3500 TERMINAL AVE Geotech Report 2022-10-25

Port of Everett—South Terminal Wharf& Electrical Upgrades—Phase 2 123 Stresses During Pile Driving Steel pipe piles should be driven with a pile hammer capable of delivering sufficient driving energy to achieve capacity while not overstressing the steel. Based on the subsurface conditions encountered in our borings,we anticipate there may be significantly different penetration depths to refusal from one pile to another. It will be helpful,when installing a large group of piles,to begin installation from the center piles in the group and work outward. Material order lengths should reflect potential variability in subsurface conditions. We understand that piles will be driven close-ended. Driving a close-ended pile into the bearing layer will likely require penetrating soils with a high driving resistance.Typical construction methods used to install piling through dense soil include using a larger hammer or pre-drilling. Using a larger hammer is generally more cost-effective. Larger hammers can cause damage to a pile during pile driving.To reduce the potential for damage,the pile-driving stresses should be kept sufficiently below the yield strength of the steel. Based on our experience with similar projects,we anticipate that pile damage from pile-driving stresses is not likely to occur if the driving stresses are kept at less than about 80 to 90 percent of the steel yield strength. Depending on actual field conditions, hammer size,duration of driving,and pile size, it may be possible to allow driving stresses higher than this without pile damage. Contractor's WEAP Analysis We recommend requiring the contractor to perform and submit for review a Wave Equation Analysis of Pile Driving(WEAP)once the piles,hammer,and driving system have been selected,to confirm the adequacy of the hammer and to estimate driving stresses. It is the contractor's responsibility to select an appropriate hammer and driving system to reach the design pile tip elevations without damaging the piles. Project specifications should be written so that the contractor is made responsible for any damage to the piles during installation. In addition,we recommend monitoring selected piles during construction with PDA and verifying the achievement of required pile resistances with CAPWAP software. Preliminary WEAP Analysis We performed preliminary wave equation analyses using the computer program GRLWEAP to predict axial pile driving stresses and penetration resistances during driving at assumed compressive pile capacities.We performed WEAP analyses for different driving scenarios that represent the pile driving conditions expected during construction. Pile drivability is,to a large degree,a function of soil conditions and the pile hammer system.The upper soil conditions consist of ESUs 2,4,5,and 6,which are sand and gravel (with the exception of ESU 5)with densities ranging from loose to dense. Difficulties during pile driving may be caused by obstructions or dense gravel zones that may exist in the areas where piles are driven.Obstructions may be more prevalent close to the surface of the submerged slope where riprap and other larger construction material is expected.We anticipate that the existing riprap on the slope will need to be removed locally for installation of piles and then replaced after the piles are installed. V 19232-01 HARTCRO/SEn December 6,2017