軟岩夾層中隧道受簡諧S波入射作用數值模擬

Numerical Simulation on Tunnels in Interbedded Soft Rock Layer Subjected to Incident Harmonic S-Wave

何金益(Jin-Yi He)

指導教授 ： 黃燦輝

共同指導教授 ： 王泰典

國立臺灣大學/工學院/土木工程學研究所/碩士(2017年)

https://doi.org/10.6342/NTU201704105

摘要

隧道若受地震損壞，往往需要耗費大量時間修復，影響交通甚鉅。近年來發生的大規模地震中，許多山岳隧道損害或坍塌，山岳隧道受震行為及其耐震設計逐漸受到重視。台灣之土壤隧道耐震設計已有具體規定，然國內對於山岳隧道少有耐震考量，耐震規範甚少，因此岩石隧道受震反應待進一步探討。
本研究旨在探討隧道於三岩層中之受震行為，使用有限元素法進行數值模擬。首先分析三層岩層受簡諧S波垂直向上入射之行為，紀錄各高程監測點位之力時最大位移及震波作功，以比較不同入射頻率、軟層厚度、阻抗比之影響。確定三層岩層受震行為後，於軟層加入隧道進行分析，比較不同軟層厚度、阻抗比及隧道位置對於隧道襯砌應力增量的影響。
分析結果顯示，三層岩層不含隧道受震後之行為可分為兩類，當震波時間與波長乘積小於該層厚度時，考慮與上下層之阻抗比及層厚的影響；當震波時間與波長乘積大於該層厚度時，波之折射與反射行為較為複雜，岩層厚度的影響較大。隧道襯砌軸應力增量受阻抗比之影響與三層岩層受震反應一致，因此可以三層岩層受震反應預測隧道襯砌軸應力之趨勢；而隧道襯砌剪應力與撓曲應力受下層與中層間阻抗比(α1)影響甚大，其增量值皆隨α1上升而下降。

關鍵字

岩石隧道 ； 阻抗比 ； 受震行為 ； 簡諧波 ； 襯砌應力增量

並列摘要

Once a tunnel was severely destructed by tectonic events, it took a long period and huge expense to recover the damage. In recent years, many tunnels damaged or collapsed because of earthquake. Seismic behavior and seismic design of mountain tunnel are emphasized lately. Lack of aseismic design and feasible engineering suggestion for rock tunnel in Taiwan, this research provides a preliminary study about the seismic behavior of rock tunnels.
This study investigate the seismic behavior of interbedded soft rock layer by simulating with finite element method. First, the maximum values of displacement and work at each position were recorded to compare the effect of incident wave frequency, thickness of interbedded rock and impedance ratio on displacement and work. After confirming the seismic behavior of three layered rock, a tunnel is added to the analysis and the factor of thickness of interbedded rock, impedance ratio and position of tunnel were discussed.
According to the numerical simulation results, seismic behavior of three layered rock can be divided into two categories. If the duration of vibration time multiplied by wave length is smaller than thickness, its seismic behavior is affected by impedance ratio and the thickness of rock besides it. On the other hand, the wave propagations will be more complicated, and the thickness plays a more important role. The trends of axial stress increment of lining are the same with three-layered-rock case, though we can approximately predict the trend of axial stress increment of lining. The shear stress and bending stress increment are affected by the impedance ratio of lower rock and interbedded rock (α1), and the increment decreases when α1 increases.

並列關鍵字

Rock tunnels ； Impedance ratio ； Seismic behavior ； Harmonic wave ； Stress increment of lining

參考文獻

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