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This paper presents the results of an experimental study on a full-scale precast concrete frame reinforced with glass fibre reinforced polymer (GFRP) bars that was tested to failure under lateral cyclic loading. Within the frame four different pocket connections are tested that will lead to accelerated construction. Traditionally, a pocket connection is comprised of a column that is extended into a recessed portion of the connecting beam and the pocket is filled with grout to create a moment-resisting connection. In order to accelerate the construction process, quicker setting epoxy resin was used in place of grout. The results show that while the epoxy resin could significantly accelerate and simplify the construction procedure due to its workability in addition to its high early strength and non-shrinkable properties, its thickness and low modulus of elasticity significantly affected the performance of the pocket joint. The test frame showed a flag-shaped hysteretic behaviour with narrow loops and small residual displacement thus illustrating desirable frame self-centring behaviour. This self-centring behaviour was due to rocking of the column in the pocket connection. The frame displaced with a large displacement ductility of approximately 7.0, however, the level of energy dissipation and damping ratio was very low when compared with conventional concrete structures. This experimental study shows that pocket connections can be used for GFRP reinforced precast concrete elements, however, they should be designed carefully to account for the lower stiffness of GFRP reinforcement. Also, to avoid premature failure and achieve a higher capacity of the pocket connections, the material used in the pocket to fill the gap between column and beam is recommended to have higher strength and elastic modulus compared to the surrounding precast concrete. Refereed/Peer-reviewed

Jet grouting is one of the most widely applied soil improvement techniques. It is suitable for most geotechnical problems, including improving bearing capacity, decreasing settlement, forming seals, and stabilizing slopes. One of the difficulties faced by designers is determining the strength and geometry of elements created using this method. Jet grouted soil-cement columns in soil are a complicated issue because they are dependent on a number of parameters such as soil type, grout and water flow rate, rotation and lifting speed of monitor, nozzle jetting force, and water to cement ratio of slurry. This paper discusses the effect of the water-cement ratio on the physical and mechanical characteristics of soilcrete. In the laboratory, sandy soil mixed with cement grout with water-cement ratio varies from (0.7:1 to 1.4:1). To evaluate the characteristics of soilcrete, 96 specimens were prepared in the laboratory and tested at different curing times. The results indicate that the Uniaxial Compressive Strength (UCS) of soilcrete decreases with increasing the (W/C) ratio of the grout, where the soilcrete strength of W/C ratio of 0.7 is higher about 237% of W/C ratio of 1.4 at 28-day; the evolution of the (UCS) is proportional to the logarithm of the curing time; the ratio between the modulus of elasticity (Etg50) to the maximum UCS varies from 113 to 175; when the water-cement ratio increases, the dry density of soilcrete decreases, as a result, the (USC) of soilcrete decreases.

A two-dimensional grouting model considering hydromechanical coupling and fracturing in fractured rock is proposed and implemented in an GPU parallel multiphysics finite element-discrete element software named MultiFracs. The model can simulate the grout flows in existing and induced fractures in the rock media. The fracture network is represented by broken joint elements, which is updated to simulate fracture initiation and propagation during grouting. Therefore, both the hydromechanical coupling effect and rock fracturing are considered in the grouting model. A single-fracture grouting example is presented to verify the grouting model. Finally, the model is used to simulate the grouting process in a rock mass with a complex fracture network. The effects of grout yield stress, amount of injection holes, injection pressure, aperture, and especially hydromechanical coupling on grout penetration are studied. The results show that the grouting model can simulate the interaction between grouting-induced fractures and pre-existed fractures.

The stress–strain characteristics of reinforced masonry (RM) under axial compression should be correctly understood to effectively analyse and design RM elements. However, past studies have overlooked this aspect and mainly focused on assessing the stress–strain behaviour of grouted or confined masonry. An experimental programme was executed in this research by constructing and testing RM wallettes under uniaxial compression to understand the stress–strain behaviour of RM. The effects of grout strength and lateral restrainer configurations on the compression behaviour were also studied. The experimental outcome revealed that the grout plays a major role in the axial capacity of the RM, while change in the configurations of the lateral restraining reinforcement did not significantly affect the axial capacities and axial stress–strain behaviour of RM wallettes. The predictability of the axial capacity of the RM wallettes were validated through the expressions given in the three masonry design standards. It was observed that all considered standards conservatively predicted the axial capacity of the RM. Moreover, the applicability of the existing analytical models in the literature for the RM were verified against the experimental data and an improved stress–strain model is proposed in this research.

Data related to the pre-grouting work of a large underground project are systematically analyzed to reveal the mechanism behind, to shed some light on the execution of practical grouting, and to enrich the theory of engineering geology. Grouting is generally taken as an effective way for controlling non-ignorable water seepage during underground rock excavation. Though various models have been developed to guide grouting design or to specify criteria for grouting stop, it does not change the fact that grouting is still highly experience-based. Therefore, explanation of the current situation due to grouting complexity is given through step-by-step data analysis, where the impact on grouting parameters from the geological and hydrogeological conditions is investigated, and the grouting features of two tunnels located at the same depth below the sea surface are compared and discussed. Then, the data from individual grout hole are used to construct the regional geological conditions via inverse analysis. It is found that grouting of fractured rock masses is accompanied with great uncertainty, and field grouting data can contribute significantly to a better understanding of the regional geological conditions around an underground tunnel or rock cavern.

An acceptable viscosity and an easy penetrability of cement - limestone filler grout in the granular matrix of self compacting concrete are an important factors that affecting both its rheological and its hardened properties. This experimental and theoretical work consists to study the effect of limestone filler fineness on the rheological behavior of cement - limestone filler grout. In the first part, five different grouts were prepared by varying the Blaine Specific Surface (BSS) of the limestone filler, 3060, 4750, 6320, 7680 and 9440 cm2/g, respectively. A large number of properties relating to the rheology and the stability are carried out on the five grouts such as grain dispersion, density, volume concentration of solid, dynamic viscosity and Marsh funnel flow. The second part consists to develop a theoretical model to predict the different rheological properties of the grout as function of limestone filler BSS. The results show that the rheological properties of cement-limestone filler grout such as the dispersion percentage, the intergranular distance and the flow time are strongly affected by the limestone fillers fineness. In addition, the experimental and the predicted results present a good agreement.

Considering that the particular geometric shape of a quasi-rectangular shield, the grout flowing law and its motion process are more complicated than those of a conventional circular shield. To interpret the grouting mechanical behavior in the special-shape shield tail void, the filling and diffusion mechanism of synchronous grouting was analysed. The grout flowing is separated into two independent motion processes, which contains a circumferential filling and a longitudinal diffusion. The theoretical model of the grout pressure spatial distribution was derived based on the principle of fluid mechanics. Then, the pressure distributions in the two directions were obtained using a case study and compared with the field measured data to verify the validation of the model. Although the overall spatial pattern of grout pressure distribution on the tunnel profile show a change trend dominated by the self-weight effect mostly, its local fluctuation characteristics is very abnormal relative to that of a circular shield tunnel. Moreover, the important factors in the model were analysed, including the grout material parameters, the grouting construction parameters, and some geometry parameters. The results show that the pressure loss along this way is positively correlated with the grout flow velocity and is sensitive to the shear yield stress of the grout. The pressure loss along the circumferential direction is the most sensitive to the thickness of the ring cake, and the value range suitable for the model should be 0.02–0.03 m. The pressure loss along the longitudinal diffusion direction is the most sensitive to the size of the tail void. The research results can provide a theoretical basis for the control of special-shape shield construction.

Colloidal silica (CS) is a kind of nanomaterial used in soil/rock grouting techniques in different branches of civil engineering. Many studies have recently been performed to investigate the potential of CS in improving the mechanical behavior of cohesionless soils and mitigating the risk of seismic liquefaction in urbanized areas. CS grout is chemically and biologically inert and, when injected into a subsoil, it can form a silica gel and stabilize the desired soil layer, thus representing an attractive, environmentally friendly alternative to standard chemical grouting techniques. This paper firstly describes the characteristics of CS grout, the gelation process and the main features of the behavior of the pure gelled material. The grout delivery mechanisms through porous media are then explained, pointing out the crucial issues for practical application of CS grouting. All the grouting-induced effects on the soil behavior, which have been investigated by laboratory tests on small-sized soil elements, are reviewed, including the modifications to soil strength and stiffness under both static and seismic loading conditions, to soil compressibility and hydraulic conductivity. Published results from physical model tests and in situ applications are also presented. Finally, some aspects related to the mechanism of soil improvement are discussed. A critical discussion of each topic is presented, drawing particular attention to the controversial or not yet fully examined aspects to which future research on colloidal silica grouting should be directed.

PurposeThe purpose of this article is to understand the current research status and future development trends in the field of numerical simulation on rock mass grouting.Design/methodology/approachThis article first searched the literature database (EI, Web of Science, CNKI, etc.) for keywords related to the numerical simulation of rock mass grouting to obtain the initial literature database. Then, from the initial database, several documents with strong relevance to the numerical simulation theme of rock mass grouting and high citation rate were selected; some documents from the references were selected as supplements, forming the sample database of this review study (a total of 90 articles). Finally, through sorting out the relationship among the literature, this literature review was carried out.FindingsThe numerical simulation of rock mass grouting is mainly based on the porous media model and the fractured media model. It has experienced the development process from Newtonian fluid to non-Newtonian fluid, from time-invariant viscosity to time-varying viscosity, and from generalized theoretical model to engineering application model. Based on this, this article summarizes four scientific problems that need to be solved in the future in this research field: the law of grout distribution at the cross fissures, the grout diffusion mechanism under multi-field coupling, more accurate grouting theoretical model and simulation technology with strong engineering applicability.Originality/valueThis research systematically analyzes the current research status and shortcomings of numerical simulation on rock mass grouting, summarizes four key issues in the future development of this research field and provides new ideas for the future research on numerical simulation on rock mass grouting.

Grout curtains are commonly constructed under dams to reduce the seepage through the rock foundation. In the design of grout curtains, empirical methods have mainly been used since the introduction of dam foundation grouting. Although empirical methods have been used with success in several projects, they have their limitations, such as poor control of the grout spread, only an indirect consideration of the threat of internal erosion of fracture infillings in the grouted zones, and the risk of hydraulic jacking. This paper presents a theory-based design methodology for grout curtains under dams founded on rock. In the design methodology, the grout curtain is designed as a structural component of the dam. The risk of erosion of fracture infilling material is explicitly accounted for along with the reduction of the hydraulic conductivity of the rock mass, and an optimization of the total uplift force. By applying the proposed design methodology, engineers can create a design better adapted to the prevailing geological and hydrogeological conditions in the rock mass, resulting in more durable grout curtains. The proposed methodology also enables cost and time estimates to be calculated for the grout curtain’s construction. Applying the principles of the observational method during the grouting execution also allows the design to be modified via predefined measures if the initial design is found to be unsuitable.

Ground improvement by permeation grouting is widely utilized for improving engineering properties of soil. The accurate evaluation of a region improved by grouting is a critical issue to ensure the performance of grouting; nevertheless, current methods to evaluate the area of grouted bulbs under the ground are not well-documented. This study aims to use cross-hole electrical resistivity tomography (CHERT) to evaluate a grouted bulb region by considering the effect of electrode configuration at laboratory scale using a cylindrical container filled with saturated sand. Curing time monitoring was also conducted on grouted bulbs with various recovered Carbon Black (rCB) concentrations. Based on the inverted result, the predicted area of the grouted bulb was addressed, and then the error value between the actual and predicted areas was examined. The results of this study show that CHERT can be employed to assess the location and area of a grouted bulb. Also, it was observed that electrode spacing, damping factor, and curing time had significant influences on the image resolution and error value. Unlike the above-mentioned factors, change of rCB concentration ratio had only a slight effect on the image resolution. Thus, the use of a small amount of rCB as an additive material to enhance the grout strength can also provide a distinct contrast of measured resistivity between the grouted bulb and surrounding soil. In this study, a grouted bulb containing 3% of rCB is recommended based on the test results on strength characteristics. In addition, CHERT measuring can be conducted even in early stages of curing, during which it exhibits a better electrical resistivity contrast between the objective area and the surrounding soil.

Aims at improving the utilization rate of red mud and preparing a low-cost grouting material for underground engineering, the ultrafine red mud was adopted to prepare a slag-red mud based grout, and its fresh and hardened state properties were investigated comparing with the coarse red mud. The results showed that the incorporation of red mud could prolong the setting time and decrease the viscosity and thixotropy of slag-based geopolymeric grout, and ultrafine red mud has a better decrement effect. Ultrafine red mud has an enhancement effect on the slurry stability. The mechanical strength decreased with the adoption of red mud, while the ultrafine red mud has a higher mechanical strength than coarse red mud. The microstructure analysis showed that red mud plays a filling role in the geopolymerization process, and mechanical activation could increase the reactivity of red mud, furthermore, the iron component in ultrafine red mud could take part in the geopolymerization process. The results shed light on the utilization of red mud and the application of geopolymer in grouting engineering.

One solution to the high cost and scarcity of building materials is to use alternative and sustainable materials. The study presented herein developed an eco-friendly masonry grout using high volumes of palm oil clinker powder to replace cement and palm oil clinker to replace coarse aggregate. Several batches of grouts with different amounts of these materials were made to determine the technical viability of the grout. Scanning Electronic Microscope (SEM), X-Rays Diffraction (XRD), Energy Dispersive X-Ray (EDX) and Thermogravimetric Analyzer (TGA) analyses were conducted to investigate the microstructure characteristics of the grout, and water absorption, initial rate of absorption, sulphate attack and electrical resistivity tests were conducted to determine its durability. Compressive strength tests were conducted at different curing ages and the drying shrinkage of the grout was monitored for 180 days. The results indicate that the new grout is as good as a conventional grout but with added sustainable and economic benefits. The new grout can be used in masonry construction and can be used to alleviate the inadequate supply of affordable housing.

Historically, the idea of designing and installing rockbolts in rockmasses can be traced back to the construction of the Snowy Mountain hydroelectric scheme in Australia, which was completed in 1974. The use of rockbolts as a ground support system has been widely applied to enhance the stability of structures in mining and to resist the movement of keyblocks in underground excavations. The strength of a rockbolt as a rock support tool lies in its ability to improve the tensile and shear strength needed to maintain the load-bearing capacity of a rockmass. Currently, rockbolts are extensively used as reinforcement methods in mining and civil engineering projects to support deforming rockmasses in coal and hard rock mining, tunnelling and underground openings. The performance of a rockbolt depends on the design parameters such as load-bearing capacity of the bolt, strength of the bolt, bolt diameter, length of the bolt and bolt spacing. This study provides a detailed review of the various applications of rockbolts in mining operations. In addition, the integration of smart sensors in rockbolts to enhance monitoring of displacement measurements, stresses, subsidence of pillars and ground pressure on structures are discussed in this paper. The use of smart rockbolt devices, which has improved the monitoring and evaluation of critical parameters in rockbolts such as the axial force, corrosion occurrence, grout quality and resin delamination, are also discussed. This review shows that with the numerous applications of rockbolts in mining, especially in underground excavations and tunneling engineering, rockbolts can be used as supports in rocks with different geological conditions. Nevertheless, this paper highlights that there are still some areas that need improvement in rockbolting technology.

The design of grouting engineering in practice is either based on conventional soil mechanics or empirical procedures ignoring the effect of degree of saturation (water content). In this study, a series of laboratory-pressurized grouting tests were conducted on unsaturated sand to reveal the influence of soil water content on the grouting characteristics. With combination of direct shear tests at constant water content, water retention tests as well as microscopy observations, the mechanisms that controlling the strength and in turn the grouting characteristics in unsaturated sand were interpreted from the perspective of water–air interface. It was found that the non-monotonic phenomena of grouting characteristics (injectability and diffusion characteristics) with increasing water content were strongly dependent on the shear strength, which is influenced by the apparent cohesion induced by capillary mechanisms relating to the water–air interface. The threshold value of the injectability and diffusion pattern is corresponding to the boundary of the two transition zones (two different desaturation mechanisms) in the water retention curve. In the primary transition zone, the water phase is interconnected with air bulbs entrapped. With the drainage of bulk water in the large pores, the amount of water menisci increases, generating larger and larger surface tension force between particles. Therefore, less and less grout was injected as the bearing capacity and shear strength increase. However, in the second transition zone, with the drainage of menisci water, the menisci area of each pores decreases, inducing less and less surface tension force. Thus, more and more grout was injected as the bearing capacity and shear strength decrease. It is hoped that the work in this study will facilitate researching the grouting mechanisms in unsaturated soil, thus optimizing the grouting parameters in engineering practice.

The grouting is used to reinforce soft ground and to prevent the leakage of water in the soil. The objective of the study is to enhance the compressive strength of grout materials by using reinforcing fibers and to increase the strength of soil using blast furnace slag powder. For this purpose, cement was replaced with the blast furnace slag powder by 30 to 60%. Furthermore, for comparison of carbon fibers with aramid fibers, each fiber was added by 0, 0.5, and 1.0% of the weight of material. As the contents of carbon fibers and aramid fibers increased, the uniaxial compressive strength increased. This is due to the interlocking of fibers in the grout material that increased the uniaxial compressive strength. Moreover, the grout material reinforced with aramid fibers showed an increase of uniaxial compressive strength by at least 20% compared to the carbon fibers. An environmental assessment was done through a heavy metal leaching test and a pH test. The test result reveals that about 50% of chromium (VI) leaching decreased as 30% more blast furnace slag powder was used but the pH test shows about 0.5 pH increased as 30% more blast furnace slag powder was used. Further study is necessary for the pH test.

A numerical simulation method of shield tunnel excavation is developed to capture the time-dependent deformation behaviour of surrounding soil. The simulation method consists of four parts: (i) an elastic-plastic-viscous constitutive model that can not only reasonably describe the viscous deformation behaviour of soil, but also appropriately calculate the plastic deformation under typical stress paths of excavation; (ii) simulation of main factors related to shield tunnel excavation, including the shield machine, face pressure, lining, grout behavior, and contacts between multiple media; (iii) a simulation procedure for excavation to reflect the process of shield tunnel excavation and achieve reasonable stress and strain fields at the end of the construction stage; (iv) a creep process that is used to investigate the long-term mechanical behaviours of the surrounding soil and tunnel lining. Taking the CK570H tunnel project in Taipei as the background, a numerical simulation is conducted by adopting the developed simulation method. Based on the simulation results, the radial and circumferential stresses acting on the lining, which are induced by the surrounding soil viscosity, are analysed. The rule of the mechanical response of lining, including its deformation, bending moment, and axial force, with time is revealed. On this basis, the long-term safety of the lining is evaluated.

High-volume fly ash (HVFA) cementitious composites (paste, grout, mortar, and concrete) have been widely investigated as a class of sustainable materials due to their lower carbon footprint and often better life cycle performance than conventional Portland cement mixtures. Recent years have seen increased research in HVFA-based materials, and the potential of this type of mixtures in engineering applications has significantly improved. In this context, this work reviews the renewed knowledge of HVFA mixtures, focusing on the relevant papers published over the last decade. The effects of replacing cement with a HVFA binder on the fresh properties, mechanical properties, durability performance, and environmental impact of HVFA cementitious composites are explored. Measures that can compensate for the main drawbacks that limit the wider application of HVFA mixtures are discussed in detail. At last, we summarize the research needs and remaining challenges of HVFA cementitious composites.

Grouted splice connector is widely employed in precast concrete structures, but its utilization is still limited by shortcomings such as high construction cost, inconvenience in assemblage, and uncompacted grout caused by its small sleeve diameter. The grouted sleeve lapping connectors proposed by the authors can not only provide reasonable force transfer and convenient construction processing but also have the characteristics of low price and easy grouting. In this paper, the seismic performance of two full-scale precast concrete columns with two types of grouted sleeve lapping connectors was investigated, where type-I connector connected two lapped rebars and type-II connector connected four lapped rebars by a steel sleeve, respectively. A cast-in-situ column was also tested as a reference. All the specimens were tested under reversed cyclic horizontal load with a constant axial force. The distribution of cracks, failure modes, loading capacities, deformation abilities, stiffness, ductility, hysteresis loops, and energy dissipation of the specimens were studied. The type-I and type-II grouted sleeve lapping connectors satisfactorily transferred the stress of rebars when the columns reached their ultimate loads, and the seismic performance of the precast concrete columns was found to be comparable to that of the cast-in-situ column. Thus, the grouted sleeve lapping connector has a potential to replace the grouted splice connector in cast-in-situ connection.

Since the failure modes of fully grouted bolts subject to displacements of rock joints are difficult to predict, the joint displacements in this study are categorised into two types: opening displacement and shear displacement. At first, a closed-form solution incorporating the nonlinear constitutive model of interfaces between bolts and grout is developed, which is able to formulate the full-range behaviour of bolts subject to the opening displacements of rock joints. Then, a novel numerical approach considering the nonlinear rock reaction force is proposed, which can analyse stress and displacement conditions on each point along a bolt. The results of the proposed numerical approach are validated by existing test results. Combining the proposed numerical approach with the improved closed-form solution, a comprehensive model for predicting yield and failure patterns of rock bolts is proposed. In this way, decoupling between the bolt and grout, the yield and failure patterns of two potential points along the bolt are also highlighted and discussed. Further discussions about the influences of bolt inclined angles to the discontinuity and the dilatancy effect of the joint face are carried out at last. This work provides a useful tool to evaluate the behaviours and estimate the load-bearing capacity of fully grouted bolts in jointed rock masses.

In real engineering, with the gradual deterioration of mining geological conditions, the improvement of the bearing performance of fully grouted bolts is beneficial to better control of the roadway surrounding rock. For this purpose, based on the idea of steel fiber reinforced concrete, a systematic laboratory study was conducted to investigate the effect of steel fiber grout on the bearing performance of anchored specimens. Three steel fibers with different diameters (0.5, 1.0 and 1.5 mm) were selected. Fiber specimens and fiber-free specimens were prepared and a series of pull-out tests were conducted. The experimental results show that the steel fiber grout can effectively improve the bearing performance of the anchored specimens and enhance the anti-destructive ability of the anchored specimens. The steel fibers in the grout can enhance the mechanical interlocking effect, the dilatancy effect and the friction effect of the anchoring interface, thereby improving the ability of the anchored specimen to withstand additional loads. The reinforcement effect of steel fiber on the bearing performance of the anchored specimens presents an obvious diameter dependence. With the increase of the steel fiber diameter, the bearing properties of the anchored specimens tend to increase and the cumulative AE counts, cumulative AE hits, cumulative AE energy and AE events also increase. Moreover, the steel fiber grout can more fully mobilize the bearing performance of the anchoring interface, and the number of microcracks in the fiber specimens increases during the bearing process. This research results may provide a useful reference for the support design of fully grouted bolts.

A large share of the primary energy is consumed to provide space heating. Geothermal energy offers a regenerative alternative. For reasons of efficiency and environmental protection, it is important to ensure the system integrity of a borehole heat exchanger (BHE). Previous investigations have focused on the individual components of the BHE or on the grout and pipe systems’ integrity. This study focused on the analysis of the hydraulic system integrity of the complete subsoil–grout–pipe system as well as possible thermally induced changes. For this purpose, a pilot-scale experiment was built to test a 1-m section of a typical BHE under in situ pressure, hydraulic and temperature conditions. During the tests the hydraulic system permeability of the soil and the BHE was measured continuously and separately from each other. In addition, the temperature monitoring array was installed in a 50-cm cross-sectional area. Significant temperature-related fluctuations in the sealing performance could be observed. Hydraulic conductivity limits required by VDI 4640-2 (Thermal use of the underground—ground source heat pump systems, 2019) were exceeded without frost action. The succeeding application of freeze–thaw cycles further enhances the system permeability. The study shows that the thermally induced effects on the system integrity of the BHE are larger and more significant than the subsequent frost-induced effects. The hydrophobic character of the high-density polyethylene (PE-HD) pipes as well as its high coefficient of thermal expansion seem to be the main points of weakness in the system. Optimization research should focus on the interface connection between grout and pipe, whereby hydrophilic pipe materials such as stainless steel or aluminum should also be considered as well as manipulation of the pipe surface properties of PE-HD.

Steel tubes are widely used in strengthening reinforced concrete (RC) columns. However, in engineering construction, the effect of preload on the original RC column on the performance of strengthened RC column has not mostly considered. Therefore this paper tests five circular short columns under axial compression—three steel tube-strengthened RC columns with preload, one strengthened RC column with no preload, and one normal RC-to study compressive performance of steel tube-retrofitted circular RC short columns under various preload levels. Moreover, the verified finite element numerical model is established using ABAQUS software to stimulate the behavior of the retrofitted columns. The extended parametric studies is conducted based on the thickness of steel tube, yield strength of steel tube, and strength of grout under preload, in addition to preload level itself. A practical design method is proposed and compared with four existing design codes to predict the axial compressive ultimate strength of the retrofitted column under preload.

The present article analyses the influence of defects in the bonding zone between the reinforcement bar and the grout on the mechanical performance of the full-grouted sleeve connector. Grouted sle...

Synchronous grouting has a very important effect on shield tunnel, which directly affects the stability of excavation face and the safety of segment structure. Testing the setting time and early strength of mortar is conducive to timely control the surface settlement and prevent the segment from floating. The flow table test can ensure that synchronous grouting can fill the excavation gap of shield machine to the greatest extent. Oedometer test can obtain physical and mechanical indexes such as elastic modulus, Poisson's ratio, compression and drainage of slurry at different ages. The test results showed that the use of well-graded, small-sized machine-made gravel (0–5 mm) and natural sand (0–2 mm) with high-efficiency additives promoted the formation of early strength in grout and reduced the probability of plugging in the grouting pipe at the tail shield. The oedometer test results indicated that the quantity of water drained from a grout mixed for more than 2 h was stable and the grout deformation within 1 h of compression accounted for 80% of the total deformation. The Young’s modulus of the grout reached 10 MPa when the grouting pressure was > 0.2 MPa, meeting the requirements for field injection. In this study, an efficient synchronous grouting mixture proportion suitable for calcareous sand layer is proposed, and the performance of slurry in fresh state is obtained through a variety of tests, which can be widely used in shield tunnels in similar strata.

Jet grouting methods have recently become one of the soil enhancement technologies utilized to provide strength improvement and solve most problems of weak soils. In this study, a full-scale 1 m diameter and 5 m length jet grout (soilcrete) column was constructed in the field with a water-to-cement ratio of 1 and 400 bar pressure injections. A mechanical, physical, and microstructural investigation was performed on jet grout samples taken from six different depths (0.0, 0.5, 1.0, 1.5, 2.0, and 2.5 m) and at the same depth at five different locations, including the center. For normal conditions, samples were prepared for six periods to study dry and saturated conditions. The following tests are performed on each sample: compressive strength index (I-s) in all conditions, water absorption, density, porosity, and interface friction. Additionally, SEM was performed on selected samples to investigate the microstructures of jet grout columns (JGCs). The test results showed that the I-s varies with depth, and within the same depth, the variation is approximately 20%. Other properties also vary with depth and location; for example, the average percentage of water absorption and porosity are considered minimum values at the same location, which are 53 and 30%, respectively. However, the interface friction angle of organic soil-cement grout gains 48 degrees and 10 kPa cohesion. The theoretical part of this study is to predict the diameter of JGC in organic soil.

This paper presents an experimental investigation of propagation and fluid pressure of grouting in a two-dimensional fractured network replica. Two-dimensional fracture network models with a rough profile were simulated based on Barton’s standard roughness curves, and an orthogonal experiment of chemical grouting was conducted to explore the relationship between the sealing efficiency and different factors, including the joint roughness coefficient, initial water flow rate, gel time of slurry, and grout take rate. The results show that the initial water flow rate had the greatest influence on the sealing effect, followed by the joint roughness coefficient, grout take rate, and gel time of slurry. Together with the grouting quality and slurry diffusion form, the grouting sealings were divided into two types, i.e., partial plugging with edge unfilled and completely plugging with fracture fully filled. The slurry propagation sequence in the intersected fractures indicates that the slurry first diffuses downstream of the current fracture, then downstream of the cross fracture, and finally upstream of the cross fracture. The grouting pressure on the later stage of grouting was greater than that at the beginning of the grouting, resulting in a better grouting effect.

Grouting is an important and convenient technique to improve rock properties. The grouting effectiveness depends on quantities of complex influencing factors. The investigation on the effects is essential for engineering applications. This study focuses on the evaluation of shear strength with experimental and numerical approaches. Firstly, the shear test of rock sample with cement grouting was carried out. Based on the tests, the numerical modelling of grouting was conducted. The effect of normal stress, grouting thickness and strength parameters of grout on the shear strength was studied, respectively. Then, the critical condition of effective grouting was proposed. Lastly, the mechanism in the influencing factors was discussed. Results show that the strength of grouted rock could be improved by increasing the normal stress and the grout parameters and decreasing the grouting thickness. The critical condition of effective grouting involves the grouting thickness and the strength parameters of grouting material. When the condition of effective grouting is satisfied, the grouting effect would be remarkable with additional supports, such as bolts. According to the opening of the dominant structural plane, the grouting parameters should be reasonably designed to meet the critical condition. The results could provide experimental and theoretical methodologies for the grouting design.

The bond between tendons and grout is crucial to the performance of bonded post-tensioned concrete structures. To study the bond performance of grouted tendons at elevated temperatures, pull-out tests were conducted on specimens comprising either a mono- or multi-strand tendon located centrally within a grouted duct inside a concrete cylinder, at test temperatures of 20–600°C. It was found that the bond strength deteriorated with a rise in temperature and the degradation of bond strength was more severe than that of other mechanical properties. Three types of failure mode were observed: pull-out, partial splitting and through splitting. The use of a smaller duct could improve the bond strength of specimens failing in pull-out mode. The influence of the strength of the outer concrete was found to be insignificant. Based on the distinct bond behaviour of different failure modes, a bond–slip model was developed by regression of the test results.

One of the highly efficient sources of renewable energy is the Ground Source Heat Exchangers (GSHE). Thermal interaction effects between boreholes cause a decrease in the efficiency of GSHEs. In the present study, the effects of the distance between boreholes, soil properties, grout heat conduction coefficient, and boreholes’ arrangement are investigated on the outlet fluid temperature in the GSHEs. The Finite Line Source (FLS) model is coupled with the Simplified Thermal Resistance-Capacity Model (STRCM) and a transient modified model called FLS-STRCM is developed. The FLS model considers the thermal interaction between boreholes while the STRCM model solves the flow field inside the boreholes. The obtained results of the FLS-STRCM are compared with the transient results of Computational Fluid Dynamics (CFD) simulations and available experimental data. To simulate the heating and cooling cycles of a building, the present model of GSHE is coupled with the water to air heat pump in the TRNSYS software. The available models of GSHEs in the TRNSYS software are not capable of considering different arrangements of boreholes. However, the present model, in addition to the transient simulation of GSHEs, can examine any desired layouts of boreholes. The results of the present model show that for a set of 6 boreholes in a rectangular arrangement, a reduction of the distance between boreholes from 7 m to 3 m results in 2.8% changes in the average temperature of outlet fluid. Also, the investigation of soil and grout properties shows that the soil properties has a dominant effect on the outlet fluid temperature. Considering the computational time and the acceptable accuracy of the presented model compared to the CFD methods, the FLS-STRCM model can be employed for the engineering applications in the construction of the GSHE system and the long-term simulations.

In FLAC3D, cable element or modified pile element can be used to build slope anchoring model. However, the difference between the two structural elements and their influence on the calculation results have not been studied in depth. In order to solve this problem, the Xiashu loess slope anchoring models based on cable element and modified pile element were constructed respectively. A variety of anchoring schemes were designed by orthogonal experiment method, and then they were brought into the model for calculation and the calculation results were analyzed by range analysis and variance analysis. The results show that the modified pile element can bear the bending moment and reflect the strain softening property of the grout. From the perspective of slope safety factor, the anchorage length and anchor bolt spacing are the main factors affecting the stability of the slope, and the anchorage angle is the secondary factor. The grout in cable element is assumed to be an elastic-perfectly plastic material, so the safety factor of the slope can be significantly increased by increasing the length of the anchor bolts. This will bring potential risks to the slope treatment project. Therefore, in the calculation of the slope anchoring model, the modified pile element is more suitable for simulating the anchor bolt.

Changes in Australian Masonry Standards and National Code of Construction for reinforced masonry (RM) under compression impress the need of a grout annulus and vertical bar confinement using 6 mm t...