干燥_饱和风化花岗岩动态力学特性及损伤演化规律研究

发布时间：2018-12-07 07:57

【摘要】：本文以国家基金为依托,针对离子型稀土矿溶浸效率低的的特点,提出采用小药量空间间隔爆破提高渗透的想法,以此为依据利用霍普金森杆(SHPB)试验装置和核磁共振仪等仪器,研究干燥、饱和状态下离子型稀土风化花岗岩的动态力学特性及其动态损伤,通过本文研究为提高离子型稀土矿开采提供一定的理论和技术支持。本文主要内容和研究结果如下:(1)通过核磁共振反演软件获得试样的弛豫时间T2分布以及内部孔隙结构信息,结果表明试样的T2谱分布曲线有效信号在0.02ms~10000ms之间,各试样中的孔隙主要为小孔隙和中等孔隙,两者谱峰面积占总谱面积的98%以上。(2)采用RMT-150C试验系统进行单轴压缩试验和巴西劈裂试验,为后续章节提供参考,基于试验结果,分析风化花岗岩在干燥、饱和状态下应力应变曲线变化规律以及强度变形特性的影响,结果显示饱和试样表现出软化特性,不同含水状态的试样抗压强度、抗拉强度和弹性模量均随孔隙度的增大而减小,受试样内部节理面形状和分布的影响,孔隙度不同的两个试样所对应的抗压强度和弹性模量差值变化较大,离散性明显。(3)利用SHPB试验装置进行循环冲击试验,对干燥、饱和风化花岗岩动态强度及变形特性进行研究研究,结果表明试样动态应变随着冲击次数,孔隙度的增加而增大,与是否含水无关;随着冲击次数增加试样弹性模量变化曲线呈两种变化:逐步减小和先增大后减小,其中如果饱水试样抗冲击能力足够强,当冲击次数足够多时,弹性模量最终趋于稳定;弹性模量随着孔隙度的增大而减小,饱水试样弹性模量比干燥试样下降更快;试样峰值应力整体随着冲击次数的增大呈现先增大再减小,与含水状态无关;试样峰值应力整体随孔隙度增大而减小,同时峰值应力存在一临界值,当孔隙度小于这个值时,峰值应力整体下降,当大于此孔隙度时,峰值应力趋于变化趋于平缓,而且饱水试样对应的这个临界值大于干燥试样;试样平均应变率随着冲击次数的增大而增大,与含水状态无关;饱水试样以孔隙度4%为界,干燥试样以3.25%为界,在临界值后的平均应变率整体大于界限前的平均应变率。(4)通过冲击前后试样对应的纵波波速,从宏观方面研究干燥、饱和状态下风化花岗岩试样的动态损伤变化规律,并从核磁共振T2谱分布、T2谱面积和核磁共振成像等微观角度分析冲击前后干燥、饱和两种状态下试样的孔隙变化,分析得到干燥试样孔隙变化大于饱和试样,表明当风化花岗岩试样饱水时,其动态累积损伤要小于干燥试样,从侧面反映出在动荷载作用下,达到同样的损伤量,饱和试样需要消耗更多能量。
[Abstract]:In this paper, based on the national fund, in view of the low leaching efficiency of ion rare earth ore, the idea of increasing permeability by small charge space interval blasting is put forward. Based on this, the dynamic mechanical properties and dynamic damage of ion-type rare earth weathered granite under dry and saturated condition were studied by using Hopkinson rod (SHPB) test device and nuclear magnetic resonance instrument. The research in this paper provides some theoretical and technical support for the improvement of ion rare earth mining. The main contents and results are as follows: (1) the relaxation time T2 distribution and internal pore structure information of samples are obtained by NMR inversion software. The results show that the effective signal of T2 spectrum distribution curve is between 0.02ms~10000ms. The porosity of each sample is mainly small pore and medium pore, and the peak area of both is more than 98% of the total spectrum area. (2) uniaxial compression test and Brazilian splitting test are carried out with RMT-150C test system, which provides a reference for the following chapters. Based on the experimental results, the variation of stress-strain curves and the strength and deformation characteristics of weathered granite under dry and saturated conditions are analyzed. The results show that the saturated samples show softening characteristics, and the compressive strength of the samples with different water content is different. The tensile strength and elastic modulus decrease with the increase of porosity, and the difference between compressive strength and elastic modulus of the two specimens with different porosity varies greatly due to the shape and distribution of the joints inside the specimen. (3) the dynamic strength and deformation characteristics of dry and saturated weathered granite were studied by cyclic impact test with SHPB device. The results showed that the dynamic strain of the sample increased with the impact times. The increase of porosity has nothing to do with water content. With the increase of impact times, the change curve of elastic modulus shows two kinds of changes: gradually decreasing and then decreasing. If the saturated sample is strong enough to resist the impact, when the number of impact is enough, the elastic modulus will eventually become stable; The modulus of elasticity decreases with the increase of porosity, the elastic modulus of saturated sample decreases faster than that of dry sample, and the whole peak stress of the sample increases first and then decreases with the increase of impact times, which has nothing to do with the state of water content. The peak stress of the sample decreases with the increase of porosity, and there is a critical value of the peak stress. When the porosity is less than this value, the peak stress decreases as a whole, and when the porosity is greater than the porosity, the peak stress tends to change slowly. The critical value of saturated sample is larger than that of dry sample. The average strain rate increases with the increase of impact times, and is independent of the water content. The average strain rate after the critical value is larger than the average strain rate before and after the critical value. (4) the longitudinal wave velocity corresponding to the specimen before and after impact. The dynamic damage changes of weathered granite samples under the condition of drying and saturation are studied from macroscopic angle, and the drying before and after impact is analyzed from the microcosmic angles of NMR T2 spectrum distribution, T2 spectrum area and NMR imaging, etc. The pore changes of the samples under saturated condition are analyzed. The pore changes of dry samples are larger than that of saturated samples, which indicates that the dynamic cumulative damage of weathered granite samples is smaller than that of dry samples when the samples are saturated with water, which is reflected from the side under dynamic load. To achieve the same amount of damage, saturated samples need to consume more energy.
【学位授予单位】：江西理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TD313

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