水泥稳定碎石基层的弹塑性特性

Elastoplastic Characteristics of Cement-stabilized Aggregate Bases

为了认识水泥稳定碎石基层的弹黏塑性特性,优化路面结构的设计计算,选用路面常用的骨架密实和悬浮密实2种水泥稳定碎石基层材料,振动压实成型了Φ150×150 mm标准圆柱体试件,应用微机控制万能试验机,设定不同加载速率(0.5,1,1.5,2,4 mm·min^(-1)),进行简单加载、循环加卸载、抗压回弹模量、徐变和松弛等试验,测试试件的应力-应变及其随时间的变化,分析强度、刚度、徐变与松弛等变化规律及加卸载应力-应变特性,研究水泥稳定碎石基层的弹塑性特性,提出改进型本构模型。结果表明:加载速率对试验结果的总体影响小于4.4%(相对误差),且60 min的徐变变形最大为0.03%,14 min的应力松弛最大为6.9%,表明水泥稳定碎石基层的黏性极弱,可以忽略不计;每次加载卸载后均有回弹变形和永久变形出现,反映了水泥稳定碎石基层的弹塑性性质,且服从有应力强化的弹塑性固体模型,可以用广义圣维南模型模拟分析;提出的改进型邓肯-张本构模型数值模拟具有很好的有效性,可以用来分析水泥稳定碎石的应力-应变曲线;0.4σ_(max)(σ_(max)为水稳碎石混合料的破坏强度)对应的割线模量十分接近传统的回弹模量,说明简化的0.4σ_(max)取值法可以用来测试水泥稳定碎石基层的回弹模量;从总体路用技术性能来看,骨架密实型的水泥稳定碎石基层要优于悬浮密实型。

In order to determine the visco-elastoplastic properties of cement-stabilized aggregate base and optimize the calculation of pavement structure design,two common types of cement stabilized aggregates base materials(skeleton-dense and suspend-dense structure)were selected to mold standard cylinder specimens(Φ150×150 mm)by vibration compaction.By applying a microcomputer-controlled testing machine at different loading rates(0.5,1,1.5,2,and 4 mm·min-1 respectively),simple loading,repeated loading and unloading,resilient modulus by compression,creep and relaxation tests were conduced to determine the specimen’s stress and strain,and their variations over time.Change rules for strength,stiffness,creep and relaxation,and loading-unloading stress-strain characteristic of cement-stabilized aggregate base materials were analyzed,Further,the elastoplastic properties were studied and a modified constitutive model was proposed.The results show that the overall impact of loading rate on the test results is less than 4.4%(relative error),and the maximum value of 60-minutes creep deformation is 0.03%,and the 14 minute stress relaxation effect is less than 6.9%,this indicates that the viscosity of cement stabilized aggregate bases is very weak and thus negligible.There is always resilient and permanent deformations after each loading-unloading,which reflects the elastoplastic properties of cement-stabilized aggregate bases,this can be analyzed by an elastoplastic solid model with stress hardening,and simulated by the generalized Saint-Venant model.The modified Duncan-Chang constitutive model proposed in this paper is very effective for numerical simulation and can be used to analyze the stress-strain curve of the cement-stabilized aggregates.The secant modulus value corresponding to 0.4σmax is very close to the traditional resilient modulus value,which shows that the simplified 0.4σmax measurement method can be applied to determine the resilient modulus.Considering overall pavement technical performance,the skeleton-dense type of cement-stabilized aggregate base is better than the suspended-dense type.