Desiccation cracks compromise soil integrity and weaken its strength, causing a range of detrimental consequences across various domains. Elucidating the cracking mechanism can aid in managing crack propagation and mitigating the associated risks. This study monitored and compared the evolution of crack patterns on the soil surface and fracture morphologies on the soil cross-section during the drying process using a tested soil sample. Multiple fracture morphological features are discerned on the soil cross-section, encompassing initiation points and plumose structures. Soil fracture morphologies are categorized into three cases based on the initiation point's location, referred to as "Top-initiated structure", "Bottom-initiated structure" and "Truncated structure". Experimental results demonstrate that plumose structures result from the division of the crack front under mixed-mode loading. Cracking under mixed-mode I+II loading leads to cross-section tilting, resulting in curved surface cracks. Conversely, cracking under mixed-mode I+III loading causes cross-section twisting, generating hackle lines and step structures. Furthermore, the crack front radiates from the initiation point, creating orthogonal hackle lines. The geometric relationship confirms that the soil fracture morphology is a good indicator of the cracking process, both in laboratory tests and field observations.
{"title":"Fracture morphology of desiccation cracks in clayey soil","authors":"Zhao-Lin Cai, C. Tang, Q. Cheng, Bin Shi","doi":"10.1139/cgj-2023-0099","DOIUrl":"https://doi.org/10.1139/cgj-2023-0099","url":null,"abstract":"Desiccation cracks compromise soil integrity and weaken its strength, causing a range of detrimental consequences across various domains. Elucidating the cracking mechanism can aid in managing crack propagation and mitigating the associated risks. This study monitored and compared the evolution of crack patterns on the soil surface and fracture morphologies on the soil cross-section during the drying process using a tested soil sample. Multiple fracture morphological features are discerned on the soil cross-section, encompassing initiation points and plumose structures. Soil fracture morphologies are categorized into three cases based on the initiation point's location, referred to as \"Top-initiated structure\", \"Bottom-initiated structure\" and \"Truncated structure\". Experimental results demonstrate that plumose structures result from the division of the crack front under mixed-mode loading. Cracking under mixed-mode I+II loading leads to cross-section tilting, resulting in curved surface cracks. Conversely, cracking under mixed-mode I+III loading causes cross-section twisting, generating hackle lines and step structures. Furthermore, the crack front radiates from the initiation point, creating orthogonal hackle lines. The geometric relationship confirms that the soil fracture morphology is a good indicator of the cracking process, both in laboratory tests and field observations.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":"31 3","pages":""},"PeriodicalIF":3.6,"publicationDate":"2023-12-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138972336","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Borui Ge, Gary Martin, Matthew S Dietz, G. Mylonakis, Andrea Diambra
This paper describes a novel laboratory test apparatus for investigating the axial interaction between pipeline and soil. Contrary to the majority of existing pipe-soil shear rigs, the proposed apparatus applies a relative pipe-soil shear displacement through driving a soil box below an axially restrained pipe segment, which is instrumented to measure the pipe settlement and the axial resistance at the pipe-soil contact surface. Through axial shear tests of polypropylene pipe segment on sand, this paper explores the effect of vertical loads, soil types and densities on the resulting axial resistance and estimates the interface stress evolution. The coefficients of axial resistance obtained from large-scale pipe-soil shear tests are compared to those obtained via planar element interface shear tests with consideration of the wedging effect. Their consistency suggests that, under the low stress levels investigated in this work, the effect of both pipeline curvature and settlement on the resultant data is minor. The agreement provides validation for the novel apparatus to generate high-quality data under controlled conditions for future studies. The findings of this study will also potentially help reduce the uncertainties around subsea pipeline design when linking the interface shear behaviour at element scale to large-scale pipe-soil interaction.
{"title":"A novel pipe-segment shear test apparatus: Polypropylene pipe behaviour over sand beds vs element interface tests","authors":"Borui Ge, Gary Martin, Matthew S Dietz, G. Mylonakis, Andrea Diambra","doi":"10.1139/cgj-2023-0015","DOIUrl":"https://doi.org/10.1139/cgj-2023-0015","url":null,"abstract":"This paper describes a novel laboratory test apparatus for investigating the axial interaction between pipeline and soil. Contrary to the majority of existing pipe-soil shear rigs, the proposed apparatus applies a relative pipe-soil shear displacement through driving a soil box below an axially restrained pipe segment, which is instrumented to measure the pipe settlement and the axial resistance at the pipe-soil contact surface. Through axial shear tests of polypropylene pipe segment on sand, this paper explores the effect of vertical loads, soil types and densities on the resulting axial resistance and estimates the interface stress evolution. The coefficients of axial resistance obtained from large-scale pipe-soil shear tests are compared to those obtained via planar element interface shear tests with consideration of the wedging effect. Their consistency suggests that, under the low stress levels investigated in this work, the effect of both pipeline curvature and settlement on the resultant data is minor. The agreement provides validation for the novel apparatus to generate high-quality data under controlled conditions for future studies. The findings of this study will also potentially help reduce the uncertainties around subsea pipeline design when linking the interface shear behaviour at element scale to large-scale pipe-soil interaction.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":"9 6","pages":""},"PeriodicalIF":3.6,"publicationDate":"2023-12-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138975435","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Water spewing is a potential risk when Earth Pressure Balance (EPB) shields pass through water-rich sandy strata, and may even cause ground instability. A low permeability of excavated sands via active conditioning is required to avoid water spewing. This study investigated the effect of water pressure on the permeability of foam-conditioned sands using laboratory permeability tests. The water pressure, for the first time, is decoupled with the hydraulic gradient, owing to a newly developed permeameter with the controllable downstream hydraulic pressure in the laboratory. The results show that the permeability is significantly affected by the water pressure, and the effect is also predominantly dependent upon the Foam Injection Ratio (FIR). The initial permeability coefficient increases with an increasing water pressure, while the initial stable period duration decreases. The water-plugging structure formed by foam bubbles and sand particles is prone to be damaged under high water pressure. The underlying mechanism of water pressure in modifying the permeability of conditioned sands is also examined from a particle-scale perspective.
{"title":"Effect of water pressure on permeability of foam-conditioned sands for EPB shield tunnelling","authors":"Zhiyao Feng, Shuying Wang, Tongming Qu, Xiangcou Zheng","doi":"10.1139/cgj-2023-0419","DOIUrl":"https://doi.org/10.1139/cgj-2023-0419","url":null,"abstract":"Water spewing is a potential risk when Earth Pressure Balance (EPB) shields pass through water-rich sandy strata, and may even cause ground instability. A low permeability of excavated sands via active conditioning is required to avoid water spewing. This study investigated the effect of water pressure on the permeability of foam-conditioned sands using laboratory permeability tests. The water pressure, for the first time, is decoupled with the hydraulic gradient, owing to a newly developed permeameter with the controllable downstream hydraulic pressure in the laboratory. The results show that the permeability is significantly affected by the water pressure, and the effect is also predominantly dependent upon the Foam Injection Ratio (FIR). The initial permeability coefficient increases with an increasing water pressure, while the initial stable period duration decreases. The water-plugging structure formed by foam bubbles and sand particles is prone to be damaged under high water pressure. The underlying mechanism of water pressure in modifying the permeability of conditioned sands is also examined from a particle-scale perspective.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":"26 8","pages":""},"PeriodicalIF":3.6,"publicationDate":"2023-12-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139009190","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In this research, the potential benefits of using various structural types of cemented soil, including block-type, column-type, and wall-type, to reinforce the active zone behind a quay wall were investigated by experimental and numerical methods. The response of the quay wall and ground was analysed from aspects of soil movement, quay wall displacement, lateral earth pressure, and bending moment, and a close agreement between the experimental and numerical results was observed. Experimental and numerical results showed that the cemented soil effectively prevented potential deep soil sliding, and then lateral displacement of the quay wall and ground deformation was reduced. Among various structural patterns, the case with the block-type cemented soil exhibited smaller lateral earth pressure on the quay wall, while the case with the wall-type cemented soil more effectively reduced the bending moments and lateral displacements of the quay wall; therefore, wall-type cemented soil seems to be more favourable considering their improved performance under the same load intensities and excavation depth. This research provides a hint and guideline for the preliminary design of cemented soil-stabilised sheet pile quay structures in soft clay based on the lateral load-reduction effect of the varying structural types of the cemented soil.
{"title":"Behavior of an anchored sheet pile quay in soft clay reinforced by various structural types of cemented soil","authors":"Shengyuan Chen, Yunfei Guan, Jiqun Dai, Xun Han","doi":"10.1139/cgj-2023-0158","DOIUrl":"https://doi.org/10.1139/cgj-2023-0158","url":null,"abstract":"In this research, the potential benefits of using various structural types of cemented soil, including block-type, column-type, and wall-type, to reinforce the active zone behind a quay wall were investigated by experimental and numerical methods. The response of the quay wall and ground was analysed from aspects of soil movement, quay wall displacement, lateral earth pressure, and bending moment, and a close agreement between the experimental and numerical results was observed. Experimental and numerical results showed that the cemented soil effectively prevented potential deep soil sliding, and then lateral displacement of the quay wall and ground deformation was reduced. Among various structural patterns, the case with the block-type cemented soil exhibited smaller lateral earth pressure on the quay wall, while the case with the wall-type cemented soil more effectively reduced the bending moments and lateral displacements of the quay wall; therefore, wall-type cemented soil seems to be more favourable considering their improved performance under the same load intensities and excavation depth. This research provides a hint and guideline for the preliminary design of cemented soil-stabilised sheet pile quay structures in soft clay based on the lateral load-reduction effect of the varying structural types of the cemented soil.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":"14 8","pages":""},"PeriodicalIF":3.6,"publicationDate":"2023-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138978840","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Energy piles may be utilized for retaining structures, embankment reinforcements and building foundations on a slope. In this paper, a field test of a retaining energy pile subjected to horizontal loads has been carried out. The pile was subjected to thermal and thermo-mechanical loads before and after a pit excavation of 6 m deep, respectively. The non-uniform thermal and mechanical response at the cross-section due to heating and horizontal-load induced bending has been recorded. A simplified mechanism of the normal strain and stress at the pile cross-section was introduced to infer the thermo-mechanical behavior of the energy pile. The results show that the restraint of the retaining pile markedly decreased at the depth of 1.5 m and 4.0 m under the thermo-mechanical loads, compared to the case subjected to thermal load only. The bending behaviors (bending moment and horizontal displacement) indicate that there is a 10%-15% increase in bending moment when the energy pile was heated after the pit excavation. This effect needs to be considered at the most unfavorable section position. A possible positive effect is that heating up is beneficial for reducing the risk of tensile crack at the pile section due to the thermal compressive stress.
{"title":"Field test on cross-sectional behaviors of a retaining energy pile subjected to horizontal loads","authors":"Yang Zhou, Gangqiang Kong, Junjie Li","doi":"10.1139/cgj-2023-0270","DOIUrl":"https://doi.org/10.1139/cgj-2023-0270","url":null,"abstract":"Energy piles may be utilized for retaining structures, embankment reinforcements and building foundations on a slope. In this paper, a field test of a retaining energy pile subjected to horizontal loads has been carried out. The pile was subjected to thermal and thermo-mechanical loads before and after a pit excavation of 6 m deep, respectively. The non-uniform thermal and mechanical response at the cross-section due to heating and horizontal-load induced bending has been recorded. A simplified mechanism of the normal strain and stress at the pile cross-section was introduced to infer the thermo-mechanical behavior of the energy pile. The results show that the restraint of the retaining pile markedly decreased at the depth of 1.5 m and 4.0 m under the thermo-mechanical loads, compared to the case subjected to thermal load only. The bending behaviors (bending moment and horizontal displacement) indicate that there is a 10%-15% increase in bending moment when the energy pile was heated after the pit excavation. This effect needs to be considered at the most unfavorable section position. A possible positive effect is that heating up is beneficial for reducing the risk of tensile crack at the pile section due to the thermal compressive stress.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":"58 1","pages":""},"PeriodicalIF":3.6,"publicationDate":"2023-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138982012","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Tongwei Tao, W. Shi, Shaozhen Xiong, Fengting Liang, Jiayong Zhang
On August 28, 2017, the collapse of a mining slope in Pusa Village, Guizhou Province, China, released approximately 8,600 m3 of earth and rock, killing 35 people. This study, analyzes the deformation damage mechanism and progress of a simulated rainfall-induced mining slope collapse. The results show that the stress at the monitoring points changes under the action of mining, with the stress concentrated at the upper monitoring points of the mined-out area. A number of mining fractures are generated after the mining stress in the model is adjusted; these fractures were interconnected and gradually continued to the top of the slope as a consequence of rainwater infiltration. The simulation results demonstrate how, with continued mining of the coal seam and rainfall, the displacement value and range gradually increase, with maximum displacement occurring at the top of the mined-out area. The damage mechanism can be described as follows: subsurface mining disturbs the rock mass generating fractures; under rainfall, the fractures extend, further decreasing the rock strength and leading to a rise in water pressure inside the slope body; and, ultimately, deformation of the slope surface leads to collapse.
{"title":"Experimental study on deformation and failure of a mining slope under the action of rainfall","authors":"Tongwei Tao, W. Shi, Shaozhen Xiong, Fengting Liang, Jiayong Zhang","doi":"10.1139/cgj-2023-0298","DOIUrl":"https://doi.org/10.1139/cgj-2023-0298","url":null,"abstract":"On August 28, 2017, the collapse of a mining slope in Pusa Village, Guizhou Province, China, released approximately 8,600 m3 of earth and rock, killing 35 people. This study, analyzes the deformation damage mechanism and progress of a simulated rainfall-induced mining slope collapse. The results show that the stress at the monitoring points changes under the action of mining, with the stress concentrated at the upper monitoring points of the mined-out area. A number of mining fractures are generated after the mining stress in the model is adjusted; these fractures were interconnected and gradually continued to the top of the slope as a consequence of rainwater infiltration. The simulation results demonstrate how, with continued mining of the coal seam and rainfall, the displacement value and range gradually increase, with maximum displacement occurring at the top of the mined-out area. The damage mechanism can be described as follows: subsurface mining disturbs the rock mass generating fractures; under rainfall, the fractures extend, further decreasing the rock strength and leading to a rise in water pressure inside the slope body; and, ultimately, deformation of the slope surface leads to collapse.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":"19 10","pages":""},"PeriodicalIF":3.6,"publicationDate":"2023-12-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138978733","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The strength damage and deformation failure of frozen soil-rock mixture (FSRM) often restrict the safety of major engineering construction in cold areas or the spatial development of urban underground water-rich rock and soil masses. In order to investigate the uniaxial strength damage evolution and failure characteristics of FSRM under different loading rates (0.3, 0.6, 3, 6, 30, 60 mm·min-1) in the quasi-static range, resistivity monitoring and image recognition technology were used to study the time-stress-volumetric strain-resistivity changes. The results indicate that the peak stress, peak strain, initial yield modulus, and tangential modulus of FSRM increase rapidly before increasing slowly as the loading rate increases, and there are critical loading rates and post-peak failure phenomenon. Three distinct types of failure modes, bulge failure, oblique shear failure, and fragmentation failure, were observed at low (0.3-0.6 mm·min-1), medium (3-6 mm·min-1) and high loading rates (30-60 mm·min-1), respectively. The macroscopic failure of the FSRM at different loading rates arises from a combination of strain rate hardening of strength and damage softening of the structure. To predict the stress-strain characteristics at various loading rates, a damage prediction model with a damage variable correction factor considering residual strength was employed, based on the modified Duncan-Chang model and damage theory of electrical resistivity, and the predicted results were in good agreement with the experimental data.
{"title":"Study on Strength Damage Model Considering Resistivity and Failure Characteristics of the Frozen Soil-Rock Mixture Under Different Loading Rates","authors":"Shuangjiao Wang, Zhiqing Li, Zhiao Gao, Zhiyu Qi, Kai Sun, Ruilin Hu, Yingxin Zhou","doi":"10.1139/cgj-2023-0283","DOIUrl":"https://doi.org/10.1139/cgj-2023-0283","url":null,"abstract":"The strength damage and deformation failure of frozen soil-rock mixture (FSRM) often restrict the safety of major engineering construction in cold areas or the spatial development of urban underground water-rich rock and soil masses. In order to investigate the uniaxial strength damage evolution and failure characteristics of FSRM under different loading rates (0.3, 0.6, 3, 6, 30, 60 mm·min-1) in the quasi-static range, resistivity monitoring and image recognition technology were used to study the time-stress-volumetric strain-resistivity changes. The results indicate that the peak stress, peak strain, initial yield modulus, and tangential modulus of FSRM increase rapidly before increasing slowly as the loading rate increases, and there are critical loading rates and post-peak failure phenomenon. Three distinct types of failure modes, bulge failure, oblique shear failure, and fragmentation failure, were observed at low (0.3-0.6 mm·min-1), medium (3-6 mm·min-1) and high loading rates (30-60 mm·min-1), respectively. The macroscopic failure of the FSRM at different loading rates arises from a combination of strain rate hardening of strength and damage softening of the structure. To predict the stress-strain characteristics at various loading rates, a damage prediction model with a damage variable correction factor considering residual strength was employed, based on the modified Duncan-Chang model and damage theory of electrical resistivity, and the predicted results were in good agreement with the experimental data.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":"28 18","pages":""},"PeriodicalIF":3.6,"publicationDate":"2023-12-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138589245","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The influence of bitumen coating on the development of unit shaft resistance along driven steel and pre-cast concrete piles resulting from subsiding surrounding soft soil (Gyttja) induced by fill placement at terrain was investigated. All piles were instrumented with conventional discrete-point vibrating wire strain gauges and distributed fiber optic sensors to achieve high resolution strain measurements. The magnitude of the mobilised unit shaft resistance along uncoated piles was observed to be primarily related to an increase in effective stress resulting from the dissipation of excess pore water pressures. The unit shaft resistance along bitumen coated piles was found to be primarily related to the rate of relative movement between pile and soil, which highlights the effectiveness of bitumen coating in reducing shaft resistance.
{"title":"The development of unit shaft resistance along driven piles in subsiding soil","authors":"J. Kania, Kenny Kataoka Sorensen, B. Fellenius","doi":"10.1139/cgj-2022-0694","DOIUrl":"https://doi.org/10.1139/cgj-2022-0694","url":null,"abstract":"The influence of bitumen coating on the development of unit shaft resistance along driven steel and pre-cast concrete piles resulting from subsiding surrounding soft soil (Gyttja) induced by fill placement at terrain was investigated. All piles were instrumented with conventional discrete-point vibrating wire strain gauges and distributed fiber optic sensors to achieve high resolution strain measurements. The magnitude of the mobilised unit shaft resistance along uncoated piles was observed to be primarily related to an increase in effective stress resulting from the dissipation of excess pore water pressures. The unit shaft resistance along bitumen coated piles was found to be primarily related to the rate of relative movement between pile and soil, which highlights the effectiveness of bitumen coating in reducing shaft resistance.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":"45 26","pages":""},"PeriodicalIF":3.6,"publicationDate":"2023-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138597626","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Weiping Wang, Xi-An Li, Haoyang Dong, Hao Chai, Wenfu Yang
The vast majority of geological disasters in loess-covered areas are caused by seepage erosion in loess. Therefore, this paper focuses on the microscopic mechanism of loess seepage erosion, and constructs a loess microstructure model based on particle "core+coat". On this basis, the SEM photos are imported into COMSOL to simulate the micro-scale seepage in the pore domain. Through the actual permeability test, combined with the micro-quantitative information obtained by IPP(Image-pro-plus) and Arcgis, the micro-factors affecting loess permeability are quantitatively analyzed by grey relational analysis. The results show that the dry density affects the porosity of loess and ultimately determines the permeability of loess. Different pore types and proportions lead to different seepage erosion of loess. The erosion process mainly occurs at the junction of pores. The sudden increase of velocity, pressure drop and maximum shear rate at the throat indicate that this area is the main action area of loess seepage erosion. The research results of this paper provide an important theoretical basis for the research and prevention of geological disasters and engineering diseases related to seepage deformation and failure in loess area.
{"title":"Micromechanical study of loess permeability and seepage erosion based on microstructure functional basic unit and seepage simulation in pore domain","authors":"Weiping Wang, Xi-An Li, Haoyang Dong, Hao Chai, Wenfu Yang","doi":"10.1139/cgj-2023-0281","DOIUrl":"https://doi.org/10.1139/cgj-2023-0281","url":null,"abstract":"The vast majority of geological disasters in loess-covered areas are caused by seepage erosion in loess. Therefore, this paper focuses on the microscopic mechanism of loess seepage erosion, and constructs a loess microstructure model based on particle \"core+coat\". On this basis, the SEM photos are imported into COMSOL to simulate the micro-scale seepage in the pore domain. Through the actual permeability test, combined with the micro-quantitative information obtained by IPP(Image-pro-plus) and Arcgis, the micro-factors affecting loess permeability are quantitatively analyzed by grey relational analysis. The results show that the dry density affects the porosity of loess and ultimately determines the permeability of loess. Different pore types and proportions lead to different seepage erosion of loess. The erosion process mainly occurs at the junction of pores. The sudden increase of velocity, pressure drop and maximum shear rate at the throat indicate that this area is the main action area of loess seepage erosion. The research results of this paper provide an important theoretical basis for the research and prevention of geological disasters and engineering diseases related to seepage deformation and failure in loess area.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":"84 6","pages":""},"PeriodicalIF":3.6,"publicationDate":"2023-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138595893","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jun Wang, Guojin Lin, Ning Tian, Kun Feng, Guowne Xu, Xiong-yu Hu, Zi-quan Chen, Chuan He
This paper aims at addressing the face failure of earth pressure balance (EPB) shield tunnels in dry dense sand by model tests and discrete element method (DEM) models. The model tests incorporated a miniature EPB shield which could fully reproduce the real tunnel construction of excavation and support. DEM models simulating the model tests were developed to capture the underlying face failure mechanism. Results show that both the limit support pressure obtained at chamber board and tunnel face increase with increasing C/D (C is tunnel buried depth, D is tunnel diameter). The ratio of the former to the latter approximates 0.60 due to the soil retaining of cutterhead panel, and it is independent of C/D. The local face failure initializes around tunnel face and develops directly to the global failure outcropping the ground surface in one phase with C/D≤1.0, while the local failure develops to the global failure in three phases with C/D=2.0 due to the soil arching evolution. The soil arching gets weaker when it propagates upward, and the horizontal stress concentration in the longitudinal direction is stronger than the transverse direction due to the difference of arch foot.
{"title":"Face failure of EPB shield tunnels in dry dense sand: a model test and DEM study","authors":"Jun Wang, Guojin Lin, Ning Tian, Kun Feng, Guowne Xu, Xiong-yu Hu, Zi-quan Chen, Chuan He","doi":"10.1139/cgj-2023-0072","DOIUrl":"https://doi.org/10.1139/cgj-2023-0072","url":null,"abstract":"This paper aims at addressing the face failure of earth pressure balance (EPB) shield tunnels in dry dense sand by model tests and discrete element method (DEM) models. The model tests incorporated a miniature EPB shield which could fully reproduce the real tunnel construction of excavation and support. DEM models simulating the model tests were developed to capture the underlying face failure mechanism. Results show that both the limit support pressure obtained at chamber board and tunnel face increase with increasing C/D (C is tunnel buried depth, D is tunnel diameter). The ratio of the former to the latter approximates 0.60 due to the soil retaining of cutterhead panel, and it is independent of C/D. The local face failure initializes around tunnel face and develops directly to the global failure outcropping the ground surface in one phase with C/D≤1.0, while the local failure develops to the global failure in three phases with C/D=2.0 due to the soil arching evolution. The soil arching gets weaker when it propagates upward, and the horizontal stress concentration in the longitudinal direction is stronger than the transverse direction due to the difference of arch foot.","PeriodicalId":9382,"journal":{"name":"Canadian Geotechnical Journal","volume":"44 16","pages":""},"PeriodicalIF":3.6,"publicationDate":"2023-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138597793","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"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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