Grouting System Research Articles

Ternary mix design of grout material for structural repair using statistical tools

Repair is an indispensable part of the maintenance of structures over their lifetimes. Structural grouting is a widely used remediation technique for concrete components, trenches, mine subsidence, dam joints, restoration of masonry structures, and geological stabilizations. A structural grout system should be injectable in narrow spaces and hence include ingredients with finer particles. Ultrafine cements are ideal for these type of demanding grouts due to their superior properties compared to that of the less-expensive, but coarser ordinary Portland cement (OPC). Supplementary cementitious materials (SCMs) are often used to replace OPC clinker based binder in order to modify certain properties and to reduce costs. The most commonly used SCMs are fly ash (FA), and ground granulated blast furnace slag (GGBS). For various special applications microsilica (MS), and metakaolin (MK) are also used. Identifying the optimum replacement contents of OPC by SCMs are a challenge during the design of such grouts. The aim of this experimental study is to investigate the effect of the selected SCMs (FA, MS and MK) on the slump flow, time of efflux, viscosity, shrinkage, and compressive and flexural strength of ultrafine cement based grouts with constant water-binder ratio and superplasticizer content. The test program was formulated using Box-Behnken design principles. Maximum percentages of replacement with ultrafine cement was 6% by volume of cement for MS and 16% for FA, and MK. The results suggest that most investigated grouts have the potential to be used for structural applications. The appropriate quadratic models are then formulated through statistical tools and presented as response surfaces. The trends indicate that fly ash improves the rheological properties, whereas microsilica and metakaolin positively affect shrinkage and mechanical properties to some extent. Based on the influence of SCMs and priorities among the properties, Decision Matrix Analysis (DMA) is carried out to select the most suitable ones among the SCMs. The analysis suggests that microsilica and fly ash are more suitable as SCMs than metakaolin without affecting the properties.

Twin neighboring tunnel construction under an operating airport runway

Beijing Capital International Airport, as one of the busiest airports in the world, has three terminals and three runways. The middle runway lies between Terminal 2 and Terminal 3, and underground transportation is necessary to alleviate the congested surface traffic and reduce the impact of the surface traffic on the middle runway operations. As a result, twin neighboring tunnels, one each for passenger transportation and automobiles, passing underneath the operating middle runway were constructed. The section of the twin tunnels that was approximately 6 m under the operating runway was excavated using the sequential excavation method under the protection of a pipe-screen system. The elaborate installation of the pipe-screen system was performed using slurry pipe-jacking machines with an excavation diameter of 1020 mm. The annular gap between the excavation diameter and the outer diameter of the pipe was filled in time to reduce surface settlements. To conduct an information-oriented construction project, the real-time monitoring of the runway pavement surface with high-precision automatic total stations was employed during and after construction. With the monitored results, in-pipe grouting was performed when necessary to decrease the runway settlements. The undercrossing construction was completed as scheduled, and the final settlements of the runway were controlled within the predefined allowable settlement. The airport continued all operations without any interruptions. The success of crossing under the operational runway of the twin tunnels lies in the use of the large-diameter pipe screen, the well-controlled excavation of the twin tunnels, the installation of the high-precision and automatic runway movement measurement system and, most importantly, the employment of the in-pipe grouting system.

A review of jet grouting practice and development

The jet grouting technique was originally initiated in the UK and progressively developed following the needs for larger geometries, ease of implementation, economic rationality, and better mechanical properties. This paper presents a comprehensive review of the development and practice of jet grouting through some fundamental concepts and relevant case studies. Subsequently, a laboratory testing program is performed to investigate the factors affecting the efficacy of the twin grouting system. The principal objective of this study is to define the suitable conditions for the jet grouting efficacy regarding economic rationality as well as quality control. For the first phase, a particular emphasis is placed on the properties of jet columns, site geological conditions, implementation methods, and the justification of each selected treatment option, while the second phase mainly focuses on the unconfined compressive strength (UCS) tests. It follows that the mono-fluid jet grouting system presents a valuable flexibility in dealing with complex configurations; yet, the double- and triple-fluid systems are more indicated for cases of mass treatments for which large portions of space must be treated and overlapping is fundamentally important for the reliability of the treatment. Furthermore, it was established that the efficacy of the twin-jet method primarily relies on the proper adequacy of some critical parameters, namely, the cement content, the water-cement ratio, and cement slurry-water glass ratio. In spite of some uncertainties inherently related to the technique, the UCS test represents the quintessential laboratory index for evaluating the mechanical properties of grouted elements, deriving jet grouting efficacy and the economics of jet grouts.

Factors affecting the performance characteristics of cementitious grouts for post-tensioning applications

In grouted post-tensioned (PT) systems, cementitious grouts are supposed to completely fill the interstitial spaces between the strands and act as the ‘last line defence system’ against corrosion. However, use of poor quality grout materials and grouting practices result in voided grout systems, ultimately leading to premature failure of tendons in many bridges around the world. To ensure an intact system, the grout must have excellent fresh properties, in particular the flow properties. Such high-performance grouts are not available in many developing countries, where grouting for post-tensioned structures is still a nascent technology. In this research, a two-stage test program was carried out to evaluate the fresh and hardened properties of seven commercial grouts, which includes three Pre-Packaged Grout mixes (PPG); three Site-Batched Grout mixes (SBG) and one standard Ordinary Portland Cement grout mix (PCG). Further, one PPG mix and SBG mix were chosen and their properties were evaluated for three levels of mixing speed and two ambient temperature conditions. Fresh properties such as wet density, efflux time and its retention, standard bleed, wick-induced bleed and pressure bleed, as well as set/hardened properties such as setting time, compressive strength and volume change were evaluated. Three batches of grout were tested for each grout material, to ensure reliability of results. The influence of binder fineness on the performance of grouts was also evaluated. The study serves as a strong evidence in substantiating that the most commonly used grout materials for PT system in developing countries, fail to meet the standard requirements and even the manufacturer’s own specifications. It is also found that the performance of the grout is influenced by mixing speed, ambient temperature, and fineness. The study emphasises that the evaluation of the grout behaviour under simulated field conditions is essential to ensure void free and durable PT systems.

Could magnetic properties be used to image a grouted rock volume?

In this study, we show that development of a detectable permeation grouting system is feasible, based on the addition of magnetic materials to the grout, specifically, magnetite. A magnetic-based detection system is selected for development because unlike other previously trialled detection methods, magnetic fields are detectable over large distances within the subsurface, and importantly, attenuation of the magnetic field is not strongly dependent on the material properties of the surrounding rock. To test the conceptual feasibility of such a system, a finite element based numerical model is developed to simulate the magnetic field anomaly that can be achieved by the addition of magnetic materials to a cement grout. The model is verified against an analytical solution and then used to predict the magnetic field generated by a grouted cylinder of rock, assuming a fixed percentage of uniformly distributed magnetic minerals, and a central injection borehole. Two field trials are conducted to verify the detectable grouting concept, the first using a walkover survey that allowed mapping of the magnetic signal in 2D. The second is designed to mimic magnetic field measurements from a borehole monitoring array, with a single central magnetic grout block (representing the grout close to the injection point). Results of the two field trials show that the magnetic cement is detectable, even when the background magnetic noise within the surrounding soils/rocks is significant. A good agreement is obtained between the measured and the modelled magnetic anomaly. This research opens the door to the development of a ‘detectable’ magnetic grouting system, that can increase confidence in the integrity of grouted rock volumes and reduce the inefficiencies currently present in the grouting industry, enabling in-situ real-time optimisation of grouting campaigns.

A self-learning propotional–integral–derivative control of grouting pressure using the back-propagation model

For the security of grouting process of dam foundation, grouting pressure control is one of the most important problems. In order to avoid dangerous grouting pressure fluctuation and improve the control precision, a feedback propotional–integral–derivative control method was presented for the whole grouting system. Because the grouting pressure is affected by many factors such as grouting flow, grouts density, and geological conditions, the parameters of propotional–integral–derivative must be tuned. In this article, the adaptive tuning method is presented. The back-propagation artificial neural networks model was proposed to simulate the grouting control process, and sensitivity analysis algorithm based on orthogonal test method was adopted for the selection of input variables. To obtain the optimal propotional–integral–derivative parameters, an iteration algorithm was used in each sampling interval time and the discrete Lyapunov function of the tracking error. The simulation results showed that self-learning propotional–integral–derivative tuning was robust and effective for the realization of the automatic control device in the grouting process.

SEGREGATION TEST OF THE OFF-SHORE WIND TURBINE JACKET FOUNDATIONS MADE BY FREE FALL POURING

One of the major concern of wind farm offshore is the type of wind turbine foundation to be installed. When it comes to talk about offshore installation of pre-piled fixed jacket foundations (3-4 legs), one of the most critical activities to be performed by the installer is the grouting operation. For currently wind turbines size, are being installed on the new wind farms developments, pre-piling jacket installation is a very extended alternative used and we could be talking about piles with easily 30m length and between 2-3 m diameter which are drilled into the seabed until only 4-5 m come out the seabed line. Once piles have been installed into the seabed it comes the time to proceed with jacket legs installation. For this operation, heavy lift vessel is spready used due to dimension and weight of these structures and once structure has been guide-lifted over the sea level it starts coming down into the sea until it´s fixed into the already installed piles. Next step is to grouting-secured together both structures (pile and jacket) pouring grout, throughout the already pre-installed grouting lines into the lower part of the jacket leg, along the ring around between jacket leg and piles border as well as the gap between the stabbing cone (being the sharp shaped ending up of the jacket leg) and the ground (we´re usually talking about mm distance). Due to complexity of the overall manoeuvre as well as required precision not only for the grout system but for the right parameters should be considered for pouring in order to ensure the grout correctly into the pile/jacket annulus without segregation or other undesirable effects occurring a mock-up test was carried out. The proposed and analysed method defines a protocol that could be used and repeated for others offshore windfarms that are planned to be installed in the future over pre-pilled foundations. Running a grout wall test based on protocol described on this paper prior to offshore grout operations will guarantee mix of grout and lub is in line with grouting foundations requirements, saving pumping grout time and therefore vessel stand by costs as well as money savings for grout exceeds, avoiding segregation problems could lead up to in worst case to foundations removal with massive vessel standby costs for reparation of the entire installation foundation operation.

Permeation grouting and excavation at Victoria station, London

Paid area link 6 (Pal6) underpass, a crucial tunnel connection of London Underground's Victoria station upgrade project, was engineered within notoriously difficult sub-artesian granular River Terrace Deposits (RTD) immediately below the Victorian-age District and Circle line masonry tunnel, a structure highly sensitive to ground displacements. Due to the proximity of the overlying operational railway, the consequences of ground movement were of very high risk. Historic tunnel construction in the heterogeneous RTD had limited success with permeation grouting, and face losses and instabilities occurred. For the case of Pal6, the railway tunnel overhead magnified the difficulties. Permeation grouting still remained the most feasible stabilising option, but only with significant improvements in both grouting technique and grout types. A low-risk tunnelled solution, using a bespoke and sophisticated construction approach, enabled safe continuous excavation within the severely restricted structural constraints. Successful tunnelling demanded: complete sequence recovery of the RTD for accurate soil characterisation for design of the grouting system; caution with permeation grouting; appropriate grout selection to promote permeation without claquage (uncontrolled fracturing by grout with its consequent irregular distribution), thus precisely targeting discrete zones; uniform treatment; and observational control by monitoring real-time ground movements.

自动润滑注浆系统在长距离顶管隧道施工中的应用

自动润滑注浆系统在长距离顶管隧道施工中的应用

Use of fly-ash slurry in backfill grouting in coal mines

Cave backfill grouting implies grouting of the caving rock mass prior to it being compacted. The filling materials strengthen the caving rock and support the overlying strata to achieve the purpose of slowing down the surface subsidence. The broken roof will fail and collapse during mining operations performed without appropriate supporting measures being taken. It is difficult to perform continuous backfill mining on the working face of such roofs using the existing mining technology. In order to solve the above problems, fly ash and mine water are considered as filling materials, and flow characteristics of fly-ash slurry are investigated through laboratory experiments and theoretical analyses. Laws governing the diffusion of fly-ash slurry in the void of caving rock masses and in the void between a caving rock mass and a basic roof are obtained and verified. Based on the results obtained from the above analyses and actual conditions at the Zhaoguan coal mine, Shandong Province, China, a cave backfill grouting system of the hauling pipeline is developed and successfully tested at the 1703 working face in the Zhaoguan coal mine. The results demonstrate that a filling rate of 43.46% is achieved, and the surface subsidence coefficient of the grouting process is found to be 0.475. Compared to the total caving method, the proposed system is found to achieve a reduction rate of 40.63%. This effectively helps in lowering the value of the surface subsidence coefficient. Fly ash and mine water, considered as primary materials in this study, also play a significant role in improving the air quality and water environment.

Shear Performance of Fiber-Reinforced Cementitious Composites Beam-Column Joint Using Various Fibers

Increasing demands of reinforcement in the joint panel are now requiring more effective system to reduce the complicated fabrication by widely used precast system. The joint panel is responsible to keep the load transfer through beam and column as a crucial part in a structural frame that ensures the main feature of the whole structure during earthquake. Since precast system might reduce the joint panel monolithic integrity and stiffness, an innovation by adding fiber into the grouting system will give a breakthrough. The loading test of precast concrete beam-column joints using FRCC (Fiber-Reinforced Cementitious Composites) in joint panel was conducted to evaluate the influences of fiber towards shear performance. The experimental factor is fiber types with same volume fraction in mortar matrix of joint panel. Two specimens with Aramid-fiber and PP-fiber by two percent of volume fraction are designed to fail by shear failure in joint panel by reversed cyclic testing method. The comparison amongst those experiment results by various parameters for the shear performance of FRCC beam-column joints using various fibers are discussed. Preceding specimens was using no fiber, PVA fiber, and steel fiber has been carried out. Through the current experimental results and the comparison with previous experiment results, it can be recognized that by using fibers in joint panel was observed qualitatively could prevent crack widening with equitable and smaller crack width, improved the shear capacity by widening the hysteretic area, increased maximum load in positive loading and negative loading, and decreased the deformation rate. Elastic modulus properties of fiber are observed to give the most impact towards shear performance.

Cure-on-Demand Acrylamide Grout Using Frontal Polymerization

AbstractAn acrylamide-based chemical grouting system has been developed that allows users to initiate the curing process on demand. After heating a localized area, the curing reaction propagates th...

Experimental and Analytical Investigation of Steel Reinforced Grout (SRG) Strengthened Masonry Panels

This paper illustrates the results of experimental and analytical investigation carried out on masonry panels built by grey clay brick (GCB) from the Lingnan Region, China, reinforced with externally bonded Steel Reinforced Grout (SRG) system. The experimental program involves diagonal compression tests on two unreinforced and two double side reinforced panels. The main outcomes of the experimental tests include load-displacement response, stiffness, load capacity and failure mechanism. The results show that the contribution of the strengthening system to the increase of the load carrying capacity and ductility. Finally, analytical model is proposed and compared with experimental results.

Round Robin Test on tensile and bond behaviour of Steel Reinforced Grout systems

Mortar-based reinforcements are an innovative solution for retrofitting existing structures that combine effectiveness, compatibility, and sustainability. Despite the recent spreading of field applications, there is still insufficient knowledge on their fundamental mechanical properties, and a regulatory gap for experimental procedures and design criteria. A Round Robin Test initiative was organized by the Rilem TC 250-CSM (Composites for the Sustainable strengthening of Masonry) to investigate the tensile and bond behaviour of mortar-based composites with basalt, carbon, glass, polyparaphenylene benzobisoxazole (PBO), aramid and steel textiles. This paper presents the tests carried out on Steel Reinforced Grout (SRG) systems, comprising three textile and four mortar types, supplied by three producers. Ten laboratories from Italy, Poland and Portugal were involved for a total of 150 tests, including direct tensile tests on textiles and composites, and single-lap bond tests on masonry substrate. The influence of the layout of the textile, the mechanical properties of the mortar matrix, the manufacturing and curing conditions, as well as the testing setup and instrumentation, is discussed to contribute to the optimization of the reinforcement systems and to the development of recommendations for laboratory testing. Finally, results are combined to derive engineering parameters for qualification and design purposes.

Experimental tests on FRCM strengthening systems for tuff masonry elements

Composite materials consisting of high-strength fibers embedded in inorganic matrix (Fiber Reinforced Cementitious Mortar materials, FRCM) are becoming more and more widespread as strengthening technique for existing masonry structures because of the higher compatibility of the inorganic matrix with the masonry supports compared with the epoxy adhesives, the lower sensitivity to debonding phenomena at the interface, and the ‘grid’ configuration of the reinforcement, particularly suitable for strengthening bi-dimensional elements. Conversely, the use of lime or cement-based mortar implies that attention has to be payed also to the bond behavior between the fibers and the matrix, since sliding phenomena and cohesive failures in the mortar frequently occur. Thus, for the FRCM materials the knowledge of the bond behavior both at the fiber/matrix and at the composite/substrate interface is fundamental to correctly assess their performance as strengthening of masonry elements.The experimental tests discussed in this paper show different aspects of the bond behavior of the FRCM materials in order to validate an experimental methodology for such a strengthening technique. In particular, tensile tests on coupons made of different FRCM materials were carried out in order to investigate the interaction between fibers and mortar and the bond strength at the fiber/mortar interface. Then, the bond behavior between different FRCM systems and a masonry substrate made of Neapolitan yellow tuff was investigated by shear bond tests according to a single push-pull set-up. The experimental tests were carried out on three types of fibers embedded in cement-based grouts: a balanced glass grid (G-FRCM, i.e. Glass Fibers Reinforced Cementitious Mortar system), and two types of unidirectional fabric made of steel cords (SRG, i.e. Steel Reinforced Grout system) with different density. The readings obtained with traditional measuring instruments were integrated with those obtained by the Digital Image Correlation (DIC) technique.

Adaptive control system for grouting pressure stability based on fuzzy algorithm

To solve the issues during grouting, such as low accuracy in grouting pressure detection, lack of stability, and tedious manual control work for pressure, a new adaptive control system for grouting pressure stability was designed based on single-chip technology, sensor technology, and automatic control technology for online detection and stability control of grouting parameters. The grouting simulating test bed was designed based on the actual grouting pipeline system in the project. The experiment tests were conducted by adjusting the following parameters: flow characteristics of the grouting pump, instantaneous flow pulsation variation law, and P-Q (pressure-quantity of flow) performance. Subsequently, the damping characteristics of valve under different pressures and pipeline hydraulic power balance control equations were proposed. Based on the experimental tests, whereby the opening of perturbation valve V01 was regulated and changed to create pressure fluctuations, changes at different pressure values are obtained. On the basis of fuzzy control algorithm tuning the parameters Kp, Ki, and Kd of Proportion, Integration, Differentiation (PID), the PID controller that varied the regulating signal and maintained a given pressure in grouting system was afforded. Finally, the reliability of the adaptive control system for grouting pressure stability was demonstrated by the application in rock mass curtain grouting project. The accuracy of automatic pressure control was maintained within 5% of the set value, and the control response time was 2 s to 3 s, thereby showing the high accuracy, fast response, and good stability of the designed system.

Fatigue and Flexural Behavior of Reinforced-Concrete Beams Strengthened with Fiber-Reinforced Cementitious Matrix

AbstractThe need for repair and rehabilitation is a crucial issue today in order to maintain a safe and efficient transportation network. One of the most recent innovative composite materials that has been proposed to the market is a fabric reinforced cementitious matrix (FRCM) strengthening system. This system consists of two components: a structural reinforcement mesh and a cementitious matrix. The structural reinforcement mesh consists of a polyparaphenylene benzobisoxazole (or PBO) fiber composite, while the cementitious matrix is a nontoxic grout system based on portland cement with a low dosage of dry polymers. The first aim of this study was to evaluate the fatigue resistance of reinforced concrete (RC) beams strengthened with FRCM under fatigue loading and postfatigue flexural strength to failure. The second aim was to investigate the durability performance of the FRCM after exposure to environmental conditioning including temperature, moisture, and sustained stress. All of the beam specimens exam...

Flexural Strengthening of RC Slabs with SRP/SRG: An Experimental-Numerical Comparison

Steel reinforced polymer (SRP) and steel reinforced grout (SRG) systems have emerged as promising and cost-effective technologies for the external strengthening of RC structures. An experimental campaign was recently performed to investigate the effectiveness of SRG/SRP systems in increasing the flexural strength of RC slabs. Test results are herein used to validate a Fiber based finite element code developed with the aim of simulating the flexural behavior of SRP/SRG strengthened RC beams/slabs. The model provides an accurate prediction of the cross-sectional response by explicitly modeling each constituent, their position inside the discretized cross-section, and their nonlinear behavior. The satisfactory comparison between numerical predictions and experimental results assessed the accuracy of the developed code.

Numerical analysis of submerged flows for jet grouting

The diffusion of turbulent submerged flows is studied to understand the core mechanism of jet grouting and to enhance the efficiency of treatments. Because of the particularly high speeds, experimental measurement is very difficult, and theoretical relationships found at lower velocities are misleading. The velocity distribution and its relationship with the injection parameters are then obtained, combining experiments, numerical calculations and theory. A numerical finite-volume model simulating the turbulent propagation of submerged jets is initially calibrated using a set of experimental data reported in the literature. This model is used to perform a parametric study, varying the injection parameters within the typical range of jet grouting and evaluating their influence on the velocity distribution. The results of numerical calculations are finally interpreted with a mathematical function relating the velocity distribution to the nozzle diameter, inlet velocity and fluid composition. The effect of insulating the injected fluid with a coaxial air jet is also investigated, to clarify the principles of double- and triple-fluid jet grouting systems.

Steel reinforced grout systems for the strengthening of masonry structures

Steel Reinforced Grout (SRG) systems, comprising Ultra High Tensile Strength Steel cords embedded in mortar matrix, are increasingly used for the strengthening of existing structures. Their mechanical properties, however, still need to be fully investigated in order to provide reliable values of tensile and bond strength, strain and stiffness for design purposes. With this aim, four SRG systems made of two textiles combined with two mortars were tested. The durability of the textiles, the tensile behaviour of the composites and the shear bond performance on different substrates, including historic and modern bricks and tuff units, were investigated. The role of the layout of the textile, the characteristics of the matrix and the properties of the substrate are discussed. Finally, test results are combined to derive engineering design parameters for different field applications.