Effects of freeze-thaw cycles on saturated hydraulic conductivity of soils reclaimed with different vegetation types at an open-pit coal mine dumping site

XIONG Shuzhen; LYU Gang

doi:10.13522/j.cnki.ggps.2024207

Abstract：[Objective]Freeze-thaw cycles are a critical abiotic process that reshape soil structure.This study investigates their impact on the saturated hydraulic conductivity of soil in an open-pit coal mine in Haizhou,which is reclaimed with different vegetation types.[Method]A laboratory experiment was conducted in spring.The vegetation types studied included Ulmus pumila forestland,Rhus typhina forestland,farmland,and waste grassland.Soil samples from the top 0-20 cm soil layer was used in the experiment.The natural spring thaw environment was simulated using a constant temperature test chamber.Infiltration tests were performed with a ring infiltrometer.The saturated hydraulic conductivity was analyzed under different freeze-thaw cycles,thawing times,and before and after freeze-thaw treatments.[Result]① The saturated hydraulic conductivity decreased with increasing freeze-thaw cycles and thawing time.It also varied with vegetation type and their interactions.The saturated hydraulic conductivity measured under different vegetation types was ranked in the order of waste grassland＞Rhus typhina forestland＞Ulmus pumila forestland＞farmland.② Soil physical properties before and after freeze-thaw cycles differed between vegetation types.The freeze-thaw cycles increased soil bulk density by 0.05,0.07,0.05,and 0.02 g/cm3 for Ulmus pumila forestland,Rhus typhina forestland,farmland,and waste grassland,respectively,and reduced the saturated hydraulic conductivity by 0.8,0.49,0.2,and 0.19 mm/min,respectively.③ After freeze-thaw cycles,the saturated soil hydraulic conductivity was ranked in order of Ulmus pumila forestland＞Rhus typhina forestland＞farmland＞waste grassland.[Conclusion]Freeze-thaw cycles reduced saturated hydraulic conductivity for vegetation types,and its value was ranked in the order of Ulmus pumila forestland＞Rhus typhina forestland＞farmland＞waste grassland.Our results showed that the waste grassland was most resistant to freeze-thaw effects.