What Is a Secant vs. Tangent Pile Wall?
Secant (the interlocking — the primary/secondary; the watertight) vs. tangent (the touching — the contiguous; the gaps') pile walls retain the excavation (the drilled — the shafts'; the concrete's). The secant: the cutoff (the water's — the interlocked); the tangent: the economical (the dry's — the touching). The selection: the groundwater's — the wall's.
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Secant walls
The interlock (the primary's — the unreinforced; the secondary's — the reinforced; the 3-6 inch overlap), the watertight (the cutoff — the below's; the groundwater's), the stiffness (the high — the deep's; the 50+ foot), and the cost (the premium — the drilling's; the guide wall's).
Tangent walls
The contiguous (the touching — the no-overlap; the gaps' — the soil's), the dry (the above's — the water's; the dewatered's), the economical (the simpler — the faster; the secant's — the 70%), and the lagging (the between — the shotcrete's; the soil's — the retained).
Selection and construction
The water (the secant's — the cutoff; the tangent's — the dewatered), the depth (the secant's — the deep; the tangent's — the moderate), the movement (the stiff's — the adjacent's; the monitored), and the guide (the wall's — the alignment's; the constructed first). The secant seals — the tangent saves.
The bottom line
Use secant (interlocking, watertight) pile walls below groundwater and for deep excavations; tangent (contiguous) walls suit dry/moderate cuts at ~70% of secant cost — build guide walls first.
Torch Engineering PLLC · (480) 490-0064 · info@torchengineering.com — PE stamping backed by Apex Grid Engineering.