The composite pile consisting of core-pile and surrounding cement-enhanced soil is a promising pile foundation in recent years.However,how and to what extent the cement-enhanced soil influences the ultimate lateral re...The composite pile consisting of core-pile and surrounding cement-enhanced soil is a promising pile foundation in recent years.However,how and to what extent the cement-enhanced soil influences the ultimate lateral resistance has not been fully investigated.In this paper,the ultimate lateral resistance of the composite pile was studied by finite element limit analysis(FELA)and theoretical upper-bound analysis.The results of FELA and theoretical analysis revealed three failure modes of laterally loaded composite piles.The effects of the enhanced soil thickness,strength,and pile-enhanced soil interface characteristics on the ultimate lateral resistance were studied.The results show that increasing the enhanced soil thickness leads to a significant improvement on ultimate lateral resistance factor(N P),and there is a critical thickness beyond which the thickness no longer affects the N P.Increasing the enhanced soil strength induced 6.2%-232.6%increase of N P.However,no noticeable impact was detected when the enhanced soil strength was eight times higher than that of the natural soil.The maximum increment of N P is only 30.5%caused by the increase of interface adhesion factor(a).An empirical model was developed to calculate the N P of the composite pile,and the results show excellent agreement with the analytical results.展开更多
How to determine reasonable position and length of anchor cable is a frequently encountered but not well addressed problem in slope reinforcement projects. In this paper, the variable-modulus elastoplastic strength re...How to determine reasonable position and length of anchor cable is a frequently encountered but not well addressed problem in slope reinforcement projects. In this paper, the variable-modulus elastoplastic strength reduction method （SRM） is used to obtain the stress field, displacement field, and factor of safety of slope. Slope reinforcement using anchor cables is modeled by surface loading, i.e. different distributions of surface loading represent various reinforcement schemes. Optimal reinforcement scheme of anchor cables can be determined based on slope stress and displacement fields. By comparing the factor of safety and stress field before and after slope reinforcement, it is found that better rein-forcement results can be achieved if strong reinforcement is applied upon the regions with high stress and large displacement. This method can well optimize the arrangement of anchor cables. In addition, several cases are employed to verify the proposed method.展开更多
Fluctuating snow-covered elevation （FSCE） was conceptualized and proposed to characterize within-year variation of the border between snow-covered and snow-free area in mountainous regions. Two parameters, namely me...Fluctuating snow-covered elevation （FSCE） was conceptualized and proposed to characterize within-year variation of the border between snow-covered and snow-free area in mountainous regions. Two parameters, namely median of snow flee period （Tm） and snow free duration （AT）, were defined to quantify FSCE. A regression model of FSCE was developed for the Lhasa River Basin, Niyang River Basin, and Changdu region in eastern Tibet. Statistical analysis of the snow-products data with a spatial resolution of 25km×25km shows that： （1） Tm correlates weakly with geographical and topographic factors, having the yearly mean value of July 31; （2） △T correlates significantly with the average elevation of the snow-products cell, having the yearly mean value of nearly five months （i.e., 151 days）; （3） the region begins snow disappearance in late April and finishes snow coverage in mid November, being snow-free from late June to mid September and snow-covered from December to March in the next year. In addi- tion, snow-products with higher spatial resolution will be helpful to characterize FSCE in smaller spatial scales.展开更多
Inter-basin water diversion projects have led to accelerated colonization of aquatic organisms,including the freshwater golden mussel(Limnoperna fortunei),exacerbating global biofouling concerns.While the influence of...Inter-basin water diversion projects have led to accelerated colonization of aquatic organisms,including the freshwater golden mussel(Limnoperna fortunei),exacerbating global biofouling concerns.While the influence of environmental factors on the mussel's invasion and biofouling impact has been studied,quantitative correlations and underlying mechanisms remain unclear,particularly in large-scale interbasin water diversion projects with diverse hydrodynamic and environmental conditions.Here,we examine the comprehensive impact of environmental variables on the establishment risk of the golden mussel in China's 1432-km-long Middle Route of the South-to-North Water Diversion Project.Logistic regression and multiclass classification models were used to investigate the environmental influence on the occurrence probability and reproductive density of the golden mussel.Total nitrogen,ammonia nitrogen,water temperature,pH,and velocity were identified as crucial environmental variables affecting the biofouling risk in the project.Logistic regression analysis revealed a negative correlation between the occurrence probability of all larval stages and levels of total nitrogen and ammonia nitrogen.The multiclass classification model showed that elevated levels of total nitrogen hindered mussel reproduction,while optimal water temperature enhanced their reproductive capacity.Appropriate velocity and pH levels were crucial in maintaining moderate larval density.This research presents a quantitative analytical framework for assessing establishment risks associated with invasive mussels,and the framework is expected to enhance invasion management and mitigate biofouling issues in water diversion projects worldwide.展开更多
An algorithm for simulating free surface flows is presented using large time step based on the wave-propagation method proposed by LeVeque,and an exact Riemann solver is used.A multiple wave approximation approach was...An algorithm for simulating free surface flows is presented using large time step based on the wave-propagation method proposed by LeVeque,and an exact Riemann solver is used.A multiple wave approximation approach was suggested for eliminating the discontinuities found in the rarefaction fans of dam-breaking flows.In addition,we use the random choice method to reduce non-physical oscillations.Applications demonstrate that the algorithm proposed in this paper can considerably increase the CFL number up to 25when modeling dam-break flows,while retaining satisfactory accuracy and efficiency.This suggests that our algorithm has the potential to be applied to modeling free surface flows.展开更多
基金The work was supported by the National Natural Science Foundation of China(Grant No.51978540).
文摘The composite pile consisting of core-pile and surrounding cement-enhanced soil is a promising pile foundation in recent years.However,how and to what extent the cement-enhanced soil influences the ultimate lateral resistance has not been fully investigated.In this paper,the ultimate lateral resistance of the composite pile was studied by finite element limit analysis(FELA)and theoretical upper-bound analysis.The results of FELA and theoretical analysis revealed three failure modes of laterally loaded composite piles.The effects of the enhanced soil thickness,strength,and pile-enhanced soil interface characteristics on the ultimate lateral resistance were studied.The results show that increasing the enhanced soil thickness leads to a significant improvement on ultimate lateral resistance factor(N P),and there is a critical thickness beyond which the thickness no longer affects the N P.Increasing the enhanced soil strength induced 6.2%-232.6%increase of N P.However,no noticeable impact was detected when the enhanced soil strength was eight times higher than that of the natural soil.The maximum increment of N P is only 30.5%caused by the increase of interface adhesion factor(a).An empirical model was developed to calculate the N P of the composite pile,and the results show excellent agreement with the analytical results.
基金funded by the National Natural Science Foundation of China (Grant Nos. 51378131 and 51378403)
文摘How to determine reasonable position and length of anchor cable is a frequently encountered but not well addressed problem in slope reinforcement projects. In this paper, the variable-modulus elastoplastic strength reduction method （SRM） is used to obtain the stress field, displacement field, and factor of safety of slope. Slope reinforcement using anchor cables is modeled by surface loading, i.e. different distributions of surface loading represent various reinforcement schemes. Optimal reinforcement scheme of anchor cables can be determined based on slope stress and displacement fields. By comparing the factor of safety and stress field before and after slope reinforcement, it is found that better rein-forcement results can be achieved if strong reinforcement is applied upon the regions with high stress and large displacement. This method can well optimize the arrangement of anchor cables. In addition, several cases are employed to verify the proposed method.
基金supported by the National Natural Science Foundation of China under Grant No.50221903by the Ministry of Science and Technology of China under Grant No.2007BAC06B06
文摘Fluctuating snow-covered elevation （FSCE） was conceptualized and proposed to characterize within-year variation of the border between snow-covered and snow-free area in mountainous regions. Two parameters, namely median of snow flee period （Tm） and snow free duration （AT）, were defined to quantify FSCE. A regression model of FSCE was developed for the Lhasa River Basin, Niyang River Basin, and Changdu region in eastern Tibet. Statistical analysis of the snow-products data with a spatial resolution of 25km×25km shows that： （1） Tm correlates weakly with geographical and topographic factors, having the yearly mean value of July 31; （2） △T correlates significantly with the average elevation of the snow-products cell, having the yearly mean value of nearly five months （i.e., 151 days）; （3） the region begins snow disappearance in late April and finishes snow coverage in mid November, being snow-free from late June to mid September and snow-covered from December to March in the next year. In addi- tion, snow-products with higher spatial resolution will be helpful to characterize FSCE in smaller spatial scales.
基金supported by the National Key Research and Development Program of China(grant no.2021YFC3200902 and 2021YFC3200905)the National Natural Science Foundation of China(grant no.U2243222).
文摘Inter-basin water diversion projects have led to accelerated colonization of aquatic organisms,including the freshwater golden mussel(Limnoperna fortunei),exacerbating global biofouling concerns.While the influence of environmental factors on the mussel's invasion and biofouling impact has been studied,quantitative correlations and underlying mechanisms remain unclear,particularly in large-scale interbasin water diversion projects with diverse hydrodynamic and environmental conditions.Here,we examine the comprehensive impact of environmental variables on the establishment risk of the golden mussel in China's 1432-km-long Middle Route of the South-to-North Water Diversion Project.Logistic regression and multiclass classification models were used to investigate the environmental influence on the occurrence probability and reproductive density of the golden mussel.Total nitrogen,ammonia nitrogen,water temperature,pH,and velocity were identified as crucial environmental variables affecting the biofouling risk in the project.Logistic regression analysis revealed a negative correlation between the occurrence probability of all larval stages and levels of total nitrogen and ammonia nitrogen.The multiclass classification model showed that elevated levels of total nitrogen hindered mussel reproduction,while optimal water temperature enhanced their reproductive capacity.Appropriate velocity and pH levels were crucial in maintaining moderate larval density.This research presents a quantitative analytical framework for assessing establishment risks associated with invasive mussels,and the framework is expected to enhance invasion management and mitigate biofouling issues in water diversion projects worldwide.
基金supported by the National Basic Research Program of China (2011CB403304,2011CB409901)the National Natural Science Foundation of China (51039004,51109009)
文摘An algorithm for simulating free surface flows is presented using large time step based on the wave-propagation method proposed by LeVeque,and an exact Riemann solver is used.A multiple wave approximation approach was suggested for eliminating the discontinuities found in the rarefaction fans of dam-breaking flows.In addition,we use the random choice method to reduce non-physical oscillations.Applications demonstrate that the algorithm proposed in this paper can considerably increase the CFL number up to 25when modeling dam-break flows,while retaining satisfactory accuracy and efficiency.This suggests that our algorithm has the potential to be applied to modeling free surface flows.
