In this study, the impacts of various grouting methods and volumes on the vertical bearing characteristics of model piles in clay strata were investigated through indoor static load tests on one ungrouted model pile and two model piles with grouting at the pile tip, as well as two model piles with distributed grouting at the pile tip and along the pile side. These tests were performed in conjunction with data obtained from optical fiber sensors that monitored changes in the internal forces of the pile body. The results indicate that, compared to the ungrouted model pile Z1, the ultimate bearing capacities of the grouted model piles Z2 to Z5 were increased by 83.9%, 175.0%, 125.0%, and 253.6%, respectively. Additionally, the displacements at the pile tops after failure reached 57.6%, 62.3%, 69.5%, and 73.5% that of the ungrouted model pile Z1. These results demonstrate that post-grouting can significantly enhance the ultimate bearing capacity of model piles and reduce settlement at the pile top. Under various loads, the axial force of the pile body decreases gradually with the increasing depth of the pile foundation and increases with the increasing load at the pile top. The increase in the ultimate average side friction resistance and ultimate tip resistance of the grouted model piles (i.e., Z2 to Z5), in comparison to the ungrouted pile, was positively correlated with the grouting volume at the pile tip and along the pile side. All five model piles displayed the characteristics of friction piles.

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.

Biodeterioration poses a significant challenge in the conservation of cultural heritage, particularly for earthen sites in humid environments, which are highly susceptible due to their inherent material properties. To address the diverse biological threats affecting such sites, we developed a novel broad-spectrum biocide, FACA, formulated by combining phenylcarbamoylthiazoles and isothiaquinolones to achieve triple efficacy: antimicrobial, anti-algal, and anti-lichen effects. Laboratory assessments demonstrated FACA’s rapid efficacy in eliminating molds, algae, and lichens. A 12-month field application at the Sanyangzhuang earthen site (Neihuang, Henan) yielded excellent results, confirming long-term protection against biological colonization without recurrence. Crucially, the treatment exhibited no adverse effects on the earthen sites, enabling sustainable coexistence between the heritage site and its surrounding ecosystem. These findings support the applicability of FACA for surface treatment across various humid earthen archeological sites.