Monitoring and modelling surface deformation are crucial components of understanding the freeze-thaw process and preventing disasters in permafrost regions. However, previous methods had limitations that inhibited the interpretation of freeze-thaw deformation, such as a lack of physical meaning, an inability to reflect the physical freeze-thaw process and consideration of only a single external factor's impact on permafrost deformation. This study proposes an improved degree-day model (IDM) for quantitatively isolating surface deformation using interferometric synthetic aperture radar (InSAR) technology over permafrost. We considered the effect of soil moisture variation on permafrost deformation and incorporated interannual variation in the freeze-thaw process due to climate change. By applying small baseline subset (SBAS) technology to Sentinel-1 InSAR measurements over the Wudaoliang permafrost region on the Qinghai-Tibet Plateau from 2018 to 2019, we estimated long-term and seasonal permafrost deformation. The reliability of InSAR results was validated using in situ measurements, with root mean square errors (RMSEs) less than 10 mm. The results showed that the average linear deformation rates in 2018 and 2019 were -3.8 mm a-1 and -11.0 mm a-1, respectively, and the maximum seasonal deformations were 15.7 mm and 13.2 mm, respectively. Compared with the original degree-day model (ODM), the method used in this study produced smaller residual deformations of 6.9 mm and 6.4 mm, highlighting its ability to improve a quantitative description of permafrost deformation.

Seismic-induced submarine landslides pose significant risks to offshore structures. To enhance our understanding of this phenomenon, we have developed a CFD-MPM capable of simulating complete mechanisms behind earthquake induced submarine landslide. Recent centrifuge tests have demonstrated that the permeability of marine sediment is a critical factor in determining the failure mechanism of submarine landslides. Specifically, a lower permeability increases the likelihood of a slope transitioning from failure to gravity debris flow. Our CFDMPM, validated with centrifuge tests, supports this conclusion. Moreover, we conducted a sensitivity analysis of seismic-induced submarine landslides using the CFD-MPM. In the case of contractive soil, a lower permeability leads to slower dissipation of excess pore water pressure, resulting in longer submarine debris flow runouts. Additionally, in the case of softening soil, a lower permeability increases the chances of spreads as a failure mechanism, while a higher permeability favours retrogressive flow slides. This study sheds light on the diverse effects of sediment permeability on submarine landslide mechanisms, offering crucial insights for hazard assessment and mitigation strategies in offshore engineering and coastal management.

The red stratum soft rock, contained extensively in the deep soil-rock mixture (SRM) backfill area of southwest China, exhibits significant water-disintegrating properties that greatly impact the foundation's bearing capacity and deformation failure in this region. This study introduced the large-scale triaxial test to investigate the mechanical deformation characteristics of clay-red stratum soft rock mixture before and after wetting. Simultaneous, combined with the results of test, the law of water disintegration of red stratum soft rock was revealed, and its effects were analyzed in detail. The results show that: (1) Wetting intensified the crushing of rock blocks, resulting in the reduction of shear strength and critical strain of the samples, the decrease of critical internal friction angle and secant modulus, and the significant increase of the relative crushing rate of rock blocks; (2) The most significant increase and decrease of the content before and after the test occur in the particles with the particle size of 0.5-2 mm and 20-40 mm, respectively; (3) Wetting-induced breakage of the red stratum soft rock mainly occurs during the first two hours after encountering water; (4) An increase in confining pressure exacerbates the influence of wetting. Additionally, based on the theory of non-linear elasticity, with the assuming that the reduction of secant modulus causes the wetting deformation, a theoretical calculation model of the wetting axial strain was proposed. Through comparing the calculated results with the measured values obtained by using the double-line method and single-line method test, it is found that the calculation method can accurately predict the wetting axial strain of SRM and be used for quantitative analysis of wetting deformation.