Been relatively quiet around the Los Lunas High School site these past couple of weeks. Most of the site utilities work has wrapped up, those crews awaiting the completion of the earthwork to recommence their under-slab work.
Speaking of earthwork, that in itself was a rather large endeavor. The earthmovers first over-excavated the entire building pad, stockpiled the native soils, blended same to create suitable fill, installed the resulting engineered fill in compacted lifts to the correct elevation to support the first floor slabs.
Whew! To the casual observer, that’s a whole lotta work just to get back to where you started
As for foundation earthwork, the project’s Structural Engineer (Chavez Grieves) specified a rather clever, expedient system to mitigate the potential for undermining the existing building foundations immediately adjacent to our new building. In lieu of over-excavating the new foundations, or installing expensive cast-auger piers, the native soils under the foundations are compacted and reinforced by a rammed aggregate pier system (RAPS).
The RAPS in essence, augers a hole down to around 20′below grade, fills the resulting void with compacted gravel lifts. The compaction process not only installs an aggregate pier, but also compacts adjacent native soils. Long story short, no massive earthwork removal and re-installation is required, nor existing foundations undermined, yet the soils are thus improved to withstand the loads of a traditional foundation design. Saves the District both time and money- cool beans, no?
Michael Heitman, VP, Project Architect.