應變速率對等應變速率壓密行為之探討

Abstract

相較於加載增量壓密 (incremental loading consolidation) 試驗，等速率應變壓密 (constant rate of strain consolidation) 試驗具有較短之時間歷程，然而，在過去的文獻中，應變速率對等應變速率壓密行為的影響仍然尚不明確，以致對於等應變速率壓密試驗的可靠性和精確性仍存有疑慮。本研究針對內湖地區的薄管取樣試體進行一系列室內試驗，旨在探討等應變速率壓密試驗中，土壤試體在不同應變速率下土壤之應力應變曲線、水力傳導係數和壓密係數等壓密行為，並探討在加載完成後使用恆定載重階段消散超額孔隙水壓的必要性，再並分別以加載增量壓密試驗和三軸透水試驗對等應變速率壓密試驗之結果進行驗證，最後探討在何種應變速率下，等應變速率壓密試驗得到的壓密參數與加載增量壓密試驗所得的結果相近。 研究結果顯示，隨著應變速率的增加，土讓的應變量及水力傳導係數均隨之增加，兩者皆呈正比關係，而恆定載重階段設定對於試驗整體結果而言影響不大。此外，也透過三軸透水試驗的結果證實，在較慢的應變速率下，測得的水力傳導係數更符合實際情況。最後，比較加載增量壓密試驗和等應變速率壓密試驗的結果，發現較慢的應變速率所得結果與加載增量壓密試驗的結果更為接近。因此，本試驗結果認為，較慢的應變速率能夠更符合實際的壓密參數，故建議應變速率之選定標準需以達到瞬時應變函數和超額孔隙水壓力比的觸發標準為前提，並盡可能選擇較緩慢的速率。

Compared to incremental loading consolidation tests, constant rate of strain consolidation tests have a shorter duration. However, previous literature has not clarified the impact of strain rates on the behavior of constant rate of strain consolidation, leading to doubts about the reliability and accuracy of these tests. This study conducted a series of laboratory tests on thin walled sampler from the Neihu District to investigate the consolidation behavior of soil specimens under different strain rates in constant rate of strain consolidation tests. The study results show that as the strain rate increases, both the strain and the hydraulic conductivity of the increase, demonstrating a proportional relationship. The constant load phase setting has little impact on the overall test results. Additionally, triaxial permeability test results confirm that the measured hydraulic conductivity at lower strain rates is more consistent with actual conditions. Finally, comparing the results of incremental loading consolidation tests and constant rate of strain consolidation tests, it was found that results obtained at slower strain rates are closer to those of incremental loading consolidation tests. Therefore, this study concludes that slower strain rates are more representative of actual consolidation parameters. It is recommended that the selection of strain rates be The study aims to examine the stress-strain curves, hydraulic conductivity, and consolidation coefficients of soil, as well as the necessity of dissipating excess pore water pressure during the constant load phase after loading. The results of the constant rate of strain consolidation tests were verified using incremental loading consolidation tests and triaxial permeability tests. Finally, the study explored the strain rates at which the consolidation parameters obtained from constant rate of strain consolidation tests are similar to those obtained from incremental loading consolidation tests.Therefore, this study concludes that slower strain rates are more representative of actual consolidation parameters. It is recommended that the selection of strain rates be based on achieving the trigger standards of the transient strain function and excess pore water pressure ratio, and that slower rates be chosen whenever possible.