Grouting Effect Research Articles

Mechanical Properties of Iron Tailing Sand Grout Sleeve Joints and Force Analysis.

In this paper, the mechanical properties and internal stress condition of the reinforcing bar sleeve connectors with ferro-tailed mineral sand cementitious grout as filler material were analyzed as research objects. Firstly, an experimental study was carried out on the reinforcing bar sleeve connectors of iron tailing sand grout with a 40% substitution rate of mechanism sand to analyze the mechanical properties of different grout types, age, and reinforcement diameters under unidirectional tensile, high stress, and large deformation of repeated tensile and compressive stresses. Next, five groups of sleeve joints with different anchorage lengths were set up for unidirectional tensile tests. The results show that, with the decrease of the diameter of the reinforcement, the grip force and bond strength of the iron tailing sand grout on the internal reinforcement gradually increase. Under conditions of large deformation and high stress due to repeated tensile loading, the residual deformation and total elongation of iron tailing sand grout sleeve joints are satisfactory. Additionally, the restraining anchorage effect of iron tailing sand grout in the end section is small. The utilization rate and integrity of iron tailing sand grout in the initial anchorage section are better.

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 study on the effect of mixing parameters on the rheological behaviour and micro-flocculation structure of ultrafine Portland cement slurry

The penetration diffusion of ultrafine Portland cement (UPC) slurry is closely related to its rheological behaviour and micro-flocculation structure. To date, there has been a need for more research investigating the impact of mixing parameters on the macro-micro hydrodynamic behaviour of UPC slurries. In this study, a series of macroscopic rheomechanical characterisation tests and microscopic in-situ tests of the flocculation structure of UPC slurries under various mixing parameters were conducted systematically by using a rotational rheometer and a focused beam reflectance measurement (FBRM) system. The effects of mixing speeds and times on the macroscopic shear stress-shear rate curves, rheological patterns, rheomechanical parameters, and the distribution of micro-flocculated particles of UPC slurries were investigated. The results indicate that the macroscopic rheomechanical parameters and microscopic flocculation coefficient of UPC slurry exhibit a decrease with increased slurry mixing speed. However, a “decrease and then increase” trend is observed with increased slurry mixing time. The smaller the powder size of cement and the lower the water-cement ratio of the slurry, the more sensitive the rheomechanical properties of the slurry are to the influence of the mixing parameters. A positive correlation exists between the macroscopic rheomechanical properties of UPC slurry and its microscopic flocculation coefficient. Increasing the slurry mixing speed or prolonging the early mixing time can destroy the microscopic flocculation particles of UPC slurry, a reduction in the flocculation coefficient of the slurry, and an improvement in the macroscopic fluidity properties. The research findings provide a foundation for improving the effectiveness of UPC grouting in the engineering field.

Influence of Freezing Tunnel Excavation on Foundation Settlement of Buildings

In this paper, the effects of the cement content and excavation speed parameters on the improvement effect of the artificial freezing method and the characteristics of frozen walls are studied by means of a field test, numerical simulation and theoretical model. The optimization effect of the cement content in the artificial freezing method is studied. It is found that 10% is the best content, which can maximize the freezing wall thickness and grouting effect, and promote uniform distribution of the temperature field. At the same time, the influence of the excavation speed on the stress and settlement of the foundation soil is analyzed. It is pointed out that the increase of the excavation speed will aggravate the settlement and stress redistribution, which may threaten the building structure. The evaluation method proposed in this paper verifies that the construction deformation and settlement control are within the safety standards and provides theoretical support and construction guidance for tunnel engineering.

A porous IPN-structured polyurethane/epoxy grouting material with low viscosity, high strength and low volume shrinkage

Epoxy based grouting materials should concern with low viscosity, high strength, rapid curing, and low shrinkage. A polyurethane/epoxy grouting material was prepared. Through formula design, its initial viscosity was reduced to below 200 mPa·s. The morphology observation confirmed its porous and IPN structure. Compared with pure EP, its tensile strength, compressive strength, and impact strength were increased by 87 %, 20 %, and 50 %, respectively, as well as the volume shrinkage was significantly reduced. The inherent strength of PU/epoxy resin grouting materials was significantly higher than that of concrete, even in humid environments, their bond strength was 3.26 MPa. The theoretical grout flow rate and diffusion radius at different stages of the grouting process were also determined, which achieved an excellent on-site grouting effect.

Impact Strength Properties and Failure Mode Classification of Concrete U-Shaped Specimen Retrofitted with Polyurethane Grout Using Machine Learning Algorithms

The inherent brittle behavior of cementitious composite is considered one of its weaknesses in structural applications. This study evaluated the impact strength and failure modes of composite U-shaped normal concrete (NC) specimens strengthened with polyurethane grout material (NC-PUG) subjected to repeated drop-weight impact loads (USDWIT). The experimental dataset was used to train and test three machine learning (ML) algorithms, namely decision tree (DT), Naïve Ba yes (NB), and K-nearest neighbors (KNN), to predict the three failure modes exhibited by U-shaped specimens during testing. The uncertainty of the failure modes under different uncertainty degrees was analyzed using Monte Carlo simulation (MCS). The results indicate that the retrofitting effect of polyurethane grout significantly improved the impact strength of concrete. During testing, U-shaped specimens demonstrated three major failure patterns, which included mid-section crack (MC), crushing foot (CF), and bend section crack (BC). The prediction models predicted the three types of failure modes with an accuracy greater than 95%. Moreover, the KNN model predicted the failure modes with 3.1% higher accuracy than the DT and NB models, and the accuracy, precision, and recall of the KNN model have converged within 300 runs of Monte Carlo simulation under different uncertainties.

Experimental study on effect of grouting and high temperature on the anisotropic compressive strength behaviour of soft jointed rocks with an impersistent flaw

This study investigates the effect of different in situ conditions like flaw infill, heat-treatment temperatures, and sample porosities on the anisotropic compressive response of jointed samples with an impersistent flaw. Jointed samples of different porosities are prepared by mixing Plaster of Paris (POP) with different water contents, i.e. 60% (i.e. for lower porosity) and 80% (i.e. for higher porosity). These samples are grouted with different infill materials, i.e. un-grouted, cement and sand-cement (3:1)-bio-concrete (SCB) mix and subsequently subjected to different temperatures, i.e. 100 °C, 200 °C and 300 °C. The results reveal the distinct stages in the stress-strain responses of samples characterized by initial micro-cracks closure, elastic transition, and non-linear response till peak followed by a post-peak behaviour. The un-grouted samples exhibit their lowest strength at 30° joint orientation. The ratios of maximum to minimum strength are 3.11 and 3.22 with varying joint orientations for lower and higher porosity samples, respectively. Strengths of cement and SCB mix grouted samples are increased for all joint orientations ranging between 16.13%-69.83% and 18.04%–73% at low porosity and 22%–48.66% and 27.77%–51.57% at high porosity, respectively as compared to the un-grouted samples. However, the strength of the grouted samples is decreased by 66.94%–75.47% and 77.17%–81.05% at lower porosity, and 79.37%–82.86% and 81.29%–95.55% at higher porosity for cement and for SCB grouts with an increase in the heating temperature from 30 °C to 300 °C, respectively. These observations could be due to the suppression of favourable crack initiation locations, i.e. flaw tips along the samples due to the filling of the crack by grouting and generation of thermal cracks with temperature. The mechanism of strength behaviour is elucidated in detail based on fracture propagation analysis and the anisotropic response of with or, without grouted samples.

Experimental and Numerical Study on the Treatment Effect of Horizontal Lateral Grouting on the Deformation of Shield Tunnels in Clay

Experimental and Numerical Study on the Treatment Effect of Horizontal Lateral Grouting on the Deformation of Shield Tunnels in Clay

Waste-based panels with cement grout as an infill material for composite railway sleepers

The development of high performance and eco-friendly composite railway sleepers at a reasonable price is a great challenge for composite railway sleeper manufacturers. The study proposed a railway sleeper concept based on high-performance fibre composites and low-cost waste-based materials to overcome this challenge. In this concept, thin hollow composite tubes are filled with high volume waste-based panels, which are bonded together with cement grout. This study examined the effect of cement grout, grout thickness, panel types, and surface preparation of the panels on the bond behaviour between the panels and cement grout. It also investigated the bending behaviour of manufactured railway sleepers by evaluating the effects of filling hollow tubes, the orientation of the infill panels, and the types of infill materials. Results indicate that the proposed concept has a high potential for development of high performance and eco-friendly composite railway sleepers at a competitive price due to the incorporation of high volume of waste materials. The results of the study will serve as a guide to the manufacture and design of composite railway sleepers.

Cement slurry penetration behavior of swirl grouting technology

Traditional pressure grouting technology operates under steady pressure conditions, causing the grout to easily flow along preferential pathways. This results in uneven grout penetration and increased economic costs. This study proposes swirl grouting technology, which effectively improves this problem. To verify the effectiveness of swirl grouting, a fan-shaped blade tool was also proposed. The grout penetration performance was investigated through experimental studies. The length, width, height, weight, and uniformity of the grouted bodies produced by the swirl grouting method were compared with those produced by the steady pressure grouting method. Then, the mechanisms of swirl grouting were analyzed through transparent disc visualization experiments. The results demonstrated that, at different water–cement ratios, the swirl device increased the penetration length in the X, Y, and Z directions by 43.3%, 27.8%, and 45.8%, respectively, compared to the conventional straight device, and by 57.3%, 39.4%, and 55.6%, respectively, compared to the fan blade device. Moreover, the swirl device increased the weight of the grouted stone body by 54.9% compared to the conventional straight device and by 91.0% compared to the fan blade device, significantly enhancing filling efficiency. The uniformity coefficient of the swirl device permeation decreased by 56.6% and 51.0%, respectively, compared to the conventional straight device and the fan blade device, resulting in a more uniform grout distribution. The transparent disc visualization experiment further revealed the advantage of the swirl device in promoting the migration of fine particles, with a significant increase in average penetration distance and a penetration shape closer to a regular circle. The rotating flow path of the swirl device imparts additional rotational momentum and multidirectional penetration capabilities. The resulting turbulence accelerates the mixing of grout with the soil matrix, facilitating the migration of fine particles, expanding flow channels, and reducing flow resistance. This combination of effects enhances penetration efficiency and reduces energy loss. This study offers significant practical application value for improving engineering quality, construction efficiency, and reducing costs.

Experimental Research on Microbial Grouting Effect on Strength of Granite Residual Soil in Guangdong

Experimental Research on Microbial Grouting Effect on Strength of Granite Residual Soil in Guangdong

Effects of superplasticizer on properties of calcined ginger nuts-based grouting material for earthen site cracks

Grout injection is an effective technique for repairing cracks in earthen sites. This study aims to address the challenges of Calcined Ginger Nuts (CGN)-based grout and enhance its engineering performance by investigating the compatibility of different superplasticizers. We examined the effects of Polycarboxylate Superplasticizer (PCE) and Naphthalene Superplasticizer (PNS) on the properties of CGN-based grout, focusing on fluidity, rheological properties, mechanical strength, volume stability, color difference, and pore structure. The engineering applicability of the optimized CGN-based grout with superplasticizers was assessed using COMSOL Multiphysics. The results show that fluidity increased with higher dosages of PCE and PNS. The grout containing these superplasticizers behaved as a shear-thinning fluid, following the power law model. Specifically, the consistency coefficient of grout with 0.5 wt% PCE and PNS decreased by 39.73% and 64.83%, respectively. Additionally, 2.9 wt% PCE and PNS reduced volume shrinkage rate by 6.86% and 6.27%, respectively. Initially, increasing the dosage of PCE and PNS improved compressive and flexural strength, but these properties later declined. XRD analysis revealed that PNS above 1.1 wt% and PCE weakened the hydration reaction, while both superplasticizers promoted carbonation. Mercury Intrusion Porosimetry (MIP) showed that 1.1 wt% PCE and PNS reduced the proportion of capillary pores by 13.79% and 10.11%, respectively. Based on these findings, 0.5 wt% PNS demonstrated the best compatibility with CGN-based grout, whereas PCE showed poor compatibility. Numerical simulations using COMSOL Multiphysics confirmed that 0.5 wt% PNS provided superior grouting effectiveness. Therefore, the CGN based grout with 0.5wt% PNS demonstrates excellent engineering performance and applicability. This study offers valuable insights into optimizing CGN-based grout for the preservation of earthen sites.

An approach based on P-wave velocity for grouting effectiveness evaluation in earthen sites

Grouting technology is the primary method for repairing cracks in earthen sites. However, there has been a long-standing lack of effective methods for evaluating grouting effectiveness. This paper proposes a field evaluation method based on P-wave velocity. This method explicitly discusses two scenarios where the P-wave velocity of the grout is either higher or lower than that of the soil, using the depth ℎ of the “hypothetical crack” as the evaluation indicator. The experimental results indicate that specimens with 20% and 40% defects show increases in ℎ values of 0.0113 m and 0.0166 m, respectively. Laboratory tests have demonstrated that this method can accurately evaluate grouting effectiveness and is not affected by the P-wave velocity of the soil. The application of this evaluation method to three typical earthen sites resulted in more reliable and easily quantifiable evaluation outcomes. By considering the width of grout, the method provides a more intuitive comparison of reparation effectiveness. The study demonstrates the feasibility of the proposed method, thereby facilitating effective crack reparation in earthen sites.

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.

Evaluating densification effect of ideal compaction grouting in unsaturated soils by volumetric water content

Compaction grouting is primarily applied based on empiricism, and it is challenging to quantify its densification effect. To address this issue, five sets of laboratory model tests on ideal compaction grouting were conducted, with varying pressures from 400 kPa to 800 kPa, to quantitatively evaluate the densification effect in unsaturated soils. The response of surrounding soil during compaction grouting was monitored. The changes in dry density and void ratio induced by compaction grouting were obtained by monitoring volumetric water content to determine compaction efficiency. In addition, a model was developed and validated to predict the effective compaction range. The results show that soil dry density increased rapidly during compaction grouting before being stabilized at a consistent level. As expected, it is positively correlated with grouting pressures (GPs) and negatively correlated with the distance from the injection point. At higher GPs, the difference in densification effect around the injection point after compaction grouting was significant. Interestingly, variations in ultimate dry density and peak earth pressures perpendicular to the injection direction exhibited axisymmetric behavior around the injection point when comparing the dry density and earth pressure results. Furthermore, soil densification resulted in a decrease in suction. However, no significant effect of GP on suction at different soil positions was observed. Moreover, compaction efficiency decreased with increasing distance from the injection point, showing a strong linear relationship. In addition, the model results for the effective compaction range were basically consistent with the extrapolated values from the experimental results.

Evaluation of grouting effectiveness for Semi-Rigid pavement base layer cracks based on Time-Frequency domain signal characteristics of 3D GPR

This study aims to address the deficiency of rapid, comprehensive, and non-destructive methods for evaluating the effectiveness of grouting treatment on semi-rigid pavement base layer cracks. By integrating radar simulation with empirical measurements, we establish a comprehensive evaluation method for the grouting treatment effectiveness of pavement base layer cracks. Initially, we propose a GprMax simulation of crack models with varying grout-filled volumes, analyzing the time–frequency domain signal characteristics before and after grouting. Based on data sensitivity, thirteen time–frequency domain signal characteristics are selected as grading evaluation indicators. Subsequently, relying on an engineering case study, we conduct a graded evaluation of the grouting effect on base layer cracks, analyzing the correlation and weight of evaluation indicators to derive a comprehensive evaluation method. Field coring results confirm the accuracy of the comprehensive graded evaluation method.

Effectiveness of Grouting and GFRP Reinforcement for Repairing Spalled Reinforced Concrete Beams

Corrosion of steel reinforcement from chloride exposure can compromise the strength of reinforced concrete structures. Rust formation expands, applying pressure on concrete, resulting in cracks and spalling. Prompt repair is crucial for severe cases of spalling. This research assessed the efficacy of repair strategies for reinforced concrete beams post-spalling, including grouting and different techniques involving Glass Fiber Reinforced Polymer (GFRP) reinforcement. The research examined four variations of reinforced concrete beams, each sized at 150 mm × 200 mm × 3300 mm. Results showed that the standard beam (BK) had an average maximum load capacity of 29.74 kN. In contrast, the grouted beam (BGR) demonstrated a reduced maximum load of 14.39 kN, along with decreased steel and concrete strain compared to BK. This suggests that the grouting repair did not fully restore the beam's flexural capacity after spalling. Incorporating GFRP strips (BGRS) led to a marginal increase in the beam's maximum load, albeit remaining below BK, with lower steel and concrete strain than BK. However, the steel and concrete approached their yield points, indicating enhanced flexural performance. The full-wrap GFRP beam (BGRSF) experienced an 8.08% increase in maximum load compared to BK, with concrete strain surpassing BK, suggesting an enhancement in flexural stiffness. Doi: 10.28991/CEJ-2024-010-07-05 Full Text: PDF

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.

Mechanical characteristics and damage model for rock-like specimen with two parallel grout-filled cracks

To investigate the mechanical properties of rock-like specimens with two parallel cracks filled with grout, uniaxial compression tests in combination with digital image correlation (DIC) and acoustic emission (AE) techniques have been performed on grout-filled cracked specimens with different rock bridge dip angles β. Results indicated that with the increase of β, the uniaxial compression strength, cumulated AE count, AE energy, as well as shear crack proportion initially decreases and subsequently increases. The overall AE b-value and the DIC-based maximum principal strain initially increases and subsequently decreases as β increases. The failure mode also varies from tensile to mixed tensile-shear mode. Furthermore, a particle flow code (PFC) model, which considers the grout filling, grout-rock interface, and rock, has been proposed. Numerical results showed that the range of microcracks inclination angle first decrease from 70°−100° to 70°–90° and then increases to 70°–110°. Besides, existence of grout filling and changes of bridge angle leads to significant difference in PFC particle displacement, which can cause the changed of crack initiation positions and failure modes. Finally, a damage model considering stress intensity factor for the grout-filled specimen was established. Both of pre-crack damage and loading damage were considered in this model, and a damage repair factor was proposed to describe effect of grout filling. The results showed that grouting could can effectively suppress stress concentration caused by pre-existing crack, thereby changes the strength of cracked specimen.