纤维加筋膨胀土的三轴蠕变特性试验研究

TRIAXIAL CREEP PROPERTIES OF FIBER REINFORCED EXPANSIVE SOIL

为了初步探究纤维加筋膨胀土的蠕变特性,采用室内非饱和三轴蠕变试验,分析了初始含水率和纤维掺量两个因素对玄武岩纤维加筋膨胀土蠕变特性的影响,通过等时应力-应变曲线得出加筋土的长期强度,并尝试建立了纤维加筋膨胀土的蠕变模型,得到的结论主要有以下几点:通过对比分级加载条件下的应变-时间曲线,发现纤维加筋对于减小膨胀土的蠕变变形有显著的作用,并存在最优纤维掺量,当纤维掺量超过最优纤维掺量,蠕变效应无显著改善;纤维加筋膨胀土的蠕变变形随着含水率的减小而减小,并存在最优含水率,当小于最优含水率时蠕变效应无明显改善;纤维加筋可以显著提高膨胀土的长期强度,纤维掺量分别为0.4%和0.6%的加筋土长期强度比相同条件下的素土分别提高了26.7%和23.3%;通过拟合,得到了Mesri蠕变模型参数,认为该模型从总体上可以反映纤维加筋膨胀土的三轴蠕变特性。

Studies on the properties and improvements of expansive soil have drawn more and more attentions because of many engineering accidents caused by deformation of expansive soil. In order to investigate the creep characteristics of fiber reinforced expansive soil, unsaturated triaxial creep tests are carried out with the consideration of the influence of water content and reinforcement ratio of basalt fiber mixed into the expansive soil.Long- term strength of the fiber reinforced expensive soil is analyzed through isochronous stress-strain curves.Meanwhile,Mesri creep model is established and verified. The main conclusions are as follows： By comparing strain-time curve,it finds that the fiber reinforced expansive soil has an obvious role on reducing creep deformation.However,there exists an optimal reinforcement rate. If fiber content surpasses the optimal reinforcement rate,the creep effect cannot be significantly decreased. The creep properties of the fiber reinforced expansive soil increase as the moisture content decreases. They have the optimum moisture content. If less than the optimum moisture content,the creep effect cannot be significantly increased. Isochronous stress-strain curves can be obtained from the straintime curve at different load levels. The long- term strength of the samples can be figured out according to the inflexion point of isochronous stress-strain curves. Long- term strength of expansive soil can be significantly improved by fiber reinforcement. In the test,the long-term strength of 0. 4%reinforced expansive soil is improved by26. 7%compared with pure soil under the same condition. The long-term strength of 0. 6%reinforced expansive soil is improved by 23. 3%. Mesri creep model can generally reflect the triaxial creep characteristics of fiber reinforced expansive soil.