The development of fissures in expansive soils has a great effect on the stability of slope. Of the three phases of soils,the gas phase and solid phase are relatively insulated,so the average resistivity of soils can ...The development of fissures in expansive soils has a great effect on the stability of slope. Of the three phases of soils,the gas phase and solid phase are relatively insulated,so the average resistivity of soils can be calculated from the resistivity of the liquid phase. On this basis,the two-part model of resistivity changing with the water saturation of the expansive soil can be deduced. A 2-D resistance grid model is established based on simulating the resistance of ver-tically developed fissures. Variation in measured resistance of vertically developed fissures at different positions can be calculated from this model. Fissure development can be inversely determined from the variation in the measured resis-tance. Finally,the model is verified by an indoor resistivity test for remolded soil samples,indicating that the test result agrees well with that of the model established.展开更多
The relation between ice pressure and load as a criterion of segregated ice initiation is introduced into the rigid ice model to simulate frost heave in saturated and granular soil. The calculated results show that un...The relation between ice pressure and load as a criterion of segregated ice initiation is introduced into the rigid ice model to simulate frost heave in saturated and granular soil. The calculated results show that unfrozen water content, thermal conductivity and hydraulic conductivity change greatly in frozen fringe. In numerical simulations, the influence of load, hydraulic conductivity and property of soil containing water on the process of soil freezing are analyzed, and the simulation curves such as cumulative heave, the change of depth of frozen and the distributions of water content are similar to the observations reported elsewhere.展开更多
Soil N transformations using the polyvinyl chloride （PVC） closed-top tube in situ incubation method were studied in Nanchang urban forests of the mid-subtropical region of China in different months of 2007. Four plo...Soil N transformations using the polyvinyl chloride （PVC） closed-top tube in situ incubation method were studied in Nanchang urban forests of the mid-subtropical region of China in different months of 2007. Four plots of 20 m × 20 m were established in four different plant communities that represented typical successional stages of forest development including shrubs, coniferous forest, mixed forest and broad- leaved forest. Average concentrations of soil NH4^＋-N from January to December were not different among the four plant communities. The concentrations of soil NO3^--N and mineral N, and the annual rotes of ammonification, nitrification and net N-mineralization under the early successional shrub community and coniferous forest were generally lower than that of the late successional mixed and broad-leaved forests （p〈0.05）. Similar differences among the plant communities were also shown in the relative nitrification index （NH4^＋-N/NO3^--N） and relative nitrification intensity （nitrification rate/net N-mineralization rate）. The annual net N-mineralization rate was increased from younger to older plant communities, from 15.1 and 41.4 kg.ha^-1.a^-1 under the shrubs and coniferous forest communities to 98.0 and 112.9 kg.ha^-1.a^-1 under the mixed and broad-leaved forests, respectively. Moreover, the high annual nitrification rates （50-70 kg.ha^-1.a^-1） and its end product, NO3-N （2.4-3.8 mg·kg^-1）, under older plant communities could increase the potential risk of N loss. Additionally, the temporal patterns of the different soil N variables mentioned above varied with different plant community due to the combined affects of natural biological processes associated with forest maturation and urbanization. Our results indicated that urban forests are moving towards a state of＂N saturation＂ （extremely niUification rate and NO3^--N content） as they mature.展开更多
By testing soil organic matter （SOM） contents, soil water contents （SWC） within low suctions, and saturated infiltration rates of samples taken from east slope of Gongga Mountain of China, the enhancive effects of...By testing soil organic matter （SOM） contents, soil water contents （SWC） within low suctions, and saturated infiltration rates of samples taken from east slope of Gongga Mountain of China, the enhancive effects of SOM contents on SWC within low suctions and saturated infiltration rates were quantified. The simulated functions might be applied on regional experience forest-hydrology model. The improving function of protecting forest floor and increasing SOM contents on forest ecosystem hydrological effects were also embodied.展开更多
管桩作为一种常用的桩基础,在实际工程中被广泛应用,其动力响应分析具有重要研究价值。基于弹性动力学原理和黏弹性饱和土模型,考虑了土骨架的非流动黏性和管桩的横向惯性效应,研究了分数阶黏弹性饱和土中大直径管桩在竖向动载荷作用下...管桩作为一种常用的桩基础,在实际工程中被广泛应用,其动力响应分析具有重要研究价值。基于弹性动力学原理和黏弹性饱和土模型,考虑了土骨架的非流动黏性和管桩的横向惯性效应,研究了分数阶黏弹性饱和土中大直径管桩在竖向动载荷作用下的动力特性。首先,基于Biot动力固结理论和分数阶标准线性固体(fractional-order standard linear solid,简称FSLS)模型,建立了分数阶黏弹性饱和土在柱坐标系下的波动方程。其次,基于Rayleigh-Love杆模型并考虑管桩的横向惯性效应,推导了管桩的桩顶动阻抗解析解答。最后,通过算例分析,研究了分数阶模型参数、管桩横向惯性效应、桩长和土体渗透力对管桩桩顶动阻抗的影响规律。结果表明:饱和土体骨架FSLS模型参数中分数阶数和应变松弛时间的增大以及应力松弛时间的减小都会增大桩顶动阻抗;管桩的横向惯性效应在高频区段对降低桩顶动阻抗尤为明显;缩小管桩外半径和扩大其内半径以及增加桩长,降低土体渗透性均有助于提高桩顶动阻抗。展开更多
基金Project 50579017 supported by the National Natural Science Foundation of China
文摘The development of fissures in expansive soils has a great effect on the stability of slope. Of the three phases of soils,the gas phase and solid phase are relatively insulated,so the average resistivity of soils can be calculated from the resistivity of the liquid phase. On this basis,the two-part model of resistivity changing with the water saturation of the expansive soil can be deduced. A 2-D resistance grid model is established based on simulating the resistance of ver-tically developed fissures. Variation in measured resistance of vertically developed fissures at different positions can be calculated from this model. Fissure development can be inversely determined from the variation in the measured resis-tance. Finally,the model is verified by an indoor resistivity test for remolded soil samples,indicating that the test result agrees well with that of the model established.
基金The National Natural Science Founda-tion of China (No.40501017)the Innovation Program of the Chinese Academy of Sciences (No.KZCX1-SW-06)
文摘The relation between ice pressure and load as a criterion of segregated ice initiation is introduced into the rigid ice model to simulate frost heave in saturated and granular soil. The calculated results show that unfrozen water content, thermal conductivity and hydraulic conductivity change greatly in frozen fringe. In numerical simulations, the influence of load, hydraulic conductivity and property of soil containing water on the process of soil freezing are analyzed, and the simulation curves such as cumulative heave, the change of depth of frozen and the distributions of water content are similar to the observations reported elsewhere.
基金supported by grants from the National Natural Science Foundation of China (Nos. 30960311 &30600473)
文摘Soil N transformations using the polyvinyl chloride （PVC） closed-top tube in situ incubation method were studied in Nanchang urban forests of the mid-subtropical region of China in different months of 2007. Four plots of 20 m × 20 m were established in four different plant communities that represented typical successional stages of forest development including shrubs, coniferous forest, mixed forest and broad- leaved forest. Average concentrations of soil NH4^＋-N from January to December were not different among the four plant communities. The concentrations of soil NO3^--N and mineral N, and the annual rotes of ammonification, nitrification and net N-mineralization under the early successional shrub community and coniferous forest were generally lower than that of the late successional mixed and broad-leaved forests （p〈0.05）. Similar differences among the plant communities were also shown in the relative nitrification index （NH4^＋-N/NO3^--N） and relative nitrification intensity （nitrification rate/net N-mineralization rate）. The annual net N-mineralization rate was increased from younger to older plant communities, from 15.1 and 41.4 kg.ha^-1.a^-1 under the shrubs and coniferous forest communities to 98.0 and 112.9 kg.ha^-1.a^-1 under the mixed and broad-leaved forests, respectively. Moreover, the high annual nitrification rates （50-70 kg.ha^-1.a^-1） and its end product, NO3-N （2.4-3.8 mg·kg^-1）, under older plant communities could increase the potential risk of N loss. Additionally, the temporal patterns of the different soil N variables mentioned above varied with different plant community due to the combined affects of natural biological processes associated with forest maturation and urbanization. Our results indicated that urban forests are moving towards a state of＂N saturation＂ （extremely niUification rate and NO3^--N content） as they mature.
基金This research was supported by the Knowledge Innovation Project of Chinese Academy of Sciences (KZCX2-SW-319).
文摘By testing soil organic matter （SOM） contents, soil water contents （SWC） within low suctions, and saturated infiltration rates of samples taken from east slope of Gongga Mountain of China, the enhancive effects of SOM contents on SWC within low suctions and saturated infiltration rates were quantified. The simulated functions might be applied on regional experience forest-hydrology model. The improving function of protecting forest floor and increasing SOM contents on forest ecosystem hydrological effects were also embodied.
文摘管桩作为一种常用的桩基础,在实际工程中被广泛应用,其动力响应分析具有重要研究价值。基于弹性动力学原理和黏弹性饱和土模型,考虑了土骨架的非流动黏性和管桩的横向惯性效应,研究了分数阶黏弹性饱和土中大直径管桩在竖向动载荷作用下的动力特性。首先,基于Biot动力固结理论和分数阶标准线性固体(fractional-order standard linear solid,简称FSLS)模型,建立了分数阶黏弹性饱和土在柱坐标系下的波动方程。其次,基于Rayleigh-Love杆模型并考虑管桩的横向惯性效应,推导了管桩的桩顶动阻抗解析解答。最后,通过算例分析,研究了分数阶模型参数、管桩横向惯性效应、桩长和土体渗透力对管桩桩顶动阻抗的影响规律。结果表明:饱和土体骨架FSLS模型参数中分数阶数和应变松弛时间的增大以及应力松弛时间的减小都会增大桩顶动阻抗;管桩的横向惯性效应在高频区段对降低桩顶动阻抗尤为明显;缩小管桩外半径和扩大其内半径以及增加桩长,降低土体渗透性均有助于提高桩顶动阻抗。
