Grout Slurry Research Articles

Effects of a polycarboxylate superplasticizer and temperature on the rheological properties of grout blended with seawater

A series of subsea tunnel projects with unprecedented scale is under vigorous construction. In the construction sector, grouting has been widely adopted as the primary method for disaster control, and superplasticizers are the additives commonly used in grouting engineering. However, during grouting, seawater intrusion and ambient temperature change lead to significant changes in the rheological properties of grouting materials and failure of the grouting scheme. Therefore, it is critical to study the rheological properties of seawater-mixed grout slurry containing a polycarboxylate superplasticizer (PCS) at different temperatures. In this study, the mechanism of a PCS and its effects on the rheological properties of biomass-activated grouts (BAGs) blended with seawater were revealed for the first time. Further, the rheological characteristics and constitutive equations of seawater-mixed grout slurry at 0–30 °C were determined. Results indicated that the PCS significantly reduced the shear stress and viscosity of seawater-mixed grout. The fluidity of grout slurry with 0.8 % PCS increased by 30.8 %. The power law model was applied to describe the rheological characteristics of seawater-mixed slurry with varying PCS contents. With increasing temperature, the rheological index increased, whereas the viscosity, shear stress, and consistency coefficient decreased. The constitutive equation of seawater-mixed BAGs containing 0.8 % PCS at different temperatures was also established for the first time. The findings of this study can provide a basis for grouting diffusion theory, numerical calculation, and the design of a grouting scheme for subsea tunnels at different temperatures.

Application and Prospect of Curtain Grouting Technology in Mine Water Safety Management in China: A Review

In China, mine curtain grouting has become an important technology to ensure the safe and efficient mining of deep mineral resources and protect regional groundwater resources after more than 60 years of development and improvement. This review paper summarizes and analyzes four aspects of the current situation of curtain grouting technology in deep underground mines: curtain construction conditions, theoretical design and effects, drilling structures, and grouting materials’ research and development. In addition, several main problems of curtain grouting technology in deep underground mines are analyzed: planning and construction lag behind; the theory of mine curtain grouting is not mature enough; the investigation into the mechanism of consolidation and deterioration of grout slurry under long-term high pressure is insufficient; there is a lack of research on the long-term effectiveness of monitoring and evaluation, so precise drilling control technology needs further breakthroughs. In addition, the development directions of this technology are put forward from three aspects: precise directional drilling technology; the consolidation mechanism and durability of slurry under multi-field coupling conditions; and long-term dynamic monitoring, evaluation, and early warning for grouting curtain effectiveness. In the future, mine curtain grouting will become an important mine geological guarantee technology for safety, efficiency, accurate, sustainability, and green mining of the Earth’s deep resources.

Research and evaluation on Water-dispersion resistance of synchronous grouting slurry in shield tunnel

When the shield tunnel passes through the watered stratum with high permeability, as the shield tail interspace prone to be filled with groundwater, resulting in the segregation and loss of ordinary grout slurry during synchronous grouting, then critically affect the physical and mechanical properties as well as the durability of the curing grouting ring. Hence, it is necessary to optimize the performance of the existing ordinary grouting slurry to improve its water-dispersion resistance on the premise of ensuring the original performance. By means of theoretical analysis and indoor tests, this paper systematically investigates the mechanism of water-dispersion resistance of synchronous grouting slurry in water-rich stratum with high permeability, establishing a set of testing process and detection method for water-dispersion resistance of synchronous grouting. Moreover, the influences of different flocculants with corresponding contents on the performance of synchronous grouting slurry have been revealed, and the evaluation criterion of water-dispersion resistance of synchronous grouting slurry in shield tunnel is also clarified. The results show that: 1) Turbidity has notable responses to the change of flocculant content, which could better reflect the clarity of water samples. So, the turbidity is considered as a main evaluation index of water-dispersion resistance of synchronous grouting; 2) On the other hand, pH and water-land strength ratio also demonstrates the acid-base changes of groundwater and the loss of cementitious materials respectively during grouting. Thus, the two indexes are applied as auxiliary evaluation indexes for water-dispersion resistance of synchronous grouting; 3) For the above evaluation indexes, corresponding critical values to satisfy the water-dispersion resistance of synchronous grouting slurry are ensured: turbidity < 100NTU, pH < 10, and water–air strength ratio at different curing ages greater than 80%.

Reducing settlement of soft clay using different grouting materials

Abstract Different injection material types were tried in the injection of soft clay, such as lime (L), silica fume (SF), and leycobond-h (LH). In this study, experiments were made to study the effect of injection on soft clay consolidation settlement. A sample of natural soft clayey soil was investigated in the laboratory and the sample was injected with each of the grout materials used, L, SF, L + SF, and L + SF + LH. A 20 cm3 of each slurry grout was conducted into the soil, which was compacted in California Bearing Ratio (CBR) mold and cured for 7 days, and then the sample was loaded to 80 N load by a circular steel footing 60 mm in diameter. The settlement was recorded. The sample of each slurry grout, which provided minimum settlement, was chosen (L + SF + LH). To reduce soft clay settlement before and after footing construction, four cases were investigated. The impact of injection hole spacing and grout depth was studied. It was discovered that injecting a slurry of (L + SF + LH) into the soft clay beneath or surrounding the footing increased bearing capacity by 5–88%. Due to the shape of shear failure of the soft clay around the footing, grouting near the footing at a distance of 0.5 diameter of the footing is more effective than grouting at a distance of 1.0 diameter of the footing, and grouting near the footing at a distance of 0.5 diameter of the footing is more effective than grouting at a distance of 1.0 diameter of the footing.

Real-time characterization of the grouting diffusion process in fractured sandstone based on the low-field nuclear magnetic resonance technique

Investigations of the flow and diffusion mechanism of grout slurry in underground fractured rock mass are of critical significance to guarantee the grouting reinforcement of deep soft rock tunnel and to ensure the construction safety. This paper reports a series of permeation grouting tests in fractured sandstone samples based on the low-field nuclear magnetic resonance (LF-NMR) technique. During the grouting process, the NMR signal characteristics of the grout were monitored in real-time, and the parameters such as the slurry injection volume, effective grouting time and grout filling speed were comprehensively analyzed under various temperatures, confining pressures, flow velocities and numbers of fractures. The results show that the final injection amount of the grout decreases with increasing temperature and confining pressure. The effective grouting time is inversely proportional to the flow velocity, while it is positively related to the temperature. The filling speed decreases with increasing the temperature and confining pressure, while it increases with increasing the grout flow velocity. Compared to the single fractured sample, the sample with more fractures is injected with more grout slurry in a shorter effective grouting time and a higher filling speed. Under the conditions of high confining pressure (e.g., 15 MPa) or high flow velocity (e.g., ≥5 ml/min), the grout slurry preferentially transports into the micropores, and then the mesopores and macropores. However, the temperature and number of fractures have equal effects on the grout flow and diffusion in the three types of pores. The grouting filling performance becomes worse when the temperature and confining pressure are higher. The findings in this study provide meaningful guidance for the grouting reinforcement of deep soft rock tunnel.

Fractal-based model for maximum penetration distance of grout slurry flowing through soils with different dry densities

Existing penetration models for grouting slurry seldomly consider the relationship between dry density and complexity of soil. A novel penetration model, in which the complexity of the flow path in soil was described by fractal theory, has been proposed for quantifying the maximum penetration distance of grout slurry flowing through soils with different dry densities. The relationship among dry density, fractal dimension and fractal tortuosity of flow path was identified by SEM analysis, showing that fractal tortuosity increases but fractal dimension is almost unchanged with increase of dry density. The results calculated by the penetration model were validated against experimental results for different soils under various pump pressures and volume flow rates. The analysis results show that the grout slurry tends to penetrate to a long distance under high pump pressure, low flow rate, low consistency factor and low fluidity index. High dry density and small average particle size of soil reduce the penetration distance. The proposed model is helpful to achieve a better design in soil ground stabilization via grouting.

Physical test of fracture development in the overburden strata above the goaf and diffusion process of permeable grout slurry

The massive mechanized and irrational coal mining has generated many goafs (i.e., mined-out areas) in China. To manage these goafs effectively, grouting technique has been commonly used to fill the fractures in the overburden strata. However, little is known about the development and distribution of fractures in the overburden strata above the goaf. The lab-scale simulation of fracture development, as well as the grouting process, can provide valuable information for managing a real goaf by the grouting technique. Based on the mechanical properties of rocks and soils in the goaf of Kangjiagou coal mine in Shanxi Province, an experimental system was designed to simulate the development of fractures in the overburden strata above the goaf and study the diffusion behaviors of the grout slurry under different conditions (such as grout volume, grouting pressure, porosity, and water-solid ratio). The physical model test showed that more fractures were found in the fractured and caved zones, with fracture porosity ranging from 15.05 to 40.79%. The grouting experiment showed that, when the water-solid ratio was smaller than 1.15 and the grouting pressure was lower than 0.3 MPa, the changes in diffusion radius were stable during the grouting process. To maintain the stable changes in diffusion radius and reach a high filling ratio, the grouting pressure should be controlled in the range of 0.2–0.4 MPa at the porosity of 24.8% and 0.5 MPa at the porosity of 35.1%. The findings derived from this study are widely applicable under real engineering contexts.

Study to Assess the Behaviour of Cement Grouted Bituminous Mix Prepared Using Pozzolanic Grouting Material

Cement grouted bituminous mix (CGBM) is a composite mixture where cementitious grout slurry is penetrated within the air voids of an Open-graded bituminous mix (OGBM). The CGBM surface has both flexible and rigid pavement merits and is considered a semi-flexible pavement type. Further, the choice of cold mix layer of CGBM also minimises the challenges associated with conventional hot mix types. In the present study, cementitious grout slurry is prepared using cement, fly ash, silica fume, and polycarboxylic ether-based superplasticiser to make the CGBM samples. To study the effect of grouting, the prepared CGBM samples were tested in the laboratory at 1, 3, 7 and 28 days after the curing period. Compressive strength, Marshall stability, indirect tensile strength, and resistance against the CGBM mix's moisture damage, improve with the increase in the curing period. CGBM mixes are less temperature susceptible and exhibit better resistance against moisture damage and abrasion loss. A trial section is constructed as per the design developed in the laboratory. The paved CGBM surface's field performance reveals that grout material is significantly improving the CGBM mix's behaviour. The evaluation of CGBM is considerably beyond the defined criterion in the Indian standards code, i.e. MoRTH (Ministry of Road Transport and Highways) fifth revision. Results and analysis presented in this manuscript may help the engineers to analyse the CGBM layer further.

Application of grout slurries with the defecate addition for effective well cementing

Purpose. Research and substantiating the expediency of cement mix formulations of grout slurries with different Defecate additive content and their effective use when cementing the reservoirs prone to absorption of the cement slurry, as well as to prevent behind-the-casing flows and for cementing operations in the zone of abnormal pressures (hydraulic seam fracturing). Methods. Analytical and experimental studies of the physical-chemical grout slurry properties are used: determining the influence of the Defecate additive content on the cement mixture technological properties; study of a change in the grout slurry rheological characteristics at various temperature conditions; testing the formulation of grout slurry with different rates of strength development; substantiating the economic efficiency of using the grout mixtures with the Defecate additive. Findings. It has been revealed that the cement mixture fluidity increases by 10-20% with the addition of a Defecate in the proportion of 5-20%. With a further increase in the Defecate content, the stone strength deteriorates, and with a decrease, the grout slurry concentration increases. It has been found that when Defecate is added to the cement mixture in a proportion of 20%, the pumpability of the cement slurry doubles, that is, from 1.5 to 3 hours. The economic efficiency has been proved of using these mixtures during insulating activities in the well No. 122 of the Kulychykhynske NHKR (oil and gas condensate field). The improved formulations of grout slurry with the addition of a Defecate are recommended to be used during repair-insulation works for delimitation of producing reservoirs prone to absorption, behind-the-casing flows and hydraulic fracturing. Originality.New dependences have been determined of the technological and rheological characteristics of grout slurries on the content of the Defecate additive, which makes it possible to set its optimal proportion. Practical implications. The use of grout mixture based on the Defecate will expand the raw material base for obtaining lightweight grout slurries. The properties of such a solution make it possible to use a grout mixture for cementing wells in the zone of abnormal pressures, while reducing the costs for the process of reservoir delimitation. Keywords: well, behind-the-casing flows, producing reservoir, grout slurry, Defecate

Increasing the efficiency of water shut-off in oil wells using sodium silicate

Purpose. Substantiation of technology for creation of a water-blocking zone below an oil reservoir and calculation of the proper composition of a gel-forming compound based on sodium silicate, in order to reduce water cut in production wells. Methodology. The goal of the work was achieved by conducting theoretical and experimental studies on technological processes of water blocking in an oil reservoir, and by identifying patterns of gel formation of sodium silicate and hydration of a micro-cement solution in reservoir conditions on full-scale models. The gel compound included sodium silicate (Na2SiO3, also referred to as liquid glass) and an aluminum salt cross-linker (AS-1). The plugging material mixture of Portland micro-cement and sodium silicate contained calcium oxide, to allow expansion, and a GL-1 reaction inhibitor. The criteria for assessing the creation of a reliable water-blocking zone in an oil reservoir are: the mobility of the aqueous solution of the gel-forming compound during its movement from the wellhead to the bottom of the well, the low permeability of the zone following its creation, and the sufficient strength of the non-shrink micro-cement in the annulus of the well. Findings. A new technology is suggested used to create a water isolation zone is a gel-forming compound based on sodium silicate, which provides a significant reduction of water cut in oil production. It is found that perforation of production string below the oil reservoir at the level of the water-saturated zone followed by injection into a well through perforated channels, the mixture of fresh water and the gel-forming compound prevents water inflow to the bottom of the well. Experiments established that with a gelation time of 2 hours at a temperature of 80 C, the viscosity of the gel is in the range of 1.22.9 Pas, and the density is 10801109 kg/m3. These values for the viscosity of the gel allow transportation from the top of the well to the bottom with the least resistance to motion. Following gelation time, the viscosity increases significantly, and after 3 days the gel viscosity reaches a range of 3.46.7 Pas. The values indicated for the viscosity of the gel are much greater than those of oil. Therefore, the proposed gel-forming compound provides a reliable water shut-off zone at the bottom of an oil reservoir, and prevents the influx of water at the bottom of a well. Originality. The proposed sodium silicate compound allows for the creation of a reliable water shut-off zone and an enhanced grouting material, based on the combination of sodium silicate and micro-cement, which together provide a significant reduction in water cut in wells during oil production. Practical value. A method for studying technological processes of oil reservoir water-blocking has been devised and the rational composition of gel-forming compound and micro-cement grout slurry with an expanding additive and a reaction retarder in reservoir conditions on full-scale models has been established. The application of the research results in oil fields allows reduction of water cut in production wells to 010%, against existing values of 7090%, and an increase in flow rate in producing wells by 2030%.

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.

Shear stress limit, rheological properties and compressive strength of cement-based grout modified with polymers

Grouting is a comprehensive technology used in the construction projects due to the rapid development of sub-surface urban infrastructures, the main reasons for grouting soils are strengthened the cohesion-less soils and increasing the shear stress (pure shear) of the grouted soils. Providing high flowability with high viscosity for the cement-based grout in the liquid stage (slurry) and high compressive strength of the cement-based grout in the hardened stage are significant challenges. In this study, the impact of two types of water reducer [polycarboxylate (PCE)] polymer on the rheological properties with the ultimate shear strength and compressive strength of cement-based grout with water-cement ratios (w/c) of 0.6 and 1.0 at two different temperatures 25 °C and 50 °C were studied. XRD and TGA were used to analysis the cement, polymers, and cement modified with polymers. The behavior of cement-based grout in the liquid phase (slurry) and hardened phase modified with different percentages of polymer up to 0.16% (by dry weight of cement) were investigated. The compressive strength of cement-based grout modified with polymer was tested from the young age up to 28 days of curing. Vipulanandan rheological model was used to predict the shear stress-shear strain behavior of cement-based grout slurry and compared to the Herschel–Bulkley (HB) model. The rheological and the compressive strength are increased with increasing the of PCE content. The polymer modification increased the yield stress, apparent viscosity and plastic viscosity of the cement grout by 19–136%, 32–319% and 58–367%, respectively based on the types of polymer, polymer content, w/c, and temperature. The compressive strength of the cement-based grout increased by 94–786% based on the types of polymer, polymer content, w/c and curing time. Increasing the temperature of cement-based grout slurry to 50 °C increased the maximum shear stresses by 110% and 107%, respectively. Effects of polymer content, w/c, curing time and the temperature of the plastic and hardened properties of cement-grout were modeled using a multiple nonlinear regression analysis.

TGA, rheological properties with maximum shear stress and compressive strength of cement-based grout modified with polycarboxylate polymers

Grouting is a comprehensive technology used in the construction projects due to the rapid development of sub-surface urban infrastructures, the main reasons for grouting soils are strengthened the cohesion less soils and increasing the shear stress (pure shear) of the grouted soils. Providing high flowability with high viscosity for the cement-based grout in the liquid stage (slurry) and high compressive strength of the cement-based grout in the hardened stage are significant challenges. In this study, the impact of two types of polycarboxylate (PCE) polymer on the rheological properties with the ultimate shear strength and compressive strength of cement-based grout with water-cement ratios (w/c) of 0.6 and 1.0 at two different temperatures 25 °C and 50 °C were studied. XRD and TGA were used to analysis the cement, polymers, and cement modified with polymers. The behavior of cement-based grout in the liquid phase (slurry) and hardened phase modified with different percentages of polymer up to 0.16% (by dry weight of cement) were investigated. The compressive strength of cement-based grout modified with polymer was tested from the young age up to 28 days of curing. Vipulanandan rheological model was used to predict the shear stress-shear strain behavior of cement-based grout slurry and compared to the Herschel-Bulkley (HB) model. The rheological and the compressive strength are increased with increasing the of PCE content. The polymer modification increased the yield stress, apparent viscosity, and plastic viscosity by 19–136%, 32–319% and 58–367%, respectively based on the types of polymer, polymer content, w/c, and temperature. The compressive strength of the cement-based grout increased by 94–786% based on the types of polymer, polymer content, w/c, and curing time. Based on the Vipulanandan rheological model, increasing the temperature of cement-based grout slurry to 50 °C increased the maximum shear stresses by 110% and 107% respectively. The unprecedented conclusions can be drawn in this study, which is the effect of the polymer content, water-cement-ratio and temperature effect on the plastic viscosity, yield points and shear stress limit in the fresh stage (slurry) of the cement-based grout and also, the impact of the polymer content, water-cement-ratio and curing time on the flexural with compressive strengths in the hardened stages of the cement modified with polymers were modeled.

Investigation of critical hydraulic gradient and its application to the design and construction of bentonite-grout curtain

The application of salt–bentonite (Salt–Bent) grouting for the design and construction of grout curtain to form vertical barriers (VB) to serve as seepage remediation measures has been investigated. Recent experiences on the high cost of grout injection materials when conducting a grouting campaign have necessitated the authors to consider the use of clay of the montmorillonite (Mt) type (Wyoming bentonite), which is less expensive; readily available naturally occurring; yet very effective and environmentally friendly grouting material for the construction of grout curtain. Grout curtain is formed by injecting grout slurry into a series of boreholes, drilled through the weathered zone of the subsurface, to form VB. Vertical barriers play a significant role in geo-environmental engineering for the control of horizontal groundwater flow and contaminant spread into the unsaturated–saturated zone of the subsurface. The design and construction of effective grout curtain is key to the overall performance of the barrier and this is dependent on the accurate determination of a design parameter, the critical hydraulic gradient (CHG). A laboratory investigation of the CHG was conducted through grout injection into fractures of aperture sizes 100–60 µm and river sand compacted to different porosities (0.33 ≤ n ≤ 0.40), to determine the safety thickness of a bentonite-grout curtain to withstand a given hydraulic gradient without failure. The study finds that, the CHG due to the fractured and porous media ranges between 30 and 35; and 180 and 200, respectively. The resulting permeability values obtained from the grouted samples were in the order of 10−7cm/s or less. It can be inferred from the results that, bentonite-grouting can provide the required permeability for an effective barrier. The results also suggest that, accurate determination of the safety thickness of the barrier is of great importance for sustainable barrier system.

Performance of typical cement suspension-sodium silicate double slurry grout

To plug dynamic water effectively during underground constructions, it is important and urgent to determine the performance of quick-setting cementitious grouts. In this study, the Ordinary Portland cement (OPC) and sulphate aluminium cement (SAC) were selected as two typical cements, and the double slurry were prepared with cement suspension and sodium silicate slurry. The fresh-state properties of cement single slurry i.e., mini-slump, flowability and bleeding; basic work performance of double slurry i.e., flowability losing time, anti-washout and initial or final setting time; flexural and compressive strengths; failure mode; brittleness evaluation and microstructure of the double slurry grout were studied. The water/cement (W/C) ratio was selected as 0.6:1–1.2:1. The volume ratios of cement slurry and sodium silicate were 1:1, 2:1, 3:1 and 5:1. The results show that the sodium silicate slurry disturbed and accelerated the normal hydration process of cementitious minerals, and the SAC was not suitable for preparing double slurry compared with OPC. The flowability losing times of SAC double slurry were higher than those of OPC double slurry. The anti-washout, failure modes of OPC double slurry have more advantages. Considering the flowability losing time, controllability, pumpability, diffusibility, mechanical strength, failure mode and microstructure, the volume ratios should not be over 5:1 and not be less than 2:1.

Simulation of coupled hydro-mechanical interactions during grouting process in fractured media based on the combined finite-discrete element method

Fracture grouting is one of the most widely used methodologies to reduce the hydraulic conductivity and enhance the strength of rock masses in geotechnical engineering (e.g., mining, civil engineering and hydraulic engineering). Understanding and controlling the migration process of grout slurry are critical to optimize the grouting process. In this paper, a grouting process simulator is generated for hydro-mechanical (HM) coupling grouting problems, linking the combined finite-discrete element method (FDEM) and a grouting flow simulator, called as FDEM-grouting. The initiation and propagation of fractures as well as the deformation of solid mass are solved by the FDEM. Meanwhile, the grout flow in fractures is modeled based on the principle of the parallel-plate model. This FDEM-grouting can consider the HM coupling effect, the stress-induced fracture aperture variation, the fracture networks evolution and the hardening of grout during the grouting process, which are rarely considered in previous studies. The present FDEM-grouting is validated by intensive numerical tests. Then, several influence factors of grout penetration are discussed. Lastly, we investigate a fracture grouting process with considering the effect of in-situ stress and the interference between grouting holes. Results show that this FDEM-grouting is potentially useful to optimize the fracture grouting process.

Large-scale test of sleeve valve pipe grouted overwet subgrades

Due to the intense capillarity action on low-liquid limit silt subgrade, the subgrade is often overwet. The technology of sleeve valve pipe grouting is an effective reinforcement method of the overwet subgrade. However, there are limited studies on the reinforcement mechanism and its effects. In this study, four large-scale subgrade models were set up. Distributions of moisture content and physical mechanical indexes of soil in different silt subgrades were analysed. Integral stiffness and deformation characteristics of the subgrades were studied by cyclic step loading tests. The subgrade models were excavated after tests to see the spreading pattern of the grout slurry. The reinforcement mechanism of the sleeve valve pipe grouting was analysed based on Vesic's cavity expansion theory. The results indicate that the integral stiffness and stability of the subgrade decrease due to the capillary action. The vertical plastic deformation of the wet subgrade rapidly increases with the increase in vehicle load. Sleeve valve pipe grouting produces bottom-expanded micropiles, and also horizontal reinforcement layers, which can block the capillary water from rising and form a space frame with the bottom-expanded micropiles to bear the load with the soil together. This increases the subgrade stability, and the reinforcing effect is more significant than with the traditional grouting technology.

The differences between soil grouting with cement slurry and cement-water glass slurry

Cement slurry and cement-water glass slurry are the most widely applied for soil grouting reinforcement project. The viscosity change of cement slurry is negligible during grouting period and presumed to be time-independent while the viscosity of cement-water glass slurry increases with time quickly and is presumed to be time-dependent. Due to the significantly rheology differences between them, the grouting quality and the increasing characteristics of grouting parameters may be different, such as grouting pressure, grouting surrounding rock pressure, i.e., the change of surrounding rock pressure deduced by grouting pressure. Those are main factors for grouting design. In this paper, a large-scale 3D grouting simulation device was developed to simulate the surrounding curtain grouting for a tunnel. Two series of surrounding curtain grouting experiments under different geo-stress of 100 kPa, 150 kPa and 200 kPa were performed. The overload test on tunnel was performed to evaluate grouting effect of all surrounding curtain grouting experiments. In the present results, before 240 seconds, the grouting pressure increases slowly for both slurries; after 240 seconds the increase rate of grouting pressure for cement-water glass slurry increases quickly while that for cement slurry remains roughly constant. The increasing trend of grouting pressure for cement-water glass is similar to its viscosity. The setting time of cement-water glass slurry obtained from laboratory test is less than that in practical grouting where grout slurry solidifies in soil. The grouting effect of cement-water glass slurry is better than that of cement slurry and the grouting quality decreases with initial pressure.

Comparative Study of Soil Grouting with Cement Slurry and Cement‐Sodium Silicate Slurry

Cement slurry and cement‐sodium silicate slurry are most widely applied for soil grouting reinforcement project. The viscosity change of cement slurry is negligible during grouting period and presumed to be time independent, while the viscosity of cement‐sodium silicate slurry increases with time quickly and is presumed to be time dependent. Due to the significant rheological differences between them, the grouting quality and the increasing characteristics of grouting parameters may be different. Those are main factors for grouting design. In this paper, a large‐scale 3D grouting simulation device was developed to simulate the surrounding curtain grouting for a tunnel. Two series of surrounding curtain grouting experiments under different initial pressures of 100 kPa, 150 kPa, and 200 kPa were performed. The overload test on the tunnel was performed to evaluate the grouting quality of all surrounding curtain grouting experiments. The results show that the increasing trend of grouting pressure for cement‐sodium silicate is similar to its viscosity; the setting time of cement‐sodium silicate slurry obtained from the laboratory test is less than that in the practical grouting environment where grout slurry solidifies in soil; the grouting quality of cement‐sodium silicate slurry is better than cement slurry, and the grouting quality decreases with initial pressure.

Effect of Glass Powder Added Grout for Deep Mixing of Marginal Sand with Clay

The deep mixing has recently become a popular technique for improvement of weak or problematic soils in order to increase bearing capacity and reduce settlement. Despite various successful applications in construction projects, specifically improvement of marginal sand (i.e., loose poorly graded sand) using new materials in the viewpoint of strength development is still open for the attempt of deep mixing regarding the binder of grout, curing time and clay content. Thus, in this paper, effect of glass powder added to cement-based slurry grout in different proportions (0, 3, 6, 9% by dry weight of binder) has been experimentally investigated for deep mixing of marginal sand with various clay contents (4, 8, 20%). An experimental program has been developed for this purpose conducting the Vicat, unconfined compressive strength (UCS) and ultrasonic pulse velocity (UPV) tests for the performances of soilcrete samples. From the testing results, it is found that: (i) The glass powder is not able to accelerate the setting times of grout, (ii) the bulk density does not significantly change with the glass powder, clay content and curing time, (iii) the most performed UCS value is obtained due to the addition of 3% glass powder at the 28-day curing for the soilcrete samples of 20% clay content of sand, while all UCS magnitudes obtained for the soilcrete samples are considered acceptable for the construction of soil–cement column, (iv) the elastic modulus correlates well with the UCS values (R $$\ge $$ 0.83) at the majority of soilcrete samples and (v) the UPV values of soilcrete samples at 28-day curing perform better due to the addition of 3% glass powder similar to the response trend of UCS, while their performances are higher due to 4% clay content in contrast to the trend of UCS. As a consequence, this study demonstrates the use of glass powder added grout to be beneficial for deep mixing of marginal sand, in which 20% clay inclusion contributes more.