Failure process analysis of spalling failure—Comparison of laboratory test and numerical modelling data

Abstract

This paper presents a comparison of laboratory tests and numerical modelling results for evaluation of spalling failure in hard rock. The aim of this paper was to evaluate if the failure and deformation (i.e., strain at crack initiation, crack damage and peak strength stages) process in the zone of spalling failure of two real excavations can be predicted by using strain data from rocks tested in laboratory. Data such as axial strain and lateral strain quantities from uniaxial compressive laboratory test performed on Fennoscandian hard rocks were used. Numerical modelling of these excavations using Phase2 was conducted. Volumetric strain and maximum shear strain were chosen as indicators of the depth and shape of the spalling failure developing in the walls and roof of the excavations. Quantities within the spalling failure zone such as volumetric strain, maximum shear strain, and major and minor principal strain, were calculated, and compared to the failure-deformation data of limestone and quartzite (from laboratory tests). This paper shows that the failure process of hard rock excavations can be predicted by using laboratory test data. This paper further demonstrated that the onset of cracking calculated from laboratory tests can be related to the in situ crack initiation strain.