Effects of Freeze-thaw Cycles and Soil Water Contents on Disintegration Characteristics of Brown Earth
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S151.7

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Supported by the National Natural Science Foundation of China (No. 41601284),the National Key Research and Development Program of China (No. 2016YFE0202900),and the Science Research Project of Education Department of Liaoning(No. LSNQN202023)

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    Abstract:

    【Objective】 Undisturbed brown earth soils from 5~7 cm and 25~27 cm depths in the Shenyang area of China were collected for this research. The effects of freeze-thaw cycles and soil water contents on the disintegration characteristics of the soils were analyzed. 【Method】 Based on meteorological data and field observation, five freeze-thaw cycles were designed. The weighed water contents of the soil samples were regulated to 10%, 15%, 20%, 25% and 35%, respectively, and the disintegration process was measured. 【Result】 1) The soil disintegration had four phases, including the rapid water absorption phase, exponential disintegration phase, step disintegration phase, and disintegration completion phase. In the four phases, the exponential disintegration phase was regarded as the main disintegration process. Importantly, during the exponential disintegration phase, the soil sample collapsed continuously due to pulling or losing support. Also, the disintegration rate in the exponential disintegration phase and non-capillary water content showed similar behavior as the increasing freeze-thaw cycle. According to the two fitting surfaces, there was a most easily disintegrating soil water content in the range10%~15% in which the total disintegration rate was largest. When the water contents were 25% and 35%, all soil samples skipped the exponential disintegration phase and directly entered the step disintegration phase. The total disintegrations of 5~7 cm and 25~27 cm soils were very small under 35% soil water content, and was no more than 6.93% and 11.14%, respectively. 2) Over-consolidation was observed on soil samples with 10% and 15% water contents, and the polarization distribution of soil pores was accelerated under the freeze-thaw cycles. The disintegration rate of the exponential disintegration phase and non-capillary water content of both soil samples was increased after continuous freeze-thaw cycles. Under the freeze-thaw cycles, the structure of soil samples with 25% and 35% water contents was destroyed, soil pores were expanded with an internal settlement, and the water absorption capacity was reduced. 3) The pore difference of 25~27 cm soil sample was slightly larger, the control ability of electric double layer to free water was inhibited by the higher clay content, which resulted in a higher total disintegration rate. 【Conclusion】 The ability of soil to resist erosion from inside to outside was transformed into the ability from outside to inside under freeze-thaw cycles. All the findings may serve as a data basis for brown earth soil erosion research.

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ZHU Longxiang, FAN Haoming, MA Renming. Effects of Freeze-thaw Cycles and Soil Water Contents on Disintegration Characteristics of Brown Earth[J]. Acta Pedologica Sinica,2023,60(1):77-88.

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History
  • Received:March 02,2021
  • Revised:August 17,2021
  • Adopted:October 13,2021
  • Online: October 14,2021
  • Published: