温度变化条件下路基盐渍土动应力-动应变响应规律研究

以青海西部某地区的路基盐渍土为研究对象,基于英国GDS动三轴试验系统,进行室内温度变化状态下的动三轴试验,研究其在不同温度、频率、围压下的动应力-动应变、动剪切模量等的变化规律。试验结果表明:在循环动荷载作用下,温度改变对试样的动应力-动应变关系影响显著,频率和围压次之;同一动应变幅值下,温度越低,动剪切模量(G_d)越大;频率和围压增加时,G_d同样增大,但围压对G_d的影响更为明显,其曲线发展趋势更为陡峭;最大动剪切模量(G_dmax)和最终剪应力幅值(τ_dult)在温度、围压不变,频率增大时,两者也都增大,G_dmax曲线为上凸形,τ_dult曲线在正温状态下为上凸形,在负温状态下为下凹形;频率、围压不变时,G_dmax和τ_dult随温度降低而增大,且0℃以上变化趋势较缓,0℃以下变化趋势较陡。使用一个温度修正系数对不同温度下的G_dmax进行修正,并得到修正系数的拟合函数,其在负温下的拐点在-4℃左右。

Study on the Dynamic Stress-Strain Response of Subgrade Saline Soil under Temperature Change Condition

Based on the British GDS dynamic triaxial test system and with reference to the subgrade saline soil in one area of Western Qinghai, the laboratory test of dynamic triaxial is conducted under temperature change condition to unveil the change rule of the dynamic stress-strain relation and dynamic shear modulus at different temperature, frequency and confining pressure. The experimental results show that under cyclic dynamic load, the influence of temperature change on the dynamic stress-strain relationship of the sample is significant, while frequency and confining pressure are secondary. At the same dynamic strain amplitude, the lower the temperature becomes, the bigger the dynamic shear modulus(G_d) gets. As frequency and confining pressure increase, G_d also gets increased; not only the effect of confining pressure is more obvious, but also the trend of its curve is steeper. Both the maximum dynamic shear modulus(G_(dmax)) and the final shear stress amplitude(τ_(dult)) increase, when temperature and confining pressure are constant and the frequency is increased, and the curve of G_(dmax) is convex. The curve of τ_(dult) is convex at positive temperature, and it is concave at negative temperature. G_(dmax) and τ_(dult) increase with the decrease of temperature when frequency and confining pressure are invariant. The trend of curve change is slower at the temperature above 0 ℃ and relatively steeper at the temperature below 0 ℃. A temperature correction coefficient is used to modify G_(dmax) at different temperature, and the fitting function of the correction coefficient is obtained. Its inflection point at negative temperature is about 4 ℃.