Chun-An Tang

Large evaporite provinces (LEPs) represent prodigious volumes of evaporites widely developed from the Sinian to Neogene. The reasons why they often quickly develop on a large scale with large areas and thicknesses remain enigmatic. Possible causes range from warming from above to heating from below. The fact that the salt deposits in most salt-bearing basins occur mainly in the Sinian-Cambrian, Permian-Triassic, Jurassic-Cretaceous, and Miocene intervals favours a dominantly tectonic origin rather than a solar driving mechanism. Here, we analysed the spatio-temporal distribution of evaporites based on 138 evaporitic basins and found that throughout the Phanerozoiceon, LEPs occurred across the Earth’s surface in most salt-bearing basins, especially in areas with an evolutionary history of strong tectonic activity. The masses of evaporites, rates of evaporite formation, tectonic movements, and large igneous provinces (LIPs) synergistically developed in the Sinian-Cambrian, Permian, Jurassic-Cretaceous, and Miocene intervals, which are considered to be four of the warmest times since the Sinian. We realize that salt accumulation can proceed without solar energy and can generally be linked to geothermal changes in tectonically active zones. When climatic factors are involved, they may be manifestations of the thermal influence of the crust on the surface.

An exponential creep model on the basis of material properties degradation law was applied in the paper to simulate the rheological behavior of inhomogeneous rock and time-dependent response of rock tunnels. The primary, secondary, and tertiary creep regimes associated with damage were observed in the simulations, indicating that the macroscopic creep failure is linked to clusters of microstructure damage evolution at a mesoscale. Simulations on the time-dependent response of tunnels in the long-term under different coefficients of lateral pressure show that creep deformation and damage occurs in rock mass at tunnel sidewalls around rock mass under the coefficient of lateral pressure less than unity, whereas creep deformation and damage occurs at the roof and floor of the tunnel under the coefficient of lateral pressure larger than unity. Under the hydrostatic pressure of the coefficient of lateral pressure equal to unity, creep deformation and damage randomly occurs and damage localization forms ...

A micromechanical model based on material properties degradation law was proposed in the paper to simulate the time-dependent damage and deformation and delayed failure of rock materials in tunnels. The time-dependent degradation law of material properties, an exponential empirical relation between degradation of material properties and applied stress, is used at the scale of each element to simulate its damage. The primary and tertiary creep regimes associated respectively with a degradation and increase of the rate of strain, damage event and energy release were observed in the simulations. The time-dependent deformation and delayed failure of tunnels on the long-term under different coefficients of lateral pressure was studied to investigate the failure patterns and mechanism of tunnels. This model can reproduce rheological properties including the three creep regimes and associated damage evolution of rock in tunnels, which is of great help to investigate long-term stability of tunnels and to prevent associated rock hazards in tunneling engineering.