前海软土蠕变特性试验及模型参数研究
Creep characteristics and model parameters of Qianhai soft soil
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摘要: 为研究沿海地区软弱土层的蠕变特性并建立相应的蠕变模型,对深圳市城市轨道交通12号线海上田园东站处淤泥质黏土进行室内直剪蠕变试验。结果表明,该软土试样的蠕变特性与所受应力状态有关,在400 kPa固结压力下,当试样所受剪应力较小时,蠕变特性不显著,随着剪应力的提高,蠕变特性逐渐显著。根据蠕变速率将软土的蠕变过程区分为减速和稳定两个阶段,随着剪应力的提高,该软土在各蠕变阶段的时间均逐渐延长,相应的应变增量也逐渐增大。采用修正的Singh-Mitchell模型对该软土的蠕变特性进行建模,该模型参数少,本构方程简单,适用性较强。通过采用不同参考时间的试验数据对模型参数进行校核,发现当参考时间t1=1 h时模型计算结果与试验数据之间的误差最小,预测精度较高。Abstract: In order to explore the creep characteristics of the soft soil layer in coastal areas and establish the corresponding creep model, a direct shear creep test is conducted on the silty clay at the Haishangtianyuan East Station of Shenzhen Metro Line 12. The results show that the creep characteristics of the soft soil samples are related to the stress state. Under the consolidation pressure of 400 kPa, when the shear stress of the samples is small, the creep characteristics are not significant. With the increase of shear stress, the creep characteristics gradually become more significant. Using the creep rate, the creep process of the soft soil is divided into two stages: deceleration and stability stages. With the increase of shear stress, the elapsed time for each creep stage grows, and the corresponding strain increment increases gradually. The modified Singh-Mitchell model is used to simulate the creep characteristics of the soft soil. This model is widely used because it has fewer parameters and its constitutive equation is simple. The model parameters are calibrated using the test data at different reference time. It is found that the error between the calculated results and the test data is the smallest when the reference time t1=1 h, and the prediction accuracy is higher.