VertekCPT: All you need to know about Soil Liquefaction Sponsored

In continuation to the previous article about Soil Shear Strength, which was published in VertekCPT University Blog, today is highlighted another very important application of using CPT. This capability is the estimation of soil liquefaction potential, which is meaning the potential of soil to dramatically lose strength when subjected to changes in stress.

Liquefaction is of particular concern in sandy, saturated soils. Shaking due to an earthquake or other sudden force causes the grains of loosely packed, sandy soils to settle into a denser configuration. If the soil is saturated and the loading is rapid, pore water does not have time to move out of the way of settling soil: pore water pressure rises, effectively pushing the soil grains apart and allowing them to move more freely relative to each other. At this point, the soil can shift and flow like a liquid—hence the name liquefaction.

This dramatic reduction of soil stiffness and strength causes soil to shift under pre-existing forces—say, the pressure of a building’s foundation or the pull of gravity on a slope. The increased pore pressure also increases the force of the soil on in-ground structures such as retaining walls, dams, and bridge abutments.

How can the potential for these effects be evaluated using the CPT? The subject is complex, as the wealth of research on the subject over several decades shows! Many approaches for determining cyclic liquefaction potential rely on the cyclic stress ratio (CSR), which requires a seismic analysis of the site. It expresses the ratio of the average cyclic shear stress in an earthquake of a given magnitude and the effective vertical overburden stress at the test site.

Read the entire article where you will find more examples about Soil Liquefaction in VertekCPT University page!