Due to the large temperature fluctuations between day and night during the transition from winter to spring, soil sites in seasonally frozen soil areas go through repeated freeze–thaw cycles. During these cycles, the water in the soil undergoes phase transformation and migration, which changes the physical and mechanical properties of the soil and directly affects the stability and durability of the soil site. In order to explore the feasibility of using the ZDS-2 organosilicon reinforcement agent for the anti-freeze-and-thaw protection of soil sites, Qingtai site soil and the ZDS-2 organosilicon reinforcement agent were used as raw materials. The optimal ratio of modified soil samples with different freeze–thaw cycles was obtained by laboratory tests. The strengthening mechanism of the ZDS-2 organosilicon reinforcement agent under freeze–thaw cycles was revealed by a microscopic test. The test results showed that the ZDS-2 organosilicon reinforcement agent can inhibit the volume expansion of soil samples caused by the freeze–thaw cycle. After nine freeze–thaw cycles, the shear strength of the soil samples, to which 15% ZDS-2 organosilicon reinforcement agent was added, increased by 53.4% on average compared with plain soil. The highly cross-linked organic–inorganic hybrid network structure formed between the siloxane group in the ZDS-2 organosilicon reinforcement agent and the soil particles can fill the pores and form a protective layer. The experimental results provided a basis and reference for the research of freeze–thaw-resistant materials for soil sites in seasonally frozen soil areas.
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