非飽和土壤傍壓儀現地試驗

Abstract

由於現場試驗不易，非飽和力學特性之決定，大多根據現場取得土樣所進行室內非飽和試驗，以求得包括土壤保水特性曲線以及在不同基質吸力條件下之剪力強度等。然而土壤保水特性曲線會受到現地應力狀態、試體擾動、初始孔隙比、含水量等影響，利用現地試驗求取非飽和土壤強度可能為一更佳的選擇。本研究將一現有傍壓儀配合光纖光柵感測技術，使得傍壓儀之應變與壓力量測更為靈敏。在交通大學光復校區設定試驗場址，進行不同基質吸力情況下之現場傍壓儀試驗。本論文敘述傍壓儀之改良，傍壓儀儀器設備與現場試驗程序，最後用傍壓儀試驗結果配合非飽和土壤擴孔理論來詮釋力學特性。

Because the difficulties involved in field tests in unsaturated soils, we often perform laboratory tests on reconstituted soil samples to determine the mechanical properties of unsaturated soils, such as soil water characteristic curves and shear strength under various matric suctions. However, soil water characteristic curve can be affected by stress state, disturbance, initial void ratio, and moisture content, etc. Characterization of unsaturated soils in situ can be a more desirable approach. Taking advantage of the optic fiber Bragg grating sensing techniques, the author modified an existing pressuremeter to enhance the sensitivity of its strain and pressure measdurement capabilities. A test site was set up within the campus of National Chiao Tung University. A series of field pressuremeter tests were performed in unsaturated soils under various matric suctions. The thesis describes the modifiaction of the pressuremeter and the field test proceduree. The pressuremeter test results are interpreted according to cavity expansion theory considering the effects of matric suction.