Common use of Determine Driving Resistance Clause in Contracts

Determine Driving Resistance. Drive piles in one continuous operation. Determine the driving resistance of the piling based on the method specified in the plans, which will be one of the following methods (a – c): a. Upon completion of the dynamic pile testing in accordance with Special Provision Section 523. The pile bearing will be determined by computing the penetration per blow with less than ¼-inch (6-mm) rebound averaged through 12 inches (305 mm) each of penetration. When it is considered necessary by the Engineer, the average penetration per blow may be determined by averaging the penetration per blow through the last 10 to 20 blows of the hammer. In soft material the driving resistance may be determined, at the Engineer’s discretion, after delaying driving operations and performing pile re- strikes. b. Upon completion of the loading test in accordance with Sub-Section 520.3.05.D.2. c. Shall not be used when driving pile to hard rock. Using FHWA-modified Gates Formula as provided below: Rndr = 1.75 (Ed)0.5 log10 (10Nb) - 100 (kips) U.S units Rndr = 7 (Ed)0.5 log10 (10Nb) - 550 (kN) S.I. units Where: These resistance formulas apply only when: • The hammer has a free fall. • The head of the pile is not broomed, crushed, spalled, or excessively crimped. • The penetration rate is reasonably uniform. Determining driving resistance by formula is not a Pay Item. Provide the facilities for determining driving resistance by formula as an incidental part of the work. Once the driving resistance has been determined by one of the methods noted above, do not continue to drive piles if the Engineer determines that the piles have reached practical refusal. Practical refusal is defined as 20 blows per inch with the hammer operating at the highest setting or setting determined by the Engineer and less than ¼-inch (6-mm) rebound per blow. The Engineer will generally make this determination within 2 inches (51 mm) of driving. However, the Engineer will not approve the continuation of driving at practical refusal for more than 12 inches (305 mm). When the required pile penetration cannot be achieved by driving without exceeding practical refusal, use other penetration aids such as jetting, spudding, predrilling or other methods approved by the Engineer.