Factors Influencing the Load-Bearing Capacity of Rock as Base Material for Post-Installed Anchors

In the case of fastenings on rock, as a result of the variability, it is quite difficult to make a preliminary assessment of the load-bearing capacity of rock as a base material. This paper therefore investigates which rock parameters next to an anchor position have an influence on the load-bearing capacity. For this purpose, tests are carried out on post-installed anchors in different lithologies in eastern Austria. It can be shown that the joint weathering has an influence on the load-bearing capacity of post-installed anchors and conclusions can be made about joint weathering by means of rebound hammer. Rebound values can therefore also be used to draw conclusions about the rock quality as a base material for post-installed anchors. Nevertheless, a combined optical assessment of the base material is recommended as an adequate method.

Analysis of the Behaviour of Rocks Under Cyclic Loads

The cyclic load applied to civil and mining structures can lead to a reduction of the materials’ strength, different from that which would occur with a monotonous load. Numerous cases can be found where the decay of the rock parameters subjected to this type of stress leads to progressive or sudden collapse: among them, tunnel walls, pillars and slabs in mining operations, roads with a heavy vehicle transit, abutments of bridges and dams can be quoted. The topic can therefore be fundamental for a correct structural design, to avoid problems during the life of the structure. However, given the heterogeneity of the rock materials and the difficulty of their characterization under this aspect, an unequivocal analysis is hardly achievable. Then, the discussion initially develops through a general historical review of the concept of fatigue, with a synthetic collection of case histories. The laboratory tests on rock samples are then examined and the most important results obtained are discussed. Finally, a comparison between different types of tests is proposed. The experimental data are expressed through the Wӧhler diagram. The goal is to fill the lack of design codes or standards in the field of cyclic stresses applied to rock materials, the understanding of its effect being of great interest in order to apply suitable parameters in the design phase.

The Influence of the Physical-Mechanical Parameters of Rock on the Extent of the Initial Failure Zone under the Action of an Undercut Anchor

This paper presents the results of a numerical FEM (Finite Element Method) simulation of the formation of a rock failure zone in its initial stage of development. The influence of rock parameters, such as the Young’s modulus, Poisson’s ratio and friction factor of the rock in the contact zone with the working surface of the undercut anchor head, were taken into account. The obtained results of FEM simulations were compared with the results of field tests conducted in Polish mining plants extracting rock raw materials.