基于能量耗散机制的粗粒土圆度损伤特性分析

圆度损伤是研究粗粒土力学特性变化的重要指标,为探索剪切过程中粗粒土圆度损伤的演化过程,定性及定量从能量角度对损伤本质进行分析。根据能量耗散原理,分析了剪切系统及单个颗粒剪切过程中能量的耗散与传递。结合弹塑性力学与热力学定律,定义粗粒土圆度损伤因子Dr,建立了基于能量耗散下的圆度损伤模型。采用剪切试验研究不同圆度的花岗岩和卵石颗粒的强度特性,以观测效果较好的花岗岩颗粒为研究对象,研究不同法向应力下的圆度损伤演化过程,运用MATLAB对模型及试验数据分析。结果表明:圆度不同的颗粒(花岗岩、卵石)随圆度减小,传递到颗粒内部积聚的塑性势能增大,更易在颗粒边界棱角处产生微裂纹使颗粒磨损,从而增大粗颗粒圆度,强度特性减小;剪切试验粗粒土圆度损伤演化过程存在2次损伤拐点,可分为圆度损伤响应、圆度损伤演化、圆度损伤稳定3个阶段;同一类型颗粒法向应力增大,达到损伤临界状态圆度损伤所需能量增大,圆度损伤因子减小。基于能量耗散下建立的圆度损伤模型阐述了剪切过程中的圆度损伤,试验结果能合理地反应圆度损伤演化过程中颗粒力学特性响应。

Analyses of roundness damage characteristics of coarse-grained soil based on energy dissipation mechanism

Roundness damage is an important index to study the change of mechanical properties of coarse-grained soil. In order to explore the evolution process of roundness damage of coarse-grained soil during shearing, the nature of damage is analyzed qualitatively and quantitatively from the energy point of view. According to the principle of energy dissipation, the dissipation and transmission of energy in the shearing system and individual particle shearing process are analyzed. Based on the elastoplastic mechanics and thermodynamic laws, the roundness damage factor Dr of coarse-grained soil is defined, and the roundness damage model based on energy dissipation is established. The shear strength test is used to study the strength characteristics of granite and pebble particles with different roundness. The granite particles with good observation effect are studied. The evolution process of roundness damage under different normal stresses is studied. The model and test data are analyzed by using MATLAB. The results show that the particles with different roundness (granite and pebbles) decrease with the roundness, and the plastic potential energy transmitted to the interior of the particles increases. It is easier to generate micro-cracks at the corners of the particles to wear the particles and increase the roundness of the coarse particles. The strength characteristics are reduced. There are two damage inflection points in the shear evolution process of coarse-grained soil roundness. It can be divided into three stages: roundness damage response, roundness damage evolution and roundness damage stability. The same type of particle normal stress increases, the energy required to achieve roundness damage in the critical state of damage increases, and the roundness damage factor decreases. Based on the roundness damage model established under energy dissipation, the roundness damage during the shearing process is described. The test results can reasonably reflect the mechanical response of the particle during the roundness damage evolution process.