中文摘要：

砂-聚苯乙烯颗粒轻质填料由工程细砂和聚苯乙烯颗粒按一定比例混合形成，有利于节省胶凝材料、降低土工填料附加应力和减小地基沉降，探讨该材料的应力应变关系对指导其工程实践变得尤为重要。基于椭圆-抛物双屈服面模型，推导了考虑轻质填料配比和围压特征的应力应变增量形式方程，结合轻质填料三轴固结排水剪切试验中的应力应变特性，分析了所推导的应力应变增量形式方程的合理性。研究发现，基于椭圆-抛物双屈服面模型的考虑轻质填料配比和围压特征的应力应变增量形式方程能较好地拟合材料偏应力-轴向应变-体变规律，能较好地反映材料的弹塑性、剪胀性和剪缩性，并结合轻质填土的变形机理给予相应解释。

英文摘要：

Geomaterial, known as sand-expanded polystyrene （EPS） lightweight fill, is formed by blending EPS beads with standard fine sands at various ratios. The geomaterial has many merits, e.g., saving cementitious materials, mitigating additional loads and settlements. Researches on the stress-strain relationships of the geomaterial become important in guiding its field uses Based on the elliptic-parabolic yield surfaces model, the incremental stress-strain equations describing the stress-strain variations of materials are established. The equations consider the blending ratios and confining stresses of materials while depicting the mechanical behaviors of materials. Consolidated drained triaxial shear test results are used to analyze the reliability of the derived stress-strain equations. It is indicated that the equations well demonstrate the deviatoric stress-axial strain-volumetric strain variations of lightweight fills, meaning that the incremental stress-strain equations basically reflect the critical behaviors of materials, i.e. elastic-plasticity, dilatancy and contraction. Interpretation is advised from the perspective of the shear deformation of materials.