Tunnels have been the necessary element of the modern construction industry. Due to their importance for the infrastructural and economic point of view, several tunneling projects are being carried ...out. The present numerical study investigates the response of rock tunnel under static and surface blast loading. The response of tunnel have been observed in three different types of rocks predominantly observed in Himalayan mountains, i.e. Phyllitic Quartzite, Quartzitic Phyllite and Migmatic Gneiss. The study has been carried out on a 3D numerical model of dimension 70 x 70 x 80 m. The tunnel has 11 m diameter with concrete liner of 0.45 m initial thickness and the overburden has been applied in the form of pressure initially as a height of 50 m of overburden rock. The overburden pressure and the lining thickness have been varied under static loading conditions. In addition, the shape of the tunnel cross-section has been varied as Arch, Circular, Rectangular and Horseshoe. The surrounding rocks have been modeled as a nonlinear elastoplastic constitutive material model, with concrete liner as Mohr-Coulomb (M-C) and Concrete Damage Plasticity model respectively. Initially, the response of the tunnel has been observed under static loading conditions for different overburden pressure and tunnel cross-section. Later, a surface blast analysis has been carried out using CONWEP method with source at a standoff distance of 10 m from the ground surface. The blast analysis has been carried out for initial conditions of concrete liner and overburden pressure. It has been concluded that under static loading, circular shape is the safest rock tunnel among all four shapes. However, Arch shape of rock tunnel provides maximum resistance under blast loading condition.
The application package previously developed at the Pisarenko Institute of Problems of Strength of the National Academy of Sciences of Ukraine for the numerical calculation of the dynamic ...non-axisymmetric three-dimensional stress-strain state and strength of multilayer helically orthotropic cylinders of finite length under impulsive loading was modified by the CONWEP method for load due to the explosion of a spherical explosive charge arbitrarily located in air inside a cylinder. Its accuracy was investigated by the variation of grid size, the number of the terms of Fourier expansions of unknowns, boundary conditions, charge coordinates and other input parameters. The three-dimensional dynamics and strength of composite and metal-composite cylinders loaded by a non-axisymmetric internal explosion were studied. Strength was determined by the generalized Mises criterion. The influence of displacement of the explosive charge relative to the center of symmetry of the cylinder along the radius and axis on stress-strain state and strength was studied. It is shown that at the constant relative mass of the charge, metal-composite cylinders can be made equally strong by increasing the thickness of the metal layer from zero to a quarter of the shell thickness, while increasing the mass of the charge by a factor of almost two. The inefficiency of the use of reinforced composites with low ultimate tensile strength across fibers in such structural elements has been established. It is shown that in some cases adding an outer composite layer to the inner steel shell leads not to an increase but on the contrary to a decrease in the strength of the object as a whole.
