Why does ice content affect the strength of permafrost soil?

The ice content of permafrost is a critical factor in determining the ground's structural integrity and bearing strength. The relationship between ice and soil strength is primarily defined by the state of the ground moisture and the effects of thermal changes.12

When permafrost thaws, the melting of ground ice significantly reduces the soil's bearing capacity. This occurs because the transition of ice from a solid to a liquid state creates an excess of moisture within the active layer, resulting in a saturated, unstable soil structure that lacks the strength to support engineering works or agricultural use.23

Furthermore, the presence of ice makes the ground susceptible to frost action. During winter, the freezing of moisture causes upward displacement known as frost heaving, while in summer, the resulting excess moisture leads to a loss of soil strength. Because ice content—such as pore ice or segregated ice—can represent a large percentage of the ground volume, its melting can lead to significant surface subsidence and structural failure.213