懸臂式梳子壩力學與緩衝之研究

Abstract

梳子壩是土石流攔阻構造物中常被採用的方法。台灣目前施做的梳子壩大體上可分為重力式與懸臂式兩種，本研究由收集資料進行分析，在兼顧安全、攔阻效率及經濟目的，提出懸臂式梳子壩設計上應考量之項目。為使壩體保持安定，本文針對梳子壩面臨河道中四種不同狀況，經由合理之力學計算，分析壩體穩定性。四種狀況分別為：空壩時土石流推擊、淤滿後靜土石堆積+最大設計地震、壩體上游土石流淤滿後土石流溢流、壩體上游土石流近淤滿時巨礫撞擊。 由於部分防砂構造物或橋樑橋墩雖依規範設計，仍可能擋不住巨大之土石推移力或衝擊力，所以本研究進行衝擊試驗，模擬防砂構造物前加置廢輪胎緩衝材料，是否能有效地消減撞擊時之能量，以保護結構物之安全。結果顯示，於坡度40~130時，皆可降低93%之最大衝擊力，若於廢輪胎內填充砂石（或細砂）者，則可降低95%或以上之最大衝擊力。因此廢輪胎緩衝材料具有很好的緩衝、消能效果，可達保護結構物安全之效能。

Slit dam, is usually adopted to intercept debris flow and thus reduce its impact on downstream areas. There are two main types of retaining structures used for the slit dam design in Taiwan, namely, gravity type and cantilever types. In this study, we collected various design data of slit dams in Taiwan to study the safety issue and the efficiently on blocking debris and building costs as well. To investigate the stability of the cantilever type slit dam, four different conditions were analyzed as follows. (1) Empty dam impacted by debris flow. (2) Full filled dam with normal flow under maximum designed earthquake. (3) Full filled dam with maximum flow. (4) Nearly full filled dam stricken or impacted by huge rock at the top of the dam. Owing to the fact that certain structures may not survive the impact due to huge falling rocks even when they were designed by codes. It is intended to carry out impact tests on the proposed used-tire cushion materials to evaluate the effectiveness of such devices on reducing the maximum impact force. The results indicate that used-tire cushion material can significantly decrease the maximum impacted force about 95% or higher for slopes between four to fourteen degrees. It is then concluded that these use-tire cushion materials may have excellent potentials to be applied to maintain the safety of retaining structures. As a result, it seems more economically efficient to design retaining structures with used-tire cushion systems than those without used-tire cushion systems.