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Rock reinforcement with different types of rock bolts can be calculated with analytical solutions based on the theories of the ground reaction curve. Analytical solutions of the behaviour of the rock support with fully grouted bolts (dowel) are presented as well as with prestressed anchor bolts. Elastic as well as plastic behaviour of the bolts and the rock mass can be considered. The failure state of the rock mass can be brittle or perfect plastic. Based on two calculated examples the difference between prestressed anchor and grouted bolt in squeezing rock are discussed.

Friction rock bolts or stabilizers have been tested and compared with conventional prestressed mechanical bolts by the Mining Division of the Norwegian Institute of Technology during the periode 1979–1982. Practical tests including convergence measurements and pull tests have been carried out in three different mines. Both Split sets and Swellex bolts have been investigated. Convergence measurements show that Split Set bolted sections of drifts have slightly higher convergence than conventionally bolted sections. Pull out tests show that the pull force needed for Swellex bolts is at least three times that of Split Sets. Bit diameter wear creates considerable problems with the installation of Split Sets as the hole diameter becomes too small. This has in turn made it difficult to get the systems accepted by the miners. The Swellex system is virtually independent of the hole diameter within quite large limits, and the system was much easier accepted by the miners. Systematically friction bolted roof sections seem to be fully equivalent to or even better than conventionally bolted sections.

Shear test have been performed in a large shear rig on Swellex bolts, massive steel bolts, massive and tube bolts of fiber glass. The inclination of the bolts to a joint plane in jointed rock, the normal stress and the type of blocks for bolt installation were varied. Shear test results show that the modern tube bolts (Swellex and Split set bolts) allow larger shear displacements before failure than is the case with massive rock bolts. However, tube bolts show lower shear resistance than massive rock bolts for the same size of cross section area. The reinforceing capacity for tube bolts of fiber glass is less than that of steel bolts. The inclination of the bolt to the shear surface joint plane is found to have a strong influence on shear resistance and shear displacement before bolt failure. An inclination in which the bolt is loaded in shear and tension offer the maximum resistance to shear failure.

U.S. Bureau of Mines research is developing technology that can lead to reduced accidents from roof falls in underground mining operations. Research efforts have focused on the development of systems to install rock reinforcements remotely, and in studies to define the interaction mechanics between rock mass and support systems. Remote manual roof bolters, a fiberglass epoxy-resin pumpable roof-bolting system, and automated bolter modules, all of which utilize flexible shaft drills and bolt benders/inserters, are being developed. These systems provide remote longer-than-seam-height drilling and bolting capabilities. Systems are also being developed to grout rock bolts remotely in mine roof through application of a slurry injection system using low-cost, fast-setting gypsum cement. A device to evaluate the bond quality of full-column grouted bolts nondestructively is also under development. A full-scale geotechnical model of a coal mine entry, in correlation with finite-element analysis, is being used by the Bureau for research in the area of roof-bolt support interaction mechanics.

Two corrosivity classification systems are proposed for the underground environment with relation to the corrosion of rock bolts. The corrosivity of the underground environment is judged on the bas ...

In the paper, the authors propose a new quantitative assessment method of rock condition based on observational classification obtained at the tunnel face, which will enable to know either strength or deformability of rock mass, further more appropriate amount of rock bolts, thickness of shotcrete and size and pitch of steel ribs just after the blasting procedure. The study is confirmed by the database of up to the 6,101 sections of tunnels constructed by Japan Highway Public Corporation.

In general Swellex bolts strengthen the rock mass through a combination of friction and mechanical interlock at the rock-bolt interface. The anchoring mechanism of the Swellex bolt is actually diff ...