Current Issue : October-December Volume : 2021 Issue Number : 4 Articles : 5 Articles
To accurately obtain the tensile strength of rock and fully understand the evolution process of rock failure is one of the key issues to the research of rock mechanics theories and rock mass engineering applications. Using direct tensile, Brazilian splitting, and threepoint bending test methods, we performed indoor and numerical simulation experiments on marble, granite, and diabase and investigated the tensile strength and damage evolution process of several typical rocks in the three different tests. Our experiments demonstrate that (1) the strength is about 10% greater in the Brazilian splitting than in the direct tensile, while the tensile modulus is lower; it is the highest in the three-point bending, which is actually subjected to the bending moment and suggested as one of the indexes to evaluate the tensile strength of rock; (2) the strength in splitting tests is strikingly different, while the strain law is basically similar; the direct tensile test with precut slits is more attainable than that with no-cut slits, with an uninfluenced strength; (3) the failure modes of rocks using different methods are featured by different lithology, while their final modes are basically the same under the same method; (4) PFC and RFPA numerical simulation tests are effective to analyze the internal crack multiplication and acoustic emission changes in the rock as well as the damage evolution process of rock in different tests....
Dump in the steep area of the open-pit mine is essential for safe production. )e bedrock with the bumpy-surface blasting method effectively improves the stabilization of the dumpsite. )e effect of the ratio and dispersion degree on the deformation and failure of the dumping bench at the largely inclined area was analyzed. Based on the limit equilibrium method, the equation about the stability factor and the blasted region ratio was deduced. Virtual experiments were performed to address how the ratio and dispersion degree affect deformation and failure. )e results showed that the stability factor is a quadratic function of the ratio of the blasted area. )e increase in the ratio results in a drastic reduction of displacement, and the direction of displacement significantly changes. )e rise in the dispersion degree effectively reduces the displacement and shear strain increment, and the failure mode changes. )ere is a specific value for the ratio and dispersion degree, making the displacement and shear strain increment little. )e research on bumpy surface blasting in this paper provides the theoretical foundation for the dump construction at the site with the large dip angle....
Hazardous rock refers to an unstable rock block that is cut by weak structural planes and gradually separates from the slope. Hazardous rock generally collapses rapidly, and at present, it is challenging to effectively identify the separation degree of the rock and accurately predict its sudden failure. In this study, focusing on a hazardous rock with tilt behavior, a microelectromechanical system (MEMS) acceleration sensor is used in combination with the calculation principle of the included angle of the space vector to establish a microtilt angle monitoring method. A physical model test is designed, in which a thermally sensitive material (with heat-sensitive strength) is adopted as the weak structural plane of the hazardous block, and the change in the tilt angle during the process of block instability is monitored at a sampling frequency of 1000 Hz. -e test results show that the accelerated evolution of the tilt angle is a precursor to hazardous rock failure. In the rapid acceleration stage, the reciprocal of the tilt angle rate is approximately linear with time, and a correlation equation is obtained. Assuming that the change rate of the tilt angle is approximately infinite, the failure time of hazardous rock can be predicted using the correlation equation. In addition, the effectiveness of the instability prediction method based on microtilt angle monitoring is verified by analyzing the long-term monitoring data of hazardous rock....
The 2030 Agenda and Sustainable Development Goals (SDG) are both an engineering challenge and an opportunity. Clean energy (SDG 7), sustainable cities and communities (SDG 11), and climate action (SDG 13) represent an effort to manage, plan, and develop our buildings and infrastructure. The purpose of this study is to contribute to this challenge by analysing nanomaterials in marine environment structures, both urban and maritime. To do this, we have analyzed different regulations of concrete properties in various countries, defining the characteristics of the cement, coating, water/cement rating, and chloride effect; the difference in durability based on conventional reinforcements and nanomaterials; and use on highly sensitive elements, buildings in marine environments, rubble mound structures, crown walls, and gravity-based foundations for wind power facilities. Division into overhead, underwater, or splash zones entails the use of epoxy resins or silica fume matrices in percentages far below ten percent. Using the most exposed and unfavorable structures, conclusions of application to buildings are established based on the recommendations in maritime engineering most exposed to the actions of the waves. The study concludes with recommendations regarding the durability, increased lifespan, and use of new materials in infrastructure elements in highly adverse marine environments....
*e development law of mining cracks in shallow coal seams under gully topography was used as the research base to analyze the development characteristics of mining cracks in the 5-2 coal mining face of Anshan Coal Mine, and the weak strength was established. *e basic top force model under the action of the overburden is the “nonuniformly distributed load beam” structure model. *rough similar simulation research and theoretical calculation analysis, the fracture development law of the working face passing through the valley is studied. Based on the mechanical analysis of the beam structure with nonuniform load, the discriminant conditions of the stability of the bearing structure of the bedrock are derived, the calculation formulas of the parameters such as the pressure, shear force, and the ultimate span of the basic roof at both ends are determined, the influence law of the thickness and slope change of the weak strength overburden on the mining crack spacing is revealed, and the influence of the slope of the weak strength overburden on the weighting step distance on the beam with nonuniform load is obtained. *e phenomenon is that the burial depth has a great influence on the step distance of weighting. *e practice shows that the distance between the mining-induced fractures determined by the nonuniformly distributed load beam model and the periodic weighting step, the height of fracture development, and the buried depth are approximately the same; the mining-induced fractures in the overburden develop and evolve periodically with the failure and instability of the bedrock. *e research results will clarify the development mechanism of surface cracks in the gully mining area, which is of great significance to reduce terrain disasters....
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