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The problem of seepage control is faced in the construction of large underground powerhouse cavern systems. To reduce leakage and improve the permeability stability of the surrounding rock, a complex seepage control system, including drainage hole arrays, drainage tunnels, and grouting curtains, was designed for the Wunonglong underground powerhouse caverns. In this study, we performed a seepage field numerical analysis of the Wunonglong underground powerhouse caverns system to optimize the seepage control system. A three-dimensional numerical model was established considering the complex seepage control system and the geological conditions. A steady seepage analysis method, with a variational inequality formulation, was adopted in order to calculate the long-term seepage field. A drainage substructure method was used to simulate the seepage behavior of the densely arranged drainage hole arrays. The seepage control effects of single and double grouting curtains were compared to determine a reasonable curtain layout scheme. The effect of the drainage system on the seepage control of the powerhouse caverns is further discussed. The findings offer reliable insights into the seepage behavior of underground powerhouse caverns and provide a reference for the design and construction of similar underground powerhouse cavern systems. [ABSTRACT FROM AUTHOR]

This study is intended to investigate the mechanical, durability, and drying shrinkage properties of concrete mixtures incorporating wastewater from ready-mixed concrete plants. The microstructural attributes were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) imaging, energy dispersive spectrometry (EDS), and mercury intrusion porosimetry (MIP). Meanwhile, rough set theory (RST) was used to analyze the influence of mean pore radius, porosity, fractal dimensions, and pore size distribution (PSD) on the compressive strength of wastewater concrete. The results showed that the seven-day cube compressive strengths for C20, C40, and C60 concrete specimens increased when wastewater was utilized, with the highest rise in the strength properties being observed as 16.84% for C40 mixture. Nevertheless, the 28-day cube compressive strengths of C20, C40, and C60 concretes were reduced by 4.85%, 9.33%, and 18.63%, respectively. The durability results showed that wastewater mixing reduced the frost resistance of C40 and C60 concrete, but improved for C20 concrete. The microstructural investigation revealed that mixing concrete with wastewater densifies the early-age concrete microstructure and refines the pore size. Nevertheless, the compactness of concrete microstructure at the later stage was reduced, and the pores in concrete were enlarged due to the poor cohesiveness of wastewater particles. The porosity and PSD have the greatest influence on the compressive strength of wastewater concrete. A strength and pore structure model of wastewater concrete was also developed and validated by considering PSD and porosity as bivariate parameters. The addition of wastewater can improve the early compressive strength of concrete. The addition of wastewater reduces the carbonization resistance of concrete. A high-precision model of wastewater concrete strength was established. [ABSTRACT FROM AUTHOR]

Reasonable control of grouting parameters was the key to improving the pile-soil interaction. However, quantitative analysis on the effect of grouting parameters on the pile-soil interaction was still lacking. This article developed an intelligent post-grouting system for precise control and quantitative analysis of grouting parameters. The conventional preparation method for shear tests were improved in this article. By changing the normal stress of the pile-soil interface during grouting, the test sample could simulate the grout distribution of the pile-soil interface at different depths. Through the improved experimental methods, a more accurate analysis of the mechanism for the pile-soil interaction was achieved. And the effectiveness of the intelligent post-grouting system was further verified by the case application. The results indicated that increasing the grout volume could improve the interface shear strength when the normal stress and grouting pressure were constant. This improvement effect caused by increasing grout volume decreased when the normal stress was high. Increasing the grouting pressure increased the interface shear strength when the normal stress and the grout volume remained constant. This improvement effect caused by increasing grouting pressure decreased when the grout volume was small. By appropriately controlling the two grouting parameters, the cohesion and the shear strength of the pile-soil interface were increased by 5.8-18.8 times and 1.16-2.91 times, respectively. The results indicated that the intelligent post-grouting system could accurately control the grouting parameters and effectively improve the pile-soil interaction of bored piles. The intelligent post-grouting system effectively reduced geotechnical engineering risks and improved the bearing capacity of pile. [ABSTRACT FROM AUTHOR]