基于离散元法的温度静力触探贯入与传热研究

Penetration and Heat Transfer of T-CPT based on DEM Simulation

温度静力触探是一种新型原位测试方法,可同时获取土体的力学和热学参数,为浅层地温能资源勘查提供技术保障。为研究温度静力触探的贯入与传热机理,通过离散元数值模拟实现了离散元模型的建立和试样的力学和热学参数标定。研究分析了贯入过程中的贯入阻力变化、土体应力场、位移场及位移路径;获得了加热-散热过程中探头加热段与隔热段的温度响应规律以及土体温度场演化,并与室内模型试验进行了对比分析。采集的温度变化曲线通过数据解译反演得到了土体的导热系数,为温度静力触探的贯入-传热机理研究及工程应用奠定了理论依据。研究结果表明:贯入过程中,贯入阻力随深度的增加而增加,且土体颗粒位移范围在距锥身B/2内;传热过程中,探头加热60 s,加热段实现了5.5℃的升温;在加热和散热的初期,探头的温度变化最快,与实验结果相同;利用探头散热温度所反演导热系数为0.330 W/(m·K),误差为6.5%,优于加热数据反演结果。

Thermal cone penetration test(T-CPT)is a new type of in-situ testing method,for obtain-ing both mechanical and thermal properties of soil layers,providing technical support for shallow geo-thermal resources exploration.To study the penetration and heat transfer mechanism of T-CPT,the numerical simulation is conducted in this study by establishing a model based on the discrete element method(DEM),followed by calibration of mechanical and thermal parameters of the soil sample.Penetration resistance,soil distributions of stresses and displacement are analyzed during the penetra-tion process.The thermal responses of heating and insulation sections are obtained in the following heating and cooling processes,as well as the evolution of the temperature field in the surrounding soil.Furthermore,the numerical results are compared with the laboratory model test.The measured tem-perature curves are then used to interpret soil thermal conductivity.It provides a theoretical basis for in-sights into the mechanisms of penetration and heat transfer of T-CPT and its implications in geotechni-cal engineering.The results show that the penetration resistance increases with the increase of depth in the process of the penetration,and the soil particle displacement range is within B/2 of the cone.Dur-ing the heat transfer process,the probe is heated for 60 seconds,and the heating section achieves a heating of 5.5°C.In the early stages of heating and dissipation,the temperature of the probe changes the fastest,which is the same as in the experimental results.The thermal conductivity of the inversion using the heat dissipation temperature of the probe is 0.330 W/(m·K),and the error is 6.5%,which is better than the heating data inversion result.