爆炸荷载作用下水泥砂浆试块裂纹扩展及数值模拟研究

发布时间：2018-04-17 05:19

本文选题：裂纹扩展 + 高速摄像　；参考：《安徽理工大学》2017年硕士论文

【摘要】：随着社会的发展,混凝土成为城市建筑、道路施工等领域的主要原材料,具有广泛的应用前景。但大多对混凝土的静载荷作用下进行研究,对动载荷条件下研究较少,特别是在爆炸荷载作用下,岩石裂纹扩展比较复杂,没有对其进行精确的分析和研究。爆破技术在各个领域得到广泛的应用,研究爆炸作用下混凝土的裂纹扩展,能够很好的控制爆破方向和岩石破碎程度。混凝土由粗细不同的骨料组成,均匀性较差,研究在超动态荷载条件下的破碎情况比较困难。本文采用相对均匀的水泥砂浆试块代替混凝土,研究在爆炸荷载的作用下,试块裂纹扩展情况,特别在光面爆破、预裂爆破等特种爆破中,能够很好的控制爆破方向和岩石的裂纹发展趋势,为工程爆破提供一定的数据支持。通过实验的方法,利用HX-3高速摄像机拍摄不同药量的炸药在水泥砂浆试块中爆炸产生裂纹的过程,及爆生气体对混凝土的破坏,了解试块破坏的机理。采用示波器测量试块表面一定距离裂纹扩展时间,通过对数据的处理得到裂纹扩展速度。通过ANSYS LS-DYNA有限元软件模拟爆炸应力波在水泥砂浆试块内的作用过程,以及研究试块的损伤情况,实验结果与模拟结果进行比较和分析,得出以下几点结论:(1)采用电测法可以得出,炸药在试块中爆炸时,随着药量的增加,裂纹扩展速度越快,裂纹扩展主要是由反射拉伸作用,扩展效果越明显。(2)试块在爆炸作用下,裂纹扩展过程主要是爆炸应力在炮孔周围形成微裂纹,爆生气体在微裂纹中增加裂纹的扩展,爆炸应力在边界形成的反射拉伸应力再次增加裂纹的扩展。裂纹扩展过程主要有两部分组成,一是爆炸应力、反射拉伸应力、爆生气体形成一条裂纹,二是其它裂纹在爆炸应力、反射拉伸应力、爆生气体和第一条裂纹形成的过程产生环向拉伸应力共同作用,形成其它裂纹,第一条裂纹消耗大量能量,产生环向拉伸应力。因此,其它几条裂纹扩展速度比第一条裂纹较快。(3)采用ANSYS内JHC混凝土模型对实验进行模拟,模拟结果与实验结果进行比较得出,JHC损伤模型能够很好的模拟试块中爆炸应力波的传播过程、应力大小、试块的损伤程度,通过应力和损伤程度能够体现试块的破碎情况。实验结果与模拟结果基本一致,很好的描述试块裂纹扩展过程和试块的破碎情况。
[Abstract]:With the development of society, concrete has become the main raw material in the field of urban architecture and road construction.However, most of the researches are carried out under the static load of concrete, but less on the condition of dynamic load. Especially under the action of explosion load, the crack propagation of rock is more complicated, and it is not accurately analyzed and studied.Blasting technology has been widely used in various fields. To study the crack propagation of concrete under explosion can well control the direction of blasting and the degree of rock fragmentation.The concrete is composed of different aggregates with different thickness, and the uniformity is poor. It is difficult to study the breakage of concrete under the condition of super dynamic load.In this paper, a relatively uniform cement mortar test block is used to replace concrete, and the crack propagation of the specimen is studied under the action of explosion load, especially in the special blasting such as smooth blasting, pre-splitting blasting and so on.It can control the direction of blasting and the development trend of rock cracks, and provide some data support for engineering blasting.By using HX-3 high-speed camera, the process of crack caused by explosive explosion in cement mortar specimen was recorded by using HX-3 high-speed camera, and the damage of explosive gas to concrete was also studied, and the failure mechanism of the specimen was understood.The crack propagation time is measured by oscilloscope and the crack propagation velocity is obtained by processing the data.The action process of explosive stress wave in cement mortar was simulated by ANSYS LS-DYNA finite element software, and the damage of cement mortar was studied. The experimental results were compared with those of simulation.The following conclusions can be drawn: (1) when the explosive explodes in the sample, the faster the crack growth rate is, the faster the crack growth is, and the more the effect of reflective tension is, the higher the explosive explosive is when it explodes in the sample.The more obvious the propagation effect is, the more obvious the crack propagation process is under explosion. The main process of crack propagation is that the explosion stress forms microcracks around the hole, and the explosion gas increases the crack propagation in the microcrack.The reflection tensile stress formed by explosion stress at the boundary increases the crack propagation again.The process of crack growth is composed of two parts, one is explosive stress, the other is reflective tensile stress, and the other is that other cracks are in explosive stress, reflecting tensile stress.The gas generated by explosion and the process of formation of the first crack together produce the toroidal tensile stress and form other cracks. The first crack consumes a great deal of energy and produces the toroidal tensile stress.Therefore, several other cracks propagate faster than the first crack. (3) the JHC concrete model in ANSYS is used to simulate the experiment.Compared with the experimental results, the JHC damage model can well simulate the propagation process of explosive stress wave, the magnitude of stress, the damage degree of the specimen, and the fragmentation of the specimen can be reflected by the stress and damage degree.The experimental results are in good agreement with the simulation results. The process of crack growth and the breakage of the specimen are well described.
【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】：TQ177.62

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