Polyurethane has been widely used as new chemical grouting material. Expansion characteristics caused by chemical reactions make polymer grout different from other types of grout. To throw light on the diffusion process of polymer grout in a fracture, a density model was derived by fitting the experimental data based on the polymerization mechanism of polyurethane. In addition, a numerical simulation of polymer diffusion in a single fracture was developed to predict the pressure distribution. An experiment was carried out to analyze the diffusion distance and pressure field under different grouting masses. Comparison of results from numerical calculation and experiments indicates that the numerical approach is able to predict polymer diffusion in the fracture. The numerical simulation is suitable for rapid determination of the grouting mass, diffusion shape, flow-front position, and pressure distribution, which could provide guidance on assessing polymer grouting parameters.

Polyurethane grouting can be used for antiseepage and reinforcement in underground construction. Understanding the diffusion characteristics of polyurethane grout is critical for good grouting design. However, the influence of water pressure on the diffusion of polyurethane grout is not clear. The aim of this work is to experimentally investigate the diffusion behavior of polyurethane grout in a water-bearing fracture. A series of laboratory experiments was conducted using a self-designed visual fracture grouting device under different conditions. The influences of grouting quantity and water pressure on grout diffusion distance and flow field are discussed. The results show that grout expansive diffusion and the pressure field change of the grout–water system have a phased characteristic. Also, the change of grout pressure is not synchronized with grout diffusion distance. The grout diffusion radius increases with the increase of grouting quantity, but decreases with the increase of hydrostatic pressure. The study helped gain insight into the performance of polyurethane grouting in fracture under static water condition.

Polyurethane grouting materials, a type of expansible grout, has played a significant role in the rehabilitation of public infrastructures, such as lifting the slab in a road and reinforcing the broken wall rocks in a tunnel. Due to the unique expansion characteristic of polyurethane materials induced by the chemical reaction, its diffusion mechanism in rock fracture is rather complicated. Based on a numerical method presented in a previous paper, the diffusion law of expansible grout in a single fracture is studied considering the time-varying density and viscosity of the grout tested by experiments. The grout diffusion radius, pressure distribution and velocity field are calculated by the numerical model combining the finite volume method (FVM) and volume-of-fluid (VOF) method. Taking the gel time into account, the characteristics of flow field distribution during the grout movement process are investigated on five different cases and the influences of grouting quantity and fracture aperture on grout diffusion behavior are analyzed, which can reveal some diffusion law of expansible grout in a single water-free fracture.

Polyurethane grouting material (polymer) has been widely used in rock mass fracture grouting. The previous test of polymer slurry grouting in planar fracture did not consider the influence of temperature; therefore, in this paper, a test of polymer slurry grouting in planar fracture was firstly conducted in order to explore the diffusion characteristics of polymer slurry. The results show that the preheating temperature of polymer slurry has a great influence on the diffusion of slurry in fractures, which should be considered in the research of polymer fracture grouting. In addition, the slurry temperature is related to the chemical reaction of the polymer itself. However, the existing polymer fracture grouting models ignore the influence of temperature and the chemical reaction of the polymer slurry itself, which lack the rationality to reveal the diffusion behavior of the polymer slurry in fracture. Therefore, in this paper, a chemical reaction-fluid dynamic (CF) model was established. In addition, the Particle Swarm Optimization (PSO) algorithm was used to obtain the chemical reaction kinetic parameters of the polymer slurry. Based on the CF model, the diffusion characteristics of the polymer slurry during the fracture diffusion process were calculated. The applicability of the CF model was verified by comparing the experimental data with the calculated results. Finally, the influence of polymer preheating temperature and ambient temperature on slurry fracture grouting behavior was explored by the CF model. The research in this article provides some theoretical reference for the design of grouting parameters in fracture grouting engineering.

The rapid detection of asphalt content in asphalt mixture is of great significance to the quality evaluation of asphalt pavement. Based on the dielectric properties of an asphalt mixture, the prediction model of asphalt content is deduced theoretically using three types of dielectric models: Lichtenecker‐Rother (L‐R) model, Rayleigh model, and Bottcher equation. Under the condition of laboratory mixing at room temperature (about 20–25°C), a dielectric test of asphalt mixture is conducted to verify the applicability of the model. The test results indicate that the dielectric constant of the asphalt mixture is inversely proportional to the asphalt content and directly proportional to the aggregate size of the mixture. Among the models, the Rayleigh model has a wide range of applications and exhibits a high accuracy, with an average relative error of only 1.86%. The results provide a theoretical basis for the nondestructive testing of asphalt pavements using ground‐penetrating radar.