1018 14TH ST 2023-02-09 - Laserfiche WebLink

SHANNON&WILSON,INC. hammer installation, and rate of advancement for vibratory hammer installation. In addition, the record should include time, date, reasons for delays, tip elevation, specified criteria, initials of inspectors making final acceptance of the pile, and other pertinent information. We recommend that Shannon & Wilson observe pile driving and/or review the pile driving records daily. 5.2.1 Impact Hammer Fixed-lead-type impact pile driving equipment is recommended. The use of hanging or swinging leads is not recommended, unless they are constructed so that they can be held in a fixed position during driving operations such as by the use of a template. Leads should be of sufficient length so that the use of followers will not be necessary. The Contractor should furnish the manufacturer's specifications and catalog for the hammer proposed. We recommend that a Wave Equation Analysis of Pile driving be performed to evaluate the proposed hammer type. 5.2.2 Vibratory Hammer A vibratory hammer may be used to install the open pipe piles that would support the viewing platform. If vibratory hammers are used to drive the piles into glacial soil,they should be appropriately sized for the pile and soil conditions. If vibratory hammers are oversized for the pile and soil conditions, the glacially overridden soils could be disturbed resulting in a reduction in the pile side resistance. Vibratory hammers are rigidly connected to the pile using hydraulic clamps. They use paired counter-rotating eccentric masses, synchronized by a gear system and driven by one or more hydraulic motors. The eccentric masses typically rotate at about 1,200 to 3,000 revolutions per minute, or about 20 to 50 Hertz. The continuous energy impulses transferred from the hammer and pile to the soil travel outwards away from the pile wall and tip as stress waves. In granular soils, such as these present at the project site, the stress waves induced by the vibration cause movement and loss of contact pressure between individual soil particles. As a result,the internal friction of the soil and the contact friction between the soil and pile are reduced, allowing the pile to penetrate the soil. As noted above,this process can also result in reduced pile resistance if oversized vibratory hammers are used. We recommend that Shannon& Wilson evaluate the Contractor's hammer selection as compared to the anticipated soil conditions. If a vibratory hammer is used to install the piles we recommend that production piles be driven to within about 3 feet of the expected tip,then impact driven to tip. For the test piles, the vibratory hammer should be used to drive the piles to within 10 feet of the expected tip,then 21-1-21761-003-R I Cdocx/wp/cIp 21-1-21761-003 18