Hybrid Finite-Discrete Element Modelling of Various Rock Fracture Modes during Three Conventional Bending Tests

The numerical techniques for modelling the rock fracture have been briefly reviewed. A hybrid finite-discrete element method (HFDEM) is proposed to simulate various fracture types of rock. A fracture model is implemented in the HFDEM for simulation of the three main fracture types. In addition, the influence of the strain rate is considered during the HFDEM modelling rock behavior. Then, two typical rock mechanism tests are employed to calibrate the HFDEM. The proposed method has well modelled the rock fracture processes and can obtain reasonable stress distribution and force–displacement curves. After that, the HFDEM is used to model three convention bending tests. The obtained rock fracture processes indicates that the HFDEM can simulate various fracture types. The obtained rock strengths and fracture toughness indicate that the HFDEM can reflect the influence of the strain rate. It is concluded that the HFDEM can model the entire and complete rock fracture process during the three convention bending tests, and it also can capture the rock’s behavior on the strain rate.

Experimental Study of the Rock Mechanism under Coupled High Temperatures and Dynamic Loads

With the development of modern society, geomaterials are widely used for infrastructure. These materials often experience dynamic loading and high temperature, which significantly influences the mechanical behaviour of the materials. This research focuses on the effects of the loading rate and high temperature on rock mass in terms of rock mechanism. A state-of-the-art review of rock mechanism under coupled dynamic loads and high temperatures is conducted first. The rock mechanism under static and dynamic loads is introduced. The marble is taken as the rock material for the test, while the split-Hopkinson pressure bar system is used to take the dynamic tests. In addition, the principles of the split-Hopkinson pressure bar are introduced to obtain the dynamic parameters. The fracture patterns of the uniaxial compressive strength test and the Brazilian tensile strength test are obtained and compared with those well documented in the literature. Some curves for the relationships among the loading rate, strain, temperature, compressive or tensile strengths are explained. It is conduced that with the increase of the loading rate, the rock strength increases, while with the increase of the temperature, the rock strength decreases.

Research on Simulation Process of Rock Broken by TBM Hob

The rock broken process was simulated by using finite element method based on the hob broken rock mechanism. The rock broken shape was analyzed by adjustment numbers of hobs and angles of hob. The destruction of rock was the presence of both compressive failure and shear failure. The main destruction of rock was compressive failure with single hob. The main destruction of rock was shear failure with multiple hobs. It could be found that the main destruction of hard and brittle rock was shear failure but shear failure of softer rock was relatively small through rock breaking process of three hob in different sequentially angles.

NAT-rock formation by mother clouds: a microphysical model study

Polar stratospheric clouds (PSCs) of type 1a or 1a-enh containing high number densities of nitric acid trihydrate (NAT) particles, can act as mother clouds for extremely large NAT particles, termed NAT-rocks, provided the air below the clouds is supersaturated with respect to NAT. Individual NAT particles at the cloud base fall into undepleted gas phase and rapidly accelerate due to a positive feedback between their growth and sedimentation. The resulting reduction in number density is further enhanced by the strong HNO3 depletion within a thin layer below the mother cloud, which delays subsequent particles. This paper introduces the basic microphysical principles behind this mother cloud/NAT-rock mechanism, which produces 10-4 cm-3 NAT-rocks with radii around 10 mm some kilometers below the mother cloud. The mechanism does not require selective nucleation and works even for a monodisperse particle size distribution in the mother cloud.

NAT-rock formation by mother clouds: a microphysical model study

Polar stratospheric clouds (PSCs) of type 1a or 1a-enh containing high number densities of nitric acid trihydrate (NAT) particles, can act as mother clouds for extremely large NAT particles, termed NAT-rocks, provided the air below the clouds is supersaturated with respect to NAT. Individual NAT particles at the cloud base fall into undepleted gas phase and rapidly accelerate due to a positive feedback between their growth and sedimentation. The resulting reduction in number density is further enhanced by the strong HNO3 depletion within a thin layer below the mother cloud, which delays subsequent particles. This paper introduces the basic microphysical principles behind this mother cloud/NAT-rock mechanism, which produces 10-4 cm-3 NAT-rocks with radii around 10mm some kilometers below the mother cloud. The mechanism requires neither selective nucleation nor additional atmospheric dilution and works even for a monodisperse particle size distribution in the mother cloud.