橡胶砂应力-应变特性三轴-单剪联合试验研究

Stress-strain characteristics of rubber-sand mixtures in united triaxial shear and simple shear tests

橡胶砂作为一种环保的岩土材料有广泛的应用前景。应用三轴和单剪两种试验方法对2种固结压力下、7种配比橡胶砂的应力-应变特性、体变特性和模量衰减特性进行了对比研究,结果表明:随着橡胶颗粒含量的增加,橡胶砂模量降低,应力-应变曲线向应变硬化型转变,线性关系增强;随着橡胶颗粒含量的增加,橡胶砂剪胀特性减弱,剪缩增大;橡胶砂应力-应变关系可用扩展邓肯-张模型进行模拟,模型参数受橡胶颗粒含量影响的规律明显;随着橡胶颗粒含量的增加,橡胶砂的静剪切模量Gs与剪应变γ曲线降低,而橡胶砂模量衰减曲线Gs/G0-γ(G0为初始剪切模量)向大应变方向偏移;三轴和单剪两种试验方法得到的橡胶砂应力-应变特性、体应变-剪应变规律类似,但试验参数明显受应力状态和应力路径的影响,两者的差异主要表现为三轴试验得到的应力-应变曲线和模量曲线高于单剪试验,产生这种差异的主要原因是由于前者的平均应力相对较大。试验还得到了橡胶砂初始模量随橡胶颗粒含量降低的经验关系。

Rubber-sand mixture（RSM） has recently been demonstrated to be an environmental beneficial geotechnical material with wide application. The purpose of this paper is to investigate the stress-strain characteristics, volumetric properties and the modulus reduction properties of RSM. United tests combining triaxial shear and simple shear apparatus, in which 2 confining pressures and 7 rubber contents are considered, are conducted. Experimental results indicate that： with the increase of rubber content, the modulus of RSM decreases, and the stress-strain curves extend to strain hardening as well as the linearity of stress-strain relationship enhances. Volumetric expansion of RSM decreases and contraction increases with adding rubber to RSM. The behavior of stress-strain of RSM could be simulated well by extended Duncan-Chang hyperbola model, and the model parameters are evaluated with rubber content in RSM. With the increase of rubber content, the Gs-γ curves（where Gs is static shear modulus and γ is shear strain） of RSM decrease while the generalized Gs /G0-γ curves（where G0 is initial shear modulus） shifts toward to large strain domain. The stress-strain relationship and volumetric strain-shear strain relationship obtained from triaxial shear tests and simple shear tests are consistent and verified each other. The stress condition and stress path influence the experimental parameters. The stress-strain curve and modulus curve obtained from triaxial shear tests are higher than that from simple shear tests, which is possibly induced by higher mean stress in triaxial shear tests. An empirical relationship between the initial modulus of RSM and the reducing rubber content is proposed based on experiments.