A sophisticated new computer study attests to the effectiveness of soil filters in protecting dam structures from earthquake damage.

For over half a century, civil engineers have employed soil filters to shore up the strength of dam structures in the wake of earthquakes.

The soil filters are comprised of grains which are larger and coarser than those of the earth which fills the dam's core structure, and serve to prevent those finer soils from eroding or escaping when cracks are created by seismic events. This in turn reduces the likelihood of a dam failure by reducing the ingress and passage of water.

While soil filters have been in usage for nearly two generations, design standards for their deployment have relied solely on experimental studies, and engineers have thus far refrained from using computer modelling to determine their effectiveness.

The efficacy of the soil filter method has now finally been proven by a sophisticated computer study conducted by the Lawrence Livermore National Laboratory (LLNL) and the Engineer Research and Development Center (ERDC) of the US Army Corps.

The study performed a detailed three-dimensional computer simulation of the way soil filters interact with the erosion process to ensure the dam structure retains its strength, and examined the behaviour of the soil filters at a granular level in order to determine their effectiveness based on first principles.

The research concluded that the method is indeed an effective means of shoring up the structural strength of dams when current standards for soil filters are applied, thus validating more than fifty years of real world practice.

Experimental tests were also run by the EDRC to substantiate the findings of the computer simulations, using the world's most powerful centrifuge at the Centrifuge Research Centre and a one-foot scale model of a 30-foot high dam, as well as glass beads of varying sizes to simulate soil filters and the clay core of the dam structure. These experiments generated data which served to further validate the findings of the computer simulations.

In addition to vindicating the use of soil filters, the computer simulations can also help to devise better earthquake-proofing arrangements by predicting the interaction between a dam's concrete and embankment sections with the soil filters in the case of seismic disturbances.