以實驗方法探討非飽和含黏土粒料砂土之液化行為研究

Abstract

液化的發生是近年來時常探討的領域，然而，過往土壤液化行為的研究主要專注於飽和且土壤種類為砂土的條件下，對於非飽和的土壤甚至是含有黏土粒料的非飽和土壤並沒有太多的關注。為了瞭解非飽和砂土以及含有黏土粒料之非飽和砂土之液化行為，本研究利用GDS開發的動力三軸試驗儀進行一系列之非飽和含黏土粒料砂土之液化行為研究。不同飽和度、黏土粒料含量之試體在加載不同的循環應力之後可以計算得CSR以及LRR。另外，本研究亦利用令流量幫浦試驗得到土壤之SWCC曲線，即為土壤之土水特徵曲線，試體飽和度為利用抽出之水體積計算控制而得，在加載循環應力時，土壤試體之空氣壓力變化、孔隙水壓變化以及基質吸力變化都會被記錄。從結果得知，在試體中加入低於20％之黏土粒料將會使土壤之抗液化強度減少，降低試體之飽和度可以提昇其抗液化強度。當飽和度從100％下降至80％，含有黏土粒料之試體因減少飽和度所提升之抗液化強度相較於純砂試體為多。本研究所使用的實驗流程與改良之設備再經過一系列試驗結果觀察討論後可供後人進行非飽和土壤試驗之參考。

Tens of thousands of earthquakes occur in Taiwan annually. Occasionally, some of them can be catastrophic which would lead to severe damages to buildings and infrastructures, as well as human injuries and casualties. Liquefaction is one of the earthquake-induced hazards. In the past, most studies focused on the liquefaction behavior of saturated sands. However, there were studies which indicated that liquefaction of unsaturated sands is also possible. In this study, a series of cyclic triaxial tests were conducted on unsaturated sands with clayey fines. The effects of degree of saturation and fines content on liquefaction resistance were investigated. The specimens were controlled to a target degree of saturation by using the flow pump method. Based on the laboratory test results, adding clayey fines to sands would decrease the liquefaction resistance, while decreasing the degree of saturation would have an opposite effect. Compared to clean sand, the liquefaction resistance of sand-clay mixtures would have a larger increase when the saturation was decreased from 100% to 80%.