Grouting Process Research Articles

Study on montoring simulation of urban space Environmental Science grouting by transient electromagnetic field

Grouting is one of the most effective methods to control underground space engineering disasters. It can effectively achieve a series of governance goals such as reinforcement of broken ground, reduction of settlement, and prevention and control of water and mud inrush. The form of the grouting process, the diversity of the grout, and the complexity of the stratum being injected are the key issues that restrict the development of grouting monitoring. Traditional grouting monitoring is mainly to control the grouting flow and pressure to achieve the grouting process and the state of grout diffusion. Routine testing The method can only perform spot inspection on the space or judge the overall space density, and it is difficult to monitor the spread of the slurry during the grouting process and the effective detection of the effect after the grouting. Based on the characteristics of transient electromagnetic sensitivity to low-resistance bodies, simple construction methods, and large detection depth, this paper uses theoretical analysis and numerical simulation as the main research methods to carry out forward simulation research on the diffusion process of grout in the formation. Through the establishment of numerical models for the different content of slurry in the middle layer of the same thickness layered formation, the possibility of using the electromagnetic field to explain the slurry diffusion in the grouting process is explored. Under ideal conditions, the transient electromagnetic response characteristics of the middle layer with different slurry conditions are analyzed. It is proved that the change of the field value of the transient electromagnetic secondary field before and after grouting can effectively judge the intrusion effect of the grout during the grouting process.

An Experimental Research on Crack Propagation Regularity During Fracture Grouting

A new grouting model test device has been developed to model the fracture grouting process and improve understanding of the crack propagation regularity during grouting. It was concluded that the propagation process of crack is not one-time formed but undergoes the sequential mode of “expansion, stagnation, re-expansion, re-stagnation” after fracture initiation. The smaller the grouting pressure is, the longer the stagnation time is, and the smaller the crack propagation velocity is. The crack width increases rapidly when the crack tip stagnates or the expansion speed is small. Research results can help achieve better grouting aims and realize grouting safety in practice

Macro and micro grouting process and the influence mechanism of cracks in soft coal seam

Grouting is an important method to reinforce soft coal roadway, and the presence of primary cracks in the coal body has an important influence on the grouting effect. With the discrete element simulation method, the grouting process of the soft coal seam was simulated. The mechanism of primary cracks on grouting was revealed, while the influence of fracture characteristics and grouting pressure on the grouting effect was analyzed. The results demonstrated that grouting in the soft coal seam involves the stages of seepage, rapid splitting, slow splitting, and stability. Due to the presence of primary cracks, the grouting diffusion radius increased significantly. Under the slurry pressure, the tensile stress concentration was formed at the crack tip, and the slurry split the coal once the splitting pressure was reached. In addition, the distribution characteristics of fractures are found to have a great influence on the grouting effect. It is observed that smaller fracture spacing is associated with a larger slurry diffusion radius and thus easier penetration of the primary crack tips. The fracture angle affects the direction of fracture propagation. The secondary fracture formed by splitting is a tensile fracture, which is more likely to extend along the direction parallel to the maximum principal stress. Overall, these simulation results have guiding significance for the setting of reasonable spacing of grouting holes in the practice of grouting engineering.

Field study on axial behavior of instrumented post-grouted steel pipe micropiles in tropical lateritic soil

This paper presents a field study on the axial behavior of new configuration of steel pipe micropiles in tropical lateritic soil. The micropiles were installed following a two-step grouting process with high injection pressures at a new experimental site located at the University of Campinas (Unicamp). The main innovation of the micropiles relies on the use of high-strength steel pipes as a drilling tool, casing protection, structural component and injection device. Full-scale pile loading tests were performed under compression and tension loads to investigate the axial behavior of the micropiles. The micropiles were instrumented along the shaft with electrical extensometers, and they were monitored during the progress of the loading tests. The load–movement responses, elastic moduli, axial load transfer mechanism, and unit bond stress relating to the micropiles and their interactions with the tropical soil were measured and evaluated. The bearing capacity of the post-grouted micropiles was considerably improved by the proposed post-grouting technique. The ultimate load capacity of the grouted steel pipe micropile under a compression load is approximately the same under a tension load. The average ultimate bond strength was 99 kPa and 100 kPa for the micropile under compression and tension, respectively. The distribution of unit bond stress along the shaft of the micropile under compressive and tensile load presented a post-peak softening behavior. The average ultimate grout-to-ground strength at the soil–micropile interface was 2.4 and 1.7 times greater than other nongrouted and non-injected piles installed in the same soil conditions at Unicamp.

Study on the Calculation Method of the Diffusion Range of Grouting Slurry for a High-speed Railway Ballastless Track Subgrade

Grouting engineering is the most convenient and quick way to deal with postconstruction settlement. Based on the investigation of the Beijing Shenyang high-speed railway in the early stage, the microdestructive force of grout on the soil mass in the process of grouting with the method of fluid solid coupling theory was analyzed. The numerical simulation results show that, in the grouting process, the greater the grouting pressure, the wider the diffusion range of the slurry and the greater the damage to the microscopic contact force of the slurry to the soil; in addition, when the grouting pressure is below 0.15 MPa, the diffusion form of the slurry in the soil is osmotic grouting; when the pressure is about 0.3 MPa, the diffusion form of the slurry in the soil is compacted grouting; on the basis of the simulation results, a deeper research is carried out, and the calculation formula of the slurry diffusion curve is obtained. It fills in the blank of the theoretical study of the slurry diffusion curve. In this paper, the diffusion formula of grouting slurry can be used in the theoretical study of clay grouting, and it can be used as a reference for practical engineering.

Numerical Simulation of Stress and Strain Behavior of Foundation Soil under Compensation Grouting

To prevent the development of settlements and heave-up of facilities, the compensation grouting technique is used. The article reports the data of numerical simulation of the compensation grouting process as illustrated by the physical experiment performed by Luca Mazini, Ph.D. from La Sapienza Rome University (Rome, Italy). Simulation is performed with the JulyS program developed by the article authors for the ECM. The program implements the finite element method in a three-dimensional approach with Professor L.N.Rasskazov’s non-linear “energy” soil model. Different simulation of supplementary volume arrangement in the sandy soil under grouting in the finite element method approach is reviewed. The numerical simulation data are compared with the field experiment.

Simulation of Mosul Dam Break Using Finite Volume Method

Mosul dam is an earth-fill embankment located north of Iraq on the Tigris River forming a reservoir with 11.11 km3 water storage capacity which is the largest dam in the country. The dam is built on a rock bed foundation, in which the dissolution process is dynamic in the zone where gypsum and anhydrite layers present. During the construction development seepage locations were found in the dam foundation and the grouting process is in progress until now to control this problem. Therefore, the possibility of the Mosul dam break is highlighted by previous studies. In this research, a FORTRAN code based on the finite volume method is modified to solve the two-dimensional shallow water equations and simulating the Mosul dam break. The computational domain discretized using unstructured triangular mesh. The solver applied Harten lax van leer with contact (HLLC) wave approximate Riemann solver to calculate the cell interface fluxes, and the semi-implicit scheme employed to solve the friction source term. The numerical scheme applied to two benchmark test cases, and the results showed that the presented model was robust and accurate especially in handling wet/dry beds, mixed flow regimes, discontinuities, negative water depths, and complex topography. The results of this study demonstrate that flood waves may reach the center of Mosul city in < 6 h and water depth may rise to 34 m after 7 h of Mosul dam breaking. Finally, the simulation results of the Mosul dam break were used to prepare an emergency action plan.

An Intelligent Prediction Method of the Karst Curtain Grouting Volume Based on Support Vector Machine

The prediction of the grouting volume is a very important task in the grouting quality control. Because of the concealment and complexity of the karst curtain grouting engineering, there is little research on the prediction of the karst curtain grouting volume (KCGV), and the prediction is hindered by the practical problems of small samples, high dimensions, and nonlinearity. In the study, based on the basic idea of support vector machine (SVM), a multiparameter comprehensive intelligent prediction method of the KCGV is proposed, which overcomes the limitation of few sample data in practical engineering. This method takes the grouting construction conditions and the slurry conditions which control the slurry diffusion as the input parameters, which are the basic data which can be easily obtained in the field grouting process. This feature greatly improves the prediction accuracy and generalization performance of the method. The intelligent prediction method of the KCGV based on SVM is applied to a typical karst curtain grouting project. The mean absolute error of the prediction results is 3.47 L/m, and the mean absolute percentage error of the prediction results is 5.97%. The results show that the proposed prediction method has an excellent prediction effect on the KCGV and can provide practical and beneficial help for the field karst curtain grouting project.

Grouting Power Prediction Using a Hybrid Model Based on Support Vector Regression Optimized by an Improved Jaya Algorithm

Grouting power is a vital parameter that can be used as an indicator for simultaneously controlling grouting pressure and injection rate. Accurate grouting power prediction contributes to the real-time optimization of the grouting process, guaranteeing grouting safety and quality. However, the strong nonlinearity of the grouting power time series makes the forecasting task challenging. Hence, this paper proposes a novel hybrid model for accurate grouting power forecasting. First, empirical wavelet transform (EWT) is employed to decompose the original grouting series into several subseries and one residual adaptively. Second, partial autocorrelation function (PACF) is applied to identify the optimal input variables objectively. Then, support vector regression (SVR) is adopted to obtain prediction outcomes of each subseries, while an improved Jaya (IJaya) algorithm by coupling chaos theory and Lévy flights to improve the algorithm’s accuracy performance is proposed to optimize the SVR hyperparameters. Finally, the prediction results of decomposed subseries are superimposed to produce the final results. A consolidation grouting project is taken as a case study and the computation results with the RMSE = 0.2672 MPa·L/min, MAE = 0.2165 MPa·L/min, MAPE = 3.85% and EC = 0.9815 demonstrate that the proposed model exhibits superior forecasting ability and can provide a viable reference for grouting construction.

Shear behaviour of sand-concrete interface with side post-grouting considering the unloading effect

Side post-grouting bored-pile foundations are widely used in geotechnical engineering. However, few studies have focused on analyzing the shear behaviour of soil and concrete while considering the grouting process. A total of 48 groups of self-developed, large-scale direct shear experiments were conducted to investigate the shear behaviour of sand-concrete interface with side-grouting, focusing on the effect of soil stress unloading and the on-site roughness measurements of bored pile. The influence of the grouting volume V, unloading rate α and interface roughness R on the shear behaviour are discussed, and the grouting modes and shear band deformation are investigated. The experimental results indicated that the grouting volume has a limited effect on improving the shear strength, and an optimal grout quantity will exist in post-grouting engineering. In addition, the unloading has a non-negligible influence on the grouting modes.

Grouting Reinforcement Technology of Weak Fractured Rock Mass in Subway Open-cut Station

In the process of subway open-cut station construction, excavation deformation seriously threatens the safety of municipal pipelines and buildings. To ensure the effectiveness of grouting reinforcement, drilling exploration and pressure water test were conducted on the basis of the grouting reinforcement project of the excavation of an open-pit station in Qingdao metro, the permeability coefficient and crack characteristics were studied, and the equivalent crack width was calculated on the basis of cubic law. To determine the injectability index of grout and realize the optimal selection of grouting materials, the statistical distribution law of the equivalent crack width was analyzed on the basis of the Pareto distribution, and an effective method of grout selection was proposed. The PQT curve in the grouting process was analyzed by flow dimension theory to realize the dynamic adjustment of the grouting process. Finally, the grouting reinforcement effect was evaluated on the basis of the core sample and borehole TV. Results show that if the permeability coefficient is subject to Pareto distribution with parameters tmin and k, then the distribution curve of the permeability coefficient in the logarithmic coordinate is a straight line; the equivalent crack width obtained on the basis of the cubic law is also subject to the Pareto distribution with parameters bmin and 3k. Therefore, the equivalent crack width distribution curve can be obtained to provide a basis for the grout selection.

Field Test Research on Film Bag Grouting in Strongly Weathered Stratum Overlying Subway

A strongly weathered stratum needs to be reinforced by grouting before tunnel excavation due to its poor self-stability. This work studied the law of surface uplift caused by grouting in a strongly weathered stratum overlying a subway. A strongly weathered stratum overlying a subway section was taken as the research object, and the field test method was used to reveal the time and space variation characteristics of the surface uplift with grouting reinforcement. Then, the influence of the grouting reinforcement technology, quantity, and material on the maximum surface uplift value in the practical grouting process was analyzed. The results show the following. Regardless of whether film bag grouting is used or not, the uplift value of the monitoring points is directly proportional to time, and the growth rate of the uplift value tends to accelerate. The spatial distribution of the surface uplift is mainly related to its distance to the grouting point. In addition, the maximum uplift value of the film bag grouting technology is 32.1% lower than that of the ordinary grouting technology; given the same grouting materials and technology, the grouting amount increases by 50%, and the surface uplift value increases by 121%. Moreover, the C-S slurry exhibits rapid setting, a small diffusion range, and a large thickness of the grouting vein; the surface uplift value of the C-S slurry is 3.08 times that of the cement slurry. The field test research conclusion is applied to practical engineering, where the final uplift value is 1.8 to 2.5 cm, and the average permeability coefficient of the inspection hole is 3.52×10−7 cm/s, which reflects a good engineering governance effect.

Development and experimental research of a low-thermal asphalt material for grouting leakage blocking

AbstractTunnel water burst is among the common severe geological hazards in deep buried tunnel projects in China and throughout the world. Asphalt grouting is an effective method to block seepage channels in macroporous strata under the condition of flowing water, but it has defects such as a high heating temperature, complex high-temperature construction technology, and poor controllability during the grouting process. A type of “water-in-oil” low-thermal asphalt was developed in this study. It can cool and solidify and not be diluted when encountering water, and its construction temperature can be below 80°C. Experimental research on the physical and mechanical properties of the low-thermal asphalt leakage-blocking material was completed, including proportion experiments, fluidity, sensitivity to temperature, one- and two-dimensional indoor diffusion experiments, and impact experiments, which presented its physical and mechanical properties and can provide guidance for the application of the material in site projects.

Grouting rock fractures under condition of flowing water

Grouting is generally applied as an effective way to seal rock fractures, reduce permeability, decrease deformation, increase strength of rocks, and to stop the water flow through the jointed rock mass. But grouting rock fractures under condition of flowing water depends greatly on experiences of professional engineers, without sufficient theoretical guidance to refer to, as no commonly accepted and reasonable theoretical models are available. To describe the grouting process of fractures in flowing water, and put forward reasonable grouting guidance suggestions. The present work established a theoretical model for grouting into a fracture with flowing water. Considering boundary conditions, a streamline equation of grouting diffusion trajectory with flowing water was derived, and analyzed the influence of boundary effect on grouting diffusion law. The simulation tests of grouting rock fracture with flowing water were carried out on the self-developed fracture grouting experimental platform, and the results were compared with the theoretical prediction results, which verified the rationality of the theoretical model. The results show that there are three types of diffusion of quick-setting slurry under condition of flowing water. The existence of boundaries can increase the penetration along the direction of the flowing water both downstream and upstream, but it weakens the penetrability in the vertical flow direction. Rock fractures with a high water velocity require a high grouting flow rate, however, it is not the higher the better for determining the relevant grouting flow rate, a decrescent ratio between these two parameters should be ensured as a precondition.

A novel real-time monitoring system for the measurement of the annular grout thickness during simultaneous backfill grouting

Backfill grouting is generally used to limit the ground surface settlement induced by shield tunneling. The control of this settlement constitutes a major challenge in the use of shield machines in urban areas. This control could be monitored using the ground penetrating radar (GPR) for its high precision and efficiency. This paper presents the development and use of a real-time back-fill grouting monitoring system, which is based on the integration of a new GPR monitoring system in a shield tunnel machine. The three-dimensional Finite Difference Time Domain (FDTD) was adopted to analyze the propagation of the electromagnetic waves in the backfill grouting. After verification of the use of a GPR center frequency band of 300 MHz, the system was used in real in the construction of the R3 of Jinan metro. The application showed that only 3–4 min were required for the backfill monitoring, which provided enough time to adapt the grouting process to the settlement requirements. Results also allowed establishing criteria for the evaluation of the grouting thickness. The use of this system allowed engineers to limit the tunneling-induced settlement in urban areas.

Understanding the Effect of Cementitious Grouting Pressure on Micro-Fracture Permeability for Rock Reinforcement Underground: A Lab Study

In grouting support projects, due to the small concealment of micro-fractures, the support effect often fails to meet design requirements. The percolation effect is a common factor that causes grouting failure, and the influence of grouting pressure on the percolation effect is very obvious. In this article, a design of a micro-fracture grouting experimental system is presented that can realize high-pressure grouting and then uses a variety of ultrafine cements to carry out high- and low-pressure grouting tests under different fracture opening conditions, thereby obtaining the grouting pressure and accumulated grouting weight during the grouting process. The results show that a combination of the grouting pressure curve and the cumulative grouting weight curve can determine whether the ultrafine cement will have a percolation effect. Increasing the grouting pressure can reduce the critical fracture opening value and also reduce the occurrence of the percolation effect. The research results provide a theoretical basis for the high-pressure grouting of micro-fracture rock masses and offer certain guiding significance for the design of high-pressure grouting support schemes.

A numerical study of the influence of cyclic grouting and consolidation using TOUGH2

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.

Effect of Nano-CaCO3 on the Sealing Efficiency of Grouts in Flowing Water Grouting

Flowing water grouting is a big challenge in the tunneling and underground engineering. To enhance the early strength and grouting effectiveness of slurry for flowing water grouting, nano-CaCO3 and fly ash were mixed with cement based grout. A series of physical simulation tests were conducted to simulate the flowing water grouting process in rough rock fracture, and investigate the effect of nano-CaCO3 content on the fluid pressure and sealing efficiency of grouts. Results of viscosity tests show that the viscosity of grouts decreased with an increase of nano-CaCO3 content. Scanning electron microscope (SEM) tests indicate that nano-CaCO3 can promote the formation of fibrous hydrates and enhance the flowing water resistance of grouts. Increasing nano-CaCO3 content resulted in the first increase while later decrease of maximal fluid pressure (MFP) and sealing efficiency (SE) of grouts. Reducing water cement ratio of grouts and incorporating fly ash can effectively improve the SE of flowing water grouting.

Numerical analysis of material modeling rock reinforcement in 2D FDEM and parameter study

This paper introduces a simplified smooth rock reinforcement modeling approach based on the 2D combined finite discrete element method (FDEM). The goal is to facilitate modeling the end grouting process and the full grouting process of rock bolts reinforcement, and to improve further understanding of the interaction between bolt, grouting, and host rock based on material mechanical behavior. The study analyzed the mechanical model and fracture mode extracted from experimental results using the rebar bolt specimen. This facilitated the study of the bond strength component of the rib. Then, the bond force-slip relationship was explored using physical modeling with different combinations of bolt and cover constraints, with different types of grouts and rocks. Corroboration of the laboratory axial pullout test was then conducted. A power law for the stress-displacement of the radial component of bond force was generated, to elaborate simplified modeling method and the data range of parameters in the diverse combination of constraining forces. Then, the action law was implemented into the material rock reinforcement model in FDEM. The verification process, done by comparing the bond force-slip curve with the physical modeling, shows the model can effectively reflect the action rule of rebar bolts. The model simplifies rebar bolt modeling and adds a new ability to model rock reinforcement features into FDEM, making the FDEM technology extend fundamentally.

Study on the Effects of Grouting and Roughness on the Shear Behavior of Cohesive Soil-Concrete Interfaces.

Grouted soil–concrete interfaces exist in bored piles with post-grouting in pile tip or sides and they have a substantial influence on pile skin friction. To study the effect of grouting volume on the shearing characteristics of the interface between cohesive soil and concrete piles with different roughness, grouting equipment and a direct shear apparatus were combined to carry out a total of 48 groups of direct shear tests on cohesive soil–concrete interfaces incorporating the grouting process. The test results showed that the shear behavior of the grouted cohesive soil–concrete interface was improved mainly because increasing the grouting volume and roughness increased the interfacial apparent cohesion. In contrast, increasing the grouting volume and roughness had no obvious increasing effects on the interfacial friction angle. Interfacial grouting contributed to the transition in the grouted cohesive soil from shrinkage to dilation: as the grouting volume increased, the shrinkage became weaker and the dilation became more obvious. The shear band exhibited a parabolic distribution rather than a uniform distribution along the shearing direction and that the shear band thickness was greater in the shearing direction, and it will become thicker with increasing grouting volume or roughness. The analysis can help to understand the shear characteristics of soil–pile interface in studying the vertical bearing properties of pile with post-grouting in tip or sides.