纤维加筋膨胀土的蠕变规律及模型预测

Creep law and model prediction of fiber-reinforced expansive soil

膨胀土是具有流变性质的灾害性土,其蠕变行为直接影响到工程结构的稳定性和安全性。为探究剑麻纤维加筋膨胀土的蠕变特性及应力-应变数学模型,采用室内固结排水三轴蠕变试验,分别进行了不同含水率、不同围压和不同偏应力条件下素膨胀土和剑麻纤维加筋膨胀土的蠕变特性研究,根据蠕变特征曲线提出了基于Mesri蠕变经验模型的剑麻纤维加筋膨胀土的修正蠕变模型。结果表明:相同条件下,剑麻纤维加筋土的蠕变变形量明显小于素土的蠕变变形量,说明掺入剑麻纤维可有效提高膨胀土的结构性能和抗变形能力;素土和剑麻纤维加筋土的蠕变变形量随含水率增大而增大,而随围压的增大呈减小趋势;素土和剑麻纤维加筋土在受到偏应力时均会产生瞬时应变量和蠕变变形量,其蠕变变形量随偏应力的增大而增大;素土和加筋土的蠕变曲线分4个阶段,分别为弹性变形阶段、稳态蠕变阶段、衰减蠕变阶段和加速蠕变阶段;高偏应力下,基于传统Mesri蠕变经验模型的剑麻纤维加筋土蠕变预测误差高达37.95%,对Mesri蠕变经验模型进行修正后预测误差降至1.5%内,说明修正模型能较好地描述剑麻纤维加筋土的蠕变特性。此研究结果可为膨胀土工程提供理论参考。

Expansive soil is a disastrous soil with rheological properties,and its creep behavior directly affects the stability and safety of engineering structures.To investigate the creep characteristics and stress-strain mathematical model of sisal fiber-reinforced expansive soil,the creep characteristics of expansive soil and sisal fiber-reinforced expansive soil under different water content,confining pressure,and deviator stress conditions were studied using laboratory triaxial creep test of consolidated drainage,and a modified creep model of sisal fiber-reinforced expansive soil based on Mesri creep empirical model was proposed with the creep characteristic curves in view.The results show that under the same conditions,the creep deformation of sisal fiber-reinforced soil is significantly smaller than that of soil without being reinforced,indicating that adding sisal fiber can effectively improve the structural performance and deformation resistance of expansive soil.The creep deformation of soil without being reinforced and reinforced-soil increases with the increase of water content,while decreases with the increase of confining pressure.Both soils could generate instantaneous strain and creep deformation when subjected to deviatoric stress,and their creep deformation increases with the increase of deviatoric stress.The creep curves of plain soil and reinforced-soil are divided into four stages,elastic deformation stage,steady creep stage,attenuation creep stage and accelerated creep stage.Under high deviational stress,the creep prediction error of sisal fiber-reinforced soil based on traditional Mesri creep empirical model is as high as 37.95%.By modifying the Mesri creep empirical model,the prediction error decreases to within 1.5%,indicating that the modified model can better present the creep characteristics of sisal fiber-reinforced soil.The research results can provide theoretical reference for expansive soil engineering.