Mechanical Behavior of Grouted Rock Bolts in Underground Engineering
Summary
Grouted rock bolts represent a cornerstone of ground support in tunnels, mines and deep excavations, enhancing stability by anchoring unstable rock masses. Their mechanical behaviour is governed by the interaction between the steel bolt, cementitious grout and surrounding rock. Under axial loading, load is transferred from bolt to grout via the anchor–grout interface and subsequently from grout to rock through the grout–rock interface. Failure may occur by tensile rupture of the steel, debonding at one of the interfaces or shear failure of the rock mass. Key parameters influencing performance include grout compressive strength, water–cement ratio, bolt geometry, embedment length and in situ stress conditions such as confining pressure. Temperature, loading rate and pretension further modulate bond strength and strain distribution. Recent advances combine full-scale field tests, laboratory pull-out experiments, analytical modelling and numerical simulation to elucidate stress and strain profiles along the anchorage zone. Distributed sensing techniques now offer high-resolution monitoring of axial force and shear stress, enabling more accurate prediction of bolt behaviour. Understanding these mechanisms is vital for optimising support design, ensuring safety and economic efficiency in underground projects worldwide.
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Mechanical Behavior of Grouted Rock Bolts in Underground Engineering publication trend
The graph below shows the total number of articles in mechanical behavior of grouted rock bolts in underground engineering across all publications each year (not limited to Nature Index journals).
Technical terms
Grouted rock bolt: A reinforcement element consisting of a steel bar fully encapsulated in cementitious grout within a drilled hole to stabilise rock masses.
Bond strength: The shear resistance developed at an interface, typically expressed as a fraction of grout or rock uniaxial compressive strength.
Embedment length: The length of bolt fully grouted and in contact with the rock mass, critical for ensuring adequate load transfer.
Confining pressure: The external stress applied to the rock mass surrounding the bolt, influencing the load transfer and bond behaviour.
Pull-out test: A laboratory or field experiment in which a grouted bolt is subjected to axial loading until failure to characterise bond and anchorage performance.
References
- Full-scale pullout tests of rock anchors in a limestone quarry focusing on bond failure at the anchor-grout and grout-rock interfaces. Journal of Rock Mechanics and Geotechnical Engineering (2023).
- A new analytical model for stress distribution in the rock bolt under axial loading. International Journal of Rock Mechanics and Mining Sciences (2024).
- Pull-out and Critical Embedment Length of Grouted Rebar Rock Bolts-Mechanisms When Approaching and Reaching the Ultimate Load. Rock Mechanics and Rock Engineering (2021).
- The application of distributed optical strain sensing to measure the strain distribution of ground support members. Facets (2018).
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