FEM Analysis on the PD-3 Tunnel Section

유한 요소법에 의한 터널해석(사례문제 2)

For the tunnel pattern of PD-3, a numerical analysis using the FEM program, MrSoil, was conducted with given geotechnical properties of surrounding rockmasses to verify the analysis results by comparing with other programs. The analyzed domain was extended to the far enough distance from the excavation surface to avoid the restrained effect by the boundary condition, and the construction sequence was employed in the analysis as calculation steps to simulate the time dependent 3 dimentional behavior of surrounding ground due to tunneling. Maximum 35 mm of the tunnel crown settlement and about 13 mm of the surface settlement were computed and the amount of settlement may not give any structural damage on the concrete structures on the ground surface. The shotcrete stress of 84 kg/cm2 and the rockbolt axial force of 9 ton as a maximum are within the allowable limit. The plastic zone was restricted near the excavation surface, but forepoling around the crown may be required to prevent rock falling. It is believed that the tunnel is designed reasonablely from the economical and safety points of view.

주어진 터널 斷面 및 地盤條件을 對象으로 1次元 有限要素 프로그램인 MrSoil을 利用하여 數値解析을 遂行하고 그 結果를 本稿에 收錄하였다. 解析 모델은 過去의 터널 計測 結果等에 根據하여 터널 掘進 影 이 充分히 적은 地域까지로 擴張 設定하여 境界條件에 의한 解析結果에의 影響을 最小化하도록 하였으며, 3次元的인 터널 擧動을 適切히 Simulation 하기 위하여 施工順序를 導入하여 段階別로 解析을 遂行하였다. 解析結果 터널 天井部는 最大 約 35mm의 沈下가 豫想되며, 地表面 沈下는 13mm 以內로서 地上 構造物의 構造的인 被害는 없을 것으로 判斷된다. 支保工인 Shotcrete와 Rockbolt의 最大應力 및 軸力도 各各 84 Kg/cm2 및 9론 以內로서 許容値 以內이고, 掘面 周邊의 塑性領域은 Rockbolt 길이 以內로 制限되고 있으므로 天井部에 Forepoling을 設置한다면, 터널 安全에는 影響을 미치지 않을 것으로 判斷되므로 本 터널은 合理的이며 適切히 設計된 것으로 評價된다.