水力抽砂回填地層穩定度之分析

Abstract

本研究採用麥寮六輕基地回填地層土樣為試驗材料，進行大尺寸模型試驗，模擬靜置之回填地層受沿海潮汐作用下，所可能產生之脹縮情形，並探討回填地層滲透性與孔隙比的關係。根據試體之emax和emin及臺灣西岸潮汐變化之倩形分別擬定兩組不同洩升週期（分別為15分鐘及30分鐘）及各三種不同初孔隙比：0.7, 0.85及0.95，共六次模擬試驗。各次試驗模擬現場土層兩個月的歷時變化情形。 由試驗結果推得：洩升週期為30分鐘者（即模擬日單潮者），其土層壓縮係數△e/△10g(□)約介於-0.1至-0.05之間；並可得回脹係數約為0.05。洩升週期為15分鐘者（即模擬日雙潮者），其土層壓縮係數△e/△10g(□)約介於-0.09至-0.31之間。亦得滲透係數與孔隙比的關係式：10g(k)=5.541og(e)-3.0。另由結果發現：初孔隙比接近0.7之回填土層已有回脹發生，值得相關工程設計單位注意。

In this study, large scale models which simulates an under cultivation big- range hydraulic sand fill being affected by the tides are built by the filled material from Mai - Liao seaside. From the models, the possibility of expansion and compression, and the relationship between permeability and void ratio have been discussed. There are total 6 models divided into two groups! differing in tide - cycles (15 minutes and 30 minutes). Each group including 3 models differ in initial void ratio (0.7, 0.85 and 0.95). All models simulate the process of the reclamation of Mai - liao seaside during a period of two months. In consequence of the experiment of these models, it can be found that when the tide - cycle is 30 minutes (simulating once high tide a day), the compress index of the hydraulic sand fill is about 0.05 to 0.1; and the swell index is about 0.05. When the tide - cycle is 15 minutes (simulating twice high tide a day), the compress index is about 0.09 to 0.31. In addition, the function of the relationship between permeability and void ratio can be found as follows: 10g(k)=5.54．1og(e)-3.0 On the other hand, the result also shows that swelling happens in hydraulic sand fill when the void ratio of it is close to 0.7. It is worthy of pay attention to the situation.