模态分析在隧道二衬脱空声振检测中的应用

Application of Modal Analysis in Acoustic-vibration Detection of Tunnel Secondary Liner Void

研究目的:声振法在隧道二衬脱空检测中具有低成本、易实施的特点,但由于仪器设备及技术手段限制,目前尚无成熟可靠的脱空识别判定依据。针对单次振动激励下的响应块体,本文通过进行数值模态分析,以得到模态参数与二衬结构形态参数的对应关系,从而提出定量的脱空判定标准。研究结论:(1)完全脱空响应块体基频值随平均脱空深度增大呈三次多项式规律增大,浅部脱空块体的基频值低于深部脱空块体,平缓脱空面较倾斜脱空面块体基频值更大,脱空面为水平时基频达到最大值;前两阶固有频率差值变化规律同基频-平均脱空深度曲线类似;(2)局部脱空响应块体基频值随脱空长度增大呈Logistic函数规律减小,脱空长度相同时,基频值随起始脱空深度增大而增大;前两阶固有频率差值随脱空长度增大而增大,结果曲线在脱空长度为30 cm处存在节点,前后差异明显;(3)由判定曲线图可确定二衬结构的精确形态参数,实现定量脱空判定,并提出了快速求得脱空特征参数的作图法;(4)该研究成果可为声振法在隧道二衬脱空检测中的工程运用提供理论依据。

Research purposes： The acoustic -vibration method has the characteristics of low cost and easy implementation in the detection of tunnel secondary liner void, but because of the restriction of equipment and technical means, there is no mature and reliable basis for void identification currently. For response block under the single excitation of vibration, the numerical modal analysis is done, to obtain the relationship between modal parameters and morphological parameters of secondary liner structure, and propose quantitative determination criteria for void. Research conclusions： （ 1 ） The fundamental frequency value of completely void block increases with the increase of average void depth in cubic polynomial law, fundamental frequency value of shallow void block is lower than the deep void block overall, and fundamental frequency value of subdued surface void block is higher than inclined surface, the value of level void surface reaches the maximum. The change rule of the first two natural frequency differentials is similar to the frequency - average void depth curve. （2） The fundamental frequency value of local void block increases with the increase of void length in Logistic function law, for the same void length, fundamental frequency value increases with the increase of the initial void depth, the first two natural frequency differentials increase with the increase of void length, the curve has a node at the length of 30 cm, there is significant difference before and after. （3） The precise morphological parameters of the secondary liner structure can be determined through the decision graph, so the quantitative void identification is realized, then presenting a fast drawing method to obtain the accurate information of the void characteristics. （4） The research results can provide theoretical basis for engineering application of acoustic - vibration method in tunnel secondary liner void detection.