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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. [ABSTRACT FROM AUTHOR]

Slurry diffusion is the key factor affecting the resistance reduction of pipe jacking grouting. Therefore, this paper establishes a three-dimensional numerical analysis model of pipe jacking, introduces a diffusion ring to simulate the slurry diffusion process during pipe jacking construction, modifies the friction coefficient according to the contact between the soil around the pipe and the segment, and studies the influence of the slurry diffusion process on the resistance reduction effect during pipe jacking construction. The calculated jacking friction is compared with the measured data to verify the reliability of the method proposed. The influence of the filtering effect on soil displacement and the influence of grouting diffusion-related parameters on soil displacement and jacking friction during pipe jacking construction are further studied. The results show that the surface subsidence is smaller when the filtration effect is considered; The stronger the attenuation of permeability coefficient caused by the filtration effect, the smaller the surface settlement and jacking friction resistance; The faster the slurry diffuses and the more complete the slurry jacket is, the better the resistance reduction effect of grouting during pipe jacking.

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]

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Shanghai Jiao Tong University (1006-2467) is the property of Journal of Shanghai Jiao Tong University Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The deep mining process of North China type coalfields is highly threatened by the threat of water damage from the floor limestone aquifer. By arranging grouting holes reasonably to inject a large amount of slurry into the aquifer that directly threatens the safety of coal seam mining, making the strong aquifer a weak aquifer or an impermeable layer is the main means to solve such water damage problems. In microfracture grouting engineering, the slurry-rock mass coupling effect has a significant impact on the diffusion process of slurry. To this end, the interaction between slurry and rock mass and the diffusion mechanism of slurry during high-pressure grouting of coal seam floor aquifers was studied, a single fracture grouting diffusion theoretical model was established that considers the slurry flow-rock mass deformation coupling effect, based on the viscosity time varying Bingham slurry diffusion equation and fracture aperture control equation. The spatial distribution characteristics of slurry pressure and fracture aperture in the slurry diffusion direction were analyzed, and the effect rules of slurry-rock mass coupling effect on slurry diffusion was revealed, and the results were compared with the grouting model with constant fracture aperture. The results showed that the attenuation trend of slurry pressure and fracture aperture in the slurry diffusion direction was consistent, and both had obvious nonlinear characteristics, and the attenuation was faster in the fracture entrance area. The degree of slurry-rock mass coupling effect decreased with the increase of fracture aperture, and the design value of grouting pressure will be too high if fracture aperture was small and the slurry-rock mass coupling effect was not considered. The grouting pressure became the main controlling factor affecting the slurry diffusion distance gradually as the fracture aperture increased. By comparing the theoretical results with an example of grouting transformation of the limestone aquifer in the lower coal seam floor of Luxi coal mine, the validity of the theoretical model was verified.

In view of the loose, broken and serious deformation of the surrounding rock of the connection roadway in the south of 730 mining area of Xinhe Mining Company, the influence of different grouting parameters on the slurry diffusion was discussed by using Comsol Multiphysics finite element analysis software; on this basis, the influence of different grouting anchor cable arrangement on grouting effect is studied. The results show that the slurry diffusion radius will gradually increase with the increase of grouting pressure and grouting time. The average growth rate of slurry diffusion radius is 30.95% for each increase of 1 MPa grouting pressure and 25.67% for each increase of 1 min grouting time; the layout of the grouting anchor cable determines the scope of the grouting reinforcement circle. When the “hexagon” layout is adopted, the scope of the grouting reinforcement circle is relatively large, and there will be no slurry leakage on both sides of the roof. Based on the numerical simulation results, it is determined that the grouting pressure of the bolt-grouting support of the connection roadway in the south of Xinhe Mining Company is 4 MPa, the grouting time is 8 min, and the grouting anchor cable arrangement scheme is “hexagon” type. The engineering application shows that the optimized grouting parameters effectively control the deformation and damage of the surrounding rock of the roadway, and obtain good engineering results, and also provide an effective basis for the grouting reinforcement of such roadway.

In order to liberate the shallow quaternary loose aquifer coal pillar resources, taking the 1010-1 working face of the first mining area of Wugou Coal Mine as the test object, the grouting reinforcement test of quaternary loose aquifer and the weathering zone of the bedrock at the bottom was carried out by using the splitting grouting method and the grouting technology combining continuous and intermittent grouting. The results show that: the quaternary loose aquifer control area has complex lithology and weak water content, and mainly receives runoff recharge from the lateral area. The grouting reconstruction project adopts the water displacement and sand fixation scheme of the ground straight hole combined with the directional oblique hole row by row; the strength of the mixed slurry is subject to the ratio of fly ash, and the strength and stone rate of the mixed slurry are higher than those of the cement net slurry. When the fly ash content is 20%, the stone rate is the highest; the diffusion of grout in the quaternary loose aquifer is very uneven, the grouting process needs to control the grout diffusion range by controlling the grouting amount, the influence of grouting on the surface is reflected in the grout diffusion and pressure conduction, and the pressure conduction is the main one; after injection, the true density and water content of the core hole samples slightly increased, while the compressive strength, tensile strength and shear strength slightly increased; with the increase of sampling depth, the compressive strength of the rock layer in the wind-oxidized zone of bedrock increased first, then decreased and then increased, and the compressive strength increased about 2-5 times.

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. [ABSTRACT FROM AUTHOR]

Directional regional grouting to transform aquifers is one of the effective ways to prevent and control mine water hazards. In order to study the diffusion law of grouting slurry in directional areas, a three-dimensional simulation test system for directional area grouting has been independently developed. The system is mainly composed of test bench, grouting system, water injection system, data monitoring and other subsystems, which can realize directional drilling grouting simulation, three-dimensional slurry diffusion simulation, high pressure water simulation and regional grouting simulation. The system can independently control the grouting hole unit to achieve porous and multi sequence grouting. With the help of six grouting holes, the slurry flow process is simulated under various parameters such as different grouting pressure, slurry viscosity, grouting rate, and water cement ratio. It can also achieve real-time monitoring of the slurry diffusion process in dynamic/static (high) water pressure environments. The paper takes the simulated naked hole lengths of 200 mm, 250 mm, and 300 mm as the research objects, and preliminarily explores the characteristics and effects of slurry diffusion in naked hole grouting under directional grouting. The study found that: in the case where only the naked hole length is a variable, the slurry diffusion range does not synchronously increase linearly with the linear increase of naked hole length; The slurry stone body of the short open hole is cylindrical with the drilling open hole as the axis, while the slurry stone body of the long open hole is circular with the drilling open hole as the axis; Increasing the same length of the bare hole results in a larger difference in the diffusion range of the slurry at both ends of the bare hole. At the same time, the more pressure loss there is, the smaller the diffusion distance of the slurry. Comparing the diffusion radius of the slurry obtained from the experiment with that calculated by the Maag formula, the difference between the two values is only 2.8% when the length of the grouting open hole is 200 mm. The experimental results comply with the Maag spherical diffusion theory and verified the scientificity and rationality of this experimental system.

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.

Copyright of Journal of Mine Automation is the property of Industry & Mine Automation Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

After the water inrush accident in coal mine tunnels, early-stage pouring of aggregate forms a high-resistance, low-permeability aggregate stacking, transforming the pipeline flow into percolation. In the later stage, grouting is carried out into the interior of the aggregate stacking, effectively accumulating and solidifying the cement slurry. Among these, whether the slurry can migrate over long distances and fill the voids inside the aggregate stacking is the critical determinant of the success or failure of sealing. To quantitatively analyze the migration distance of slurry inside the aggregate stacking after grouting, a single-hole grouting test platform was established, and an orthogonal experiment was designed with grouting pressure, water cement ratio, and aggregate stacking porosity as influencing factors. Based on 25 sets of experimental measurements, four neural network prediction models suitable for studying the slurry migration distance within the aggregate stacking were constructed separately as back propagation neural network (BPNN), genetic algorithm (GA) combined BPNN, particle swarm optimization (PSO) combined BPNN, and GA-PSO combined BPNN. Evaluation criteria such as Mean Absolute Error (MAE), Mean Absolute Percentage Error (MAPE), Mean Square Error (MSE), Root Mean Square Error (RMSE), and the coefficient of determination (R2) were used for comparative analysis of the calculation errors and prediction accuracy of each model. From the perspective of neural network prediction results, the weight value of each influencing factor was analyzed, and the ranking was as follows: grouting pressure > aggregate particle size > water cement ratio, with grouting pressure being the primary controlling factor. The study demonstrates that the GA-PSO-BP model exhibits the best prediction performance, with an average relative error of only 1.59% and an R² of 0.998. This neural network model overcomes issues such as slow learning and getting stuck in tricky spots in BP neural networks. The prediction model shows high accuracy and stability, enabling more effective and accurate prediction of slurry migration distances, making it worthy of dissemination and application. This study can improve safety measures by reducing waste, expediting disaster management efforts, and minimizing environmental hazards associated with mining incidents.

The main technical means for preventing and controlling karst water damage in the coal seam floor of North China type coal fields are grouting transformation of the water-bearing rock layer. Currently, the main method for testing the grouting effect is to analyze the lithological features before and after grouting. There is a lack of tracking and dynamic monitoring of the entire grouting process, making it difficult to accurately evaluate the grouting effect. In order to solve the above problems, an inter hole resistivity monitoring system is introduced to monitor the entire process of resistivity changes in grouting transformed rock layers, in order to achieve precise detection of the slurry diffusion range. Firstly, an improved electrode and cable device is used to place the resistivity monitoring system in a long directional borehole on the coal seam floor, achieving resistivity monitoring between boreholes. Secondly, a geological model of slurry diffusion is constructed, and the simulated data is processed and interpreted using three-dimensional resistivity inversion. Finally, engineering tests are conducted on the inter hole resistivity monitoring of the entire grouting process at the injection layer underground in the coal mine. The simulation results indicate that inter hole resistivity monitoring can identify the diffusion range of slurry anomalies. Based on the trend of resistivity changes over time, the diffusion range of slurry can be inferred. As the slurry gradually diffuses, the range of anomalous areas gradually increases and the intensity of anomalies gradually increases. The engineering test results show that the resistivity monitoring system is arranged on the grouting layer through drilling for dynamic monitoring. After three-dimensional inversion imaging of the monitoring data, the features of resistivity changes in the grouting layer caused by slurry diffusion can be successfully captured. It provides a feasible technical solution for detecting the grouting effect in coal mines.

A large number of shield tunnel construction practices have shown that the assembled tunnel segments just detached from the tail of the shield machine are prone to various defects such as ring displacement, crack propagation, and local damage. The reason for these defects is that the tunnel segments tend to float locally or as a whole during the construction process between the connecting rings. To investigate the reasons for the floating of tunnel segments during the construction period, a combination of theoretical derivation, numerical simulation, and on-site monitoring were used to roughly divide the floating force into two parts: "static floating force" and "dynamic floating force" for different strata and stages. The study focused on the theoretical derivation and analysis of the dynamic floating force magnitude and distribution during the grouting process at different stages. With the support of numerical simulation and on-site monitoring of the tunnel segment floating condition in the shield tunnel section from Sanyuanqiao station to Taiping Temple station of Chengdu metro line 9, the correctness of the formula and distribution pattern of the dynamic floating force calculation were verified for the poorly permeable and weathered mudstone stratum. [ABSTRACT FROM AUTHOR]

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.

To solve the problem of gangue discharge in coal mining, fluidized gangue filling technology was developed. The key scientific problem of this technology is the diffusion characteristics of the gangue in the goaf. Therefore, a discrete element fluidized gangue model was established based on the ARR contact model. Based on the Rblock module, a goaf model with a certain void ratio was created, and the meso-parameters of fluidized gangue were calibrated. The fluidized gangue diffusion and rock displacement laws were explored under different grouting speeds, void ratios, and gangue particle sizes. The research results show that with the increase in the grouting speed and void ratio, and the decrease in the gangue particle size, the diffusion radius gradually increases, and the rock displacement in the goaf also gradually increases. Under given geological conditions, the total grouting mass of a single hole can reach 5.63 × 104 kg. [ABSTRACT FROM AUTHOR]