循环荷载下发泡聚苯乙烯改良膨胀土动弹性模量与阻尼比试验研究

Experimental study of dynamic elastic modulus and damping ratio of improved expansive soil under cyclic loading by expanded polystyrene

发泡聚苯乙烯(expanded polystyrene,简称EPS)与膨胀土结合形成改良土,其可通过EPS的变形特性吸收膨胀能量,从而改善膨胀土胀缩性,并有优良的保温减振效果。通过GDS动三轴仪在不同围压、频率下进行分级动应力加载,研究不同条件下EPS改良膨胀土的动应力-应变、动弹性模量及阻尼特性。试验结果表明:EPS改良膨胀土的动应变、一次荷载循环下的能量损耗随着动应力增加呈非线性增加,而其动弹性模量随动应力增加而下降;频率增加使EPS改良膨胀土动应变减少,动弹性模量增加;围压增加使EPS改良膨胀土的动弹性模量呈先下降后上升趋势;不同频率下EPS改良膨胀土阻尼比-动应力曲线存在明显交汇点,其随围压提高向左偏移;在动应力幅值较小时,施加高频荷载将产生更大阻尼比,而动应力发展后期,低频加载则对应更大的阻尼比;相同频率条件下,改良土阻尼比随围压升高呈下降趋势。

Expansive soil combined with expanded polystyrene(EPS) can absorb expansive energy through deformation characteristics of EPS, improving swelling and shrinkage of expansive soil. The combination can also have excellent effect of heat preservation and vibration reduction. The dynamic stress-strain, dynamic elastic modulus and damping characteristics of EPS modified expansive soil under different conditions are studied by means of GDS dynamic triaxial instrument under different confining pressures and frequencies. The test results show that: 1)With the increase of dynamic stress, the dynamic strain and energy loss of EPS modified expansive soil increase non-linearly, while its dynamic elastic modulus decreases. 2) With the increase of frequency, the dynamic strain of EPS modified expansive soil decreases while the dynamic elastic modulus increases. 3) With the increase of confining pressure, the dynamic elastic modulus of EPS modified expansive soil decreases first and then increases. The damping ratio and dynamic stress curves of EPS modified expansive soil at different frequencies have obvious intersection points, which deviate to the left with the increase of confining pressure. When the amplitude of dynamic stress is small, applying high-frequency load will produce a larger damping ratio. In the later development period of dynamic stress, a larger damping ratio corresponds to a lower-frequency load. Under the condition of same frequency, the damping ratio of improved soil decreases with the increase of confining pressure.