Seismic Wave Propagation Characteristics and Their Effects on the Dynamic Response of Layered Rock Sites

To investigate the seismic response of layered rock sites, a multidomain analysis method was proposed. Three finite element models with infinite element boundaries for layered sites were analysed. The results of this multidomain analysis show that stratum properties and elevation have an impact on wave propagation characteristics and the dynamic response of layered sites. Compared with the rock mass, the overlying gravel soil has a greater dynamic amplification effect at the sites. A time domain analysis parameter PGA(IMF) was proposed to analyse the effects of different strata on the seismic magnification effect of layered sites, and its application was also discussed in comparison with PGA. According to the frequency domain analysis, the interface of the rock mass strata has a low impact on the Fourier spectrum characteristics of the sites, but gravel soil has a great magnification effect on the spectrum amplitude in the high-frequency band (≥30 Hz) of waves. Moreover, the stratum properties have a great influence on the shape and peak value of the Hilbert energy and marginal spectrum at layered sites. When waves propagate from hard rock to soft rock, the peak value of the Hilbert energy spectrum changes from single to multiple peaks; then, in gravelly soil, the Hilbert energy spectral peak, its nearby amplitude and the amplitude in the high-frequency band (28–36 Hz) are obviously amplified. The frequency components and amplitude of the marginal spectrum become more abundant and larger from rock to gravelly soil in the high-frequency band (28–35 Hz).

Modeling of stress states in intact layered rock massifs

Предложена структурная модель анизотропной среды для расчета напряженнодеформированного состояния в нетронутых массивах горных пород, которая учитывает ряд горнотехнических и горно-геологических факторов. Результаты аналитического решения позволили объяснить известные из практики натурных наблюдений факты (возможность превосходства горизонтальных напряжений над вертикальными, кусочно-линейный характер напряжений и т.д.), которые находились в противоречии с широко распространенными гипотезами о распределении напряжений в породных массивах. A structural model of an anisotropic medium is proposed for calculating the stressstrain state in intact rock massifs, which takes into account a number of mining and geological factors. The results of the analytical solution allowed us to explain the facts known from the practice of field observations (the possibility of the superiority of horizontal stresses over vertical ones, the piecewise linear nature of stresses, etc.), which were in contradiction with the widespread hypotheses about the distribution of stresses in rock massifs.

Bedding Plane Effects on Mechanical Behavior of Surrounding Rock in Mountain Tunneling

The layered rock showed the characteristics in Mountain tunnel, Yunnan. A series of uniaxial compression tests and variable angle shear tests were carried out, and the aim was to investigate the effect of the bedding on its mechanical parameters and failure modes. The test results show that the uniaxial compressive strength, elastic modulus, and Poisson's ratio of layered rock present a U-shaped distribution with the increase in bedding orientation from 0° to 90°. All of them have a maximum when the bedding orientation is 0° and a minimum when the bedding orientation is 45°. The failure modes of layered rock can be summarized into three types: the fracture tensile failure parallel to the weak plane of bedding; the shear slip failure along bedding weak plane; and tension-shear composite failure between bedding weak plane and matrix. Based on the testing data and analysis results, it can be concluded that the layered rock specimen with different bedding orientations is an important reason for the anisotropy of mechanical parameters and failure modes.