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The post-construction improvement technology of bored pile tips has been widely used in the construction of gravel pebble layers, but the diffusion law of the grouting slurry remains to be revealed. To study the diffusion law of the grouting slurry at the tip of bored piles in gravel pebble layers, an equivalent relationship between the seepage continuity equation and the mass diffusion continuity equation was established based on an in-depth comparative analysis; further relying on the Diluted Species Transport Module in Porous Media of Comsol Multiphysics, a three-dimensional numerical model of slurry diffusion was established to systematically study the impact of key factors such as different porosities, grouting times, grouting pressures, slurry diffusion coefficients, and the ratio of vertical to horizontal slurry diffusion coefficients on the diffusion radius of the slurry. The calculation results show that with the continuation of grouting, the increase in porosity, grouting pressure, and slurry diffusion coefficient, or the decrease in the ratio of vertical to horizontal slurry diffusion coefficients, the diffusion range of the slurry increases accordingly. Furthermore, comparatively speaking, the impact of porosity is the smallest, while the impact of the slurry diffusion coefficient is the greatest. The research findings reflect the diffusion trend of the slurry in the gravel pebble layer, which has guiding significance for the quality control of the actual design and construction of grouting. [ABSTRACT FROM AUTHOR]

Grouting has been commonly used for structure controlling in mining engineering. To investigate the mechanism of fracturing grouting, an experiment was conducted under constant flowing conditions. Through the real-time gathering of main parameters and reconstruction of the slurry distribution, the complete grouting process and pressure spread of the high-pressure slurry were revealed. An identification method of fracturing diffusion based on acoustic emission (AE) signals was proposed and verified. The results indicated that the intact rock showed fracturing response with a mutated pressure in a short time. For fractured ones, the grouting process can be divided into five stages: seepage flow, pressure holding, fracturing diffusion, steady flow, and pressure relief. Influenced by the hydraulic fracture and slurry infiltration, there were three states: cement diffusion, water seepage, and the unaffected zone. A calculation method of whole stages for the grouting pressure was proposed based on the Hoek–Brown strength criterion and flow model in a fracture. In addition, AE ring counting occurred during the entire slurry process but was relatively concentrated in pressure holding and fracturing diffusion stages. Considering the zonal distribution characteristics, the AE method was used to characterize the slurry diffusion range and flow paths. The slurry distribution was obtained by the three-dimensional cutting and reconstruction method to verify its feasibility. This study is expected to further clarify the grouting mechanism, and guide engineering practices. Highlights: High-pressure grouting experiment of fractured rock based on acoustic emission was carried out. The whole process of fracturing grouting shows five responses in fractured rock. The pressure calculation model for revealed whole injection process was established in inclined fracture. AE monitoring can be used to identify the splitting-diffusion range and path for fracturing grouting. [ABSTRACT FROM AUTHOR]

The post-construction improvement technology of bored pile tips has been widely used in the construction of gravel pebble layers, but the diffusion law of the grouting slurry remains to be revealed. To study the diffusion law of the grouting slurry at the tip of bored piles in gravel pebble layers, an equivalent relationship between the seepage continuity equation and the mass diffusion continuity equation was established based on an in-depth comparative analysis; further relying on the Diluted Species Transport Module in Porous Media of Comsol Multiphysics, a three-dimensional numerical model of slurry diffusion was established to systematically study the impact of key factors such as different porosities, grouting times, grouting pressures, slurry diffusion coefficients, and the ratio of vertical to horizontal slurry diffusion coefficients on the diffusion radius of the slurry. The calculation results show that with the continuation of grouting, the increase in porosity, grouting pressure, and slurry diffusion coefficient, or the decrease in the ratio of vertical to horizontal slurry diffusion coefficients, the diffusion range of the slurry increases accordingly. Furthermore, comparatively speaking, the impact of porosity is the smallest, while the impact of the slurry diffusion coefficient is the greatest. The research findings reflect the diffusion trend of the slurry in the gravel pebble layer, which has guiding significance for the quality control of the actual design and construction of grouting.