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How does pore-water pressure fluidize material in a mud slide?

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landslide This 1995 landslide at La Conchita, a coastal town in California, swept away a hillside road and destroyed a number of houses.

In the context of a mud slide, material becomes fluidized when an increase in pore-water pressure significantly reduces the internal resistance of the soil or rock mass.1

When water saturates the pore spaces between soil grains, it exerts pressure that counteracts the forces holding the particles together. This process reduces interparticle friction and, in the case of clays, can lead to the dissolution of interparticle cements and the hydration of clay minerals. As the pore-water pressure rises, the individual grains or particles are pushed apart, allowing them to move freely within the watery matrix.12

This transition effectively lowers the material's shear strength, causing the mass to lose its solid structure and behave like a viscous fluid. Once the material reaches this state, it can flow downslope with high mobility, often resulting in the rapid movement characteristic of a mud slide.123