饱和土排水蠕变特性对比研究

Comparative Studies of Creep Characteristics of Saturated Soils at Drained k_0 Consolidation

利用室内改装的应力控制式三轴仪,以淤泥土、粉土、粉细砂(中密、密实)为研究对象,通过k_0固结三轴排水蠕变试验探讨了饱和土的排水蠕变特性.3种土样轴向蠕变规律均为稳定衰减型,但粉细砂的轴向蠕变与密实度有一定关联.3种土样体变规律存在一定差异性,淤泥土的体变随时间呈现剪缩与剪胀交替性,而粉土整体剪缩.砂土体变随时间变化则受围压和密实度的影响较大,体变总体呈剪胀性状,且砂越密实,受剪时围压越低,越易发生剪胀.3种土体蠕变系数与应力水平密切相关,均随应力水平增大而增大,而与围压值关系不大.但这种增长关系,对于黏性土(淤泥土、粉土)基本呈直线关系,而粉细砂并不呈线性,用指数增长关系描述更合适.最后,采用Merchant和Burgers蠕变模型拟合试验数据,发现应力水平S<0.8时两个蠕变模型均能达到较好拟合效果,S>0.8时均存在弊端有待进一步修正.

The triaxial drainage creep characteristics of saturated soils including oozy soil and silty soil and silty-fine sand （middle dense sand, dense sand ） were studied by triaxial k0- consolidation drainage creep tests using the interior refitting stress control triaxial apparatus. The three types soils＇ axial creep consistently present a steadily degenerative creep property, except silty-fine sand＇ s axial creep has certain correlation with relative dense degree. The volume strains＇ creep law exists some differences of these three kinds of soils. The oozy soil＇ s volume strain presents alternation characteristics between shearing shrinkage and shearing dilatancy along with time extension. The silty soil＇ s volume creep law is entirety sheared shrinkage change . Silty-fine sand＇s is sheared dilatancy more often than cohesive soil. From volume curve with time shows that, its creep law is obviously affected by confining pressure and relative dense degree. The lower the confining pressure is and the denser it is, the sample For cohesive soil （oozy soil and silt soil） the increasing curve is a straight line;For silty-fine sand （middle dense sand and dense sand） the increasing curve can be fitted by an exponential function. Finally two theoretical creep model of Merchant and Burgers are used to fitting the experimental data. It is concluded that when the deviatoric stress level is lower than 0. 8, they both achieve a good fitting, however when it is larger than 0. 8, they both have drawbacks and need some further revision.