DTS检测灌注桩桩完整性的光纤布设优化研究

Study on optical fiber layout optimization of DTS for detecting the integrity of cast-in-place piles

DTS应用于灌注桩完整性检测的研究对提高桩基质量、节约施工时间具有重要的经济意义。采用物理和数值模型试验方法,对DTS检测灌注桩完整性的光纤检测系统的优化进行研究。根据理论分析提出确定合理光纤间距的基本原则;采用物理模型试验,设置加热功率为4,8,12和16W/m对内置光纤热源的桩体热传导特征进行研究;应用有限元分析,对物理模型依次施加对应的中心热荷载22℃,24℃,28℃,32℃进行验证。研究结果表明:加热功率越大,中心线温度越高,光纤热源的临界半径也越大;距离中心线热源越近,温升值越高;边界条件不同,距离热源相同距离处的温升值不同,光纤的临界半径也不同;光纤结构对热传导特征影响明显;用功率4~16W/m加热长度为28m的光纤时,U型布设光纤的间距48cm左右最合理。数值模型与物理模型试验结果较吻合,且能很好地补充物理模型试验的不足,研究结果和手段为DTS检测灌注桩完整性的检测系统设计提供理论依据和技术指导。

The application of DTS on the integrity testing of cast-in-place piles has an economic significance which improves pile foundation quality and saves construction time.The optimization of the optical fiber detection system for DTS detection of the integrity of the cast-in-situ pile was studied by physical and numerical model test methods.According to the theoretical analysis,the basic principle that determines proper fiber spacing is proposed.The physical model test is used to set the heating power of the built-in fiber heat source by 4 W/m,8 W/m,12 W/m and 16 W/m.The meta-analysis is carried out by applying the corresponding central thermal loads in 22℃,24℃,28℃,32℃to the physical model respectively.The results show that the higher the heating power is,the higher the centerline temperature is,and the larger the critical radius of the fiber heat source is.The closer the heat source is to the centerline,the higher the temperature rise value.The boundary conditions are different,and the temperature rise at the same distance from the heat source is different.The critical radius of the fiber is also different;the fiber structure has a significant influence on the heat conduction characteristics;when the fiber with a length of 28 m is heated by 4–16 W/m,the spacing of the U-shaped fiber is about 48 cm.The numerical model is in good agreement with the physical model test results and can effectively make up the insufficiency in the physical model test.The research results and methods provide a theoretical basis and technical guidance for the design of the detection system for DTS detection of the integrity of the cast-in-situ pile.