Experimental Study on the Effect of Freeze—Thaw Cycles on the Mineral Particle Fragmentation and Aggregation with Different Soil Types

Jinbang Zhai,Mingyi Zhang,Doudou Jin,Andrey Melnikov,Ze Zhang,Linzhen Yang

doi:10.3390/min11090913

Abstract

The freeze–thaw cycle can change the size and shape of soil particles, that is, cause fragmentation and aggregation of soil mineral particles, thereby affecting the soil structure, which, in turn, affects the soil properties. In addition, the process of soil mineral fragmentation and aggregation, as an event closely related to the cold climate, plays an irreplaceable role in reconstructing the climatic conditions of a certain area and a certain period of time and has important referential significance for the restoration of historical permafrost boundaries and the study of climate change. Therefore, in order to better study the effect of freeze–thaw cycles on the fragmentation and aggregation of soil mineral particles, four soil specimens were selected for this study; the freeze–thaw cycle tests were carried out 0, 3, 6, 9, 50, and 100 times, respectively, and the test results were analyzed. The results of these experiments indicate that (1) after freeze–thaw cycles, the changes in grain-size distribution are different in various soil types, and the changes are mainly concentrated in 0.001–0.1 mm; (2) the coarse particle size particles (sand, silt) can be fragmented into relatively fine-grained particles (silt, clay). The fine-grained particles (clay) cannot undergo fragmentation, and the decrease in clay is due to its aggregation; (3) with the increase in freeze–thaw cycles, the fraction change trend of four specimens is parallel to the x-axis, which means the fragmentation and aggregation of soil mineral particles are in a state of equilibrium or balance; (4) the increase in the Kvar value indicates the change in grain-size distribution, which means aggregation and fragmentation of soil mineral particles. After the 100th cycle, the Kvar value of four specimens is <0.1, which belongs to a low-intensity area; (5) the freeze–thaw cycle will change the type of soil, and after 100 freeze–thaw cycles, the soil type of specimen (H) changes from silty clay loam to silty clay; (6) during the freeze–thaw process, different types of soil have different situations of aggregation and fragmentation.

Highlights

As the atmospheric temperature changes periodically with the seasons, the soil in the seasonal and permafrost regions will inevitably undergo a periodic freeze–thaw process; the ground surface experiences more than 100 freeze–thaw cycles within a year [1].Different freeze–thaw conditions will cause the soil to form different types of texture and structure [2–4]
The change in size fraction is different in diverse soil types after the freeze–thaw process
After the freeze–thaw cycles, we found that the different soil types have different situations of the mineral particle aggregation and fragmentation—

Summary

Introduction

As the atmospheric temperature changes periodically with the seasons, the soil in the seasonal and permafrost regions will inevitably undergo a periodic freeze–thaw process; the ground surface experiences more than 100 freeze–thaw cycles within a year [1].Different freeze–thaw conditions will cause the soil to form different types of texture and structure [2–4]. Water and salt transfer cause changes in soil structure, with the initial stable state of soil particles being changed through aggregation and fragmentation, causing changes in grain-size distribution These changes may result in further variations in soil, including its composition, structure, and characteristics, all of which can lead to ecological (water-retention and nutrient-preservation capabilities, resulting in water loss, grassland degradation, desertification, etc.) and engineering (soil strength, bearing capacity of foundations, capillary water pressure in soil, and soil’s plasticity and collapsibility) problems [6]. In geology, this process is the main cause of physical weathering, and the freezing process is called a freezing weathering process [7]. Studies have found that the magnitude of freezing weathering is directly proportional to the number of freeze–thaw cycles and moisture content

Methods

Results

Discussion

Conclusion