Virtual reality assisted techniques in field tests and engineering application of the mechanical parameters of a horizontally layered rock mass

The mechanical indices used to describe the anisotropy of layered rock mass are numerous and difficult to be measured. Take the medium - thick horizontal layered limestone rock mass as an example, rock mechanical tests, engineering geological survey, field tests, numerical back-analysis were done to obtain transverse isotropic deformation parameters and strength indices. Normal and transverse moduli of elasticity of rock mass could be preliminarily confirmed by rock uniaxial compression tests, RQD, and empirical formula. Then vertical compression testing of layered rock mass, vertical and horizontal plate bearing tests, and numerical back-analysis were conducted to determine the other deformation parameters. These parameters include normal and transverse moduli of elasticity, normal and transverse Poisson’s ratio, and shear modulus of the rock mass. The cohesion and internal friction angle of the rock mass were then confirmed by direct shear and shear testing. Test results of bidirectional elasticity modulus showed the obvious anisotropy of the layered rock mass. Engineering application indicated that vault settlement was the main deformation mode of the horizontally layered surrounding rock. This differed from the homogeneous rock. Rock falling and delamination readily occurred in the arch of the tunnel.