The application of grouting materials has increased significantly in recent decades. In order to stabilize fractured rock and to reduce the permeability of a rock, the fissures are filled with grouting material. Different grouting materials can be used for this purpose, such as cement, polyurethane resin and acrylate gel. Through the grouting of rock fissures, the physical properties of the rock can be changed. Several parameters may affect the load bearing capacity of the grouted rock, such as properties of the grouting materials, stress level, fracture shape and orientation. Usually, by grouting, the cohesion in the fissure is increased and the friction angle is reduced.

In this study, two acrylate gels and a polyurethane resin were selected as test material. The acrylates have an extremely low viscosity, close to the viscosity of water. Therefore, it is possible to grout the acrylates in extremely tight joints. The material behaviors of the selected grouting materials were experimentally investigated and numerical simulations were used to compare the bearing capacity of the fractured rock before and after grouting. Different grouting materials, load variants and fracture orientations were compared. Thus, it was possible to define a new safe application limit for the investigated grouting materials.

1 Introduction

Rock grouting is used to increase the strength of the rock and to seal the ground. Acrylate gels or resins are particularly suitable as grouting materials, because they can penetrate even the smallest fractures. Rock grouting modifies the mechanical properties of the rock and as a consequence it requires a reassessment of the bearing capacity of the rock. It is quite difficult to assess the strength increase of the rock after grouting, because there are many influencing factors like the rock stress state, the geometry of the gap and finally the used grouting material. In spite of these numerous influencing factors, it is the motivation of this research work to be able to make a qualitative statement on the effects of rock grouting on the strength of the rock mass and thus also on the load bearing capacity.

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