Grouting Reinforcement Effect Research Articles

Experimental Study on Grouting Reinforcement Mechanism of Heterogeneous Fractured Rock and Soil Mass

To explore the grouting reinforcement mechanism of heterogeneous rock and soil in a fault fracture zone, based on the F2 fault grouting project of Yonglian Tunnel, the filling area composed of loose and soft media in the fault is defined as the advantageous grouting diffusion region, which is divided into loose and weak diffusion regions according to the slurry diffusion form. A self-developed grouting reinforcement test system is used to carry out grouting reinforcement tests on the heterogeneous rock and soil. The existence of the advantageous diffusion region can effectively improve the reinforced body strength. The slurry in the reinforced body containing the loose medium mainly expands outwards in the form of first infiltration and then compaction, and the slurry vein mainly remains in the advantageous diffusion region. The slurry in the reinforced body containing the soft medium mainly diffuses in the form of compaction splitting, which can form thicker splitting of the grouting veins. When the reinforced body is destroyed, the body containing the loose medium is mostly conically fractured, indicating complete lithology and homogeneous material. Moreover, the reinforced body containing the soft medium always forms a penetrating crack along the slurry vein or near the grouting vein. Focusing on the heterogeneous stratum consisting of fault breccia and soft plastic fault gouge, controllable slurry dynamic adjustment, same-hole multi-sequence sub-gradient grouting, and localized grouting control are proposed. The grouting control method is applied to the case of Yonglian Tunnel, and a superior grouting reinforcement effect is achieved.

Research on Influence of Water‐Cement Ratio on Reinforcement Effect for Permeation Grouting in Sand Layer

In order to study permeation grouting reinforcement effect in the sand layer, a set of grouting test device is developed, which consists of a power device, a pressure‐bearing slurry tank, and several test frames. Compressive strength, deformation modulus, and permeability coefficient are selected to be the evaluation index of grouting reinforcement effect. Grouting reinforcement effect under different water‐cement ratio of cement slurry and curing time were measured. Eventually, under laboratory conditions, fitting formulas have been obtained which describe the quantitative relationship between reinforcement effect of permeation grouting and water‐cement ratio and curing time. Results show that water‐cement ratio of slurry has obvious effect on grouting reinforcement effect. Mechanical performance and impermeability of the grouted body are negative‐correlated with water‐cement ratio. There are two different destruction patterns for the grouted body in uniaxial compression process: global destruction pattern at low water‐cement ratio and local destruction pattern at high water‐cement ratio. If cement slurry at high water‐cement ratio is permeated into the sand layer, water bleeding phenomena will appear and lead to inhomogeneous performance of the grouted body, with lower performance in the upper part and higher performance in the lower part of the grouted body.

A Novel Class F Fly Ash‐Based Geopolymer and Its Application in Coal Mine Grouting

The novel class F fly ash‐based geopolymer, largely made of fly ash from the coal solid waste, was used as a kind of grouting material in the coal and electricity‐integrated mine from which the solid waste comes, for the purpose of in situ utilization of fly ash. The ratio experiment of material, designed through the orthogonal method, was used to study material properties such as fluidity and strength which are important to the application of mine grouting, and the optimal material proportioning scheme for Green Fly Ash‐based grouting material is determined. It has been found out that there was serious rib spalling, roof deformation, obvious floor heave, crack development, and some water seepage in the permanent refuge chamber of the mine. Therefore, to solve these problems, a specific scheme of grouting reinforcement for the surrounding rocks of the permanent refuge chamber and roadway in this mine was designed. Through an analysis of the reinforcement effect of the cementation of surrounding rock after the grouting process, it can be concluded that the green fly ash‐based polymer as grouting material can well penetrate into the cracks of the broken surrounding rock and get fully cemented with the surrounding rock and that it can reduce the deformation of the surrounding rock effectively, increase the integrity, and improve the carrying capacity of the surrounding rock. Besides, the grouting reinforcement effect of surrounding rock was verified through numerical simulation, and the grouting process design of green fly ash‐based polymer mine was discussed. This study can provide a green and economical approach to the in situ utilization of fly ash which is a kind of coal solid waste.

Forward Modelling and GPR Imaging in Leakage Detection and Grouting Evaluation in Tunnel Lining

Tunnels in the operation period are faced with different types of diseases, such as lining fracture, lining containing voids and lining leakage. In this paper, the common tunnel lining diseases are classified and ground-penetrating radar (GPR) is adopted to detect the tunnel lining diseases rapidly and nondestructively. The finite-difference time-domain (FDTD) method is used to carry out numerical experiments on GPR detection forward modelling and backward projection imaging. An interpretation criterion of GPR detection was established on typical lining diseases. Based on the dielectric differences between before and after grouting of tunnel lining, GPR is introduced into the evaluation of grouting on leakage in tunnel lining, and the numerical simulation of grouting effect is carried out. It can be concluded that GPR imaging can well-identify the dielectric changes before and after grouting and evaluate the grouting reinforcement effect more intuitively. Finally, this method was applied to a practical case in Kaiyuan tunnel, China. This paper provides an alternative way to detect tunnel lining leakage in operation period and a reference for the evaluation of structural defects reinforcement in underground engineering.

Reinforcement simulation of water-rich and broken rock with Portland cement-based grout

To explore solutions for water plugging and reinforcement problems of water-rich and broken rock mass in underground engineering, it is necessary to study the performance of cement-based grout and its reinforcement effect. In this study, Portland cement-based grouts with high amounts (70%) of granulated blast-furnace slag (GBFS) (30%) and Class C fly ash (FA) (40%) were prepared. The superplasticizer (SP) and anti-washout agent (AWA) were formulated to improve flowability and stability of single slurries. A new self-developed experimental device was designed for the grouting simulation. The fresh-state properties of cementitious single slurry i.e., flowability, mini-slump, stability, effective W/S and initial/final setting time; flexural and compressive strengths of grout stone bodies were studied. Meanwhile, the grouting reinforcement effect; mechanical performance of reinforcement sample i.e., unconfined compressive strength (UCS), failure mode, process and key parameters were evaluated. The results show that the performance and grouting effects of cement-based grouts with high amounts of GBFS and FA were generally acceptable. The addition of SP + AWA enhanced the stability and was beneficial to the grouting effectiveness especially at higher (0.8–1.2) water-solid (W/S) ratios. The diffusion or setting time of this type grout should be shortened appropriately in practice. The rupture interface and tensile fracture of grout were two main failure modes of reinforcement samples. The variations of key parameters corresponding to different failure modes were analyzed.

Study on Properties of Grouting Materials and Reinforcement Effect in Coal Roadways Influenced by Dynamic Pressure

In order to study the occurrence mechanism of rock burst in coal roadways under the influence of mining activities, the study took five main coal roadways in Yuwu Colliery as an engineering background. The occurrence mechanism of rock burst was analyzed by theory of dynamic and static combined load. Furthermore, based on the prevention mechanism of weak-strong structure, this paper puts forward to use a hierarchical coupled grouting method to reinforce the cataclastic surrounding rock of main coal roadways, and the laboratory test results show that slurry properties of superfine cement is better than that of regular cement. The numerical simulation law of slurry diffusion shows that the water-cement ratio and fracture aperture have obvious influence on the final diffusion distance, but the grouting pressure almost has no effect on it. A bolt-mesh-cable and grouting combined reinforcement method was applied in the five main coal roadways, and the borehole observation and deformation monitoring results show that the control effect of surrounding rock is satisfactory and the rock burst accidents caused by mining disturbance are effectively prevented. The study conclusions provide theoretical foundation and a new guidance for preventing rock burst in coal roadways.

Development of cement-based self-stress composite grouting material for reinforcing rock mass and engineering application

Grouting is an important method to reinforce fractured rock mass in underground engineering. To improve the grouting reinforcement effect of fractured rock mass, the theory of self-stress grouting reinforcement was put forward for the first time, and the self-stress grouting material was developed. The swelling stress of self-stress grouting material was tested by self-developed testing device to analyze the relationship between swelling stress and expansive agent content. Then, with cement, bentonite, silica fume, FZ expansive agent, accelerator, water reducer and water as raw materials, the effects of bentonite-cement ratio, silica fume content, accelerator content and water reducer content on the fluidity, initial setting time, uniaxial compressive strength at 3 days and 28 days of grouts were investigated by orthogonal test. Finally, the optimum proportion of the cement-based self-stress composite grouting material was applied to reinforce crushed coal blocks and the surrounding rocks of mine roadway, respectively. The results shown the optimum expansive agent content of the grout was 10%, corresponding swelling stress of 0.82 MPa. The proportion of the cement-based self-stress composite grouting material was bentonite-cement ratio of 1, FZ expansive agent content of 10%, silica fume content of 6%, accelerator content of 2.9%, and retarder content of 2.5%. The uniaxial compressive strength of the crushed coal blocks after reinforcement was 12.1 MPa, which was greater than the strength of the original coal. The cement-based self-stress composite grouting material had significant effect on the reinforcement of the surrounding rocks of mine roadway.

改建工程深基坑对地铁车站及区间隧道的影响分析

改建工程深基坑对地铁车站及区间隧道的影响分析

Feasibility of a Polymer Foaming Agent as a Grouting Material for Broken Coal Masses

A new soluble polymer foaming (PF) grouting material was developed by using hydrophilic amino resin as the base material and adding other cross‐linking, foam, foam stabilizing, toughening, and coupling agents. The PF material exhibited low viscosity, excellent adhesion, and strong penetration. The grouting reinforcement effect of the proposed PF material on broken coal masses was investigated and compared with that of traditional superfine cement (SC) through simulation experiments. Results showed that after grouting, fractures, joints, and other failure planes inside raw coal were filled and bonded, and the mechanical strength of the grout‐coal concretion improved relative to the residual strength of raw coal. The average uniaxial compressive strength of SC specimens was 6.16 MPa, whereas that of PF specimens was 10.85 MPa. Moreover, the PF specimens presented an obvious characteristic of plastic strengthening. Analyzing the reinforcement effect of the grouting materials on the basis of single structural plane theory revealed that at the critical state, the average σ3 value of SC specimens was 1.43 MPa, whereas that of PF specimens was 3.09 MPa. In addition, coordination between the lateral and axial deformations of the PF specimens during compression promoted the formation of a bearing structure that can adapt to deformation. This structure is crucial for the safe operation of coal mines.

Experimental and Mechanism Study of a Polymer Foaming Grouting Material for Reinforcing Broken Coal Mass

To study the mechanism of grouting reinforcement of broken coal mass, simulation experiments on grout reinforcing of broken coal mass were performed by using traditional materials, namely, Superfine Cement (SC) and Aluminate Cement (CA), and selfdeveloped Polymer Foaming (PF) grouting material. The macromechanical test results of the different grouting reinforced specimens showed that the residual strength of broken coal increased by different degrees after grouting, and the reinforcement effect was improved most notably by the PF material, which caused obvious plastic deformation characteristics of the coal mass that highly adapted to the deformation of the surrounding rocks, moreover, the long-term reinforcement effect was beneficial. Scanning Electronic Microscopy (SEM) showed that the grout-coal interfaces of the SC and CA materials were relatively loose and mainly affected by the types, quantities, and existence forms of cement hydration products, but had little relation to the properties of the injected medium. However, SEM showed a close combination at the interface with the PF material, which presented acceptable molecular compatibility. Moreover, FTIR indicated that some chemical grafting reactions occurred between the PF and coal mass, thereby leading to a firm polymer coating on the coal surface; thus, the grouting reinforcement effect of the broken coal mass was improved.

Experimental Study on the Reinforcement Mechanism of Segmented Split Grouting in a Soft Filling Medium

Subsection split grouting technology can effectively improve the grouting efficiency and homogeneity of grouting in a target reinforcement area. It is therefore necessary to clarify the reinforcement mechanism and characteristics of the soft filling medium under the condition of split grouting. A three-dimensional grouting simulation test of segmented split grouting in a soft filling medium was conducted. The distribution characteristics and thicknesses of the grouting veins were obtained under the condition of segmented grouting. The mechanical mechanism of segmented split grouting reinforcement, based on the distribution characteristics of different grouting veins, was revealed. After grouting, a uniaxial compression test and an indoor permeation test were conducted. Based on the method of the region-weighted average, the corresponding permeability coefficient and the elastic modulus of each splitting-compaction region were obtained. The quantitative relationship between the mechanical properties and the impermeability of the soft filling medium before and after grouting was established. The results revealed that three different types of veins were formed as the distance from the grouting holes increased; namely, skeleton veins, cross-grid grouting veins, and parallel dispersed grouting veins. The thicknesses of the grouting veins decreased gradually, whereas the number of grouting veins increased. Moreover, the strikes of the grouting vein exhibited increased randomness. The reinforcement effect of segmental split grouting on soft filling media was mainly confirmed by the skeleton support and compaction. The elastic modulus of the grouting reinforcement solid increased on average by a factor that was greater than 100, and the permeability coefficient decreased on average by a factor that was greater than 40 in the direction of the parallel grouting vein with the most impermeable solid. The research results may be helpful in the investigation of the split grouting reinforcement mechanism under the condition of segmented grouting.

Investigation on Reinforcement and Lapping Effect of Fracture Grouting in Yellow River Embankment

Fracture grouting has been a mitigation measure widely used against seepage in the Yellow River Embankment. However, there is currently a lack of systematic investigations studying the anti-seepage effect of the fracture grouting employed in this longest river embankment in China. Therefore, in this work, laboratory and in situ experiments are carried out to investigate the reinforcement effect of fracture grouting in the Jinan section of the Yellow River Embankment. In particular, laboratory tests concentrate on studying the optimum strength improvement for cement–silicate grout by varying the content of backfilled fly ash and bentonite as admixtures. Mechanical strength and Scanning Electron Microscope photographs are investigated for assessing the strength and compactness improvement. Subsequently, based on the obtained optimum admixtures content, in situ grouting tests are carried out in the Jinan section of the Yellow River Embankment to evaluate the reinforcement and lapping effect of fracture grouting veins, where geophysical prospecting and pit prospecting methods are employed. Laboratory results show that, compared with pure cement–silicate grouts, the gelation time of the improved slurry is longer and gelation time increases as fly ash content increases. The optimum mixing proportion of the compound cement–silicate grout is 70% cement, 25% fly ash, and 5% bentonite, and the best volume ratio is 2 for the investigated cases. Geophysical prospecting including the ground penetrating radar and high-density resistivity method can reflect the lapping effect of fracture grouting veins on site. It shows that the grouting material mainly flows along the axial direction of the embankment. The treatment used to generate directional fracture is proved to be effective. The injection hole interval distance is suggested to be 1.2 m, where the lapping effect of the grouting veins is relatively significant. For the investigated cases, the average thickness of the grouting veins is approximately 6.0 cm and the corresponding permeability coefficient is averagely 1.6 × 10−6 cm/s, which meets the anti-seepage criterion in practice.

Failure of bolt support and experimental study on the parameters of bolt-grouting for supporting the roadways in deep coal seam

Abstract This paper aims to provide some useful guidance for the design of parameters in bolt-grouting support and stabilize the surrounding rock in deep coal seam. A grouting reinforcement effect evaluation test instrument for fractured rock mass was developed. A laboratory test was carried out, the results show that the influence of water cement ratios on the grouting reinforcement effect was different, and the engineering proposals were put forward for the selection of water cement ratios. A field test was conducted for the selection of length and inter-row spacing of grouting bolt, the results show that the overall increase trend of pullout forces of common bolts was “Below > Right side > Above” under the condition of the same distance from grouting bolt, and the effective reinforcement range of grouting bolt had an important significance for the selection of parameters of grouting bolt. A successful field application was implemented, and the field test was verified as a good solution in the design of bolt-grouting parameters.

Application of Shaft Lining Monitoring System in the Deep and Thick Overburden

The vertical additional force could make the shaft lining in deep topsoil fracture. The force is caused by the bottom aquifer drainage settlement. In order to analyze the mechanical state of shaft, a shaft lining automatic monitoring system is built. The overall safety can be valuated by it. When monitoring data show that the shaft lining will be fractured, management measures can be timely taken to prevent more damage. In the process of ground grouting treatment to prevent shaft fracture, the monitoring data can be as the shaft lining stability and grouting parameters adjustment basis, to ensure safety and grouting reinforcement effect.

Research on the Lining Monitoring System of Mine Shaft in the Special Strata

The shaft lining in deep topsoil will be lead to fracture by the vertical additional force, which is caused by the bottom aquifer drainage settlement. Through the establishment of the shaft lining automatic monitoring system, the mechanical state of shaft can be effectively analyzed and the overall safety can be valuated. When monitoring data show that the shaft lining will be fractured, the rocks, management measures can be timely taken to prevent more damage by a ruptured shaft. In the process of ground grouting treatment to prevent shaft fracture, the monitoring data can be as shaft lining stability and grouting parameter adjustment basis, to ensure safety and grouting reinforcement effect.

Study on Shear Properties of Rock Structural Plane by Grouting Reinforcement

In order to study the grouting reinforcement effect of structural plane in cracked rock mass under uniaxial compression test and reveal the essence and mechanisms of grouting reinforcement, the roughness of structural plane in cracked rock mass was measured and studied. The influence of grouting on strength, JRC and stiffness was analyzed through shear tests of structural plane of cracked rock samples around grouting reinforcement. Test results were back-analyzed using JRC－JCS mode. The results showed that the JRC of structural plane in artificial cracked rock of the same rock mass was similar and replicable, the JRC value was about 8-10. Stiffness, roughness, peak shear strength (PSS), residual strength (RS), shear strength parameters (SSP) and slope of upward section (SUS) of structural plane were significantly improved by grouting reinforcement. The theoretical formula of structural plane stiffness was given by theoretical analysis.