Previous studies have demonstrated that the surge in jacking force during the Guanjingkou project is caused by the contact conditions of the debris bentonite slurry outside the pipe.Therefore,this paper further system...Previous studies have demonstrated that the surge in jacking force during the Guanjingkou project is caused by the contact conditions of the debris bentonite slurry outside the pipe.Therefore,this paper further systematically investigates the influence of different debris slurry mass ratios(SLRs)and different particle size distributions(PSDs)on the pipe-rock friction characteristics using friction tests.The test results reveal that under the same PSD,an adequate amount of slurry(with an SLR of 1:4)consistently yields the lowest friction coefficient.When the SLR is between 1:2 and 1:3,the viscosity of the slurry reaches its peak,resulting in the highest friction coefficient.Additionally,when the PSD is 1:1:5 and 1:1:15,the friction coefficient is primarily governed by the plowing effect at the contact surface.When the PSD is 5:1:1 and 15:1:1,the friction coefficient is mainly controlled by the void ratio(VR)of debris.In the case of PSDs 1:5:1 and 1:15:1,the friction coefficient is jointly controlled by the adhesion effect of high-viscosity slurry and the plowing effect at the contact surface,and it gradually shifts towards being dominated by the VR as the amount of debris increases.Regardless of the SLRs and PSDs,the continuous deposition of debris and the injection of slurry incessantly exacerbate both the plowing and adhesion effects,creating a vicious cycle.This is the reason why the high-pressure water flushing method can not only fail to resolve the issue but also accelerate the occurrence of the surge in jacking force.展开更多
Determining earth pressure on jacked pipes is essential for ensuring lining safety and calculating jacking force,especially for deep-buried pipes.To better reflect the soil arching effect resulting from the excavation...Determining earth pressure on jacked pipes is essential for ensuring lining safety and calculating jacking force,especially for deep-buried pipes.To better reflect the soil arching effect resulting from the excavation of rectangular jacked pipes and the distribution of the earth pressure on jacked pipes,we present an analytical solution for predicting the vertical earth pressure on deep-buried rectangular pipe jacking tunnels,incorporating the tunnelling-induced ground loss distribution.Our proposed analytical model consists of the upper multi-layer parabolic soil arch and the lower friction arch.The key parameters(i.e.,width and height of friction arch B and height of parabolic soil arch H 1)are determined according to the existing research,and an analytical solution for K l is derived based on the distribution characteristics of the principal stress rotation angle.With consideration for the transition effect of the mechanical characteristics of the parabolic arch zone,an analytical solution for soil load transfer is derived.The prediction results of our analytical solution are compared with tests and simulation results to validate the effectiveness of the proposed analytical solution.Finally,the effects of different parameters on the soil pressure are discussed.展开更多
As an economically crucial species in the southeast Pacific Ocean,understanding the spatiotemporal distribution changes of the habitat of Trachurus murphyi under the influence of climate change is essential for effect...As an economically crucial species in the southeast Pacific Ocean,understanding the spatiotemporal distribution changes of the habitat of Trachurus murphyi under the influence of climate change is essential for effective resource assessment and management.The spatiotemporal changes in suitable habitats of T.murphyi under three climate change scenarios(SSP 126,SSP 370,and SSP 585)of Phase 6 of the Coupled Model Intercomparison Project(CMIP 6)were explored based on key environmental factors affecting the potential distribution of the species in a habitat suitability index(HSI)model.Results show that seawater temperature would increase under different scenarios,while the mixed layer depths would decrease under SSP 370 and SSP 585 scenarios but vary slightly under the SSP 126 scenario,which is similar to the variation in different climate periods.The positive difference in seawater temperature will be distributed in the central,southern,and offshore regions of Chile,and the negative difference in mixed layer depths be accounted for a large region.Under different climate scenarios,the HSI value for fishing ground and the overall proportion of suitable habitat area of T.murphyi will be decreased over the forecasted period.The suitable habitat of T.murphyi is concentrated in the 42°S-47°S area and will move to the southwest in different climate periods.Based on short-term climate change,the proportion of suitable habitat areas in the high seas of Chile is larger than in the exclusive economic zone under medium-and long-term climate change under different scenarios.The results of the gravity center of suitable T.murphyi habitat indicates that the spatial distribution of T.murphyi might be related to variations in oceanic currents.These findings provide insights for the effective fisheries resource management of T.murphyi in the Southeast Pacific Ocean.展开更多
For a pipejacking, the jacking force is critical to balance the resistance force and to move the pipe string forwards. The driving mechanism of a curved pipejacking is more complicated than a straight-line pipejacking...For a pipejacking, the jacking force is critical to balance the resistance force and to move the pipe string forwards. The driving mechanism of a curved pipejacking is more complicated than a straight-line pipejacking, and its jacking force is also more difficult to be determined. The paper theoretically studies the jacking force of a curved pipejacking by considering the static equilibrium of earth pressure, resistance at cutting face, friction at pipe surface, and the driving force behind the pipe string. The derived theoretical formula can be used to estimate the driving forces of a straight-line or a curved pipejacking. Case study was performed by applying the theoretical and empirical formulae. After calibration, the corrected formula is more accurate and more applicable.展开更多
在驾驶舱的设计中应用人机工效学原理,利用JACK软件对舱内布局设计进行仿真及舒适性、可达域、可视域等工效进行评价,并提出修改意见。首先将基于人机工效学设计的驾驶舱的CATIA模型导入JACK软件中创建分析对象;然后基于JACK软件建立用...在驾驶舱的设计中应用人机工效学原理,利用JACK软件对舱内布局设计进行仿真及舒适性、可达域、可视域等工效进行评价,并提出修改意见。首先将基于人机工效学设计的驾驶舱的CATIA模型导入JACK软件中创建分析对象;然后基于JACK软件建立用于仿真工效分析的数字人模型(Digital Human Model),将数字人模型调整成驾驶员工作时的最优姿势,仿真驾驶员位于驾驶舱的虚拟环境。最后应用JACK软件的人机工效分析工具对驾驶舱内部进行分析并提出改进意见,这样既缩短了设计周期,又减少了设计制造费用。展开更多
基金the funding support from the National Natural Science Foundations for Young Scientists of China(Grant No.52208391)Doctoral Foundation Project of Guizhou University(Grant No.2021e78).
文摘Previous studies have demonstrated that the surge in jacking force during the Guanjingkou project is caused by the contact conditions of the debris bentonite slurry outside the pipe.Therefore,this paper further systematically investigates the influence of different debris slurry mass ratios(SLRs)and different particle size distributions(PSDs)on the pipe-rock friction characteristics using friction tests.The test results reveal that under the same PSD,an adequate amount of slurry(with an SLR of 1:4)consistently yields the lowest friction coefficient.When the SLR is between 1:2 and 1:3,the viscosity of the slurry reaches its peak,resulting in the highest friction coefficient.Additionally,when the PSD is 1:1:5 and 1:1:15,the friction coefficient is primarily governed by the plowing effect at the contact surface.When the PSD is 5:1:1 and 15:1:1,the friction coefficient is mainly controlled by the void ratio(VR)of debris.In the case of PSDs 1:5:1 and 1:15:1,the friction coefficient is jointly controlled by the adhesion effect of high-viscosity slurry and the plowing effect at the contact surface,and it gradually shifts towards being dominated by the VR as the amount of debris increases.Regardless of the SLRs and PSDs,the continuous deposition of debris and the injection of slurry incessantly exacerbate both the plowing and adhesion effects,creating a vicious cycle.This is the reason why the high-pressure water flushing method can not only fail to resolve the issue but also accelerate the occurrence of the surge in jacking force.
基金Project(2022YJS073)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(2024YFE0198500)supported by the National Key Research and Development Program of China:Intergovernmental International Science and Technology Innovation CooperationProject(U2469207)supported by the National Natural Science Foundation Railway Innovation and Development Joint Fund Project,China。
文摘Determining earth pressure on jacked pipes is essential for ensuring lining safety and calculating jacking force,especially for deep-buried pipes.To better reflect the soil arching effect resulting from the excavation of rectangular jacked pipes and the distribution of the earth pressure on jacked pipes,we present an analytical solution for predicting the vertical earth pressure on deep-buried rectangular pipe jacking tunnels,incorporating the tunnelling-induced ground loss distribution.Our proposed analytical model consists of the upper multi-layer parabolic soil arch and the lower friction arch.The key parameters(i.e.,width and height of friction arch B and height of parabolic soil arch H 1)are determined according to the existing research,and an analytical solution for K l is derived based on the distribution characteristics of the principal stress rotation angle.With consideration for the transition effect of the mechanical characteristics of the parabolic arch zone,an analytical solution for soil load transfer is derived.The prediction results of our analytical solution are compared with tests and simulation results to validate the effectiveness of the proposed analytical solution.Finally,the effects of different parameters on the soil pressure are discussed.
基金Supported by the National Key R&D Program of China(No.2023 YFD 2401303)the Natural Science Foundation of Shanghai(No.23 ZR 1427100)the Shanghai Talent Development Funding(No.2021078)。
文摘As an economically crucial species in the southeast Pacific Ocean,understanding the spatiotemporal distribution changes of the habitat of Trachurus murphyi under the influence of climate change is essential for effective resource assessment and management.The spatiotemporal changes in suitable habitats of T.murphyi under three climate change scenarios(SSP 126,SSP 370,and SSP 585)of Phase 6 of the Coupled Model Intercomparison Project(CMIP 6)were explored based on key environmental factors affecting the potential distribution of the species in a habitat suitability index(HSI)model.Results show that seawater temperature would increase under different scenarios,while the mixed layer depths would decrease under SSP 370 and SSP 585 scenarios but vary slightly under the SSP 126 scenario,which is similar to the variation in different climate periods.The positive difference in seawater temperature will be distributed in the central,southern,and offshore regions of Chile,and the negative difference in mixed layer depths be accounted for a large region.Under different climate scenarios,the HSI value for fishing ground and the overall proportion of suitable habitat area of T.murphyi will be decreased over the forecasted period.The suitable habitat of T.murphyi is concentrated in the 42°S-47°S area and will move to the southwest in different climate periods.Based on short-term climate change,the proportion of suitable habitat areas in the high seas of Chile is larger than in the exclusive economic zone under medium-and long-term climate change under different scenarios.The results of the gravity center of suitable T.murphyi habitat indicates that the spatial distribution of T.murphyi might be related to variations in oceanic currents.These findings provide insights for the effective fisheries resource management of T.murphyi in the Southeast Pacific Ocean.
文摘For a pipejacking, the jacking force is critical to balance the resistance force and to move the pipe string forwards. The driving mechanism of a curved pipejacking is more complicated than a straight-line pipejacking, and its jacking force is also more difficult to be determined. The paper theoretically studies the jacking force of a curved pipejacking by considering the static equilibrium of earth pressure, resistance at cutting face, friction at pipe surface, and the driving force behind the pipe string. The derived theoretical formula can be used to estimate the driving forces of a straight-line or a curved pipejacking. Case study was performed by applying the theoretical and empirical formulae. After calibration, the corrected formula is more accurate and more applicable.
文摘在驾驶舱的设计中应用人机工效学原理,利用JACK软件对舱内布局设计进行仿真及舒适性、可达域、可视域等工效进行评价,并提出修改意见。首先将基于人机工效学设计的驾驶舱的CATIA模型导入JACK软件中创建分析对象;然后基于JACK软件建立用于仿真工效分析的数字人模型(Digital Human Model),将数字人模型调整成驾驶员工作时的最优姿势,仿真驾驶员位于驾驶舱的虚拟环境。最后应用JACK软件的人机工效分析工具对驾驶舱内部进行分析并提出改进意见,这样既缩短了设计周期,又减少了设计制造费用。
