土石壩滲漏之啟發式反算分析

Abstract

台灣蓄水庫最常見之壩體型態為土石壩。依國外土石壩壩體破壞案例所累積之經驗，除壩頂溢流潰決破壞外，壩體滲漏亦為造成管湧破壞主要原因之一。管湧會造成壩體突然、全面之破壞，後果非常嚴重，日常需要透過滲漏量與水壓監測等數據來研判安全性。監測數據若有異常、有必要透過壩體內部問題診斷來尋求真正原因。本研究旨在透過啟發式最佳化反算分析，以土石壩滲流相關問題為例，期運用監測數據，配合數值模擬分析，找出對應異常監測數據之可能原因，目標在建構壩體異常問題診斷與詮釋之方法。本研究最佳化演算法採用和弦搜尋法，反算分析中以MATLAB作為和弦搜尋最佳化流程之主控伺服，常用之地工分析軟體FLAC則扮演計算引擎之角色。藉由相通介面資料傳遞至外部檔案方式進行兩種不同軟體間之溝通，可達到整體最佳化搜尋過程自動化之優點。本研究先藉兩座型態迥異之土石壩案例進行驗證分析，再以新山壩實際案例擬定兩種問題型態之情境，以評估本研究所研擬之和弦搜尋演算法應用於土石壩滲流問題診斷之功效，以說明此方法之可行性與有效性。

Embankment dam is the most common type of dams in Taiwan. Besides dam failure caused by overflow erosion, piping due to seepage is one of the major reason that may result in the breach of an embankment dam. Piping failure tends to take place unexpectedly and catastrophically. A proper program of monitoring for seepage and water pressure can help to reduce the chance of piping failure. When unusual monitored data occurs, an appropriate diagnosis will be essential to look for the real cause and timely solve the problem. This thesis aims to propose a diagnosis procedure by means of back analyses of earth-dam seepage problems using one of the heuristic optimization methods - the harmonic search method. This procedure incorporates the harmonic search algorithm into MATLAB as the optimization server and a commercial numerical simulation tool FLAC as the simulation engine to allow the simulated results match the monitoring data. A common data file serves as the interface communicating between MATLAB and FLAC. This work also makes use of two earth-dam seepage problems to demonstrate the feasibility and applicability of the proposed diagnosis procedure.