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Ionic soil stabilization additives can improve soil compactness and strength rapidly and efficiently by chemical reaction. In order to study the stabilization mechanism of the F1 ionic soil stabilization additive and the basic engineering properties of the stabilized soil, the basic physical parameters, CBR value, unconfined compressive strength, expansion characteristics, and microscopic pore structure characteristics of the loess before and after F1 stabilization were studied by using micro and macro testing methods. The results show that the high-energy H3O+ of F1 dissociated with water can exchange with the metal cation and polar water molecule on the surface of clay particles, and neutralize the vacancy anion, so that the charged property, ion type, and concentration on the surface of stabilized soil particles can change. In F1, the sulfonated oil-coated soil particles form a hydrophobic oily layer, which reduces the plastic limit and optimal water content of the soil, increases the plastic index, and reduces the water sensitivity. The F1, through a series of physical and chemical effects, reduces the clay minerals’ surface electric potential and the electric double layer thickness of the water film; changes the pore structure and the form of contact between the soil particles; causes the soil particles through fine flocculation to join together into large particles; reduces the soil micro-pore area, the total number of pores, and the pore distribution fractal dimension, inhibiting the expansion deformation of the soil; increases the connection strength between the soil particles, the maximum dry density, and the CBR value; and makes the arrangement closer; a layer-stacked structure with more compact arrangement, larger aggregates, and surface-to-surface contact was formed under the action of compaction. F1 has many advantages that traditional soil stabilization additives do not have and has a broad application potential in soil reinforcement engineering in loess areas.

Frost jacking of electricity transmission tower (ETT) pile foundations in permafrost regions of the Qinghai–Tibet Plateau is becoming increasingly serious. This study investigated the effe...

The frost heave rate and stiffness of soil in frozen soil foundations varies remarkably with the freezing depth under the influence of the freezing-end temperature, temperature gradient, and overburden stress. The stress level of frozen soil increases with increasing frost penetration, leading to greater stiffness and a smaller frost heave rate. In this work, the freezing-end temperature and temperature gradient are introduced to the traditional Takashi model via the frost heave layering method and the overburden stress is modified to establish an empirical prediction model of frost heave rate and stiffness. Analytical solutions of load transfer differential equation of single pile considering stiffness increase and frost heave rate decrease along the frost penetration are derived on the basis of the mechanism of pile–soil interactions. The calculation results are in good agreement with measured values, thus confirming the correctness of the analytical solution. Variations in frost heave rate and soil stiffness with increasing depth are then combined to form four models, and changes in axial force and tangential frost heave force as a function of frost penetration are calculated and analyzed on the basis of these models. Results show that calculation of the frost heave rate and stiffness of soil along the frost penetration depth according to normal values will significantly underestimate the axial force of on the pile.