脆性材料钻孔爆炸致裂机理研究
发布时间：2019-04-25 22:55
【摘要】：爆破方法具有高效率、低成本等特点,因而在矿山、土木和油气等工程中得到了广泛的应用,因此研究爆破特别是钻孔爆破致裂机理具有很重要的理论意义和应用价值。本文主要研究脆性材料(岩石和混凝土)在爆炸冲击载荷作用下的开裂行为,通过理论分析、数值模拟和实验研究对钻孔爆炸致裂问题进行了较系统的研究,主要内容包括以下几个方面： 钻孔装药爆炸后在距爆源不同的距离会产生破碎区、开裂区和弹性区,根据这三种不同的材料响应行为建立了一种空穴膨胀理论模型,该模型与以前的空穴膨胀模型相比,不同点是空腔初始半径不为0,而是一个有限值。同时在模型中考虑了剪胀效应,这样一来在破碎区内不仅可以描述脆性材料的压缩状态,也可以描述材料的膨胀状态。文中还将理论计算结果与利用实验室自己开发的材料本构模型进行的数值模拟结果进行了比较,发现这两种方法计算得出的空穴壁面处的径向应力大小比较一致。而且通过空穴膨胀模型还可以得出使空穴发生膨胀行为的临界径向应力。 建立了二级钻地弹的侵彻分析模型,研究了靶体中预制孔道直径大小与弹体侵彻深度之间的关系,并与实验结果进行对比,发现两者吻合得很好；优化了二级战斗部系统,并得到了最优侵彻深度与撞击速度、随进弹与前置装药直径之比之间的关系。 数值模拟分析了载荷特性如载荷峰值、加载率和卸载率对钻孔周围破碎区和开裂区范围大小产生的影响。研究发现如果载荷峰值过高会在钻孔周围形成较大范围的破碎区,造成载荷能量的浪费,对宏观连贯性裂纹的扩展延伸没有产生积极的作用；如果载荷峰值过低,钻孔周围介质中的环向应力不足以引起径向裂纹的产生,不利于宏观裂纹的生成。研究还发现在相同冲量的条件下,梯形载荷比三角形载荷的致裂效果好一些,并且载荷的加载率和卸载率对裂纹的数目和长度有很大的影响,加载率越高同时卸载率越低,产生的宏观裂纹越长,但是裂纹数目越少。当使空穴发生膨胀行为的临界径向应力作为载荷峰值的下界时,能够产生较好的致裂效果。 利用实验室自己开发的脆性材料本构模型对花岗岩钻孔爆炸致裂问题进行了数值模拟研究,并与文献中报导的实验结果和实验室自己的实验结果进行了比较。结果表明该本构模型能够较好地模拟脆性材料(岩石、混凝土)在动态冲击载荷下的损伤开裂行为。 采用数值模拟方法研究了裂纹内爆生气体驱使裂纹扩展的过程,并对裂纹内高压气体的分布、裂纹不同位置的张开位移进行了分析,研究发现：裂纹密度越大,驱使裂纹扩展所需要的临界压力也越高；高压气体浸入裂纹内并在孔内膨胀做功的联合作用与只考虑高压气体浸入裂纹内的单独作用相比,前者的致裂效果稍好一些。
[Abstract]:Because of its high efficiency and low cost, blasting method has been widely used in mining, civil engineering, oil and gas engineering, etc. Therefore, it is of great theoretical significance and application value to study the mechanism of blasting, especially in drilling blasting. In this paper, the cracking behavior of brittle materials (rock and concrete) under explosive impact load is studied. Through theoretical analysis, numerical simulation and experimental study, the problem of borehole explosion cracking is studied systematically. The main contents include the following aspects: a hole expansion theoretical model is established according to the response behavior of the three different materials, such as the fragmentation zone, the crack zone and the elastic zone, which will occur at different distances from the explosion source after the drilling charge explodes, and the theoretical model of hole expansion is established according to the response behavior of these three kinds of materials. The difference between the model and the previous cavity expansion model is that the initial radius of the cavity is not 0 but a finite value. At the same time, the shear expansion effect is taken into account in the model, so that not only the compressive state of brittle material can be described, but also the expansion state of the material can be described in the broken zone. The theoretical calculation results are compared with the numerical simulation results by using the material constitutive model developed by ourselves in the laboratory. It is found that the radial stresses calculated by these two methods are in good agreement with those obtained on the surface of the cavity wall. The critical radial stress of the cavity expansion behavior can also be obtained by the cavity expansion model. The penetration analysis model of two-stage ground drilling projectile is established. The relationship between the diameter of prefabricated holes in the target and the penetration depth of the projectile is studied, and compared with the experimental results, it is found that the two are in good agreement with each other. The second-level warhead system is optimized, and the relationship between the optimal penetration depth and impact velocity, the ratio of projectile-to-precharge diameter is obtained. The effects of load characteristics, such as peak load, loading rate and unloading rate, on the area of fracture and fracture around borehole are analyzed by numerical simulation. It is found that if the peak value of load is too high, a large area of fragmentation will be formed around the drilling hole, resulting in a waste of load energy and no positive effect on the propagation and extension of macro-coherent cracks. If the load peak is too low, the circumferential stress in the surrounding media is not enough to cause radial cracks, which is not conducive to the formation of macro-cracks. It is also found that under the condition of the same impulse, the trapezoidal load is better than the triangular load, and the loading rate and unloading rate of the load have a great effect on the number and length of cracks, and the higher the loading rate, the lower the unloading rate, and the higher the loading rate and the lower the unloading rate, the higher the loading rate and the lower the unloading rate. The longer the macro cracks are produced, the less the number of cracks is. When the critical radial stress of the cavity expansion behavior is used as the lower bound of the peak load, a better fracturing effect can be obtained. In this paper, the constitutive model of brittle materials developed by the laboratory is used to simulate the explosion cracking of granite drilling holes, and the results are compared with the experimental results reported in the literature and the experimental results in the laboratory. The results show that the constitutive model can simulate the damage and cracking behavior of brittle materials (rock and concrete) under dynamic impact load. The process of crack propagation driven by crack explosion gas is studied by numerical simulation method. The distribution of high pressure gas in crack and the opening displacement of crack at different positions are analyzed. It is found that the crack density increases with the increase of crack density. The higher the critical pressure is needed to drive the crack propagation; The combined action of high pressure gas immersion into the crack and expansion in the hole is better than that of only considering the single action of high pressure gas immersion into the crack, the former is a little better than that of the high pressure gas immersion in the crack.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：X932
本文编号：2465538
[Abstract]:Because of its high efficiency and low cost, blasting method has been widely used in mining, civil engineering, oil and gas engineering, etc. Therefore, it is of great theoretical significance and application value to study the mechanism of blasting, especially in drilling blasting. In this paper, the cracking behavior of brittle materials (rock and concrete) under explosive impact load is studied. Through theoretical analysis, numerical simulation and experimental study, the problem of borehole explosion cracking is studied systematically. The main contents include the following aspects: a hole expansion theoretical model is established according to the response behavior of the three different materials, such as the fragmentation zone, the crack zone and the elastic zone, which will occur at different distances from the explosion source after the drilling charge explodes, and the theoretical model of hole expansion is established according to the response behavior of these three kinds of materials. The difference between the model and the previous cavity expansion model is that the initial radius of the cavity is not 0 but a finite value. At the same time, the shear expansion effect is taken into account in the model, so that not only the compressive state of brittle material can be described, but also the expansion state of the material can be described in the broken zone. The theoretical calculation results are compared with the numerical simulation results by using the material constitutive model developed by ourselves in the laboratory. It is found that the radial stresses calculated by these two methods are in good agreement with those obtained on the surface of the cavity wall. The critical radial stress of the cavity expansion behavior can also be obtained by the cavity expansion model. The penetration analysis model of two-stage ground drilling projectile is established. The relationship between the diameter of prefabricated holes in the target and the penetration depth of the projectile is studied, and compared with the experimental results, it is found that the two are in good agreement with each other. The second-level warhead system is optimized, and the relationship between the optimal penetration depth and impact velocity, the ratio of projectile-to-precharge diameter is obtained. The effects of load characteristics, such as peak load, loading rate and unloading rate, on the area of fracture and fracture around borehole are analyzed by numerical simulation. It is found that if the peak value of load is too high, a large area of fragmentation will be formed around the drilling hole, resulting in a waste of load energy and no positive effect on the propagation and extension of macro-coherent cracks. If the load peak is too low, the circumferential stress in the surrounding media is not enough to cause radial cracks, which is not conducive to the formation of macro-cracks. It is also found that under the condition of the same impulse, the trapezoidal load is better than the triangular load, and the loading rate and unloading rate of the load have a great effect on the number and length of cracks, and the higher the loading rate, the lower the unloading rate, and the higher the loading rate and the lower the unloading rate, the higher the loading rate and the lower the unloading rate. The longer the macro cracks are produced, the less the number of cracks is. When the critical radial stress of the cavity expansion behavior is used as the lower bound of the peak load, a better fracturing effect can be obtained. In this paper, the constitutive model of brittle materials developed by the laboratory is used to simulate the explosion cracking of granite drilling holes, and the results are compared with the experimental results reported in the literature and the experimental results in the laboratory. The results show that the constitutive model can simulate the damage and cracking behavior of brittle materials (rock and concrete) under dynamic impact load. The process of crack propagation driven by crack explosion gas is studied by numerical simulation method. The distribution of high pressure gas in crack and the opening displacement of crack at different positions are analyzed. It is found that the crack density increases with the increase of crack density. The higher the critical pressure is needed to drive the crack propagation; The combined action of high pressure gas immersion into the crack and expansion in the hole is better than that of only considering the single action of high pressure gas immersion into the crack, the former is a little better than that of the high pressure gas immersion in the crack.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：X932
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