考虑变温幅值影响的颗粒循环热固结离散元法试验研究

Experimental research on discrete element method of particle cyclic thermal consolidation considering the influence of variable temperature amplitude

随着地下能源工程、热法地基处理和核废料处理等技术越来越多的开展,热力耦合对土体的影响已经成为当今岩土工程领域的热门研究课题之一。基于颗粒体积膨胀法,通过PFC^(2D)模拟不同变温幅值下(20、40、60℃)松散颗粒(相对密实度D_(r)=0.2)的循环热固结试验。在宏观角度上发现颗粒在温度循环过程中产生热固结现象,即试样随温度循环圈数的增加,其孔隙比不断累积降低。研究表明:变温幅值越大将导致长期温度循环过程中的颗粒材料越密实,且孔隙比、侧向应力和竖向应力的分布出现一定的不均匀性。与此同时,通过微观角度的分析,总结了温度循环和变温幅值对颗粒间接触数量、法向接触力和切向接触力所存在的影响,得出热固结试验中温度循环的幅值对试样的各向异性有较大的影响。

With the developments of geotechniques such as underground energy engineering,thermal foundation treatment,and nuclear waste treatment,the influence of thermo-mechanical coupling on soil has become one of the hot research topics in the field of geotechnical engineering.Based on the particle volume expansion method,the cyclic thermal consolidation experiment on loose particles(relative density D_(r)=0.2)at different temperature changes(20℃,40℃,and 60℃)is simulated by the PFC^(2D).From a macroscale point of view,it is found that the particles produce thermal consolidation during the temperature cycle,i.e.the process in which the void ratio of the sample cumulatively reduces as the number of temperature cycles increases.The studies have shown that the larger the amplitude of the temperature changes,the denser the granular material will be during the long-term temperature cycle,and the uneven distributions of void ratio,lateral stress,and vertical stress will appear.At the same time,the influences of temperature cycle and variable temperature amplitude on the number of contacts between particles,normal contact force,and tangential contact force are summarized by microscopic analysis.It is concluded that the amplitude of the temperature cycle in the thermal consolidation test has a greater impact on the anisotropy of the sample.