Warm and ice-rich frozen soil (WIRFS) is a composite porous material consisting of a multiphase medium including mineral particles, ice, unfrozen water and air, which exhibits lower shear strength due to the weak binding forces between soil particles and ice crystals. 

To improve the stability of road embankments and bridge foundations in permafrost regions, scientists tried various measures to enhance the strength of WIRFS. 

Recently, a research group from Northwest Institute of Eco-Environment and Resources (NIEER) of the Chinese Academy of Sciences investigated the microscopic pore distribution characteristics and the macro-mechanical properties of WIRFS, to quantitatively analyze the relationship between laws of pore-size transformation and the strength of treated WIRFS. 

Scientists also used different soil stabilizers to strengthen the intensity of the WIRFS and observed the effects of different soil stabilizers on the WIRFS. 

The results reveal that the cement-based treatment of WIRFS can improve the cementation fill of soil pores and the bond forces between soil particles. 

There is an evident correlation between the microstructure characteristics and the mechanical properties of the treated WIRFS. 

As the fractal dimensions of pore-area decrease, the unconfined compressive strength of cement-treated WIRFS increases significantly. 

In contrast, as the fractal dimensions of pore-volume increases, the unconfined compressive strength decreases remarkably. 

The main object of this study is to reveal the relationship between compressive strength and micro-structures for the stabilized WIRFS. 

The study entitled "Microstructure and strength features of warm and ice-rich frozen soil treated with high-performance cements" was published in Journal of Mountain Science. 

 Preparation of mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM) test samples using the freeze-drying method. (a) freeze drier; (b) SEM samples. (Image by ZHANG Jianming)