英文篇名
Use of T3 Program to Simulate and Study the Behavior of Cantilever Retaining Walls
作者
林婷媚、林卓民、黃于庭
關鍵字
懸臂式擋土壁、TORSA3、T3-STONE
摘要
工程上採用懸臂式擋土壁開挖工法之優點為開挖時無內支撐障礙可縮短工期,也無斜坡明挖超挖區所需之回填土,因此只要在地層條件及周圍環境許可下,此種工法屬大面積開挖之首選。然懸臂式擋土壁之設計檢核項目目前尚無明確之定義,僅由設計者自行根據經驗或參考相關文獻進行設計。本文除簡要介紹常用於懸臂式擋土壁之鋼軌樁、型鋼樁及鋼板樁施工外,另採用國內學者研發之T3-STONE軟體內含之懸臂式擋土壁貫入深度計算及TORSA3軟體進行參數研究。參數研究結果顯示,當貫入深度之安全係數(FS)已達1.5,額外再增加之壁體長度對減少壁體變位無助益,若是改以增加壁體勁度,則可獲得不同結果。本文亦介紹兩個使用鋼板樁無支撐工法之實際案例,其中之一為成功案例,另一則屬失敗案例。由失敗案例得知除地層條件外,現場施工及管理不佳都有可能造成懸臂式擋土壁不穩定,因此緊急應變措施之擬定極為重要。程式是提供工程師分析之工具,真正設計還需仰賴工程師經驗判斷。
英文摘要
Not having to install internal bracing is the apparent advantage of using a non-supported cantilever retaining wall, which helps to shorten the excavation schedule. Another benefit is that there is no need for backfilling comparing to an open excavation with side slopes. Therefore whenever the situations allow, the cantilever retaining wall is always a popular choice among designers. However, how the cantilever retaining wall should be designed is not yet well understood, the designers must rely on experience and sporadic literature to make their best judgment. This paper describes the use of rails, H-section steel and sheet pile in configuring the cantilever retaining wall. The global stability of the cantilever retaining wall is checked by the T3-STONE software, while parametric studies are conducted by the TORSA3 program to further investigate the characteristics of cantilever retaining wall has an insignificant effect on further reducing the wall displacement. The wall displacement can only be effectaining wall. As indicated by the parametric studies, once the factor of global stability exceeds 1.5, increasing the depth of retively reduced by increasing the overall stiffness of the cantilever retaining wall. This paper also addresses two case histories using sheet piles as the cantilever retaining wall, one successful, while the other failed. The main reason for the failed case is attributed to the local variation of the ground condition that was not identified in the site investigation program. It is also undeniable that poor construction practice and filed management can also lead to the unexpected failure of a cantilevered excavation. In view of this, a contingency plan
must always be planned to counter the unforeseeable ground condition. Though computer programs are indispensable tools for engineers to design the cantilever retaining wall, sound engineering judgment is still required to arrive at the eventual design.