SR 170: San Carlos

Design of a light-weight concrete fill (LCF) retaining wall for a sidehill roadway widening. Railroad tracks were within 20-ft of the toe of the existing slope, with a Southwest Gas Pipeline between the slope and the tracks. Additionally, the subsurface conditions consisted of soft, saturated, clayey soils. Settlements from surcharges needed to be minimized to avoid adversely affecting the pipeline or the railroad. Instead of ground improvement, a decision was made to use LCF with a unit weight of 30 pcf to mitigate adverse settlement.

A rather unique and innovative solution was developed that combined a soil nail wall with LCF and post-and-panel facing. The existing embankment was trimmed and secured by means of a soil nail application. The nails were extended beyond the wall face and connected to the post-and-panel facing. The space between the soil nail wall face and the post-and-panel was filled with LCF.