Check the pile has sufficient drivability and that the driving system is matched to the pile. If the pile and driving system are suitably matched, check driving system operation for compliance with manufacturer’s guidelines. If no obvious problems are found, dynamic measurements should be made to determine if the problem is driving system or soil behavior related. Driving system problems could include preignition, preadmission, low hammer efficiency, or soft cushion. Soil problems could include greater soil strength than anticipated, temporarily increased soil resistance with later relaxation (required restrike to check), large soil quakes, or high soil damping.Soil resistance at the time of driving could be lower than anticipated or driving system performance is better than anticipated. Perform restrike tests after an appropriate waiting period to evaluate soil strength changes. If the ultimate capacity based on restrike blow count is still low, check drive system performance and restrike capacity with dynamic measurements. If drive system performance is as assumed and restrike capacity low, the soil conditions are weaker than anticipated. Foundation piles will probably need to be driven deeper than originally estimated or additional piles will be required to support the load. Contact the structural engineer/designer for recommended change.If borings do not indicate weathered profile above bedrock/bearing layer, then pile toe damage is likely. For piles that allow internal inspection, reflect light to the pile toe and tape the length inside the pile for indications of toe damage. For piles that cannot be internally inspected, dynamic measurements could be made to evaluate problem or pile extraction could be considered.Review soil borings. If soil borings do not indicate soft layers, pile may be damaged below grade. If the pile was spliced, re-evaluate splice detail and field procedures for possible splice failure.Pile movements likely due to soil displacement from adjacent pile driving. Possible solutions include redriving of installed piles, change in sequence of pile installation, or predrilling of pile locations to reduce ground movements. Lateral pile movements could also result from adjacent slope failure.Piles may be moving out of alignment tolerance due to hammer-pile alignment control or due to soil conditions. If due to poor hammer-pile alignment control, a pile gate, template or fixed lead system may improve the ability to maintain alignment tolerance. Soil conditions such as near surface obstructions or steeply sloping bedrock having minimal overburden material may prevent tolerance from being met.<p>Piles may be moving out of location tolerance due to hammer-pile alignment control or due to soil conditions. If due to poor hammer-pile alignment control, a pile gate, template or fixed lead system may improve the ability to maintain location tolerance.</p><p><em>For piles encountering shallow obstructions:</em></p><p>If obstructions are within 3 feet of working grade, obstruction excavation and removal is probably feasible. If obstructions are at deeper depth, are below the water table, or the soil is contaminated, excavation may not be feasible. Spudding or predrilling of pile locations may provide a solution.</p>If deep obstructions are encountered contact the engineer for remedial design. Ultimate capacity of piles hitting obstructions should be reduced based upon pile damage potential and soil matrix support characteristics. Additional piles may be necessary.Check hammer-pile alignment since bending may be causing the problem. If the alignment appears to be normal, tension and bending combined may be too high. The possible solution is as above with complete cracks.<p>Determine pile head stress for observed blow count and compare with allowable stresses. If high calculated stress, add pile cushioning. If low calculated stress, investigate pile quality, hammer performance, hammer-pile alignment</p>Determine tension stresses along the pile for observed blow counts. If high calculated tension stresses, add cushioning or reduce stroke. If low calculated tension stresses, check hammer performance.Determine tension stresses along the pile. If high calculated tension stresses, consider heavier ram. If low calculated tension stresses, take measurements and determine quakes which are probably higher than anticipated.Check hammer-pile alignment since bending may be the problem. If alignment appears to be normal, tension and bending combined may be too high; solution will then be the same as for complete cracks above.Check helmet size/shape; check steel strength; check evenness of the pile head, banding of timber pile head. If okay, determine pile head stress. If calculated stress is high, reduce hammer energy (stroke) for low blow counts; for high blow counts, different hammer or pile type may be required.If soil borings do not indicate soft layers, pile may be damaged below grade. Investigate both tensile stresses along the pile and compressive stresses at toe. If calculated stresses are acceptable, investigate the possibility of obstructions/uneven toe contact on hard layer or other reasons for pile toe damage.Review the wave equation analysis and check that all parameters were considered. Check hammer and driving system. If no defects are found in driving system, field measurements should be taken. Problem could be preignition, preadmission, low hammer efficiency, soft cushion, large quakes, high damping, greater soil strengths, or temporarily increased soil resistance with later relaxation.Probably, soil resistance is lower than anticipated. Perform restrike testing. Establish setup factor and drive to lower capacity. Hammer performance may also be better than anticipated, check.The field stroke is less than 90% of the calculated stroke. Check that ram friction is not a problem. Compare calculated and observed blow count. If observed one is lower, soil resistance is less than anticipated. If blow counts are comparable, reanalyze with lower combustion pressure to match observed hammer stroke.See if there is a hammer of same type, similar ram weight and energy rating and modify its data.Both calculated stresses and blow counts are too high. Increase pile impedance or material strength or redesign for lower capacities. If soil is fine grained or known to exhibit setup gains after driving, then end of driving capacity may be chosen lower than required. Capacity should be confirmed by restrike testing or static load testing.