軟弱黏土取樣過程所造成之擾動，改變了黏土原本結構，影響其力學性質，影響所及無法依現行一般試驗方法獲取應有之正確強度。過去一些深開挖工程，在循正常設計及施工條件下，卻依然發生失敗案例，檢討眾多災變原因之中，設計參數採用不正確黏土剪力強度是其中重大關鍵因素。因此本文針對取樣擾動對軟弱黏土強度之影響提出研究心得，除了根據學理探討擾動的現象與大小外，更根據實務工程設計需求提出簡易之分析方法。

　　由取樣擾動所衍生的後果加上現有常用的實驗室試驗，並無法有效修正黏土強度偏差。由過去的深開挖隆起破壞案例經驗指出取樣擾動及不當試驗方法導致黏土應有強度誤判。因此本文首先提出一簡易方法用於開挖隆起穩定分析中判斷現地黏土應有的強度。藉此，不但有效運用傳統試驗資料，維持原有工程分析有效便利以外，同時在實際應用上避免採用非常繁複的 試驗方法而可以繼續沿用慣用的試驗方法。

　　為達到有效運用傳統試驗方法的目的，必需藉由提昇試體品質，以獲取可靠試驗成果。因此，現階段有必要探討與試體品質相關之取樣試驗等擾動所造成的影響。由於泛稱擾動之成因不只一端，依個別影響性重要程度考量，本研究內容著重於對軟弱黏土影響最大之取樣貫入擾動上。

　　研究方法以黏土經歷之應變歷史與應變率做為薄管取樣擾動之評估指標。其中，理論方法採用流體動力學推演擾動應變理論，將黏土視為不可壓縮流體。數值方法則應用FLAC程式，解析取樣貫入過程之擾動應變，在分析過程中將土壤模擬為不可壓縮彈性材料，並據此與前項理論結果相互驗證比較。對於基本擾動行為特性而言，兩種研究方法獲致如下結論：(1)薄管取樣最大擾動應變約與取樣器厚徑比成正比；(2)取樣擾動應變率除隨厚徑比增加外，並隨著取樣之速度增大而增加；(3)取樣器刃口形狀影響擾動應變。對於實務工程而言，取樣薄管厚徑比過大、刃口截平及取樣速度過快時，容易導致黏土降伏改變強度，使得實驗結果產生偏差，誤判真實強度。進而錯估設計需求，影響工程安全。

　　降低取樣擾動最直接的方法，可藉由改進目前之取樣器達成。本研究參考各種取樣器之優點，提出一種兼顧工程及經濟價值之新型斜口式取樣器，藉數值試驗確認能有效降低擾動。

　　本文課題由實務問題而來，研究成果回饋於實務應用。透過細密的理論與數值研究過程，將心得以簡便實用的分析方法與取樣器呈現兩項具體成果，盼能改善工程應用上的困境，並緩和對黏土擾動問題的困惑。因此，提供適當的分析方法消弭取樣擾動所偏失的土壤強度，以及研發可以降低取樣擾動的取樣器，成為本文研究對於實際工程應用的兩項貢獻。

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