REVIEWED BLD BLD2023-1534+Geotechnical_Report+12.7.2023_12.51.33_PM+3940178.,.,.,.,.,.REVIEWED ,.,.,.........
BY
CITY OF EDMONDS RECEIVED
BLD2023-1534 Dec142023
BUILDING DEPARTMENT!
Pipe piles should consist of Schedule 40 galvanized steel with mechanical couplers for splices. Battered
piles may be necessary to provide lateral support to the structures.
The number of piles required depends on the magnitude of the design load. Allowable axial compression
capacities of 6, 1o, and 15 tons may be used for the 3-, 4-, and 6-inch diameter pin piles, respectively, with
an approximate factor of safety of 2 for piles driven to refusal. Penetration resistance required to achieve
the (refusal) capacities will be determined based on the hammer used to install the pile. Tensile capacity of
pin piles should be ignored in design calculations.
It is our experience that the driven pipe pile foundations should provide adequate support with total
settlements on the order of or less.
For 3-, 4-, and 6-inch pin piles, the following table is a summary of driving refusal criteria for different
hammer sizes that are commonly used:
Hammer
3" Pile Refusal
4" Pile Refusal
6" Pile Refusal
Hammer
Weight (lb) /
Criteria
Criteria
Criteria
Model
Blows per
(s/inch
(s/inch
(s/inch
minute
penetration)
penetration)
penetration)
Hydraulic
850 / 900
10
16
TB 325
Hydraulic
11100 / 900
6
10
20
TB 425
Hydraulic
2,000 / 600
3
4
10
TB 725X
Hydraulic
3,000 / 500
6
TB 830X
Please note that these refusal criteria were established empirically based on previous load tests on 3-, 4-,
and 6-inch pin piles. Contractors may select a different hammer for driving these piles and propose a
different driving criterion. In this case, it is the contractor's responsibility to demonstrate to the
geotechnical engineer's satisfaction that the design load can be achieved based on their selected equipment
and driving criteria.
A structural engineer shall perform the structural design of the pile including spacing and reinforcing
steel. The structural engineer also should determine the buckling load for the slender piles and make sure
that is not exceeded.
A 200 percent load test should be performed on 3 percent of the total piles. This test consists of increasing
the load on a test pile in 25 percent increments up to 200 percent of the design load. This load is held for 1
hour and deflections are measured on a dial gauge (to the hundredths or lower) for each load up to 200
percent. The pile should be unloaded in 25 percent increments.
Lateral resistance for footings can be developed using battered piles or an allowable equivalent fluid passive
pressure of 225 pounds per cubic foot (pcf) acting against the appropriate vertical footing faces (neglect the
upper 12 inches below grade in exterior areas).
Regards,
Phil Haberman, PE, LG, LEG
Principal
Cobalt Geosciences, LLC
(2o6) 331-1097
www.cobaltgeo.com
COBALT
G E 0 S C I E N C E S