Grout Diffusion Research Articles

Analysis of Stress and Deformation and Stability of Grouting Wall and Mud Control in Tunnel Excavation

To prevent the grout and fissure water from gushing out of the working face and to ensure the effective diffusion of grout along the fissure under the action of high grouting pressure, the grouting wall should be set up on the working face before grouting to ensure the grouting effect. This study found that under the grouting pressure of 4MPa, the grouting wall model with a thickness of 80cm is more stable than that with a thickness of 50cm. At the same time, for the grouting stop wall with a thickness of 80cm and a dip angle of 50°, both the horizontal deformation and the settlement of the vault have met the requirements of the construction specification in the process of simulated grouting calculation.

Non-linear spring model for backfill grout-consolidation behind shield tunnel lining

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

Model study on backfill grouting in shield tunnels based on fractal theory

Fractal theory demonstrates significant merit in the feature expression of forms of matter in nature. This study uses fractal theory to study the backfill grouting of a shield tunnel. The seepage path was considered as a seepage mesh inserted into the rock-soil mass. For the fractal features of the seepage mesh, the formulas for the diffusion distance and the pressure contribution of grout were derived. The results showed that the diffusion equations of different grout patterns (Newtonian fluid and Bingham fluid) were of a uniform form after calculation, and the equations for the pressure distribution of grout with a change in radius were identical. The diffusion distance of grout increased with increasing grouting time, and there was no indication that the development of diffusion distance tended to be gradual; the downward tendency of the grout diffusion velocity was not moderated. The segment pressure increased with an increase in the diffusion distance. With a constant diffusion distance, a greater grouting pressure produced a greater segment pressure. The favorable performance of grout was attributed to an appropriate mixture ratio. An improper mixture ratio resulted in a smaller reinforcement area in the stratum, which impaired the stability of the shield tunnel.

The Effect of Soil Porosity and Geopolymer Viscosity on Spreading Grouting in Weathered Clay Shale

Fly ash geopolymer is a potential material for the stabilisation of clay shale. Therefore, this research determines the effect of soil porosity (n), binder activator ratio (f/a), and geopolymer viscosity on the injected grout volume (Vi ) and soil-grout column of weathered clay shale. The research was carried out using fly ash as a geopolymer binder, dissolved in Na2SiO3 and NaOH(10M) with an activator ratio of 1:1. The binder activator ratios were 0.50, 0.75, 1.0, and 1.25, with injection applied in the compacted clay shale using three dry densities corresponding to the porosity of 0.42, 0.48, and 0.54. Furthermore, a cylindrical specimen with 46 mm diameter and 100 mm height was used to carry out this test. A hole with a diameter of 12 mm and 80 mm depth was bored at the centre of the specimen to model a fracture grouting method, which was injected with the geopolymer by applying a pressure of 100 kPa for 20 minutes. The research found that the higher the binder activator ratio, the lesser the viscosity obtained; therefore, the grout easily penetrated the pores between the soil particles. As a consequence, more volume of geopolymer could be injected in soil. Binder activator ratio lesser than 0.75 was ineffective for the injection method, and binder activator ration between 1.00 - 1.25 was recommended for the grouting injection method. A new equation to determine the grout diffusion was proposed based on this experiment, as written in the equation .

Test Method for the Solubility Model of Physical Blowing Agent of Self-Expanding Polymer

This paper aims to present a solubility model of physical blowing agent (PBA) for a kind of commonly used self-expanding polymer on engineering. The self-expanding polymer contains Component A (isocyanate) and Component B (polyhydric alcohol, PBA, water, and catalyst). Component B grout of the polymer, which contains PBA, was heated to measure its temperature and volume variations. Based on the principle of mass conservation and Clapeyron equation, the solubility curve of PBA with respect to temperature was calculated. The solubility curve was then applied to simulate the foaming process. A two-component polymer grout foaming experiment was then carried out to verify the applicability of the measured solubility curve. The simulated changes of temperature and density with respect to time of polymer grout were analyzed and compared with experimental results. The error of both sets of curves is within 5%, which shows a good agreement among them and proves the feasibility of the solubility model. This study provides a relatively complete test and verification process for the solubility model of PBA, which lays a theoretical foundation for both the polymer grouting diffusion mechanism and engineering application.

The Split-Permeation Grouting Mechanism of Loose and Broken Coal Rock Masses considering the Temporal and Spatial Characteristics of Slurry Viscosity

Quick-setting grout has time-varying characteristics, and the space porosity of the injected medium changes after being grouted. The above two points need to be considered when loose and broken coal rock masses are grouted with rapid-setting grout. In other words, the coupling effect of the slurry-coal rock mass causes the slurry to exhibit the temporal and spatial characteristics of slurry viscosity (TSCSV). Based on the Bingham fluid constitutive model, a capillary group model with a linear increase in diameter was created, and a one-dimensional penetration grout diffusion model was established considering the TSCSV. The one-dimensional visualization splitting-permeation grout diffusion simulation test system was designed to obtain the space porosity of the broken coal rock mass under different final grouting pressures to obtain the law of the changes in grouting pressure and diffusion height with time under the condition of a fixed grouting rate. Furthermore, the mechanism of splitting-permeation grouting in loose and broken coal rock masses is analysed in depth considering the TSCSV. The results showed that the space porosity of coal rock masses increases linearly. In addition, the calculated value of the slurry diffusion distance was 0.93 – 1.1 times the experimental value considering the TSCSV. The calculated value was in good agreement with the experimental value. The calculated value of the final pressure of orifice grouting was approximately 1.5 times the test value without considering the unevenness of the space porosity distribution (USPD). The grouting pressure was overestimated without considering the USPD. Therefore, the TSCSV of the quick-setting slurry should be fully considered in the grouting design.

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.

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.

Numerical Investigation of Grout Diffusion Accounting for the Dynamic Pressure Boundary Condition and Spatiotemporal Variation in Slurry Viscosity

Abstract This paper proposed an improved stepwise algorithm to simulate the grout diffusion in a single fracture considering the dynamic grouting parameter boundary condition and the spatial- and t...

Experimental and Numerical Study on the Permeation Grouting Diffusion Mechanism considering Filtration Effects

Permeation grouting estimation is important for the design of grouting engineering. Filtration effects and rheological behavior play a key role in permeation grouting diffusion of cement-based grouts. To better understand the effect of filtration and grout rheological behavior on the grouting diffusion mechanism, one-dimensional permeation grout injections in sand columns under constant flow rate were performed by a self-developed experimental procedure. Experimental results showed that there were dramatic variations in rheological parameters and porosity along the diffusion distance. However, the rheological parameters changed slightly with time for each position. Based on the experimental results, a numerical model considering the filtration effect and grout rheological behavior was established to describe the mechanism of grout flow in porous media. In addition, numerical solutions from the proposed model are compared with the experimental results. The comparative results showed that the proposed numerical method can match the laboratory tests well. Finally, the effects of the grout flow velocity and the water/cement ratio of the grout on the diffusion mechanism are also discussed.

Analysis of application of cement paste grouting curtain in coastal environment

Zhejiang Datang Wushashan power plant is composed of farmland and aquaculture ponds in the Xizhou seawall, which are backfilled with artificial riprap. In order to block the seepage path in the rock fill layer, the vertical curtain cement paste grouting anti-seepage reinforcement measures are adopted to block the connection between the underground water and the surrounding surface water in the plant area, so as to achieve the purpose of gas closure. This paper mainly analyzes and evaluates the technical indexes, such as grout diffusion range and impermeability, of the cement paste grouting curtain, via field tests and two dimensional numerical simulation based on the platform of PFC2D or Geostudio.

Model Test on Segmental Grouting Diffusion Process in Muddy Fault of Tunnel Engineering

In order to realize the diffusion law of segmental grouting in muddy fault of tunnel engineering, a three-dimensional grouting diffusion simulation test has been done. Three times of grouting operation have been done for three adjacent sections in grouting pipe. Grouting pressure, injection rate, soil pressure field, and seepage pressure field have been real-time monitored in three grouting stages. The effect of segmental grouting operation on soil pressure field and effective stress field has been analyzed. Results show that previous grouting operation can affect later grouting operation. Due to previous grouting operation, the grouted stratum can be compacted and grouting diffusion will conquer greater resistance in later grouting stages. Correspondingly, grouting pressure increases and injection rate decreases in the later grouting stage. There exists a limited influence range for a single grouting operation. For every grouting stage, soil pressure and effective stress in the section which the injection hole locates in are affected effectively by grouting operation. By contrast, soil pressure and effective stress in section away from injection hole are affected relatively weakly by grouting operation. With distance to injection hole increasing, compaction degree and reinforcement effect of grouted muddy fault decay in space. Multisegmental grouting method has significant advantages over single grouting method. Ineffectively compacted area by previous grouting operation can be effectively compacted by later grouting operation from adjacent injection hole. As a result, uniformity of grouting reinforcement effect can be improved, and weakly reinforcement area can be reduced.

Experimental study on the diffusion characteristics of polyurethane grout in a fracture

Although polyurethane grouting has been widely used in fractured rock masses, the understanding of polyurethane diffusion characteristics still needs to be enhanced significantly. To analyse the diffusion mechanism of the polyurethane grout in the fracture, physical simulation experiments were conducted using a self-designed device. Additionally, the influence of grouting quantity on the grout diffusion distance and pressure distribution was investigated. The results indicated that the diffusion radius and pressure field increased with the increase in grouting quantity. Furthermore, the pressure growth rate and grout diffusion rate during the early self-expansion stage is directly proportional to the amount of polyurethane grout injected. However, the change in grout pressure is not synchronised with that of the diffusion radius. Hence, a hysteresis effect was observed for the pressure field change. Additionally, the grout pressure, which was not distributed evenly, decreased along the diffusion radius as it moved away from the grout hole. Furthermore, we derived the relationship between maximum diffusion radius and grouting quantity. Therefore, this study provides a better understanding of the diffusion law of polyurethane grouting in fractured rock masses.

Two-phase analytical model of seepage during grout consolidation around shield tunnel considering the temporal variation in viscosity and the infiltration effect

Studies on grout consolidation after synchronous grouting around shield tunnels have ignored the expansion of the grout–groundwater interface and the difference in the permeabilities of the grout and water in the stratum. The process of grout pressure dissipation and diffusion in the stratum was solved with a two-dimensional two-phase seepage model, with which the head losses caused by grout diffusion in the stratum and groundwater seepage in the stratum under the ‘push-displacement effect’ were studied together. In addition, the influence of the temporal variation in viscosity and the infiltration effect were considered. Then, a two-phase analytical seepage model of consolidation for shield grouting considering the temporal variation in viscosity and the infiltration effect was established. A numerical algorithm was designed to solve the theoretical model with the difference method. The analytical model was verified by comparison with the results of numerical simulation. Furthermore, the main parameters in the analytical model were analysed. The results show that the temporal variation in grout viscosity and the infiltration effect greatly influence the stable pressure value and the loss rate of the volume of grout after consolidation. Among the main parameters in the model, the permeability coefficient of the stratum is the most sensitive.

A diffusion model for backfill grout behind shield tunnel lining

AbstractThis paper presents an analytical model to investigate backfill grout diffusion behind tunnel segmental lining, in which the backfill grout is taken as a Bingham fluid. The analytical model of grout diffusion is derived based on force–equilibrium principle, Darcy's law, and the law of momentum conservation of the grout. Time‐dependent grout diffusion pressure and distance are highlighted in the model. The proposed grout diffusion model is applied in two field cases: Metro Lines No. 9 and No. 4 in Shanghai City. The results show that the proposed model agrees well with the measured grout diffusion distance in the field. Parametric studies are then conducted, implying that grout diffusion distance along the radial direction of tunnel lining is proportional to either hydraulic conductivity or initial grout pressure, whereas it is in inverse proportion to the yield stress of backfill grout. The distributions of initial grout pressure exert key influences on the grout diffusion distance and grout diffusion pressure behind tunnel segment lining.

Unsplit Youngs Method for Tracking the Moving Interface of Expansible Grout

Accurately tracking the moving interface is one of the most critical challenges in numerically modeling grout diffusion in fractures. The traditional Youngs method does not consider fluid transport to the oblique adjacent cell, which leads to repeated calculation and error accumulation. Based on the interface reconstruction technology, this paper introduced the idea of the unsplit algorithm to capture the grout-air interface. The unsplit interface advancement formulas were derived considering the fluid fluxes from the central cell to the oblique adjacent cells in the structured cell system. The numerical method based on the unsplit algorithm was validated by examples of predicting the propagation of expansible grout in a fracture. Results show that the diffusion pattern and grout front position calculated by the proposed method are in better agreement with the analytical solution compared with the traditional split algorithm. The new method can effectively improve the grout-air interface tracking accuracy.

Lattice Boltzmann simulation for grout filling process during simultaneous backfill grouting of shield in tunnel construction

Over the years, it has become obvious that simultaneous backfill grouting is of great significance to the design of the tunnel lining and process control of shield construction. It is essential to know the grout pressure distribution around the tunnel lining. The purpose of this study is to seek an alternative method to simulate the grout diffusion process and obtain pressure distribution of different time during simultaneous backfill grouting of tunnel construction. A lattice Boltzmann method (LBM) based free surface flow model is introduced and modified, and a Smagorinsky large-eddy simulation model serves to deal with the small-scale turbulent problem, which is a challenge for LBM to simulate the large-scale real-world engineering. The simulation results obtain the grout filling state with time and pressure distribution around the tunnel lining. Additionally, the grout pressures on site are measured at a ring in line 8 of Chengdu Rail tunnel, and the measurement results are also compared with ones taken from numerical simulation, it is showed that the numerical results are consistent with that of measurement on the whole. Through simulating different grouting strategies, it is concluded that for four-holes grouting schemes, the grouting pressures of upper holes are significant for the grout pressure distribution and should be paid most attention in construction.

Experimental and Numerical Study on a Grouting Diffusion Model of a Single Rough Fracture in Rock Mass

Grouting reinforcement is an important method used to solve problems encountered during tunnel construction, such as collapse and water gushing. The grouting diffusion process is greatly influenced by the structural characteristics of the fractures in a rock mass. First, an analytical grouting diffusion model of a single rough fracture under constant-pressure control is established based on the constitutive equation of a Bingham fluid. Second, the “quasi-elliptical” grouting diffusion pattern under the influence of roughness is revealed through a grouting diffusion experiment, which is conducted with an independently developed visualized testing apparatus. Furthermore, the analytical formula of roughness-corrected grouting diffusion characterized by the saw tooth density is established. Finally, an elaborate numerical simulation of the diffusion process of cement slurry (Bingham flow type) in a single rough fracture is carried out by introducing the Bingham–Papanastasiou rheological model. The temporal and spatial distribution characteristics of the velocity field and pressure field during the grouting diffusion process are analyzed as well. Moreover, the method and range of the roughness correction factor in the analytical grouting diffusion model are proposed based on the fracture roughness unit.

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.

Study on Fracturing and Diffusion Mechanism of Nonslab Fracturing Grouting

The coupling effect of a slurry and the fractured rock layer controls a spatial attenuation of the fracture channel width and grouting pressure from a grouting hole to the slurry top of fracture diffusion. This paper comprehensively considers the influencing factors such as the mechanical properties of the injected rock mass and the time-varying characteristics of the serous viscosity and introduces the control equation of the fracture channel width to establish a single-fracture nonslab fracturing grouting model. Combining the motion law of the slurry with the extension form of fracture, the equation of slurry diffusion motion, considering the fracture geometry and the time-varying characteristics of the serous viscosity, is derived. Comparing this equation with the existing theories and experiments, the validity and reliability of the theory are verified. In this paper, the effects of rock elastic modulus, slurry viscosity, and grouting rate on the fracturing grouting diffusion law of rock mass are analyzed. It is pointed out that when fracturing grouting in deep rock layers, a larger initial grouting rate and grouting pressure should be selected in the early stages of grouting to generate or penetrate fractures in the rock layer. Also, when the grouting pressure is stable, it is appropriate to increase the viscosity so that the slurry can quickly gel in the fractures thus sealing the fractures.