软粘土边坡稳定性分析中十字板强度取值的探讨

DISCUSS ON SOFT SOIL STRENGTH FOR SLOPE STABILITY ANALYSIS BASED ON VANE SHEAR STRENGTH

土体强度指标的确定和选取是正确计算边坡稳定性的关键。对于欠固结、高灵敏度的软粘土地基,获取完全不扰动的土样进行室内试验是相当困难的,对此种软土地基通常采用十字板法来获得其强度指标进而进行边坡稳定性分析。但工程经验表明,由于土体强度具有摩擦特性和明显的各向异性,使得由十字板指标计算的边坡稳定性不能反映实际情况。考虑到上述因素,将十字板强度与土体的抗剪强度指标建立联系,采用经过修正的十字板强度指标进行边坡稳定性分析,通过对若干工程进行对比分析表明,该方法能够比较准确地反映工程的实际情况。

Tianjin New Harbor is covered with a soft clay layer of about 20 m thick. The vane shear testing is frequently performed to determine shear strength for slope stability analysis. However, even with the use of in-situ vane shear strength, the safety factors of stable slopes are often under estimated, suggesting that the in-situ vane shear strength may not represent the shear strength mobilized along the analyzed sliding surfaces. This study presented a method of converting in-situ vane shear strength into undrained shear strength parameters. The shear strength parameters determined for in-situ vane shear strengths were subjected to statistical regression analysis to take into consideration of the possible effect of non-homogeneity in the soft clay deposit. Using the regressed shear strength parameters, slope stability analyses were performed for five existing soil slopes. Based on the results of the study, it can be concluded that the presented method is effective to convert in-situ vane shear strength into undrained shear strength parameters for slope stability analysis.