Alireza Entezam

Fully grouted rock bolts are widely used for ground control in underground excavations and slopes. Their behaviour under axial and shear loading is governed by bond-slip at the interfaces, confinement, embedment length, annulus thickness and bolt profile, which together control peak capacity and post-peak load transfer. Although many studies have examined individual aspects of this behaviour, a consolidated assessment of axial and shear load-transfer mechanisms remains limited. This review addresses that gap by systematically reviewing Scopus-indexed literature from 1988 to 2025. An initial broad search returned 977 records on rock-bolting systems. After applying focused search terms, exclusions and manual screening, 122 articles were selected for detailed bibliometric and content-based analysis. VOSviewer keyword mapping identified three main research clusters: (a) grout, pull-out testing,analytical modelling, shear stress, and shear strength; (b) finite-difference modelling and failure mechanisms; and (c) numerical simulation using the finite element method. The review also compares publication trends, leading contributors and the main technical themes shaping the field. . The findings revealed that the axial behaviour is mainly bond-controlled, whereas joint conditions, boundary constraints, and local bending more strongly influence shear behaviour. These differences highlighted the need for careful interpretation of test data and for modelling approaches that distinguished between the axial and shear load transfer mechanisms in fully grouted rock bolts.

Conventional cementitious grouts, widely used for underground reinforcement and structural repair, rely heavily on Portland cement, a material responsible for nearly 7% of global CO₂ emissions and significant resource depletion. Addressing this environmental and material-efficiency challenge, this study develops and evaluates novel sustainable grout formulations that partially replace cement with recycled waste glass (WG), tyre rubber waste (TRW), and construction and demolition waste (CDW). By systematically linking mechanical, rheological, and microstructural performance, the research bridges a key gap between sustainability-driven material substitution and the performance requirements of practical grouting applications. Grout mixtures incorporating 0–20% WG, 0–3% TRW, and 0–10% CDW were evaluated for rheological behaviour and unconfined compressive strength (UCS). All modified grouts maintained shear-thinning properties but exhibited significantly reduced viscosity, enabling lower water demand. Notably, WG-enhanced grouts preserved or even improved UCS. For example, 2.5–5% WG substitution resulted in minimal strength loss, yielding up to 97% of the 70.5 MPa control strength. When adjusted for reduced water content, these mixes achieved a 10.6% UCS increase. TRW grouts peaked at 55.2 MPa with 0.75% inclusion, while CDW caused only minor strength drops at 2.5–5%. Enhanced flowability (lower viscosity/yield stress) compensated for some strength reductions. Microstructural analysis revealed that WG improved matrix density via pozzolanic activity and filler effect, while TRW and CDW influenced pore structure. Beyond their laboratory performance, these findings underscore the practical potential of recycled waste-based grouts to reduce cement consumption, lower embodied carbon, and divert waste streams from landfills. Such formulations retain pumpability and mechanical performance while offering viable alternatives for ground reinforcement, structural repair, and sustainable construction applications. Overall, the integration of WG, TRW, and CDW demonstrates a promising pathway toward lower-impact cementitious grouts that meet both engineering and environmental demands.

This study follows the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) framework, combining bibliometric mapping and mechanistic synthesis to provide a unified evidence-based review of cementitious grouts in ground support systems. The bibliometric layer quantifies global research activity, while the systematic synthesis interprets how material composition, pozzolanic chemistry, and rheology control grout performance and sustainability. This study presents a systematic review complemented by bibliometric analysis to synthesise global research trends and technical advances in grout design. A dataset of 1200 articles was screened, from which 101 journal papers met the inclusion and quality criteria and were analysed in detail. Co-occurrence mapping of author keywords was then used to identify research hotspots and collaborative structures. The bibliometric analysis revealed that Construction and Building Materials is the leading outlet. Co-authorship mapping highlighted strong international collaboration, with leading clusters centred on supplementary cementitious materials, rheology, and microstructural analysis. The technical review consolidates five interrelated themes: reinforcement mechanisms, cementitious grouts, chemical reactions and pozzolanic reactivity, fresh and hardened state properties, and microstructural development with rheological behaviour. Across these themes, supplementary cementitious materials and waste-derived binders have emerged as central to both performance enhancement and carbon reduction, while advanced experimental and modelling techniques have refined understanding of microstructural evolution and grout–rock–bolt interactions. Collectively, the findings underline that cementitious grouts are no longer passive fillers but engineered composites designed for mechanical efficiency, durability, and environmental responsibility. Key research gaps remain in the standardisation of rheological testing, long-term durability under complex field conditions, and integration of life-cycle assessment into grout development. Addressing these challenges will be critical for the design of next-generation grouts capable of meeting the dual imperatives of safety and sustainability in mining and civil engineering.

Fully grouted rock bolts play a vital role in stabilising underground excavations, particularly in corrosive environments where material properties, geometric configuration, and installation conditions influence their load transfer performance. Although the practical importance of fully grouted fibreglass rock bolts is well recognised, quantitative evidence on their axial load transfer mechanisms remains limited. Prior work has primarily centred on steel rock bolts, with few studies on how embedment length, grout stiffness, interface roughness and confining stress govern bond mobilisation in fully grouted fibreglass rock bolts, indicating a clear need for further scientific investigation. This study examines the axial load transfer and shear behaviour of fully grouted fibreglass rock bolts, focusing on the effects of embedment length (EL), grout properties, and boundary conditions. A comprehensive series of laboratory pull-out tests were conducted on two widely used Australian glass fibre reinforced polymer (GFRP) rock bolts, TD22 and TD25, with diameters of 22 mm and 25 mm, respectively, under varying ELs and grout curing times to evaluate their axial performance. Additionally, single shear tests and uniaxial compressive strength (UCS) tests were conducted to assess the shear behaviour of the rock bolts and the mechanical properties of the grout. The results showed that increased EL, bolt diameter, and grout curing time generally enhance axial capacity. With grout curing from day 7 to the day 28, the influence of embedment length became increasingly pronounced, as the axial peak load rose from 35 kN (TD22-50, 7 days) to 116 kN (TD22-150, 28 days) and from 39 kN (TD25-50, 7 days) to 115 kN (TD25-150, 28 days), confirming that both longer bonded lengths and extended curing significantly enhance the axial load-bearing capacity of fully grouted GFRP rock bolts. However, the TD22 rock bolts exhibited superior shear strength and ductility compared to the TD25 rock bolts. Also, a calibrated distinct element model (DEM) was developed in 3DEC to simulate axial load transfer mechanisms and validated against experimental results. Parametric studies revealed that increasing the grout stiffness from 5 e7 N/m to 5 e8 N/m increased the peak load from 45 kN to 205 kN (approximately 350%), while reducing the peak displacement, indicating a shift toward a more brittle response. Similarly, increasing the grout-bolt interface roughness boosted the peak load by 150% (from 60 kN to 150 kN) and enhanced residual stability, raising the residual load from 12 kN to 93.5 kN. In contrast, confining stress (up to 5 MPa) did not affect the 110 kN peak load but reduced the residual load by up to 60% in isotropic conditions. These quantitative findings provide critical insights into the performance of GFRP bolts and support their optimised design for underground reinforcement applications.

The main objective of implementing primary ground-controlling methods, such as applying rock bolting systems, is to increase the strength of surrounding rock mass. Among all rock bolting systems, fully grouted rock bolting systems are the most popular and reliable retaining systems due to their simplicity, availability of materials, ease of installation in the field, and cost-effectiveness. While these types of rock bolts experience both axial and shear forces, understanding their response to axial loads remains complex and dependent on several factors. Extensive research has addressed the overall behaviour of the fully grouted rock bolting system, but a systematic review of the axial load transfer mechanism and its impact on overall performance is lacking. This study addresses this gap by employing a bibliometric analysis of 77 peer-reviewed publications to explore the current state of knowledge regarding the axial load transfer mechanism in fully grouted rock bolting systems. The analysis identifies influential journals, publishers, researchers, highly cited articles, and emerging keywords within this field. Furthermore, it reveals three key parameters significantly impacting the axial behaviour: (a) rock mass and boundary conditions, (b) mechanical behaviours of the grouts, and (c) the geometry and surface profile of the rock bolt. These parameters are subsequently discussed in detail, highlighting their influence on the axial performance of the system. Finally, this article concludes by suggesting promising directions for future research.