Composite bucket foundation (CBF) is an environmentally friendly form of offshore wind power foundation. By virtue of the air-floating subdivision structure in the bucket, the foundation has a self-floating characteristic and can allow for long-distance air-floating towing and transport. In this study, first, a numerical analysis was performed on the towing motion characteristics of CBF, and the formula for foundation stability was deduced; then, we probed into the variation rules of the natural period of the foundation with draft and analyzed the response amplitude operator (RAO) responses, added mass coefficients, radiation damping coefficients, and exciting forces (moments) of the composite bucket foundation under different drafts and different wave directions. Finally, we clarified the basic hydrodynamic characteristics of the composite bucket foundation in the frequency domain and adopted multiple random wave models to investigate the effects of different wave heights, periods, and spectral peak factors on the towing motion characteristics of composite bucket foundation.

In this paper, the early drying shrinkage coefficients of different hydraulic cement mortars are calibrated through laboratory experiments for moderate-heat Portland cement (MHPC) and low-heat Portland cement (LHPC). By developing an improved mesoscale modeling approach, a 3D highly detailed simulation of concrete was generated, which incorporates the phases of mortar, aggregates, and interfacial transition zone (ITZ). The simulation result is in good agreement with the concrete early drying shrinkage experiment, exhibiting an error of less than 4.99% after 28 days. Subsequently, the mesoscale model is employed to explain the influence of the ambient humidity, cement type, and aggregate volume ratio on the early drying shrinkage performance of concrete. The results show that the early drying shrinkage coefficient of the LHPC is approximately 82% of the MHPC. Additionally, the depth of ambient humidity influence is about 15 mm from the concrete surface after 28 days. The early drying shrinkage can be controlled by increasing ambient humidity via the LHPC or raising the aggregate volume ratio. The mass-loss rate of concrete decreases as the ambient humidity or aggregate volume ratio increases during the process of drying shrinkage. Furthermore, the results quantify the influence patterns of various factors on drying shrinkage, thereby facilitating their application in assessing the cracking time induced by early drying shrinkage in roller-compacted concrete (RCC) dams. This provides theoretical guidance for crack prevention in concrete structures and aids in developing strategies for the construction of crack-free dams.

Unregulated underground group mining in China has led to problems such as unclear locations and complex shapes of mine goafs in mineral engineering, posing serious safety hazards for subsequent mining operations. This paper takes mineral engineering with complex mine goafs as the research object, integrates multi-survey data from surface deformation remote sensing monitoring and 3D laser scanning measurement to survey the area where the surface deformation rate reaches 14cm/ year, accurately identifies the location of risky mine goafs, and constructs detailed representations of the real shapes of the complex mine goafs inside the mineral engineering. The FLAC^3D 6.0 software is used to establish a 3D numerical simulation model of the mine goafs, fully considering the mining process, and conducting characteristic analysis of the stress distribution, failure range and surface deformation response of the mine goafs, revealing the impact of void deformation on the stability of the mine. The numerical simulation results are combined with on-site investigations to verify whether geological disasters have been caused by mine goafs. The research methods and results can provide effective technical means for the detailed survey and stability assessment of mineral engineering with complex mine goafs, which can help to reduce the risk of geological disasters in mines and improve the safety of mineral engineering.

Temperature control and crack prevention are crucial for mass concrete structures in cold regions. Electrically conductive roller-compacted concrete (ERCC) provides a promising route to shift surface temperature regulation from passive protection to active control. To develop an ERCC material suitable for engineering applications, this study first established a quantitative relationship between interparticle interaction energy and particle spacing to elucidate the effect of carbon black (CB) dispersion and agglomeration on concrete performance. The dispersion quality of CB was then evaluated by sedimentation tests, UV absorbance, and resistivity measurements. The absorbance of CB suspensions containing PCE, SDS, and TA increased by 79.9%, 80.1%, and 100.4%, respectively, compared with the suspension without dispersant, and TA gave the lowest mortar resistivity. Mechanical tests and mesoscopic simulations showed that coarse aggregate volume fraction and CB dosage had stronger effects on the compressive strength and elastic modulus of ERCC than aggregate gradation and specimen size. After calibration using the ERCC-2-TA mixture, the average errors between simulation and experiment were 0.7% for compressive strength and 0.4% for elastic modulus. For engineering applications, the recommended ERCC parameters were a coarse aggregate volume fraction of 40%, a CB content of 4–5% and a water-to-binder ratio of 0.45–0.50 for roads, and a CB content of 8% with a water-to-binder ratio of 0.55 for dams.

The transformation of abandoned open-pit mines into pumped-storage power station reservoirs offers an effective way to optimize China’s energy structure and supports China’s dual-carbon objectives by providing large-scale flexible storage. However, the steep slopes and complex geological conditions formed by mine excavation pose severe challenges to the stability of reservoir slopes. This paper focuses on a pumped-storage power station project converted from an abandoned mine pit in Luanping, Hebei Province. Specifically addressing high and steep slopes containing weak faults, it proposes a stability analysis method for the excavation stage that considers the influence of faults. The analysis assumes dry conditions, excluding reservoir-induced pore water pressure and seepage forces. Adopting the Janbu method and the M-P method within the limit equilibrium framework, safety analyses were conducted on multiple typical analysis sections of the abandoned mine pit before and after excavation. Analytical results indicate that the minimum safety factors derived from the Janbu method pre- and post-excavation are 1.33 and 2.13, respectively, whereas those obtained via the M-P method are 1.40 and 2.47. Given its consistently lower and thus more rigorous estimations, the Janbu method is recommended for conservative engineering design and risk assessment in similar geological settings. It is found that when the fault outcrop daylighting on the slope face constitutes a substantial spatial proportion, the potential sliding surface of the slope will extend from the top of the weak fault along an arc to the bottom of the stepped excavation. This indicates that the position of the fault influences both the sliding mode and the safety performance of the slope. The research findings of this paper could provide technical support for the slope engineering design, excavation and construction of pumped-storage power station reservoirs converted from abandoned mine pits.