This paper updates the recent development of rock dynamics research conducted by the Underground Technology and Rock Engineering (UTRE) research program in Nanyang Technological University, Singapore. It includes dynamic tests for granite rock specimen and various artificial rock joints, development of numerical manifold method and its application in rock slope stability analysis, stress wave propagation in jointed rock mass, and prediction of ground motions induced by underground explosion, etc. It has been found that the rock strengths including uniaxial/triaxial compression, shear and tensile splitting strengths all depends on the strain rate applied to the specimen. To analyze dynamic deformation of rock masses, the numerical manifold method has been extended to a three dimensional version and various slope stability problems have been studied. A visco-elastic equivalent medium model has been put forward to analyze stress wave propagation in jointed rock mass. It is validated that the proposed equivalent medium model gives more reasonable results in describing wave transmission and attenuation in jointed rock mass. A virtual wave source model is proposed to consider the wave reflections at rock joints. Wave propagation theory by adopting the principle of momentum conservation is used to predict the ground motion induced by an underground explosion. It is found that the analytical solution gives an accurate prediction of the ground motions in terms of peak ground motions and wave forms.
Rock dynamics is one of the strategy research areas of the Underground Technology and Rock Engineering (UTRE) research program in Nanyang Technological University, Singapore. The UTRE is a long term joint research program between Nanyang Technological University (NTU) and Defence Science and Technology Agency (DSTA), Singapore. The first phase of five years of the UTRE research program has been completed in May 2009 and it has been successfully extended to the second phase for another four years in 2009. In the past a few years, various fundamental rock dynamics research has been conducted under the UTRE research program. It include rock dynamic testing and modelling, rock joint dynamic testing and modelling, development of discontinuous deformation analysis methods, analysis of stress wave propagation in jointed rock mass, and scaled and field blast tests, etc. The present paper mainly updates the results related to
rock and rock joint dynamic properties,
numerical modelling of rock mass,
stress wave propagation in jointed rock mass,
theoretical derivation of underground explosion induced ground motion.
In the rock and rock joint dynamic properties part, we mainly tested the dynamic properties of granite rock specimen which were collected from the Bukit Timah formation covering about one-third on the Singapore geological map. Dynamic uniaxial/triaxial compression, shear and tensile splitting tests have been carried out to the granite specimen. Artificial joints using dry and saturated sand or clay layers have also been tested by using modified split Hopkinson pressure bars made by granite cores. In the numerical modeling of rock mass deformation, the numerical manifold method is adopted and it has been successfully extended to a three dimensional version.