A comparative study of progressive failure of granite and marble rock bridges under direct shearing.

Shear failure of rock bridges is an important process in geological phenomena, including landslides and earthquakes. However, the progressive failure of natural rock bridges has not yet been fully understood. In this work, we carried out direct shearing experiments on both granite and marble rock bridges, and applied acoustic emission (AE) monitoring throughout the experiments.

Research Progress on the Geomechanical Properties of Block-in-Matrix Rocks.

The differences in geomechanical properties and the uncertainty in the spatial distribution of Bimrock pose significant challenges to the construction and disaster prediction of geotechnical engineering. To clarify the geomechanical characteristics of Bimrock, this paper summarizes the basic concepts and classification methods of Bimrock at home and abroad. It discusses the methods and characteristics of determining the geometric features of Bimrock blocks and explores the influencing factors and laws of failure modes and strength under different stress states of Bimrock.

Influence of the Welding Degree on the Strength and Failure Modes of Tuff.

The diagenesis of welded tuffs is a process in which volcanic debris undergoes degassing, compaction, and quenching, and vitreous rheologic, which indicates that the welding occurred in a high-temperature, high-pressure diagenetic environment and that different temperatures and pressures result in different degrees of welding in the welded tuffs, which can also result in differences in the mechanical properties of the rock. In this study, based on petrographic identification, mineral composition analysis, and pore structure characterization, uniaxial compression combined with linear accelerator CT and Brazilian splitting tests was carried out to investigate the influence of the welding degree on the strength and failure modes. The test results showed that although they had almost similar mineral composition and porosity, the uniaxial compression strength and tensile strength of the strongly welded tuffs were greater than that of the weakly welded tuffs.

The Confinement-Affected Strength Variety of Anisotropic Rock Mass.

It has been recognized that the anisotropic structures dominate the deformation and strength properties of laminated rock masses. The resultant strength anisotropy is strongly affected by confining pressures beyond anisotropic structures. Nevertheless, the effects of confinement are inconsistent among existing experiments and not fully understood.

The effects of missense OPN3 mutations in melanocytic lesions on protein structure and light-sensitive function.

Opsin 3 (OPN3), a member of the light-sensitive, retinal-dependent opsin family, is widely expressed in a variety of human tissues and plays a multitude of light-dependent and light-independent roles. We recently identified five missense variants of OPN3, including p. I51T, p.

Experimental investigation of the creep behaviour of remoulded loess under different levels of compactness.

Generally, a loess high fill project will undergo a time-dependent deformation and settlement process for a long time after the initial fill. Understanding the creeping behaviour of compacted loess is an important part of determining the stability of a compacted loess foundation. To study the creep behaviour of remoulded loess under different levels of compactness, we performed triaxial shear and triaxial creep tests using Q2 loess specimens obtained from the new district of Yan'an city.

Report on the 18th International Symposium on Geo-disaster Reduction and the 4th Gu Dezhen Lecture, 20-22 November 2020, Beijing, China.

The 18th International Symposium on Geo-disaster Reduction (ISGdR) was held on 20-22 November in Beijing, China, focusing on the theme of "Improving the Relationship between Geoenvironment and Society". In this symposium, a high-level Gu Dezhen Lecture and a number of keynote and invited lectures provided a platform for scientists, industrial professionals and students to share their researches and exchange novel ideas on geo-disaster reduction in a hybrid way of offline and online.

Compression-Induced Tensile Mechanical Behaviors of the Crystalline Rock under Dynamic Loads.

Characterization of the tensile mechanical behaviors of rocks under dynamic loads is of great significance for the practical engineering. However, thus far, its micromechanics have rarely been studied. This paper micromechanically investigated the compression-induced tensile mechanical behaviors of the crystalline rock using the grain-based model (GBM) by universal distinct element code (UDEC).

A New Shear Strength Criterion for Rock Masses with Non-Persistent Discontinuities Considering the Nonlinear Progressive Failure Process.

The shear strength characteristics of rock masses containing non-persistent discontinuities are strongly affected by discontinuities and rock bridges. The linear Jennings criterion cannot reflect the nonlinear mechanical behavior during progressive failure of rock masses with non-persistent discontinuities. In this study, a new nonlinear shear strength criterion was developed.

Progressive Failure Characteristics of Brittle Rock under High-Strain-Rate Compression Using the Bonded Particle Model.

This paper microscopically investigated progressive failure characteristics of brittle rock under high-strain-rate compression using the bonded particle model (BPM). We considered the intact sample and the flawed sample loaded by split Hopkinson pressure bar respectively. Results showed that the progressive failure characteristics of the brittle rock highly depended on the strain rate.

Three-dimensional pore characterization of intact loess and compacted loess with micron scale computed tomography and mercury intrusion porosimetry.

The pore structure is one of the most important properties of soil, which can directly affect the other properties such as water content, permeability and strength. It is of great significance to study the soil pore structure for agricultural cultivation, water and soil conservation and engineering construction. This paper investigates the 3D pore characterization of intact loess and four kinds of compacted loess (with different dry density) in northwest China.

Numerical Studies on the Failure Process of Heterogeneous Brittle Rocks or Rock-Like Materials under Uniaxial Compression.

In rocks or rock-like materials, the constituents, e.g. quartz, calcite and biotite, as well as the microdefects have considerably different mechanical properties that make such materials heterogeneous at different degrees.

Numerical Simulation on Seismic Response of the Filled Joint under High Amplitude Stress Waves Using Finite-Discrete Element Method (FDEM).

This paper numerically investigates the seismic response of the filled joint under high amplitude stress waves using the combined finite-discrete element method (FDEM). A thin layer of independent polygonal particles are used to simulate the joint fillings. Each particle is meshed using the Delaunay triangulation scheme and can be crushed when the load exceeds its strength.

[Monte Carlo simulation of the divergent beam propagation in a semi-infinite bio-tissue].

In order to study the light propagation in biological tissue, we analyzed the divergent beam propagation in turbid medium. We set up a Monte Carlo simulation model for simulating the divergent beam propagation in a semi-infinite bio-tissue. Using this model, we studied the absorbed photon density with different tissue parameters in the case of a divergent beam injecting the tissue.

[Mechanism of "crescent sign" formation in avascular necrosis of femoral head].

Objective: To investigate corresponding relation between structure change of the femoral head with "crescent sign" and stress exerted on the avascular necrosis of femoral head, to explore the mechanism of the "crescent sign" formation.

Methods: From March 1998 to April 2003, the femoral heads of 18 hips in 16 cases having osteonecrosis and "crescent sign" in X-ray film before total hip arthroplasty, were collected. General and coronal section plane morphology of the femoral heads were observed.

[Measurements of diffusion reflectance and transmittance of biological tissues by using CCD].

The CCD experimental setup and the CCD image analysis system that were developed by using C Language were presented, and the spatially resolved diffusion reflectance and transmittance of porcine muscle and fat were determined by using CCD experimental setup. The experimental results were compared with those of Monte Carlo simulations and those of the two models based on diffusion theory, and we found good agreement between theory and experiment for the range from the beam center to 12 mm. It i s shown that the CCD experimental setup and the CCD image analysis system can be used to measure the spatially resolved diffusion reflectance and transmittance of biological tissues, and this work offers the experimental bases for noninvasive and fast measurement of optical parameters of biological tissues.

Analysis of capillary interferometry for measuring refractive indices of minute samples.

A method of measuring the refractive indices of minute samples by analyzing capillary interferometry is introduced. With the interference theory of light, the intensity distribution of an interference fringe pattern formed by a cylindrical tube of a capillary is obtained, and the influence of some parameters on the fringes are discussed. The measurement accuracy and its relative problems are analyzed.