To explore the influence of coal thickness on mechanical behavior and failure characteristics rock-coal-rock (RCR) mass, experimental investigation uniaxial compressive tests was conducted first then a systematic numerical simulation by particle flow code (PFC2D) performed to deeply analyze RCR specimens with different thicknesses in conventional compression tests. The overall elastic modulus peak stress lie between rock coal. Inter-particle properties were calibrated match physical sample...

Abstract Layered rocks exhibit notable transverse isotropy and have a significant impact on the deformation failure characteristics of underground structures. To large extent, mechanical properties layered are related to structure stress state their bedding planes. obtain an in‐depth understanding yield rocks, model for incorporating planes weakness volumetric is proposed by improving strain‐hardening/softening ubiquitous‐joint based continuum mechanics methods. In this model, elastoplastic...

The mechanical properties of mortar materials in construction are influenced both by their own proportions and external loads. trend the stress–strain curve cracks compaction stage has great influence on relationship between strength deformation cement mortar. Uniaxial compression tests specimens with different cement–sand ratios loading rates were carried out, stored dissipated energies calculated. Results indicated that elastic modulus increase ratio rate. energy dissipation shows good...

The development of cost-effective oxygen reduction reaction (ORR) catalysts is great importance and urgency for green energy technologies. Herein, the uniform Co nanoparticles encapsulated in two-dimensional (2D) nitrogen-doped graphitic-carbon nanosheets (Co@N–C) were synthesized by a one-step solvent-free, template-free, scalable pyrolysis strategy. Originating from mutually reinforcing effect between N–C active sites stable 2D porous conductive nanosheet structure, optimized Co@N–C-700...

There are a lot of fissures, holes, and other defects in the formation natural rocks. Under influence external loads, these may cause engineering problems. Therefore, it is great significance to analyze characteristics damage evolution defective In study, double‐hole rocks with different angles center connection line considered numerical models established firstly. Then mechanical behavior acoustic emission (AE) analyzed systematically. Finally laws rock materials investigated based on AE...

Basic rock mechanical parameters, that is, the uniaxial compressive strength σ c and elastic modulus E, have close relationships with fractal dimension inhomogeneity. Scanning electronic microscopy calculations are applied to four different types (mudstone, sandstone, limestone, basalt) in order investigate between properties, dimensions, homogeneity. The results show of each type fluctuates as scanning magnification increases. Rocks values possess self-similarity when or increases,...

In order to evaluate the surrounding rock stability of deep roadways, diversity accident hazard sources in coal mining is statistically analyzed. To conduct an effective evaluation, first, risk analysis factors affecting mass accidents carried out, and comprehensive safety index system mine roadway established. Further, combining theory with extension method, a matter-element model for assessment Finally, E-Zhuang Xinwen Ming area are evaluated. The results show that grade roadways "B",...

Many case studies have revealed that rock bursts generally occur in the high stress concentration area where layer‐crack structures often exist, especially for brittle coal or masses. Understanding mechanical properties of models is beneficial rational design and stability analysis engineering project burst prevention. This study experimentally investigated influence fissure number on through uniaxial compression tests. The digital speckle correlation method (DSCM) acoustic emission (AE)...

Abstract SEM scanning and fractal dimension estimation were adopted to study the inhomogeneous microstructure features its influences on failure pattern of sandstone. The results show that different sandstones are self-similarities microstructure. average homogeneities lithic arenite, greywacke, subfeldspathic arenite 5.61, 3.39, 4.57 estimated dimensions 1.94, 1.52, 1.84, respectively, indicating homogeneity is well consistent with dimension. resulted macro-cracks vertical cleavages,...

In order to evaluate the stability of deep surrounding rock, all affecting factors should be theoretically identified. However, some have slight impacts on rock compared with others. To conduct an effective risk assessment, key first extracted. The analytic hierarchy process (AHP) and grey relation analysis (GRA) methods are integrated determine factors. First, AHP method is applied sort by calculating weights them. Seven out fifteen extracted as factors, which account for 80% weights....

In order to identify the microstructure inhomogeneity influence on rock mechanical property, SEM scanning test and fractal dimension estimation were adopted. The investigations showed that self-similarity of markedly changes with scanned microscale. Different rocks behave in different variation patterns magnification, so it is conditional adopt describe material. Grey diabase black have high suitability; red sandstone has low suitability. suitability fractal-dimension-describing method for...

Natural rock masses have many internal joints, fractures and faults, which greatly influence their mechanical properties during geological processes. In this paper, considering different joint angles rock-bridge angles, uniaxial compression numerical tests on double-fractured red sandstone based particle flow code (PFC) were carried out. The laws of the mechanics, acoustic emission (AE) damage evolution characteristics under crack geometry conditions analysed. results indicated that peak...

Geotechnical engineering problems will cause asymmetric deformation of surrounding rock, which is not conducive to the stability rock mass. In order study meso-damage mechanism strength and characteristics, taking three kinds typical sandstone as examples, meso structure images were obtained by JSM-6510LV scanning electron microscope (SEM). According meso-structure fractal theory, MATLAB was compiled calculate dimension types sandstone. The uniaxial compression test carried out using...

Taking Wuzhen Xishan scenic area as an example, this article aimed at studying the impact internet comments had on tourists' decision-making. Based tourism decision-making reference group theory and behavior theory, using experimental method, author designed a pretest questionnaire post-test respectively to get know changes in relative decisions before after reading comments. Through comparative analysis, we find that great decision. And main factors include category of comments, style...

The family physicians contracted service is an important means to promote hierarchical diagnosis and treatment realize healthy Chinese strategy.With the continuous introduction of policy, it very raise awareness, effectively put into place.This study analyzed policy from perspective public used multiple streams theory framework analyze driving factors proposed.In addition, explored influence problem stream, political stream on launch process.These efforts can help improvement awareness in...

By using the image processing and numerical functions of MATLAB, after treatment SEM to mudstone specimen with threshold segmentation, filtering other procedures, we can obtain binary mudstone; determine fractal dimension by MATLAB program.The results showed that: is simple convenient, computation regular Koch curve that calculating in this way are accurate reliable.The calculation has different under intensities.On whole, bigger intensity, smaller dimension.

Objective To analyze influencing factors of physicians' turnover intention at public county hospitals from career stage perspective.Methods Physicians life was divided into three stages according to professional ranks and titles.The sample drawn using stratified multistage random methods in Shandong province 677 questionnaires were completed,giving a 90.3％ valid response rate.Data analyzed multi-group stepwise linear regression.Results The percentage responders with middle high-level...