压实黄土初始孔隙分布对持水性及V-G模型参数的影响OA

[Objective]This study aims to determine the key hydraulic parameters of unsaturated loess under different initial wet densities,investigate the variation patterns of its soil-water characteristic curve(SWCC),and examine their impact on the parameters of the van Genuchten(V-G)model,thereby providing a new perspective for elucidating the mechanism by which the initial pore structure regulates water retention.[Methods]Pressure plate tests and nuclear magnetic resonance(NMR)tests were conducted to analyze the SWCC of loess under different initial wet density conditions,investigate their influence on the parameters of the V-G model,and obtain the pore water distribution characteristics of the samples.[Results](1)In the boundary effect zone,the slope of the SWCC decreased as K and w0 increased.In the transition zone,the slope decreased as K and w0 decreased,leading to a faster descending rate of the SWCC curve and an accelerated water loss of the specimens.In the residual zone,the SWCCs gradually converged,and the residual value increased with increasing K and w0.(2)The parameter ψ0 of the air-entry value showed a linear positive relationship with K and an exponential relationship with w0.ψ0 increased with the increase of w0.The parameters of the V-G model α were logarithmically related to K and linearly related to w0.K and w0 had little influence on parameters m and n.Based on the V-G model,the SWCC model considering the coupling of saturation and compaction degree,and saturation and initial moisture content was modified.(3)As K increased,the pore structure within the soil transformed from more open pores to more uniform small and medium-sized pores.Water became more difficult to discharge within the soil,resulting in a decreased water loss rate,an increased air-entry value,and stronger water retention capacity.The T2 spectra of low w0 samples were mainly unimodal,and those of high w0 samples were mainly bimodal.With the increase of w0,the number of small pores increased and the connectivity between pores decreased,restricting the movement of water molecules and making water more difficult to discharge.Therefore,the air-entry value of the samples increased and their water retention capacity was enhanced.[Conclusion]The differences in the micro-pore structure(changes in size distribution and pore connectivity)of loess under different initial conditions are the key to the changes in its macroscopic water retention capacity.