S 波速度模型与电阻率成像（ERI）相结合来探测埋藏目标，从而证明地震折射是一种有效的工具。我们沿二维剖面采集了两个已知目标的垂直和水平分量地震数据。第一个是位于地表下 1.5 米处的直径为 0.8 米的水管，第二个是位于 2 米深处的直径为 1 米的雨水管。垂直和水平分量数据的首次到达时间被提取出来，并利用网格层析技术进行反演。所得到的速度模型具有平滑变化的结构，无法识别任何目标特征。然而，当结合为 V P /V S 和泊松比模型时，特征明显显示为异常区。与之相配合的二维电阻率模型显示，在相同位置周围存在异常。我们的研究表明，从地震速度得出的异常 V P /V S 和泊松比值表明了由于施工对土壤的扰动而导致的相对于背景的变化，而不是异常。
{"title":"Understanding the Behavior of Seismically Derived Poisson's Ratio in Near Surface Characterization","authors":"Md Iftekhar Alam, A. Katumwehe, Salman Abbasi","doi":"10.1144/qjegh2023-025","DOIUrl":"https://doi.org/10.1144/qjegh2023-025","url":null,"abstract":"\u0000 Near surface characterization is often challenging using a single geophysical technique. We show that seismic refraction is an effective tool by combining P-and S-wave velocity models in the form of V\u0000 P\u0000 /V\u0000 S\u0000 and Poisson's Ratio (\u0000 \u0000 \u0000 σ\u0000 \u0000 \u0000 ) to detect buried targets along with electrical resistivity imaging (ERI). We acquired vertical and horizontal component seismic data along a 2D profile over two known targets. First, is a water pipe of ∼0.8 m diameter located ∼1.5 m below the surface and second, a storm drainage pipe (SDP) of ∼1 m diameter at ∼2 m depth. The first arrival times of vertical and horizontal component data were picked and inverted using grid-based tomography. The resulting velocity models have smoothly varying structures and could not identify any of the target features. However, when combined as V\u0000 P\u0000 /V\u0000 S\u0000 and Poisson's Ratio models, the features clearly appeared as anomalous zones. A collocated 2D electrical resistivity model shows the presence of anomalies around the same locations. Our study suggests that anomalous V\u0000 P\u0000 /V\u0000 S\u0000 and Poisson's ratio values derived from seismic velocities are indicative of the relative changes due to the disturbances in the soil because of construction with respect to the background instead of the anomaly.\u0000","PeriodicalId":20937,"journal":{"name":"Quarterly Journal of Engineering Geology and Hydrogeology","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2023-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138957019","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}
A hydrogeological investigation is presented that focused on development of a drought resilient groundwater supply for a town (Carlow) in the Irish Midlands. The combination of thick overlying glacial deposits, and Carboniferous limestones of low primary permeability posed a challenge to identifying a groundwater source. The source exploration strategy comprised surface geophysics and follow-on pilot well drilling to identify zones of high (secondary) permeability in bedrock. The study identified a previously-unrecorded large (∼3.5 km long) and deep infilled karst feature that possibly extends 2 km further to a nearby area of known Neogene-aged karst infill. Separately, the investigation revealed new areas of dolomitized limestone, suitable for water supply development, where two production wells were constructed. A program of pumping tests showed that dolomitized limestone areas exhibited low-nitrate groundwater quality, relatively high transmissivity and sustaining recharge boundaries (leakage from a nearby riverbed). Analysis of data from the operational stage provided further insights into recharge behaviour, and showed that groundwater levels are resilient during droughts at current abstraction rates. The analysis concluded that the wellfield could sustain higher abstraction volumes, even through extended periods of low effective rainfall. 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":"Development of a drought-resilient water supply from dolomitized limestones of the Irish Midlands","authors":"O. D. Higgins","doi":"10.1144/qjegh2023-043","DOIUrl":"https://doi.org/10.1144/qjegh2023-043","url":null,"abstract":"A hydrogeological investigation is presented that focused on development of a drought resilient groundwater supply for a town (Carlow) in the Irish Midlands. The combination of thick overlying glacial deposits, and Carboniferous limestones of low primary permeability posed a challenge to identifying a groundwater source. The source exploration strategy comprised surface geophysics and follow-on pilot well drilling to identify zones of high (secondary) permeability in bedrock. The study identified a previously-unrecorded large (∼3.5 km long) and deep infilled karst feature that possibly extends 2 km further to a nearby area of known Neogene-aged karst infill. Separately, the investigation revealed new areas of dolomitized limestone, suitable for water supply development, where two production wells were constructed. A program of pumping tests showed that dolomitized limestone areas exhibited low-nitrate groundwater quality, relatively high transmissivity and sustaining recharge boundaries (leakage from a nearby riverbed). Analysis of data from the operational stage provided further insights into recharge behaviour, and showed that groundwater levels are resilient during droughts at current abstraction rates. The analysis concluded that the wellfield could sustain higher abstraction volumes, even through extended periods of low effective rainfall.\u0000 \u0000 Thematic collection:\u0000 This article is part of the Climate change and resilience in Engineering Geology and Hydrogeology collection available at:\u0000 https://www.lyellcollection.org/topic/collections/climate-change-and-resilience-in-engineering-geology-and-hydrogeology\u0000","PeriodicalId":20937,"journal":{"name":"Quarterly Journal of Engineering Geology and Hydrogeology","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2023-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138955217","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}
A jet grouting trial was undertaken within the Thames Tideway Tunnel shaft at Kirtling Street in Battersea, southwest London, to assess the viability of the technique within the Lambeth Group and Thanet Formation sediments up to 60 m below ground level (bgl). There was no precedent industry experience of jet grouting in the U.K. at this depth and in these soil types. Four, separate, upper and lower grout columns were constructed respectively within upper and lower granular zones, inside the shaft footprint and then exhumed for inspection and measurement during ensuing excavation within the diaphragm wall lining. Target diameters for the upper columns were achieved within granular channel sand and Laminated Bed material, with minimal vertical deviation. These were not so successfully achieved, however, within stiff cohesive Laminated Bed and Lower Shelly Clay materials. Formation of the lower columns was severely restricted in dense gravel belonging to the ‘Pebble Bed’ and stiff gravelly clay, at the top of the Upnor Formation, but with target diameters being achieved in the lower portion of the formation, comprising Upnor sand. At their base, the column diameters were again, restricted in the very dense sand at the top of the Thanet Formation.
{"title":"Jet grouting to new depths in the Lambeth Group and Thanet Formation beneath London","authors":"T.G. Newman, A.J. Skarda","doi":"10.1144/qjegh2023-083","DOIUrl":"https://doi.org/10.1144/qjegh2023-083","url":null,"abstract":"A jet grouting trial was undertaken within the Thames Tideway Tunnel shaft at Kirtling Street in Battersea, southwest London, to assess the viability of the technique within the Lambeth Group and Thanet Formation sediments up to 60 m below ground level (bgl).\u0000 There was no precedent industry experience of jet grouting in the U.K. at this depth and in these soil types.\u0000 Four, separate, upper and lower grout columns were constructed respectively within upper and lower granular zones, inside the shaft footprint and then exhumed for inspection and measurement during ensuing excavation within the diaphragm wall lining. Target diameters for the upper columns were achieved within granular channel sand and Laminated Bed material, with minimal vertical deviation. These were not so successfully achieved, however, within stiff cohesive Laminated Bed and Lower Shelly Clay materials.\u0000 Formation of the lower columns was severely restricted in dense gravel belonging to the ‘Pebble Bed’ and stiff gravelly clay, at the top of the Upnor Formation, but with target diameters being achieved in the lower portion of the formation, comprising Upnor sand. At their base, the column diameters were again, restricted in the very dense sand at the top of the Thanet Formation.","PeriodicalId":20937,"journal":{"name":"Quarterly Journal of Engineering Geology and Hydrogeology","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2023-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138980074","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}
Jing Wang, Mingming He, Zhuoya Yuan, Xudong Ma, Xinxing Liu, Haoteng Wang, Bo Luo
Evaluating the anisotropy of rock and its size effect in spatial variation is of great significance for improving engineering efficiency and stability. For this purpose, an anisotropy index is used to quantify the magnitude of anisotropy in rock. Digital drilling tests are carried out in three directions on six types of rock to investigate the anisotropy of drilling parameters. The rock is subdivided into multiple diminutive units along the depth of drilling, and the effect of size on rock anisotropy based on drilling work was studied. The research findings indicate that the drilling work of six rock types exhibits anisotropy. Among these, the anisotropy sequence for the total drilling work of each rock is as follows: red sandstone > granite > slate > gneiss > sandstone > argillaceous sandstone. As the length of individual rock units increases, the anisotropy index of drilling work initially exhibits a fluctuating trend, subsequently reaching a state of stability, thereby manifesting a size effect. Furthermore, the Representative Elementary Volume (REV) for each type of rock exhibits distinct variations. The anisotropy indices for drilling work along the depth of the borehole exhibit an initial phase of rapid increase, followed by a convergence towards a value close to 1.0. The anisotropy of rocks demonstrates size dependence, and size effects also exhibit anisotropy. Anisotropy and its size effects are interconnected and inseparable. The reliability of the cited anisotropy index is checked by comparison with the other two anisotropy indices. The comparison results show that the method can reliably determine rock anisotropy. In summary, the research outlined in this paper presents a highly efficient and straightforward approach to evaluate the effect of size on rock anisotropy.
{"title":"Size Effect of Anisotropy in Rocks Spatial Variability: Evaluating through Digital Drilling","authors":"Jing Wang, Mingming He, Zhuoya Yuan, Xudong Ma, Xinxing Liu, Haoteng Wang, Bo Luo","doi":"10.1144/qjegh2023-070","DOIUrl":"https://doi.org/10.1144/qjegh2023-070","url":null,"abstract":"Evaluating the anisotropy of rock and its size effect in spatial variation is of great significance for improving engineering efficiency and stability. For this purpose, an anisotropy index is used to quantify the magnitude of anisotropy in rock. Digital drilling tests are carried out in three directions on six types of rock to investigate the anisotropy of drilling parameters. The rock is subdivided into multiple diminutive units along the depth of drilling, and the effect of size on rock anisotropy based on drilling work was studied. The research findings indicate that the drilling work of six rock types exhibits anisotropy. Among these, the anisotropy sequence for the total drilling work of each rock is as follows: red sandstone > granite > slate > gneiss > sandstone > argillaceous sandstone. As the length of individual rock units increases, the anisotropy index of drilling work initially exhibits a fluctuating trend, subsequently reaching a state of stability, thereby manifesting a size effect. Furthermore, the Representative Elementary Volume (REV) for each type of rock exhibits distinct variations. The anisotropy indices for drilling work along the depth of the borehole exhibit an initial phase of rapid increase, followed by a convergence towards a value close to 1.0. The anisotropy of rocks demonstrates size dependence, and size effects also exhibit anisotropy. Anisotropy and its size effects are interconnected and inseparable. The reliability of the cited anisotropy index is checked by comparison with the other two anisotropy indices. The comparison results show that the method can reliably determine rock anisotropy. In summary, the research outlined in this paper presents a highly efficient and straightforward approach to evaluate the effect of size on rock anisotropy.","PeriodicalId":20937,"journal":{"name":"Quarterly Journal of Engineering Geology and Hydrogeology","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2023-11-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139220065","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}
S. Libby, Lee Hartley, Robert Turnbull, Mark Cottrell, T. Bým, N. Josephson, Raymond Munier, J. Selroos, D. Mas Ivars
Quantitative assessment of the flow properties and mechanical stability of naturally fractured rock is frequently practiced across the mining, petroleum, geothermal, geological disposal, construction, and environmental remediation industries. These fluid and mechanical behaviours are strongly influenced by the connectivity of the fracture system and the size of the intact rock blocks. However, these are amongst the more difficult fracture system properties to characterise and honour in numerical simulations. Nonetheless, they are still the product of interactions between fractures that can be conceptualised as a series of deformation events following geomechanical principles. Generating numerical models of fracture networks by simulating this deformation with a coupled and evolving rock mass and stress field is a significant undertaking. Instead, large scale fracture network models can be ‘grown’ dynamically according to rules that mimic the underlying mechanical processes and deformation history. This paper explores a computationally efficient rules-based method to generate fracture networks, demonstrates how different types of fracture patterns can be simulated, and illustrates how inclusion of fracture interactions can affect flow and mechanical properties. Relative to methods without fracture interaction and in contrast to some other rules-based approaches, the method described here regularises and increases fracture connectivity and decreases flow channelling.
{"title":"Exploring the impact of fracture interaction on connectivity and flow channelling using grown fracture networks","authors":"S. Libby, Lee Hartley, Robert Turnbull, Mark Cottrell, T. Bým, N. Josephson, Raymond Munier, J. Selroos, D. Mas Ivars","doi":"10.1144/qjegh2023-010","DOIUrl":"https://doi.org/10.1144/qjegh2023-010","url":null,"abstract":"Quantitative assessment of the flow properties and mechanical stability of naturally fractured rock is frequently practiced across the mining, petroleum, geothermal, geological disposal, construction, and environmental remediation industries. These fluid and mechanical behaviours are strongly influenced by the connectivity of the fracture system and the size of the intact rock blocks. However, these are amongst the more difficult fracture system properties to characterise and honour in numerical simulations. Nonetheless, they are still the product of interactions between fractures that can be conceptualised as a series of deformation events following geomechanical principles. Generating numerical models of fracture networks by simulating this deformation with a coupled and evolving rock mass and stress field is a significant undertaking. Instead, large scale fracture network models can be ‘grown’ dynamically according to rules that mimic the underlying mechanical processes and deformation history. This paper explores a computationally efficient rules-based method to generate fracture networks, demonstrates how different types of fracture patterns can be simulated, and illustrates how inclusion of fracture interactions can affect flow and mechanical properties. Relative to methods without fracture interaction and in contrast to some other rules-based approaches, the method described here regularises and increases fracture connectivity and decreases flow channelling.","PeriodicalId":20937,"journal":{"name":"Quarterly Journal of Engineering Geology and Hydrogeology","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2023-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139254444","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}
Improving low flows in Chalk streams by relocating groundwater abstraction further downstream is an idea that has become popular in the UK in recent years. Simulations using the Environment Agency's Hertfordshire Chalk Groundwater Model predict that reducing groundwater abstraction close to ephemeral or intermittent Chalk streams is more likely to increase river flows during high flow conditions than during low flows. This finding helps to explain the apparent lack of observed benefit to river flows during drought periods, in catchments where abstractions have been reduced. If abstraction reductions are predicted to result in more increase to high river flows than to low flows, they may risk contributing to increased flood likelihood downstream, without providing significant habitat protection during low flows. Conversely, it has also been found that under certain circumstances, preferential benefits can be predicted for low flows. Simulations show that such benefits are most likely to manifest by relocating abstraction to downstream locations where groundwater levels are already below the base of the river bed (e.g. due to existing abstraction or artificial channel modifications). Here, the varying degree of hydraulic connection between groundwater and river can result in preferential benefits to downstream low flows and reduced downstream flood risk. Thematic collection: This article is part of the Karst: Characterization, Hazards & Hydrogeology collection available at: https://www.lyellcollection.org/topic/collections/karst
{"title":"Predicted variable river response at high and low flows due to groundwater abstraction changes in Chalk catchments","authors":"Adam Taylor, Daniel R. Yarker, Ilias Karapanos","doi":"10.1144/qjegh2023-074","DOIUrl":"https://doi.org/10.1144/qjegh2023-074","url":null,"abstract":"Improving low flows in Chalk streams by relocating groundwater abstraction further downstream is an idea that has become popular in the UK in recent years. Simulations using the Environment Agency's Hertfordshire Chalk Groundwater Model predict that reducing groundwater abstraction close to ephemeral or intermittent Chalk streams is more likely to increase river flows during high flow conditions than during low flows. This finding helps to explain the apparent lack of observed benefit to river flows during drought periods, in catchments where abstractions have been reduced. If abstraction reductions are predicted to result in more increase to high river flows than to low flows, they may risk contributing to increased flood likelihood downstream, without providing significant habitat protection during low flows. Conversely, it has also been found that under certain circumstances, preferential benefits can be predicted for low flows. Simulations show that such benefits are most likely to manifest by relocating abstraction to downstream locations where groundwater levels are already below the base of the river bed (e.g. due to existing abstraction or artificial channel modifications). Here, the varying degree of hydraulic connection between groundwater and river can result in preferential benefits to downstream low flows and reduced downstream flood risk. Thematic collection: This article is part of the Karst: Characterization, Hazards & Hydrogeology collection available at: https://www.lyellcollection.org/topic/collections/karst","PeriodicalId":20937,"journal":{"name":"Quarterly Journal of Engineering Geology and Hydrogeology","volume":null,"pages":null},"PeriodicalIF":1.4,"publicationDate":"2023-11-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139269669","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}
Wentao Yang, Xiaopeng Su, Zhou Lei, Wenjie Wu, Xu Wei, Ruide Lei
Anisotropic flow characteristics in single-fractured tensile and shear fractures of granite subjected to various confining stress were investigated by experiments and experimental results-based flow simulations. Anisotropic characteristics in aspects like permeability reduction rate, stress dependency of permeability, flow path in fracture and fracture aperture distribution were analyzed and compared between tensile and shear fractures. The main conclusions are as follows: (1) for tensile fracture, k X is slightly lower than k Y , the average permeability anisotropic coefficient α k ( α k = k X / k Y ) is in the range of 0.236∼0.779. For shear fracture, k X is obviously lower than k Y , α k is in the range of 0.038∼0.163, therefore, the permeability anisotropy in shear fracture is stronger than tensile fracture. (2) Strong channeling effect exists in both shear and tensile fractures. The stress dependence coefficient of permeability is 0.731MPa -1 in X direction and 0.365MPa -1 in Y direction for tensile fracture and this data is 0.034 and 0.010MPa -1 respectively for shear fracture, indicating that the dependency of permeability on stress also shows anisotropic. (3) An empirical model of α k based on stress and fracture aperture variogram was proposed. Based on α k , permeability along both X and Y directions can be predicted well, especially under relatively high confining stress.
通过实验和基于实验结果的流动模拟，研究了不同围应力作用下花岗岩单裂缝拉剪裂缝的各向异性流动特征。分析并比较了张缝与剪切缝在渗透率降低率、渗透率应力依赖性、裂缝内流道、裂缝孔径分布等方面的各向异性特征。主要结论如下:(1)对于张性裂缝，k X略低于k Y，平均渗透率各向异性系数α k (α k = k X / k Y)在0.236 ~ 0.779之间。对于剪切裂缝，k X明显小于k Y， α k在0.038 ~ 0.163范围内，因此，剪切裂缝的渗透率各向异性强于拉伸裂缝。(2)剪切裂缝和张拉裂缝均存在较强的通道效应。拉伸裂缝X方向渗透率应力依赖系数为0.731MPa -1, Y方向渗透率应力依赖系数为0.365MPa -1，剪切裂缝渗透率应力依赖系数分别为0.034 mpa -1和0.010MPa -1，表明渗透率对应力的依赖也具有各向异性。(3)提出了基于应力和裂缝孔径变异函数的α k经验模型。基于α k，可以很好地预测X和Y方向的渗透率，特别是在较高围应力条件下。
{"title":"Anisotropic flow characteristics in single-fractured tensile and shear fractures of granite subjected to various confining stress","authors":"Wentao Yang, Xiaopeng Su, Zhou Lei, Wenjie Wu, Xu Wei, Ruide Lei","doi":"10.1144/qjegh2023-094","DOIUrl":"https://doi.org/10.1144/qjegh2023-094","url":null,"abstract":"Anisotropic flow characteristics in single-fractured tensile and shear fractures of granite subjected to various confining stress were investigated by experiments and experimental results-based flow simulations. Anisotropic characteristics in aspects like permeability reduction rate, stress dependency of permeability, flow path in fracture and fracture aperture distribution were analyzed and compared between tensile and shear fractures. The main conclusions are as follows: (1) for tensile fracture, k X is slightly lower than k Y , the average permeability anisotropic coefficient <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" overflow=\"scroll\"> <mml:mi>α</mml:mi> </mml:math> k ( <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" overflow=\"scroll\"> <mml:mi>α</mml:mi> </mml:math> k = k X / k Y ) is in the range of 0.236∼0.779. For shear fracture, k X is obviously lower than k Y , <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" overflow=\"scroll\"> <mml:mi>α</mml:mi> </mml:math> k is in the range of 0.038∼0.163, therefore, the permeability anisotropy in shear fracture is stronger than tensile fracture. (2) Strong channeling effect exists in both shear and tensile fractures. The stress dependence coefficient of permeability is 0.731MPa -1 in X direction and 0.365MPa -1 in Y direction for tensile fracture and this data is 0.034 and 0.010MPa -1 respectively for shear fracture, indicating that the dependency of permeability on stress also shows anisotropic. (3) An empirical model of <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" overflow=\"scroll\"> <mml:mi>α</mml:mi> </mml:math> k based on stress and fracture aperture variogram was proposed. Based on <mml:math xmlns:mml=\"http://www.w3.org/1998/Math/MathML\" overflow=\"scroll\"> <mml:mi>α</mml:mi> </mml:math> k , permeability along both X and Y directions can be predicted well, especially under relatively high confining stress.","PeriodicalId":20937,"journal":{"name":"Quarterly Journal of Engineering Geology and Hydrogeology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136346976","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}
Understanding the spatial variations in soil-rock profiles is crucial for identifying weathered rock layers and mapping geological structures, particularly in the complex feldspar-rich granitic terrain of Penang Island, Malaysia. This study employs a combination of electrical resistivity and seismic refraction tomographic techniques, along with borehole lithological data, in three distinct areas on the island. Its goal is to provide insights into surficial and subsurface soil-rock properties and water-bearing structures within the North Penang Pluton (including a part of the Sungai Ara axis) for sustainable groundwater development, addressing the region's growing population's needs. The research identifies three distinct geological units near the surface: residual soils, highly to moderately weathered/fractured granitic layers, and fresh bedrock, each with its hydrogeological properties. Promisingly, the weathered layers offer significant groundwater development potential, with deep-weathered and potentially fractured zones exceeding 30 meters in the study area. These findings have substantial implications for sustainable groundwater development, especially in tropical hard-rock terrains. Additionally, the study underscores the limitations of small geophysical spacings for probing deeper groundwater resources. This knowledge is essential for informed decision-making in water resource management and infrastructure development, addressing the ongoing global challenge of ensuring access to clean water resources amid population growth.
{"title":"Geophysical research on the interplays between soil-rock variability and hydrogeological structures: a case study","authors":"Adedibu Sunny Akingboye","doi":"10.1144/qjegh2023-100","DOIUrl":"https://doi.org/10.1144/qjegh2023-100","url":null,"abstract":"Understanding the spatial variations in soil-rock profiles is crucial for identifying weathered rock layers and mapping geological structures, particularly in the complex feldspar-rich granitic terrain of Penang Island, Malaysia. This study employs a combination of electrical resistivity and seismic refraction tomographic techniques, along with borehole lithological data, in three distinct areas on the island. Its goal is to provide insights into surficial and subsurface soil-rock properties and water-bearing structures within the North Penang Pluton (including a part of the Sungai Ara axis) for sustainable groundwater development, addressing the region's growing population's needs. The research identifies three distinct geological units near the surface: residual soils, highly to moderately weathered/fractured granitic layers, and fresh bedrock, each with its hydrogeological properties. Promisingly, the weathered layers offer significant groundwater development potential, with deep-weathered and potentially fractured zones exceeding 30 meters in the study area. These findings have substantial implications for sustainable groundwater development, especially in tropical hard-rock terrains. Additionally, the study underscores the limitations of small geophysical spacings for probing deeper groundwater resources. This knowledge is essential for informed decision-making in water resource management and infrastructure development, addressing the ongoing global challenge of ensuring access to clean water resources amid population growth.","PeriodicalId":20937,"journal":{"name":"Quarterly Journal of Engineering Geology and Hydrogeology","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136346973","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}
Wengui Huang, Fleur A. Loveridge, Kevin M. Briggs, Joel A. Smethurst, Nader Saffari, Fiona Thomson
Understanding and mitigating the impact of climate change on the built environment is becoming increasingly important worldwide. Earthworks (embankments and cuttings) supporting road and rail transportation networks often have direct contact with the atmosphere and are therefore influenced by extreme weather events and seasonal weather patterns. Atmospheric wetting and drying alters porewater pressures (PWPs) within earthworks, potentially contributing to the deformation and failure of earthwork slopes. Consequently, it is essential to understand the influence of climate change on PWPs within earthwork slopes, to inform strategies for their design, assessment and maintenance. Extensive 1D seepage analyses were carried out for typical railway embankments in the London area. The analyses showed that forecast hotter, drier summers will increase the water storage capacity of earthworks. This will lead to increased net infiltration in the winter months owing to both a forecast increase in rainfall and a longer time being required to saturate the soil pores and bring the water table back to the slope surface. Hence, despite the forecast increase in winter rainfall, this will not lead to higher design PWP regimes. The analyses were conducted for the London area, but this approach and conceptual framework can be readily adapted for other locations. 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":"Forecast climate change impact on pore-water pressure regimes for the design and assessment of clay earthworks","authors":"Wengui Huang, Fleur A. Loveridge, Kevin M. Briggs, Joel A. Smethurst, Nader Saffari, Fiona Thomson","doi":"10.1144/qjegh2023-015","DOIUrl":"https://doi.org/10.1144/qjegh2023-015","url":null,"abstract":"Understanding and mitigating the impact of climate change on the built environment is becoming increasingly important worldwide. Earthworks (embankments and cuttings) supporting road and rail transportation networks often have direct contact with the atmosphere and are therefore influenced by extreme weather events and seasonal weather patterns. Atmospheric wetting and drying alters porewater pressures (PWPs) within earthworks, potentially contributing to the deformation and failure of earthwork slopes. Consequently, it is essential to understand the influence of climate change on PWPs within earthwork slopes, to inform strategies for their design, assessment and maintenance. Extensive 1D seepage analyses were carried out for typical railway embankments in the London area. The analyses showed that forecast hotter, drier summers will increase the water storage capacity of earthworks. This will lead to increased net infiltration in the winter months owing to both a forecast increase in rainfall and a longer time being required to saturate the soil pores and bring the water table back to the slope surface. Hence, despite the forecast increase in winter rainfall, this will not lead to higher design PWP regimes. The analyses were conducted for the London area, but this approach and conceptual framework can be readily adapted for other locations. 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":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2023-11-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135087724","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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