A comprehensive understanding of the dynamic frictional characteristics in rock joints under high normal load and strong confinement is essential for ensuring the safety of deep engineering construction and mitigating...A comprehensive understanding of the dynamic frictional characteristics in rock joints under high normal load and strong confinement is essential for ensuring the safety of deep engineering construction and mitigating geological disasters.This study conducted shear experiments on rough rock joints under displacement-controlled dynamic normal loads,investigating the shear behaviors of joints across varying initial normal loads,normal loading frequencies,and normal loading amplitudes.Experimental results showed that the peak/valley shear force values increased with initial normal loads and normal loading frequencies but showed an initial increase followed by a decrease with normal loading amplitudes.Dynamic normal loading can either increase or decrease shear strength,while this study demonstrates that higher frequencies lead to enhanced friction.Increased initial normal loading and normal loading frequency result in a gradual decrease in joint roughness coefficient(JRC)values of joint surfaces after shearing.Positive correlations existed between frictional energy dissipation and peak shear forces,while post-shear joint surface roughness exhibited a negative correlation with peak shear forces through linear regression analysis.This study contributes to a better understanding of the sliding responses and shear mechanical characteristics of rock joints under dynamic disturbances.展开更多
A laboratory salt-water dynamics experiment using unsaturated soils in packed silt loam and clay soil columns withdifferent soil texture profiles and groundwater levels under crops were conducted to study the changes ...A laboratory salt-water dynamics experiment using unsaturated soils in packed silt loam and clay soil columns withdifferent soil texture profiles and groundwater levels under crops were conducted to study the changes of salt-waterdynamics induced by water uptake of crops and to propose the theoretical basis for the regulation and control of salt-water dynamics as well as to predict salinity levels. The HYDRUS 1D model was applied to simulate the one-dimensionalmovement of water and salt transport in the soil columns. The results showed that the salts mainly accumulated in theplow layer in the soil columns under crops. Soil water and salt both moved towards the plow layer due to soil waterabsorption by the crop root system. The salt contents in the column with lower groundwater were mostly greater thanthose with high groundwater. The water contents in the soil columns increased from top to the bottom due to plant rootwater uptake. The changes in groundwater level had little influence on water content of the root zone in the soil columnswith crop planting. Comparison between the simulated and the determined values showed that model simulation resultswere ideal, so it is practicable to do numerical simulation of soil salt and water transport by the HYDRUS 1D model.Furthermore, if the actual movement of salt and water in fields is to be described in detail, much work needs to be done.The most important thing is to refine the parameters and select precise boundary conditions.展开更多
To study the dynamics of mixed traffic flow consisting of motorized and non-motorized vehicles, a carfollowing model based on the principle of collision free and cautious driving is proposed. Lateral friction and over...To study the dynamics of mixed traffic flow consisting of motorized and non-motorized vehicles, a carfollowing model based on the principle of collision free and cautious driving is proposed. Lateral friction and overlapping driving are introduced to describe the interactions between motorized vehicles and non-motorized vehicles. By numerical simulations, the flux-density relation, the temporal-spatial dynamics, and the velocity evolution are investigated in detail The results indicate non-motorized vehicles have a significant impact on the motorized vehicle flow and cause the maximum flux to decline by about 13%. Non-motorized vehicles can decrease the motorized vehicle velocity and cause velocity oscillation when the motorized vehicle density is low. Moreover, non-motorized vehicles show a significant damping effect on the oscillating velocity when the density is medium and high, and such an effect weakens as motorized vehicle density increases. The results also stress the necessity for separating motorized vehicles from non-motorized vehicles.展开更多
The hot compressive deformation of extruded AZ31magnesium alloy with the mass fractions of Al and Zn equal to 3 % and 1 % respectively is studied by a Gleeble-1500D thermal mechanical simulator over the temperature ra...The hot compressive deformation of extruded AZ31magnesium alloy with the mass fractions of Al and Zn equal to 3 % and 1 % respectively is studied by a Gleeble-1500D thermal mechanical simulator over the temperature range from 200 ℃ to 400 ℃ and the strain rate from 10-3 s-1 to 100 s-1. The true stress-strain curves of the strain of 65 % are tested. The deformation activation energy is obtained and the flow stress model is established by analyzing the effects of strain rate and temperature on the flow stress. Zener-Hollomon parameter is introduced to describe the softening behaviors of AZ31 magnesium alloy resulted from dynamic recrystallization during the hot compressive deformation, whose natural logarithm is linear with the critical strain of dynamic recrystallization.展开更多
基金Projects(52174092,51904290)supported by the National Natural Science Foundation,ChinaProject(BK20220157)supported by the Natural Science Foundation of Jiangsu Province,China+1 种基金Project(232102321009)supported by Henan Province Science and Technology Key Project,ChinaProject(2022YCPY0202)supported by Fundamental Research Funds for the Central Universities,China。
文摘A comprehensive understanding of the dynamic frictional characteristics in rock joints under high normal load and strong confinement is essential for ensuring the safety of deep engineering construction and mitigating geological disasters.This study conducted shear experiments on rough rock joints under displacement-controlled dynamic normal loads,investigating the shear behaviors of joints across varying initial normal loads,normal loading frequencies,and normal loading amplitudes.Experimental results showed that the peak/valley shear force values increased with initial normal loads and normal loading frequencies but showed an initial increase followed by a decrease with normal loading amplitudes.Dynamic normal loading can either increase or decrease shear strength,while this study demonstrates that higher frequencies lead to enhanced friction.Increased initial normal loading and normal loading frequency result in a gradual decrease in joint roughness coefficient(JRC)values of joint surfaces after shearing.Positive correlations existed between frictional energy dissipation and peak shear forces,while post-shear joint surface roughness exhibited a negative correlation with peak shear forces through linear regression analysis.This study contributes to a better understanding of the sliding responses and shear mechanical characteristics of rock joints under dynamic disturbances.
基金the National Key Basic Research Support Foundation (NKBRSF) of China (No. G1999011803),the National Natural Science Foundation of China (Nos. 40371058 and 40471018), the Jiangsu Provincial Society Deve-lopment Program of China (No. BS2003005), and the Institute of Geography and Limnology, Chinese Academy of Sciences(No. S250020).
文摘A laboratory salt-water dynamics experiment using unsaturated soils in packed silt loam and clay soil columns withdifferent soil texture profiles and groundwater levels under crops were conducted to study the changes of salt-waterdynamics induced by water uptake of crops and to propose the theoretical basis for the regulation and control of salt-water dynamics as well as to predict salinity levels. The HYDRUS 1D model was applied to simulate the one-dimensionalmovement of water and salt transport in the soil columns. The results showed that the salts mainly accumulated in theplow layer in the soil columns under crops. Soil water and salt both moved towards the plow layer due to soil waterabsorption by the crop root system. The salt contents in the column with lower groundwater were mostly greater thanthose with high groundwater. The water contents in the soil columns increased from top to the bottom due to plant rootwater uptake. The changes in groundwater level had little influence on water content of the root zone in the soil columnswith crop planting. Comparison between the simulated and the determined values showed that model simulation resultswere ideal, so it is practicable to do numerical simulation of soil salt and water transport by the HYDRUS 1D model.Furthermore, if the actual movement of salt and water in fields is to be described in detail, much work needs to be done.The most important thing is to refine the parameters and select precise boundary conditions.
基金Supported by the National Basic Research Program of China under Grant No.2006CB705500the National Natural Science Foundation of China under Grant Nos.70631001 and 70701004
文摘To study the dynamics of mixed traffic flow consisting of motorized and non-motorized vehicles, a carfollowing model based on the principle of collision free and cautious driving is proposed. Lateral friction and overlapping driving are introduced to describe the interactions between motorized vehicles and non-motorized vehicles. By numerical simulations, the flux-density relation, the temporal-spatial dynamics, and the velocity evolution are investigated in detail The results indicate non-motorized vehicles have a significant impact on the motorized vehicle flow and cause the maximum flux to decline by about 13%. Non-motorized vehicles can decrease the motorized vehicle velocity and cause velocity oscillation when the motorized vehicle density is low. Moreover, non-motorized vehicles show a significant damping effect on the oscillating velocity when the density is medium and high, and such an effect weakens as motorized vehicle density increases. The results also stress the necessity for separating motorized vehicles from non-motorized vehicles.
基金Funded by the National "863" Foundation (Grant No. 2001AA351050)
文摘The hot compressive deformation of extruded AZ31magnesium alloy with the mass fractions of Al and Zn equal to 3 % and 1 % respectively is studied by a Gleeble-1500D thermal mechanical simulator over the temperature range from 200 ℃ to 400 ℃ and the strain rate from 10-3 s-1 to 100 s-1. The true stress-strain curves of the strain of 65 % are tested. The deformation activation energy is obtained and the flow stress model is established by analyzing the effects of strain rate and temperature on the flow stress. Zener-Hollomon parameter is introduced to describe the softening behaviors of AZ31 magnesium alloy resulted from dynamic recrystallization during the hot compressive deformation, whose natural logarithm is linear with the critical strain of dynamic recrystallization.
