青藏高原环境下混凝土结构密实性超声无损检测研究

ULTRASONIC NON-DESTRUCTIVE TESTING OF CONCRETE STRUCTURES COMPACTNESS UNDER CIRCUMSTANCES OF QINGHAI-TIBET PLATEAU

青藏高原的环境条件限制常导致混凝土出现密实性缺陷问题,如何对混凝土的密实性缺陷进行精确的无损检测,是保障结构承载力及耐久性的关键。该文结合此前在西藏雅鲁藏布江藏木大桥与广西南宁实地开展的混凝土超声试验结果,基于不同气压下混凝土实体的超声波速计算模型,建立了以气压、水胶比为参数的混凝土实体部分超声波速计算模型;进一步对混凝土在不同孔隙率、缺陷条件、骨料分布情况条件下的超声波速进行了计算分析。揭示了孔隙率及缺陷条件对混凝土超声波速的影响规律及机理。研究了骨料分布占比对混凝土超声检测结果的影响规律,建立了混凝土整体超声波速的多因素计算模型,并提出了基于超声波速的混凝土密实性统计分析方法,可以为实际工程中混凝土结构密实性的超声无损检测结果分析提供理论依据。

The environmental conditions of Qinghai-Tibet Plateau lead to the problem of compactness defects in concrete.Accurate non-destructive testing of concrete compactness defects is the key to ensuring the bearing capacity and durability of the structure.In this study,one ultrasonic pulse velocity(UPV)calculation model was established for the concrete entity part with air pressure and water-cement ratio as calculation parameters upon the UPV calculation model of concrete entities under different air pressures and combined with the results of the previous concrete ultrasonic tests carried out on Zangmu Bridge of Yarlung Zangbo River in Tibet and Nanning of Guangxi;and further calculated and analysed the UPV of concrete under the conditions of different porosity,of defects,and of aggregate distribution to reveal the influence regularity and mechanism of porosity and defects on UPV of concrete,to study the influence rule of aggregate distribution proportion on ultrasonic test results of concrete,to establish a multi-factor calculation model for overall UPV of concrete,and to propose a statistical analysis method of concrete compactness based on UPV.It is hoped that this study can provide a theoretical basis for the analysis of ultrasonic non-destructive testing results of concrete structure compactness in practical engineering.