[신간의 별자리x] 우리/미술, 그리고 ‘슬픔의 박물관’

• Stability of steady frictional sliding, inertia and the quasi-static limit • work on ps 4; see course web site

The Mechanics Of Earthquakes And Faulting

Cracking processes have been extensively studied in brittle rock and rock-like materials. Due to the experimental limitations and the complexity of rock texture, details of the cracking processes could not always be observed and assessed comprehensively. To contribute to this field of research, a numerical approach based on the particle element model was used in present study. It would give us insights into what is happening to crack initiation, propagation and coalescence. Parallel bond model, a type of bonded-particle model, was used to numerically simulate the cracking process in rock-like material containing a single flaw under uniaxial vertical compression. The single flaw’s inclinations varied from 0° to 75° measured from the horizontal. As the uniaxial compression load was increased, multiple new microcracks initiated in the rock, which later propagated and eventually coalesced into longer macrocracks. The inclination of the pre-existing flaw was found to have a strong influence on the crack initiation and propagation patterns. The simulations replicated most of the phenomena observed in the physical experiments, such as the type, the initiation location and the initiate angle of the first cracks, as well as the development of hair-line cracks, which later evolved to macrocracks. Analyses of the parallel bond forces and displacement fields revealed some important mechanisms of the cracking processes. The first cracks typically initiated from the tensile stress concentration regions, in which the tensile stress was partially released after their initiation. The tensile stress concentration regions subsequently shifted outwards close to the propagating tips of the first cracks. The initiation and propagation of the first cracks would not significantly influence the compressive stress singularity at the flaw tips, which was the driving force of the initiation of secondary cracks. The initiation of microcracking zone consisting almost exclusively of micro-tensile cracks, and that of microcracking zone consisting of micro-tensile cracks and mixed micro-tensile and shear cracks, were found to be correlated with two distinct types of displacement fields, namely type I (DF_I) and type II (DF_II), respectively.

Cracking Processes in Rock-Like Material Containing a Single Flaw Under Uniaxial Compression: A Numerical Study Based on Parallel Bonded-Particle Model Approach

An experimental investigation on thermal damage and failure mechanical behavior of granite after exposure to different high temperature treatments

The goal of this review paper is to provide a summary of selected discrete element and hybrid finite–discrete element modeling techniques that have emerged in the field of rock mechanics as simulation tools for fracturing processes in rocks and rock masses. The fundamental principles of each computer code are illustrated with particular emphasis on the approach specifically adopted to simulate fracture nucleation and propagation and to account for the presence of rock mass discontinuities. This description is accompanied by a brief review of application studies focusing on laboratory-scale models of rock failure processes and on the simulation of damage development around underground excavations.

https://cyberleninka.org/article/n/14358.pdf

A review of discrete modeling techniques for fracturing processes in discontinuous rock masses

In the process of excavating seven parallel tunnels at the Jinping II Hydropower Station, several extremely intense rockbursts occurred, killing and injuring construction workers and damaging several sets of equipment. Based on the characteristics and mechanisms of these rockbursts, four typical events were selected and their temporal and spatial characteristics were here described in detail. The geological conditions revealed after the rockbursts were surveyed carefully. The responses of support elements were also analyzed. The details documented in each case provide not only an important reference for understanding the development mechanisms of rockbursts but also a basis for the selection and development of rockburst prevention measures in deep hard rock tunnels.

Case Histories of Four Extremely Intense Rockbursts in Deep Tunnels

In situ monitoring of rockburst nucleation and evolution in the deeply buried tunnels of Jinping II hydropower station

Real-time computerized tomography (CT) experiments on sandstone damage evolution during triaxial compression with chemical corrosion

Many geo-engineering applications, such as geological repositories for nuclear waste, geological sequestration of CO2, enhanced geothermal systems, deep mining and deep well drilling involve thermal, hydraulic, mechanical and chemical interactions. Describing these coupling processes requires knowledge of each individual process and their coupling effects (Kohl et al. 1995; Hudson et al. 2005; Poulet et al. 2012; Jobmann and Polster 2007). A number of investigations (Maruyama et al. 2014; Zhu et al. 2015; Duchkov et al. 2014; Nagaraju and Roy 2014; Fortin et al. 2011) on various rock materials have indicated that the elastic modulus, strength, thermal conductivity and seismic properties of rock materials are dependent on their porosity, saturation degree, saturating fluids and damage. Furthermore, there are correlations between the physical and mechanical properties, and some theoretical and empirical relations have been proposed for different rocks (Yasar and Erdogan 2004; Gruescu et al. 2007; Hovis et al. 2008; Chen et al. 2012). Anisotropies are usually observed in rock materials and cause the physical and mechanical properties to vary with direction because of the presence of bedding planes, schistosity planes, structural discontinuities and stress-induced defects (Gao et al. 2015; Davis et al. 2007; Bourret et al. 2015; Qin et al. 2015; Wenk et al. 2012). Some previous studies indicated that thermal expansion of rock materials exhibits anisotropies (Mitoff and Pask 1956; Robertson 1988; Somerton 1992). Indeed, the thermal expansion of rock materials is relatively small in magnitude and may have only minor effects (Robertson 1988). However, the thermal expansion coefficients of rock materials usually vary with their mineral compositions, and these differences in thermal expansion behaviour may have significant effects on the structure of rock masses. For example, anisotropy in the thermal expansion caused by bedding planes in sedimentary rocks can also cause structural damage during heating (Somerton 1992). The aim of the present paper is to study the anisotropic mechanical properties, thermal expansion properties and & Dawei Hu dwhu@whrsm.ac.cn

Anisotropies in Mechanical Behaviour, Thermal Expansion and P-Wave Velocity of Sandstone with Bedding Planes

Brittleness is an important characteristic of rocks, for it has a strong influence on the failure process no matter from perspective of facilitating rock breakage or controlling rock failure when rocks are being loaded. Various brittleness criteria have been proposed to describe rock brittleness. In this paper, the existing brittle indices are summarised and then analysed in terms of their applicability to describe rock brittleness. The analysis demonstrates that the widely used strength ratio or product (σ
 c/σ
 t, σ
 c·σ
 t) of rocks cannot describe rock brittleness properly and that most of the indices neglect the impact of the rock’s stress state on its brittleness. A new evaluation method that includes the degree of brittleness (B
 d) and brittle failure intensity (B
 f) is proposed based on the magnitude and velocity of the post-peak stress drop, which can be easily obtained from the conventional uniaxial and triaxial compression tests. The two indices can accurately account for the influence of the confining pressure on brittleness, and the applicability of the new evaluation method is verified by different experiments. The relationship between B
 d and B
 f is also discussed.

Hui Zhou

Papers

Case Histories of Four Extremely Intense Rockbursts in Deep Tunnels

In situ monitoring of rockburst nucleation and evolution in the deeply buried tunnels of Jinping II hydropower station

Real-time computerized tomography (CT) experiments on sandstone damage evolution during triaxial compression with chemical corrosion

Anisotropies in Mechanical Behaviour, Thermal Expansion and P-Wave Velocity of Sandstone with Bedding Planes

Evaluation Methodology of Brittleness of Rock Based on Post-Peak Stress–Strain Curves