A system for preparing soil specimens subjected to drying-wetting cycles whilst under vertical confining pressures is introduced with Clayey soil specimens subjected to different drying-wetting histories, then the relative performance tested using consolidated undrained triaxial shear tests. Meanwhile, their soil water retention properties were also measured. The experimental results indicate that drying-wetting cycles lead to a rise in the matric suction for soil with high moisture content, and the decrease of matric suction for soil with low moisture content. Partly owing to the higher pore water pressure, peak shear strength reduces gradually during drying-wetting cycles. The impacts of drying-wetting cycles on hydro-mechanical properties of soil specimens during the first cycle are larger than those during the second and the third cycles as the highest matric suction of soil occurs during the first cycle. Vertical confining pressure is shown to limit the impact of drying-wetting cycles on the hydro-mechanical properties of soil effectively because of its restricting effects on the volumetric deformation of soil during the cycles.
{"title":"Mechanical behaviour of soil under drying-wetting cycles and vertical confining pressure","authors":"Zhiming Chao, Danda Shi, G. Fowmes","doi":"10.1680/jenge.22.00048","DOIUrl":"https://doi.org/10.1680/jenge.22.00048","url":null,"abstract":"A system for preparing soil specimens subjected to drying-wetting cycles whilst under vertical confining pressures is introduced with Clayey soil specimens subjected to different drying-wetting histories, then the relative performance tested using consolidated undrained triaxial shear tests. Meanwhile, their soil water retention properties were also measured. The experimental results indicate that drying-wetting cycles lead to a rise in the matric suction for soil with high moisture content, and the decrease of matric suction for soil with low moisture content. Partly owing to the higher pore water pressure, peak shear strength reduces gradually during drying-wetting cycles. The impacts of drying-wetting cycles on hydro-mechanical properties of soil specimens during the first cycle are larger than those during the second and the third cycles as the highest matric suction of soil occurs during the first cycle. Vertical confining pressure is shown to limit the impact of drying-wetting cycles on the hydro-mechanical properties of soil effectively because of its restricting effects on the volumetric deformation of soil during the cycles.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2023-03-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48096807","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}
E. Hellawell, S. Hughes, D. Hajializadeh, Sarah Cook, Richard Brinkworth
Meeting the 2050 net zero carbon target requires all sectors of civil engineering to include the reduction of carbon emissions within their designs. This paper presents the development and early achievements of a Carbon Reduction Design Tool (CReDiT) for excavation and clean cover remediation of brownfield sites. The tool was developed for this remediation technique as it is the dominant remediation method used on residential redevelopment sites within the UK. CReDiT determines carbon emissions from the complex processes involved in this form of remediation, e.g., excavation of soil, use of raw materials, transport of material and the waste, recycling and reuse of materials. The application of the tool, to evaluate carbon emissions from excavation and cover remediation options applied to a former landfill site, is presented. In this case study, CReDiT quantifies carbon emissions and material volumes for proposed design options. It also demonstrates the carbon savings that can be made by the effective reuse of material onsite and the contribution of waste materials to carbon emissions. Additional carbon savings through the reuse or recycling of carbon-rich or valuable materials are also calculated. The use of CReDiT has led to a rethink of remediation excavation and cover design. Excavated /waste materials are re-evaluated as a resource; material reuse options are assessed and carbon reduction is included in the design process. This leads to more sustainable remediation solutions.
{"title":"Carbon Reduction Design Tool (CReDiT) for excavation and clean cover remediation","authors":"E. Hellawell, S. Hughes, D. Hajializadeh, Sarah Cook, Richard Brinkworth","doi":"10.1680/jenge.22.00128","DOIUrl":"https://doi.org/10.1680/jenge.22.00128","url":null,"abstract":"Meeting the 2050 net zero carbon target requires all sectors of civil engineering to include the reduction of carbon emissions within their designs. This paper presents the development and early achievements of a Carbon Reduction Design Tool (CReDiT) for excavation and clean cover remediation of brownfield sites. The tool was developed for this remediation technique as it is the dominant remediation method used on residential redevelopment sites within the UK. CReDiT determines carbon emissions from the complex processes involved in this form of remediation, e.g., excavation of soil, use of raw materials, transport of material and the waste, recycling and reuse of materials. The application of the tool, to evaluate carbon emissions from excavation and cover remediation options applied to a former landfill site, is presented. In this case study, CReDiT quantifies carbon emissions and material volumes for proposed design options. It also demonstrates the carbon savings that can be made by the effective reuse of material onsite and the contribution of waste materials to carbon emissions. Additional carbon savings through the reuse or recycling of carbon-rich or valuable materials are also calculated. The use of CReDiT has led to a rethink of remediation excavation and cover design. Excavated /waste materials are re-evaluated as a resource; material reuse options are assessed and carbon reduction is included in the design process. This leads to more sustainable remediation solutions.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2023-03-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41611892","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}
Kaixuan An, Yun-min Chen, K. Gao, Mei-Lan Zhang, J. Lan, H. Ke, L. Zhan
Low-strength sludge takes up a lot of space in landfills, creating an environmental concern and a resource waste that needs to be treated right away. A novel mixed solidifying agent in this work is introduced to the geotechnical characteristics’ improvement of sludge for the first time. The role of each component in the mixed agent is explored by a series of different additive dosages in solidification. According to water content tests, shear wave velocity tests, unconfined compression strength tests, direct shear strength tests, X-ray diffraction, and scanning electron microscopy, the strength development of solidified sludge is comprehensively analyzed under different dosages and curing ages. The micro-analysis result shows that the geotechnical characteristics improved mostly due to hydration products such as ettringite, calcium silicate hydrate gel, aluminum gel, and hydrogarnet. Besides, the generation of hydration products consumes the water in sludge, fills soil particle pores, and connects the soil particles, which makes the structure of solidified sludge compacted, hence, improving the strength of the solidified sludge. Furthermore, the relationship between the shear wave velocity and undrained shear strength parameters follows the power function and indicates that the shear wave velocity can characterize the strength level of the solidified sludge.
{"title":"Geotechnical property development and micro characteristic evolution of solidified sludge using a novel mixed agent","authors":"Kaixuan An, Yun-min Chen, K. Gao, Mei-Lan Zhang, J. Lan, H. Ke, L. Zhan","doi":"10.1680/jenge.21.00127","DOIUrl":"https://doi.org/10.1680/jenge.21.00127","url":null,"abstract":"Low-strength sludge takes up a lot of space in landfills, creating an environmental concern and a resource waste that needs to be treated right away. A novel mixed solidifying agent in this work is introduced to the geotechnical characteristics’ improvement of sludge for the first time. The role of each component in the mixed agent is explored by a series of different additive dosages in solidification. According to water content tests, shear wave velocity tests, unconfined compression strength tests, direct shear strength tests, X-ray diffraction, and scanning electron microscopy, the strength development of solidified sludge is comprehensively analyzed under different dosages and curing ages. The micro-analysis result shows that the geotechnical characteristics improved mostly due to hydration products such as ettringite, calcium silicate hydrate gel, aluminum gel, and hydrogarnet. Besides, the generation of hydration products consumes the water in sludge, fills soil particle pores, and connects the soil particles, which makes the structure of solidified sludge compacted, hence, improving the strength of the solidified sludge. Furthermore, the relationship between the shear wave velocity and undrained shear strength parameters follows the power function and indicates that the shear wave velocity can characterize the strength level of the solidified sludge.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2023-03-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47532375","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}
Pub Date : 2023-03-27DOI: 10.3390/geotechnics3020009
I. Umaru, M. M. Alhaji, M. Alhassan, Taiye Elisha Adejumo, B. Alkali, A. H. Birniwa, A. H. Jagaba
This study proposes a method of gradually loading plate load on-site using lever arms to squeeze out pore water from clayey soils, allowing the soil to settle. Several types of tests were conducted, including a conventional field plate load test (CFPLT), a numerical field plate load test (NFPLT) and an innovative field plate load test (IFPLT) proposed in this study. Three trial pits with soils of varied engineering properties were studied using CFPLT, which employed the use of a heavy jack for load application, the NFPLT test using PLAXIS and an IFPLT, which employed a lever arm to magnify the applied static load. Disturbed soil samples collected from these trial pits were tested for index properties while the undisturbed soil samples were tested using the undrained triaxial compression test (UTCT) and laboratory consolidation tests. The results of the index properties classified these three clay soils as silt of low plasticity (ML) for clay from site 1, and clay of low plasticity (CL) for clay from site 2 and 3. The cohesion and angle of internal friction from the UTCT recorded cohesion values were 28, 29 and 37 kN/m2 for sites 1, 2 and 3, respectively, while the angle of internal friction values were 13, 8 and 6° for sites 1, 2 and 3, respectively. The plate load testing using the three methods showed similar graph pattern except that the allowable load occurred at approximately 350 kN/m2 for the CFPLT and 150 kN/m2 for the IFPLT. The high value of bearing capacity in CFPLT is due to the short period of time taken to load from a jack, which allowed the test to be completed within a short period of time. The ultimate bearing capacities computed from the laboratory test have values of 315.0, 231.0 and 270.0 kN/m2 for sites 1, 2 and 3, respectively. These values agree closely with the bearing capacities obtained for CFPLT but higher than the values recorded for the IFPLT. This is probably due to the long period of sustained loading during testing, which allowed for dissipation of pore water during each loading. Settlements obtained using the IFPLT were close to 25 mm, which is recommended as minimum settlements for building structures BS 8004, 1986.
{"title":"Development of Innovative Plate Load Testing Equipment for In-Situ Saturated Clays Soils","authors":"I. Umaru, M. M. Alhaji, M. Alhassan, Taiye Elisha Adejumo, B. Alkali, A. H. Birniwa, A. H. Jagaba","doi":"10.3390/geotechnics3020009","DOIUrl":"https://doi.org/10.3390/geotechnics3020009","url":null,"abstract":"This study proposes a method of gradually loading plate load on-site using lever arms to squeeze out pore water from clayey soils, allowing the soil to settle. Several types of tests were conducted, including a conventional field plate load test (CFPLT), a numerical field plate load test (NFPLT) and an innovative field plate load test (IFPLT) proposed in this study. Three trial pits with soils of varied engineering properties were studied using CFPLT, which employed the use of a heavy jack for load application, the NFPLT test using PLAXIS and an IFPLT, which employed a lever arm to magnify the applied static load. Disturbed soil samples collected from these trial pits were tested for index properties while the undisturbed soil samples were tested using the undrained triaxial compression test (UTCT) and laboratory consolidation tests. The results of the index properties classified these three clay soils as silt of low plasticity (ML) for clay from site 1, and clay of low plasticity (CL) for clay from site 2 and 3. The cohesion and angle of internal friction from the UTCT recorded cohesion values were 28, 29 and 37 kN/m2 for sites 1, 2 and 3, respectively, while the angle of internal friction values were 13, 8 and 6° for sites 1, 2 and 3, respectively. The plate load testing using the three methods showed similar graph pattern except that the allowable load occurred at approximately 350 kN/m2 for the CFPLT and 150 kN/m2 for the IFPLT. The high value of bearing capacity in CFPLT is due to the short period of time taken to load from a jack, which allowed the test to be completed within a short period of time. The ultimate bearing capacities computed from the laboratory test have values of 315.0, 231.0 and 270.0 kN/m2 for sites 1, 2 and 3, respectively. These values agree closely with the bearing capacities obtained for CFPLT but higher than the values recorded for the IFPLT. This is probably due to the long period of sustained loading during testing, which allowed for dissipation of pore water during each loading. Settlements obtained using the IFPLT were close to 25 mm, which is recommended as minimum settlements for building structures BS 8004, 1986.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":"3 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2023-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83383434","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}
Pub Date : 2023-03-25DOI: 10.3390/geotechnics3020008
P. Kulatilake, Mawuko Luke Yaw Ankah
This paper provides a review of the present status of the topic dealt with. The contact and non-contact methods used for rock joint roughness measurement are summarized including their salient features, advantages, and disadvantages. A critical review is given of the empirical, statistical, and fractal-based methods used for rock joint roughness quantification identifying their salient features, shortcomings, and strong attributes. The surface topography of rough rock joints is highly erratic. Fractional geometry is better suited than Euclidean geometry in representing highly erratic rock joint surfaces. The influence of non-stationarity on accurate quantification of roughness is discussed. The existence of heterogeneity of natural rock joint roughness and its effect on computed roughness parameters are well illustrated. The controversial findings that have been appearing in the literature on roughness scale effects during the last 40 years have resulted from neglecting the effect of roughness heterogeneity on scale effects. The roughness heterogeneity controls the rock joint roughness scale effect, and it can be either negative, positive, or no scale effect depending on the type and level of the roughness heterogeneity of the rock joint surface. The importance of consideration of the existence of possible anisotropy in the quantification of roughness is well illustrated. The indices available to quantify the level of anisotropy are given. Effects of sampling interval and measurement resolution on the accurate quantification of roughness are discussed. A comparison of results obtained by using different quantification methods is discussed. A few recommendations are given for future research to address the shortcomings that exist on the topic dealt with in the paper.
{"title":"Rock Joint Roughness Measurement and Quantification—A Review of the Current Status","authors":"P. Kulatilake, Mawuko Luke Yaw Ankah","doi":"10.3390/geotechnics3020008","DOIUrl":"https://doi.org/10.3390/geotechnics3020008","url":null,"abstract":"This paper provides a review of the present status of the topic dealt with. The contact and non-contact methods used for rock joint roughness measurement are summarized including their salient features, advantages, and disadvantages. A critical review is given of the empirical, statistical, and fractal-based methods used for rock joint roughness quantification identifying their salient features, shortcomings, and strong attributes. The surface topography of rough rock joints is highly erratic. Fractional geometry is better suited than Euclidean geometry in representing highly erratic rock joint surfaces. The influence of non-stationarity on accurate quantification of roughness is discussed. The existence of heterogeneity of natural rock joint roughness and its effect on computed roughness parameters are well illustrated. The controversial findings that have been appearing in the literature on roughness scale effects during the last 40 years have resulted from neglecting the effect of roughness heterogeneity on scale effects. The roughness heterogeneity controls the rock joint roughness scale effect, and it can be either negative, positive, or no scale effect depending on the type and level of the roughness heterogeneity of the rock joint surface. The importance of consideration of the existence of possible anisotropy in the quantification of roughness is well illustrated. The indices available to quantify the level of anisotropy are given. Effects of sampling interval and measurement resolution on the accurate quantification of roughness are discussed. A comparison of results obtained by using different quantification methods is discussed. A few recommendations are given for future research to address the shortcomings that exist on the topic dealt with in the paper.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":"276 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2023-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90782580","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}
Pub Date : 2023-03-17DOI: 10.3390/geotechnics3010007
Qianhao Tang, I. Gratchev, S. Ravindran
This paper seeks to investigate the effect of rainfall intensity on the occurrence of shallow landslides by means of a series of flume tests. Coarse-grained material was used to build a slope, and several rainfall events with an intensity of either 40 mm/h, 70 mm/h, or 100 mm/h were simulated to initiate slope failure. A set of pore water pressure and moisture content sensors was installed in the slope to monitor changes in the water conditions during each test. Different initial moisture contents of 5% and 10% of the soil mass were used to better understand the effect of moisture on slope stability during rainfall. It was found that the slope failed when intensities of 70 mm/h and 100 mm/h were used; however, no failure was observed with a rainfall intensity of 40 mm/h. The failure patterns were found to be similar, with progressive slides occurring as more water infiltrated the slope. A numerical procedure to estimate the factor of safety over the period of the rainfall event was proposed and validated against the laboratory data. The results of the numerical analysis yielded the failure time, which was close to the time observed in the flume tests.
{"title":"Effect of Rainfall Intensity on Landslide Initiation: Flume Tests and Numerical Analysis","authors":"Qianhao Tang, I. Gratchev, S. Ravindran","doi":"10.3390/geotechnics3010007","DOIUrl":"https://doi.org/10.3390/geotechnics3010007","url":null,"abstract":"This paper seeks to investigate the effect of rainfall intensity on the occurrence of shallow landslides by means of a series of flume tests. Coarse-grained material was used to build a slope, and several rainfall events with an intensity of either 40 mm/h, 70 mm/h, or 100 mm/h were simulated to initiate slope failure. A set of pore water pressure and moisture content sensors was installed in the slope to monitor changes in the water conditions during each test. Different initial moisture contents of 5% and 10% of the soil mass were used to better understand the effect of moisture on slope stability during rainfall. It was found that the slope failed when intensities of 70 mm/h and 100 mm/h were used; however, no failure was observed with a rainfall intensity of 40 mm/h. The failure patterns were found to be similar, with progressive slides occurring as more water infiltrated the slope. A numerical procedure to estimate the factor of safety over the period of the rainfall event was proposed and validated against the laboratory data. The results of the numerical analysis yielded the failure time, which was close to the time observed in the flume tests.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":"2 1","pages":""},"PeriodicalIF":2.2,"publicationDate":"2023-03-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89094990","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The main objective of this investigation is to understand the desiccation behaviour of fluid fine tailings (FFT) pre-dewatered with a superabsorbent polymer (SAP) with respect to wetting-drying cycles. Raw FFT (control) and pre-dewatered FFT with SAP were subjected to five cycles of wetting and six cycles of drying. Evaporation was found to be the dominant mechanism in the dewatering of raw FFT as well as FFT pre-dewatered with SAP. In both cases, the suction developed in each drying cycle was eliminated temporarily by the succeeding wetting cycle. The minimum solids content within the column was found to be around 70%, which corresponded to a vane shear strength of 4.5 kPa. Based on the digital images of the surface, the crack intensity factors of the raw FFT and pre-dewatered FFT were calculated to be 26% and 14%, respectively. Scanning electron microscopy and mercury intrusion porosimetry analyses indicate that the FFT pre-dewatered with SAP after 25 days of evaporation in the second lift exhibits the most compacted texture. The solids content of the FFT pre-dewatered with SAP increased to 98% from an initial 50%. SAP pre-dewatering method can significantly increase the shear strength of FFT subjected to wetting-drying cycles.
{"title":"Effect of wetting-drying cycles on the desiccation of tailings pre-dewatered with SAP","authors":"A. Roshani, M. Fall, K. Kennedy","doi":"10.1680/jenge.21.00038","DOIUrl":"https://doi.org/10.1680/jenge.21.00038","url":null,"abstract":"The main objective of this investigation is to understand the desiccation behaviour of fluid fine tailings (FFT) pre-dewatered with a superabsorbent polymer (SAP) with respect to wetting-drying cycles. Raw FFT (control) and pre-dewatered FFT with SAP were subjected to five cycles of wetting and six cycles of drying. Evaporation was found to be the dominant mechanism in the dewatering of raw FFT as well as FFT pre-dewatered with SAP. In both cases, the suction developed in each drying cycle was eliminated temporarily by the succeeding wetting cycle. The minimum solids content within the column was found to be around 70%, which corresponded to a vane shear strength of 4.5 kPa. Based on the digital images of the surface, the crack intensity factors of the raw FFT and pre-dewatered FFT were calculated to be 26% and 14%, respectively. Scanning electron microscopy and mercury intrusion porosimetry analyses indicate that the FFT pre-dewatered with SAP after 25 days of evaporation in the second lift exhibits the most compacted texture. The solids content of the FFT pre-dewatered with SAP increased to 98% from an initial 50%. SAP pre-dewatering method can significantly increase the shear strength of FFT subjected to wetting-drying cycles.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2023-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41642892","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. Shu, Xiao P. Xue, Qiang Wang, Yunquan Li, Pratap Hadkhale
Marine dredging silt that has been solidified is commonly used as a filler material for inland reclamation and artificial island construction. However, determining the long-term environmental safety of artificial islands made of solidified silt is a challenge. A bridge-tunnel conversion artificial island made of solidified silt was the research location of this study. Laboratory tests were conducted to study the effect of cement content on pollutant pore-water concentration and hydraulic conductivity of solidified silt. The results showed that after solidification treatment, the concentration of heavy-metal concentration in the pore water of dredged silt reduced by 60%–85%, whereas the concentration of OH− increased 106–1070 times, and the hydraulic conductivity decreased by approximately three orders of magnitude. On the basis of the test results, the finite element method was used for simulating the long-term transport of heavy metal Ni2+ and OH− artificial islands. When the cement content increased from 60 to 100 kg/m3, the Ni2+ concentration in the dam around the solidified silt decreased by approximately 68%, whereas the OH− concentration increased approximately 10-fold. However, none of them exceeded the seawater water quality standard. This indicates that the long-term environmental safety of the artificial island could be ensured.
{"title":"Long-term environmental impact of an artificial island of solidified dredged marine silt","authors":"S. Shu, Xiao P. Xue, Qiang Wang, Yunquan Li, Pratap Hadkhale","doi":"10.1680/jenge.22.00066","DOIUrl":"https://doi.org/10.1680/jenge.22.00066","url":null,"abstract":"Marine dredging silt that has been solidified is commonly used as a filler material for inland reclamation and artificial island construction. However, determining the long-term environmental safety of artificial islands made of solidified silt is a challenge. A bridge-tunnel conversion artificial island made of solidified silt was the research location of this study. Laboratory tests were conducted to study the effect of cement content on pollutant pore-water concentration and hydraulic conductivity of solidified silt. The results showed that after solidification treatment, the concentration of heavy-metal concentration in the pore water of dredged silt reduced by 60%–85%, whereas the concentration of OH− increased 106–1070 times, and the hydraulic conductivity decreased by approximately three orders of magnitude. On the basis of the test results, the finite element method was used for simulating the long-term transport of heavy metal Ni2+ and OH− artificial islands. When the cement content increased from 60 to 100 kg/m3, the Ni2+ concentration in the dam around the solidified silt decreased by approximately 68%, whereas the OH− concentration increased approximately 10-fold. However, none of them exceeded the seawater water quality standard. This indicates that the long-term environmental safety of the artificial island could be ensured.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2023-03-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46785196","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}
Hai-jie He, Kuan Chai, Tao Wu, Zhan-hong Qiu, S. Feng, Shifang Wang, H. Xie, Jun Yao, Jianbin Zhao
Phenolic compounds are prevalent organic contaminants in aquatic and soil environments. In order to address the issue of phenolic wastewater treatment, bentonite can be utilized as an effective adsorbent through organic modification. The present study focuses on using sodium bentonite, which was modified with cetyltrimethylammonium bromide (CTMAB), to remove phenol from an aqueous solution. The influence of various factors such as adsorption time, initial phenol concentration, and CTMAB-bentonite dosage on phenol adsorption was thoroughly investigated. In addition, the microstructural changes during the adsorption process, adsorption kinetics, and adsorption isotherms of the organically modified bentonite (OMB) were analyzed. The results indicated that the adsorption equilibrium time of OMB was longer compared to sodium bentonite. The amount of phenol adsorbed by OMB was found to be positively correlated with the initial phenol concentration and CTMAB-bentonite dosage. The maximum phenol adsorption capacity and removal rate achieved were 3.00 mg/g and 43.74%, respectively. The study also revealed that a quasi-second-order kinetic model was appropriate for describing the phenol adsorption process of OMB, and the adsorption isotherm was found to conform to the Freundlich isotherm model. These findings demonstrate the potential of OMB as an efficient and effective adsorbent for phenolic wastewater treatment.
{"title":"Phenol adsorption properties and microstructural changes of organically modified bentonite","authors":"Hai-jie He, Kuan Chai, Tao Wu, Zhan-hong Qiu, S. Feng, Shifang Wang, H. Xie, Jun Yao, Jianbin Zhao","doi":"10.1680/jenge.21.00123","DOIUrl":"https://doi.org/10.1680/jenge.21.00123","url":null,"abstract":"Phenolic compounds are prevalent organic contaminants in aquatic and soil environments. In order to address the issue of phenolic wastewater treatment, bentonite can be utilized as an effective adsorbent through organic modification. The present study focuses on using sodium bentonite, which was modified with cetyltrimethylammonium bromide (CTMAB), to remove phenol from an aqueous solution. The influence of various factors such as adsorption time, initial phenol concentration, and CTMAB-bentonite dosage on phenol adsorption was thoroughly investigated. In addition, the microstructural changes during the adsorption process, adsorption kinetics, and adsorption isotherms of the organically modified bentonite (OMB) were analyzed. The results indicated that the adsorption equilibrium time of OMB was longer compared to sodium bentonite. The amount of phenol adsorbed by OMB was found to be positively correlated with the initial phenol concentration and CTMAB-bentonite dosage. The maximum phenol adsorption capacity and removal rate achieved were 3.00 mg/g and 43.74%, respectively. The study also revealed that a quasi-second-order kinetic model was appropriate for describing the phenol adsorption process of OMB, and the adsorption isotherm was found to conform to the Freundlich isotherm model. These findings demonstrate the potential of OMB as an efficient and effective adsorbent for phenolic wastewater treatment.","PeriodicalId":11823,"journal":{"name":"Environmental geotechnics","volume":" ","pages":""},"PeriodicalIF":2.2,"publicationDate":"2023-03-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42417478","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}
Pub Date : 2023-03-03DOI: 10.3390/geotechnics3010006
Yizhen Chen, Suihong Chen, Didi Li, Xi Jiang
Industrial development has significantly increased the concentration of CO2 in the atmosphere, resulting in the greenhouse effect that harms the global climate and human health. CO2 sequestration in saline aquifers is considered to be one of the efficient ways to eliminate atmospheric CO2 levels. As an important mechanism, the solubility trapping greatly determines the efficiency of CO2 sequestration in saline aquifers, and this depends, in turn, on the density-driven convection that occurs during the sequestration. Density-driven convection is influenced by multiple factors. However, existing discussions on some of these influential factors are still ambiguous or even reach contradictory conclusions. This review summarizes the common modeling approaches and the influence of factors on density-driven convection. We suggest that saline aquifers with high values of depth, permeability, pH, and SO2 impurity concentration are the ideal CO2 sequestration sites. A certain degree of porosity, fractures, stratification, slope, hydrodynamic dispersion, background flow, and formation pressure are also considered advantageous. Meanwhile, the geological formation of the Permian White Rim Sandstone or carbonate is important, but it should not contain brine with excessive viscosity and salinity. Finally, we discuss the contents in need of further research.
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