岩石—混凝土界面断裂特性与界面拉伸软化本构关系试验研究

发布时间：2018-06-10 17:49

本文选题：岩石-混凝土界面 + 界面裂缝　；参考：《大连理工大学》2014年硕士论文

【摘要】：建立在岩石基础上的混凝土大坝,由于基岩-混凝土界面开裂问题,易引发坝体失稳等安全事故。混凝土坝与基岩的薄弱界面在荷载、水流及温度变化等作用下极易产生裂缝并沿建基面不断扩展,直至坝体溃决。因此,坝踵处坝体与基础岩石的开裂可归结于基岩-混凝土界面开裂问题。然而,岩石和混凝土两种材料本身具有的非均质性与各向异性等属性加深了界面裂缝问题的复杂程度。因此,对岩基与混凝土坝体的界面断裂性能及其裂缝扩展问题进行研究,对大坝的安全使用具有重大意义。基于基岩-混凝土界面裂缝问题研究的必要性,本文开展了如下的研究工作： (1)人工切槽界面断裂特性试验研究均采用一半为岩石一半为混凝土的界面复合试件,对岩石表面进行人工切槽处理,对尺寸为500mm×100mm×100mm的复合试件进行了三点弯曲断裂试验,同时进行了轴向拉伸与劈裂试验。试验结果表明,随着界面粗糙度的增加,岩石-混凝土界面的抗拉强度、断裂韧度及断裂能均有大幅度提高,可以通过增加界面粗糙度的方式来提高界面的抗弯及抗裂性能。 (2)自然界面断裂特性试验研究通过三点弯曲加载试验使岩石形成自然断面,并将其与另一半混凝土结合制成复合试件,按预制裂缝设计5种初始缝高北a0/D,对尺寸为500mm×100mm×100mm界面试件进行三点弯曲试验。试验结果表明,随着a0/D的增加,试件的起裂荷载和最大荷载逐渐减小,抗折强度逐渐增大；试件的起裂韧度的和断裂能不随a0/D变化,认为是与a0/D无关的断裂参数。 (3)界面拉伸软化本构关系的确定及数值应用采用改进的J积分法,通过试验获得的荷载-加载点位移(P-δ)曲线,进而根据裂缝扩展过程中的能量损耗,建立与Hillerborg提出的粘聚力模型下的能量平衡关系,确定了界面软化本构关系。采用本文得到的软化本构关系,并引入Ⅰ型裂缝扩展准则,对岩石-混凝土界面裂缝扩展全过程进行数值模拟。研究表明,试验结果与数值计算结果吻合良好,从而验证了界面软化本构关系的正确性。
[Abstract]:Concrete dam based on rock is liable to lead to dam instability and other safety accidents due to the crack between bedrock and concrete interface. The weak interface between concrete dam and bedrock is easy to produce cracks and expand along the foundation surface under the action of load, water flow and temperature change, until the dam body collapses. Therefore, the cracking between the dam body and the foundation rock at the dam heel can be attributed to the crack between the bedrock and concrete interface. However, the heterogeneity and anisotropy of rock and concrete increase the complexity of interfacial crack problem. Therefore, it is of great significance to study the interface fracture performance and crack propagation of rock foundation and concrete dam. Based on the necessity of the research on the interfacial crack between bedrock and concrete, the following research work has been carried out in this paper: (1) the experimental research on the fracture characteristics of the interface between the artificial cut groove and the concrete interface is carried out by using the composite specimen which is half rock and half concrete. Three point bending fracture tests were carried out for the composite specimens with the size of 500mm 脳 100mm 脳 100mm, and the axial tensile and splitting tests were carried out at the same time. The experimental results show that the tensile strength, fracture toughness and fracture energy of the rock-concrete interface increase greatly with the increase of the interfacial roughness. The flexural and crack resistance of the interface can be improved by increasing the roughness of the interface. Combined with the other half of concrete, the composite specimen was designed according to the precast crack, and five kinds of initial joint height (a _ 0 / D) were designed. The three-point bending test was carried out on the 500mm 脳 100mm 脳 100mm interface specimen. The experimental results show that with the increase of a _ 0 / D, the initiation load and maximum load of the specimen decrease gradually, and the flexural strength increases, and the initial fracture toughness and fracture energy of the specimen do not change with a _ 0 / D. It is considered to be a fracture parameter independent of a _ 0 / D. The determination and numerical application of tensile softening constitutive relation at the interface are obtained by using the improved J-integral method and the load-loading point displacement (P- 未) curves obtained by experiments. Furthermore, according to the energy loss during crack propagation, the energy balance relationship under the cohesive force model proposed by Hillerborg is established, and the constitutive relation of interface softening is determined. Based on the softening constitutive relation obtained in this paper and the model I crack propagation criterion, the whole process of crack propagation at the rock-concrete interface is numerically simulated. It is shown that the experimental results are in good agreement with the numerical results, which verifies the correctness of the constitutive relation of interface softening.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TV642;TV313

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