157 / 2021-10-24 00:34:01

Experimental and numerical studies of shock-induced fracture and fragmentation of rocks

3D Numerical Simulation,fracture propagation control

Rock excavation by blasting method is commonly used in mining or tunnelling area around the world. Two aspects related with rock excavation are a point of interest: to reduce the cost efficiency of this process and increase safety [1-3]. Nowadays, a numerical methods supports an engineers to optimize the blasting technique with proper design of borehole pattern and geometries to reduce costs, as well as to verify how destress blasting reduces the stress in the surrounding rock around the tunnel. However, this task requires a proper numerical modeling of rock fragmentation, especially the crack propagation in the rock volume. This may be considered with use of properly calibrated constitutive model that will give the reliable results in both: laboratory and field scale tests.

In this paper a Johnson Holmquist Ceramics (JH2) [4] model is used due to its pressure and strain rate dependency as well as damage calculation resulting in high brittleness of modeled material which corresponds to behavior of dolomite rock. This model, validated with mechanical tests in small and medium scale is used to simulate of cut-hole and destress blasting in minings.

Both problems, due to large volume of rock that have to be simulated were simplified to 2D loading cases with proper boundary conditions. A confining pressures were depth dependend  and were applied vertically and horizontally. High explosive (HE) were reproduced with SPH particles  taking into account the interaction with the rock medium by a contact algorithm.

As the result, the effect of delay between HE initiations was investigated and optimal delay was obtained to reduce the wave interference. Simultaneously, the effect of explosion on residual stresses in rock massif was measured. It was proven, that the stresses decreases mostly at the distance equal to the horizontal drilling range of borehole. Also a different angles of a borehole were investigated to obtain the expected trend in stress change.





References

[1] DICK, R. A., FLETCHER, L. R., D’ANDREA, D. V., Explosives and Blasting Procedures

Manual, Information Circular 8925, US Department of Interior Office of Surface Mining Reclamation and Enforcemen, 1-112

[2] Baranowski P, Mazurkiewicz Ł, Małachowski J, Pytlik M., 2020. Experimental testing and numerical simulations of blast-induced fracture of dolomite rock, Meccanica (2020) 55:2337–2352.

[3] Baranowski P, Damaziak K, Mazurkiewicz Ł, Mertuszka P, Pytel W, Małachowski J, Pałac-Walko B, Jones T. 2019. Destress blasting of rock mass: multiscale modelling and simulation. Shock Vib. 2019:1–11

[4] Baranowski P, Damaziak K, Mazurkiewicz Ł, Mertuszka P, Pytel W, Małachowski J, Pałac-Walko B, Jones T. 2019. Destress blasting of rock mass: multiscale modelling and simulation. Shock Vib. 2019:1–11