A similarity experiment study is conducted to investigate the evolution characteristics of temperature field and frozen wall closure judgment criteria for the inclined shaft, under inclined holes freezing condition using an adjustable-angle freeze sinking analogous instrument. The changes of temperature and frozen wall thickness with the freezing time in the inclined shaft section, are recorded in real time, and the water pressure of axial and radial hydrological holes are measured. The results demonstrate that the soil temperature change can be divided into three stages under the conditions of salt-water temperature of -32°C and flow rate of 3.18 m/s: rapid cooling before reaching the freezing point, slow cooling in the process of freezing latent heat release, and accelerated cooling and stabilization after freezing latent heat release. The distance from the freezing pipe is the main factor affecting the freezing wall temperature. Affected by the arched arrangement of frozen pipes, the freezing speed in the position of arch crown and arch baseline is slower than the position of wall corner and base plate. A new judgment criterion of frozen wall closure based on the water pressure of the axial hydrological pipe is recommended. In all, this paper has an enlightenment significance for understanding the evolution of the soil temperature field, and predicting the frozen wall closure time in applications of the inclined holes freezing method for the inclined shaft.

Electrical resistivity is a sensitive indicator of rock damage, yet the quantitative link between pore-structure change and resistivity response under varied hydro-thermo-mechanical conditions remains poorly constrained. In this study, triaxial compression tests were conducted on saturated limestone at confining pressures of 5–20 MPa, pore pressures of 0–9 MPa and temperatures of 20–80 °C, with synchronous measurement of electrical resistivity and pore volume; in situ X-ray computed tomography (X-CT) was performed on miniature specimens at six characteristic loading stages to resolve the accompanying mesoscale pore-structure evolution. Resistivity tracked pore volume closely, rising to at most 1.16 times its initial value as pre-existing microcracks closed, then falling once crack propagation restored fluid connectivity, with the turning point occurring at approximately 50% of the peak deviatoric stress. A resistivity change rate per unit pore volume (ρ′) is introduced to separate the two contributions: its stage-averaged magnitude during unstable crack propagation is about 8.5 times that during linear compression, showing that crack opening alters resistivity far more efficiently than closure of an equivalent pore volume. Consistently, the cementation exponent decreased monotonically throughout loading while the electrical tortuosity reversed from increasing to decreasing at crack initiation, indicating that deformation reorganizes the topology of the conductive network rather than merely its volume. X-CT reconstruction shows pore orientation migrating progressively toward the loading axis, with 93% of the pore volume concentrated within the 18–27° interval after failure, matching the macroscopic shear angle. Crack connectivity, rather than pore fluid content, therefore governs resistivity in damaged limestone, providing a quantitative basis for resistivity-based early warning of rock mass instability in underground engineering.

Carbon-based shape-stabilized phase change materials (SSPCMs) are promising for thermal energy storage, but their performance is often limited by low PCM loading. Enhancing the compatibility between the PCM and supporting matrix is an effective approach to address this issue. Herein, biomass waste was converted into activated biochar supports through chemical treatment with different agents, a process that simultaneously regulated the construction of micro- and mesopores and enriched surface functional groups. This led to optimal compatibility and interaction with lauric acid (LA) and myristic acid (MA). The prepared SSPCM demonstrates excellent leak-free performance with a high PCM loading of 81%. The composite also exhibits a high thermal energy storage capacity, with melting and crystallization enthalpies of 134.0 J g⁻¹ and 106.4 J g⁻¹, respectively. Furthermore, an SSPCM-based coating displays effective temperature regulation in a simulated indoor environment. This work provides a new insight into the design of cost-effective, high-performance thermal storage materials.

Artificial ground freezing is widely adopted for shaft construction in thick alluvium, yet the mechanical and microstructural responses of surrounding deep clay to freeze–thaw under high pressure remain poorly understood, and the assessment of shaft stability lacks a reliable foundation. Deep clay specimens collected from the Longgu Coal Mine in Shandong Province, China, were subjected to freeze–thaw (FT) under high-pressure and triaxial shear tests under varied initial liquidity indices, confining pressures and freezing temperatures. Particle-size distribution and pore structure were further characterized. Unfrozen specimens show strain-softening behavior and localized shear failure, whereas most FT specimens exhibit strain-hardening responses with bulging-dominated plastic failure, accompanied by a 29–69% reduction in shear strength. A predominant pore-size range remains 2–10 nm, whereas the specific surface area decreases and the average pore diameter increases. Under high stress, freeze–thaw induced particle refinement and pore reconstruction, which is proposed as a key mechanism contributing to strength loss of deep clay. The microstructural evolution and performance degradation of deep clay under the tested conditions correlate strongly with its initial physico-mechanical state. These findings provide a theoretical basis for evaluating shaft-wall stability and mitigating freeze–thaw damage during shaft construction using artificial ground freezing in deep alluvial strata.