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Groundwater seepage can easily cause large deformation and fracture instability of the surrounding rock in deep roadways, and the coupling support of "yield-bolt-grouting" can effectively control the occurrence of such accidents. This paper takes the specific engineering geological conditions of deep water-enriched roadway as the research background, revealing the coupling control mechanism of yield-bolt-grouting. The mechanical characteristics of the yielding tube were determined using lab analysis, and an investigation was conducted for the support control mechanism of high-strength yielding bolts. The control mechanism of grouting reinforcement is summarized, and a comprehensive coupling control technology system of "yield-bolt-grouting" is proposed based on the rheological large deformation characteristics of the surrounding rock of deep water-enriched roadway, with high-strength yielding grouting anchor rods and high-strength yielding grouting anchor cables as the core. The on-site monitoring results indicate that this technology effectively controls the deformation of the surrounding rock. The research results provide new ideas and technical approaches for controlling the surrounding rock of deep water-enriched roadways. [ABSTRACT FROM AUTHOR]

Bentonite grouting is utilized widely in geotechnical engineering to stabilize the excavation and prevent seepage in sandy soils. However, the infiltration behavior of bentonite slurry in sandy soil is not well understood, primarily due to rheological blocking and the formation of a filter cake. This study performed infiltration column tests to investigate the infiltration behavior under various conditions, including slurry concentration, sand properties, grouting pressure, and infiltration duration. Monitoring included infiltrated distances (calculated from drainage volume), pore pressure at different depths, and bentonite distribution using methylene blue titration. Results indicate that rheological blocking occurs during the infiltration process as bentonite slurry, which is a shear-thinning fluid, increases in viscosity with a decreased shear rate. This phenomenon is more pronounced with higher slurry concentrations, leading to reduced infiltration distances. Additionally, in soils with pore throats smaller than bentonite particles, a filter cake forms above the surface of the grouted soil, decreasing the pore pressure and further reducing infiltration distance. The distribution of bentonite content remains consistent across the infiltrated zone, resulting in a linear pressure drop. Based on these findings, the study proposes a novel model that combines the generalized Darcy's law, the Herschel–Bulkley rheological model, and mass conservation of slurry to predict the spatiotemporal progression of the infiltration front. This model, which was validated using experimental data, accurately predicts the effects of rheological properties and filter cake formation on infiltration. The results of this study provide valuable insights into infiltration processes and enhance the application of bentonite slurry in grouting. [ABSTRACT FROM AUTHOR]

Base grouting below a drilled shaft tipped in sand has been shown in many cases to dramatically improve both the initial stiffness and ultimate end-bearing resistance. After promising results from base-grouting case studies in the early 1960s, numerous grouting methods were developed, but end-bearing prediction methods remained largely proprietary for over 40 years, none of which were provided via design codes or specifications. No safety factors or resistance factors for any design method had been codified prior to this study. Instead, load test verifications routinely were performed, and the safety or resistance factor associated with the test method was applied. This paper assigned resistance factors for base-grouted end bearing from the results of 35 base-grouted shafts that were load-tested throughout the United States. Like other geotechnical capacity prediction methods (e.g., driven pile capacity), a higher resistance factor is established when increased field inspection is implemented, specifically when grout pressure verification demonstrates that the end-bearing soils have been effectively grouted to the specified design pressure. Practical Applications: Safety factors are a necessary parameter in the design of any structural element. Currently most codes either mandate load and resistance factor design (LRFD) or provide the option to use LRFD, which separates load and resistance factors to better isolate uncertainties and to achieve an acceptable level of safety. To date, no resistance factors have been incorporated into standard specifications for base-grouted drilled shafts. Hence, a load test is required to provide a suitable degree of certainty. This paper provides resistance factors for end-bearing resistance for base-grouted shafts and recommends a minimum level of field inspection to ensure that the grouting process is performed effectively. [ABSTRACT FROM AUTHOR]

Grouting technology can be selected to strengthen broken rock mass in order to improve its antiseepage and bearing capacity. Based on the working principle of infiltration grouting and grouting pipe technology, experimental and numerical studies are conducted by using high-water grouting material. In terms of numerical analysis and origin software, the polynomial prediction model is provided to establish the relationship between the grouting effect and influencing factors. According to the research findings, the lower the slurry level, the larger the diffusion range. The greatest influencing factors for diffusion radius, grouting volume, and strength are porosity, level height, and water–cement ratio, respectively. Through numerical simulation, corresponding amplification coefficient of diffusion length ranging from 1.21 to 1.33 is obtained, and subsequently, the maximum diffusion length is put forward. Finally, the slurry diffusion theoretical model is improved to explain the slurry diffusion characteristic. [ABSTRACT FROM AUTHOR]

As an effective reinforcement technology for seepage prevention, penetration grouting has been widely used in geotechnical and underground engineering. Because grouting is a hidden project, the extent of slurry spread is often estimated theoretically and through experience. Therefore, it is important to understand the diffusion pattern and scope of penetration grouting in reinforcement engineering. Based on the generalized Darcy's law, a penetration grouting model considering the gravity and the time-varying nature of the slurry viscosity is proposed in this study. Its validity and effectiveness are verified through a comparison with existing penetration grouting tests. Based on the established penetration grouting model, the effects of the grouting pressure, permeability coefficient, water–cement ratio, and other factors on penetration grouting are analyzed. The penetration and diffusion process of a Bingham fluid considering gravity and time-variable slurry viscosity is computationally simulated using a finite-element software. The research results show that the proposed penetration grouting model is more accurate than the traditional one that does not consider the two aforementioned factors, and its results are more in line with the experimental ones. The rate of error calculated from the experimental value is about 11%. The diffusion radius of the slurry increases with increasing grouting pressure, permeability coefficient, and water–cement ratio, and decreases with increasing groundwater pressure. With the elapse of the grouting time, the increase rate of the diffusion radius exhibits a trend of increasing first and then decreasing and tending to level off. These research results can provide certain theoretical support for penetration grouting research in geotechnical and underground engineering. [ABSTRACT FROM AUTHOR]

This paper aims to present the mechanism of scour and empirical equations for evaluating local scour with and without a countermeasure around the bridge pier. A critical review of scour countermeasures, mainly hydraulic, structural, and biotechnical, extending to the present time is done. Hydraulic countermeasures consist of river training structures and bed armoring. Structures placed parallel, perpendicular, or at an angle to the flow aiming to modify it is the purpose of river training works. Armoring is done through the use of riprap, partially grouted riprap, cable-tied blocks, grout-filled containers, and gabions. Structural countermeasures include foundation strengthening and pier geometry modifications. Extending footings, underpinning, and pile- underpinning are related to foundation strengthening, while pier geometry modifications include different pier features such as shapes, textures, slots, and collars. Biotechnical countermeasures include using vegetation riprap, geosynthetic polymer, live staking, and bio-stabilization using extracellular polymeric substances. Different combinations of countermeasures are also discussed. In hydraulic and structural countermeasures, riprap and collars are most commonly used due to their efficiency in scour reduction and economic feasibility. Bio-stabilization using extracellular polymeric substances is a novel measure for scour prevention. From the literature, it is concluded that pier modifications are the most effective and active area of research in which lenticular pier shape, lenticular hooked, and airfoil-shaped collar are best suited for reducing the local scour around the pier. Finally, the limitations of the countermeasures mentioned above are presented. [ABSTRACT FROM AUTHOR]

Shield tail grouting is an important measure to control tunnelling-induced ground deformation by injecting prepared grouting materials to fill the tail gap. The working performance of grout is usually invisible and hard to obtain in construction. This paper carries out an experimental study to investigate the tail grout behavior in ground. In the current research, a testing device is developed to explore the grout behavior in varying soils. The grout working performance is evaluated not only by the liquid grout properties such as fluidity, consistency, bleeding rate, stone rate and compressed deformation but also solid grout properties such as unconfined compressive strength and permeability. Three typical grouts are chosen and their behaviors in the various soils are observed. To take an insight on the behaviors, scanning electron microscopy and mercury intrusion porosimetry analysis are employed. The microstructure of solid grout is a sign of its working performance. The observation shows that the solid grout micro-structure is influenced by grout proportions, pressure, and ground permeabilities. The experimental results are applied in the case of Beijing Metro Line 12 for validation and as a result, the ground movement is inhibited due to high performance of tail grout. [ABSTRACT FROM AUTHOR]

To address the challenges of coal fracture image recognition, including interference from gangue and multiscale fractures, a multiscale coal fracture segmentation network model to significantly enhance the recognition of coal fracture structures is proposed. The model significantly enhances the recognition of fracture structures based on a U-shaped network architecture and the incorporation of several advanced techniques, including transfer learning, depthwise separable atrous convolutions, and residual modules. Transfer learning, by leveraging pretrained visual geometry group 16-layer network weights, bolsters the feature extraction capabilities of an encoder. Simultaneously, the integration of depthwise separable atrous convolutions and residual modules optimizes a decoder, thereby improving segmentation accuracy and the robust recognition of fractures within images. Experimental results based on qualitative and quantitative data showed that the proposed model surpassed traditional convolutional neural networks, demonstrating proficiency in identifying multiscale fractures in complex coal images. The model was applied to the identification of fractures in roadway surrounding rock boreholes. By extracting fractures from borehole imaging videos and planar diagrams, and conducting cross-validation, the study precisely delineated the fracture distribution. Additionally, to improve coal seam gas extraction efficiency, the grouting and sealing range for cross-layer extraction boreholes was determined. [ABSTRACT FROM AUTHOR]

In the construction of subsea tunnels, grouting reinforcement is crucial for enhancing tunnel strength, impermeability, and stability. This article investigates the impact of prolonged exposure to seawater, specifically magnesium ion corrosion, on the degradation of the C-S-H gel and the weakening of grouting compounds. Utilizing erosion acceleration theory, an experimental setup simulating seawater flow is designed to explore erosion patterns and mechanisms. Macroscopic and microscopic experiments and analyses reveal that magnesium ion corrosion products, Mg(OH)2 and M-S-H, lack cementation ability, leading to detachment from the grouting compound. This detachment results in increased porosity, crack formation, and reduced strength and impermeability. The study recommends reducing the water–cement ratio and increasing grouting pressure to enhance composite strength and impermeability, with attention to boundary effects and prevention of magnesium ion corrosion product shedding. These findings have significant implications for optimizing subsea tunnel construction by improving grouting reinforcement design and ensuring long-term durability. [ABSTRACT FROM AUTHOR]

This paper reports the results of a full-scale field test that was conducted to assess the performance of the use of wet-milling cement and chemical compound grouting in the same hole to reinforce a flexural fracture zone. Wet-milling cement and chemical compound grouting methods were used to treat a layer of the flexural fracture zone with a thickness of 19 m. The procedures of the cement–chemical compound grouting method were described in detail, and the results of the normal water pressure test, fatigue water pressure test, failure water pressure test, and shear wave velocity test suggested that the working effects in the epoxy testing area were better than those in the acrylic acid salt test area, which further indicated that the cement–chemical compound grouting method was feasible. In addition, the improvement mechanism of the cement–chemical compound grouting technology was studied; this method is beneficial for solving the problem of the reinforcement effect not being ideal in practical engineering and further improving the compactness of dam structures. [ABSTRACT FROM AUTHOR]

To investigate the mechanism by which clay shock slurry fills excavation gaps and reduces ground layer deformation during shield tunneling, we conducted a study using the project example of Beijing Metro Line 19 from Youanmenwai Station to Niujie Station, which passes through Guang'anmennei Station to CaiShiKou Station of Beijing Metro Line 7 at a close distance. We employed physical and mechanical testing, numerical simulation calculations, and other methods to examine the deformation law and mechanism of the clay shock method in shield tunneling construction. Our results indicate that (1) as the mass concentration of clay shock slurry increases, its permeability decreases significantly; at a mass concentration of 400 kg/m3, clay shock slurry can prevent synchronous grouting slurry from flowing forward, providing optimal filling and support for excavation gaps. (2) Clay shock slurry can reduce friction between the shield shell and soil body by 50%, avoiding super-consolidation, shear damage, and volumetric expansion of the surrounding soil body. (3) Radial grouting with a two-fluid slurry of cement–water glass at a 1:1 ratio within 15 rings after shield tail removal effectively reduces settlement of the existing tunnel. (4) Numerical simulations demonstrate that using clay shock slurry to fill shield tunnel gaps not only significantly reduces construction settlement but also effectively inhibits strata displacement along the tunnel axis. [ABSTRACT FROM AUTHOR]

This study researches the bending and shear performance of the fragile cross-section of square hollow steel-reinforced concrete columns using experiments, numerical analysis, and theoretical investigation. First, three tests of square hollow steel-reinforced concrete column (HSrCC) specimens considering different sectional sizes and grouting conditions were conducted. The bearing capacity and load transfer mechanisms under bending and shear loading were experimentally compared. Second, a numerical model was established based on the experimental results, and then parametric studies were performed on the bearing capacity and deformation of the structure. Last, a peak load calculation formula was derived in this study considering thickness and strength for a 400 × 400 square HSrCC. Based on the experimental results, the failure process of the specimen can be divided into four steps. Grouting increases stiffness at the front part of the specimen but induces significant damage at the rear compared to the no-grouting case, with the maximum strain increasing by 25%. Increasing the cross-sectional area of the concrete short column effectively improves the overall performance, with the maximum tensile strain of the concrete short column being reduced by approximately 1.2 times. Under the given sectional dimensions, parametric analysis suggests that the optimal square hollow steel thickness and steel strength range from 14 mm to 16 mm and from Q355 to Q420, respectively. The proposed peak load calculation formula demonstrates a discrepancy of less than 5.06% when compared with the numerical model results. These findings provide valuable references for the design of square hollow steel-reinforced concrete columns. [ABSTRACT FROM AUTHOR]

Featured Application: Grouting reinforcement of the top part of earth-rock dam. As a novel seismic reinforcement measure for earth–rock dams, the PFA-reinforced rockfill materials technology lacks comprehensive investigation into both its reinforcement efficacy and the underlying mechanisms. In this study, we establish a fluid–solid coupling model of PFA-reinforced rockfill materials utilizing the matrix discrete element software MatDEM3.24, developed independently by Nanjing University. The model simulates the dynamic process of polymer grouting within the rockfill body and analyzes the impact of slurry diffusion patterns and various grouting pressures on polymer grouting. Our findings reveal that the diffusion of polymer foam in rockfill occurs in three distinct stages, which are characteristic of penetration grouting. Moreover, we observed that grouting pressure had a significant effect on the diffusion range of the slurry, with greater sensitivity noted in the Z direction. Additionally, we observed a decrease in porosity with increasing grouting pressure, and stress augmentation exhibited an approximately linear relationship with grouting pressure, but the stress augmentation in different directions was different. These research outcomes offer valuable insights into the practical implementation and optimization of PFA-reinforced rockfill materials technology, bearing considerable engineering implications. [ABSTRACT FROM AUTHOR]

Rock bolting in underground environments is used for different fundamental reasons, including suspending potentially loosened blocks, clamping small wedges together, inducing a protective pressure arch along the contour of excavated voids to improve the self-supporting capacity of the ground, and providing passive pressure in integrated support systems. In this study, we describe a testing procedure that was developed to investigate the grouted annulus of a rock bolt using a low-cost investigation method. This diagnostic technique was based on the dynamic response of the system, where mechanical vibrations were induced within the rock bolt and the response was recorded by using geophones/accelerometers on the protruding element of the bolt (the collar and head). The collected signal was then processed to estimate the spectral response, and the amplitude spectrum was analyzed to detect the resonance frequencies. A 3D finite element model of the rock bolt and grouting was established to simulate the quality of the coupling by varying the mechanical properties of the grouting. The model's response for the studied geometry of the rock bolt suggested that a poor quality of grouting was usually associated with flexural modes of vibration with a low resonance frequency. Good-quality grouting was associated with a frequency higher than 1400 Hz, where the axial vibration was mainly excited. Our analyses referred to short rock bolts, which are usually adopted in small tunnels. The interpretation of the experimental measurements assumed that the spectral response was significantly affected by the quality of the grouting, as demonstrated by the modeling procedure. The resonant frequency was compared with the results of the model simulation. The method was used to test the quality of rock bolts in a small experimental tunnel carved from andesite rock in Chile. Low-cost shock sensors (piezoelectric geophones) with low sensitivity but a wide frequency band were used. The main research outcome was the development of a reliable method to model the dynamic response of rock bolts in mines or for experimental applications in tunnels. Albeit limited to the current specific geometries, the modeling and testing will be adapted to other anchor/bolt options. [ABSTRACT FROM AUTHOR]

The enzyme-induced calcium carbonate precipitation (EICP) technique was utilized to cement calcareous sand. The mechanical properties of EICP-cemented calcareous sand at various cementation degree were investigated using consolidated drained triaxial compression tests. A statistical damage constitutive model tailored for EICP-cemented calcareous sand was also developed based on damage mechanics theory. The findings are as follows: (1) The EICP technique significantly enhances the cementation of calcareous sand. As the number of grouting operations increases, the peak deviator stress of the cemented material gradually increases, with the maximum enhancement approaching 2.5 times. Moreover, during the stress decay phase following the peak stress, the decay rate of the cemented sand accelerates, displaying a more pronounced brittle characteristic. (2) With the increased calcium carbonate content, the peak eccentric stress of the cemented body increases significantly, and there is an obvious nonlinear exponential correlation between them. (3) The statistical damage constitutive model, formulated based on Lemaitre's strain equivalence principle combined with a log-normal distribution and the Drucker–Prager strength criterion, accurately predicts the stress–strain curves, effectively simulating the complete stress–strain evolution of EICP-cemented sand under different numbers of grouting operations and varied confining pressure conditions. (4) At higher cementation levels or lower confining pressures, the internal damage process of the EICP-cemented calcareous sand specimens intensifies, indicated by the rapid increase of the damage variable D with axial strain. The research findings can provide a crucial theoretical foundation for the application of EICP technology in the treatment of island reef or roadbed foundations, aiding in the analysis and prediction of the mechanical properties of EICP-cemented calcareous sands. [ABSTRACT FROM AUTHOR]

Various testing methods have been proposed and conducted on cable bolt pull out in the last century. Large and small scale tests have both provided valuable information about the behaviour of the cable bolts. This study compares large scale and small scale pull out experiments with similar cables, bonding agents (grout and resin), and loading paths (monotonic and cyclic) to juxtapose the unique characteristics of each test. The results suggested that small scale tests in grout tend to have lower repeatability compared to large scale test while large scale test typically provide a stiffer behaviour with higher initial peak loads. In cyclic loading, large scale testing tended to have most of their cycles in the first 5 mm whereas small scale test loading and unloading cycles were more spread. In resin cases, bulbed cables had similar behaviour whereas the unbulbed cables had various load values suggesting the presence of bulbs overshadows other characteristics. [ABSTRACT FROM AUTHOR]

The influence of underground excavation on urban areas constitutes a critical issue in tunnel engineering. This paper strives to establish a machine learning algorithm to predict maximum tunnel induced surface displacement. The algorithm was developed using FLAC3D and validated under actual conditions in the twin tunnel of the Seville metro line. A dataset of 526 simulations of underground excavation with Earth Pressure Balance (EPB) was used to predict the maximum surface displacement using machine learning techniques. Five machine learning methods to evaluate the significance of input data variables, as soil properties, tunnel depth, face pressure or grout pressure of EPB, proving the most accurate models, were Gradient Boost and XGBoost. Additionally, the feature importance analysis conducted using Random Forest indicated that soil properties play a crucial role in the prediction process. The XGBoost model's effectiveness in predicting surface displacement has been confirmed through validation on real monitored data from Seville metro tunnel Line 1. The percentage error of the calculated values was compared with the real vertical surface movements obtained, and it varied from 3.24 to 10.66%. This study develops a practical approach to improving construction planning for future excavations in Seville, making them safer and more efficient. [ABSTRACT FROM AUTHOR]

The complex mechanical characteristics of calcareous sand complicate comprehensive analysis of the bearing characteristics of pressure grouting piles. The bearing mechanism of pressure grouting piles is unclear. Field tests of the bearing characteristics of pressure grouting piles in calcareous sand foundations were carried out. On the basis of the field test data, the coupled finite difference method (FDM) and discrete element method (DEM) were applied to explore the settlement characteristics. The force transfer laws in calcareous sand foundations are analyzed using complex network theory. The results show that the ultimate bearing capacity of pressure grouting piles increases significantly with increasing pile diameter. An increase in the pile‒soil interface friction coefficient can increase the pile side friction resistance, which can then increase the ultimate bearing capacity of the pile foundation. The friction coefficient of calcareous sand foundations can also increase the ultimate bearing capacity of pile foundations. However, the settlement of the pile foundation also increases. The axial force of the grouting pile gradually increases as the burial depth increases. When the pile bottom is reached, the axial force of the pile body clearly increases. This study presents an effective tool for the comprehensive analysis of the bearing characteristics of pressure grouting in calcareous sand foundations. [ABSTRACT FROM AUTHOR]

This study investigates the effectiveness of modified graphene (MGE) for developing novel structural adhesives and their application in concrete beam reinforcement. The research aims to reveal the mechanism of MGE and evaluate the effect of different reinforcement methods on the flexural performance of concrete beams. Two adhesive formulations – original structural adhesive (OSA) and functionalized graphene-based structural adhesive (FGSA) – were examined alongside two reinforcement methods: the grouting reinforcement method and the adhesive fiber-reinforced polymer (FRP) method. The results show that the increased spacing of the functionalized MGE flakes improved their dispersion in epoxy resin, enhancing cohesive forces through bonding interactions and leading to the enhancement of the basic mechanical properties of FGSA by 6% to 12%. Compared to OSA, the application of FGSA improved the flexural properties of concrete beams, with the degree of improvement depending on the reinforcement method, while the failure mode of the beams remained unchanged. In addition, the FGSA/FRP combination showed the most significant improvement in the fracture parameters (220% to 480%) compared to the unreinforced control, highlighting its efficiency and cost-effectiveness as a reinforcement method. These findings offer valuable insights into reinforcement strategies for concrete beams, addressing the limitations of structural adhesive bond strength and optimizing reinforcement techniques. [ABSTRACT FROM AUTHOR]

In recent years, the rapid expansion of subway construction has brought increasing challenges related to the crossing of new and existing subway lines. This study focuses on the Nanjing Metro line 11 project, where the new line crosses the existing line 3. A numerical simulation analysis of the tunnel intersection area is conducted using ABAQUS software to investigate the deformation mechanism of shield segments when a new tunnel is constructed at a close distance and oblique angle to an existing tunnel. During the construction of a new tunnel, the existing tunnel segments experience the greatest settlement at the intersection point, with the deformation pattern gradually evolving from a V-shape to a W-shape. The majority of the deformation in the existing tunnel occurs during the close-crossing stage of the new tunnel. An ultra-high-performance grouting (UHPG) material is proposed, and the optimal reinforcement material ratio is determined through tests. The UHPG material is applied to the underside of the existing tunnels in the crossover section for local reinforcement. The results demonstrated the effectiveness of the proposed reinforcement method. Specifically, the deformation of the left line and right line of the existing tunnel is reduced by 35.0% and 33.1%, respectively, the segmental stress decreased by 10.1%, and the ground subsidence was reduced by 13.2%. [ABSTRACT FROM AUTHOR]

This article uses the engineering background of the Zhengzhou Metro Line 5 with a cement-soil group pile composite foundation. It simplifies the composite foundation using the area-weighted composite modulus method and establishes a finite element model of a double-line EPBM passing beneath the cement-soil group pile composite foundation building. The calculation results were compared and validated against monitoring data. Based on this, the simplified model was used to analyze the effects of face pressure and grouting pressure on the settlement of the upper structure. The research results indicate that the numerical simulation curves of settlement at monitoring points F17, F16, F15, and F14, where the shield axis intersects the building plane, align well with the monitored values, thereby confirming the rationality of the simplified model. Additionally, appropriately increasing the face pressure and grouting pressure is beneficial in suppressing the settlement of the upper structure; however, when the face pressure increases to 0.20 MPa and the grouting pressure increases to 0.35 MPa, the suppressive effect significantly diminishes. [ABSTRACT FROM AUTHOR]

In trenchless pipe jacking engineering practice, the formation of high-quality slurry jacket on the outer wall of pipe section is the key to effectively reducing the pipe-soil frictional resistance, improving the construction efficiency, reducing the construction risk and ensuring the construction safety. Herein, the multifunctional experimental apparatus for the pipe-soil frictional resistance testing is improved to ensure the smooth implementation of the subsequent experimental research. The influences of the structural parameters of grouting holes in circular and rectangular pipe sections on the pipe-soil frictional resistance and the states of slurry jackets around the various pipe sections are investigated respectively based on orthogonal experiment. Key findings include the pipe-soil frictional resistances increase with the increase of the spacing between adjacent grouting holes and the deflection angle of grouting holes, the layout of grouting holes has the greatest influence on pipe-soil frictional resistance, reasonable and uniform layout of grouting holes around the pipe sections can form more complete high-quality slurry jackets, to show better pipe-soil frictional resistance reduction effect. Moreover, the optimal structural parameters of grouting holes in circular and rectangular pipe sections are the same, i.e. the layout is triple grouting holes, the spacing between adjacent grouting holes S is 417 mm, and the deflection angle of grouting holes α is 40°. These insights could provide some scientific and valuable guidance for pipe-soil frictional resistance reduction during trenchless pipe jacking. [ABSTRACT FROM AUTHOR]

Capsule expansion technology (CET) is innovatively developed to protect subsurface structures from underground engineering construction. However, it has hardly been reported in pile settlement control using CET. In this study, field trials were conducted to verify the feasibility of pile lifting using CET in soft clay, compared to the Tube-a-Manchette (TAM) grouting. Meanwhile, numerical simulations were used to further explore the pile–soil–capsule interaction and load transfer mechanism during pile lifting. The result showed that CET could effectively lift the pile by 1 mm after consolidation, with the lifting efficiency of CET at 62.5% and that of TAM grouting at −200%, proving the feasibility of CET for pile lifting. The ultimate bearing capacity of the pile was improved by 25%, which is attributed to the reinforcement of the soil at the lower part of the pile by the expansion. Pile tip resistance and skin friction near the lower part of the pile play the primary role in bearing the pile head load after CET processing. Moreover, CET changes the load transfer mechanism of the pile, a downward load transfer mechanism after expansion and an upward load transfer mechanism after consolidation. Accordingly, it confirms that the pile is lifted by the coupling effect of pile tip resistance and skin friction during expansion. Then, reducing pile skin friction and tip resistance leads to pile settlement during the consolidation stage. [ABSTRACT FROM AUTHOR]

The time-varying viscosity of quick-setting slurries will cause the spatial variation of slurry viscosity, which has an important impact on the diffusion mechanism of infiltration grouting. With the time-varying Bingham fluid constitutive model and the uniform capillary group theory, a cylindrical–hemispherical slurry infiltration diffusion model was established, considering the time-space variation of slurry viscosity. According to the soil parameters and slurry rheological parameters, the slurry pressure can be calculated at different diffusion radius and times. The effects of the permeability, porosity, and grouting rate of the injected medium on the grouting pressure and grouting diffusion radius were analyzed. The medium porosity is very critical for the design of the slurry diffusion radius. A 3-dimensional infiltration grouting test was carried out. The infiltration grouting pressure under different grouting rates and soil parameters were obtained. The results obtained from theoretical model were compared and verified with the test results. The results show that the grouting pressures calculated from the infiltration diffusion model proposed in this paper are in agreement with the experimental results. The grouting pressure calculated by the theoretical model is 1.05–1.25 times of the experimental value. [ABSTRACT FROM AUTHOR]

The sealing efficiency of pressure grouting in coal seam boreholes is pivotal for enhancing gas extraction and mitigating environmental risks. Therefore, this study integrated theoretical and modeling approaches to investigate the development of fractures around coal seam boreholes, elucidate the migration behavior of non-Newtonian sealing slurries within fracture networks, and analyze the effects of structural parameters of fractal-like tree fracture networks on paste material permeation. First, a fractal-like, tree-like fracture bifurcation network is introduced to describe the distribution of fractures around coal seam boreholes, and the spatial fractional constitutive equation of non-Newtonian fluid is used to solve the nonlocality of non-Newtonian fluid flow and the potential correlation of particles inside the fluid. Then, the seepage model of grouting sealing material in the fracture network around coal seam drilling is constructed, and the associated seepage characteristics are examined. The research reveals the direct influence of critical parameters such as the space fractional derivative order (α), fracture network opening ratio (β), fracture network length ratio (γ), maximum bifurcation series (m), fracture opening fractal dimension (De), tortuosity fractal dimension (DT), primary fracture length (l0), the maximum opening of fracture network (emax), and the number of fracture bifurcations per level (s) on the seepage characteristics of grouting materials. Specifically, it can be obtained by the theoretical model that the permeability of the fracture network is positively correlated with β, s, De, and emax, while it is negatively correlated with α, γ, m, DT, and l0. These findings provide a theoretical basis for understanding the seepage behavior of non-Newtonian fluids in engineering coal-rock fracture networks and developing efficient sealing materials for coal seams. [ABSTRACT FROM AUTHOR]

To address the stability challenges when large-section chambers are excavated in deep mining, this study employed numerical simulations to investigate excavation sequences and optimize support parameters for large-section chambers. A distribution and excavation model for large-section chambers was established, and 16 excavation schemes were designed based on principles such as "roof first, then walls" "walls first, then roof" and "simultaneous walls and roof" as well as the cutting approach of integrated excavator on mine site. The study analyzed the effects of 5 different support types and optimized support parameters based on the simulation results. The findings indicate that the "roof first, then walls" excavation sequence results in minimal disturbances when considering factors like plastic zone changes, surrounding rock convergence, and excavation equipment. Bolts, cables, and concrete lining significantly enhance chamber stability and load-bearing capacity; however, deformation persists in the wall, middle, and middle areas of floors of the chamber. It is recommended to increase the density of bolts and cables and supplement with grouting for reinforcement. [ABSTRACT FROM AUTHOR]

The diffusion process and effect of grouting in rock fractures are affected by the grouting parameters, fracture parameters, and external environment. On the basis of theoretical research, a numerical simulation method of rough fracture grout propagation refinement based on Bingham–Papanastasiou rheological model is established in this paper. The propagation test of fracture grouting is designed, and the correctness of the numerical simulation method is verified by comparison between the model test and numerical simulation under standard working condition. Based on the standard working condition, the influences of grout water–cement ratio, grouting pressure, water-rich environment and filling rate on grout propagation are investigated, and the temporal and spatial distribution characteristics of velocity field and pressure field during grout propagation are analyzed. A simplified model of fissure-filling grouting infiltration is used to determine the geometric equivalence of the fissure-filling rate, and an empirical constant term fitting method for the Forchheimer infiltration equation of a Bingham flow-type grout is proposed. Highlights: On the basis of theoretical analysis and model tests, this paper fills the gap in numerical simulation research on grout diffusion to some extent. This study establishes a refined numerical simulation method of rough fracture grout diffusion based on the Bingham–Papanastasiou rheological model. This study explores the effects of the water-cement ratio, the grouting pressure, water-rich environments and the filling rate on grout diffusion. This paper proposes a fitting method for the empirical constant terms in the Forchheimer seepage equation for Bingham grouts. The research helps to quantify the influences of multiple factors on grouting reinforcement and summarize the grout diffusion effect law. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The reasonable parameters setting of grouting and sealing boreholes is key to improve the efficiency of gas extraction. In response to the poor effect of grouting and sealing boreholes drilled by large-diameter drilling bit under multistage excavation, the fracture evolution and slurry diffusion laws of slurry are studied, both the fracture evolution laws, and the slurry diffusion laws based on the fractures distribution of multistage large-diameter drilling boreholes is obtained. The results show that when the final size of boreholes is 400 mm diameter, comparing with the one-time borehole-forming method, the radius of drilling fracture area of the multistage borehole-forming method increases from 0.50 m to 0.75 m, which shows the latter drilling method can provide more fissure channels for gas migration. The number of shear fractures generated in the coal body around the borehole is significantly higher than that of tensile fractures, proving that shear stress is the main reason for the formation of fractures. When the grouting pressure is increased from 2.00 MPa to 3.00 MPa, the diffusion distance is increased from 0.644 m to 0.657 m while the maximum slurry diffusion velocity is increased from 0.10 m/s to 0.18 m/s; when the consistency coefficient k is increased from 13 Pa·s to 21 Pa·s, the maximum slurry diffusion velocity is reduced from 0.14 m/s to 0.08 m/s while the diffusion distance drops from 0.662 m to 0.644 m. According to the results of numerical simulation and empirical formula verification, when applying high-pressure holding grouting technology to the coal mine working face in Shanxi Province, it is confirmed that the best grouting diffusion effect can be achieved when the optimal grouting pressure is 3.00 MPa and the optimal water/cement ratio is 1:1.2, the radial diffusion radius of grouting can reach between 0.597 m and 0.615 m. The results can provide the theoretical basis for determining the grouting parameters for sealing multistage large-diameter drilling boreholes. [ABSTRACT FROM AUTHOR]

In order to find the optimal ratio of inorganic double liquid materials and improve the coal fixing effect of materials, based on the mechanism of coal wall reinforcement, four factors such as fluidity, setting time, compressive strength and bond strength are selected as evaluation parameters. Then the optimization experiment of material ratio is carried out by single factor control method. The results show that when the ratio of water to cement, the ratio of lime to gypsum, the content of water reducing agent and the content of suspension agent are 0.7, 1:7, 0.25% and 0.3%, respectively, the performance of the inorganic double liquid materials can reach the best. The deformation trend of coal reinforced by grouting before and after the optimization of material ratio is the same, and the four stages of compaction, elasticity, yield and failure are successively experienced under compression conditions, but the load resistance and deformation resistance of the cemented coal after optimization are obviously improved. Under uniaxial and triaxial compression conditions, the consolidated coal mostly produces shearing-tension-friction mixed failure, and the coal block fracture occurs after the optimized material reinforcement, which further reveals that the optimized inorganic double liquid material has better coal fixing effect. Although the optimized inorganic material is difficult to achieve the effect of Marisan grouting reinforcement, it can avoid the shortcomings of high reaction temperature, high price and difficult preparation, which can provide a reference for the research of coal wall grouting reinforcement materials. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Shanghai Jiao Tong University (1006-2467) is the property of Journal of Shanghai Jiao Tong University Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of China Rural Water & Hydropower is the property of China Rural Water & Hydropower Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The low injectability and strong permeation of micro-fractures in argillaceous rock masses significantly impair the impermeabilization and reinforcement performance of conventional cement-based grouting materials. This study first develops a highly injectable and high-strength nano-silica sol-based composite grout. Then, the characteristics of silica sol, cement grout, and composite grout in argillaceous fractured rock masses are analyzed and compared. The permeation mechanism of the composite-grout grouting in these rock masses is preliminarily elucidated, and the grouting process is described in detail, showing its application prospects. The research results indicate the following: (1) The electrical conductivity and stone-formation rate of granular pulp can reflect the characteristics of pulp filtration. Silica sol is a grouting material with nanometer particles, and the stone rate and gel strength are weakly affected by rock mass infiltration. (2) A large amount of water cannot be combined into the gel network and separated during the cement slurry percolation process, resulting in a significant reduction in the stone rate and compressive strength of deep rock mass. The minimum stone rate decreased to 45.19%, and the minimum compressive strength decreased to 2.29 MPa. This reduces the sealing and reinforcement effect of cement grouting on deep rock masses. (3) Rock permeation primarily affects the compressive strength of the formed stones, with minimal impact on the stability and stone-formation rate of the composite grout. As permeability decreases, the position of rock permeation shifts closer to the rock surface, while the sealing of deeper rock masses is less affected, enabling the composite grout to achieve dual functions of superficial reinforcement and deep sealing. This study provides theoretical support for the practical application of composite-grout grouting in reinforcing argillaceous rock masses. [ABSTRACT FROM AUTHOR]