Support of Excavation - Pitfalls in Design and Construction-PPT Presentation

PPT Presentation

Pdf Summary

The presentation introduces support of excavation (SOE) systems—also called shoring, temporary support, or excavation support—and their role in keeping excavations safe and stable. It emphasizes that OSHA requires shoring for vertical excavations deeper than five feet, underscoring that SOE is both a legal requirement and a life-safety measure.<br /><br />Common wall systems include sheet piles, soldier piles with lagging, micropiles, tangent and secant piles, slurry walls, soil-mix walls, and soil-nail walls. Each involves trade-offs in cost, water control, movement, constructability, equipment needs, and suitability for site conditions. Excavations may be supported by cantilever or deadman walls, internal bracing, or external tiebacks; these options differ in height limits, workspace impacts, coordination needs, and easement requirements.<br /><br />The presentation identifies key design and construction pitfalls: groundwater, base heave, global stability, inadequate quality control, vibration, and natural or man-made obstructions. Groundwater risks include excess pore pressure, seepage, and confined aquifers, which can cause heave, loss of resistance, or settlement beyond the excavation. Potential controls include dewatering, depressurization wells, wick drains, and observational monitoring. Base heave—especially in soft clay—may require measures such as jet-grout plugs, tremie slabs, or tension piles. Designers should also evaluate mass uplift and deep-seated failure.<br /><br />Case histories illustrate how inadequate subsurface investigation, groundwater control, or construction oversight can lead to serious failures. The presentation stresses specifying and carrying out construction quality assurance, coordinating support systems with the permanent structure, and anticipating site constraints early.

Keywords

support of excavation

shoring

excavation safety

OSHA

sheet piles

groundwater control

base heave

tiebacks

soil stability

construction quality assurance