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To investigate the soil hydraulic characteristics across a wide range of suctions (0-10 MPa) of Benggang soil, the soil water holding capacities of different soil layers in Benggang was determined using the pressure film meter and the filter paper methods. Traditional and modified Van Genuchten-Mualem (VG) models were used to fit the soil moisture characteristics curves. The results showed that the water-holding curves determined by the pressure film meter and filter paper methods intersected and tended to overlap. This observation suggested combining the two measurement methods to obtain soil moisture characteristic curves over a wide suction range. Further, within the wide suction range, the water-holding capacity of the sandy soil layer was higher than that of the red and detritus soil layers in the low suction stage (h<0.1 MPa). However, in the high suction stage (h>0.1 MPa), the red soil layer had the highest water-holding capacity. Both the traditional and modified VG models were able to fit the soil moisture characteristics of each soil layer of the Benggang wall with a root mean square error of less than 0.021 5. The Nash efficiency and correlation coefficients were greater than 0.926 6 and 0.899 1, respectively. Noticeably, the modified VG model was more suitable for describing the soil moisture characteristic curves of the Benggang wall across a wide suction range. The residual values of the soil moisture characteristic curves for the red, sandy, and detritus layers were 378 kPa (corresponding to a water content of 18.82%), 173 kPa (corresponding to a water content of 18.95%), and 92 kPa (corresponding to a water content of 18.41%), respectively. Finally, the form of the segmental function (with the residual value as the inflection point) was more suitable for describing the unsaturated hydraulic conductivity over a wide suction range of Benggang soils than the conventional VG model. [ABSTRACT FROM AUTHOR]

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