饱和砂-黏及砂-粉-黏混合土动孔压特性

Dynamic pore water pressure characteristics of saturated sand-clay and sand-silt-clay mixtures

含细粒砂土在吹填土中广泛分布,其在长期服役过程中可能经受波浪及车辆荷载的循环作用,掌握含细粒砂土动孔隙水压力的变化特性对于评价吹填土在循环荷载作用下的安全性及稳定性尤为重要。通过对饱和重塑砂-黏混合土及砂-粉-黏混合土开展室内固结不排水循环三轴试验,研究了不同黏粒含量、细粒含量、黏粉比和孔隙比下砂-黏混合土及砂-粉-黏混合土动孔压的发展特征。结合不同混合土内部颗粒赋存状态光学显微镜图像及颗粒赋存状态理论,揭示了黏粒含量、细粒含量、黏粉比和孔隙比对混合土动孔压发展的影响规律及影响机理。试验结果表明:对于砂骨架孔隙比与孔隙比恒定的砂-黏混合土来说,随着黏粒含量的增加,动孔压在振动后期的波动性增长趋势分别增强、减弱;对于砂-粉-黏混合土来说,随着细粒中粉粒含量增多(黏粒含量减少),FC=5%试样动孔压在振动后期的波动性增长趋势呈现非单调变化规律,不同孔隙比下FC=10%试样动孔压在振动后期的波动性增长趋势单调增强;提出了适用于砂-黏混合土以及砂-粉-黏混合土动孔压发展的Mod-Baziar模型,该模型不仅扩展了动孔压的预测范围,而且具有更高的预测精度,其可以更好反映动孔压的整体发展趋势以及孔压在振动后期的细节变化;当采用Mod-Baziar模型分别对不同孔隙比下的纯砂、砂-黏混合土以及砂-粉-黏混合土动孔压进行预测时,模型中各个参数的取值范围依次增大。初步分析认为上述试验结果是由不同颗粒间复杂的黏结、摩擦及填充作用所致。

The sand-fines mixtures are widely distributed in hydraulic fill soil and may be subjected to the cyclic action of wave and vehicle loads during their long-term service.It is very important to know the dynamic pore water pressure changing characteristics of the sand-fines mixtures for evaluating the safety and stability of hydraulic fill soil under cyclic loading.The consolidated undrained cyclic triaxial tests are carried out on the saturated reconstituted sand-clay and sand-silt-clay mixtures to investigate the development features of dynamic pore water pressure of mixed soil with different clay contents,fines contents,clay silt ratios and void ratios.By combining with the optical microscope images of soil particles and the theory of soil particles occurrence modes,the influence laws and mechanisms of clay content,fines content,clay silt ratio and void ratio on the dynamic pore water pressure of mixed soils are revealed.It is find that for the sand-clay mixtures(constant e and constant es),with the increasing clay contents,the fluctuation growth trend of dynamic pore water pressure at the later stage of vibration increases and weakens respectively.For the sand-silt-clay mixtures,with the increasing silt contents(decreasing clay contents),the fluctuation growth trend of the dynamic pore water pressure at the later stage of vibration of specimens with FC of 5%changes nonmonotonously.While the fluctuation growth trend of the dynamic pore water pressure at the later stage of vibration of specimens with FC of 10%increases monotonically under different void ratios.The Mod-Baziar model applied to the development of dynamic pore water pressure of sand-clay mixtures and sand-silt-clay mixtures is proposed,which extends the prediction range of dynamic pore water pressure and has higher prediction accuracy.The Mod-Baziar model can better reflect the overall development trend and detail change at the later stage of dynamic pore water pressure.By comparing the values of each parameter in the Mod-Baziar model,it is found that when the Mod-Baziar model is used to predict the dynamic pore water pressure of sand,sand-clay mixtures and sand-silt-clay mixtures with different void ratios respectively,the value range of each parameter in the model increases successively.The preliminary analysis suggests that the above results are attributed to the complex bonding,friction and filling between different particles.