Dynamic Development Law of Expansive Soil Cracks Under Environmental Influence

Crack propagation tests are conducted on expansive soil under various temperature (15 °C, 20 °C, 25 °C, and 30 °C) and relative humidity (31%, 43%, 52%, and 67%) conditions. An innovative method for determining the volumetric crack rate is proposed, and the following conclusions are drawn. (1) The rate of water evaporation in soil samples plays a decisive role in the expansion of apparent cracks in expansive soil. (2) The higher the environmental temperature is, the higher the cracking water content and the lower the stable water content. When the environmental humidity is high, the lower the cracking moisture content is, the higher the stable moisture content. (3) There is a unified law for the expansion of apparent cracks in expansive soil under different environmental factors. The variations in the plane crack rate over time under different conditions are found to conform to the logistic law. (4) The volumetric fracture rate is a key indicator that comprehensively reflects the degree of fracture development. With increasing environmental temperature, the fracture volume increases from 9 to 11%. With increasing environmental humidity, the fracture volume decreases from 10 to 7.5%. (5) When the evaporation of water and the exchange of air reach equilibrium, the moisture stress in the soil is balanced, and the cracks expand to a stable state.