STEEL SHEETPILE RETAINING WALL IN CLAY
STEEL SHEETPILE RETAINING WALL IN CLAY
(OP)
The majority of my sheetpile design experience has been in fine to medium coarse sand with traces of clay and silt. I am designing a 30' x 30' sheetpile box with 28 foot deep excavation for a lift station. The soil profile is very soft clay (N=1 to 2)from ground level to 45 feet and fine to medium coarse sand (N-30) from 45' to 60' below land surface. Groundwater table is 2 feet below land surface and I am requiring dewatering inside and outside the box to lower grounwater table to 30 feet below land surface (2 feet below dredge line). I have a 4 tiered waler system with diagonal bracing at the corners. Length of sheetpile is 55 feet. I am getting very high maximum bending moment on the sheetpile using the Pile Buck SPW911 software that require PZ40 sheets whereas if the excavation was in sand PZ27's would be more than adequate. Does clay create that much more bending moment or am I miscalculating?





RE: STEEL SHEETPILE RETAINING WALL IN CLAY
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RE: STEEL SHEETPILE RETAINING WALL IN CLAY
Are you familiar with the software Prosheet from Skyline Steel? Presently, I rarely do sheeting design but I recall that about 10+ years ago they had software that gave very conservative results.
Thanks
RE: STEEL SHEETPILE RETAINING WALL IN CLAY
The default earth pressure diagram for ProSheet is triangular. You can enter in other diagram shapes but not easily. There are other easier programs for that. I rarely use triangular earth pressure diagrams except for cantilevered sheeting and walls where the retained soils are very soft or for single tier braced or tiedback walls where the brace or tieback level is unusually close to the top of the wall.
Also, for the Boussinesq surcharges, I believe it multiplies the calculated surcharge by Ka which then gives less lateral surcharge than what some agencies (railroads) are requiring.
You can't beat the price though.
www.PeirceEngineering.com
RE: STEEL SHEETPILE RETAINING WALL IN CLAY
RE: STEEL SHEETPILE RETAINING WALL IN CLAY
RE: STEEL SHEETPILE RETAINING WALL IN CLAY
www.PeirceEngineering.com
RE: STEEL SHEETPILE RETAINING WALL IN CLAY
RE: STEEL SHEETPILE RETAINING WALL IN CLAY
RE: STEEL SHEETPILE RETAINING WALL IN CLAY
I also think dewatering the soft clay will be difficult. Would it be possible to brace the piling across the excavation, and 'seal-in' the excavation bottom by over-excavating and replacing with a thickness of concrete equivalent (with a proper safety factor) to the hydrostatic head difference?