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Effective and safe support in soft rock roadways remains a critical challenge in underground coal mining due to the extreme weakness of the rocks and their susceptibility to weathering and water invasion. This paper examines the tailgate of longwall panel 2606, a typical soft rock roadway excavated along the edges of mined-out areas with thin pillars at the Lvtang Coal Mine in Guizhou, China. Despite employing a combination of rock bolts, cable bolts, and surface support systems, significant roadway deformation was observed. The mechanisms behind this deformation were analyzed through in-situ tests and clay mineral composition analysis. These analyses revealed that the primary causes of the roadway's substantial deformation were the low strength and weathering susceptibility of the coal and surrounding rock. A novel synergistic control strategy combining anchoring, shotcreting, and grouting was proposed for supporting soft rock roadways. Detailed numerical simulations were conducted to evaluate the deformation and stability of the tailgate under various support scenarios, validating the effectiveness of the proposed support scheme. The synergistic support strategy was implemented to reinforce the 2606 tailgate, and field monitoring was conducted to assess its effectiveness. Monitoring data indicated that rib deformation with the new support design was reduced by 66% compared to the original design. The results demonstrate that the improved synergistic support system effectively mitigated large deformations and maintained the stability of the tailgate. These findings provide a valuable engineering reference for supporting and reinforcing soft rock roadways under similar geological conditions. [ABSTRACT FROM AUTHOR]

The stability of coal pillars in fault areas is crucial for ensuring the safe passage of working faces. Based on field observations, frequent coal pillar spalling and substantial tectonic coal crumbs leakage, as well as tilting of hydraulic supports, are observed when working faces transition from primary coal to tectonic coal. To analyze the instability mechanisms behind these phenomena, this paper establishes a mechanical model of coal pillars in fault areas and analyzes the distribution of tectonic stresses and factors affecting the stability of coal pillars. The results indicate that horizontal tectonic stress adheres to an exponential function dependent on the angle factor, where (k0) is a parameter associated with the friction angle of the coal body, the dip angle of the fault, and the friction angle of the fault plane. The stability of coal pillars is influenced by factors such as roof and floor pressures, coal pillar integrity, mining height, and shield support force, with coal pillar integrity being the most critical. To ensure the smooth passage of working faces through faults, this study proposes a combined control technique of "inclined mining" and "grouting," including reducing mining heights, adjusting the slope of working face advancement, and pre-grouting of coal pillars. Industrial experiments conducted on-site have shown improved integrity of tectonic coal, enabling the working face to pass through faults smoothly and significantly increasing production efficiency. [ABSTRACT FROM AUTHOR]

The grouted gravel pile is a new method of pile foundation, which has been widely used in engineering fields in recent years. However, the grout diffusion characteristics and full-field displacement response of soil during grouting have not been fully revealed and systematically studied in previous publications. This paper employed a transparent soil model test system to explore the effects of the grouting pressure (GP), soil pre-consolidation pressure (SPCP), and initial viscosity of grout (GIV) on the grouting performances and load-bearing characteristics of grouted gravel piles. The development laws of the grouting duration, displacement field of the soil, and ultimate load-bearing capacity of the pile were analyzed. The results show that the total grouting duration decreases with a higher GP, increases with the increasing GIV, initially increases and then decreases as SPCP increases. Both the range of horizontal and vertical displacements of the soil around the pile and the distribution of vertical displacements of the soil at the pile end were obviously enlarged with GP as well as with GIV. However, with the increasing SPCP, they showed a decreasing tendency. The vertical ultimate load-bearing capacity of the grouted gravel pile increases with GP, SPCP, and GIV to varying degrees. The findings of this study contribute to the understanding of the pile-soil interaction during grouting process of the grouted gravel pile, which may improve the design of construction parameters. [ABSTRACT FROM AUTHOR]

Understanding the leakage routes plays an important role in a successful remediation of water loss by consequently reducing its cost and time. Among the common methods for reducing uncertainty in leakage analysis, the geology, hydrochemistry, environmental isotopes, grouting analysis, water-balance calculations, and water level monitoring are applied at this study to find the dominant leakage routes at the Roudbal Dam site. Results show that two leakage routes are probable, through the karstic limestone at the right bank of reservoir. Leakage along the first route is based on the following evidence: (a) the occurrence of bedding plane conduits; (b) the appearance of leakage in the access gallery down gradient of grout curtain; (c) the similarity of water chemistry and isotopic content; (d) the close correlation of water-level response in open boreholes to fluctuation in reservoir water levels; and (e) inadequate sealeing of grout curtain in depth and length. For the second route, leakage evidence is based on: (a) the interpreted hydraulic connectivity of karst aquifers especially by the presence of springs at transverse faults; (b) the elevation of discharge zones approximately 300 m lower than reservoir water level; (c) the similar water chemistry and isotopic content; (d) the results of water-balance calculations; and (e) no grout curtain was constructed on this route. To reduce uncertainty along any proposed leakage route, a thorough hydrogeological investigations (including spring monitoring, tracer test, borehole drilling and karst assessment) and geophysical evaluation (particularly in sites with complex structure) are needed. It is concluded that to reduce uncertainty in the addressing leakage routes, the applied approach at each dam site must be based specifically on the local geological and hydrogeological conditions. [ABSTRACT FROM AUTHOR]

In tunnel construction, grouting is frequently used to decrease the permeability and increase the rock mass strength. One of the most challenging steps in grouting is choosing the best grout type to achieve the highest penetration and sealing efficiency in the joints. The main purpose of this study is to investigate the sealing efficiency of different grout types in the joints of a high-risk section of the Kerman water conveyance tunnel (KWCT). For this purpose, the penetrations of three types of grouts including Ordinary Portland Cement (OPC), Ultra-Fine Cement (UFC), and silica sol were determined using analytical equations. Thereafter, the sealing efficiency of each type of grout in joints with different apertures was calculated. Also, the penetration radius of each type of grout was simulated and calculated using UDEC code. Based on the results of the analytical equations, by performing the grouting for 20 min using silica sol-based grout, the joints of the high-risk section of the KWCT with apertures of 0.5–2.5 mm and 2.5–10 mm can be sealed at 'Fair' and 'Excellent' levels, respectively. Furthermore, based on the results of numerical simulations, the UFC and silica sol-based grouts can seal the joints in 'Good' and 'Excellent' levels, respectively. [ABSTRACT FROM AUTHOR]

Suction bucket jackets are increasingly being used to support bottom-fixed offshore wind turbines. It is generally assumed that contact between the underside of the bucket lid and the seabed is mandatory to safeguard against additional settlement. Lid contact is usually ensured by underwater grout injection, albeit this has a significant impact on the duration and costs of installation. Although grouting is routine, there are limited available data regarding the benefits of ensuring contact between the lid and the soil. This paper presents data from centrifuge tests of completely and partially installed buckets in dense sand subjected to vertical cyclic loading to investigate the role of lid contact. Lid contact was shown to have a discernible effect on displacement accumulation when buckets were loaded beyond the drained skirt capacity in compression. Under these conditions, settlement of a completely installed bucket was limited by lid contact with the soil plug, while partially installed buckets experienced continuous settlement, as expected. The physical evidence indicates complex load transfer mechanisms that are influenced significantly by the drainage conditions. Hence, an understanding of the soil drainage characteristics at a particular site would provide value when evaluating the requirement for under-lid grouting. [ABSTRACT FROM AUTHOR]

When constructing tunnels in composite strata of soft and hard rock combinations, the disturbance during construction often leads to the collapse and instability of weak strata. Pregrouting is commonly employed in tunnel construction to reinforce the weak surrounding rock, aiming to achieve stable excavation faces. The assessment of excavation face stability and the selection of grouting parameters are crucial for the safe construction of tunnels in composite strata. This paper utilizes the recently proposed discontinuity layout optimization (DLO) method. Taking the tunnel at the Shilaoren Bathing Beach Station in Qingdao as an example, the stability of the excavation face is quantitatively evaluated using a safety factor. Furthermore, the paper explores the influence of the position of the composite stratum boundary, friction angle, cohesive strength, and grouting parameters on the stability of the tunnel excavation face. Simultaneously, the paper fits the grouting parameters and safety factor curves under different geological parameters, aiding construction personnel in choosing reasonable grouting parameters. [ABSTRACT FROM AUTHOR]

The majority of a coal mine's goaf is semi-closed complex porous medium space, which is a critical place for coal spontaneous combustion disasters. To investigate the flow diffusion pattern of inorganic compounds in fractured coal in the goaf, as well as the capacity to put out coal fires. It examine the viscosity properties of an inorganic material slurry as a function of water/material ratio and time. By building a three-dimensional grouting test platform in the lab, simulating the broken coal body with sand and gravel, designing orthogonal tests to run multiple groups of grouting tests, and analyzing the effects of factors besides grouting pressure, water/material ratio, and air space ratio on the slurry diffusion radius. The effect of grouting pressure on the pattern of slurry diffusion radius of inorganic material and the water/material ratio under the action of grouting pressure is studied. The test of inorganic materials to extinguish coal pile fire is done, and the fire extinguishing and cooling ability is assessed in comparison to mud of the same grade, based on a prior research of inorganic materials to suppress CO formation in coal oxidation warming. According on the findings, the three-dimensional grouting test platform can pass the grouting test of loose sand and gravel bodies at various grouting pressures. The effects of grouting pressure, water/material ratio, and air space ratio on slurry dispersion are discovered to be multivariate power function relationships rather than linear correlations. The related slurry diffusion radius equation is established, and the variables impacting the parameters of the slurry diffusion range are evaluated, with the grouting pressure and water/material ratio having a substantial impact on slurry diffusion. Inorganic materials, as opposed to mud, require less time to extinguish coal pile fires and are less prone to scatter. It can form an oxygen barrier through continually covering the surface of coal. The study's findings might give a solid foundation for the avoidance of slurry and fire suppression of inorganic materials in the goaf. [ABSTRACT FROM AUTHOR]

The study is based on a section of the Zhengzhou Metro Line 8 quasi-rectangular shield tunnel. Field excavation trials were conducted to analyze the surface settlement patterns caused by the construction of a large-section quasi-rectangular shield tunnel in the rich water sand layer in Zhengzhou. Based on the characteristics of the rich water sand layer, ground settlement control measures were proposed. The research findings show that the surface settlement caused by the construction of the large-section quasi-rectangular shield tunnel in the rich water sand layer exhibits a temporal curve pattern of slow settlement (Stage I: pre-arrival of the shield), rapid settlement (Stage II: shield passage, Stage III: shield tail exiting 14.4 ~ 18 m), and stable settlement (Stage IV: late settlement). In Stage I, controlling the excavation rate to maintain balance between the cutter face pressure and soil pressure is effective. In Stage II, injecting lubricating mud between the shell and the sand layer to reduce soil friction and shear slip is recommended. In Stage III, increasing the synchronous grouting volume at the shield tail and adjusting grouting pressure, as well as timely filling the shield tail construction gap, are effective methods to reduce surface settlement. The Peck formula was used to fit the transverse settlement trough on the surface, with a linear correlation coefficient R²=0.983, validating the use of the Peck formula to predict surface settlement troughs for quasi-rectangular shield tunneling in the rich water sand layer. These research findings can provide data support and reference for similar projects. [ABSTRACT FROM AUTHOR]

The utilization of geopolymer as a grouting material has gained significant attention in research and construction applications. Geopolymer grout is a type of binding material that differs from traditional grouts, typically based on Portland cement. Researchers have explored its effectiveness and potential applications in grouting processes, considering its unique properties and characteristics. In this paper, various studies employing and utilizing geopolymer as a grouting material are reviewed. The emphasis is on mixture design of geopolymer grout, physical property, chemical composition of geopolymer grout, rheological behavior of geopolymer grout such as yield stress (in case of Bingham fluid) and viscosity, and engineering properties such as compressive strength, expansion, shrinkage, etc. [ABSTRACT FROM AUTHOR]

Magnesium phosphate cement (MPC) has a promising application in grouting. This study drew on the traditional cement-waterglass two-liquid grouting model. Creatively, the two main reaction components of MPC, dead-burned magnesium oxide and phosphate, were applied to the grouting field in a two-component liquid form. At the same time, through proportioning adjustment and experimental testing, we obtained A\B liquid components, which can be stabilized. In addition, MPC slurry was compared with the traditional grouting material, silicate cement slurry, to demonstrate its superiority. Finally, we simulated the grout diffusion process of the mixed slurry using the two-phase Darcy's law module of COMSOL Multiphysics subsurface fluids. The results show that the mixed slurry with a magnesium phosphate ratio of 1/3, a magnesium–boron ratio between 5% and 10%, and a water–cement ratio of 0.2–0.5 has better stability and mobility. Under the same fluidity, its strength is much higher than that of common silicate cement slurry and has good injectability. MPC was subjected to two-fluid grouting to take advantage of its fast-hardening and early-strengthening properties, while also improving its stability and fluidity. This study provided a theoretical foundation for the application of MPC. [ABSTRACT FROM AUTHOR]

According to the project example, in view of the area of wharf foundation bed hollowing out, underwater steel cage and stone throwing are set up, and stone dams are used on both sides of the gap area between the steel cage and foundation bed hollowing out, and underwater non-dispersed concrete is poured and secondary grouting is carried out for restoration. For the overturning area of the block, a prefabricated L-shaped baffle is set up, and rubber air bags are used on both sides of the gap area between the baffle and the overturning area of the block, and underwater non-dispersed concrete is poured and secondary grouting is carried out for repair. The implementation of the project has achieved good construction results, which can provide reference for similar projects. [ABSTRACT FROM AUTHOR]

The Dalian Bay Subsea Tunnel is constructed using the immersed tube method, where 18 sections of immersed tubes are prefabricated using a fixed dry-dock. The dock entrance serves as a protective barrier between the dry-dock and the sea, playing a crucial role in ensuring dock safety by preventing water ingress and providing wave protection. On the premise of safety and economy, it is necessary to take into account the convenience of construction and the ease of use. On the basis of summarizing the typical dock gate types for prefabrication of immersed tubes both domestically and internationally, this project adopts the fixed dry dock method, gravity-type dock entrances, and large floating caisson gate system. The dock entrance system incorporates curtain grouting, water stop strips, steel gates, and concrete structure water stop system, and is equipped with the energy dissipation self-flowing water dock gate pier structure. The caisson of floating dock gate adopts cast-in-situ scheme, which can provide reference for similar projects. [ABSTRACT FROM AUTHOR]

After the completion of the dry environment construction of foundation pit support, the support structure at the interface of the land and sea box culvert should be removed to complete the docking of the sea and land box culverts. In order to solve the limitation that the traditional hydraulic crushing hammer process can only dismantle cast-in-place piles in sequence due to the influence of site and equipment station location, and the impact on the construction period, this paper conducts technical research and application of the underwater dismantling of the pit supporting cofferdam with box culvert rows and high pressure jet grouting piles in the land section of Yulong Island refinery and chemical integrated project. The technology adopts underwater rope saw method to cut the cast-in-place pile, and uses the existing large-tonnage crane ship for integral lifting during the installation of the offshore box culverts to determine key parameters such as rope saw cutting equipment, integral lifting of crane, design of lifting hole and lifting attachments, realizing underwater green and safe dismantling of cast-in-place piles and ensuring the smooth implementation of the project. [ABSTRACT FROM AUTHOR]

The coupling effect between the spatial variability of slurry diffusion and the time-varying viscosity of quick-setting slurry is the time–space characteristics of slurry viscosity (TSCSV). The TSCSV is the governing factor for the complex and uncontrollable flow of slurry in fractures. In this regard, the flow pattern of quick-setting slurry is considered as a Bingham fluid with viscosity spatiotemporal characteristics. Using the fractal function with random parameters (W-M function), a single fracture with random fracture opening (RFO) is drawn, and a theoretical model on grouting diffusion in fractures is established considering the TSCSV. The RFO is corrected for head loss, and the spatiotemporal distribution equation of the RFO grouting pressure is derived. The relationship between grouting pressure, grouting time, and slurry diffusion distance is obtained. Additionally, the effects of the RFO, the fractal dimension of the fracture curve, the horizontal movement distance of the lower end face of the fracture, and the effects of viscosity and grouting rate on the viscosity and grouting pressure in the slurry diffusion space are discussed. Finally, by predefining the spatial distribution function of slurry viscosity for a single fracture in the numerical calculation model, a numerical simulation of random fracture distribution grouting considering viscosity spatiotemporal characteristics is achieved. The rationality of the model is validated through a comparison of theoretical analysis and numerical simulation, providing reference for the determination of grouting parameters in practical grouting projects. [ABSTRACT FROM AUTHOR]

In this paper, the mechanical properties and internal stress condition of the reinforcing bar sleeve connectors with ferro-tailed mineral sand cementitious grout as filler material were analyzed as research objects. Firstly, an experimental study was carried out on the reinforcing bar sleeve connectors of iron tailing sand grout with a 40% substitution rate of mechanism sand to analyze the mechanical properties of different grout types, age, and reinforcement diameters under unidirectional tensile, high stress, and large deformation of repeated tensile and compressive stresses. Next, five groups of sleeve joints with different anchorage lengths were set up for unidirectional tensile tests. The results show that, with the decrease of the diameter of the reinforcement, the grip force and bond strength of the iron tailing sand grout on the internal reinforcement gradually increase. Under conditions of large deformation and high stress due to repeated tensile loading, the residual deformation and total elongation of iron tailing sand grout sleeve joints are satisfactory. Additionally, the restraining anchorage effect of iron tailing sand grout in the end section is small. The utilization rate and integrity of iron tailing sand grout in the initial anchorage section are better. [ABSTRACT FROM AUTHOR]

Accelerated bridge construction is crucial in bridge engineering. In order to improve the seismic performance of prefabricated columns, this study proposes using ultra‐high performance concrete (UHPC) in the plastic hinge areas of prefabricated columns with bellows grouting connections. In particular, cyclic loading tests are carried out on four 1/3‐scaled columns, including two cast‐in‐place columns and two bellows grouting connection columns. The results show that columns with UHPC in the plastic hinge areas exhibit larger lateral and ultimate bearing capacity, ductility, cumulative energy dissipation, and stiffness compared to those with conventional concrete. Additionally, bellows grouting connection column with UHPC shows superior seismic performance compared to cast‐in‐place column with conventional concrete. The proposed finite element analysis model is in a good agreement with the test results. Through using finite element analysis, three key parameters influencing the seismic performance of bellows grouting columns are examined, and the optimal combination of these parameters is identified. [ABSTRACT FROM AUTHOR]

A constitutive model for the determination of anchor bearing capacity based on distributed sensing in geotechnical engineering From 2015 to 2017, as part of his work as head of research and development at Stump‐Franki Spezialtiefbau GmbH, the author devoted himself to the topic of pioneering measurement methods on the basis of Distributed Strain Sensing in geotechnics. One of the first developments was and is the monitoring of grouted bodies on strand grouted anchors. The new findings at that time were presented internationally at the DFI India, 2017 as well as nationally in construction technology, 2017 and locally at the 12th Hans Lorenz Symposium in Berlin, 2016. It was shown that the measurement results of the strain measurement using distributed strain sensing can be used to check over the following years whether the grouted anchors have been overloaded. The author already pointed out at the time that correct interpretation not only requires an understanding of the measuring process used, but also a certain wealth of experience in interpreting the measurement results in the direct context of geotechnics. As part of his work on the DIN standardization committee NA 005‐05‐17 AA Grouted anchors, accompanied by his practical experience, the author has dealt in depth with the question of what exactly is actually measured in the grout body using distributed strain sensing and what conclusions can be drawn about the load‐bearing capacity of grouted anchors on the basis of the measurement results. This article is intended to describe a constituent model on the basis of which further developments are possible for the interpretation of the measurement results with regard to their use as proof of economic efficiency and anchor load‐bearing capacity. [ABSTRACT FROM AUTHOR]

Re‐anchoring during severing of historical tendons Prestressed concrete bridges are increasingly being dismantled in Germany. The problem here is usually the insufficient knowledge of the properties of the materials used. In particular, it is difficult to determine the condition of the tendons and the grouting. In the course of dismantling, the cutting through of tendons away from the coupling joints can be advantageous for construction‐related reasons. A prerequisite for ensuring the structural safety of the dismantling section is successful bond anchoring of the tendons with the surrounding grout, the duct, and the concrete. In addition to a good condition of the tendons and the grouting, sufficient knowledge of this bond behavior is therefore essential. However, information on the bond properties of the prestressing steel used in the Unterrieden viaduct could hardly be found in the literature. For this reason, investigations were carried out during the dismantling of the Unterrieden viaduct to determine the condition of the tendons. This included strain recovery measurements to determine the existing prestressing and tensile tests on prestressing bars, which were removed from the structure subsequent to the strain recovery measurements. Furthermore, bond specimens were taken from the bridge and tested in the laboratory in order to draw conclusions about the anchorage behavior of the tendons. These investigations are intended to verify the assumptions made in the dismantling planning. [ABSTRACT FROM AUTHOR]

Synchronous grouting technology is a crucial aspect of shield tunnel construction. However, understanding the mechanism of slurry diffusion during this process is challenging due to its complexity and invisibility. Existing theoretical models often oversimplify the grouting process and do not account for multi‐stage diffusion mechanisms. By considering the radial penetration of slurry and viewing the diffusion process as the formation of annular pancakes through circumferential filling, a 3D diffusion numerical model is established using the volume of fluid (VOF)‐multiphase flow model in Fluent software. The model's validity is confirmed through calculations based on theoretical formulas and monitoring data from engineering examples. This study uncovers the patterns of slurry diffusion and examines how factors like porosity, grouting pressure, and slurry density impact diffusion radius and segment stress. The findings of this research provide a crucial theoretical foundation for shield synchronous grouting construction. [ABSTRACT FROM AUTHOR]

This paper aims to investigate the effect of combined end-and-side grouting on the bearing properties of large-diameter rock-socketed bored piles in highly weathered rock layers. Eight full-scale pile load tests were conducted in the highly weathered rock layer to analyze the enhanced mechanism of the combined grouted bored piles. The test data from pile mechanical testing were compared with the recommended values in the current specification and geological survey report. The results demonstrate significant improvement in the side and end resistances of the combined grouted bored piles, resulting in a substantial increase in the bearing capacity and effective settlement control. It was observed that the construction of impact holes for bored piles can cause severe damage to highly weathered rock structures and weaken the mobilization of side and end resistances. Moreover, it was found that the calculation of the enhancement coefficient in the current specification underestimates the practical bearing capacity. The measured enhancement coefficients for the side and end resistance of piles in fully or highly weathered rock layers range from 2.49 to 3.05 and 2.24 to 2.43, respectively, which are more reasonable and feasible for the calculation. The research findings deepen the understanding of the bearing characteristics of large-diameter rock-socketed bored piles with combined grouting and provide valuable case references for the optimal design of large-diameter combined grouted piles for building foundations in Shenzhen, China. Highlights: Post-grouting had the potential to improve super high-building foundation reliability while reducing pile length and cost. The improvement effect and improvement mechanism of combined grouted bored piles embedded in highly rock strata were revealed. The influence of the size effect for large-diameter piles in highly weathered rock was revealed. The construction of impact holes for bored piles can cause severe damage to highly weathered rock structures and weaken the mobilization of side and end resistances. The enhancement coefficients for the side and end resistance of piles in fully or highly weathered rock layers were proposed. [ABSTRACT FROM AUTHOR]

The grouting method is commonly used to seal rock fissures in subsea tunnels, and therefore the water and mud inrush can be prevented in this way. However, the current understanding of the grout diffusion mechanism inside the rock fissure under seawater conditions is still limited, especially inside the inclined rock fissure. This study first presented a novel rock fissure geometry schematization, which can be simplified to a single fissure with different inclinations. Then, based on the obtained time-varying grout viscosity under seawater conditions, the grout diffusion model of cement and sodium silicate grout (C-S grout) was developed by combining the equilibrium equation, constitutive equation, and continuity equation, which can be used to calculate the key parameters involved in rock fissure grouting, i.e., the grouting pressure and grout diffusion distance. After that, the change of grouting pressure with time was obtained. Furthermore, the numerical simulation of grouting in the inclined rock fissure was performed to verify the suitability of the grout diffusion model, and the comparison between them shows that they match reasonably well with each other. It is hoped that the conclusions could aid in the design of grouting in rock fissures around subsea tunnels with C-S grout in the future. HIGHLIGHTS: A novel rock fissure geometry schematization is presented. The C-S grout diffusion model in the inclined rock fissure under seawater is developed. The effect of time-varying viscosity on grout diffusion under seawater conditions is studied. The relation between the grouting pressure and grout diffusion distance is obtained. The numerical simulation of grouting in the inclined rock fissure is performed. [ABSTRACT FROM AUTHOR]

Water-reactive polymer grouts can be injected directly into contaminated sediment zones where a portion of the contaminated pore water may participate in grout polymerization and contaminants may be immobilized in the grout matrix. This study evaluated the effectiveness of injecting a water-reactive polymer grout into frozen soil for immobilizing iodide by incorporation into grouted soil monoliths. Iodide was used as a model sediment contaminant. Soil freezing is a unique method used in subsurface remediation and was investigated because it may limit the amount of contaminated water displaced and mobilized during pressure grouting. In addition, joint use of grouting and soil freezing has the potential to broadly impact other remediation challenges, for example, treatment of collapsible soil and soil in water-active areas. Variables analyzed were freezing, moisture content, iodide concentration, and accumulated pressure due to carbon dioxide gas generated during polymerization. Iodide mobilization, iodide leaching as cumulative fraction leached (CFL), effective diffusivity (D), and leachability index (LI) were evaluated. Iodide mobilized during polymer injection into frozen sands was 37.9%±12.9% which indicated that soil freezing did not prevent iodide from being mobilized when injecting the liquid polymer. Lowering the moisture content from 5% to 1.6% by weight, to align reacted water with the introduced polymer, resulted in a decrease in the mobilization of iodide to only 0.23%±0.06%. This is the lowest reported result for contaminant displacement from liquid reaction additions known to the authors. All grouted samples leached less and more slowly than the ungrouted (control) samples. Grouting reduced effective iodide diffusivity by more than 96% and the LI of the grouted soil monoliths was greater than 6.0, which meets the criteria for materials intended for shallow burial with radioisotopes. These results demonstrate that polymer grouting of sands can be used to immobilize and slow the subsurface transport of sediment contaminants. [ABSTRACT FROM AUTHOR]

Aiming at the condition of shield tunnel undercrossing the foundation of a pile group directly, using the settlement and inclination of the pile caps as the evaluation index, the reinforcing effect of the pregrouting of the soil around the pile foundation, the deep hole grouting behind the tunnel segment, and the combination of the two reinforcement methods are analyzed through three-dimensional numerical simulation. A reasonable reinforcement scheme is found and applied to practical engineering. The results show that for the pregrouting reinforcement of the soil around the pile, the optimal reinforcement scheme is to extend 0.5 m around the pile cap in the plane and vertically from the surroundings of the pile cap to 1/3 of the pile length below the bottom of the cap. When deep hole grouting reinforcement is adopted, larger reinforcement range and a certain range of radial reinforcement radius of tunnel section will result in a better effect of reinforcement. The combination of the two schemes is better than the single use of one. The practical application results show that the combined reinforcement scheme can effectively control the influence of shield tunnel excavation on the pile foundation of an elevated waiting hall. [ABSTRACT FROM AUTHOR]

Regional grouting treatment is an effective technical means to prevent mine water disasters, and the grouting effect is affected by many factors. In actual grouting engineering, the single constant-rate grouting method is often transformed into a variable-parameter grouting process. However, research on grouting rates has been insufficient. This investigation focused on the issue of "the diffusion law of variable-rate grouting slurry in regional governance". Methods such as theoretical analysis, numerical simulation, and field verification were used to evaluate the diffusion mechanism of variable-rate fracture grouting. The results indicated that the key parameters of variable-rate grouting, such as slurry diffusion distance and grouting pressure, were affected by the grouting rate. The decrease in the grouting rate reduced the migration speed of the slurry and the grouting pressure. The time for constant-velocity grouting and variable-velocity grouting to reach the same diffusion distance was 60 s and 108 s, respectively, which can be achieved with lower grouting pressure. When the grouting rate was 7.5 L/min and 30 L/min, the maximum grout diffusion distance was 2.81 m and 5.64 m, respectively, which required greater grouting pressure. The slurry diffusion rate decreased with the reduction in the grouting rate. Under the same diffusion distance conditions, variable-rate grouting took longer than constant high-rate grouting. In variable-rate grouting, the grouting pressure decreased stepwise with the grouting rate, with a final pressure drop of 77.4%. In grouting practice, the innovative use of the rate-reducing grouting method can greatly reduce the final grouting pressure under the premise of changing the slurry diffusion distance less, which can not only ensure the stability of surrounding rock but also reduce the cost of high-pressure grouting and the risk of grouting operation. The investigation results can provide scientific guidance for ground grouting renovation projects in deep coal mine water hazard areas. [ABSTRACT FROM AUTHOR]

As a green, environmentally friendly, and cost-effective grouting material, geopolymer requires consideration of grouting performance indicators such as strength and fluidity in order to achieve good injectability. For this reason, indoor ratio optimization experiments were conducted using liquid-solid ratio, water glass content, and water glass modulus as experimental factors. A multivariate second-order response surface regression model was constructed for compressive strength, flowability, and final setting time, and the influences of single factor and its interaction on various grouting performance indicators were obtained through variance analysis. The degree of influence of experimental factors on grouting performance indicators is as follows: liquid-solid ratio, water glass content, and water glass modulus. The interaction between liquid-solid ratio and water glass content has a significant impact on compressive strength, while the interaction between the other two factors has no significant impact on grouting performance indicators. Using the analytic hierarchy process and expert assignment method to obtain the relative weights of various grouting performance indicators, a multi- objective satisfaction function was constructed to optimize the ratio of slag-fly ash geopolymer grouting materials. Based on this, SEM testing was conducted on the slurry stone body with the best comprehensive ratio of grouting performance indicators. The results show that a small number of spherical unreacted fly ash particles can still be observed in the system, the slag particles and cement particles are basically fully reacted, and the oligomeric gel-like reaction products are rearranged and extended by deposition, and cross-lap with each other to form a dense and complete spatial network-like structure. [ABSTRACT FROM AUTHOR]

In order to solve the cost and environmental pollution problems caused by the transportation and stacking of shield tunneling muck, and to achieve the goal of resource reutilization of solid waste, a study was conducted based on a section of the Zhengzhou Metro Line 10 shield tunneling project. Excavated muck was used to replace sand, fly ash, and bentonite, while rice husk ash (RHA) was used to partially replace cement in the preparation of micro expansion synchronous grouting material. The effects of RHA content, muck particle size, water-binder ratio, and the type and content of expansion agents on the working and mechanical properties of synchronous grouting material were investigated. The results indicate that RHA significantly affects the slurry consistency and setting time, and higher RHA content leads to lower slurry consistency and shorter setting time. When RHA content is 25% (based on mass ratio of cement), the slurry consistency decreases by 27. 5% and the setting time shortens by 39. 9%. As RHA content increases, the compressive strength of slurry decreases first and then increases. As the particle size of muck increases, the slurry consistency and setting time decrease. Quicklime powder and high soundless static cracking agent (HSCA) as expansion agents reduce slurry consistency but effectively improve setting time and compressive strength. When HSCA mass fraction exceeds 3%, the expansion effect of HSCA is superior to that of quicklime powder. The tests determine that a water-binder ratio of 2.6, RHA content of 25%, adding larger particle size of muck, and the appropriate addition of expansion agents collectively meet all engineering requirements for slurry indicators, thereby providing a novel approach for the reutilization of shield tunneling muck and rice husk ash. [ABSTRACT FROM AUTHOR]

Full-length anchorage rockbolts are widely used in roadway reinforcement and rock controlling in underground mining. This article proposes using an elastic–debonding (ED) model to analyse the axial performance of rockbolts. The advantage of this ED model was that the full force–deformation curve of rockbolts comprised only three phases, which was relatively simpler to calculate. Its effectiveness was compared with experiment tests. Based on the ED model, a series of parameter studies was conducted. Results showed that for cross-section area of rock, there was a critical range. Once the cross-section area of rock was beyond that critical range, external rock had a mild impact on the axial performance of rockbolts. Rockbolt diameter significantly affected the axial performance of rockbolts. When rock diameter increased, the peak force of rockbolts increased linearly, while deformation at the peak force decreased non-linearly. The corresponding calculation equation between the peak force, deformation at the peak force, and rockbolt diameter was obtained. Borehole diameter had a mild impact on the axial performance of rockbolts. Increasing rockbolt length benefits improving the peak force of rockbolts. Rockbolt modulus of elasticity had a more apparent impact on the deformation at peak force. Mechanical properties of the bolt/grout (b/g) face affected the axial performance of rockbolts. Increasing the b/g face strength improved the peak force of rockbolts. Slippage at the ultimate load had a more apparent impact on the turning point between the elastic phase and the elastic–softening phase. [ABSTRACT FROM AUTHOR]

This study presents a collaborative sensing approach that integrates the pre-embedded sensor method and the impact-echo technique to enhance the accuracy of grout filling quality assessment for precast concrete sleeve connections. The pre-embedded sensor method, which relies on vibration energy attenuation, enables continuous monitoring of the grout filling process; however, its accuracy is limited at low filling degrees, as vibration energy values remain constant at approximately 255 when the filling degree is below 70%. In contrast, the impact-echo technique, based on the principle of impact elastic wave propagation, demonstrates high accuracy in evaluating grout filling degrees across various levels, with reflected waveform amplitude increasing accordingly. This collaborative approach establishes a functional relationship between vibration energy values from the pre-embedded sensor method and grout filling degree, allowing for a comprehensive assessment of grout filling quality. In field demonstrations, the calculated grout filling degree values deviated by less than 5% from the set values. Practical guidelines for implementing the collaborative sensing approach are also provided. The method developed in this study offers a reliable solution for assessing grout filling quality in precast concrete sleeve connections, addressing the limitations of individual testing methods. [ABSTRACT FROM AUTHOR]

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Anchor rods are widely used in tunnel construction to significantly improve the self-supporting capacity of surrounding rock and reduce structural stress. Hollow grouting anchor rods can greatly enhance their support effectiveness after grouting, and the quality of the grouting directly affects the load-bearing capacity of these rods. This study focused on the optimization design of a newly developed type of hollow grouting anchor rod stopper plug by conducting numerical simulations to refine its structural form and dimensions. The exhaust pressure stabilization effect of the newly developed stopper plug was tested through indoor model experiments and field trials. The results showed that the optimal dimensions for the stopper plug were an upper exhaust groove width of 8. 0 mm and depth of 1. 5 mm, a lower groove width of 11. 3 mm and depth of 1. 0 mm, an air-tight ridge height of 3 mm, and an outer stopper plug diameter of 51 mm at the opening and 50 mm at the far end. The grouting stopper plug was adaptable to various anchor rod hole diameters, and when the difference between the stopper plug and the anchor hole was 0 ~ 4 mm, it met the requirements for pressure stabilization and grouting performance. The experimental results showed that the stabilizing pressure of the new grouting stopper plug was between 0. 7 and 1. 2 MPa, with the anchor rod hole being fully filled and the grout compacted, demonstrating a significant grout-stopping effect. [ABSTRACT FROM AUTHOR]

Joints in frame structures often fail before beams and columns in an earthquake and are a key part of reinforcement. In this study, to enhance the seismic performance of concrete frame structures, a steel-jacketed grouting composite reinforcement method is proposed by combining reinforcement technology, steel cladding technology, and eco-efficient materials from grouting technology. This method effectively utilizes the advantages of various materials, avoids major demolition and construction, and reduces waste and resource consumption. In order to verify the feasibility and effectiveness of the reinforcement method, one of the original joint specimens with a scale of 1:3 and one of the reinforced joint specimens were designed and tested. The experiments involved reversed cyclic testing of beam–column to measure its seismic behavior. The seismic performance indexes such as failure characteristics, hysteretic properties, and the energy dissipation capacity of the specimens were analyzed, and the corresponding finite element model was established. The influence of key parameters such as reinforcement range, steel plate thickness, and grout strength on its seismic performance was explored. The research shows that the method can effectively improve the seismic performance of the joints, and seismic performance indexes such as bearing capacity, ductility, and energy consumption of the specimens are significantly improved. The test results of the established finite element model are in good agreement. The variable parameter analysis of the finite element shows that the thickness of the steel plate has little influence on its bearing capacity. With the increase in the reinforcement range of the clad steel and the strength of the grouting material, the bearing capacity of the specimen increases. The research results can provide a reference for the reinforcement of frame structure joints. [ABSTRACT FROM AUTHOR]

This study explores the deformation characteristics of surrounding rock during tunnel construction through fault fracture zones. A numerical model is established using ABAQUS to analyze the interaction between the shield machine, support system, and geotechnical materials. The model incorporates key factors, including palm face support force, grouting pressure, and the friction between the shield shell and surrounding rock. The results show that the plastic zone of the surrounding rock is concentrated within the fault zone and at the junction with normal rock, propagating along the contact surface. In the loosening zone, stress and strength are significantly reduced, leading to crack expansion and plastic slip. Without adequate support, these conditions can result in tunnel destabilization. The displacement of the surrounding rock is most prominent during the detachment of the shield tail and the synchronized grouting phase. These findings provide valuable insights for improving tunnel construction safety and stability in fault fracture zones, where the integrity of the surrounding rock is compromised by fractures and fissures. However, the constructed models may restrict the ability to capture all complex material behaviors and interactions that could arise in actual field conditions. [ABSTRACT FROM AUTHOR]

AbstractInvestigating the infiltration, diffusion and permeation of cement grouting materials in coral sand and the effects of grouting reinforcement measures can provide scientific support for coral sand foundation treatment, building settlement adjustment, and coastal geological disaster prevention and control. Permeation grouting tests were conducted on coral sand, and the effects of the water–cement ratio (w/c), permeability coefficient of coral sand (PCCS), and grouting pressure on the diffusion distance of the slurry, uniaxial compressive strength (UCS), and relative permeability coefficient (RPC) of the grouting cementitious body were analysed. In addition, the change trends in the slurry diffusion distance and slurry pressure was described, and the characteristics of the grouting cementitious body were analysed from three perspectives: UCS, RPC, and microstructure. The results showed that the slurry pressure increases nonlinearly with increasing grouting time and decreases nonlinearly with increasing slurry diffusion distance; additionally, UCS decreases with increasing slurry diffusion distance, with an “S”-shaped curve that is first concave and then convex, with an inflection point near L = 50 cm. [ABSTRACT FROM AUTHOR]

Polymer grouting materials are increasingly used in the filling of mine fissures. Unlike conventional inorganic grouting materials, the self-expansion of polymers adds complexity to their diffusion process within the crack. The objective of this research was to examine how polymer grouting material spreads in cracks at ambient temperatures and pressure. The investigation involved conducting grouting tests and performing numerical fluid simulation calculations using the finite-volume method in the computational fluid dynamics software, ANSYS FLUENT 2022 R1. The fluid volume approach was employed to determine the boundary between fluid and air and to ascertain the variation patterns of density in the slurry and the fracture system. This study applied the principles of fluid mechanics to investigate the patterns of variation in the physical characteristics of polymer grouting materials, including their density, pressure, flow velocity, and movement distance, during the diffusion process. The results indicated that the density of the polymer grouting material decreased exponentially over time throughout the diffusion process. With the increase in the grouting's volume, the grout's pressure and the permeable distance of the grout increased. The slurry's pressure near the grouting hole exceeded the other points' pressure. The physical parameters of the slurry were numerically simulated by ANSYS FLUENT 2022 R1 software, and the results were compared with the experimental data. After comparing the numerical simulation results with the test data, it was clear that the numerical simulation method was superior in accurately predicting the distribution pattern of each parameter of the polymer slurry during diffusion. The grouting volume, pressure distribution, and real-time change in the position of the flow of slurry could be efficiently determined through numerical calculation and simulated grouting tests. This work can offer valuable information for designing polymer grouting materials used in underground mine fissures. [ABSTRACT FROM AUTHOR]

Fault fracture zones are rock formations commonly encountered in submarine tunnels, and the diffusion mechanism of slurry in fault fracture zones has a crucial impact on submarine tunnel reinforcement. Based on the seepage equation of Bingham fluid, the tortuosity parameter, fractal theory, and variable viscosity equation are introduced to establish a spherical permeation grouting model of Bingham fluid considering the slurry diffusion path and viscosity time variability. The viscosity variation law with time of sulfur aluminate cement slurry under different seawater admixture conditions was tested, and the time-varying equation of viscosity of sulfur aluminate cement slurry was obtained by fitting. A set of fault fracture zone permeation grouting test system was developed, and a fault fracture zone grouting simulation test was carried out. The study shows that the diffusion distance calculated without considering the influence of slurry diffusion path and seawater is 1.63–1.91 times of the test value, which obviously overestimates the diffusion distance; the diffusion distance calculated with considering the influence of diffusion path and seawater is 1.06–1.35 times of the test value, which is in good agreement with the test value. The research results can provide some theoretical support for the design of grouting in seawater environment. [ABSTRACT FROM AUTHOR]

Traditional pressure grouting technology operates under steady pressure conditions, causing the grout to easily flow along preferential pathways. This results in uneven grout penetration and increased economic costs. This study proposes swirl grouting technology, which effectively improves this problem. To verify the effectiveness of swirl grouting, a fan-shaped blade tool was also proposed. The grout penetration performance was investigated through experimental studies. The length, width, height, weight, and uniformity of the grouted bodies produced by the swirl grouting method were compared with those produced by the steady pressure grouting method. Then, the mechanisms of swirl grouting were analyzed through transparent disc visualization experiments. The results demonstrated that, at different water–cement ratios, the swirl device increased the penetration length in the X, Y, and Z directions by 43.3%, 27.8%, and 45.8%, respectively, compared to the conventional straight device, and by 57.3%, 39.4%, and 55.6%, respectively, compared to the fan blade device. Moreover, the swirl device increased the weight of the grouted stone body by 54.9% compared to the conventional straight device and by 91.0% compared to the fan blade device, significantly enhancing filling efficiency. The uniformity coefficient of the swirl device permeation decreased by 56.6% and 51.0%, respectively, compared to the conventional straight device and the fan blade device, resulting in a more uniform grout distribution. The transparent disc visualization experiment further revealed the advantage of the swirl device in promoting the migration of fine particles, with a significant increase in average penetration distance and a penetration shape closer to a regular circle. The rotating flow path of the swirl device imparts additional rotational momentum and multidirectional penetration capabilities. The resulting turbulence accelerates the mixing of grout with the soil matrix, facilitating the migration of fine particles, expanding flow channels, and reducing flow resistance. This combination of effects enhances penetration efficiency and reduces energy loss. This study offers significant practical application value for improving engineering quality, construction efficiency, and reducing costs. [ABSTRACT FROM AUTHOR]

Rock fracture surfaces are normally rough, with upper and lower surfaces presenting obvious structural properties (i.e., matching or mismatching). In this paper, rock fracture was divided into shear and tensile fractures based on its mechanical origin. A test simulation system for grouting in rough fracture (tensile and shear fractures) with continuous pressure field monitoring was proposed. A series of grouting simulation tests were employed to evaluate the effect of fracture structural property, fracture surface roughness, and aperture on the characteristics of grout flow in the rough fracture. The results show that grouting pressure exhibited a trend of rapid increase followed by a slow increase with time during the grouting in the tensile and shear fractures. Grouting pressure increases with time in a smooth relationship for tensile fracture and a fluctuating upward relationship for shear fracture. The slurry pressure distribution along the penetration length exhibited a nonlinear attenuation trend. The attenuation degree of the slurry pressure was positively related to the fracture roughness and the roughness difference in the upper–lower fracture surface and negative with the fracture aperture. The potential filtration effect during the grouting process is an important factor affecting the grouting behavior in the rough fracture. [ABSTRACT FROM AUTHOR]

In response to the issue of resource depletion in an old gold mine, this study proposes 2 recovery schemes to effectively utilize shallow high-grade residual ore resources: one with reserved crown pillars and one without. The reserved crown pillar scheme includes options for 1 m and 0.5 m pillars, while the no reserved pillar scheme involves grouting consolidation with thicknesses of 5 m and 10 m. Based on the results of numerical simulations, the joint support method of partial crown pillar reservation and grouting consolidation of dry backfill materials was selected, with a reserved crown pillar thickness of 1 m and grouting consolidation thickness of 5 m. The process flow for residual ore recovery is detailed. By grouting and consolidating the existing loose backfill material in the upper voids of the trial stope, 4 500 1 ores containing 24 kg gold were successfully recovered, yielding an economic benefit of 6.619 8 million yuan. The success of this trial will continue to guide future residual ore recovery efforts in the enterprise. [ABSTRACT FROM AUTHOR]

Concrete-lined pressure tunnels have been widely used for water conveyance in pumped storage hydropower. With increasing internal water pressure, the tunnels are at higher risk of leakage, and the flow regime in the surrounding rocks is likely to transition from laminar to non-Darcian. Grouting has been considered as a cost-effective technique for controlling leakage in pressure tunnels, and an optimization design is usually needed to save the cost. This study proposes to use the Forchheimer's law-based model for design optimization of grouting for a concrete-lined tunnel in hard rocks subjected to 8 MPa internal water pressure. The hydraulic conductivity K of the surrounding rocks is determined from packer tests, and the excavation-induced K variation is characterized by an equivalent elasto-plastic model. The non-Darcian coefficient β is estimated from K with a calibrated power-law scaling. It is proposed that a proper design of grouting should be able to limit the region with significant non-Darcian effect within the grouted zone, in addition to other commonly-used criteria for leakage, seepage erosion and fracturing failure in the surrounding rocks. It is found that when the quality of grouting is controlled to a standard of K = 6 × 10−8 m/s, the optimal depth of grouting is 6 m in fractured rocks and 12 m in fault zones. Hydraulic tests and seepage measurements confirm that this design scheme has been well implemented at the site, and is effective in controlling pore pressure and leakage to the level predicted by the Forchheimer's law-based simulation. Highlights: The quality control criterion and depth of grouting are optimized with Forcheimer's law-based flow simulation for a pressure tunnel. It is proposed that significant non-Darcian flow effect should be limited within the grouted zone for optimization design of grouting. The optimized design scheme of grouting was implemented, and its effectiveness in leakage control is validated by seepage measurements. [ABSTRACT FROM AUTHOR]

With the increasing drilling depth of mines, the cross-complexity of fissures in the rock body, and the frequent occurrence of sudden water surges, polymer slurry, with its advantages of good permeability and strong water plugging, is increasingly used in mine grouting projects. Additional research is needed in order to further improve the grouting performance of polymer slurry, ensure the safety of mining operations, and reduce the grouting cost. In this paper, a polymer composite grouting material was prepared with diphenyl methyl diisocyanate, polyether polyol, and fly ash, as the main raw materials, with coupling agent and catalyst as auxiliary reagents. The performance of the composite grouting material in terms of mechanical properties, thermal stability, hydrophobicity, and bonding was explored. This study's findings indicated that incorporating fly ash led to notable enhancements in the thermal stability and water resistance of the polymer slurry. Furthermore, the introduction of fly ash notably raised the starting degradation temperature of the polymer, boosted the water contact angle of the composite material, and reduced the density and reaction temperature of the composite material. In addition, the catalyst and coupling agent as auxiliary reagents affected the polymers in terms of mechanical properties; in this paper, dibutyltin dilaurate was used as the catalyst, and organosilanes were used as the coupling agent. The catalyst successfully sped up the polymer's gel time, however, an excessive quantity of catalyst compromised the polymer's mechanical characteristics. The addition of organosilanes has a positive effect on the dynamic mechanical properties of the composites, fracture toughness, compression, bending, and bond strength. The research can offer a theoretical direction for creating polymer mixtures in mine grouting projects. [ABSTRACT FROM AUTHOR]

To improve shear capacity, as well as reduce on-site casting and steel consumption, a novel Y-shaped perfobond rib (Y-PBL) shear connector with ultra-high-performance concrete (UHPC) grout was proposed. The shear behavior of the Y-PBL shear connector was investigated by six groups of pushout specimens. Their failure modes, load–slip curves, load–separation curves, strain analysis, and shear transfer mechanisms were discussed. Subsequently, finite-element analysis (FEA) models were established to study the effect of parameters on the shear behavior of the Y-PBL shear connector, as well as to compare the shear capacity contributions with straight-shaped PBL (S-PBL) shear connectors. Analytical models were proposed to predict the shear capacity of the Y-PBL shear connector. The results reveal that the proposed Y-PBL shear connector has superior shear capacity and stiffness. The contribution of the perforating rebar is minor compared with the end-bearing effect of UHPC. The analytical predictions agree well with the experimental and FEA results. This study can be used to guide the design and application of the Y-PBL shear connector in steel-concrete composite bridges. [ABSTRACT FROM AUTHOR]

The warming trend presents a significant threat to the underlying permafrost. Talik formation is widely recognized as a significant mechanism of permafrost degradation. Our research indicates that the term talik has undergone a long period of development and gradually formed, referring to unfrozen layers in permafrost. The talik has already resulted in extensive damage to the infrastructure built in permafrost areas. Here, we provide a brief overview of the current research status of talik. Accurately identifying talik presents a significant challenge. However, by integrating multiple identification tools with technology, the precision of talik detection can be enhanced, resulting in more accurate results. This paper discusses the strengths and weaknesses of each approach. While numerical simulations can enhance our understanding of the development mechanism and evolution process of taliks, most simulations focus on the evolution of taliks beneath lakes. These simulations emphasize the impact of subpermafrost groundwater flow on the development of lake taliks and the surrounding permafrost thickness. Today, there is a scarcity of relevant studies about taliks in cold zone engineering. The presence of talik exacerbates the occurrence of permafrost-related subgrade diseases, which are chronic and irreversible. Additionally, it poses a threat to the stability of the subgrades and worsens settlement issues. Therefore, we have analyzed the causes and distribution characteristics of talik beneath the subgrade and proposed a novel measure for preventing and controlling it. This measure aims to enhance the long-term service performance of subgrade in permafrost regions. The modified polyurethane material is injected into the talik through grouting technology as a replacement. This material has low thermal conductivity, strong water resistance, and certain strength. It effectively improves the hydrothermal environment conditions necessary for talik formation, preventing the formation of new taliks or impeding their development. As a result, the subgrade performance is enhanced. [ABSTRACT FROM AUTHOR]

In response to the problem of deformation caused by surrounding construction disturbances in existing shield tunnels in soft soil areas, lateral horizontal grouting is often used. Based on an independently designed and developed lateral grouting experimental device, the mechanism of horizontal lateral grouting on the convergence deformation of the tunnel was determined. A three-dimensional finite-element analysis model was established to study the force and deformation characteristics of the tunnel tube sheet, and to verify the correctness of the model test results. The grouting remediation efficiency, η, was introduced to establish the relationship between the grouting volume and the convergent deformation. The results show that the tunnel tube sheet was subjected to asymmetric additional soil pressure along the ring direction, and asymmetric displacement occurred, which was most obvious on the grouting side. The additional moment distribution was symmetrical and spindle-shaped, and the peak bending moments mostly appeared in the arch roof, the arch bottom, and the arch whist. With a continuous increase in grouting volume, the efficiency of the grouting remediation decreased, and the two were negatively correlated. [ABSTRACT FROM AUTHOR]

Collapsibility significantly impacts the bearing capacity of pile foundations in loess areas. To improve the load-bearing capacity of piles, the pile-base postgrouting technique is widely used worldwide. However, there are still several related issues to be solved: the impact of loess collapsibility on the bearing capacity; the effectiveness of the pile-base postgrouting technique in enhancing the bearing capacity; and the diffusion pattern of the grout during the grouting process. To investigate these issues, this experiment utilizes a visual static pressure device combined with numerical simulation. According to the experiment, the maximum axial force and neutral point appeared to shift downward after grouting, resulting in a 17.5% increase in the bearing capacity of the pile foundation. Additionally, an increase in grouting pressure leads to a rise in both the number of shear cracks and the diffusion radius. As the permeability of the grout improves, the number of shear cracks and diffusion radii tend to stabilize after an initial increase. These discoveries enable a thorough analysis of the changes in side friction and base resistance of postgrouted piles in collapsible loess. Furthermore, they provide valuable references and guidance for the implementation of the pile-base postgrouting technique in loess areas. [ABSTRACT FROM AUTHOR]

After excavation of tunnels in interbedded surrounding rock, accidents such as rock peeling and arch crown collapse are prone to happen. In response to this issue, we first established an analysis model for the excavation of the interbedded surrounding rock tunnel through theoretical analysis, proposed corresponding failure criteria, and analyzed the reasons for the easy failure of the interbedded tunnel support structure based on the concept of principal stress difference. We also created interfaces in FLAC3D (version 6.0) software to restore the actual interbedded interface, verifying the effectiveness of principal stress difference in analyzing the deformation characteristics of the tunnel. Then, the instability forms of the interbedded surrounding rock tunnel were divided into two types, and effective support methods for the corresponding instability forms were proposed. Finally, based on the analysis results of the study, support was provided for the collapsed tunnel on site. A grouting large pipe shed was put to innovative use to support the tunnel arch waist, stabilizing the surrounding rock that is prone to shear slip and fracture at the upper part of the arch waist. The results indicate that the surrounding rock control effect is good. This study has a good reference value for on-site rapid construction and support design, and is of great significance for the instability prevention and control of interbedded surrounding rock tunnels. [ABSTRACT FROM AUTHOR]

A new grouting technique, double-row capsule grouting (DRCG), has been developed and implemented in practice. This grouting technique could effectively mitigate excavation-induced tunnel movement and ensure the serviceability of metro lines. However, its control mechanism and the factors that influence its performance are not fully understood. Based on a case history that utilized capsule grouting the precision of the numerical model is validated. Parametric studies are conducted to investigate the influence of the grouting location and volume on the tunnel deformation, bending moment, restoration ratio, and shear strain of the soil. In addition, a comprehensive comparison between the conventional grouting technique and DRCG is performed to illustrate the control mechanism of this innovative technique. The results could contribute to a better understanding of the factors that impact the performance of DRCG and an optimal application of DRCG, which facilitates its efficient implementation and further development in engineering. [ABSTRACT FROM AUTHOR]

The problem of seepage control is faced in the construction of large underground powerhouse cavern systems. To reduce leakage and improve the permeability stability of the surrounding rock, a complex seepage control system, including drainage hole arrays, drainage tunnels, and grouting curtains, was designed for the Wunonglong underground powerhouse caverns. In this study, we performed a seepage field numerical analysis of the Wunonglong underground powerhouse caverns system to optimize the seepage control system. A three-dimensional numerical model was established considering the complex seepage control system and the geological conditions. A steady seepage analysis method, with a variational inequality formulation, was adopted in order to calculate the long-term seepage field. A drainage substructure method was used to simulate the seepage behavior of the densely arranged drainage hole arrays. The seepage control effects of single and double grouting curtains were compared to determine a reasonable curtain layout scheme. The effect of the drainage system on the seepage control of the powerhouse caverns is further discussed. The findings offer reliable insights into the seepage behavior of underground powerhouse caverns and provide a reference for the design and construction of similar underground powerhouse cavern systems. [ABSTRACT FROM AUTHOR]

Excessive ballasted track deformations may occur during the railway operations due to poor load bearing capacity of the embankment (placed soil or natural ground) or the manifest accumulation of subsidence caused by the soil consolidation and the passage of trains. The principles of pressure grouting (or jet-grouting) technologies, used to create reinforcement elements for the rail trackbed stabilization, are presented, with reference to the specific construction condition on an existing and in-service railway track. A single-track railway, including the superstructure and substructure components, was modeled using the finite element method (FEM). Some soil stabilization options, based on the installation of grouted micropiles according to different layout configurations, were considered. The results of the numerical analyses, in the form of stress and strain behavior of the whole track structure, demonstrated that the use of jet-grouted micropiles is a rational and less expensive option, which can be installed on or close to the track, having positive effects on limiting the vertical deformations of the embankment without affecting the expected distribution of stress states in the embankment middle. [ABSTRACT FROM AUTHOR]