Grout Injection Research Articles

Toward Workable and Cost-Efficient Monitoring of Unstable Rock Compartments with Ambient Noise

Ambient Vibration-Based Structural Health Monitoring (AVB–SHM) studies on prone-to-fall rock compartments have recently succeeded in detecting both pre-failure damaging processes and reinforcement provided by bolting. The current AVB–SHM instrumentation layout is yet generally an overkill, creating cost and power issues and sometimes requiring advanced signal processing techniques. In this article, we paved the way toward an innovative edge-computing approach tested on ambient vibration records made during the bolting of a ~760 m3 limestone rock column (Vercors, France). First, we established some guidelines for prone-to-fall rock column AVB–SHM by comparing several basic, computing-efficient, seismic parameters (i.e., Fast Fourier Transform, Horizontal to Vertical and Horizontal to Horizontal Spectral Ratios). All three parameters performed well in revealing the unstable compartment’s fundamental resonance frequency. HHSR appeared as the most consistent spectral estimator, succeeding in revealing both the fundamental and higher modes. Only the fundamental mode should be trustfully monitored with HVSR since higher peaks may be artifacts. Then, the first application of a novelty detection algorithm on an unstable rock column AVB–SHM case study showed the following: the feasibility of automatic removing the adverse thermomechanical fluctuations in column’s dynamic parameters based on machine learning, as well as the systematic detection of clear, permanent change in column’s dynamic behavior after grout injection and hardening around the bolts (i1 and i2). This implementation represents a significant workload reduction, compared to physical-based algorithms or numerical twin modeling, and shows better robustness with regard to instrumentation gaps. We believe that edge-computing monitoring systems combining basic seismic signal processing techniques and automatic detection algorithms could help facilitate AVB–SHM of remote natural structures such as prone-to-fall rock compartments.

Use of Nanosilica for Increasing Dune Erosion Resistance during a Sea Storm

Dune recovery interventions that integrate natural, sustainable, and soft solutions have become increasingly popular in coastal communities. In the present study, the reliability of an innovative non-toxic colloidal silica-based solution for coastal sand dunes has been verified for the first time by means of laboratory experiments. An extensive experimental campaign aimed at studying the effectiveness of the use of nanosilica has been conducted in the 2D wave flume of the EUMER laboratory at the University of Salento (Italy). The study was first based on a horizontal seabed and then a cross-shore beach-dune profile was drawn similar to those generally observed in nature. Detailed measurements of wave characteristics and observed bed and cross-shore beach-dune profiles were analyzed for a wide range of wave conditions. In both cases, two sets of experiments were carried out. After the first set of experiments performed resembling the native conditions of the models composed with natural sand, the effects of the injection of the mineral colloidal silica-based grout were investigated. The observations show that mineral colloidal silica increases the mechanical strength of non-cohesive sediments reducing the volume of dune erosion, thus improving the resistance and longevity of the beach-dune system.

Preliminary Investigation of the Mechanical and Physical Properties of Natural Hydraulic Lime Grouts with Nano-Silica

Natural hydraulic lime-based grouts are often used in the structural consolidation of old stone masonry walls, mainly to re-establish the monolithic behaviour of masonry constructions. To ensure an adequate grouting operation, it is essential to have good fresh and hardened grout properties. The motivation of the present study was to examine the fresh and hardened properties of natural hydraulic lime grouts with nano-silica (NS) and silica fume (SF). The contribution of these materials and the dosage of a high range water reducer admixture (HRWR) were investigated on the rheological properties, water capillarity, open porosity and mechanical strength of injection grouts. The effects on rheology were analysed through plastic viscosity and yield stress. The results indicated that, even for reduced NS content, an increase in plastic viscosity and yield stress occurred, which required a higher HRWR content in order to not compromise the grout’s rheological performance. The results also showed that, when NS and SF were combined, a beneficial joint effect occurred, resulting in a substantial and positive change on the mechanical strength and microstructure of the hardened injection grouts. Taguchi’s method was used to optimize the grout’s formulation and to fulfil the required performance concerning the fresh and hardened state.

Effects of grout sleeve defects and their repair on the seismic performance of precast concrete frame structures

Precast concrete frame structures with grouted sleeve connections are widely used. An experimental study was conducted investigating the seismic performance of precast concrete frame structures having backflow defects in their grout sleeves. Repair of such defects is also demonstrated using a simple grout injection technique. Four two-storey precast concrete frame structures having grout sleeve connections in their columns were designed and tested under reversed cyclic loading. The performance of frames having no grout defects and those with defects and repaired defects is described in terms of failure modes, hysteresis characteristics, load-carrying capacity, ductility and energy dissipation capacity. The results indicate that the plastic collapse mechanism of the frames remains unchanged, the performance is affected by the presence of the grout sleeve defects. Despite the defects only reducing the capacity of one of three columns in the frame either 6% or 19%, the effect on the global behavior of the frame was evident in terms of reduced capacity, stiffness, ductility and energy absorption. Injecting grout into defective grout sleeves restored their capacity, and that of the frames, to a defect-free condition.

Non-linear spring model for backfill grout-consolidation behind shield tunnel lining

This study presents a non-linear spring model for modelling the backfill grout consolidation behind shield tunnel lining. Two important parameters, i.e. the time-dependent grout pressure decay induced by consolidation and the grout-cake thickness, were derived through a non-linear spring model and continuity equation. The proposed non-linear spring model for backfill grout consolidation was validated based on vertical pressure and strain relationships determined from an oedometer test. The derived equations were applied to the Groene Hart Tunnel (GHT) project. The results show that the calculated grout pressures agree well with the measured values. The calculated grout-cake thicknesses are in good agreement with the measured values. Two key factors influencing the grout consolidation are discussed: grout diffusion into the soil, and the initial distribution of the grout injection pressure. It is found that grout diffusion into the soil can dissipate the grout pressure quicker than grout consolidation. The distribution of the initial grout injection pressure dominates the final distributions of the grout pressure/grout cake around the tunnel lining.

The Effect of Soil Porosity and Geopolymer Viscosity on Spreading Grouting in Weathered Clay Shale

Fly ash geopolymer is a potential material for the stabilisation of clay shale. Therefore, this research determines the effect of soil porosity (n), binder activator ratio (f/a), and geopolymer viscosity on the injected grout volume (Vi ) and soil-grout column of weathered clay shale. The research was carried out using fly ash as a geopolymer binder, dissolved in Na2SiO3 and NaOH(10M) with an activator ratio of 1:1. The binder activator ratios were 0.50, 0.75, 1.0, and 1.25, with injection applied in the compacted clay shale using three dry densities corresponding to the porosity of 0.42, 0.48, and 0.54. Furthermore, a cylindrical specimen with 46 mm diameter and 100 mm height was used to carry out this test. A hole with a diameter of 12 mm and 80 mm depth was bored at the centre of the specimen to model a fracture grouting method, which was injected with the geopolymer by applying a pressure of 100 kPa for 20 minutes. The research found that the higher the binder activator ratio, the lesser the viscosity obtained; therefore, the grout easily penetrated the pores between the soil particles. As a consequence, more volume of geopolymer could be injected in soil. Binder activator ratio lesser than 0.75 was ineffective for the injection method, and binder activator ration between 1.00 - 1.25 was recommended for the grouting injection method. A new equation to determine the grout diffusion was proposed based on this experiment, as written in the equation .

Case Study on Applications of Lime–Cement Grouting to Strengthen Soil Characteristics

Formulating solution to obtain the required engineering properties by means of stabilizing the soil for placing infrastructural unit without undergoing large settlement, grouting is widely used restoration method for improving the relative density of the soil strata. This paper has analyzed two case scenarios about soil stabilization to accommodate reinforced cement concrete (RCC) structure to facilitate production units. Considering the soil characteristics and to avoid further collapse of the nearby establishment, injecting lime–cement composition to strengthen the loosen earth bearing capacity at certain depth has been followed. Accordingly, researchers have shown to mend on the discrepancy happened in both cases regarding strengthening of disturbed soil strata up to 2 to 2.5 times with respect to Standard Penetration Test-Number of Blows (SPT-N) values after carrying out pre- and post-dynamic cone penetration tests (DCPT) up to an average depth of 6 to 6.5 m from finished ground level (FGL), by using of grout injection procedure. Following methodology has been emanated and after conducting several trials resulted in appreciable improvement in soil consistency. Researchers believe that the study will be comparatively more suitable for improving problematic soils in South-Asian continent. In both cases, desired soil bearing capacity has been attained in most economical way and within stipulated time frame.

Non-Dispersive Anti-Washout Grout Design Based on Geotechnical Experimentation for Application in Subsidence-Prone Underwater Karstic Formations.

A new non-dispersive, anti-washout grout consisting of ordinary Portland cement, slag, superplasticizer, and methylbenzyl cellulose is proposed herein for the treatment of open karst, jointed and fractured rock, open-work gravel, and permeable sediments. A series of laboratory experiments were performed to design an anti-wash out grout suitable for grout injection of coarse aggregates depicting partially and open-jointed saturated rock mass and grouting concrete aggregates for underwater construction. The Taguchi orthogonal array was used to obtain nine different grout mix ratios. A total of four variables were considered, each with three different levels of the water–cement ratio, slag, and dosage of additives such as the superplasticizer and methyl benzyl cellulose. The laboratory determination of grout characteristics recording of mini slump, temperature, pH, visual assessment of grout dispersion, bleeding, and initial setting time and as well as uniaxial compressive strengths and permeabilities of the hardened grout samples were tested. To evaluate the suitability of the grout mixes, an analysis of variance was used for factor analysis and Grey relational analysis (GRA) was used to determine the optimal grout mix design. Based on the GRA, the following levels of the factors afforded the best results: water level 1 (0.3%), SP level 3 (0.01%), methylbenzyl cellulose level 2 (0.002%), and slag level 3 (0.1%). This paper describes the research methodology, detailed research observations, and analyses involved in designing the appropriate concrete mix. Based on the conclusions, relevant commendations regarding the suitability of grout testing equipment and grout mix designs are presented.

Low-velocity impact response of novel prepacked expanded clay aggregate fibrous concrete produced with carbon nano tube, glass fiber mesh and steel fiber

Recent researches reported that expanded clay aggregate in concrete leads to a notable reduction in strength properties. Nevertheless, the impact response of PEAFC comprising expanded clay aggregate (ECA), multi-walled nano-carbon tubes (MWCNT), steel fiber (SF) and glass fiber mesh (GFM) is still unexamined. It is interesting to draw a sound conclusion regarding the impact response of concretes comprising these four materials. Prepacked expanded clay aggregate fibrous concrete (PEAFC) is a novel type of environmentally sustainable concrete. The development process of PEAFC comprises the following two crucial stages. Firstly, the expanded clay aggregate and fiber are prepacked into the framework in the form of a natural skeleton, followed by grout injection. The skeleton is filled with cement grout comprising multi-walled nano-carbon tubes (MWCNT) obtaining a novel PEAFC. This research investigates the impact response of PEAFC through the drop weight impact test. For this study, forty-one PEAFC mixtures were prepared and divided into five groups. The effect of GFM with different layers and diameters inserted between the two concrete layers was accompanied by incorporating 0.2% of MWCNT and 2.5% dosage of SF. All specimens were tested against drop weight impact according to the guidelines of ACI Committee 544. The studied parameters were the compressive strength, number of the impact causing first crack and failure, impact energy at first crack and failure in addition to impact ductility. Additionally, scanning electron microscopy was utilized to assess the cement grout's microstructural features. The results showed that increasing the diameter of the GFM in between the concrete layers covers a larger crack projection area, which better enhances the crack arresting potential and results in higher impact energy. The GFM diameter increase from 50 mm to 150 mm increased the cracking and failure impact numbers by 49 to 60% and 117 to 152%, respectively. The average percentage improvements in cracking and failure impact numbers due to SF were estimated to be 162 and 670%, respectively. Thus, the SF shared 71 to 96% of the total developments in impact resistance of all mixtures compared to the reference mixture. The addition of 0.2% of MWCNT could adequately fill the nano-pores and nano-cracks resulted in a denser cement grout matrix. The steel fiber was found to be the reinforcement type that leads to the highest improvement contribution in the impact resistance of the tested PEAFC. Despite the use of light weight aggregate, the combined action of GFM, MWCNT and SF could enhance the impact strength of PEAFC. The outcome of this research is to deliver benchmark information for further research work on PEAFC under impact loading.

Potential of a repair system for grouted connections in offshore structures: Development and experimental verification

Grouted connections are intensively used in offshore rigs, platforms as well as jacket and monopile offshore wind turbine structures. Being located in remote offshore conditions, these connections can experience considerable adverse loading during their lifetimes. Degradation was reported inside similar connections, which were installed in the last three decades. Grouting in the offshore sites may often be proven difficult, which eventually leads to reduced load-bearing capacity of connections in the long run. Thus, repair and rehabilitation of such connections should be planned ahead to minimize operational delays and costs. In this study, scaled grouted connections were manufactured using a novel mould, whose integrity were monitored using digital image correlation (DIC). The connections were loaded under static load to visualize the main failure pattern using distributed fibre optic sensors and acoustic emission (AE) analysis. Grouted connections were then repaired using a cementitious injectable grout. The effectiveness of the grout injection was monitored using dye penetration technique. Finally, specimens are reloaded to identify the potential of such repair for grouted connections.

Experimental and Numerical Study on the Permeation Grouting Diffusion Mechanism considering Filtration Effects

Permeation grouting estimation is important for the design of grouting engineering. Filtration effects and rheological behavior play a key role in permeation grouting diffusion of cement-based grouts. To better understand the effect of filtration and grout rheological behavior on the grouting diffusion mechanism, one-dimensional permeation grout injections in sand columns under constant flow rate were performed by a self-developed experimental procedure. Experimental results showed that there were dramatic variations in rheological parameters and porosity along the diffusion distance. However, the rheological parameters changed slightly with time for each position. Based on the experimental results, a numerical model considering the filtration effect and grout rheological behavior was established to describe the mechanism of grout flow in porous media. In addition, numerical solutions from the proposed model are compared with the experimental results. The comparative results showed that the proposed numerical method can match the laboratory tests well. Finally, the effects of the grout flow velocity and the water/cement ratio of the grout on the diffusion mechanism are also discussed.

Out-of-plane testing of masonry walls retrofitted with oriented strand board timber panels

Several studies on different techniques can be found on retrofitting existing unreinforced masonry (URM) walls using varieties of materials ranging from reinforced plaster, grout and epoxy injection to fibre-reinforced polymers. Still, there is a significant lack of experimental data that consider using a material such as oriented strand board (OSB) timber panels, which can be easily sourced around the globe, and are considered to be economical and sustainable. Hence, this paper presents the first stage of a multi-phase experimental investigation into the possibility of retrofitting URM walls using OSB panels. An experimental programme with full-scale testing is expensive, therefore small-scale testing such as the approach presented here is ideal to provide insight when proposing a new retrofit technique. In this paper, flexural strength in the form of four-point bending tests has been obtained on three plain masonry prisms and six OSB retrofitted specimens (615 × 215 × 102.5 mm). The effectiveness of the proposed OSB panel retrofit techniques has been assessed in terms of flexural strength, out-of-plane load capacity and displacement. It was observed that the application of the OSB panel at the back of a masonry prism greatly influenced the out-of-plane behaviour of the retrofitted specimen by increasing its flexural capacity and also by preventing its quasi-brittle collapse.

The Utilisation of Colloidal Silica Grout in Soil Stabilisation and Liquefaction Mitigation: A State of the Art Review

Liquefaction mitigation in already existing sites has become a cause of concern for geotechnical engineers across the world. One of the possible solutions for such sites is the recently developed technique called colloidal silica grouting. The technique utilises the slow injection of colloidal silica grout at the edge of the location through injection wells and delivers it to the required location through natural groundwater flow. Later, silica particles gel and bind the soil particle together by changing the pH that, in turn, increases the strength and rigidity of loose soil. The test results obtained from the laboratory and field studies are promising and feasible to recommend colloidal silica as a potential grout material for various soil engineering applications. The present review explains the use of colloidal silica stabilisation for ground enhancement and discusses the treatment method, together with the gelation and significant factors affecting the gel formation. The current paper reviews the tests performed in colloidal silica treated soil to determine the mechanical properties, hydraulic conductivity, and evaluation of liquefaction potential. Scanning electron microscopy analysis of colloidal silica treated soil was also included to explore the microstructural bonding of soil grouted with colloidal silica. Also, the advantages and challenges of colloidal silica grouting techniques in ground improvement are included in the study. Furthermore, future research scope of colloidal silica treated soil in unexplored areas is also mentioned based on the current literature review.

Evaluation of Injection capabilities of a biopolymer-based grout material

Injection grouting is one of the most common ground improvement practice to increase the strength and reduce the hydraulic conductivity of soils. Owing to the environmental concerns of conventional grout materials, such as cement-based or silicate-based materials, bio-inspired biogeotechnical approaches are considered to be new sustainable and environmentally friendly ground improvement methods. Biopolymers, which are excretory products from living organisms, have been shown to significantly reduce the hydraulic conductivity via pore-clogging and increase the strength of soils. To study the practical application of biopolymers for seepage and ground water control, in this study, we explored the injection capabilities of biopolymer-based grout materials in both linear aperture and particulate media (i.e., sand and glassbeads) considering different injection pressures, biopolymer concentrations, and flow channel geometries. The hydraulic conductivity control of a biopolymer-based grout material was evaluated after injection into sandy soil under confined boundary conditions. The results showed that the performance of xanthan gum injection was mainly affected by the injection pressure and pore geometry (e.g., porosity) inside the soil. Additionally, with an increase in the xanthan gum concentration, the injection efficiency diminished while the hydraulic conductivity reduction efficiency enhanced significantly. The results of this study provide the potential capabilities of injection grouting to be performed with biopolymer-based materials for field application.

Material characterization and restoration of mural paintings of El-Muzzawaka Tombs, Dakhla Oases, Egypt

The present study demonstrates scientific procedures applied to study mural paintings in two Graeco-Roman tombs of El-Muzzawaka, Dakhla Oases, Egypt. First, a series of analytical methods was applied to determine the chemical and mineralogical composition of pigment and plaster samples collected from the studied tombs. The analyses were performed by means of digitalized optical microscopy (OM), polarized light microscopy (PLM), scanning electron microscopy attached with X-ray microanalysis detector (SEM−EDS), X−ray diffraction analysis (XRD), and Fourier transform infrared spectroscopy (FT−IR). Analyses of the pigment samples revealed Egyptian blue, Egyptian green, green earth, black magnetite, and red/yellow ochres. The paintings were applied on a coarse plaster layer made of gypsum, anhydrite, calcite, and quartz. The preparation layer was made of two phases of calcium sulphate (gypsum and anhydrite). Further, the detection of an organic binder, of gum Arabic, confirms the application of tempera technique. The results showed that the bed rock samples contain variable amounts of quartz, anhydrite, montmorillonite, kaolinite, gypsum, and sodium chloride (halite). In situ observations showed several deterioration forms on the studied mural paintings. The destructive climatic condition of the region and the defects of the rock structure have contributed seriously in the deterioration process. Based on experimental tests, multi restoration procedures were applied in form of cleaning, reattaching paint flakes, applying injection grouts to detached layers, reconstruction of missing parts in the plaster, repair of wide-open cracks, and final protective consolidation of the painted surfaces. Further, recommendations to minimize any future damage were discussed.

MICP-Reinforced Soil Under Three-Dimensional Grout Injection Condition

<p>The use of microbial-induced carbonate precipitation (MICP) in soil reinforcement has attracted attention in the academic field in recent years. However, most of the existing studies have been conducted based on one-dimensional ( ) grout injection condition. The present study conducted in vitro and sand column experiments of MICP using a ureolytic bacterium (ATCC 11859) (three-dimensional ( ) and models were considered in the sand column experiments) as well as the feasibility and reinforcing effect of the MICP grout injection method. A comparison of the and grout injection methods showed that the specimens reinforced using the grout injection method had higher strength, better homogeneity, a greater content, and a larger permeability coefficient compared with the specimens reinforced using the grout injection method. The limitations of the model should be considered in future practical applications.</p>

Analysis of additional stress for a curved shield tunnel

This paper focuses on analytical solutions of additional stresses for a curved shield tunnel. General equations of additional stress caused by construction loadings were deduced by rewritten Mindlin solutions, and additional thrust and friction force were considered. In addition, theoretical formulae of additional stress caused by soil loss were deduced based on the three-dimensional image theory, and the actual processes of synchronous grouting and over-excavation were considered. Then, by using a curved tunnel in Zhuhai City, China as a case study, the distribution laws of additional stress along the directions of advancement and circumference were investigated. Under the coaction of construction loadings and soil loss, it was found that the distributions of σx and σy along the advancement direction for curved tunnels are similar to those for straight-line tunnels. However, the soil around a curved tunnel is more likely to yield because the difference between the normal stresses in two directions is greater than that for soil around a straight-line tunnel. Additional stresses caused by soil loss along the circumferential direction for a curved tunnel were found to no longer have the characteristics of strictly axial symmetry. The values of compressive stress σx and σy at the outer side of the curved tunnel were found to be greater and smaller than those at the inner side, respectively. As the curvature radius decreases, the maximum tensile stresses σx and σy for curved tunnels were found to decrease and increase, respectively. Furthermore, an insufficient quantity of injection grouting will trigger detrimental effects to nearby structures during the approaching excavation.

Grouting Power Prediction Using a Hybrid Model Based on Support Vector Regression Optimized by an Improved Jaya Algorithm

Grouting power is a vital parameter that can be used as an indicator for simultaneously controlling grouting pressure and injection rate. Accurate grouting power prediction contributes to the real-time optimization of the grouting process, guaranteeing grouting safety and quality. However, the strong nonlinearity of the grouting power time series makes the forecasting task challenging. Hence, this paper proposes a novel hybrid model for accurate grouting power forecasting. First, empirical wavelet transform (EWT) is employed to decompose the original grouting series into several subseries and one residual adaptively. Second, partial autocorrelation function (PACF) is applied to identify the optimal input variables objectively. Then, support vector regression (SVR) is adopted to obtain prediction outcomes of each subseries, while an improved Jaya (IJaya) algorithm by coupling chaos theory and Lévy flights to improve the algorithm’s accuracy performance is proposed to optimize the SVR hyperparameters. Finally, the prediction results of decomposed subseries are superimposed to produce the final results. A consolidation grouting project is taken as a case study and the computation results with the RMSE = 0.2672 MPa·L/min, MAE = 0.2165 MPa·L/min, MAPE = 3.85% and EC = 0.9815 demonstrate that the proposed model exhibits superior forecasting ability and can provide a viable reference for grouting construction.

Polyurethane Grout Injection as Remedial Measure to Reduce Differential Heave in Pavement Sections Constructed over Expansive Soils

AbstractFlexible pavement sections constructed over expansive soil deposits often undergo significant damage due to volume changes in the underlying soil strata. When expansive soil deposits are co...

3D numerical simulation of consolidation induced in soft ground by EPB technology and lining defects

This paper analyses with a sophisticated numerical model the long-term phenomenology induced by Earth Pressure Balance tunnelling in compressible, low permeability soils. The complex soil-structure interaction determined by the EPB technology is analysed with a three-dimensional model that closely reproduces the sequence of face pressurisation, excavation, lining installation and tail grout injection and simulates the hydro-mechanical soil coupled response with a non-linear, irreversible, anisotropic hypoplastic model. After validation on a documented case study taken from literature, the model has been applied to a real example, MRTA Project in Bangkok. The study reveals that short and long-term settlements induced by tunnelling cannot be decoupled, being both governed by the fluid-soil-lining interaction and resulting from the time dependent stress transfer among the different elements. In this scenario over pressurising face and tail void reduces the immediate soil relaxation at the expenses of increasing the long-term settlements. Local or global defects have then been hypothesized on the lining waterproofness considering different initial groundwater conditions, soil permeability models and sets of EPB operative parameters. While concentrated lining defects play a negligible role, extensive imperfection noticeably increases settlements, volume loss and bending moments on the lining, with the same function of the relative soil-lining permeability.