Pub Date : 2024-05-04DOI: 10.1007/s11440-024-02342-8
Johannes Pistrol, Mario Hager, Fritz Kopf, Dietmar Adam
The compaction success of vibratory roller compaction can be assessed by systems for continuous compaction control (CCC) or intelligent compaction (IC) which calculate soil stiffness-proportional quantities based on measurements of the motion behavior of the vibrating drum. However, state-of-the-art intelligent compaction meter values (ICMV) do not only depend on the stiffness of the soil but are also strongly influenced by machine and process parameters. In this paper, the methodology for determining an advanced ICMV is presented, in which the mechanical properties of the soil, the process parameters and geometric relationships in the contact area between the drum and the soil are directly included in the calculation. The methodology is explained on the example of measurement data from a compaction test conducted on sandy gravel with a heavy single-drum roller. The results of the novel ICMV are compared with those of the most widely used IC systems.
{"title":"An advanced ICMV for vibratory roller compaction","authors":"Johannes Pistrol, Mario Hager, Fritz Kopf, Dietmar Adam","doi":"10.1007/s11440-024-02342-8","DOIUrl":"https://doi.org/10.1007/s11440-024-02342-8","url":null,"abstract":"<p>The compaction success of vibratory roller compaction can be assessed by systems for continuous compaction control (CCC) or intelligent compaction (IC) which calculate soil stiffness-proportional quantities based on measurements of the motion behavior of the vibrating drum. However, state-of-the-art intelligent compaction meter values (ICMV) do not only depend on the stiffness of the soil but are also strongly influenced by machine and process parameters. In this paper, the methodology for determining an advanced ICMV is presented, in which the mechanical properties of the soil, the process parameters and geometric relationships in the contact area between the drum and the soil are directly included in the calculation. The methodology is explained on the example of measurement data from a compaction test conducted on sandy gravel with a heavy single-drum roller. The results of the novel ICMV are compared with those of the most widely used IC systems.</p>","PeriodicalId":49308,"journal":{"name":"Acta Geotechnica","volume":null,"pages":null},"PeriodicalIF":5.7,"publicationDate":"2024-05-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140885146","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-05-03DOI: 10.1007/s11440-024-02313-z
Hijran Aljanabi, Reza Imam, Mohammad Khorand
Most previous experimental studies on the behavior of piles subjected to lateral loading have focused on testing model piles embedded in dry or fully saturated soils, and little attention has been paid to the impact of the soil partial saturation on the results. This paper presents results of 1g model tests on a single pile embedded in dry and unsaturated sand subjected to two-way constant displacement amplitude loading. The tests were aimed at examination of the effects of degree of soil saturation and density on the pile internal forces and lateral capacity and the deformation patterns of the adjacent soils. Five degrees of saturation (Sr = 0, 10, 20, 35 and 50%) for loose and medium-dense sand (Dr = 20% and 50%) were chosen and a 65-mm-diameter and 900-mm-long polyethylene model pile was used. Test results indicated that at each soil relative density, the pile head horizontal load, and the maximum bending moment, shear force, and soil reaction in the pile increase with increase in the degree of saturation up to about Sr = 35%. However, further increase in Sr led to decrease in these values. Moreover, the cyclic loading led to depressions in the surface of the dry sand and bulging associated with soil–pile separation in the unsaturated sand. For the model testing conditions used, results indicated that the sand degree of saturation can have a greater impact on the pile behavior than its density.
{"title":"Behavior of model pile in unsaturated soil subjected to cyclic loading","authors":"Hijran Aljanabi, Reza Imam, Mohammad Khorand","doi":"10.1007/s11440-024-02313-z","DOIUrl":"https://doi.org/10.1007/s11440-024-02313-z","url":null,"abstract":"<p>Most previous experimental studies on the behavior of piles subjected to lateral loading have focused on testing model piles embedded in dry or fully saturated soils, and little attention has been paid to the impact of the soil partial saturation on the results. This paper presents results of 1g model tests on a single pile embedded in dry and unsaturated sand subjected to two-way constant displacement amplitude loading. The tests were aimed at examination of the effects of degree of soil saturation and density on the pile internal forces and lateral capacity and the deformation patterns of the adjacent soils. Five degrees of saturation (<i>S</i><sub><i>r</i></sub> = 0, 10, 20, 35 and 50%) for loose and medium-dense sand (<i>D</i><sub>r</sub> = 20% and 50%) were chosen and a 65-mm-diameter and 900-mm-long polyethylene model pile was used. Test results indicated that at each soil relative density, the pile head horizontal load, and the maximum bending moment, shear force, and soil reaction in the pile increase with increase in the degree of saturation up to about <i>S</i><sub><i>r</i></sub> = 35%. However, further increase in <i>S</i><sub><i>r</i></sub> led to decrease in these values. Moreover, the cyclic loading led to depressions in the surface of the dry sand and bulging associated with soil–pile separation in the unsaturated sand. For the model testing conditions used, results indicated that the sand degree of saturation can have a greater impact on the pile behavior than its density.</p>","PeriodicalId":49308,"journal":{"name":"Acta Geotechnica","volume":null,"pages":null},"PeriodicalIF":5.7,"publicationDate":"2024-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140885299","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-28DOI: 10.1007/s11440-024-02301-3
Zohreh Emmarloo, Mohsen Karrabi, Bahar Shahnavaz, Asal Masoumi Khameneh, Philippe Sechet
Petroleum hydrocarbons (PHCs) including phenolic compounds cause major environmental impacts just the once released into soils or groundwater. Among the core technologies, permeable reactive barriers (PRBs) have been so far exploited to contain and control such contaminants within the subsurface layers of the soil. Against this background, the present study investigated flow-biofilm interactions in a laboratory-scale permeable reactive bio-barrier (PRBB). To this end, an experimental setup was firstly built by embedding pressure measurement ports, at 10 cm intervals, onto a cylindrical column with a diameter of 57 mm and a height of 50 cm, and then filled with a porous medium, made up of sand with an average diameter of 1.78 mm. The bacterium, Pseudomonas putida (P. putida), was also utilized to generate the biofilm. Afterward, phenol-containing water was passed through the column at a rate of 2 L/h under a hydrodynamic laminar flow regime. Experimental evidence showed that the biofilm formed by bacterial growth could shrink the bio-barrier (BB) porosity from 0.35 to 0.07, instigating a drop by 590 and 840 times in the hydraulic pressure across the column at phenol concentrations, 200 and 400 mg/L, respectively. The desired biofilm additionally managed to remove 40 and 30% of phenol at concentrations of 200 and 400 mg/L, in that order. Exploring the variations in hydraulic conductivity in different layers plus the microscopic images further demonstrated that the biofilm created at phenol concentration of 200 mg/L seemed to be much stronger and even more stable, compared to the one at 400 mg/L. This was traceable to the better adaptation of P. putida to lower concentrations of phenol as the carbon source. Furthermore, the study results established that the given PRBB could help decompose only a small portion of phenol, but outperformed in terms of containing and controlling this contaminant through reducing hydraulic conductivity.
{"title":"Performance evaluation of an ex situ permeable reactive bio-barrier in phenol-contaminated water containment and remediation under a laminar flow regime","authors":"Zohreh Emmarloo, Mohsen Karrabi, Bahar Shahnavaz, Asal Masoumi Khameneh, Philippe Sechet","doi":"10.1007/s11440-024-02301-3","DOIUrl":"https://doi.org/10.1007/s11440-024-02301-3","url":null,"abstract":"<p>Petroleum hydrocarbons (PHCs) including phenolic compounds cause major environmental impacts just the once released into soils or groundwater. Among the core technologies, permeable reactive barriers (PRBs) have been so far exploited to contain and control such contaminants within the subsurface layers of the soil. Against this background, the present study investigated flow-biofilm interactions in a laboratory-scale permeable reactive bio-barrier (PRBB). To this end, an experimental setup was firstly built by embedding pressure measurement ports, at 10 cm intervals, onto a cylindrical column with a diameter of 57 mm and a height of 50 cm, and then filled with a porous medium, made up of sand with an average diameter of 1.78 mm. The bacterium, <i>Pseudomonas putida</i> (<i>P. putida</i>), was also utilized to generate the biofilm. Afterward, phenol-containing water was passed through the column at a rate of 2 L/h under a hydrodynamic laminar flow regime. Experimental evidence showed that the biofilm formed by bacterial growth could shrink the bio-barrier (BB) porosity from 0.35 to 0.07, instigating a drop by 590 and 840 times in the hydraulic pressure across the column at phenol concentrations, 200 and 400 mg/L, respectively. The desired biofilm additionally managed to remove 40 and 30% of phenol at concentrations of 200 and 400 mg/L, in that order. Exploring the variations in hydraulic conductivity in different layers plus the microscopic images further demonstrated that the biofilm created at phenol concentration of 200 mg/L seemed to be much stronger and even more stable, compared to the one at 400 mg/L. This was traceable to the better adaptation of <i>P. putida</i> to lower concentrations of phenol as the carbon source. Furthermore, the study results established that the given PRBB could help decompose only a small portion of phenol, but outperformed in terms of containing and controlling this contaminant through reducing hydraulic conductivity.</p><h3 data-test=\"abstract-sub-heading\">Graphical Abstract</h3>","PeriodicalId":49308,"journal":{"name":"Acta Geotechnica","volume":null,"pages":null},"PeriodicalIF":5.7,"publicationDate":"2024-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140809052","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-26DOI: 10.1007/s11440-024-02293-0
Yang Xiao, Jian Hu, Jinquan Shi, Lei Zhang, Hanlong Liu
Microbially induced calcium carbonate precipitation (MICP) technology is an emerging and environmentally sustainable method for improving the strength and stiffness of soil. Specifically, this innovative approach has gained favor in marine engineering due to the advantaged compatibility between precipitated calcium carbonate induced by MICP and coral sand. Sand containing fines is susceptible to liquefy. Whereas, the impact of fines contents on cyclic behavior of MICP-treated calcareous sand remains uncertain. Consequently, this technical note aims to investigate the liquefaction behavior of biocemented calcareous silty sand by conducting undrained cyclic triaxial shear tests and microscopic analysis. The results revealed the patterns of the excess pore water pressure curves and cyclic deformation characteristics as the fines contents increased. The liquefaction resistance of biocemented sand initially decreases with the addition of fines but subsequently exhibits an increasing trend. Microscopic analysis showed that at the cementation level with the cementation solution concentration of 1 mol/L, the calcium carbonate crystals are mainly attached to the surface of sand grains and this pattern does not directly affect the force chain.
{"title":"Undrained cyclic responses of biocemented calcareous silty sand","authors":"Yang Xiao, Jian Hu, Jinquan Shi, Lei Zhang, Hanlong Liu","doi":"10.1007/s11440-024-02293-0","DOIUrl":"10.1007/s11440-024-02293-0","url":null,"abstract":"<div><p>Microbially induced calcium carbonate precipitation (MICP) technology is an emerging and environmentally sustainable method for improving the strength and stiffness of soil. Specifically, this innovative approach has gained favor in marine engineering due to the advantaged compatibility between precipitated calcium carbonate induced by MICP and coral sand. Sand containing fines is susceptible to liquefy. Whereas, the impact of fines contents on cyclic behavior of MICP-treated calcareous sand remains uncertain. Consequently, this technical note aims to investigate the liquefaction behavior of biocemented calcareous silty sand by conducting undrained cyclic triaxial shear tests and microscopic analysis. The results revealed the patterns of the excess pore water pressure curves and cyclic deformation characteristics as the fines contents increased. The liquefaction resistance of biocemented sand initially decreases with the addition of fines but subsequently exhibits an increasing trend. Microscopic analysis showed that at the cementation level with the cementation solution concentration of 1 mol/L, the calcium carbonate crystals are mainly attached to the surface of sand grains and this pattern does not directly affect the force chain.</p></div>","PeriodicalId":49308,"journal":{"name":"Acta Geotechnica","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-04-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140806763","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-25DOI: 10.1007/s11440-024-02261-8
Gerd Gudehus, Christian Karcher
We outlined earlier in this journal by means of finite element simulations how patterns of normal faults arise by a synsedimentary tectonic extension, and how clay smears evolve therein. In the present paper, we show how hydraulic breakthroughs of clay smears can arise so that water, gas and mud rise in faults. Mechanical properties of sand and clay are introduced first for the stable range and then for rupture and internal erosion. Our numerical simulations for the evolution of normal faults and clay smears are discussed in light of critical phenomena. Water assembled in an open-cast mine about 20 years ago as the critical hydraulic gradient in a clay smear dropped to the actual one due to the rapid excavation-induced deformation. The latter led to a critical point under an excavation the slope of which was parallel to a nearby normal fault. Clay smears can also break by earthquakes so that the critical hydraulic gradient drops to the actual one caused by methane with an excess pressure. This can lead to hydraulic breakthroughs and cold eruptions at outcrops of faults.
{"title":"Hydraulic breakthrough of clay smears due to technical and natural actions","authors":"Gerd Gudehus, Christian Karcher","doi":"10.1007/s11440-024-02261-8","DOIUrl":"10.1007/s11440-024-02261-8","url":null,"abstract":"<div><p>We outlined earlier in this journal by means of finite element simulations how patterns of normal faults arise by a synsedimentary tectonic extension, and how clay smears evolve therein. In the present paper, we show how hydraulic breakthroughs of clay smears can arise so that water, gas and mud rise in faults. Mechanical properties of sand and clay are introduced first for the stable range and then for rupture and internal erosion. Our numerical simulations for the evolution of normal faults and clay smears are discussed in light of critical phenomena. Water assembled in an open-cast mine about 20 years ago as the critical hydraulic gradient in a clay smear dropped to the actual one due to the rapid excavation-induced deformation. The latter led to a critical point under an excavation the slope of which was parallel to a nearby normal fault. Clay smears can also break by earthquakes so that the critical hydraulic gradient drops to the actual one caused by methane with an excess pressure. This can lead to hydraulic breakthroughs and cold eruptions at outcrops of faults.</p></div>","PeriodicalId":49308,"journal":{"name":"Acta Geotechnica","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11440-024-02261-8.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140655881","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-25DOI: 10.1007/s11440-024-02245-8
Zi Ye, Yonghui Chen, Geng Chen, Jiangwei Shi, Nan Hu, Minguo Lin
The groundwater level divides the soils into unsaturated zone and saturated zone, imposing an indispensable effect on the soil–pile interaction behavior. In this work, the groundwater level is introduced into soil–pile group interaction models for advancing the dynamic impedance research of pile groups. The motion equation of pile groups is modeled by the finite element method. The vibration solution of soils considering the groundwater level is solved via the precise integration method, which is utilized as the kernel function to construct the boundary integral equation. The coupled finite element method (FEM) and boundary element method (BEM) establishes the unsaturated soil–pile group interaction equation, which is further solved based on the soil–pile compatibility condition. After confirming the reliability of the above theory, parametric analyses are provided to discuss the effect of a series of key parameters on the impedance function of pile groups.
{"title":"Vertical dynamic impedance of pile groups embedded in soils considering the groundwater level","authors":"Zi Ye, Yonghui Chen, Geng Chen, Jiangwei Shi, Nan Hu, Minguo Lin","doi":"10.1007/s11440-024-02245-8","DOIUrl":"10.1007/s11440-024-02245-8","url":null,"abstract":"<div><p>The groundwater level divides the soils into unsaturated zone and saturated zone, imposing an indispensable effect on the soil–pile interaction behavior. In this work, the groundwater level is introduced into soil–pile group interaction models for advancing the dynamic impedance research of pile groups. The motion equation of pile groups is modeled by the finite element method. The vibration solution of soils considering the groundwater level is solved via the precise integration method, which is utilized as the kernel function to construct the boundary integral equation. The coupled finite element method (FEM) and boundary element method (BEM) establishes the unsaturated soil–pile group interaction equation, which is further solved based on the soil–pile compatibility condition. After confirming the reliability of the above theory, parametric analyses are provided to discuss the effect of a series of key parameters on the impedance function of pile groups.</p></div>","PeriodicalId":49308,"journal":{"name":"Acta Geotechnica","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140655829","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-25DOI: 10.1007/s11440-024-02307-x
Diana Bianchi, Domenico Gallipoli, R. Bovolenta, Martino Leoni
{"title":"Long-term “memory” of extraordinary climatic seasons in the hysteretic seepage of an unsaturated infinite slope","authors":"Diana Bianchi, Domenico Gallipoli, R. Bovolenta, Martino Leoni","doi":"10.1007/s11440-024-02307-x","DOIUrl":"https://doi.org/10.1007/s11440-024-02307-x","url":null,"abstract":"","PeriodicalId":49308,"journal":{"name":"Acta Geotechnica","volume":null,"pages":null},"PeriodicalIF":5.7,"publicationDate":"2024-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140656065","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-25DOI: 10.1007/s11440-024-02334-8
Dae-Sung Cho, Jaehong Kim
{"title":"Stability of the front wall and the horizontal behavior of composite reinforced-earth retaining walls","authors":"Dae-Sung Cho, Jaehong Kim","doi":"10.1007/s11440-024-02334-8","DOIUrl":"https://doi.org/10.1007/s11440-024-02334-8","url":null,"abstract":"","PeriodicalId":49308,"journal":{"name":"Acta Geotechnica","volume":null,"pages":null},"PeriodicalIF":5.7,"publicationDate":"2024-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140656142","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The presence of abundant clay components and microporous structure in shale results in its high hydrophilicity, making a water-rich environment inevitable in petroleum exploration projects. Therefore, it is crucial to consider the influence of bedding structure, moisture content, confining pressure, and their combined effects on the geomechanical properties of shale. This article aims to investigate the mechanical properties of deep shale under varying water content conditions, elucidate the failure mode and failure mechanism of shale in actual engineering scenarios, and explores the interplay between stress, structure, moisture content, and other factors on its mechanical properties. The evaluation of wellbore stability and fracture propagation effects is proposed based on laboratory experiments using triaxial stress and strain data, along with the application of energy evolution theory. The experimental procedures encompass an analysis of shale's microscopic components and structure, as well as anisotropic shale triaxial compression tests conducted under different moisture contents and confining pressures. The results demonstrate that shale exhibits dense pores in its microstructure and displays pronounced anisotropic characteristics in its macrostructure. The presence of water within these pores, combined with the in situ stress within the formation, significantly influences the mechanical properties of shale. This anisotropy decreases with increasing moisture content, but the mechanical performance still decreases. Under triaxial compression conditions, the increase in confining pressure to some extent enhances the anisotropy of shale's deformation characteristics, which is related to the failure modes of shale. However, the detrimental effect of moisture content on shale's mechanical properties still persists. In order to quantify the impact of these factors, this study utilizes the elastic modulus as an indicator of the coupling effect. It combines the triaxial strain curve obtained from laboratory tests and proposes an evaluation index for shale mechanical properties based on the energy evolution theory. This index is suitable for assessing wellbore stability (the stability index called SIr) and crack expansion (the brittleness index called BIr). The calculation results reveal that, during the wellbore drilling process, excavating parallel to the direction of shale bedding while maintaining low moisture content and high confining pressure yields a higher SIr value, indicating better wellbore stability. On the other hand, during reservoir fracturing, fracturing perpendicular to the shale bedding direction and maintaining low confining pressure and moisture content result in a smaller BIr value. This approach is more beneficial for the expansion of shale fracture network in engineering.
页岩中含有丰富的粘土成分和微孔结构,因此亲水性很强,在石油勘探项目中,富水环境是不可避免的。因此,考虑垫层结构、含水率、约束压力及其综合效应对页岩地质力学性能的影响至关重要。本文旨在研究不同含水率条件下深层页岩的力学性能,阐明页岩在实际工程场景中的破坏模式和破坏机理,探讨应力、结构、含水率等因素对其力学性能的相互影响。利用三轴应力和应变数据进行实验室实验,并应用能量演化理论,提出了井筒稳定性和裂缝扩展效应的评估方法。实验程序包括分析页岩的微观成分和结构,以及在不同含水量和约束压力下进行的各向异性页岩三轴压缩试验。结果表明,页岩的微观结构中存在致密的孔隙,其宏观结构具有明显的各向异性特征。这些孔隙中水分的存在,加上地层中的原位应力,对页岩的机械特性产生了重大影响。这种各向异性会随着含水量的增加而减弱,但机械性能仍会下降。在三轴压缩条件下,约束压力的增加在一定程度上增强了页岩变形特征的各向异性,这与页岩的破坏模式有关。然而,含水量对页岩力学性能的不利影响依然存在。为了量化这些因素的影响,本研究利用弹性模量作为耦合效应的指标。它结合实验室测试获得的三轴应变曲线,提出了基于能量演化理论的页岩力学性能评价指标。该指数适用于评估井筒稳定性(稳定性指数 SIr)和裂缝扩展性(脆性指数 BIr)。计算结果表明,在井筒钻进过程中,在保持低含水率和高约束压力的情况下,平行于页岩垫层方向开挖可获得较高的 SIr 值,表明井筒稳定性较好。另一方面,在储层压裂过程中,垂直于页岩垫层方向进行压裂,并保持较低的封闭压力和含水量,会产生较小的 BIr 值。这种方法更有利于工程中页岩裂缝网络的扩展。
{"title":"Study on failure characteristics and evaluation index of aquifer shale based on energy evolution","authors":"Xian-yin Qi, Dian-dong Geng, Meng-yao Feng, Ming-zhe Xu","doi":"10.1007/s11440-024-02263-6","DOIUrl":"10.1007/s11440-024-02263-6","url":null,"abstract":"<div><p>The presence of abundant clay components and microporous structure in shale results in its high hydrophilicity, making a water-rich environment inevitable in petroleum exploration projects. Therefore, it is crucial to consider the influence of bedding structure, moisture content, confining pressure, and their combined effects on the geomechanical properties of shale. This article aims to investigate the mechanical properties of deep shale under varying water content conditions, elucidate the failure mode and failure mechanism of shale in actual engineering scenarios, and explores the interplay between stress, structure, moisture content, and other factors on its mechanical properties. The evaluation of wellbore stability and fracture propagation effects is proposed based on laboratory experiments using triaxial stress and strain data, along with the application of energy evolution theory. The experimental procedures encompass an analysis of shale's microscopic components and structure, as well as anisotropic shale triaxial compression tests conducted under different moisture contents and confining pressures. The results demonstrate that shale exhibits dense pores in its microstructure and displays pronounced anisotropic characteristics in its macrostructure. The presence of water within these pores, combined with the in situ stress within the formation, significantly influences the mechanical properties of shale. This anisotropy decreases with increasing moisture content, but the mechanical performance still decreases. Under triaxial compression conditions, the increase in confining pressure to some extent enhances the anisotropy of shale's deformation characteristics, which is related to the failure modes of shale. However, the detrimental effect of moisture content on shale's mechanical properties still persists. In order to quantify the impact of these factors, this study utilizes the elastic modulus as an indicator of the coupling effect. It combines the triaxial strain curve obtained from laboratory tests and proposes an evaluation index for shale mechanical properties based on the energy evolution theory. This index is suitable for assessing wellbore stability (the stability index called <i>SI</i><sub><i>r</i></sub>) and crack expansion (the brittleness index called <i>BI</i><sub>r</sub>). The calculation results reveal that, during the wellbore drilling process, excavating parallel to the direction of shale bedding while maintaining low moisture content and high confining pressure yields a higher <i>SI</i><sub><i>r</i></sub> value, indicating better wellbore stability. On the other hand, during reservoir fracturing, fracturing perpendicular to the shale bedding direction and maintaining low confining pressure and moisture content result in a smaller <i>BI</i><sub>r</sub> value. This approach is more beneficial for the expansion of shale fracture network in engineering.</p></div>","PeriodicalId":49308,"journal":{"name":"Acta Geotechnica","volume":null,"pages":null},"PeriodicalIF":5.6,"publicationDate":"2024-04-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s11440-024-02263-6.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140658371","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-04-22DOI: 10.1007/s11440-024-02336-6
Emelyne Routier, Marie Guenther, Marco Terzariol
Marine plastic pollution has become a major concern as it threatens marine life and human health. Most of the plastic that enters the ocean is either consumed by animals and/or trapped in sediments. However, there is little information on how sediment properties might be affected. In this article, we explore the impact of microplastic inclusions in marine settings by using PVC plastic chips and two soil samples as analogues. We conducted a comprehensive experimental study to investigate changes in compressibility, strength, stiffness, thermal and hydraulic conductivity, and particle migration by varying plastic content. Results show that as low as 1% of plastic content by volume can lead to irreversible consequences in sediment behavior while coarse particles display a heightened sensitivity than pure fines. As plastic content in sediment increases year-by-year, we anticipate significant repercussions in marine life, the future landscape of the seafloor and subsurface phenomena.
{"title":"The impact of large microplastics on the physical behavior of soils: implications to marine sediments","authors":"Emelyne Routier, Marie Guenther, Marco Terzariol","doi":"10.1007/s11440-024-02336-6","DOIUrl":"https://doi.org/10.1007/s11440-024-02336-6","url":null,"abstract":"<p>Marine plastic pollution has become a major concern as it threatens marine life and human health. Most of the plastic that enters the ocean is either consumed by animals and/or trapped in sediments. However, there is little information on how sediment properties might be affected. In this article, we explore the impact of microplastic inclusions in marine settings by using PVC plastic chips and two soil samples as analogues. We conducted a comprehensive experimental study to investigate changes in compressibility, strength, stiffness, thermal and hydraulic conductivity, and particle migration by varying plastic content. Results show that as low as 1% of plastic content by volume can lead to irreversible consequences in sediment behavior while coarse particles display a heightened sensitivity than pure fines. As plastic content in sediment increases year-by-year, we anticipate significant repercussions in marine life, the future landscape of the seafloor and subsurface phenomena.</p>","PeriodicalId":49308,"journal":{"name":"Acta Geotechnica","volume":null,"pages":null},"PeriodicalIF":5.7,"publicationDate":"2024-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140637297","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}