The reliability of the absorbing layer is crucial for realizing protective engineering's protection function. However, the typical wave-absorbing material, sand, is unable to fulfill its intended wave-absorbing function in areas with seasonally frozen soil. This is because the internal pores of the material become filled with ice and the particles freeze. To address this issue, alumina thin-walled hollow particles were chosen as a new wave-absorbing material. These particles can introduce the gas phase into the absorbing layer which is essential for attenuating the stress waves and its wave-absorbing capacity under freezing conditions was investigated by the split Hopkinson bar (SHPB) test. According to the test data, the alumina thin-walled hollow particles are less dense than sand and have a lower wave impedance, allowing them to reflect more incident energy. Moreover, these particles have a better capacity for dissipating the absorbed energy, as compared to sand. Under freezing circumstances, the average transmittance coefficient of alumina thin-walled hollow particles is only 21.95% to 49.30% of ordinary sand. Additionally, the particle size positively correlates with the capacity for wave-absorption. The capacity of alumina thin-walled hollow particles to shatter and release the gas phase under impact stress significantly increases the compressibility of the absorbing layer under freezing conditions, which accounts for their enhanced wave-absorbing effectiveness. The stress-strain curve specifically manifests as a smoother curve and a longer stage of plastic energy dissipation. Other than that, the dynamic deformation modulus of the material and peak stress is lower, while the peak strain is larger. The findings of this study provide a low-cost, high-reliability solution to the problem of frost damage in the absorbing layer in regions with seasonal freezing.

On July 20, 2021, over 2000 ground subsidence events and collapses occurred in Zhengzhou, China, after a heavy rainstorm. These events were mostly caused by the reduced mechanical properties of loess under moistening and repeated dynamic loading. After the conducted dynamic triaxial tests considering varying moisture content, envelope pressure and 10,000 vibrations, the dynamic properties evolution of undisturbed loess under moistening has been clarified. The experimental results showed that the dynamic strain of undisturbed loess under moistening conditions increases gradually with increasing dynamic stress, following the Hardin-Drnevich hyperbolic model. The initial dynamic shear modulus, maximum dynamic shear stress, and dynamic strength decrease linearly with increasing moisture, while the dynamic strain is the opposite, and the damping ratio is less affected by the increased moisture. The dynamic strain rises with increasing dynamic stress and moisture content considering the same vibrations. Increased vibrations and greater moisture content under identical dynamic stress cause a faster accumulation of dynamic strain in undisturbed loess, making it more susceptible to damage. The results are of guiding significance for the evaluation and analysis of the dynamic properties of loess and provide technical support for disaster prevention and mitigation in Zhengzhou.