A Freezing-Thawing Damage Characterization Method for Highway Subgrade in Seasonally Frozen Regions Based on Thermal-Hydraulic-Mechanical Coupling Model

Qingsong Deng,Chao Zeng,Xianzhi He,Xiao Liu,Fengguang Chen,Siyu Zhang

doi:10.3390/s21186251

Abstract

Seasonally frozen soil where uneven freeze–thaw damage is a major cause of highway deterioration has attracted increased attention in China with the rapid development of infrastructure projects. Based on Darcy’s law of unsaturated soil seepage and heat conduction, the thermal–hydraulic–mechanical (THM) coupling model is established considering a variety of effects (i.e., ice–water phase transition, convective heat transfer, and ice blocking effect), and then the numerical solution of thermal–hydraulic fields of subgrade can be obtained. Then, a new concept, namely degree of freeze–thaw damage, is proposed by using the standard deviation of the ice content of subgrade during the annual freeze–thaw cycle. To analyze the freeze–thaw characteristics of highway subgrade, the model is applied in the monitored section of the Golmud to Nagqu portion of China National Highway G109. The results show that: (1) The hydrothermal field of subgrade has an obvious sunny–shady slopes effect, and its transverse distribution is not symmetrical; (2) the freeze–thaw damage area of subgrade obviously decreased under the insulation board measure; (3) under the combined anti-frost measures, the maximum frost heave amount of subgrade is significantly reduced. This study will provide references for the design of highway subgrades in seasonally frozen soil areas.

Highlights

Frozen soil is a kind of soil containing ice at temperatures below 0 ◦C
In the process of cyclical freeze–thaw of subgrade due to periodic temperature changes, the road pavement located in seasonally frozen areas is susceptible to damage, which poses a great threat to the safety of highway transportation [6,7]
The purpose of this study is to put forward a methodology based on actual cases, and to provide references for the design of highway subgrades in a seasonally frozen regions

Summary

Introduction

Frozen soil is a kind of soil containing ice at temperatures below 0 ◦C. It can be di-vided into permafrost and seasonally frozen soil if a seasonal freezing period exists. In the process of cyclical freeze–thaw of subgrade due to periodic temperature changes, the road pavement located in seasonally frozen areas is susceptible to damage, which poses a great threat to the safety of highway transportation [6,7]. The heat transfer, moisture migration, and phase change all interact during the freeze–thaw process This coupling effect is an important cause of subgrade freeze–thaw damage [8,9,10,11,12,13]. In order to effectively control subgrade damage and maintain the long-term safety of the highway in seasonally frozen regions, it is necessary to study the coupling mechanism of physical fields inside frozen soil, and to reveal the freeze–thaw law of subgrade in seasonally frozen soil areas

Objectives

Methods

Results