秸秆灰渣改良膨胀土三维膨胀特性试验研究

利用秸秆灰渣作为添加剂,进行室内改良膨胀土试验,研究改良后膨胀土的三维自由体变化特性及无侧限抗压强度特征。秸秆灰渣以(干质量之比)0%,10%,15%,20%的比例与素膨胀土混合进行击实试验,在最大干密度及最佳含水率条件下进行三维自由体膨胀、膨胀力和无侧限抗压强度3个试验,在液限状态下进行三维自由体收缩试验。根据三维自由体应变及膨胀压力特征,拟合出秸秆灰渣最佳含量的线性方程,得出灰渣的最佳含量为17%。试验结果表明:膨胀土的体应变、塑性指标和膨胀压力随着秸秆灰渣含量的增加而逐渐降低,无侧限抗压强度随着秸秆灰渣的增加逐渐提高;对未养护的试样,秸秆灰渣对无侧限抗压强度影响不明显,而试样养护7 d后的强度提高较为明显。

Experimental Research on Three-dimensional Swelling Characteristics of Expansive Soil Improved with Straw Ash

Laboratory tests were carried out on expansive soil improved with straw ash as additive to research the 3-D free volume change and unconfined compressive strength (UCS) characteristics of expansive soil improved with straw ash. Straw ash content (weight of straw ash/weight of dry soil) at 0%, 10%, 15% and 20% were mixed with expansive soil and then compacted. Tests on the 3-D free volumetric swell strain, vertical swell pressure and unconfined compressive strength were conducted in the presence of maximum dry density and optimum moisture content, and also tests on the volumetric shrinkage strain was conducted in liquid limit state. The linear equation of the optimum content of straw ash was fitted based on the 3-D free volumetric strain and swelling pressure properties of expansive soil, and the optimum content of straw ash was 17%. The test results show that with the increasing of straw ash, the volume strain, plasticity index and swell pressure decreased whereas the UCS increased. There is no remarkable change in the UCS of the samples immediately tested with straw ash, however, curing of 7 days could bring a remarkable increase in the UCS.