初始剪应力对外海回填土壤动态特性之影响

Initial shear stress effects on dynamic properties of reclaimed soil in offshore area

采用云林离岛工业区外海料源区土壤为试验用砂,考虑现有回填地之土壤条件,采用湿捣法制试样,探讨不同相对密度、有效围压应力及固结应力比等因素,进行一系列共振柱试验,以评估回填土於初始剪应力作用下之土动态特性。由试验结果分析得知,回填土壤之剪切模量有随固结应力比与有效围压应力之增加而增加之趋势,而最大剪切模量( Gmax) 亦随固结应力比与有效围压应力之增加而增加,同时不受初始相对密度不同之影响。另回填土壤因固结应力比所引致之最大剪切模量增量远大于孔隙变化所引致之增量。但固结应力比与有效围压应力对阻尼比之影响则较不明显。同时本研究在Hardin 与Richart(1963) 所建议之评估方式基础上进行修正,对云林外海土壤建立非等向压密条件下,最大剪切模量与不同剪应变所对应之剪切模式经验公式,可提供回填造地设计。

In this study, the reclaimed soil in Yun-Ling nearshore area was adopted as testing samples. Different relative densities and consolidation stress ratio were taken into consideration to prepare specimens by the moist tamping method. A series of resonant column triaxial test were performed, to discuss the shear modulus and damping ratio of the reclaimed soil under different intial shear stress and different consolidation stress ratios. In this study, different consolidation stress ratio were used to simulate the reclaimed soil under different initial shear stress. As shown in the test results, the shear modulus of the reclaimed soil increases as the consolidation stress ratio and mean effective confining pressure increase. Similarly, G max also increases as the consolidation stress ratio increases, but is not influenced by the different initial relative density. The increment of G max induced by consolidation stress ratio is larger than the increment induced by different viod ratios. The influence of consolidation stress ratio on damping ratio is not distinct. Summarizing all the analyzed results and based on the method suggested by Hardin and Richart (1963), a new method to evaluate maximum shear modulus and shear modulus under different shear strain for offshore reclaimed soil under anisotropic consoilidation is estabilished. The results in this paper can be provided for reference purposes during design, construction and dynamic analysis on land reclamation.