全级配混凝土/玄武岩界面直接拉伸断裂研究

Study on direct tensile fracture of fully-graded concrete / basalt interface

摘要

【目的】以建在基岩上的混凝土坝建基面地震稳定分析为背景，开展全级配混凝土/玄武岩界面静动态断裂试验研究。【方法】试验采取含预制裂缝的圆柱体复合试件承受直接拉伸的形式。在地震荷载典型应变率范围内考虑两种加载速率，其中应变率10^-3/s为动态加载，应变率10^-6/s作为准静态加载。测得了试件的荷载-位移曲线，据此计算全级配混凝土/玄武岩界面的断裂参数，结合数值模拟得到了断裂韧度。【结果】研究表明：准静态加载下复合试件沿预制裂缝扩展，而动态加载下试件在扩展过程中向玄武岩中含天然斜裂缝位置偏转。【结论】相比于准静态加载，复合试件在动态荷载作用下有更高的断裂参数。而与全级配混凝土对比，复合试件在准静态加载下的断裂参数显著降低。通过本次研究，可为全级配混凝土/玄武岩界面准静态和动态作用下的断裂性能提供参考。

Abstract

[Objective] Based on the seismic stability analysis of the foundation surface of concrete dam built on bedrock, the experimental study on static and dynamic fracture of fully graded concrete/basalt interface is carried out. [Methods] The tests were conducted in the form of cylindrical composite specimens subjected to direct tension containing preset cracks. Two loading rates were considered in the range of typical strain rates for seismic loading. The load-displacement curves of the specimens were measured, from which the fracture parameters of the full-graded concrete/basalt interface were calculated and the fracture toughness was obtained in combination with numerical simulations. [Results] The results show that the composite specimens under quasi-static loading expanded along the preset cracks, whereas the specimens under dynamic loading were deflected towards the location of the natural diagonal cracks contained in the basalt during expansion. [Conclusion] Compared with the quasi-static loading, the fracture parameters of the composite specimen are all increased. Furthermore, t the fracture parameters of composite specimens under quasi-static loading were significantly reduced compared to fully-concrete. The present study can provide a reference for the fracture properties of the fully-graded concrete/basalt interface under quasi-static and dynamic loading.

关键词

动态直接拉伸断裂 / 全级配混凝土/玄武岩界面 / 位移外推法 / 试验-数值耦合法 / 变形 / 混凝土 / 影响因素

Key words

dynamic direct tensile fracture / fully-graded concrete/basalt interface / displacement extrapolation method / coupled experimental-numerical approach / deformation / concrete / influencing factors

基金资助

国家自然科学基金项目(51979292)