珠海海相软土次固结变形特性及其系数取值研究

Secondary consolidation deformation characteristics and coefficient selection of Zhuhai marine soft soil

次固结变形是导致深厚软土区基础设施过大工后沉降的重要原因,为研究珠海海相高含水率软土的次固结特性和次固结系数的变化规律,对珠海典型区域不同深度原状土样进行一维次固结压缩试验,分析固结压力、超固结比、不同加荷比对珠海软土次固结性状和次固结系数的影响。试验结果表明:次固结时程曲线呈反S型,同一土样累计次固结变形量约占总变形量的25%,在压缩变形过程中不可忽略;次固结系数随固结压力的增大先增大再减小最后趋于稳定,在固结压力200 kPa左右达到峰值;次固结系数随超固结比的增大呈非线性减小,超固结比越大,土体次固结系数减小的程度越大;次固结变形随加荷比的增大而增大,但最终固结沉降量由所加的最大荷载决定。将试验得到的珠海软土次固结系数与其他沿海地区软土次固结系数对比发现:珠三角软土次固结系数在0.015~0.02之间,大于长三角和天津地区软土次固结系数,其次固结特性相对长三角和天津地区的更明显。在试验结果的基础上结合已有文献中的试验数据,建立珠海软土次固结系数与压缩指数、天然含水率和塑性指数的线性经验公式。研究结果可为珠海地区软基处理合理设计和长期变形准确预测提供参考。

Secondary consolidation deformation is an important reason for excessive post construction settlement of infrastructure in deep soft soil area.In order to investigate the secondary consolidation characteristics and the variation of secondary consolidation coefficients of Zhuhai marine high water content soft soils,undisturbed soil samples at different depths in a typical area of Zhuhai were obtained.One-dimensional secondary consolidation compression tests were carried out to analyze the influence of consolidation pressure,over-consolidation ratio,and different loading ratio on secondary consolidation behavior and secondary consolidation coefficient of Zhuhai soft soil.The test results show that the secondary consolidation time history curve is a reverse S-shaped curve,and the cumulative secondary consolidation deformation of the same soil sample accounts for about 25%of the total deformation.This cannot be ignored in the process of compression deformation.The secondary consolidation coefficient first increases and then decreases as the consolidation pressure increases,and finally tends to be stable,reaching a peak value at about 200 kPa of consolidation pressure.The secondary consolidation coefficient decreases nonlinearly with the increase of the over-consolidation ratio.The larger the overconsolidation ratio,the greater the degree of the decrease in the secondary consolidation coefficient of the soil.The secondary consolidation deformation increases with the increase of the loading ratio,but the final consolidation settlement is determined by the maximum load applied.The comparison between the measured secondary consolidation coefficient of Zhuhai soft soil and the test results of soft soil in other coastal areas shows that the secondary consolidation coefficient of soft soil in the Pearl River Delta is ranged from 0.015 to 0.02,which is larger than those in Yangtze River Delta and Tianjin area.The secondary consolidation characteristics in pearl River Delta region is more obvious than that in the Yangtze River Delta and Tianjin.Combined with the test data in this article and the existing literature,a linear empirical formula for the secondary consolidation coefficient and compression index,natural moisture content and plasticity index of Zhuhai soft soil is established.The research results can provide references for the reasonable design of soft foundation treatment and the accurate prediction of long-term deformation in Zhuhai area.