动力作用下岩体裂隙扩展机制的数值模拟研究
发布时间：2019-05-22 21:54
【摘要】：近年来,随着我国经济建设的持续发展,地下岩土工程的规模不断扩大,各种复杂的岩体力学问题越来越受到重视。许多大型结构工程的失稳破坏都与爆炸、冲击等动荷,载密切相关,如矿山开采、隧道爆破等。岩石是一种典型的准脆性材料,具有显著的非均匀性,当动荷载达到岩石的强度极限时,能量会瞬间释放并引发应力重分布,使局部力学性质迅速劣化,裂隙高速扩展,工程中如处理不当将可能引起重大工程事故并造成巨大的经济损失。因此,研究动荷载作用下岩体裂隙的扩展具有重要的理论价值和实践意义。本文采用岩石动态过程破裂分析系统RPPA-dynamic,通过建立数值模型,对岩体在动荷载作用下裂纹扩展机制进行数值模拟研究。具体内容包括以下几个方面：1.通过阅读相关文献,归纳、概括了国内外学者对于动荷载作用下岩体的破坏形式与裂隙扩展在理论、物理试验和数值模拟等方面的研究现状。2.建立地应力作用下岩体受到爆炸作用的二维数值模型,模拟了岩体在爆破荷载作用下裂纹萌生、扩展、贯通破坏的过程。讨论了爆破应力波峰值强度、应力比和围压值大小对岩体破坏形式和裂纹扩展规律的影响。研究结果表明：(1)随着K值由0、0.25、0.5、0.75逐渐增大,岩体的破坏模式是近似的,最终都是形成与最大压应力方向一致的两条竖直方向的主裂纹,但是裂纹最终长度逐渐减小,说明应力比越大,岩体越不容易发生破坏。(2)爆炸应力波峰值对裂纹扩展有重要影响,峰值越大,裂纹扩展能力越强。(3)当应力比K=1时,孔洞周围出现四条互相垂直的主裂纹,且随着围压值不断增大,岩体内初始应力场改变,破坏由拉剪破坏转变为剪破坏为主,最终裂纹长度逐渐减小,围压大小对爆破裂纹扩展能力有明显的抑制作用。3.建立含单条预制裂隙岩石试样的数值模型,模拟了在动荷载作用下岩石试样中预制的单条裂隙扩展过程,研究了应力波波长、峰值以及预制裂纹倾角对裂纹扩展方式的影响,并讨论了动力与静力作用下的裂隙扩展差异。研究结果表明：(1)当应力波波长相对很短时,在平行于预制裂纹上方萌生新的裂纹,长度与预制裂纹一致；当应力波波长逐渐增大,在预制裂纹两尖端产生垂直于预制裂纹的翼裂纹并逐渐向岩石试样上下两端发展；当应力波波长增大到一定程度,岩石试样的破坏模式与静荷载作用下颇为接近。(2)岩石试样的破坏程度随着应力波峰值的增大而增大。(3)预制裂隙角度越大,岩体越不容易发生破坏,岩体强度呈现逐渐提高。(4)当应力波很短时,裂纹扩展方式主要由应力波波长控制,预制裂纹倾角的影响不明显。(5)动、静荷载作用下,岩石试样的破坏模式有很大区别。应力波在平行于节理面迎波面方向产生反射拉伸波,出现层裂现象,而静力条件下更容易出现翼型裂纹。
[Abstract]:In recent years, with the sustainable development of economic construction in China, the scale of underground geotechnical engineering continues to expand, and a variety of complex rock mechanics problems have been paid more and more attention. The instability and failure of many large-scale structural projects are closely related to explosion, impact and other dynamic loads, such as mining, tunnel blasting and so on. Rock is a typical quasi-brittle material, which has remarkable inhomogeneity. When the dynamic load reaches the strength limit of rock, the energy will release and cause stress redistribution, which makes the local mechanical properties deteriorate rapidly and the cracks expand at high speed. If handled improperly in the project, it may cause major engineering accidents and cause huge economic losses. Therefore, it is of great theoretical value and practical significance to study the expansion of rock mass cracks under dynamic load. In this paper, the rock dynamic process fracture analysis system RPPA-dynamic, is used to simulate the crack propagation mechanism of rock mass under dynamic load by establishing a numerical model. The specific contents include the following aspects: 1. By reading the relevant literature, this paper summarizes the research status of failure forms and fracture propagation of rock mass under dynamic load in theory, physical test and numerical simulation. 2. A two-dimensional numerical model of rock mass subjected to explosion under ground stress is established, and the process of crack initiation, propagation and penetration failure of rock mass under blasting load is simulated. The effects of blasting stress wave peak strength, stress ratio and confining pressure on the failure form and crack propagation of rock mass are discussed. The results show that: (1) with the increase of K value from 0, 0.25, 0.5, 0.75, the failure mode of rock mass is approximate, and finally two main cracks in vertical direction consistent with the direction of maximum compressive stress are formed. However, the final crack length decreases gradually, which indicates that the larger the stress ratio is, the less likely the rock mass will be destroyed. (2) the peak value of explosion stress wave has an important influence on crack propagation, and the larger the peak value is, the stronger the crack propagation ability is. (3) when the stress ratio is K 鈮，
本文编号：2483298
[Abstract]:In recent years, with the sustainable development of economic construction in China, the scale of underground geotechnical engineering continues to expand, and a variety of complex rock mechanics problems have been paid more and more attention. The instability and failure of many large-scale structural projects are closely related to explosion, impact and other dynamic loads, such as mining, tunnel blasting and so on. Rock is a typical quasi-brittle material, which has remarkable inhomogeneity. When the dynamic load reaches the strength limit of rock, the energy will release and cause stress redistribution, which makes the local mechanical properties deteriorate rapidly and the cracks expand at high speed. If handled improperly in the project, it may cause major engineering accidents and cause huge economic losses. Therefore, it is of great theoretical value and practical significance to study the expansion of rock mass cracks under dynamic load. In this paper, the rock dynamic process fracture analysis system RPPA-dynamic, is used to simulate the crack propagation mechanism of rock mass under dynamic load by establishing a numerical model. The specific contents include the following aspects: 1. By reading the relevant literature, this paper summarizes the research status of failure forms and fracture propagation of rock mass under dynamic load in theory, physical test and numerical simulation. 2. A two-dimensional numerical model of rock mass subjected to explosion under ground stress is established, and the process of crack initiation, propagation and penetration failure of rock mass under blasting load is simulated. The effects of blasting stress wave peak strength, stress ratio and confining pressure on the failure form and crack propagation of rock mass are discussed. The results show that: (1) with the increase of K value from 0, 0.25, 0.5, 0.75, the failure mode of rock mass is approximate, and finally two main cracks in vertical direction consistent with the direction of maximum compressive stress are formed. However, the final crack length decreases gradually, which indicates that the larger the stress ratio is, the less likely the rock mass will be destroyed. (2) the peak value of explosion stress wave has an important influence on crack propagation, and the larger the peak value is, the stronger the crack propagation ability is. (3) when the stress ratio is K 鈮，
本文编号：2483298
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