Grout Diffusion Research Articles

Diffusion law and diffusion model for backfill grouting in loess shield tunnel at different soil moisture

Loess is a special type of soil whose properties are significantly affected by water. However, the grout diffusion law for backfill grouting in loess shield tunnels remains unknown. Based on a visual model experimental device, three experiments were conducted with 10%, 20%, and 30% loess moisture. A finite discrete element method was used to verify the grout diffusion mode, and parameters such as the tunnel buried depth, grout viscosity, and elastic modulus were considered to analyse the grout diffusion law. Experiments and numerical simulations show that the screening diffusion of grout occurs at low loess moisture, whereas splitting diffusion occurs at high loess moisture. The farthest splitting diffusion distance decreases as the tunnel buried depth, grout viscosity, and elastic modulus increase. In addition, based on capillary theory and geotechnical strength criteria, screening diffusion and splitting diffusion models were established. This study investigated the grout diffusion law and grout diffusion model, providing a reference for the design and construction of loess shield tunnels.

The grouting plugging mechanism of layered jointed rock mass considering the time-varying yield stress of grout

Slurry retention in fractures decreases after grouting is completed and the pressure supply is stopped, which affects the grouting sealing effect and prevents or restrains the occurrence of such adverse conditions. Based on the time-varying yield stress of grout, a theoretical analysis model of grouting diffusion decay is established, the decay height variation function and the minimum pressure stabilisation time calculation formula are derived, and the sealing mechanism of a jointed rock mass with multiple joints is studied. Moreover, a 3D visualisation laboratory test device for grouting diffusion decay of a jointed rock mass with layers was developed to analyse the diffusion and decay process of grout with different water-cement (W/C) ratios visually, and the correctness of the theoretical model was verified. The results show that: (1) the W/C ratio of grout should not be greater than 2, otherwise it is difficult for grout to remain in the cracks; (2) a large fissure opening easily spreads grout but is not conducive to the retention of grout; and (3) the time of stable pressure determines the retention rate of the slurry in the crack. When the horizontal crack opening width is 3 mm and the W/C ratio of the slurry is 1, the minimum stable pressure time to achieve a better sealing effect is 810 s. The research results can be used to reasonably plan the grouting time and improve the grouting efficiency to ensure the grouting effect, which is crucial for improving the theoretical system of grouting technology.

Diffusion Mechanism of Variable-Rate Grouting in Water Prevention and Control of Coal Mine

Regional grouting treatment is an effective technical means to prevent mine water disasters, and the grouting effect is affected by many factors. In actual grouting engineering, the single constant-rate grouting method is often transformed into a variable-parameter grouting process. However, research on grouting rates has been insufficient. This investigation focused on the issue of “the diffusion law of variable-rate grouting slurry in regional governance”. Methods such as theoretical analysis, numerical simulation, and field verification were used to evaluate the diffusion mechanism of variable-rate fracture grouting. The results indicated that the key parameters of variable-rate grouting, such as slurry diffusion distance and grouting pressure, were affected by the grouting rate. The decrease in the grouting rate reduced the migration speed of the slurry and the grouting pressure. The time for constant-velocity grouting and variable-velocity grouting to reach the same diffusion distance was 60 s and 108 s, respectively, which can be achieved with lower grouting pressure. When the grouting rate was 7.5 L/min and 30 L/min, the maximum grout diffusion distance was 2.81 m and 5.64 m, respectively, which required greater grouting pressure. The slurry diffusion rate decreased with the reduction in the grouting rate. Under the same diffusion distance conditions, variable-rate grouting took longer than constant high-rate grouting. In variable-rate grouting, the grouting pressure decreased stepwise with the grouting rate, with a final pressure drop of 77.4%. In grouting practice, the innovative use of the rate-reducing grouting method can greatly reduce the final grouting pressure under the premise of changing the slurry diffusion distance less, which can not only ensure the stability of surrounding rock but also reduce the cost of high-pressure grouting and the risk of grouting operation. The investigation results can provide scientific guidance for ground grouting renovation projects in deep coal mine water hazard areas.

Experimental and simulation study of magnesium phosphate cement two-liquid grouting materials

Magnesium phosphate cement (MPC) has a promising application in grouting. This study drew on the traditional cement-waterglass two-liquid grouting model. Creatively, the two main reaction components of MPC, dead-burned magnesium oxide and phosphate, were applied to the grouting field in a two-component liquid form. At the same time, through proportioning adjustment and experimental testing, we obtained A\B liquid components, which can be stabilized. In addition, MPC slurry was compared with the traditional grouting material, silicate cement slurry, to demonstrate its superiority. Finally, we simulated the grout diffusion process of the mixed slurry using the two-phase Darcy's law module of COMSOL Multiphysics subsurface fluids. The results show that the mixed slurry with a magnesium phosphate ratio of 1/3, a magnesium–boron ratio between 5% and 10%, and a water–cement ratio of 0.2–0.5 has better stability and mobility. Under the same fluidity, its strength is much higher than that of common silicate cement slurry and has good injectability. MPC was subjected to two-fluid grouting to take advantage of its fast-hardening and early-strengthening properties, while also improving its stability and fluidity. This study provided a theoretical foundation for the application of MPC.

Characterization of load-bearing and failure properties of fractured rock masses reinforced by negative pressure grouting

Grouting injection is a vital technique for addressing the challenges of high stress and significant deformation in the surrounding rock during deep mining operations, playing a crucial role in promoting green and low-carbon extraction methodologies. In this study, grouting reinforcement processes were examined by conducting grouting experiments on a fractured rock with varying negative pressures (0-100 kPa), followed by uniaxial compression testing of the grout-reinforced bodies. This investigation explored the diffusion patterns of grout under negative pressure and established a constitutive model of damage-bearing capacity for bodies reinforced by negative pressure grouting. It further studied the enhancement effect of negative pressure on the load-bearing capacity of the reinforced bodies and analyzed the instability mechanism of damage and failure in these bodies. The results indicated that the diffusion of grout under negative pressure is influenced by four types of forces, which alter the extent of grout diffusion within the fractured rock mass. Introducing a damage constitutive model that serially connects pore and framework elements characterizes the damage and failure behavior of grout-reinforced bodies under different negative pressures. As the negative pressure increases, changes in porosity, water-to-cement ratio, and admixture quantity occur in the grout-reinforced specimens, with the strength mean curve showing a trend of first increasing and then decreasing, reaching a threshold at a negative pressure of 60 kPa. With increasing negative pressure, the negative pressure damage variable decreases and then increases, and the stronger the interfacial microelement connections caused by the negative pressure, the greater the bearing capacity, ultimately manifesting in different failure modes.

Research on new magnetic epoxy resin composite slurry materials and localization grouting diffusion mechanism

A significant number of steep cracks are frequently encountered in underground engineering, posing a threat to operation. The high-pressure grouting method is a commonly utilized repair technique. Nevertheless, conventional grout is prone to displacement due to its weight, making it challenging to ensure adequate filling of the cracks. Therefore, this study aims to develop a grouting material with targeted displacement and anchoring properties. Firstly, an optimal magnetic slurry composition was determined through an orthogonal test. Subsequently, XRD and SEM were used to analyze the impact of the magnetic field on the composition distribution, internal pore structure, and transient viscosity of the slurry. Afterwards, a model for localized grout diffusion under magnetic was established. The results show that the application of a magnetic field caused the slurry to compact due to magnetic forces, reducing its porosity. Moreover, the dynamic viscosity of the slurry increased exponentially with rising magnetic induction intensity. Notably, a 40.5% increase in the diffusion area was observed when the magnetic field intensity rose from 2500 to 4500 GS. The error between the measured and theoretical values of the magnetic slurry diffusion model was only 8.91%, indicating the model's accuracy in describing the slurry diffusion process under magnetic field influence.

Diffusion mechanism of quick-setting slurry in water-rich fractured rock mass based on circle-outburst diffusion model

Grouting is the most commonly used methods in dealing with water inrush issue in mine and tunnel engineering. In order to better predict the grouting effect, research on slurry diffusion mechanism became a hotspot for scholars. At present, the mainstream theoretical model used to study the slurry diffusion mechanism are the circle diffusion model and the modified ones in plane plate fracture. However, these models cannot explain the “contradiction” between the rapid setting characteristics of quick-setting slurry and the continuous long-term injection of slurry in grouting engineering, which cannot accurately predict the grouting pressure or grouting diffusion range. Therefore, a “circle-outburst diffusion model” which can explain the above “contradiction” was proposed in this paper. Based on the new model, stepwise algorithms were developed to predict the grouting pressure and slurry diffusion range. By means of conducting fracture grouting simulation test and collecting grouting pressure data in an actual grouting project, the new model was verified and the slurry diffusion mechanism was studied. Comparison results indicate that the new model can reveal the intrinsic reason for the irregular diffusion phenomenon of the slurry and forecast the outburst moment accurately. The circle diffusion stage and outburst diffusion stage elaborated in the new “circle-outburst diffusion model” were consistent with the staged characteristics of the grouting process presented in the grouting simulating test. Differences between theoretical and experimental pressure value were within 10 %, indicating a high degree of consistency. The number and distribution of outburst diffusion points determine slurry diffusion form and significantly influence the diffusion range. The grouting pressure and the length of slurry flow path increase nonlinearly with time in each diffusion stage. It is hoped that the new model can provide a theoretical basis for the study of diffusion mechanism of quick-setting slurry.

Diffusion mechanism of fracture grouting in rock mass with flowing water

Grouting is a widely used geotechnical procedure known for its strong empirical properties. It has been extensively utilized for sealing subterranean water and strengthening soil and rock masses in their original locations in underground mining and underground space development. The diffusion mechanism of grouting in fractured rock is affected by the geological environment and slurry performance, which should be better revealed and characterized. In this paper, we take the surrounding rock of the roadway as the research object, consider the stress condition of the injected rock and time-dependent viscosity of the slurry, and establish fracture grouting diffusion model based on the rock composite fracture criterion. The grout strengthening mechanism is discussed based on a transparent fracture replica grouting test. According to the different transport characteristics of the slurry interacting with flowing water, it is divided into the following four areas grout-water balance area, grout loss area, stagnation area and water passage. The grout plugging mode is divided into two categories according to its final diffusion pattern: cross-section type water plugging mode and water-drop plugging mode. The pressure monitoring data of the test verified the two grout plugging modes. The diffusion distance of cis-reverse water derived in this study was in good agreement with the experimental results in grouting early stage. The research results can provide a theoretical basis for grouting engineering design.

Solid waste slurry grouting transformation mechanism of loose sand layer based on slurry-water replacement effect

During coal mining, when loose water-bearing sand layers are exposed and connected, it is extremely easy to cause water and sand inrush accidents, threatening the lives and properties in mines. Because of the intricate and tortuous internal structure of the sand layer, the diffusion pattern of grouting slurry within the loose sand layer has not been accurately characterized. Improving the efficiency of grouting and reducing the cost of grouting are common difficulties faced by industrial and mining enterprises in the grouting renovation of loose water-bearing sand layers. This paper innovatively proposes the mechanism of slurry-water displacement effect based on the diffusion characteristics of grouting slurry within the water-bearing sand layer. It studies the power-law fluid seepage and diffusion mechanism of porous media tortuosity effect and slurry-water displacement effect and derives the spherical diffusion equation of power-law fluid seepage grouting considering the coupling of porous media tortuosity effect and slurry-water displacement effect. At the same time, an indoor experimental device considering the slurry-water displacement effect is designed to verify the rationality of the spherical seepage grouting diffusion equation considering the superimposed effects of the two. Furthermore, relying on the COMSOL Multiphysics platform, a three-dimensional numerical calculation model of the power-law fluid spherical seepage grouting mechanism considering the porous media tortuosity effect and slurry-water displacement effect is constructed. It analyzes the seepage and diffusion characteristics of power-law grouting slurry in water-bearing sand layers, and studies the influence of different porosity of loose water-bearing sand layers, spacing between slurry and water holes, grouting pressure, and slurry viscosity on the volume of loose water-bearing sand layers. The key factors affecting the volume of loose water-bearing sand layers are grouting pressure > spacing between slurry and water holes > porosity of sand layer > slurry viscosity. Compared with previous grouting technologies and processes, the slurry-water displacement grouting technology can solve the problems of small grouting diffusion range and poor grouting effect in high-pressure underwater water-bearing sand layers to a certain extent.

Experimental study on visualization of seepage flow and grout diffusion and seepage reduction patterns in rough single fissure

Experimental study on visualization of seepage flow and grout diffusion and seepage reduction patterns in rough single fissure

Grout Diffusion Mechanism along the Pile Shaft during the Process of Pile Tip Post-Grouting in Sand

Grout Diffusion Mechanism along the Pile Shaft during the Process of Pile Tip Post-Grouting in Sand

Penetration grouting diffusion and strengthening mechanism of sand layer with crucial grout

Ordinary Portland Cement (OPC), micro-fine Portland cement (MPC), micro-fine sulfur-alumina cement (MSAC) and effective micro-fine cementitious grout (EMCG) were adopted. A visual simulation test device for fixed pressure permeation grouting for sandy soil was designed, and osmotic spreading and strengthening tests were conducted. The time-dependent variation rules of spreading distance and slurry amount were analyzed, and the influence of grout type, sand gradation, and grouting pressure on the reinforcement result were studied. The strengthening mechanism of EMCG at different spreading distances was analyzed emphatically, the microscopic strengthening modes of grout-rock interface with different grouts were obtained, and the essential reinforcement differences of various grouts were revealed. Based on the Kozeny-Carman model, the generalized percolation coefficient was deduced. The results showed that grout types and particle mass fraction were key factors to determine injectability of fine sand, the effect of grouting pressure was not significant, and the injectability of EMCG was the most satisfied. At the water-binder ratio (W/B) of 1.0, the 3 d strength of EMCG reached 13.3 MPa, and it was 1.25, 1.37 and 2.46 times as those of OPC, MPC and MSAC, respectively. The 7 d strength of EMCG exceeded 70 % of its 28 d strength, the diffusion distance of EMCG exceeded 2 m for S2 sand (0.3–0.6 mm), and its 28 d strength of reinforced sand reached 2.18 MPa as the W/B of EMCG was 2.5. The dense C–S–H gels generated at the EMCG slurry-rock interface can effectively improve cementation strength of sand and grout.

Experimental Study on the Relationship between Time-Varying Uplift Displacement and Grout Diffusion in Sand

Experimental Study on the Relationship between Time-Varying Uplift Displacement and Grout Diffusion in Sand

Experimental Study on Grout–Soil Interaction Effects in Sandy Soil under Different Water-to-Cement Ratios

Due to the unique characteristics of sandy soil layers, there is often a coupling effect of multiple grout diffusion patterns in the grouting process, and different slurry diffusion modes may lead to different responses of soil structures. In this study, laboratory grouting model tests were conducted with homogeneous sand under different water-to-cement (w/c) ratios to reveal the temporal variations in grouting pressure, soil stress fields, and displacement fields during the grout diffusion process. The results show that, during the grouting process in the fine sand layer, the grout mainly exhibited a compaction–splitting diffusion mode. The farther away from the grouting center, the more pronounced the hysteresis effect of soil pressure caused by grout diffusion. Meanwhile, as the w/c ratio increased, the diffusion mode between the slurry and the soil was in a transitional state. At w/c > 1.2, the primary pattern changed from the fracture–compaction pattern to the permeation–fracture–compaction pattern and fracture–permeation pattern. And the overall trend of the grouting pressure curve was similar under all of the w/c ratio conditions, showing a trend of increasing to the maximum value of the pressure first and then decreasing. With the increase in the water–cement ratio, the overall value of the grouting pressure curve showed a decreasing trend, the pressure value increased more slowly with time before reaching the maximum value, and the more obvious the influence of water–cement ratio was when w/c > 1.2. Additionally, the surface displacement also exhibited an overall decreasing trend, and it had no obvious lifting value under the condition of w/c = 1.6.

An environmental-benign method to enhance hydrate production in clayey silty reservoir via splitting grouting

During the pivotal period of energy transition between carbon neutrality and carbon peaking, it is crucial to develop the natural gas hydrate (NGH) due to the advantages of high energy density and non-pollution. However, the NGH production also faces several significant environmental challenges that need to be addressed such as seawater intrusion, methane leakage, and submarine landslides. Therefore, an environmental-benign method to enhance hydrate production in clayey silty reservoir via splitting grouting was introduced. As a novel method for achieving the two goals of both reservoir skeleton reinforcement and permeability enhancement, is proposed to stimulate NGH reservoir. Herein, the formulation based on foamed ultrafine cement-based grout was established. The results showed that the grout has good fluidity with initial viscosity ∼500 mPa·s and consolidation time in the range of 28–50 min. Meanwhile, the consolidation performance evaluation was studied, and it showed that the consolidation is with porosity in the range of 9.41%–46.59%, permeability in the range of 51.23 mD-789.07 mD, and compressive strength in the range of 3.31 MPa–3.88 MPa. The internal pore channels are uniformly distributed with a large number of stomatal strings, which can be used as a multistage seepage channel for gas and water production from hydrate decomposition. To further examine the stimulating behavior, the effect of hydrate saturation, grouting well diameter, grouting flow rate, and in-situ stress on splitting pressure and grouting volume were analyzed, and it was found that the grout has good ability to split fracturing and grout diffusion under the conditions of axial pressure of 5 MPa, confining pressure of 4 MPa, and hydrate saturation not more than 0.30. In addition, an environmental-benign high-efficient reservoir stimulation method on a laboratory scale was proposed. The findings could provide fundamental insights and recommendations for the implementation of splitting grouting in NGH reservoirs.

Numerical analysis and experimental study on slurry diffusion characteristics of vortical oscillatory grouting technology considering soil interface

Based on the fluidic jet theory, this study proposes an effective vortical oscillatory grouting technology. The fluid switching mechanism and pressure pulse characteristics are investigated through numerical simulation and experiment. The slurry diffusion performance of oscillatory grouting is compared with that of steady-pressure grouting under various soil parameters and slurry parameters. The effects of soil interface on diffusion behavior are also studied. The results show that the growth and dissipation of the vortex within the tool generate periodic oscillatory fluid, which further produces pressure pulses. During oscillatory grouting, the pressure recovery process inside the fluidic oscillator reduces the pressure of the soil. With the increase in porosity and particle size, the pressure of the soil grouted by oscillatory pressure is noticeably reduced. Despite the lower pressure of the soil, oscillatory grouting demonstrates better diffusion performance, owing to the dynamic flow field and pressure fluctuation. The performance of oscillatory grouting is also influenced by the oscillatory frequency and pressure pulse amplitude. When the soil interfaces are taken into consideration, different fluid domains exhibit complex slurry diffusion patterns. It is observed that the interface that is perpendicular to the grouting direction has a greater influence on grouting behavior. The oscillatory grouting diffusion behavior is more sensitive to the soil interface. This study is expected to improve grouting efficiency and promote the development of new grouting technology.

Development of Grouting Test System for Rough Fissure Rock Body and Research on Slurry Diffusion Law

The surface roughness of grout in fractured rock masses has a significant impact on the diffusion characteristics of grout, especially in millimeter-scale fractures. In this study, a self-constructed experimental system for grouting in rough fractured rock masses was used to conduct grout diffusion tests with varying fracture roughness, fracture aperture, and grouting pressure. A theoretical model was developed to account for the combined effects of fracture roughness, aperture, and grouting pressure on grout diffusion, and its validity was verified. The results showed that the theoretical calculations and experimental results had an error rate of around 12%, indicating the high reliability of the theory. Fracture aperture, grouting pressure, and fracture roughness all exhibited nonlinear relationships with the grout pressure distribution. With increasing diffusion distance, the grout pressure decreased, and the rate of decrease gradually slowed down. Fracture roughness and aperture had a relatively small impact on grout pressure, while grouting pressure had a significant influence on grout pressure distribution. The difference in grout pressure between the initial and final stages of diffusion was small, whereas in the middle stage of diffusion, the difference was more pronounced. This research provides a valuable reference for the selection of grouting techniques in the roadway surrounding rock projects.

Diffusion mechanism of cement-based slurry in frozen and thawed fractured rock mass in alpine region

The problem of slope stability after freeze-thaw damage in cold regions has become increasingly prominent. To explore the grouting diffusion mechanisms of different grouting materials in frozen and thawed rock masses, a true triaxial stress-state frozen and thawed rock mass fracture grouting experiment was conducted. Computed tomography (CT) and scanning electron microscopy (SEM) were performed on the grouted specimens to obtain the grouting diffusion patterns and three-dimensional reconstruction of the grout veins in different frozen and thawed rock masses under fracture grouting. The results show that Portland cement slurry with low viscosity has better diffusion performance in unfrozen rock mass and rock mass after 10 freeze-thaw cycles. In the case of cement slurry containing graphene oxide and microsilica powder additives, the reinforced area exceeded that of ordinary cement after 10 freeze-thaw cycles, with the reinforced area reaching its maximum after 25 cycles. The “slurry-rock” interface primarily forms three modes: contact, embedding, and covering. Graphene oxide and microsilica effectively fill the larger pores in the cement particles, with microsilica being particularly effective in promoting cement hydration and reducing microdefects in the transition zone between the slurry and rock interfaces.

Research on slurry diffusion and seepage law in mining overburden fractures based on CFD numerical method

It is of great theoretical significance and engineering application value to research the diffusion law of slurry in mining fractures of rock strata to enrich grouting theory and improve grouting sealing effect. In this paper, the law of grout diffusion in fractures under different working conditions is systematically explored and analyzed, and a numerical simulation scheme of grout diffusion in a single slab crack is established. Then, the diffusion law of grouting slurry in crack under different rheological index and different consistency index is further investigated. The results show that the diffusion time of grouting slurry has no relation with the rheological index. The grout pressure at the same point increases with the increase of rheological index. When the rheological index increases by 0.1, the grout pressure increases by about 12.5%. The closer the grouting mouth is, the more the grouting pressure is affected by the rheological index. There is little relationship between the diffusion time of grouting slurry and consistency index. The grout pressure at each measurement point increases with the increase of the consistency index. When the consistency index increases by 1, the grout pressure increases by about 15% on the basis of the origin. The closer the grouting mouth is, the more the grouting pressure is affected by the consistency index. In engineering practice, when grouting slurry with large rheological index or consistency index exists, it is necessary to moderately increase the grouting pressure value.

Study on the deformation failure mechanism and coupling support technology of soft rock roadways in strong wind oxidation zones

Due to the influence of sedimentary environment, the coal seams and overlying rocks in the wind oxidation zone exhibit developed fractures, high rock porosity, strength attenuation, and poor self-stability. It leads to the large deformation of the surrounding rock and managing the roof of roadways difficultly. This made the roadway excavation extremely difficult. And the rendering conventional “bolt-cable-mesh (belt)-shotcrete” combined support system was not applicable. In this paper, the No. 49,104 air return roadway in the strong wind oxidation zone of the Shuiquan Coal Mine was selected as the engineering background. The change trends of the coal and rock in the strong wind oxidation zone physical and mechanical properties were revealed, and the deformation and failure mechanism was analyzed. According to the deformation and failure characteristics of the roadway in the wind oxidation surrounding rock with engineering practice, a coupling support scheme “pregrouting + anchor net and sprayed concrete + inverted arch structure + U-shaped steel + high and low-pressure, deep and shallow-hole reinforcement grouting” was proposed. A roadway grouting reinforcement diffusion range model was established in COMSOL Multiphysics, and the grouting diffusion range was then imported into FLAC3D to compare and analyze the coupling support scheme reinforcement effect of roadway in the strong wind oxidation zone. And the coupling support scheme was used to reinforce the No. 49,104 air return roadway, and the reinforcement effect was monitored in situ. Results showed that the proposed coupling support and reinforcement scheme can be employed to effectively control the deformation of the surrounding rock and the expansion of plastic zone damage. And the stability and safety of the roadway were significantly improved. This coupling support scheme was reasonably designed, and it could provide an engineering reference for the support and reinforcement of roadways in weak and crushed surrounding rocks under similar geological conditions.