雲林地區沖積層大深度壓密沉陷行為之研究

Investigating the Settlement Behavior of Yun-lin Alluvium at Large Depth

蔣榮(Chiang, Jung) ； 吳建宏(Wu, Jian-Hong) ； 林宏明(Lin, Hung-Ming)

《中華防災學刊》 9卷2期 (2017/08) Pp. 147-153

摘要

元長鄉及土庫鎮等雲林縣內陸地區地層下陷主要來自深度大於150m深層土層之壓縮，約占整體下陷量的三分之二，歷年來測沉磁環之監測資料也可看出即使兩土層厚度相近，深度大於100m土層之沉陷量仍較深度100m內土層來的大，故有必要探討深層土層之壓密回脹特性。由於台78線快速道路與台灣高鐵等重大交通運輸路線位於該下陷區內，若能掌握附近地層之壓縮回脹特性，則可對雲林地區地層之沉陷行為有進一步了解。壓密試驗結果顯示，深度大於100m黏土層之壓縮指數與100m內相差1.5-2倍，砂土層雖然整體而言壓縮指數較黏土層來的小，但深度100m至300m砂土層之壓縮指數仍比100m內來的大，其中30m至100m間有一段最小值。以上結果皆與STA-9測沉磁環之監測結果相符，且雲林地區目前地層下陷主要集中於深度大於100m的土層，深度158.2m至219.5m黏土層最為嚴重，淺層土壤則因壓縮性較低，影響僅限於局部範圍。

關鍵字

大深度壓密試驗 ； 壓密沉陷 ； 現代沖積層 ； 雲林

並列摘要

The settlement of Yuanchang Village, Tuku Township, and other inland areas of Yunlin County are majorly caused by the consolidation of soil layers over 150m deep, which takes about two-third of the overall settlement amount. From historical magnet extensometer monitoring reports, it can be seen that even the thickness of two soil layers are about the same, the settlement amount of the soil layer over 100m deep is still larger than the one within 100m deep. Hence, it is necessary to explore the compression-swelling characteristic of deep soil layer. Since Taiwan Highway 78 and THSR (Taiwan High Speed Rail) locate at such settlement area, if the compression-swelling characteristic of the nearby layer can be managed, the ground settlements in Yunlin area can be understood. Experimental result indicates that the compression index of clay layer over 100m deep is 1.5-2 times more than clay layer within 100m deep. The clay layer adjacent to the depth of 158.2m and 219.5m is a soil layer with the severest settlement. Though the compression index of sand layer is generally smaller than clay layer, however, the compression index of the sand layer at the depth from 100m to 300m is still larger than the sand layer within the depth of 100m, and there is a minimum from 30m to 100m. The experimental result complies with the monitoring result of STA-9 magnetic extensometer, which shows that the settlement is still mainly caused by excessive underground water withdrawal in the depth, and the settlement concentrates in the soil layer over 100m deep, while the settlement of shallow layer is limited to partial areas.

並列關鍵字

large-depth consolidation test ； consolidated settlement ； modern alluvium ； Yunlin