强动载荷连续多次冲击加载下的煤岩体力学特性研究

发布时间：2018-06-18 19:04

本文选题：冲击地压 + 煤岩　；参考：《安徽理工大学》2017年硕士论文

【摘要】：冲击地压往往伴随着多次冲击现象,单次冲击与多次冲击的力学特性必然存在差异,而煤岩体作为冲击地压的受体,很有必要对其进行多次冲击力学特性的研究。该文以煤岩体为研究对象,从多次冲击设备的优选、煤岩体二次冲击实验及冲击地压多次冲击的工程模拟进行了相关研究。设计了两种SHPB连续多次冲击加载系统,即前后子弹加载系统和内外子弹加载系统,推导了变截面撞击的SHPB相关校验公式,得到了较好的波形校验结果。最终从实验可行性与成本、加工难度等方面选择了内外子弹加载系统进行实验工作,为了对比,并做了静态加载实验、单次冲击加载实验,且选择了两种规格的煤样做了低应变率与高应变率两种类型的实验,实验结果表明,单次冲击时,低应变率下,强度具有应变率硬化效应,高应变率下,强度随应变率大致保持不变;二次冲击时,低应变率时,强度会在第二次冲击时增强,高应变率时,强度会在第二次冲击时削弱至无,这与单次冲击的力学特性具有较大差异。同时,基于ABAQUS,对煤岩体的二次冲击进行了数值模拟,其所得应力应变曲线变化规律与实验大致保持一致,验证了 SHPB对煤岩体的二次冲击实验的可靠性。基于已与实验得到校验的SHPB多次冲击的煤岩摩尔库伦模型的数值模拟,建立了多次冲击"岩-煤-岩结构"数值模拟,进行了低强度与高强度一次、二次与四次冲击模拟。由模拟结果可知:在低强度冲击时,冲量相同的情况下,随着冲击次数的增多,"岩-煤-岩结构"中煤体的损伤不断变大;在高强度冲击时,冲量相同的情况下,随着冲击次数的增多,"岩-煤-岩结构"中煤体的损伤大致相当。从应力时程角度来看,在低强度时,应力时程曲线出现了二次强度增加的现象,在高强度时,应力时程曲线出现了二次强度减小的现象,这与SHPB二次冲击实验结果相符,以此,通过实验和数值模拟双重方式验证了结论的正确性。
[Abstract]:The impact ground pressure is often accompanied by multiple impact phenomena, and the mechanical properties of single impact and multiple impact are bound to be different. As the receptor of impact ground pressure, it is necessary to study the multiple impact characteristics of coal and rock mass. Taking coal and rock mass as the research object, this paper studies the optimization of multiple impact equipment, the secondary impact test of coal and rock mass, and the engineering simulation of multiple impact on ground pressure. Two kinds of SHPB continuous multiple impact loading systems are designed, that is, the front and rear bullet loading systems and the internal and external bullet loading systems. The correlation checking formulas of SHPB with variable cross section impact are derived, and good waveform verification results are obtained. Finally, from the aspects of feasibility and cost of experiment, processing difficulty and so on, the internal and external bullet loading system is selected for experimental work. In order to compare, static loading experiment and single impact loading experiment are done. Two kinds of coal samples with low strain rate and high strain rate are selected. The experimental results show that the strength has strain rate hardening effect at low strain rate, and strain rate hardening effect at high strain rate. At the second impact, the strength increases at the second impact, and at the high strain rate, the strength decreases to zero at the second impact, which is different from the mechanical properties of the single impact. At the same time, based on Abaqus, the numerical simulation of secondary impact of coal and rock mass is carried out, and the variation law of stress-strain curve obtained is approximately consistent with the experiment, which verifies the reliability of SHPB's secondary impact test on coal and rock mass. Based on the numerical simulation of the Mohr Coulomb model of coal and rock which has been verified by SHPB, the numerical simulation of "rock-coal-rock structure" has been established, and the low strength and high strength primary, secondary and fourth impact simulation have been carried out. The simulation results show that the damage of coal body in "rock-coal-rock structure" increases with the increase of impact times when the impulse is the same when the impact is low, and when the impact is high, when the impulse is the same, the damage of coal body in "rock-coal-rock structure" becomes more and more serious. With the increase of impact times, the damage of coal body in rock-coal-rock structure is about the same. From the point of view of stress time history, the secondary strength increases in the stress history curve at low strength, and the quadratic strength decreases in the stress history curve at high strength, which is consistent with the results of SHPB secondary impact test. The correctness of the conclusion is verified by both experiment and numerical simulation.
【学位授予单位】：安徽理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TD324

【相似文献】