The Los Angeles Museum of the Holocaust needed a foundation improvement solution for its new and innovative earth-sheltered facility. Jon Irvine, the project engineer, of Irvine Geotechnical Inc., suggested using a mechanically stabilized earth (MSE) mattress as an affordable alternative to overexcavation and replacement.
Schedule, performance and cost were significant project drivers, but the overriding concern was the potential effects of total and differential settlement caused by subsurface conditions or seismic events. Any foundation approach would have to meet the project’s compaction requirement while also minimizing differential settlement.
A subsurface soil investigation revealed silty sand and clay soft soils (R value = 5).
Irvine Geotechnical developed a rigid foundation design using one layer of Tensar TriAx 160 Geogrid from Tensar International Corp. The MSE design provided a low-cost solution that could be installed quickly while delivering performance that was equivalent to overexcavation.
The installation crew began the installation by undercutting the foundation to a maximum depth of 12 inches (305 mm). Next, they leveled and rolled the subgrade and covered it with overlapping layers of geogrid followed by a 12-inch (305-mm) lift of crushed aggregate compacted to meet the specified density.
“The owner was looking for an equivalent solution that would be less time consuming and costly to install,” says Lars Nelson, Pacific South regional manager for Tensar. “The MSE design satisfied those requirements despite challenging soil conditions.”