To enhance the design and construction efficiency of artificial ground freezing (AGF) in water-rich sandy strata, this study takes the No. 2 cross-passage of Zhengzhou Metro Line 8 as a case study and conducts an integrated analysis combining field monitoring and numerical simulation. During the freezing process, a sensor network was deployed to capture real-time data on temperature distribution and pore water pressure evolution. Based on the collected measurements, a three-dimensional hydrothermal coupled model was developed using COMSOL Multiphysics 6.1 and validated against field data. The results demonstrate a distinct multi-stage evolution in the formation of the frozen curtain, with the highest heat exchange rate observed at the initial phase. Under a 50-day freezing schedule, increasing the average coolant temperature by 4 °C still yielded a frozen wall that meets the design thickness requirement. Additionally, several cost-effective freezing schemes were explored to accommodate varying construction timelines. This study supports sustainable urban infrastructure development by minimizing energy consumption during artificial ground freezing (AGF) processes.

Land subsidence is an important challenge faced by coastal cities under rapid urban development. This study focuses on the Haikou–Laocheng area and conducts time-series monitoring of land subsidence using PS-InSAR and SBAS-InSAR based on 42 Sentinel-1 SAR scenes acquired from April 2023 to April 2025, thereby deriving the spatial distribution of cumulative subsidence rates and the evolution patterns of multi-temporal cumulative subsidence. Because only ascending-orbit Sentinel-1 data were used, the reported deformation values are vertical-projected estimates converted from line-of-sight (LOS) displacement under the assumption that horizontal motion is negligible. The reliability of the monitoring results is evaluated through cross-validation between the two methods, assessing their inter-method consistency. The results indicate that the study area is dominated by slight subsidence, with vertical-projected subsidence rates mainly ranging from −6 to 3.7 mm/y, while a few uplift points are locally observed, forming an overall “stable with localized anomalies” deformation pattern. PS-InSAR and SBAS-InSAR show good consistency in overall trends, and both identify a pronounced subsidence bowl in the southwestern part of the study area, where the peak vertical-projected subsidence rates reach −25.1 mm/y and −35.1 mm/y, respectively, with outward banded attenuation. The results suggest that land subsidence in the study area is influenced by both natural factors and human activities. Specifically, rainfall shows a non-synchronous, stage-wise modulation relationship with subsidence evolution, and most high-subsidence zones are distributed in impervious surfaces such as built-up land and transportation corridors, or in low-elevation areas such as farmland. In terms of geological factors, thick, highly compressible soft soils are the primary geological control on the continued development of subsidence. These findings can provide scientific references for the prevention and control of abnormal subsidence and for urban planning and development in the Haikou–Laocheng area. The strengthened discussion clarifies the research gap, planning significance, and limitations of applying dual time-series InSAR in a data-scarce tropical coastal soft-soil setting.

Surface deformation in rapidly urbanizing coastal cities is often shaped by the interplay between hydrogeological setting and development disturbance, yet these controls remain insufficiently constrained in tropical coastal environments. Using 119 ascending Sentinel-1A scenes acquired between September 2020 and August 2025, we derived a high-density line-of-sight (LOS) deformation field over Haikou, China, through the combined use of PS-InSAR and DS-InSAR time-series analysis. The results show pronounced spatial heterogeneity, with negative LOS anomalies concentrated in reclaimed coastal sectors, port-adjacent zones, and Jiangdong New District, where cumulative LOS displacement locally approaches 90 mm. DS-InSAR increased the number of valid observations to 764,573, approximately 2.8 times that of PS-InSAR, and showed good internal consistency with collocated PS estimates (R² = 0.8048). Positive LOS zones are present but are generally weaker and more spatially diffuse than the major negative anomalies, indicating that the near-zero city-wide mean partly reflects compensation between localized negative and positive signals. Spatial attribution analysis suggests that groundwater type, aquifer water-yield property, and geological zoning provide the main hydrogeological background associated with deformation, whereas human activity intensity, road density, and land-use intensity are associated with stronger negative deformation where hydrogeological conditions are susceptible. Because the dataset is limited to a single ascending viewing geometry, the reported deformation is interpreted as LOS motion rather than a fully resolved vertical subsidence field. These results support a cautiously framed interpretation in which coastal urban deformation in Haikou is hydrogeologically conditioned and development-amplified, providing a basis for targeted monitoring and risk-informed planning in newly developed coastal districts.

Light pozzolanic soft clay has high compressibility and relatively poor structural stability, which limits its direct application in subgrade and foundation engineering. This study develops a sustainable combined stabilization–reinforcement system for lightweight volcanic ash soil using a steel slag–fly ash-based composite cementitious binder (GS) and recycled polyester fiber (RPF). Unconfined compressive strength tests, unconsolidated undrained triaxial tests, and microstructural characterization were conducted to evaluate the mechanical behavior and microstructural features of the treated soil. The results show that the GS binder markedly increased the soil strength, whereas RPF mainly improved specimen integrity and the post-peak response. Based on the single-additive and orthogonal test results, 24% GS, 0.6% RPF, and 9 mm fibers were identified as an appropriate mixture within the investigated factor levels for further mechanical evaluation. With the increase in confining pressure, the stress–strain response changes from strain softening to strain hardening. Scanning electron microscopy (SEM) observations showed fine particulate material at local particle-contact and fiber–matrix regions, while energy-dispersive X-ray spectroscopy (EDS) analysis identified a representative Ca-rich microregion containing Si and Al. The combined use of GS binder and RPF effectively improved the strength and deformation resistance of lightweight volcanic ash soft clay.