廢棄掩埋場現地試驗與三維穩定分析

Abstract

雖然台灣的廢棄物處理逐漸以焚化取代掩埋，然而無論是不可燃的廢棄物、焚化灰渣、或者是離焚化場運距較遠的鄉鎮，仍將繼續以掩埋為其主要的處理方式。台灣因為地狹人稠，所以許多掩埋場位於山坡地上，這些掩埋場破壞的可能原因就是在掩埋場的設計時，並未進行嚴密的邊坡穩定分析；在營運期間也並未考量到穩定性的問題。本研究的目的在於利用現地試驗，直接求出廢棄物的剪力強度，並利用這些參數進行邊坡穩定分析。 結果顯示，竹南及湖口掩埋場的強度參數內聚力(c)、摩擦角(□)分別為34.9 kPa、37.9□以及33.6 kPa、32.1□，竹南掩埋場的廢棄物雖然含有較高比例之一般事業廢棄物，其剪強度參數與湖口掩埋場所得之結果略高。另外以平鈑載重試驗求得的地盤反力係數(kv)為875.25 kN/m3與494.33 kN/m3。在邊坡穩定分析方面，二維與三維的分析結果均顯示邊坡滑動的安全係數隨界面剪力強度降低、廢棄物填埋高度增加、填埋體長度減少而減少。二維與三維分析結果比較，開口型的掩埋場三維分析所得之邊坡滑動安全係數較二維者低，且二者間之區別隨開口之角度增加而減少。

Due to the limitation of population density and availability of land, a large portion of Taiwan’s landfills are located in mountainous area. Current regulations do not require slope stability analysis for these landfills. As a result, almost all of the landfills were not designed to maintain a suitable factor of safety against failure. The composition of Taiwan’s solid waste differs considerably from that of the United States or any other country in the world. However, the lack of data of local solid waste poses a great limitation to engineers. The objectives of this research are to collect shear strength data from in-situ tests and perform a series of stability analyses. The results show that the cohesion and friction angle of the MSW at Chu-nan and Hu-kou landfills are 34.9 kPa and 37.9°, 33.6 kPa and 32.1°, respectively. In addition, the coefficients of sudgrade reation are 875.25 kN/m3 and 494.33 kN/m3, respectively. Results of 2-D and 3-D slope stability analyses show that the factor of safety increases with lower height of wastes, longer length of waste body, smaller slope angle of the back of the excavation, and steeper face slope of final cover. In addition, 3-D analysis indicates that the factor of safety decreases with the widening of the mouth of the landfills on slopes.