温度静力触探的离散元模拟研究

Discrete element modelling of thermal penetration test with heating and cooling

^{Pin-Qiang Moa , Jing Hu b,*, Yu-Chen Hu c, Kuan-Jun Wang d, Abolfazl Eslami e, Liu Gaof}

a State Key Laboratory for GeoMechanics and Deep Underground Engineering, School of Mechanics and Civil Engineering, China University of Mining and Technology, No. 1, Daxue Road, Xuzhou, Jiangsu 221116, China

b State Key Laboratory for GeoMechanics and Deep Underground Engineering, China University of Mining and Technology, No. 1, Daxue Road, Xuzhou, Jiangsu 221116, China

c Zhaoxian Town People’s Government, Wanli Management Bureau, No. 10, Yunwan Road, Nanchang, Jiangxi 330004, China

d POWERCHINA Huadong Engineering Corporation Limited, No. 22, Chaowang Road, Hangzhou, Zhejiang 310014, China

e Department of Civil & Environmental Engineering, Amirkabir University of Technology, 424 Hafez Ave, Tehran, Iran

f School of Mechanics and Civil Engineering, China University of Mining and Technology, No.1, Daxue Road, Xuzhou, Jiangsu 221116, China

Abstract:A three-dimensional discrete element method (DEM) is employed to simulate thermal penetration tests with heating and cooling. This study investigates the mechanical behavior of soil particles during penetration, and examines the effects of temperature boundary condition, overburden load, and heating duration on the heat transfer mechanisms of the probe-soil system. Simulation results of penetration indicate that larger overburden load causes an increase in tip resistance (qc), sleeve friction (fs), and the isotropy of particles, whereas less influence is found on the distributions of penetration-induced displacement. Despite of the negligible effects of various temperature boundary conditions, the thermal responses of DEM model show that both the peak temperature of the probe heating module and the cooling rate of soil increase with the overburden load, while the probe insulation section shows a decreasing trend. The heat concentrates around the vicinity of the cone tip and probe shaft, and the high temperature area gradually expands with longer heating duration. Additionally, thermo-coupling analysis illustrates that the heat transfer process has a milder effect on the mechanical properties of granular soils. The numerical results are then validated against laboratory model chamber tests under comparable conditions, showing acceptable agreements.

Keywords: Thermal penetration test, Discrete element method, Heat response, Thermo-coupling analysis

Fig. 3. DEM model of thermal penetration test.

Fig. 6. Contact force chain maps along vertical cross-section in (a) to (c) and horizontal cross- section AA’ in (d) to (f) for simulations with different overburden loads.

Fig. 11. Soil temperature fields variation along vertical cross-section and horizontal cross-section BB’ for simulations with heating periods of (a) 60 s, (b) 120 s, and (c) 300 s and a cooling period of 180 s, where BB’ located at the depth of 36 mm (h/D_p = 6).

Fig. 17. Probe temperature versus time curves for different methods: (a) laboratory results at a depth of 5D_pl, (b) DEM simulation results with thermostatic boundary at a depth of 6D_p.