中主应力对砂土强度影响的细观机制研究

Meso-scale study of effects of intermediate principal stress on strength of sand

基于简化的颗粒单元体模型,分析总结了颗粒单元体的基本特点,针对中主应力对砂土强度的影响,重点分析了颗粒单元体之间的相互影响特点。对以往的真三轴试验结果进行了总结,得到了中主应力对砂土强度影响的规律,结合颗粒单元体的两种基本状态及其特点、大孔隙与颗粒单元体结构孔隙的特点以及颗粒单元体间相互影响的特点,揭示了中主应力对砂土强度影响规律的细观物理机制。这些规律包括:松砂的强度随着中主应力的增大是逐渐提高的;密砂随中主应力的增大,强度先提高,当中主应力接近大主应力时,却引起强度的降低;砂土越密实,强度平台段越长;在中主应力接近小主应力阶段,强度随中主应力的增大而提高的快慢与砂土的密实程度有关。

Based on the simplified model of the unit of particles, the basic principles and characteristics of the unit of particles were analyzed; and considering the deformation and strength of sand with the effect of intermediate stress, the interaction properties of the units of particles were discussed in detail. The effects of intermediate principal stress on the strength of sand were analyzed from the results of previous triaxial texts. Some macro features of the effect of intermediate stress on strength of sand were interpreted in view of meso-scale study through the analyses of the basic states and properties of the unit of particles, the features of macro-pore and unit pore, the interaction properties of the units of particles and relative physical mechanism. The macro features include that the strength of loose sand is improved gradually if the intermediate principal stress increases from the minor principal stress tY3 to the maximum principal stress σ1; but the strength of dense sand is improved at the beginning and reduced if the intermediate principal stress approach the maximum principal stress σ1; the segment of constant strength increases with the increase of sand density; the rate of strength improvement is effected by the initial ratio of sand if the intermediate principal stress is close to the minor principal stress σ3.