Pore microstructure and mechanical behaviour of frozen soils subjected to variable temperature

Mechanical behaviour of frozen soils is of great concern in the design and construction, and maintenance of the railways, highways, airports, pipelines, and other major infrastructure in cold regions. The micro-structural behaviour of the frozen soils such as porosity, particle morphology, arrangement pattern, contact connection, and particle trajectory can be susceptible to variable temperature. The paper investigates the microstructure characteristic and mechanical behaviour of the frozen soils caused by different temperature gradients. The soils differ in both water content (5% ∼ 20%) and temperature range (−15 °C ∼ 0 °C) under cold environment. The purpose of the study is to evaluate the mechanical behaviour of frozen soils based on a mathematical model and observe the microstructure behaviour using scanning electron microscopy (SEM) equipped with particles (pores) crack analysis system (PCAS). The mathematical model can well simulate the stress-strain relationship of frozen soils. The porosity of the frozen soils increases with the decrease of the temperature, and the distribution of the particles triggered by different temperature gradient. Furthermore, micro-structural behaviour has potential applications in micro- and macroscopic mechanical behaviour of the frozen soils in cold region engineering. •Pore microstructural characteristic of the frozen soils based on SEM is studied.•The distribution of pore microstructure is investigated under temperature rise.•Porosity, particle morphology, arrangement pattern, and contact forms of the frozen soils are discussed.•A new mathematical model is established to evaluate mechanical behaviour of frozen soils.