Grout Diffusion Research Articles

Numerical simulation of polymer grout diffusion in a single fracture

Polyurethane grouting materials, a type of expansible grout, has played a significant role in the rehabilitation of public infrastructures, such as lifting the slab in a road and reinforcing the broken wall rocks in a tunnel. Due to the unique expansion characteristic of polyurethane materials induced by the chemical reaction, its diffusion mechanism in rock fracture is rather complicated. Based on a numerical method presented in a previous paper, the diffusion law of expansible grout in a single fracture is studied considering the time-varying density and viscosity of the grout tested by experiments. The grout diffusion radius, pressure distribution and velocity field are calculated by the numerical model combining the finite volume method (FVM) and volume-of-fluid (VOF) method. Taking the gel time into account, the characteristics of flow field distribution during the grout movement process are investigated on five different cases and the influences of grouting quantity and fracture aperture on grout diffusion behavior are analyzed, which can reveal some diffusion law of expansible grout in a single water-free fracture.

Study on the Processes of Water and Grout Seepage in Porous Media Using Resistivity Method

In this study, we simulated the process of water and chemical grout seepage into porous media using a mix of quartz sand, calcite powder, and neutral silicone adhesive as a microscopically porous media and transparent poly(methyl methacrylate) tube to make the test model. During the test, we monitored multisectional electrical resistances of the porous media in real time, realized the visualization of the processes of water and grout seepage as well as grout solidification, and investigated the characteristics of changes in resistivity and seepage during water and grout injection into porous media. The study showed that (1) in the process of water injection into the unsaturated porous media, the water-seepage interface was clearly observed and changes in resistivity of the model material can be used to determine water-seepage velocity and interface position; (2) in the range of grout diffusion into the saturated porous media, the concentration of grout gradually decreased from along the diffusion direction, showing no obvious interface between the grout diffusion and nondiffusion areas; and (3) the resistivity of the saturated porous media in the grouting process greatly changed, and this change could be used to determine grout diffusion range, relative concentration in the diffusion range, and solidification degrees. This study provides a new way to monitor the grouting process and help guide the grouting design.

Research status and future trends on surface pre-grouting technology in reforming wall rock of vertical shafts in coal mines in China

In the mine construction, the surface pre-grouting technology is an important method to prevent water blast in excavation process of vertical shaft when the shaft must pass through the thick, water-rich and high water-pressure bedrock aquifer. It has been nearly 60 years since the technology was used to reform wall rock of vertical shaft in coal mine in China for the first time, and the existing technology can basically meet the needs of constructing 1000m deep vertical shaft. Firstly, the article introduces that in view of Magg’s spherical seepage theory and Karol’s spherical seepage theory, Chinese scholars found that the diffusion of grout from borehole into the surrounding strata in horizontal direction is irregular through a lot of research and engineering practice of using the surface pre-grouting technology to reform wall rock of vertical shafts, and put forward the selecting principles of grout’s effective diffusion radius in one grouting engineering; Secondly, according to the shape of the grouting boreholes, surface pre-grouting technology of vertical shaft is divided into two stages: vertical borehole stage and S-type borehole stage. Thirdly, the development status of grouting materials and grouting equipment for the technology is introduced. Fourthly, grouting mode, stage height and pressure of the technology are introduced. Finally, it points out that with the increasing depth of coal mining in China, the technology of reforming wall rock of 1000~2000m deep vertical shafts will face many problems, such as grouting theory, grouting equipment, grouting finishing standard, testing and evaluation of grouting effect, and so on. And it put forward a preliminary approach to solving these problems. This paper points out future research directions of the surface pre-grouting technology in China.

Development of an Optimum Forepole Spacing (OFS) determination method for tunnelling in silty clay with a case study

Phase III of Harbin Metro Line #1 was constructed in low to medium plasticity silty clay. In the primary design, forepoles with a spacing of 0.8 m were used as pre-support. However, it was found in the practice that the drilling rate was low and the grouting diffusion range was limited when the water content was low in the silty clay. In order to determine the optimum forepole spacing in relation to water content of the silty clay subject to tunnelling, a method combining laboratory tests, numerical simulations with field monitoring was developed in this study. A series of laboratory tests were performed to relate the deformation and strength parameters of the silty clay with water content. The silty clay has been sub-classified according to liquid index the mechanical parameters at different sub-classes were suggested. The parameters were used in numerical simulations for the determination of the optimum forepole spacing for tunnels in soil mass with different water contents. Field monitoring was performed to calibrate the water content-dependent deformation and strength parameters used in the numerical simulations. Numerical simulations were performed to obtain the ground surface settlement, crown settlement and steel rib axial stress for the cases without pre-support, and with forepores in different spacing. Finally, a scheme for the determining the optimum forepole spacing in relation to water content of the silty clay was obtained. In the scheme, for the silty clay with liquid limits in the range of 0.05–0.20, the tunnel could maintain stability without forepoles for the silty clay with liquid limits in the ranges of 0.20–0.45, and 0.45–0.8, the tunnel could maintain stable with forepoles in spacing of 0.8 m and 1.6 m, respectively. This scheme was used in both the phase III of Harbin Metro Line #1 and Harbin Metro Line #3. The practices proved that the scheme was applicable to the pre-support for safe and economic tunnelling in the low to medium plasticity silty clay for Harbin Metro construction.

Experimental Study on Sonic Vibration Grouting in Fine Silty Sand Layer

Fine silty sand layer is one of the common weak strata. It is easy to deform suddenly and induce accidents under the external load due to its loose structure and poor self-stability. To improve the stability of the strata in engineering construction, the grouting is usually used for antiseepage reinforcement in the fine silty sand layer. This paper presents the basic principle of the sonic vibration grouting, develops the experimental device and the simulated stratum condition, mixes the acidic water glass for engineering application, and carries out the experimental study on the sonic vibration grouting. The results show that the effect of the exciting force on the sonic vibration grouting is not obvious, and the vibration duration has a greater influence on it. With the increase of the vibration duration, the grouting diffusion distance is enlarging gradually and stabilizes eventually at a certain value. The vibration frequency has the greatest impact on the grouting. The grouting effect is the best when the vibration frequency is close to the natural frequency of the fine silty sand. The grouting diffusion distance is getting smaller, which means the grouting effect is becoming worse, when the vibration frequency is far away from the natural frequency of the stratum. The grouting effect in the fine silty sand layer can be improved effectively by vibration technology using the sonic vibration grouting which has excellent effect in engineering application. This paper lays a foundation for the further study on mechanism and engineering application of the sonic vibration grouting.

Theoretical and experimental research on the grout fronts diffusion considering filtration effect

Based on the seepage continuity equation, Darcy law, mass conservation equation, linear filtering law and pressure drop equation, the theoretical model of grout fronts diffusion was established. And through the model, the filtration mechanism of cement particles and the diffusion law of slurry fronts were analyzed. By applying the model test system developed independent, the dynamic variation law of the pressure of grout fronts is studied and compared with the theoretical value. The results show that, the permeability coefficient of the precipitated cement increases along the grout diffusion distance under the filtration effect. The change rate of frontal velocity is negatively correlated with the permeability coefficient of precipitated cement. At the specific diffusion distance, the frontal pressure drop p increases first and then decreases, while the frontal pressure p and the average unit pressure drop Δ P show the trend of decreasing first and then increasing. The deviation rate of frontal pressure value between theory and test is only from –10% to 26%, which reveal a high degree of coincidence. The conclusions can be used to guide the grouting design, which has certain application value to the practical engineering.

Double-parameter foundation beam modal of overlying thin rock stratum under loose layers grouting mining

Strata movement of drilling grouting is distinctly different from that of traditional caving mining, especially for overlying thin rock stratum. Considering the horizontal shear transfer of foundation, a mechanical model of overlying strata movement was established using the theory of Pasternak double-parameter foundation beam. The deflection and internal force equations of rock beam were derived, and the influence mechanisms of grouting material parameter were discussed. The results showed that the thickness of layer grouting was the key influential factor than the foundation modulus coefficient and grout diffusion radius. The comparison with the theory of Winkler elastic foundation beam also showed that double-parameter foundation beam method is more applicable to reinforced strata.

Grouting Diffusion Characteristics in Faults Considering the Interaction of Multiple Grouting

AbstractIn this study, a testing device was developed to analyze the characteristics of grouting diffusion in faults. To include the interaction of multiple grouting applications, tests consisting of four applications of grout were performed using three sets of grouting pipes. During the grouting process, the real-time injection pressure, injection rate, soil pressure, and seepage pressure were monitored. It was found that the curves of both injection pressure versus time and injection rate versus time showed a wavelike relationship. Soil pressure and seepage pressure showed an obvious response to grouting; both increased continuously during grouting and decreased gradually when grouting was stopped. To expose the diffusion of the grout, 23 sections were cut through the medium, and 2,197 sets of the coordinates and thicknesses of exposed grouting veins were collected. It was found that the grouting veins formed by the first and fourth groutings, respectively, had larger sizes and larger spans. Based on th...

Experimental investigation of pressure grouting in sand

Pressure grouting technology has been widely adopted in ground improvement and soil stabilization. To better understand the grout evolution and diffusion process upon pressure grouting injection in sand, laboratory-scale tests were carried out on loose sand under confined boundary conditions, with different grout water/cement (w/c) ratios (0.5 and 1) and soil degrees of saturation (ranging from 5% to 60%) taken into account. By comparing the injected grout volume, the grout bulb volume and density, and the characteristics of the grouted bulbs (dimension and shape) obtained at increasing grouting pressure, the main features of the pressure grouting process were revealed. The injected grout volume increased almost linearly with the grouting pressure, and a lower volume of grout could be injected for a lower w/c ratio at the same grouting pressure, representing a lower injectability. An increase in the grouting pressure leads to an enlarged grout bulb dimension for both w/c ratios, and this increase shifts the grout diffusion process from being dominated by compaction to one involving a fracture-like pattern. Generally, a spherical grout bulb is obtained at a lower w/c ratio of 0.5; however, at the higher w/c ratio of 1, fracture starts to occur even at a low grouting pressure of 100kPa and continues to propagate as the grouting pressure increases. The influence of the degree of saturation of the soil was significant on both the injectability and the characteristics of the grout bulbs, since the cohesion of the unsaturated sand changed along with it. When Sr exceeds 5%, the volume of the injected grout decreases, but then increases after a threshold value of approximately 40%. Conversely, compaction grouting seems to be dominant at the threshold Sr value, while fractures tend to appear at both lower and higher degrees of saturation. A considerable amount of bleeding occurred with the two main diffusion processes during pressure grouting. The w/c ratio seems to be the most significant factor contributing to this behavior in sand samples.

Grout and Anchor Coupling Support in Dynamic Pressure Impact Roadway with Large Deformation in Deep

The broken characters of roadway in deep in China were statistical analyzed. Taking unit length anchor body as studying element, interrelations of the maximum shear force max、cementation strength and confining pressures were analyzed, researched and development grouting cable, put forward grouting-anchor coupling support for surrounding rock control in deep. The relation between different water cement ratios (0.5:1-1:1), different grout pressures (0.5:1-1:1) and diffusion radius were analyzed by means of numerical software UDEC. The surrounding rock controlling problems of dynamic pressure impact and large deformation roadway in deep was solved in CHANGCUN mine of Lu’an coal mining area in China.

Study on Model of Back-Filled Grouting of Shield Tunnel

Basing on the theory of maag cylindrical diffusion, back grout diffusion radius and grouting pressure formula of shield tunnel were derived in two cases of the viscosity time-dependent behavior or not.The distribution law of diffusion radius and the pressure to segments were obtained by applicating the spreading model in some project.The results show that grout diffusion radius and grouting pressure both increase with the increasing of grouting time and grouting pressure whether considering the viscosity time-dependent behavior or not.In the same grouting time (pressure),the calculated values that unconsidering the viscosity time-dependent behavior are bigger than the values of considering.

The Grouting Diffusion Model of Power-Law Fluid in Single Fracture

Based on the Hele-Shaw smooth flat model, the theoretical model of the diffusion radius-time relationship of the power-law fluid in single fracture plate model can be deduced according to the force balance of fluid micro element in cylindrical coordinate, the rheological equation of power-law fluid and the equation of mass conservation. The calculation procedures of the derived theoretical model are compiled by applying the Matlab software, and are employed to analyze the affecting elements of diffusion. The results show that the slurry diffusion radius is widened with the increase of the fracture apertures, the grouting pressure difference and the grouting time; and the bigger the water cement ratio, the easier the grouting spreads under the equivalent fracture opening conditions. The grouting infection efficiency in the early stage is much higher than that of the later stage, and reduces with the increase of the diffusion radius, which is in accord with the rule of the grouting in practice. The Grouting Diffusion Model will serve as a theoretical basis for the cement grout with low water cement ration in the fractured rock.

Chemical grout diffusion in porous rock based on response of geoelectric field

Porous rock chemical grouting simulation test was conducted using established large scale physical model. Chemical grout diffusing rule in porous media with different permeability was studied by monitoring the spontaneous potential and exciting current response during grouting. The results show that chemical grout spread evenly in all directions and diffusion areas are approximately concentric circles in the cross section of homogeneous transverse isotropic pore medium, the grout spread filling range can be quantitatively decrypted by the diffusion radius. The average diffusion speed and radius increase approximately as the square root with the permeability coefficient in different permeability media under the same conditions. Calculation results using Maag cylindrical diffusion equation show that the calculated value of diffusion radius is in good agreement with the test value under different grouting pressures and permeability conditions.

An in situ low-pressure grouting application

This study examined the effects of low-pressure grouting on soil properties at a site that is at risk of soil liquefaction. The study was conducted at a 96 m2 site located in Yalova, Turkey, that is considered a first-degree seismic zone. Compaction grout was injected into a silty sand layer at 100 kPa and 150 kPa pressure at three different points at depths of up to 9 m. Standard penetration tests, cone penetration tests and seismic refraction tests were conducted before and after the grouting, to determine the effect of grouting on the soil properties in the field. Grout injection holes were drilled at a spacing of 1·25–3·0 m. Grout injection was observed to be impossible in wells that were spaced closer than 1·50 m, because of the diffusion of grout from primary injections. The injected grout volume was calculated to be 5% of the total soil volume. The results from the tests indicate that the bearing capacity of the soil increased by approximately 50%, and the safety factor with respect to liquefaction increased by a factor of up to 100%.

Research on Multiple Holes Grouting of Fractured Rock Mass

Considering the seepage stress coupling of fractured rock mass, the multiple holes grouting problems were simulated to analyse the spread regularity by Universal Distinct Element Code(UDEC).The results show that the correlation between grouting pressure and the diffusion distance is positive, whereas the correlation between ground stress and diffusion distance is negative; With the raising of grouting holes, the diffusion distance is increasing and becoming more uniform in all directions, and the grout pressure and saturation is falling and attenuation amplitude is decreasing along the direction of grout diffusion; With the increasing of fracture aperture, the grout diffusion distance is increasing, and the grout pressure and saturation attenuation amplitude is decreasing along the direction of grout diffusion.

The Calculation of Grouting Diffusion Radius on Based Bingham Fluid for Chunnel That Passes through Fractured Rock Mass

To conduct pro-grouting design and make the prediction of the result of grouting about the chunnel that passes through fractured rock mass, the essay adopts following theoretical formula to calculate the fractured rock mass grouting diffusion radius: Wittke and Wallner Formula、Lombadi Formula and Huang Chunhua Formula. Finally through the analysis of calculation results can conclude: (I) The diffusion radius of the slurry can meet the design requirements under the condition of 3-4 Mpa designed grouting pressure、5 cm grouting holes’ radius and 1800-3600s grouting time. (II) The calculation result of Huang Chunhua Formula is almost the same as Wittke and Wallner Formula and Lombadi Formula, but the margin of grouting diffusion radius’ change as grouting time and grouting pressure growing are different, it’s more close to the real situation.(III) The calculation of these theoretical formula only consider the breadth of fractured rock without considering the variation of its thickness and direction. So all of the calculation results of these formula are generally bigger than the standard.

Study on Chemical Grout Permeation Mechanism Based on Experiment of Mud and Sand Medium

In order to fully mechanized caving face bypass collapse column on safety and high efficiency, this paper do similarity simulation experiment, and obtained experimental result that main type of seepage flow includes finger seepage and surface seepage, the grout enter into around pore and occupy it’s space in grouting pressure. Moisture content of mud and sand medium is lower, grouting process can be regarded as single-phase permeability, analysis on the relation between grouting diffusion radius and other parameters. may know that grouting diffusion radius is increased with the increase of permeability coefficient and grouting pressure and grouting time, and is decreased with the increase of Porosity and grout viscosity.

Grout diffusion characteristics during chemical grouting in a deep water-bearing sand layer

The deep, loose bottom aquifer of the eastern air shaft in the Xinglongzhuang Coal Mine was used to develop an experimental model of shaft grouting through Model deep soil. Lab experiments using chemical grouting were done to study the grout. The grouted soil shapes and osmotic pressure were measured during the experiments. The tested characteristics of the grouted soil show that the diffusion mode of grout in saturated sandy soil is a combination of split compaction and osmosis. More specifically, the shape of the grouted soil is determined by split compaction while the size of the grouted soil shape is determined by osmosis. Sensor test results indicate that the main reason for the non-uniform grout diffusion is the anisotropic osmotic pressure field surrounding the grouting holes.

Study on Grout Permeation Model of an Equipment for Grouting in Roller Compacted Concrete

Based on cylindrical diffusion theory and characteristics of enriched vibrated Roller Compacted Concrete (RCC), a model of grout permeation was established. According to this model and generalized Darcy’s law, a formula was deduced, which shows the relationship among diffusion radius of grout, grouting pressure, radius of grouting pipe, construction time, viscosity of grout, permeability coefficient of RCC, porosity of RCC and rheological index of grout, computing steps by this formula were presented, and results of computing grout diffusion radius for an equipment of grouting in Roller Compacted Concrete was given, which was developed for construction of RCC dam at Tingzikou hydraulic power station.

Uniform Design and its Application in Grouting Simulation Experiment

The uniform design is a new design method for investigating the experiment with many factors and levels, which can get enough experiment information with less experiment times. The advantages of uniform design are introduced in the paper, it can seek experimental points to be uniformly scattered in the experimental domain, which reduce experiment times greatly and get good experiment results. The new polymeric grouting experiment is designed by uniform design and the experiment data has been studied by regression analysis. It is proved that distinct influencing factor on grout diffusion radius are grouting pressure and permeability, but the influences of grouting time and grout temperature are smaller, their relation has been obtained through regression analysis, uniform design is efficient and credible method of experimental design by the experiment results.