Yi Shen, Jing-yu Hu, L. Lu, Chao Zhu, Qile Fang, Shuang Song
Photocatalysis using the abundant solar energy is an environmentally friendly and efficient way to degrade organic matter. Covalent triazine frameworks (CTFs), a new class of metal-free organic semiconductors responsive to visible light, are promising materials for water treatment. In this study, an original CTF, namely CTF-1, was modified by S-doping to form CTFSx, which were used as metal-free catalysts for degradation of methyl orange (MO) and bisphenol A (BPA). The outcomes demonstrated that the photocatalytic degradation of MO and BPA by CTFSx was superior to that by CTF-1, with better stability and reusability. Within 6 h, 53.2% MO and 84.7% BPA were degraded by CTFS5, and the degradation rate constants were 0.145 h−1 and 0.29 h−1, respectively, which were 3.6 and 5.8 times higher than those of CTF-1. Further investigation revealed that enhanced visible light absorption, a reduced degree of free carrier recombination, rapid separation and transfer of photogenerated electrons and holes, and improved ·OH oxidation capacity were important factors contributing to the significantly enhanced photocatalytic activity. The S-doping method effectively improved the light absorption performance, electronic structure, and modulation band structure of CTF-1. This work highlights the potential application of low-cost metal-free catalysts driven by visible light for the removal of organic pollutants from wastewater.
{"title":"Enhanced photocatalytic performance of S-doped covalent triazine framework for organic pollutant degradation","authors":"Yi Shen, Jing-yu Hu, L. Lu, Chao Zhu, Qile Fang, Shuang Song","doi":"10.1631/2023.A2200440","DOIUrl":"https://doi.org/10.1631/2023.A2200440","url":null,"abstract":"Photocatalysis using the abundant solar energy is an environmentally friendly and efficient way to degrade organic matter. Covalent triazine frameworks (CTFs), a new class of metal-free organic semiconductors responsive to visible light, are promising materials for water treatment. In this study, an original CTF, namely CTF-1, was modified by S-doping to form CTFSx, which were used as metal-free catalysts for degradation of methyl orange (MO) and bisphenol A (BPA). The outcomes demonstrated that the photocatalytic degradation of MO and BPA by CTFSx was superior to that by CTF-1, with better stability and reusability. Within 6 h, 53.2% MO and 84.7% BPA were degraded by CTFS5, and the degradation rate constants were 0.145 h−1 and 0.29 h−1, respectively, which were 3.6 and 5.8 times higher than those of CTF-1. Further investigation revealed that enhanced visible light absorption, a reduced degree of free carrier recombination, rapid separation and transfer of photogenerated electrons and holes, and improved ·OH oxidation capacity were important factors contributing to the significantly enhanced photocatalytic activity. The S-doping method effectively improved the light absorption performance, electronic structure, and modulation band structure of CTF-1. This work highlights the potential application of low-cost metal-free catalysts driven by visible light for the removal of organic pollutants from wastewater.","PeriodicalId":17508,"journal":{"name":"Journal of Zhejiang University-SCIENCE A","volume":"10 1","pages":"988 - 997"},"PeriodicalIF":3.2,"publicationDate":"2022-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88558852","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}
Ming Wei, Q. Luo, Guishuai Feng, Teng-fei Wang, Liang-wei Jiang
Physical modelling of cantilever retaining walls with and without backfill reinforcement was conducted on a 1g shaking table to evaluate the mitigation effect of reinforcement on system dynamics (g denotes the acceleration of gravity). The model wall has a height of 1.5 m with a scale ratio of 1/4 and retains dry sand throughout. The input motions are amplified to three levels of input peak base acceleration, 0.11g, 0.24g, and 0.39g, corresponding to minor, moderate, and major earthquakes, respectively. Investigation of the seismic response of the retaining walls focuses on acceleration and lateral displacement of the wall and backfill, dynamic earth pressures, and tensile load in the reinforcements (modeled by phosphor-bronze strips welded into a mesh). The inclusion of reinforcement has been observed to improve the integrity of the wall-soil system, mitigate vibration-related damage, and reduce the fundamental frequency of a reinforced system. Propagation of acceleration from the base to the upper portion is accompanied by time delay and nonlinear amplification. A reinforced system with a lower acceleration amplification factor than the unreinforced one indicates that reinforcement can reduce the amplification effect of input motion. Under minor and moderate earthquake loadings, reinforcement allows the inertia force and seismic earth pressure to be asynchronous and decreases the seismic earth pressure when inertia forces peak. During major earthquake loading, the wall is displaced horizontally less than the backfill, with soil pushing the wall substantially; the effect of backfill reinforcement has not been fully mobilized. The dynamic earth pressure is large at the top and diminishes toward the bottom.
{"title":"Shaking table tests on a cantilever retaining wall with reinforced and unreinforced backfill","authors":"Ming Wei, Q. Luo, Guishuai Feng, Teng-fei Wang, Liang-wei Jiang","doi":"10.1631/jzus.A2200192","DOIUrl":"https://doi.org/10.1631/jzus.A2200192","url":null,"abstract":"Physical modelling of cantilever retaining walls with and without backfill reinforcement was conducted on a 1g shaking table to evaluate the mitigation effect of reinforcement on system dynamics (g denotes the acceleration of gravity). The model wall has a height of 1.5 m with a scale ratio of 1/4 and retains dry sand throughout. The input motions are amplified to three levels of input peak base acceleration, 0.11g, 0.24g, and 0.39g, corresponding to minor, moderate, and major earthquakes, respectively. Investigation of the seismic response of the retaining walls focuses on acceleration and lateral displacement of the wall and backfill, dynamic earth pressures, and tensile load in the reinforcements (modeled by phosphor-bronze strips welded into a mesh). The inclusion of reinforcement has been observed to improve the integrity of the wall-soil system, mitigate vibration-related damage, and reduce the fundamental frequency of a reinforced system. Propagation of acceleration from the base to the upper portion is accompanied by time delay and nonlinear amplification. A reinforced system with a lower acceleration amplification factor than the unreinforced one indicates that reinforcement can reduce the amplification effect of input motion. Under minor and moderate earthquake loadings, reinforcement allows the inertia force and seismic earth pressure to be asynchronous and decreases the seismic earth pressure when inertia forces peak. During major earthquake loading, the wall is displaced horizontally less than the backfill, with soil pushing the wall substantially; the effect of backfill reinforcement has not been fully mobilized. The dynamic earth pressure is large at the top and diminishes toward the bottom.","PeriodicalId":17508,"journal":{"name":"Journal of Zhejiang University-SCIENCE A","volume":"22 1","pages":"900 - 916"},"PeriodicalIF":3.2,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83452898","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-and-mud inrush disasters have become a major challenge in underground engineering for the construction of tunnels in sandstone and slate interbedded Presinian strata. Disaster prediction and prevention rely in part on realistic modeling and observation of the disaster process, as well as the identification and examination of the underlying mechanisms. Based on the geological conditions and the historical records of the Xinping Tunnel on the China—Laos Railway, an engineering geological model of the water-and-mud inrush was established. A physical model test that accurately reproduced water-and-mud inrush during tunnel excavation in sandstone and slate interbedded strata was also carried out. Then, testing was conducted that examined the stress and strain, seepage pressure, and high-leakage flow of the surrounding rock. The results indicated that the water-and-mud inrush proceeded through three stages: seepage stage, high-leakage flow stage, and attenuation stage. In essence, the disaster was a catastrophic process, during which the water-resistant stratum was reduced to a critical safety thickness, a water-inrush channel formed, and the water-resistant stratum gradually failed under the influence of excavation unloading and in situ stress—seepage coupling. Parameters such as the stress and strain, seepage pressure, and flow of the surrounding rock had evident stage-related features during water-and-mud inrush, and their variation indicated the formation, development, and evolution of the disaster. As the tunnel face advanced, the trend of the stress—strain curve of the surrounding rock shifted from sluggish to rapid in its speed of increase. The characteristics of strain energy density revealed the erosion and weakening effect of groundwater on the surrounding rock. The seepage pressure and the thickness of the water-resistant stratum had a positive linear relationship, and the flow and thickness a negative linear relationship. There was a pivotal point at which the seepage pressure changed from high to low and the flow shifted from low to high. The thickness of the water-resistant stratum corresponding to the pivotal point was deemed the critical safety thickness.
{"title":"Model test of the mechanism underpinning water-and-mud inrush disasters during tunnel excavation in sandstone and slate interbedded Presinian strata","authors":"P. Xu, P. Peng, Rong-hua Wei, Zhi-qiang Zhang","doi":"10.1631/jzus.A2200134","DOIUrl":"https://doi.org/10.1631/jzus.A2200134","url":null,"abstract":"Water-and-mud inrush disasters have become a major challenge in underground engineering for the construction of tunnels in sandstone and slate interbedded Presinian strata. Disaster prediction and prevention rely in part on realistic modeling and observation of the disaster process, as well as the identification and examination of the underlying mechanisms. Based on the geological conditions and the historical records of the Xinping Tunnel on the China—Laos Railway, an engineering geological model of the water-and-mud inrush was established. A physical model test that accurately reproduced water-and-mud inrush during tunnel excavation in sandstone and slate interbedded strata was also carried out. Then, testing was conducted that examined the stress and strain, seepage pressure, and high-leakage flow of the surrounding rock. The results indicated that the water-and-mud inrush proceeded through three stages: seepage stage, high-leakage flow stage, and attenuation stage. In essence, the disaster was a catastrophic process, during which the water-resistant stratum was reduced to a critical safety thickness, a water-inrush channel formed, and the water-resistant stratum gradually failed under the influence of excavation unloading and in situ stress—seepage coupling. Parameters such as the stress and strain, seepage pressure, and flow of the surrounding rock had evident stage-related features during water-and-mud inrush, and their variation indicated the formation, development, and evolution of the disaster. As the tunnel face advanced, the trend of the stress—strain curve of the surrounding rock shifted from sluggish to rapid in its speed of increase. The characteristics of strain energy density revealed the erosion and weakening effect of groundwater on the surrounding rock. The seepage pressure and the thickness of the water-resistant stratum had a positive linear relationship, and the flow and thickness a negative linear relationship. There was a pivotal point at which the seepage pressure changed from high to low and the flow shifted from low to high. The thickness of the water-resistant stratum corresponding to the pivotal point was deemed the critical safety thickness.","PeriodicalId":17508,"journal":{"name":"Journal of Zhejiang University-SCIENCE A","volume":"32 1","pages":"882 - 899"},"PeriodicalIF":3.2,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78097158","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}
Dongmei Zhang, Xiang-hong Bu, Jian Pang, W. Zhou, Yan Jiang, K. Jia, Guanghua Yang
Water conveyance tunnels usually experience high internal water pressures and complex soil conditions. Therefore, shield tunnels with double-lining structure have been adopted because of their high bearing capacity. The effect of the interface between the segmental and inner linings on the bearing capacity has been widely investigated; however, the effect of soil on the internal water pressure bearing capacity has not been emphasized enough. Therefore, in this study, model tests and an analytical solution are presented to elucidate the effect of soil on the internal water pressure bearing capacity. First, model tests are conducted on double-lining models under sandy soil and highly weathered argillaceous siltstone conditions. The internal force and earth pressure under these different soil conditions are then compared to reveal the contribution of soil to the internal water pressure bearing capacity. Following this, an analytical solution, considering the soil—double-lining interaction, is proposed to further investigate the contribution of the soil. The analytical solution is verified with model tests. The analytical solution is in good agreement with the model test results and can be used to evaluate the mechanical behavior of the double-lining and soil contribution. The effect of soil on the bearing capacity is found to be related with the elastic modulus of the soil and the deformation state of the double-lining. Before the double-lining cracks, the sandy soil contributes 3.7% of the internal water pressure but the contribution of the soil rises to 10.4% when it is the highly weathered argillaceous siltstone. After the double-lining cracks, the soil plays an important role in bearing internal water pressure. The soil contributions of sandy soil and highly weathered argillaceous siltstones are 10.5% and 27.8%, respectively. The effect of soil should be considered in tunnel design with the internal water pressure.
{"title":"Soil effect on the bearing capacity of a double-lining structure under internal water pressure","authors":"Dongmei Zhang, Xiang-hong Bu, Jian Pang, W. Zhou, Yan Jiang, K. Jia, Guanghua Yang","doi":"10.1631/jzus.A2200215","DOIUrl":"https://doi.org/10.1631/jzus.A2200215","url":null,"abstract":"Water conveyance tunnels usually experience high internal water pressures and complex soil conditions. Therefore, shield tunnels with double-lining structure have been adopted because of their high bearing capacity. The effect of the interface between the segmental and inner linings on the bearing capacity has been widely investigated; however, the effect of soil on the internal water pressure bearing capacity has not been emphasized enough. Therefore, in this study, model tests and an analytical solution are presented to elucidate the effect of soil on the internal water pressure bearing capacity. First, model tests are conducted on double-lining models under sandy soil and highly weathered argillaceous siltstone conditions. The internal force and earth pressure under these different soil conditions are then compared to reveal the contribution of soil to the internal water pressure bearing capacity. Following this, an analytical solution, considering the soil—double-lining interaction, is proposed to further investigate the contribution of the soil. The analytical solution is verified with model tests. The analytical solution is in good agreement with the model test results and can be used to evaluate the mechanical behavior of the double-lining and soil contribution. The effect of soil on the bearing capacity is found to be related with the elastic modulus of the soil and the deformation state of the double-lining. Before the double-lining cracks, the sandy soil contributes 3.7% of the internal water pressure but the contribution of the soil rises to 10.4% when it is the highly weathered argillaceous siltstone. After the double-lining cracks, the soil plays an important role in bearing internal water pressure. The soil contributions of sandy soil and highly weathered argillaceous siltstones are 10.5% and 27.8%, respectively. The effect of soil should be considered in tunnel design with the internal water pressure.","PeriodicalId":17508,"journal":{"name":"Journal of Zhejiang University-SCIENCE A","volume":"38 1","pages":"863 - 881"},"PeriodicalIF":3.2,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84803510","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}
Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong, China Research Center for Advanced Underground Space Technologies, Hunan University, Changsha 410082, China Key Laboratory of Building Safety and Energy Efficiency of the Ministry of Education, Hunan University, Changsha 410082, China College of Civil Engineering, Hunan University, Changsha 410082, China School of Engineering, University of Warwick, Coventry CV4 7AL, UK
{"title":"Physical model testing in geotechnical engineering","authors":"Z. Yin, Han-Lin Wang, Xueyong Geng","doi":"10.1631/jzus.A22PMTGE","DOIUrl":"https://doi.org/10.1631/jzus.A22PMTGE","url":null,"abstract":"Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Kowloon, Hong Kong, China Research Center for Advanced Underground Space Technologies, Hunan University, Changsha 410082, China Key Laboratory of Building Safety and Energy Efficiency of the Ministry of Education, Hunan University, Changsha 410082, China College of Civil Engineering, Hunan University, Changsha 410082, China School of Engineering, University of Warwick, Coventry CV4 7AL, UK","PeriodicalId":17508,"journal":{"name":"Journal of Zhejiang University-SCIENCE A","volume":"16 1","pages":"845 - 849"},"PeriodicalIF":3.2,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88774075","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}
Shu-jian Wang, Hongxiu Jiang, Zongjin Wang, Yu-jie Wang, Yi-xin Li, Xueyong Geng, Xinyuan Wang, Kai Wang, Yi-yi Liu, Yanxia Gong
Subgrade construction is frequently interrupted due to precipitation, soil shortage, and environmental protection. Therefore, increasing the thickness layer is required to reduce construction costs and to allow highways to be placed into service earlier. This paper presents a series of full-scale field experiments evaluating the compaction quality of gravel subgrade with large-thickness layers of 65 cm and 80 cm using heavy vibratory rollers. An improved sand cone method was first proposed and calibrated to investigate the distribution of soil compaction degree across the full subgrade depth. Results showed that dynamic soil stresses caused by the heavy vibratory rollers were 2.4–5.9 times larger than those of traditional rollers, especially at deeper depths, which were large enough to densify the soils to the full depth. A unified empirical formula was proposed to determine the vertical distribution of dynamic soil stresses caused by roller excitation. It was demonstrated that soils were effectively compacted in a uniform fashion with respect to the full depth to 96.0%–97.2% and 94.1%–95.4% for the large-thickness layers of 65 cm and 80 cm within 6 or 7 passes, respectively. Empirically, linear formulae were finally established between soil compaction degree and the subgrade reaction modulus, dynamic modulus of deformation, dynamic deflection, and relative difference of settlement to conveniently evaluate the compaction qualities. It is demonstrated that increasing the thickness layer by means of heavy rollers can significantly reduce the cost and time burdens involved in construction while ensuring overall subgrade quality. 目的 本文旨在通过65 cm和80 cm松铺厚度路基的全比尺现场试验，提出保障大厚度路基压实效果的施工工艺和评价方法，以提高路基填筑的施工效率、降低能耗和碳排放。 创新点 1. 改进适用于大厚度路基压实度评价的灌砂法；2. 建立碾压轮载作用下的路基内部动态土压力计算修正方程；3. 提出大厚度路基压实施工工艺及验收指标与压实度的关联关系，对大厚度路基压实质量进行可靠快速评价。 方法 1. 采用改进的灌砂筒及其标定方法，对大厚度路基的压实度进行分层检测；2. 基于现场土压力分层监测，获得碾压机械作用下动态土压力沿路基深度的衰减规律；3. 通过对每一遍碾压后的压实度、沉降差、K30、动态回弹模量、动弯沉进行多点检测和分析，获得各物理力学指标随碾压遍数的变化规律及其相互关联关系。 结论 1. 高能级压实下的65 cm和80 cm松铺厚度路基动土压力可达0.19∼1.18 MPa和0.079∼1.19 MPa，可采用修正后的Boussinesq方程表达；2. 路基压实效果与应力水平和土层下部支撑密切相关，底层土体压实度提升前上层土体难以致密化；3. 高能级碾压机械可保证大厚度路基全深度有效压实，且动弯沉作为大厚度路基压实质量评价指标更为可靠。
{"title":"Evaluation of heavy roller compaction on a large-thickness layer of subgrade with full-scale field experiments","authors":"Shu-jian Wang, Hongxiu Jiang, Zongjin Wang, Yu-jie Wang, Yi-xin Li, Xueyong Geng, Xinyuan Wang, Kai Wang, Yi-yi Liu, Yanxia Gong","doi":"10.1631/jzus.A2200201","DOIUrl":"https://doi.org/10.1631/jzus.A2200201","url":null,"abstract":"Subgrade construction is frequently interrupted due to precipitation, soil shortage, and environmental protection. Therefore, increasing the thickness layer is required to reduce construction costs and to allow highways to be placed into service earlier. This paper presents a series of full-scale field experiments evaluating the compaction quality of gravel subgrade with large-thickness layers of 65 cm and 80 cm using heavy vibratory rollers. An improved sand cone method was first proposed and calibrated to investigate the distribution of soil compaction degree across the full subgrade depth. Results showed that dynamic soil stresses caused by the heavy vibratory rollers were 2.4–5.9 times larger than those of traditional rollers, especially at deeper depths, which were large enough to densify the soils to the full depth. A unified empirical formula was proposed to determine the vertical distribution of dynamic soil stresses caused by roller excitation. It was demonstrated that soils were effectively compacted in a uniform fashion with respect to the full depth to 96.0%–97.2% and 94.1%–95.4% for the large-thickness layers of 65 cm and 80 cm within 6 or 7 passes, respectively. Empirically, linear formulae were finally established between soil compaction degree and the subgrade reaction modulus, dynamic modulus of deformation, dynamic deflection, and relative difference of settlement to conveniently evaluate the compaction qualities. It is demonstrated that increasing the thickness layer by means of heavy rollers can significantly reduce the cost and time burdens involved in construction while ensuring overall subgrade quality. 目的 本文旨在通过65 cm和80 cm松铺厚度路基的全比尺现场试验，提出保障大厚度路基压实效果的施工工艺和评价方法，以提高路基填筑的施工效率、降低能耗和碳排放。 创新点 1. 改进适用于大厚度路基压实度评价的灌砂法；2. 建立碾压轮载作用下的路基内部动态土压力计算修正方程；3. 提出大厚度路基压实施工工艺及验收指标与压实度的关联关系，对大厚度路基压实质量进行可靠快速评价。 方法 1. 采用改进的灌砂筒及其标定方法，对大厚度路基的压实度进行分层检测；2. 基于现场土压力分层监测，获得碾压机械作用下动态土压力沿路基深度的衰减规律；3. 通过对每一遍碾压后的压实度、沉降差、K30、动态回弹模量、动弯沉进行多点检测和分析，获得各物理力学指标随碾压遍数的变化规律及其相互关联关系。 结论 1. 高能级压实下的65 cm和80 cm松铺厚度路基动土压力可达0.19∼1.18 MPa和0.079∼1.19 MPa，可采用修正后的Boussinesq方程表达；2. 路基压实效果与应力水平和土层下部支撑密切相关，底层土体压实度提升前上层土体难以致密化；3. 高能级碾压机械可保证大厚度路基全深度有效压实，且动弯沉作为大厚度路基压实质量评价指标更为可靠。","PeriodicalId":17508,"journal":{"name":"Journal of Zhejiang University-SCIENCE A","volume":"34 1","pages":"933-944"},"PeriodicalIF":3.2,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84840034","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}
Geosynthetic-reinforced soil retaining walls (GSRWs) have been widely used in civil engineering projects. However, as the climate changes, extreme weather conditions and natural hazards are likely to become more frequent or intense, posing a huge threat to the stability of GSRWs. In this paper, the effect of groundwater level fluctuations on the seismic response of GSRWs is investigated. First, a dynamic numerical model was established and validated through centrifugal shaking-table test results. Using the established numerical model, the seismic response of GSRWs under four different groundwater level conditions was then investigated, i.e., an earthquake occurring at a low groundwater level (Case LW), an earthquake occurring when the groundwater level rises (Case RW), an earthquake occurring at a high groundwater level (Case HW), and an earthquake occurring when the groundwater level drops (Case DW). The results show that the GSRW in Case DW has the worst seismic stability because of the drag forces generated by the water flowing to the outside of the GSRW. For Case RW, deformation of the GSRW under earthquake forces was prevented by the drag forces generated by the water flowing to the inside of the GSRW and the water pressure acting on the outside of the facing, giving the GSRW the best seismic stability in this case. Compared with Case LW, the seismic stability of a GSRW in Case HW is worse, because the high groundwater level will generate excess pore-water pressure during an earthquake. On this basis, we provide engineering design suggestions to be considered by practitioners.
{"title":"Influence of groundwater level changes on the seismic response of geosynthetic-reinforced soil retaining walls","authors":"Fei-fan Ren, Qian Huang, Xueyong Geng, Guan Wang","doi":"10.1631/jzus.A2200188","DOIUrl":"https://doi.org/10.1631/jzus.A2200188","url":null,"abstract":"Geosynthetic-reinforced soil retaining walls (GSRWs) have been widely used in civil engineering projects. However, as the climate changes, extreme weather conditions and natural hazards are likely to become more frequent or intense, posing a huge threat to the stability of GSRWs. In this paper, the effect of groundwater level fluctuations on the seismic response of GSRWs is investigated. First, a dynamic numerical model was established and validated through centrifugal shaking-table test results. Using the established numerical model, the seismic response of GSRWs under four different groundwater level conditions was then investigated, i.e., an earthquake occurring at a low groundwater level (Case LW), an earthquake occurring when the groundwater level rises (Case RW), an earthquake occurring at a high groundwater level (Case HW), and an earthquake occurring when the groundwater level drops (Case DW). The results show that the GSRW in Case DW has the worst seismic stability because of the drag forces generated by the water flowing to the outside of the GSRW. For Case RW, deformation of the GSRW under earthquake forces was prevented by the drag forces generated by the water flowing to the inside of the GSRW and the water pressure acting on the outside of the facing, giving the GSRW the best seismic stability in this case. Compared with Case LW, the seismic stability of a GSRW in Case HW is worse, because the high groundwater level will generate excess pore-water pressure during an earthquake. On this basis, we provide engineering design suggestions to be considered by practitioners.","PeriodicalId":17508,"journal":{"name":"Journal of Zhejiang University-SCIENCE A","volume":"85 1","pages":"850 - 862"},"PeriodicalIF":3.2,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79823864","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 shear strength properties of the frozen sand—structure interface are critical for evaluating the serviceability of pile foundations in frozen ground. The shear characteristics of the frozen sand—concrete interface were studied with two boundary conditions (constant normal load (CNL) and constant normal height (CNH)), at three normal stresses (100, 200, and 300 kPa), and at three temperatures (−2,−5, and −8 °C). A detailed comparative analysis was performed to explore the principal factors affecting the shear/normal-shear displacement. The results showed that the shear behavior of the frozen sand—concrete interface under CNL was similar to that under CNH. The shear stress—shear displacement exhibited strain softening. The temperature and normal stress were the major influences on normal properties. The lower the temperature and the higher the normal stress, the greater was the elastic shear modulus. The peak shear stress and critical shear stress exhibited a dependence on normal stress. An exponential growth in the peak shear stress was observed as the temperature decreased. Critical shear stress was dependent on temperature. The value and percentage of peak ice-cementation in peak shear stress was affected by temperature and normal stress. 目的 探究不同边界条件下，初始法向应力和温度对冻结砂-混凝土接触面剪切变形和强度特性、法向变形特性以及冰胶结特性的影响。 创新点 1. 在不同边界条件下对冻结砂-混凝土结构进行直剪试验，了解接触面法向和切向特性；2. 建立试验模型，成功模拟弹性剪切模量和强度随温度及初始法向应力的变化关系。 方法 1. 通过实验分析，得到冻结接触面弹性模量和强度特性随温度和初始法向应力的变化（图14∼21和表2∼5）；2. 通过理论推导，构建温度、法向应力与弹性剪切模量和剪切强度之间的关系，得到相应的计算模型（公式(1)∼(6)）。 结论 1. 不同边界条件下，冻结接触面均表现出应变软化特性；2. 弹性剪切模量随初始法向应力的增加和温度的降低呈线性增长趋势；3. 冻结接触面剪切强度随初始法向应力的增加线性增长，而随温度的降低呈指数增长。
{"title":"Frozen sand—concrete interface direct shear behavior under constant normal load and constant normal height boundary","authors":"Jian Chang, Jian-kun Liu, Ya-li Li","doi":"10.1631/jzus.A2200118","DOIUrl":"https://doi.org/10.1631/jzus.A2200118","url":null,"abstract":"The shear strength properties of the frozen sand—structure interface are critical for evaluating the serviceability of pile foundations in frozen ground. The shear characteristics of the frozen sand—concrete interface were studied with two boundary conditions (constant normal load (CNL) and constant normal height (CNH)), at three normal stresses (100, 200, and 300 kPa), and at three temperatures (−2,−5, and −8 °C). A detailed comparative analysis was performed to explore the principal factors affecting the shear/normal-shear displacement. The results showed that the shear behavior of the frozen sand—concrete interface under CNL was similar to that under CNH. The shear stress—shear displacement exhibited strain softening. The temperature and normal stress were the major influences on normal properties. The lower the temperature and the higher the normal stress, the greater was the elastic shear modulus. The peak shear stress and critical shear stress exhibited a dependence on normal stress. An exponential growth in the peak shear stress was observed as the temperature decreased. Critical shear stress was dependent on temperature. The value and percentage of peak ice-cementation in peak shear stress was affected by temperature and normal stress. 目的 探究不同边界条件下，初始法向应力和温度对冻结砂-混凝土接触面剪切变形和强度特性、法向变形特性以及冰胶结特性的影响。 创新点 1. 在不同边界条件下对冻结砂-混凝土结构进行直剪试验，了解接触面法向和切向特性；2. 建立试验模型，成功模拟弹性剪切模量和强度随温度及初始法向应力的变化关系。 方法 1. 通过实验分析，得到冻结接触面弹性模量和强度特性随温度和初始法向应力的变化（图14∼21和表2∼5）；2. 通过理论推导，构建温度、法向应力与弹性剪切模量和剪切强度之间的关系，得到相应的计算模型（公式(1)∼(6)）。 结论 1. 不同边界条件下，冻结接触面均表现出应变软化特性；2. 弹性剪切模量随初始法向应力的增加和温度的降低呈线性增长趋势；3. 冻结接触面剪切强度随初始法向应力的增加线性增长，而随温度的降低呈指数增长。","PeriodicalId":17508,"journal":{"name":"Journal of Zhejiang University-SCIENCE A","volume":"24 1","pages":"917-932"},"PeriodicalIF":3.2,"publicationDate":"2022-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83069146","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}
J. Qian, Lei Zhao, Xiao-juan Li, Wen-qing Li, Zhi-jiang Jin
In this study, droplet characteristics including droplet length and formation time, and mixing efficiency in droplets were investigated via the volume of fluid (VOF) method coupled with a user defined scalar (UDS) model. A cross-shaped junction with a square cross-section was designed and used for droplet formation. An initial arrangement which differed from that of a conventional operation was adopted. Results show that when the droplet superficial velocity is constant, the exchange between the dispersed phase velocity and the continuous phase velocity has a marginal effect on the droplet formation time. However, the exchange has a great effect on droplet length. These findings provide a valuable guide for future operation of droplet formation. In addition, the results show that the mixing efficiency in the droplet forming stage can be classified into time-dominated and length-dominated regimes according to the droplet superficial velocity. When a droplet flows in a microchannel, a higher droplet superficial velocity increases mixing efficiency due to the faster inner circulation and shorter droplet length.
{"title":"Effect of droplet superficial velocity on mixing efficiency in a microchannel","authors":"J. Qian, Lei Zhao, Xiao-juan Li, Wen-qing Li, Zhi-jiang Jin","doi":"10.1631/jzus.A2200159","DOIUrl":"https://doi.org/10.1631/jzus.A2200159","url":null,"abstract":"In this study, droplet characteristics including droplet length and formation time, and mixing efficiency in droplets were investigated via the volume of fluid (VOF) method coupled with a user defined scalar (UDS) model. A cross-shaped junction with a square cross-section was designed and used for droplet formation. An initial arrangement which differed from that of a conventional operation was adopted. Results show that when the droplet superficial velocity is constant, the exchange between the dispersed phase velocity and the continuous phase velocity has a marginal effect on the droplet formation time. However, the exchange has a great effect on droplet length. These findings provide a valuable guide for future operation of droplet formation. In addition, the results show that the mixing efficiency in the droplet forming stage can be classified into time-dominated and length-dominated regimes according to the droplet superficial velocity. When a droplet flows in a microchannel, a higher droplet superficial velocity increases mixing efficiency due to the faster inner circulation and shorter droplet length.","PeriodicalId":17508,"journal":{"name":"Journal of Zhejiang University-SCIENCE A","volume":"27 1","pages":"783 - 794"},"PeriodicalIF":3.2,"publicationDate":"2022-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83714181","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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