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This study introduces a unified cylindrical and spherical cavity reverse expansion model to simulate the formation of compaction grouting bodies and grout diffusion along pile shafts. Stress field expression employs the superposition method, while displacement field analysis utilizes the nonassociated Mohr–Coulomb criterion. By combining the displacement expression for cylindrical cavity reverse expansion with the fluid flow equation, a calculation method is proposed to compute the upward and downward diffusion heights of grout, considering the unloading effect. The parameter analysis demonstrates that ultimate grouting pressure increases with increasing soil strength and grouting depth, with the ultimate grouting pressure at the pile tip being greater than that at the pile side. The value of grout diffusion height is negatively correlated with unloading ratio and grouting depth while positively correlated with grouting pressure and pile diameter. The deeper the grouting depth, the greater the impact of unloading on grout diffusion height. Three case studies validate the effectiveness of the proposed model. Analysis reveals that when grouting pressure exceeds the ultimate pressure, the size of the grout body is related to the grouting volume. Neglecting the unloading effect in the prediction of grout diffusion height for pile foundations would lead to conservative results. [ABSTRACT FROM AUTHOR]

Traditional model tests for soil and rock materials face challenges in observing the slurry diffusion within the soil mass, hindering the understanding of the relationship between grouting-induced ground deformation and grout diffusion. This study conducts grouting diffusion model tests using a self-developed experimental setup on both ordinary and transparent sand. We investigate cement slurry diffusion patterns, distribution characteristics, and temporal variations in ground uplift displacement during the grouting process. By leveraging a visualization grouting model and non-intrusive displacement measurements, we directly observe and verify the changes in cement slurry diffusion and ground displacement in transparent sand. The results indicate the following: during non-steady grouting in sand, slurry diffusion progresses from low-pressure infiltration to medium-pressure compaction, culminating in high-pressure fracturing; ground uplift displacement curves exhibit a consistent "step-like" increase with grouting time, featuring accelerated growth after each step; and visualization tests reveal a strong correlation between grouting pressure, slurry diffusion, and corresponding uplift displacement. Distinct features in the grouting pressure plot align with the acceleration phases of the displacement; at a water–cement ratio (w/c) of 0.8, the stratum's vertical deformation shows a symmetric "higher in the middle, lower on the sides" distribution. As the burial depth decreases, the stratum's uplift displacement tends to flatten horizontally, especially at w/c = 0.8 and 1.2. [ABSTRACT FROM AUTHOR]

Pile tip post-grouting technology has been widely adopted in pile foundations to improve its bearing characteristics. Grouting in the pile tip leads to the grouting cement spreading along the pile body to a certain extent. To better understand the grout diffusion mechanism along the pile body returned, a total of 45 groups of laboratory model tests were carried out on sand, with different grouting pressures, grout volumes, and soil stress histories taken into account. By comparing the characteristics of the grouted bulbs, the grout diffusion mechanism along the pile body returned was revealed. Combined with the test results, a simplified model to describe the grout diffusion pattern and the corresponding grouting mode of grouting cement along the pile body returned during the process of pile tip post-grouting was proposed. This model can comprehensively reflect the grout diffusion characteristics along the pile body, with different grouting conditions and soil stress histories taken into account.

Due to the invisibility and complexity of underground engineering rock masses, it is extremely difficult to observe the diffusion process of dynamic water grouting. Therefore, studying the diffusion mechanism of grouting in underground fractured rock masses with flowing water is crucial in preventing water inrush and improving the rock mass tightness. In this study, a novel dynamic water grouting test system based on low-field nuclear magnetic resonance (LF-NMR) was developed to investigate the dynamic grouting diffusion process in fractured sandstone with flowing water. Then, the NMR characteristics of superfine cement-sodium silicate slurry and free water were compared, and the influences of water flow velocity, grout flow velocity and fracture apertures on the grouting diffusion characteristics of fractured sandstone with flowing water were systematically investigated. The test results show that the increase in the grout flow velocity and fracture aperture can effectively improve the dynamic water grouting efficiency, while the increase in the water flow velocity will reduce the dynamic water grouting efficiency. When the grout flow velocity is lower than the water flow velocity, the dynamic water grouting test cannot be successfully performed. Additionally, the slurry filling ratio of the pores peaks when the flow velocities of grout and water are identical. The findings in this paper can provide meaningful reference and guidance for grouting parameter selection in grouting engineering practice. Highlights: A novel dynamic water grouting test system which can monitor the variations of slurry and water in pores and fractures of real rock is developed. The grout diffusion process in the rock pores and fractures under flowing water condition shows an obvious three stages evolution. The influences of dynamic water grouting parameters such as grout flow velocity, water flow velocity and fracture aperture on grouting efficiency are investigated. [ABSTRACT FROM AUTHOR]

Grouting reinforcement is an effective method for controlling the stability of engineering rock mass. The mechanism is mainly to inject or infiltrate the grout into the fracture of rock mass to form a grouting entity, and strengthen the stability of rock mass and the ability to resist failures. In order to realize the calculation of the whole process of grouting diffusion and consolidation in broken surrounding rock, a diffusion-consolidation mechanism of grouting based on discrete element method was proposed. Also, the model checking and example analysis were carried out, and the results show that: ① In the full-length grouting of single fracture scenario, the shear peak strength of the post-fractured rock mass is higher than that of the non-grouting fracture, which depends on the frictional resistance generated by the solidification and cohesion of the slurry. ② In the point grouting simulation experiment, as the grouting pressure increases, the grout continues to diffuse. Therefore, the pre-peak shear yielding and post-peak phases of the rock mass are strengthened. ③ For the engineering-scale simulation test, as the grouting pressure increases, the diffusion radius increases in two stages. When the grout expands to the high-stress area, it needs to overcome a greater compressive stress to achieve flow. After reaching a relative higher grouting pressure, the diffusion area of adjacent boreholes is superimposed to form a grouting whole body that surrounds the roadway. When the solidification bond strength of the grout is low, the failure of contact is still the main controlling factor to determine the failure and instability of the roadway.

Traditional model tests for soil and rock materials face challenges in observing the slurry diffusion within the soil mass, hindering the understanding of the relationship between grouting-induced ground deformation and grout diffusion. This study conducts grouting diffusion model tests using a self-developed experimental setup on both ordinary and transparent sand. We investigate cement slurry diffusion patterns, distribution characteristics, and temporal variations in ground uplift displacement during the grouting process. By leveraging a visualization grouting model and non-intrusive displacement measurements, we directly observe and verify the changes in cement slurry diffusion and ground displacement in transparent sand. The results indicate the following: during non-steady grouting in sand, slurry diffusion progresses from low-pressure infiltration to medium-pressure compaction, culminating in high-pressure fracturing; ground uplift displacement curves exhibit a consistent “step-like” increase with grouting time, featuring accelerated growth after each step; and visualization tests reveal a strong correlation between grouting pressure, slurry diffusion, and corresponding uplift displacement. Distinct features in the grouting pressure plot align with the acceleration phases of the displacement; at a water–cement ratio (w/c) of 0.8, the stratum’s vertical deformation shows a symmetric “higher in the middle, lower on the sides” distribution. As the burial depth decreases, the stratum’s uplift displacement tends to flatten horizontally, especially at w/c = 0.8 and 1.2.

Polyurethane foam materials have broad application prospects in practical engineering as flame retardants, waterproof coatings, and grout repair materials due to advantages such as light weight, quick forming, and good durability. Due to water's low cost and convenience, water-reactive Polyurethane foam materials are widely used in engineering. The content of the water has a significant effect on the performance of polyurethane foams after molding. Polyurethane foams with anti-seepage and reinforcement effects are used in complex water environments for long durations. This study analyzed the effects of water content on properties and the diffusion mechanism of polyurethane foam materials in water. Additionally, the effect of the water environment on the polyurethane grouting material's properties was summarized. Finally, this study discussed the future research directions of polyurethane foam materials in a water environment. [ABSTRACT FROM AUTHOR]

To explore the bolt-grouting method of the deep roadway under three-dimensional unequal ground stress, a unidirectional coupling model of surrounding rock plastic failure and grouting diffusion considering the influence of excavation disturbance stress was established. Spatial evolution characteristics of plastic failure and grouting diffusion, and the impact of the spacing and row spacing of grouting bolts/cables on grout diffusion, were simulated by using the numerical method. The results revealed that the horizontal ground stress perpendicular to the axial direction of the roadway was the main factor inducing roadway damage. Moreover, the more significant the difference of the ground stress in three directions, the larger the plastic zone of the roof corner and floor corner of the roadway. Under different lateral pressure coefficients, the grout diffused can be approximate ellipsoid and cylinders. Furthermore, the larger the ratio of lateral pressure coefficients perpendicular to and parallel to the axial direction of roadway, the larger the diffusion length of grout in each spatial direction in the surrounding rock. In bolt-grouting support, the length of the grouting bolts/cables should be greater than the plastic zone of the surrounding rock, and the optimal relationship between their spacing and row spacing and diffusion length of grout is determined. The research results were applied in the bolt-grouting engineering for the three-level main roadway in the Haizi Coal Mine, and a good support effect was achieved. This can provide technical guidance and a method of reference for the design and parameter optimization of bolt-grouting support for roadways under deep high ground stress. [ABSTRACT FROM AUTHOR]

This paper proposed an improved stepwise algorithm to simulate the grout diffusion in a single fracture considering the dynamic grouting parameter boundary condition and the spatial- and time-dependent viscosity of the grout. The method was more effective and could result in variation in key output parameters at any measurement point/time (in space and time). Based on the algorithm, three types of dynamic pressure boundary conditions, which are more applicable in grouting engineering practice, were designed to illustrate the grouting process. Compared with constant pressure grouting, the dynamic adjustments of pressure grouting were found to be beneficial to grout propagation in most cases. Some other factors were also studied under dynamic pressure boundary conditions, such as the spatiotemporal variation in the slurry viscosity and fracture aperture, which demonstrate a significant influence on the grout migration. Finally, a dynamic pressure grouting system was prepared, and the accuracy of the algorithm was successfully validated using a series of laboratory tests. [ABSTRACT FROM AUTHOR]

With the rapid development of deep underground engineering, grouting technology is widely used to enhance the stability of the surrounding rocks in tunnels, where ingress water, large site disturbance, and deformation are the main challenges. In this paper, a three-dimensional (3D) numerical grouting system, which is based on TOUGH2 and the finite element method (FEM), is developed to study the diffusion and consolidation of grout slurry during the cyclic grouting process. It is observed that the grouting technology can reduce the rock permeability and porosity, increase the degree of compactness, and improve the strength of the rock mass. This numerical grouting system is validated by three numerical tests. The grout diffusion and consolidation process are investigated by simulating grouting experiments. Finally, a detailed mining tunnel grouting schedule is designed, and the corresponding numerical model is established to mimic stopping the water ingress. The results show that the grouting system presented in this study is potentially useful to improve the grout characteristics and tunnel designs, as well as construction. [ABSTRACT FROM AUTHOR]

• Preparation of solid waste grouting material with high solid waste admixture. • Analysis of the performance of grouting materials for solid waste applications. • Establishing a three-dimensional numerical model for grouting fractured rocks. • The swirling diffusion pattern of the slurry in the fractured rock mass. China's commitment to achieving carbon neutrality by 2060 has highlighted the pressing need for effective solid waste recycling. The reinforcement of mine water hazards has led to increased production costs due to the significant consumption of slurry. This study focuses on the development of mine crack grouting sealing and reinforcement materials using mine slag powder and waste rubber particles, along with cement reinforcement and alkali slag stimulation. The impact of water-cement ratio, rubber particle content, and slag mass fraction on slurry performance is analyzed, and the optimal values for these parameters are determined. A two-phase seepage simulation using COMSOL is conducted to investigate the flow and diffusion of slurry in a fractured network rock mass. The findings indicate that a water-cement ratio of 0.7 and a slag and rubber particle mass fraction of 70% and 30% respectively result in the slurry with favorable fluidity and mechanical properties. The diffusion pattern of the slurry in the fractured rock mass is characterized by vortex-like diffusion. The stability of the fractured rock mass is influenced by both grouting time and pressure, which should be carefully considered during on-site operations. This research has significant implications for the integrated prevention and control of mine water hazards and the large-scale utilization of high-dosage solid waste, thereby ensuring production safety, ecological environment safety, and sustainable development in mining areas. [ABSTRACT FROM AUTHOR]

Investigations of the flow and diffusion mechanism of grout slurry in underground fractured rock mass are of critical significance to guarantee the grouting reinforcement of deep soft rock tunnel and to ensure the construction safety. This paper reports a series of permeation grouting tests in fractured sandstone samples based on the low-field nuclear magnetic resonance (LF-NMR) technique. During the grouting process, the NMR signal characteristics of the grout were monitored in real-time, and the parameters such as the slurry injection volume, effective grouting time and grout filling speed were comprehensively analyzed under various temperatures, confining pressures, flow velocities and numbers of fractures. The results show that the final injection amount of the grout decreases with increasing temperature and confining pressure. The effective grouting time is inversely proportional to the flow velocity, while it is positively related to the temperature. The filling speed decreases with increasing the temperature and confining pressure, while it increases with increasing the grout flow velocity. Compared to the single fractured sample, the sample with more fractures is injected with more grout slurry in a shorter effective grouting time and a higher filling speed. Under the conditions of high confining pressure (e.g., 15 MPa) or high flow velocity (e.g., ≥5 ml/min), the grout slurry preferentially transports into the micropores, and then the mesopores and macropores. However, the temperature and number of fractures have equal effects on the grout flow and diffusion in the three types of pores. The grouting filling performance becomes worse when the temperature and confining pressure are higher. The findings in this study provide meaningful guidance for the grouting reinforcement of deep soft rock tunnel. [ABSTRACT FROM AUTHOR]

This study presents a non-linear spring model for modelling the backfill grout consolidation behind shield tunnel lining. Two important parameters, i.e. the time-dependent grout pressure decay induced by consolidation and the grout-cake thickness, were derived through a non-linear spring model and continuity equation. The proposed non-linear spring model for backfill grout consolidation was validated based on vertical pressure and strain relationships determined from an oedometer test. The derived equations were applied to the Groene Hart Tunnel (GHT) project. The results show that the calculated grout pressures agree well with the measured values. The calculated grout-cake thicknesses are in good agreement with the measured values. Two key factors influencing the grout consolidation are discussed: grout diffusion into the soil, and the initial distribution of the grout injection pressure. It is found that grout diffusion into the soil can dissipate the grout pressure quicker than grout consolidation. The distribution of the initial grout injection pressure dominates the final distributions of the grout pressure/grout cake around the tunnel lining. [ABSTRACT FROM AUTHOR]