方波上升和下降沿处电场快速变化引起的位移电流和空间电磁波对局部放电(partial discharge,PD)的测量造成较大干扰。为此设计并检验了一种基于超高频(super high frequency,SHF,3~30 GHz)信号采集和下混频技术,适用于方波电场下绝缘系...方波上升和下降沿处电场快速变化引起的位移电流和空间电磁波对局部放电(partial discharge,PD)的测量造成较大干扰。为此设计并检验了一种基于超高频(super high frequency,SHF,3~30 GHz)信号采集和下混频技术,适用于方波电场下绝缘系统的PD检测方法。系统性能测试验证了SHF混频法能有效抑制方波电源的干扰,混频信号在降低频率的同时也保留了原SHF信号幅值和相位信息,且系统可检测到视在放电量20 pC左右的PD,灵敏度较好。SHF混频法与脉冲电流法和UHF法的对比实验结果表明,SHF混频法适于检测发生在绝缘强度较高材料中放电速度较快的PD。所设计系统在方波下,对环氧树脂和灌封硅胶两种绝缘封装材料进行了PD对比实验,验证了其实用性。展开更多
Thick earth-rock filled embankment of large earthwork volume often occurs during the construction of expressways in mountainous and hilly areas. The compaction quality of earth-rock filled subgrade will directly affec...Thick earth-rock filled embankment of large earthwork volume often occurs during the construction of expressways in mountainous and hilly areas. The compaction quality of earth-rock filled subgrade will directly affect the settlement deformation and stability of the embankment after filled. Therefore, effective evaluation on the compaction quality of the earth-rock filled subgrade is an unsolved critical technical issue to control the construction quality of highway engineering. Based on the wave propagation and electrical resistivity characteristics of the earth and rock fillings, a theoretical model of the compaction quality detection by wave-electric field coupling imaging diagnostic method was established. Then, two filled subgrade models containing cavities and heterogeneous bodies respectively were make separately, and by the wave velocity testing and electrical resistivity testing, the wave-electric field coupling imaging diagnostic method was applied to these two model. The result shows that it is feasible to use the wave testing technique and the electrical resistivity testing technique for a diagnostic test of the subgrade compaction quality. Based on the abnormal areas reflected by the wave velocity imaging and electrical resistivity imaging results, we are able to analyze the scope and site of distress but not able to quantitatively evaluate the subgrade compaction quality. We can accurately qualitatively analyze the subgrade compaction quality based on the wave-electric field coupling calculation model of fill subgrade quality proposed by this paper.展开更多
基金funded by National Natural Science Foundation of China(Grant No.51279219 and Grant No.51609027)Chongqing Research Program of Basic Research and Frontier Technology(Grant No.cstc2016jcyj A0016)
文摘Thick earth-rock filled embankment of large earthwork volume often occurs during the construction of expressways in mountainous and hilly areas. The compaction quality of earth-rock filled subgrade will directly affect the settlement deformation and stability of the embankment after filled. Therefore, effective evaluation on the compaction quality of the earth-rock filled subgrade is an unsolved critical technical issue to control the construction quality of highway engineering. Based on the wave propagation and electrical resistivity characteristics of the earth and rock fillings, a theoretical model of the compaction quality detection by wave-electric field coupling imaging diagnostic method was established. Then, two filled subgrade models containing cavities and heterogeneous bodies respectively were make separately, and by the wave velocity testing and electrical resistivity testing, the wave-electric field coupling imaging diagnostic method was applied to these two model. The result shows that it is feasible to use the wave testing technique and the electrical resistivity testing technique for a diagnostic test of the subgrade compaction quality. Based on the abnormal areas reflected by the wave velocity imaging and electrical resistivity imaging results, we are able to analyze the scope and site of distress but not able to quantitatively evaluate the subgrade compaction quality. We can accurately qualitatively analyze the subgrade compaction quality based on the wave-electric field coupling calculation model of fill subgrade quality proposed by this paper.
