基于能量法的尾粉土累积应变增长方式研究

Energy-based method for analyzing accumulative plastic strain growth of tailing silt

为了研究累积塑性应变增长方式与能量耗散的关系,从机理方面进一步细化累积塑性应变增长方式。基于饱和尾粉土在3种孔隙比条件下不同循环应力比的固结不排水循环剪切试验,改进传统能量耗散计算方法,依据塑性应变累积能量耗散与黏滞累积能量耗散的关系对累积塑性应变增长方式进行了重新分类,并从能量耗散机理上阐述累积塑性应变的开展。研究结果表明:随着循环应力比增大,黏滞累积能量耗散速率将逐渐超越塑性应变累积能量耗散速率。将累积塑性应变增长形式细分为4类:稳定型、稳定破坏型、破坏型、和崩塌型。同时认为塑性应变累积能量耗散的产生是由于砂粒、粉粒等较大颗粒发生颗粒重排,而黏滞累积能量耗散的产生是由于黏粒、胶粒等较小颗粒间双电离子层内弱结合水发生脱离,粒间发生相对滑移。上述能量耗散机理与建立的累积塑性应变增长方式分类相一致,为进一步研究累积塑性应变模型提供研究基础。

In order to study the relationship between the accumulative plastic strain growth and the energy dissipation,and to further classify the pattern of the accumulative plastic strain growth,dynamic consolidated-undrained triaxial shear tests are conducted on tailing silts with different void ratios under different cyclic stress ratios.The energy dissipation in soil is divided into plastic strain and viscous accumulative energy dissipations.According to the relationships,failure modes of the accumulative plastic strain growth are reclassified,and the development of accumulative plastic strain is interpreted based on the improved energy dissipation mechanism.The research highlights that as the cyclic stress ratio keeps increasing,the rate of dissipation of viscous accumulative energy will exceed that of the plastic strain accumulative energy,and the development mode of accumulative plastic strain will turn from the stability to the failure.Furthermore,the failure modes are reasonably divided into four categories： stable type,stable damage type,damage type and collapse.Essentially,the plastic strain accumulative energy will dissipate due to the rearrangement among relatively large particles such as sand and silt grains.Similarly,the viscous accumulative energy will dissipate because of the relative slippage among clay particles and colloid particles under the relaxation of weak bound water in the double electrical layers.This energy dissipation mechanism is consistent with the proposed failure pattern of the accumulative plastic strain growth.The research results may provide a basis for further model researches on the accumulative plastic strain growth.