Search

In mechanised tunnelling, the filling of the annular gap behind the precast concrete segments is one of the essential operations. The main goal of filling this space is to reduce surface settlements and limit movements due to tunnel excavation in the soil mass. To achieve this aim, a two-component grout is often used to fill the annular gap. Determination of the amounts of ingredients in the two-component grout should be carried out in such a way that the injection materials will be able to fulfil the required performance and technical properties. In this study, laboratory tests were carried out to investigate two-component grout properties, such as flowability, bleeding, gelling time and uniaxial compressive strength. The effect of lateral pressure on grout resistance was studied according to real excavation situations. The influences of the grout ingredients and effective parameters such as bentonite and cement contents, water–cement ratio and the dosage of accelerator (sodium silicate) and accelerator ratio were also investigated.

This paper presents the results of an experimental evaluation of masonry grout made with lime-activated slag–glass powder blend as a binder. The purpose of this study is to develop a grout mixture that is low-carbon dioxide (‘low-carbon’) and has the potential to replace the traditional grout material used in load-bearing concrete block masonry construction. Traditional grout material uses Portland cement, production of which is responsible for a large proportion of carbon dioxide emissions. Thus, elimination or even reduction in the use of Portland cement will minimise environmental impacts. Three grout mixtures incorporating different proportions of glass powder as a partial replacement of slag as an aluminosilicate precursor were investigated to determine the optimum mix proportion that yields the desired properties of the grout material used in concrete block masonry construction. The workability, compressive strength and permeability properties of the mixtures were evaluated. Results from this study show that the use of glass powder at 25% replacement of slag as a precursor in the binder system provides the best performance, and that this mixture can be successfully used as an alternative and low-carbon grout material for concrete block masonry construction.

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.

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 massive mechanized and irrational coal mining has generated many goafs (i.e., mined-out areas) in China. To manage these goafs effectively, grouting technique has been commonly used to fill the fractures in the overburden strata. However, little is known about the development and distribution of fractures in the overburden strata above the goaf. The lab-scale simulation of fracture development, as well as the grouting process, can provide valuable information for managing a real goaf by the grouting technique. Based on the mechanical properties of rocks and soils in the goaf of Kangjiagou coal mine in Shanxi Province, an experimental system was designed to simulate the development of fractures in the overburden strata above the goaf and study the diffusion behaviors of the grout slurry under different conditions (such as grout volume, grouting pressure, porosity, and water-solid ratio). The physical model test showed that more fractures were found in the fractured and caved zones, with fracture porosity ranging from 15.05 to 40.79%. The grouting experiment showed that, when the water-solid ratio was smaller than 1.15 and the grouting pressure was lower than 0.3 MPa, the changes in diffusion radius were stable during the grouting process. To maintain the stable changes in diffusion radius and reach a high filling ratio, the grouting pressure should be controlled in the range of 0.2–0.4 MPa at the porosity of 24.8% and 0.5 MPa at the porosity of 35.1%. The findings derived from this study are widely applicable under real engineering contexts.

Pullout tests for the deformed steel bars in early-aged cementitious grout by considering the variables of testing ages, cover thicknesses, and diameters of steel bar were conducted, and the local bond stress–slip relationship at different positions of the anchorage length of steel bar was studied. Results indicated that, with the increase of testing age, the load-slip curves exhibited a higher ultimate load and had steeper ascending and descending branches; however, the slippage at the ultimate load exhibited a decreasing trend. Moreover, with the increase of cover thickness and diameter of steel bar, the ultimate load of pullout specimens increased obviously, while the corresponding slips generally had no obvious correlations. According to an analysis of the measured rebar strain, the distributions of the steel stress and bond stress as well as the relative slip along the embedded length were obtained under different external loads. Steel stress transfer and bond stress distribution parameters were introduced to characterize the nonuniformity of the distributions of the steel stress and bond stress along the steel bar, and the effects of the testing age, cover thickness, and diameter of steel bar on these two parameters were analyzed. Results showed that the both of these two parameters increased with the increasing tensile load, testing age, and cover thickness and with the decreasing diameter of steel bar. Thereafter, the local bond stress-slip relationships along the anchorage length and position functions reflecting the variations of these relationships were proposed.

In the loose and fractured coal seam with particularly low uniaxial compressive strength (UCS), driving a roadway is extremely difficult as roof falling and wall spalling occur frequently. To address this issue, the jet grouting (JG) technique (high-pressure grout mixed with coal particles) was first introduced in this study to improve the self-supporting ability of coal mass. To evaluate the strength of the jet-grouted coal-grout composite (JG composite), the UCS evolution patterns were analyzed by preparing 405 specimens combining the influential variables of grout types, curing time, and coal to grout (C/G) ratio. Furthermore, the relationships between UCS and these influencing variables were modeled using ensemble learning methods i.e. gradient boosted regression tree (GBRT) and random forest (RF) with their hyperparameters tuned by the particle swarm optimization (PSO). The results showed that the chemical grout composite has higher short-term strength, while the cement grout composite can achieve more stable strength in the long term. The PSO-GBRT and PSO-RF models can both achieve high prediction accuracy. Also, the variable importance analysis demonstrated that the grout type and curing time should be considered carefully. This study provides a robust intelligent model for predicting UCS of JG composites, which boosts JG design in the field.

The development of water-conducting fractures from underground coal mining is a geological cause of groundwater loss. Sealing mining-induced rock fracture channels through borehole grouting is an effective way to protect groundwater resources. A ground-based engineering test was conducted at the Gaojiabao coal mine that utilized horizontal directional drilling (HDD) to grout and seal water-conducting overburden fractures. This study carried out a theoretical and experimental exploration using HDD to evaluate the development characteristics and grout hydraulic conductivity of these mining-induced fractures. The results showed that, as a result of varying fracture morphologies in different zones of the mining overburden, multiple fracture types were sequentially exposed as the HDD borehole advanced from the original rock mass outside the mining area towards the mining-induced fractured rock mass. The fracture types were exposed in the following order: compressive shear fractures, tensile failure fractures, and bed separation fractures. Moreover, the void characteristics of the exposed fractures in the borehole were significantly different at different drilling horizons, which affected the flow behavior and sealing performance of the injected grout. Lastly, three typical orders in which the different types of fractures were sequentially exposed by the borehole were summarized, and further analysis of the orders led to a scheme for determining drilling horizons favorable for efficient fracture sealing. The results of this study will enable efficient grout sealing of the fractures caused by mining and reduce groundwater loss.

Unreinforced masonry buildings in the historic centers of the world have often been overlooked for centuries without any protection. These buildings demonstrate low resistance under external effects, especially against earthquakes. Earthquakes cause serious damage to the buildings and even the collapse of structures as a result of seismic stimulation from the impact of pounding with structural impacts. For this reason, it is of great importance to repair and strengthen damaged masonry structures. This study investigated the testing of masonry wall specimens produced from different kinds of masonry units with various types of mortar. Then, geopolymer grouts with high mechanical properties were produced by using alkali activation and industrial products. The experimental performance of strengthened masonry wall samples was determined using the optimum geopolymer grout in vertical compression tests. The behavior, failure mode, and crack pattern of the masonry wall samples were determined under loading systems. Experimental results demonstrate that the use of additive styrene-butadiene (SB) latex geopolymer grouts on damaged walls increased the load-carrying capacity and ductility significantly compared to the corresponding values of samples before initial failure. All of the strengthened walls failed through the de-bonding failure mode, and no visible damage was observed on the samples. Consequently, geopolymer grouts displayed many advantages over conventional repair materials due to their high viscosity, compressive strength, eco-friendliness, and excellent resistance.

The benefits of helical anchors have made them a good alternative to grouted soil anchors. However, as their bearing capacity depends on the length and number of helices, they are not economically justified or feasible in some projects. In this research, an attempt was made to propose a new method of implementing helical anchors and their application considering the advantages of helical and grouted anchors. This method, which was named “grouted helical anchor,” was tested in wet sandy soil. Since one of the most important parameters of anchor design is pull-out resistance, the parameters affecting the pull-out resistance of grouted helical anchor such as overburden pressure, helical anchor configuration, and grout were evaluated to determine the best conditions for constructing an anchor. The results show that in the helical anchor with a 100-mm helix, changing the helix spacing from 300 to 400 mm at 90 kPa increases the maximum pull-out force by less than 6%. At the same overburden pressure, if the helix spacing is 400 mm and the helix diameter is changed from 100 to 130 mm, the maximum pull-out force will increase by more than 29%. However, by injecting and modifying the anchor to the grouted helical anchor, the maximum pull-out force can be increased by more than 45%. Therefore, injection operations can help to increase the pull-out capacity of the helical members without changing their configuration.

A novel connection adopting lap-spliced large-diameter bars and ultra-high performance concrete (UHPC) grout was developed to accelerate the assemble progress of precast bridge columns. The precast bridge column adopting the connections was testified to be on a par with the monolithic concrete counterpart in terms of seismic performance in previous research. This paper aims to develop a numerical model to further investigate the seismic behavior of the proposed bridge column considering the bar-slip effect. A finite element model was established for the bridge columns considering deformation components of flexure, shear, and bar-slip. The bond behavior between the deformed bar and UHPC was defined using a new practical model, which was developed based on a pullout test including five specimens in this research. The established finite element model was verified by the cyclic loading test in literature in terms of the overall hysteretic curve and local responses. The validated model was used to conduct parametric analysis to study the contributions of the different deformation components to lateral deformation as well as the effects of large-diameter bars on seismic performance. Results show that all the pullout specimens have the tensile fracture of bars, which indicates that the development length of 5 times bar diameter is sufficient for deformed bars in UHPC when the bar diameter is no more than 32 mm. The practical model is effective to consider the effects of the slip between the deformed bar and UHPC. The finite element model can predict the overall hysteretic curve and local responses at different drift ratios. The bar-slip has a considerable even dominative contribution to the lateral deformation of the proposed bridge column. Larger bar diameter can enhance deformation capacity as well as reduce energy dissipation and residual drift ratio.

Combining the results obtained by hydraulic (hysteresis) and hydrochemical (multivariate statistical analysis) approaches gives a better understanding of karst aquifer behavior, functioning of the hydraulic barrier and hydrogeochemical processes. The hydraulic approach is based on the principle that the relation of the groundwater levels in piezometers and the water level in a surface-water reservoir often follow certain hysteretic patterns that reflect a system of internal structure. This allows an analysis of the structure of the karst system as well as properties or functionality of the hydraulic barrier associated with the dam. Adequate understanding of the hysteresis diagrams is crucial to successfully addressing the issue of karst aquifer behavior and water leakage direction; normalized hysteresis data provided easier comparison between the data series and the interconnections among observed patterns. The application of the hydrochemical approach further contributed to an understanding of the karst system as well as the impact of the hydraulic barrier. Two-way hierarchical cluster analysis enabled the isolation of areas with similar hydrochemical characteristics, which was supplemented with circulation directions assumed by hydraulic methods. Factor analysis helped in identifying major hydrogeochemical processes in the various hydraulic regimes. The combined findings of hydraulic and hydrochemical approaches were successfully applied to a complex karst aquifer system where the reservoir (Lazici) was created for a reversible hydropower plant, situated in the Tara mountains, in the Dinaric karst of western Serbia.

An interface equivalent modeling method is proposed in this study to describe the bond behavior between multi-strand tendons and surrounding grout. The interface equivalent principle is firstly proposed to determine the effective bond interface between tendons and grout considering the effects of the quantity, the arrangement and the space of strands. Then, the maximum bond stress of the multi-strand tendons provided by the interface is derived and incorporated into the existing bond stress-slip relationship to characterize the bond of multi-strand tendons. Subsequently, a pull-out numerical model incorporating the considered effects is developed to predict pullout forces-slip response for tendons. Finally, a direct pull-out test on three strands tendons is designed to verify the interface equivalent modeling method by comparing with the numerical and experimental results. The proposed method is also validated against previous experiment on seven strand tendons. Results indicate that the proposed interface equivalent modeling method can reasonably predict the bond behavior between multi-strand tendons and surrounding grout. The applicability and feasibility of the proposed equivalent modeling method is also investigated.

A novel pocket connection was put forward to be utilized in both ends of a precast bridge column to connect cap beam and foundation, respectively. The pocket connection adopted noncontact lap-spliced bars and ultra-high performance concrete (UHPC) grout. One 1:2.5 scale specimen was fabricated and tested to investigate the seismic performance of the precast bridge column with the proposed pocket connections. Based on OpenSees platform, a verified finite element model was utilized to simulate cyclic behavior of a monolithic reinforced concrete companion. The comparison was carried out to evaluate the precast bridge column in a comprehensive way. The results show that drift capacities of the two bridge columns are up to 5% and controlled by lateral force degradation. The lapped length of five times diameter is feasible when UHPC grout is used for longitudinal bars with a diameter no more than 32 mm. For the precast bridge column, the joint opening between column and foundation contributes over 30% to total lateral displacement and traditional equivalent plastic hinge model may be not suitable. With drift ratio over 1.5%, the precast specimen has larger secant stiffness than that of the monolithic companion, owing to the shorter shear length of the precast specimen caused by moving up of the actual plastic hinge region. The precast and monolithic bridge columns have good energy dissipation capacity, and the maximum damping ratios reach up to 19.8% and 22.6% at 5% drift ratio, respectively. The precast specimen has 18.8% less residual drift ratio at 5% drift ratio than the monolithic companion.

The rapid depletion of natural resources has led to the need to develop sustainable practices and material in various applications. One such sustainable practice is to divert the waste generated in the palm oil industry into production of building materials. In this study, palm oil clinker (POC) is used to replace cement and coarse aggregate. The POC chunks are crushed to be used as coarse aggregate and further ground to produce POC powder (POCP) to be used as a binder. The physical properties, chemical composition and scanning electronic microscopic studies were conducted to check the feasibility of substitution of up to 50% POCP as binder and up to 100% POC as coarse aggregate. Density, ultrsonic pulse velocity(UPV), compressive strength for air & water curing, flexural, tensile strength, modulus of elasticity in water cured regimes and structural efficiency were evaluated for the samples. Carbon footprint, cost effieciency and energy savings were also evaluated to understand the contribution of POC to sustainability. The results revealed that the ideal mixture of GPP (30% POCP & 50% POC) masonry grout achieved 79% of compressive strength, a 83% of flexural strength, 85% of tensile strength and about 85.5% of modulus elasticity, as compared to control masonry grout. Carbon emissions of GPP was reduced by 21% and 14.60% cost reduction was established, in addition, appreciable energy savings was notified. The study showed that that utilisation of POC as eco-friendly material in masonry grout is highly recommended based on performance and can provide a route to sustanable practices in the building industry.

Foam grout is a fluid, self-leveling, and lightweight material with excellent load spreading and thermal insulation properties. These properties have contributed to foam grout being considered over its regular cement/water grout counterparts for many projects. Although applied in many successful cases, not much has been done to compare foam and regular grout behavior in cold regions. This research focused on the compressive strength of both materials before and after freeze/thaw cycles. Specimens were cured for different durations in a moisture room and conditioned for diverse freezing/thawing cycles to assess short- and long-term performance. The impact of immediate freezing was also evaluated for both materials. Foam grout’s ability to resist cold environments was explained using test results and visual analysis. At the end of the process, a material cost versus strength analysis was conducted with the intent of providing a reliable source of information when selecting materials to fulfill minimum industry specifications.

Curtain grouting is an effective measure to cut off groundwater flow and reduce mine drainage and the risk of water inrush in open-pit mines. In this paper, an innovative technique is presented in which groundwater flow of the Chengmenshan copper open-pit mine in Jiangxi Province, China, is cut off by using a grout curtain made up of an environmentally friendly material from modified lake mud. An automated grouting control system is used to improve the efficiency of grouting while ensuring grout quality and mine safety. In order to investigate the characteristics of the modified lake mud slurry, a set of orthogonal experiments with three parameters and three levels L9(33) are carried out. The results show that the specific gravity of the basic lake mud slurry is the most significant factor in the effectiveness of grouting. Moreover, the curtain grouting effect of the Chengmenshan copper mine is proved to be excellent through the relationship curve of unit grouting quantity of ZD-I and ZD-II, dispersion coefficient, and water injection tests. It is found that the karstic fractures and tectonic fracture zone are effectively intercepted by a continuous and tight grout curtain located at the east of the mine pit. Our study helps to explore and develop an automated grouting control system and an environmentally friendly material for grout curtains in open-pit mines.

Ground heat exchangers are surrounded by grout material, making it one of the most important components in geothermal energy applications since it significantly affects the system's thermal performance. The current study reviews the different types of grout materials and compares their thermophysical properties. The most critical parameter is the grout's thermal conductivity in which it always presents a proportional relation with the system's efficiency. Numerous factors are involved in this review to ascertain theier impact on the grouts’ performance such as flowability, shrinkage, moisture content, freezing, heat capacity, strength, permeability, solubility and thermal imbalance. The different grouts compared are bentonite, cement, sand, graphite, controlled low-strength material, dolomite, and phase change materials. The literature shows that phase change materials are the best choices of grouting since they can provide high storage capacity, stability and temperature uniformity. The major problem of such materials is their low thermal conductivity. Thus, it is recommended to use composite phase change materials to enhance their thermal conductivity and increase the storage/retrieval rate.

A textile reinforced concrete (TRC) system has been widely used for repair and strengthening of deteriorated reinforced concrete (RC) structures. This paper proposes an accelerated on-site installation method of a TRC system by grouting to strengthen deteriorated RC structures. Four RC slabs were strengthened with one ply of carbon textile grid and 20 mm-thick cementitious grout. The TRC strengthened slab specimens were tested under flexure and the test results were compared with those of an unstrengthened specimen and theoretical solutions. Furthermore, the TRC strengthened specimens experienced longer plastic deformation after steel yield than the unstrengthened specimen. The TRC strengthened specimens exhibited many fine cracks and finally failed by rupture of the textile. Therefore, TRC system with the proposed installation method can effectively be used for strengthening of deteriorated RC structural elements. The theoretically computed steel yield and ultimate loads overestimate the test data by 11% and 5%, respectively.

This paper investigates the effectiveness of Steel-Reinforced Grout (SRG) jackets to strengthen shear critical reinforced concrete (RC) beams. Eleven RC beams were tested in three-point bending. Key parameters of investigation were the strengthening configuration (U- and fully-wrapped jackets), the density of the fabric (1.57 and 4.72 cords/cm) and the number of the strengthening layers (one and two). The test results demonstrated the efficiency of SRG jacketing in increasing both strength (up to 160%) and deformation capacity (up to 450%) of the shear critical beams. Expressions are proposed for estimating the effective strain of the SRG jacket.

In this paper, the seismic behaviors of four precast shear wall specimens and one cast-in-place shear wall specimen are investigated by pseudo-static test method. For the precast shear wall specimens, a new type of assembled rebar lap splices with prepared grout-filled holes and constraining spiral hoops were applied. Different vertical rebar lap splice positions and different rebar lap lengths at the horizontal assembly joints of the precast specimens were designed and fabricated in order to compare their seismic behaviors with the cast-in-place specimen. The geometric size and rebars of four precast specimens are totally same as those of the cast-in-place specimen. By analysis of test results including the load-lateral drift hysteresis curves, crack propagation and rebar strains, the failure modes, bearing capacity, hysteretic characteristics, ductility, rigidity degeneration and energy dissipation of all specimens were obtained and compared. The test results show that the precast concrete shear walls with horizontal assembly joints by this kind of rebar connection have good seismic behaviors and could be equivalent to the cast-in-place shear walls on the conditions of specified construction details.

This paper develops a new type of shear connection for steel-concrete composite bridges using Ultra-High Performance Concrete (UHPC) as the connection grout. The UHPC-grout strip shear connection is fabricated by preforming a roughened slot in the concrete deck slab, welding an embossed steel rib longitudinally to the upper flange of the steel girder, and casting the strip void between the slot and the steel rib with UHPC grout. The structural performance of the new connection was validated by two sets of experimental tests, including push-out testing of shear connectors and static and fatigue testing of composite beams. The results of push-out testing indicate that the UHPC-grout strip shear connection exhibits a significant improvement of ductility, ultimate capacity, and fatigue performance. The interface shear strength of the UHPC-grout strip connection is beyond 15 MPa, which is about three times that of the strip connection using traditional cementitious grouts. The ultimate capacity of the connection is dominated by the interface failure between the embossed steel and the UHPC grout. The results of composite-beam testing indicate that full composite action is developed between the precast decks and the steel beams, and the composite action remained intact after testing for two million load cycles. Finally, the trail design of a prototype bridge shows that this new connection has the potential to meet the requirements for horizontal shear.

Existing stone masonry buildings, constituting a significant portion of historical city centers, suffered often severe damages during seismic events. Traditional and innovative strengthening techniques can be applied to restore or enhance the structural capacity of these construction typologies. The objective of the present work was to evaluate the improvement given by different strengthening procedures to the shear behavior of stone masonry elements. In particular, an experimental campaign on stone masonry samples was carried out, in which the specimens were strengthened through different Fiber Reinforced Cementitious Matrix (FRCM) systems and grout injection. Non-destructive sonic tests were performed before and after the strengthening procedure to determine the efficiency of the grout injection. Then, the samples were subject to diagonal compression test with the objective of evaluating the influence of the different FRCM strengthening systems on the shear behavior, in terms of stiffness, load bearing capacity and failure mode. Comparisons between experimental results showed, on the one hand, a good correlation between the quality of the grout injection, analyzed through sonic tests, and the shear capacity of the retrofitted samples. On the other hand, the presence of the reinforcing fibers influenced mainly the post-peak behavior and determined a more ductile failure mode.

Purpose. To obtain the dependences of the stress-strain state (SSS) of foundations and bases during their restoration on the basis of grout-injected piles for further analysis of the influence of the location of reinforcement elements. Methodology. To determine the SSS parameters and to obtain its dependencies in the foundations and bases during their restoration based on grout-injected piles, a case without reinforcement (option 0) and three options for its reinforcement (Option 1, Option 2 and Option 3) were selected. Reinforcement was carried out with 4 m long soil-cement piles with a diameter of 0.5 m, created on the basis of grout-injected pile technology. Corresponding finite element models have been developed for four options. Their numerical analysis was carried out using a professional licensed SCAD complex. Findings. Contours and isofields of displacements in the models are obtained. The error between analytical calculation and numerical analysis is 3%, which indicates the adequacy of the developed model. The constructed dependences of the stress-strain state of foundations and bases during their restoration based on grout-injected piles indicate that the option that minimizes the level of displacements is Option 1. Analysis of vertical displacements proves that they decrease 2.05 times at the center point of the foundation (option 1), 1.87 times (option 2) and 1.59 times (option 3). Analytical patterns of the stress state show a steady drop in horizontal stresses by 2.77 times (option 1), 1.80 times (option 2) and 1.09 times (option 3) and a steady increase in vertical stresses by 6.20 times (option 1), 4.06 times (option 2) and 1.38 times (option 3). Originality. It lays in obtaining the dependencies of restoring the structures of foundations and bases based on grout-injected piles based on the numerical analysis of the stress-strain state of the “foundation-base” system. Practical value. It consists of the substantiation of the change in the stress-strain state with a variation in the location of the restoration elements created on the basis of grout-injected piles technology., Цель. Получить зависимости напряженно-деформированного состояния (НДС) фундаментов и оснований при их восстановлении на основе буроинъекционных скважин для дальнейшего анализа влияния расположения элементов усиления. Методика. Для определения параметров НДС и для получения его зависимостей в фундаментах и основаниях при их восстановлении на основе буроинъекционных скважин выбран случай без усиления (вариант 0) и три варианта его усиления (Вариант 1, Вариант 2 и Вариант 3). Усиление выполнено грунтоцементными сваями длиной 4 м диаметром 0,5 м, созданными на основе буроинъекционной технологии. Для четырех вариантов разработаны соответствующие конечно-элементные модели. Их численный анализ проводился с применением профессионального лицензионного комплекса SCAD. Результаты. Получены изолинии и изополя перемещений в моделях. Погрешность между аналитическим расчетом и численным анализом составляет 3 %, что свидетельствует об адекватности разработанной модели. Построенные зависимости НДС фундаментов и оснований при их восстановлении на основе буроинъекционных скважин свидетельствуют, что вариантом, который максимально снижает уровень перемещений, является Вариант 1. Анализ вертикальных перемещений доказывает, что они в центральной точке фундамента уменьшаются в 2,05 раза (вариант 1), 1,87 раза (вариант 2) и 1,59 раза (вариант 3). Аналитические закономерности напряженного состояния показывают устойчивое падение горизонтальных напряжений в 2,77 раза (вариант 1), 1,80 раза (вариант 2) и 1,09 раза (вариант 3) и устойчивый рост вертикальных напряжений в 6,20 раза (вариант 1), 4,06 раза (вариант 2) и 1,38 раза (вариант 3). Научная новизна. Она заключается в получении зависимостей восстановления конструкций фундаментов и оснований на базе буроинъекционных скважин на основе численного анализа НДС системы «фундамент–основание». Практическая значимость. Заключается в обосновании изменения НДС при вариации расположения элементов восстановления, созданных на основе буроинъекционной технологии., Мета. Отримати залежності напружено-деформованого стану (НДС) фундаментів та основ при їх відновленні на основі буроін’єкційних свердловин для подальшого аналізу впливу розташування елементів підсилення. Методика. Для визначення параметрів НДС і для отримання його залежностей в фундаментах та основах при їх відновленні на основі буроін’єкційних свердловин обрано непідсилений випадок (Варіант 0) та три варіанти його підсилення (Варіант 1, Варіант 2 та Варіант 3). Підсилення виконано ґрунтоцементними палями довжиною 4 м діаметром 0,5 м, створеними на основі буроін’єкційної технології. Для чотирьох варіантів розроблено відповідні скінченно-елементні моделі. Їх чисельний аналіз проводився із застосуванням професійного ліцензійного комплексу SCAD. Результати. Отримано ізолінії та ізополя переміщень в моделях. Похибка між аналітичним розрахунком та чисельним аналізом складає 3 %, що свідчить про адекватність розробленої моделі. Побудовано залежності НДС фундаментів та основ при їх відновленні на основі буроін’єкційних свердловин, які свідчать, що варіантом, який максимально знижує рівень переміщень, є Варіант 1. Аналіз вертикальних переміщень доводить, що вони в центральній точці фундаменту зменшуються у 2,05 рази (Варіант 1), 1,87 рази (Варіант 2) та 1,59 рази (Варіант 3). Аналітичні закономірності напруженого стану показують стійке падіння горизонтальних напружень у 2,77 рази (Варіант 1), 1,80 рази (Варіант 2) та 1,09 рази (Варіант 3) та стійке зростання вертикальних напружень у 6,20 рази (Варіант 1), 4,06 рази (Варіант 2) та 1,38 рази (Варіант 3). Наукова новизна. Вона полягає в отриманні залежностей відновлення конструкцій фундаментів та основ на базі буроін’єкційних свердловин на основі чисельного аналізу НДС системи «фундамент–основа». Практична значимість. Полягає в обґрунтуванні зміни НДС при варіації розташування елементів відновлення, створених на основі буроін’єкційної технології.

A grout sleeve connection is a typical kind of joint in prefabricated structures. However, for construction and manufacturing reasons, defects in this kind of joint are usually inevitable. The joint quality of a prefabricated structure has a significant influence on its overall performance and can lead to structural failure. Due to the complexity of various types of materials used in grout sleeve connections, traditional non-destructive testing methods, such as Acoustic Emission (AE), Ultrasonic Testing (UT), Guided Wave Testing (GW), are facing great challenges. The recent development of deep learning technology provides a new opportunity to solve this problem. Deep learning can learn the inherent rules and abstract hierarchies of sample data, and it has a powerful ability to extract the intrinsic features of training data in complex classification tasks. This paper illustrates a deep learning framework for the identification of joint defects in prefabricated structures. In this method, defect features are extracted from the acceleration time history response of a prefabricated structure using a convolutional neural network. The proposed method is validated by vibration experiments on a half-scaled, two-floor prefabricated frame structure with column rebars spliced by different defective grout sleeves.

This article develops an enhanced UHPC-grout shear connection for steel-concrete composite bridges with precast decks. The primary improvement is the use of ultra-high performance concrete (UHPC) as the connection grout. To validate the constructability and the mechanical performance of the new connection, two series of experimental tests (including grouting tests and push-out tests) were conducted. Results from the grouting tests show that both the pressure grouting method and the self-levelling grouting method are applicable to inject the UHPC grout into the channel void of the connection. Results from the push-out tests indicate that the advanced properties of UHPC allow for a significant improvement of the shear resistance of the adhesive connection over traditional cementitious grouts. The ultimate shear capacity of the adhesive connection is controlled by the interface shear strength between the embossed steel and the UHPC grout, with a cohesion value of approximately 5.87 MPa. Meanwhile, the residual frictional resistance can be taken as approximately one-half of the ultimate resistance. The results of the finite-element analysis show that the trilinear model is reasonable to simulate the shear-slip laws of the embossed steel-grout interface and the rough concrete-grout interface.

The seismic performance of grout sleeve splicing joint was investigated in this paper. Under the action of reversed cyclic loading, the numerical model of grout sleeve splicing joint was developed and was evaluated in terms of the variation of stress distribution, failure process, hysteresis loop, and energy dissipation. Numerical simulation result shows that the seismic performance of grout sleeve splicing joint mainly depends on the stress state of grouting material. In the first two loading cycles, the mechanical interaction with uneven distribution is the main load transmission mechanism from rebar to sleeve, and the fracture damage in grouting material near the end of sleeve is the main mode of energy dissipation. Between the second and the seventh loading cycles, through the stress redistribution, the grouting material in the area far from the end of sleeve gradually undertakes the energy dissipation function by means of fracture damage, and the obvious oblique compressive zone in grouting material is formed, which is the force transmission path from rebar to sleeve. Meanwhile, it decreases the elastic modulus of entire grouting material to a stable value.

Filling material is present around the segment lining when a shielded Tunnel Boring Machine is used to excavate a tunnel. The two-component grout is becoming lately one of the most used filling materials. Its mechanical properties evolve over time. Unfortunately, there are not many studies in the literature on the specific mechanical characteristics of these materials. This work presents the results obtained from an extensive laboratory test campaign that allowed to fully characterize the two-component filling material during the setting period. In particular, the values of the stiffness and resistance parameters were obtained over time, where uniaxial compression tests and oedometer tests were carried out. A detailed study of the effect of the presence of the filling material on the behavior of the support system (segmental lining + filling material) was developed for two of the most widespread analytical methods for the analysis of the behavior of tunnels and structures of support: the convergence-confinement method and the Einstein and Schwartz method. Subsequent parametric analyses made it possible to consider the variability of the influencing parameters within the typical variability ranges obtained from the laboratory test campaign or known from the available scientific literature. From the study carried out, it was possible to note that it is necessary to consider the presence of the filling material in the evaluation of the stiffness of the support system, when using the convergence-confinement method to estimate the loads acting on segmental lining. In this regard, it is necessary to have a reliable estimate of the elastic modulus of the filling material in the period of loading of the segmental lining. On the other hand, the presence of the ring of filling material is negligible when evaluating the state of stress of the segmental lining with specific methods capable of considering the rock-support interaction. In particular, adopting the Einstein and Schwartz method, it is possible to define the bending moments and normal forces acting in the support structure, referring to the stiffness parameters of the segmental lining alone.

Based on the sequential coupling method and the temperature rise curve according to ISO-834, the ABAQUS numerical models of grout sleeve splicing joint was established. At a different fire exposure time, the temperature field and ultimate tensile strength of splicing joint were numerically analyzed. Meanwhile, by means of the stress distribution analysis of grouting material, the failure mechanism of splicing joint was put forward. Numerical simulation result shows that under the action of ultimate tensile load, the Mises stress of rebar decreases gradually along axial direction from uploaded end to non-loaded end, the Mises stress of sleeve increases gradually along axial direction from sleeve end to middle cross section, and the stress distribution of grouting material is relatively uniform. Furthermore, with the increase of fire exposure time, the stress state of grouting material changes from trip-direction compressive state to trip-direction tensile state gradually, which leads to the ultimate tensile load of grout sleeve splicing joint decreases.