Xiaochen Wang

The interaction between slurry and concrete cracks influences the grouting diffusion process during the grouting repair engineering of cracked concrete material. Compared to a single-cracked concrete material, the slurry–concrete crack interaction mechanism of a multi-cracked concrete material is more complicated. This study employs the Monte Carlo method to generate a crack group with a certain probability distribution for characterizing the random cracks in the concrete material. The cracked concrete material is simplified as a pore–crack medium model, and the continuity equation of the slurry in the model is derived. Furthermore, based on the modified interface layer theory, the coupling effect of the slurry–concrete crack is elucidated, and the variation law of each crack opening in the concrete material under different grouting pressures is examined. When the slurry diffuses in a multi-cracked concrete material, the crack opening changes mainly stem from the crack distribution position and crack tendency. Under the same grouting pressure, four main forms of changes occur in the crack opening: gradual increase along the crack distribution, slow decrease, first increasing and then decreasing, and, basically, unchanged. When the grouting pressure increases, crack groups with the same distribution form have similar crack opening change rules, but the change range varies. Under the same grouting pressure, as the number of cracks in the concrete material increases, the coupling effect of the concrete material becomes increasingly obvious.

Rock fracture surfaces are normally rough, with upper and lower surfaces presenting obvious structural properties (i.e., matching or mismatching). In this paper, rock fracture was divided into shear and tensile fractures based on its mechanical origin. A test simulation system for grouting in rough fracture (tensile and shear fractures) with continuous pressure field monitoring was proposed. A series of grouting simulation tests were employed to evaluate the effect of fracture structural property, fracture surface roughness, and aperture on the characteristics of grout flow in the rough fracture. The results show that grouting pressure exhibited a trend of rapid increase followed by a slow increase with time during the grouting in the tensile and shear fractures. Grouting pressure increases with time in a smooth relationship for tensile fracture and a fluctuating upward relationship for shear fracture. The slurry pressure distribution along the penetration length exhibited a nonlinear attenuation trend. The attenuation degree of the slurry pressure was positively related to the fracture roughness and the roughness difference in the upper–lower fracture surface and negative with the fracture aperture. The potential filtration effect during the grouting process is an important factor affecting the grouting behavior in the rough fracture.

In this paper, ordinary Portland cement, ultrafine cement, polyurethane, and epoxy resin were selected as typical grouting materials. Grouting simulation tests were first conducted to prepare the grouted concrete crack sample. The effect of concrete crack parameters (i.e., crack aperture and roughness), grout water–cement ratio, and grouting pressure on the water-plugging performance of different grouting materials was explored through the impermeability test. The microstructure of grouted concrete cracks was analyzed by means of scanning electron microscopy (SEM) and computed tomography (CT), and the difference in water-plugging performance of different grouting materials was explained at the micro level. The results show that the impermeability of the four grouting materials was ranked as follows: Epoxy resin > polyurethane > ultra-fine cement > ordinary Portland cement. The concrete cracks grouted by epoxy resin have the highest plugging failure water pressure and the lowest permeability, which is the optimal grouting material. The effectiveness of crack grouting in water-plugging was directly proportional to the grouting pressure, provided the pressure did not exceed a certain value. When the pressure surpassed the threshold, the increase in pressure did not have a significant impact on the water plugging performance. For the two cement-based materials, the threshold pressure was 1 MPa, while for the other two chemical grouts, it was 2 MPa. The two cement-based grouts with a water–cement ratio of 0.8 showed optimal water-plugging performance. The water-plugging performance of ordinary Portland cement paste, ultra-fine cement pastes, and polyurethane grout was negatively correlated with crack aperture and positively correlated with crack roughness. However, the water-plugging performance of epoxy resin grout was not affected by crack aperture or roughness.