Hydropower dams are subjected to soft water penetration during their service lives. Concrete deterioration due to calcium leaching will decrease the durability of concrete and affect dam safety. The long-term performance of concrete dams due to calcium leaching should be evaluated and predicted accurately to complete reinforcement work in a timely manner. In this paper, a methodology that combined microscopic tests and numerical analysis to evaluate the long-term performance of dam concrete due to calcium leaching is proposed. The current state of concrete is evaluated by analyzing the components of sediments and seepage water through microscopic and spectroscopic tests, such as X-ray photoelectron spectroscopy, scanning electron microscopy, and inductively coupled plasma mass spectrometry. The long-term degradation of concrete was predicted by utilizing a multi-scale model of calcium leaching, which considered the micro-pore structure of cement hydrates flux with time. The simulated results using this calcium leaching model showed a good agreement with other experiments. Finally, a real case study including field inspection was performed and the long-term durability of dam concrete was predicted through microscopic tests and finite element analysis method. It implies that the proposed method could provide calculation and theoretical basis for the durability analysis of concrete dams due to calcium leaching.

In this article, a novel three-dimensional (3D) discrete element method (DEM) algorithm is proposed for modeling real particle shapes. First, high-precision computed tomography (CT) is used to scan sand particles to obtain the 3D morphology of single-particle sand. Second, the background grid points and the 3D shape grid of the sand particles are generated along the x-axis. Finally, spherical particles are used to construct an overlapping model of real sand particles. The shapes of sand particles generated via this method are accurate, and their surface shape is close to that of real sand particles. The proposed method can also be used to generate structures of various sizes and shapes, thus simplifying the modeling process in DEM simulation. The numerical simulation results of free-falling sand particles show that the DEM model established by this method is effective in numerical simulation analysis.

As a new type of offshore wind foundation, the wide‐shallow bucket foundation with honeycomb bulkheads mainly bears vertical, horizontal, and moment loads. As yet, no systematic study has been conducted regarding the effects of honeycomb bulkheads on the undrained bearing capacities of the wide‐shallow bucket foundation. In this study, a large number of three‐dimensional (3D) finite element (FE) analyses were performed to investigate the undrained bearing capacities of the wide‐shallow bucket foundations with and without honeycomb bulkheads, thereby evaluating the influence of honeycomb bulkheads on the bearing capacities under different conditions. The results show that under uniaxial loading, the uniaxial bearing capacities of the wide‐shallow bucket foundation are basically unaffected by the honeycomb bulkheads in homogeneous clay. For nonhomogeneous clay, the moment bearing capacity will be considerably enhanced with the increase in soil shear strength heterogeneity. Under combined loading, the honeycomb bulkheads will enhance the combined bearing capacities only in nonhomogeneous clay. The enhancement effects will increase with the increase in soil shear strength heterogeneity but decrease with the increase in vertical load. Besides, the simplified equations for calculating the uniaxial bearing capacities of the wide‐shallow bucket foundation with honeycomb bulkheads are also proposed considering the influence of embedment ratio and soil shear strength heterogeneity. At last, the parameters of an approximating expression are fitted to predict the failure envelopes of this foundation under combined loading.

In Public–Private Partnership (PPP) projects, the structure of the Special Purpose Vehicle (SPV) significantly impacts the value enhancement of projects. This study conducted a quantitative analysis of value enhancement in green PPP projects under single- and Dual-Role entity models and examined existing SPV private party compositions. A quantitative model was developed to enhance the value in green PPP projects through a Dual-Role “investor–builder” entity approach, comparing it with the single-role entity model. The findings indicate that in the Dual-Role entity mode, the construction party demonstrates a greater willingness to effort, resulting in shorter construction timelines and improved economic benefits for the project company. The preferred equity range for private parties escalates with the total project investment and the extent of “political support”. Nevertheless, a disproportionately high government stake in the equity is detrimental to the value enhancement in PPPs, and excessive government regulation and control should be avoided. This quantitative model serves as a decision-making criterion for selecting the SPV mode and provides an alternative approach for evaluating PPP project performance.

The soil compaction effect of pile penetration increases earth pressure on the pile shaft. Analyzing earth pressure changes caused by pile penetration is significance for establishing a calculation method for pile penetration resistance. The large deformation numerical simulation method and the NHRI soil model were used to analyze the pile penetration process in sandy soil. The variation of earth pressure coefficient K under different working conditions was analyzed. Numerical analysis results indicate that the change in soil horizontal stress during the pile penetration process can be divided into three stages: loading, unloading and stress stabilization. The soil horizontal stress peaks when the pile end reaches a certain depth, and then the soil enters the unloading stage as penetration continues, and finally stabilizes. The maximum disturbance range is 5D in the depth direction and 6D in the radial direction. Earth pressure on the pile shaft after penetration is approximately linear, with extreme values at the pile end. The change in pile diameter has an insignificant effect on earth pressure, and the earth pressure on the pile shaft with different diameters is similar. As the interface friction coefficient increases, the earth pressure on the pile shaft gradually rises. Based on the numerical analysis results, a method for calculating pile shaft earth pressure considering the pile-soil interface friction coefficient is proposed.

This study addresses the early-age brittleness and performance limitations of sustainable cement soil. While prior works optimized the baseline compressive strength using recycled sand and nanoclay, the multi-scale synergistic effects of fibers and nanomaterials on the post-peak deformation remain underexplored. To address this gap, a composite modification system incorporating recycled sand, nanoclay, polypropylene fibers, and graphene derivatives was developed. The experimental program comprised standard specimen fabrication, early-age curing, and unconfined compressive strength (UCS) testing, supplemented by RBF neural network curve fitting and quantitative ArcGIS digital image processing of scanning electron microscopy (SEM) micrographs. The results demonstrate that optimizing the fiber parameters (0.6% content with 6 mm length) successfully increases the early UCS to 2263.2 kPa, which is further elevated to a peak of 2755.0 kPa upon co-incorporation with 0.05% small-sized graphene oxide. Correspondingly, a newly introduced ductility index quantitatively confirms that the single-fiber reinforcement yields an index of 1.93, which is further enhanced to 2.02 by the graphene composite system. Microstructure tracking and digital image extraction revealed that the SEM-derived surface porosity decreased significantly, exhibiting a clear inverse relationship with the macroscopic mechanical strength. These quantitative microstructural shifts confirm that graphene effectively filled micropores and reinforced the fiber–matrix interface, establishing a dense matrix network with enhanced interfacial bonding. This multi-scale approach offers a sustainable strategy for green geotechnical applications.