K0狀態下低塑性粉質砂土原樣與重模試驗之液化行為 與動態特性比較

Study on Liquefaction Behaviors and Dynamic Properties of Undisturbed and Remolded Specimens of Low Plasticity Silty Sands under K0 Condition

闕慎佑(Shen-You Chueh)

指導教授 ： 陳皆儒

國立暨南國際大學/科技學院/土木工程學系/碩士(2010年)

https://doi.org/10.6837/NCNU.2010.00171

摘要

在集集地震時，台灣中西部平原厚層粉土質細砂發生廣泛液化之行為，若使用現有簡易法來評估此區液化潛能，常常因細粒料含量修正與不同的現地試驗而產生不同的結論。由於土壤取樣存在著試體擾動的問題，所以室內實驗多以重模試驗進行。但高細粒料含量之粉土質細砂，受到顆粒排列與組成結構的影響，導致不同的重模試體準備方法，在相同的試驗條件下可能產生顯著不同的試驗結果，因此細粒料含量對室內試驗所得砂土強度的影響至今尚未有明確的定論。本研究於台南歸仁以Gel push取得低擾動薄管土樣，進行K 0狀態不排水單剪液化試驗，以求取現地土壤液化阻抗與動態參數，並以濕夯法製作重模試體，根據試驗結果歸納低擾動與重模土樣其液化行為與土壤動態特性之差異性。根據液化試驗結果，重模與低擾動現地土樣其土壤剪應變累積模式與孔隙水壓激發狀況有明顯的差異，但是兩者之抗液化強度並無顯著差距，且現地與重模土樣有著相似的剪力波速特性以及土壤動態特性。試驗結果顯示高細粒料含量之粉土質細砂其試體擾動對於土壤液化與動態特性之影響有限。

關鍵字

粉土質細砂 ； 現地土樣試驗 ； 土壤抗液化強度 ； 體積應變量 ； 剪力波速 ； 反覆單剪

並列摘要

The 1999 Chi-Chi earthquake caused extensive soil liquefaction in the western of Taiwan. Soil deposits in this area had more then 50% fines (soil particles passing #200 sieve). Using the simplified procedure to estimate liquefaction potential could induce different conclusions because of the fines content adjustment and in-situ test methods to use. It is difficult to obtain undisturbed soil sampling, studies used remolded specimens. Because of the effects of soil fabric, testing results on remolded silty sand specimens under similar void ratio and stress state vary with different specimen preparation methods. This study used the cyclic simple shear tests capable of maintaining K0 condition to investigate the liquefaction resistance, shear modulus, shear strain and post-liquefaction volume change of undisturbed and remolded samples. The undisturbed samples were collected in Kueiren area near Tainan city.
Based on test results, different pore pressure generation patterns have been observed between undisturbed and remolded specimens. However, variations in liquefaction resistance and dynamic soil properties between the undisturbed and remolded specimens are insignificant. As a result, it is concluded that effects of sample disturbance is limited in liquefaction characteristics and dynamic soil properties for silty sand with high fines content in southern Taiwan.

並列關鍵字

Undisturbed Samples ； Liquefaction Resistance ； Volumetric Strain ； Shear Wave Velocity ； Cyclic Simple Shear

參考文獻

Abbiss, C. P., 1981, “Shear Wave Measurement of the Elasticity of Ground,” Geotechnique, Vol.31, No.1, pp.94-104.

ASTM D 5311-92, “Standard Test Method for Load Controlled Cyclic Triaxial Strength of Soil,” American Society of Testing and Materials, West Conshohocken, PA, USA.

ASTM D 6528-00, “Standard Test Method for Consolidated Undrained Direct Simple Shear Testing of Cohesive Soils,” American Society of Testing and Materials, West Conshohocken, PA, USA.

Andrus, R. D., and Stokoe, K. H., (2000), “Liquefaction resistance of soils from shear-wave velocity,” Journal of geotechnical and geoenvironmental engineering, Vol. 126, No., 11, pp. 1015-1025.

Chang, W. J. and Hong, M. L. (2008), “Effects of Clay Content on Liquefaction Characteristics of Gap-Graded Clayey Sands,” Soils and Foundations, Vol. 48/1, (In press)