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.

Identifying the consolidation state of building foundations forms part of structural health monitoring and condition assessment of infrastructure in service. Recovering the coefficient of consolidation of each layer from pore water pressure monitoring requires repeated solution of the layered consolidation equation during a parameter search. The forward space is therefore required to remain fixed over the entire inversion and to be adapted to the flux condition at material interfaces; classical layered eigenbases and the global sine space each satisfy only one. This study constructs two operator-adapted modal spaces that satisfy both. The permeability operator basis is generated by an unweighted eigenvalue problem for the permeability operator, whereas the frozen storage basis solves a generalized eigenvalue problem with a storage weight proportional to the vertical permeability. Both depend only on the known layer positions and the relative permeability profile, not on its absolute magnitude. Under a unified projection, propagation, and full-order finite element reference, the three spaces are compared in a high-contrast four-layer configuration. Among the tested dimensions, the operator-adapted spaces first reach a full-period relative error of 10⁻² at 20 modes and the global sine space at 80. After the initial layer t < 10⁻³, the errors of the operator-adapted spaces decrease approximately as K^−2.1 to K^−4.1, compared with about K⁻¹ for the sine space, and neither operator-adapted basis is uniformly more accurate than the other. In a fixed four-layer geometry, the reduced-order gain increases with the permeability contrast. Within the same operator-adapted space, direct matrix propagation combined with bounded least squares yields lower parameter and field errors than a neural parameterization of the time coefficients. These results provide a quantitative basis for offline space construction and online solver selection in parameter identification for foundation consolidation monitoring.

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.