以板波頻散現象檢測板式無碴軌道CA砂漿層損害之初步研究

The preliminary study of using the dispersive velocities of Lame waves to detect the Asphalt mortar defect in SLAB Ballastless Track

詹琇如(Hsiu-Ju Chan)

指導教授 ： 鄭家齊

朝陽科技大學/理工學院/營建工程系/碩士(2019年)

摘要

本研究是以混凝土板表面經敲擊後激發出的應力波，探討無碴軌道結構檢測中間CA砂漿層的內部瑕疵，以一個敲擊源及一個接收器長距離配置的方式檢測，訊號以短時傅立葉轉換及再分配時頻譜求得頻散曲線。此外，進行CA砂漿材料的文獻回顧及試拌。
利用有限元素分析混凝土板-CA砂漿層-混凝土三層複合版模型，其中內含缺陷與無缺陷進行討論，所得之位移波形由Matlab程式將再分配時頻譜中做A0板波模態頻散曲線擷取，並顯示成波長波速圖。
數值分析結果顯示，敲接間距1.2 m結果優於2.0 m，CA砂漿層完全剝離的狀況下，無論CA砂漿層的厚度或裂縫位置，均可分辨裂縫的存在。CA砂漿層厚度為3 cm 之模型在裂縫半徑0.3m即可分辨出裂縫的存在。CA砂漿層厚度為13 cm之模型，裂縫在CA砂漿層下方較易測出，裂縫在上方時，裂縫長度為敲接間距時才能分辨。
CA砂漿材料研究方面，第I型試體與第II型試體之波速分別為1250 m/s及1730 m/s左右，試拌之第I型的平均抗壓強度無達到標準，第II型平均抗壓強度有達到標準，強度與配比中水泥含量有相當大的關係。

關鍵字

CA砂漿 ； 蘭姆波 ； 缺陷 ； 頻散曲線

並列摘要

The purpose of this research is on detecting flaw of the intermediate Asphalt mortar defect in SLAB Ballastless Track layer using the characteristics of Lamb waves generated by an impacting force applying on the surface. The experiments were conducted by the configuration with one excitation source and one receiver. The dispersion curves of the test results were obtained by short-time Fourier transform spectrum and amplitude reassigned method. In addition, review and trial mixing of CA mortar materials were included.

The finite element analysis was carried out with the concrete-CA mortar-concrete three-layer composite plate models. The results with and without defects inside the CA mortar layer were discussed. A0 modal dispsersion curve was obtained from the reassigned spectrogram and displayed as a wavelength wave velocity diagram.

he numerical simulation results show the impacting and receiver distance of 1.2m is better than 2.0m. For the conditions that the CA mortar layer is completely peeled off, regardless of the thickness of the layer or crack position, the presence of cracks can be assessed. The existence of cracks can be distinguished at a crack radius of 0.3 m for the model with CA mortar layer thickness of 3 cm. For the model with CA mortar layer thickness of 13 cm, the cracks located at the bottom surface of the CA mortar layer can be found easier, but, for the crack located at the top surface, the crack can only be identified when the crack length is same as the impact-receiver distance.

The wave velocities of the type I and the type II CA mortar are 1250 m/s and 1730 m/s for the trial batches. The average compressive strength of the type I of trial mixing did not reach the Chinese Standard while the type I CA fullfilled the Standard. The cement content in the mixure proportion directly affects the compressive strength of the CA mortar.

並列關鍵字

CA mortar ； Lamb wave ； Defect ； Dispersion Curves

參考文獻

1. Graff, K. F., “Wave Motion in Elastic Solids,” Oxford University Press, London, 1991.

2. Brillouin, L., “Wave Propagation And Group Velocity,” New York and London, Academic Press Inc, pp.1-2, 1960.

3. 倪勝火，「表面波譜分析法（SASW）之分析原理與應用」，地工技術，第86期，第5-18頁，2001。

4. Cho, Y. S., “Spectral analysis of surface wave response of multi-layer thin cement mortar slab structures with finite thickness,” NDT & E International, Vol.34, No.2, pp.115-122, 2001.

5. Kim, D. S., Shin, M. K., Park, H. C., “Evaluation of density in layer compaction using SASW method,” Soil Dynamics and Earthquake Engineering, Vol.21, No.1, pp.39-46, 2001.