Vibro compaction for liquefaction mitigation Operational Constraints For all site- and foundation-related construction, communicating the constraints of each project site and its environment to the potential contractors is essential for the development of competitive and realistic proposals and for safe and productive execution of the work. This is critically important to ground improvement projects for which specialized techniques may influence or be influenced by these constraints to a greater extent than conventional construction. The specification should clearly define existing agreements, covenants, etc. that exist between the Owner and third parties, or are attached to the project site, which may influence the conduct of the ground improvement work. The specification must also define: 1) Any schedule or shift limitations, e.g. no equipment noise before 0700 hours; no work between “rush hours” of xx to yy, etc. 2) The preliminary construction schedule as anticipated by the Owner/Designer. Is adequate time available to consider pre- loading or staged construction options? 3) Limitations on noise, dust, movement and vibrations. This must define not only threshold values, but also how and at what locations the threshold values are to be measured. a) Specific sensitive receptors should be identified, e.g., hospitals, schools, precision machinery, etc. b) Requirements for monitoring of noise, vibration, movements, etc. during ground improvement work. i) The type, frequency and reporting format should all be clearly defined, along with the parties responsible for collecting and distributing the data. 4) Available sources of water: available volume per day, maximum draw rate, available pressure, etc. 5) Limitations on discharge of wastewaters, including volume, rate and locations. 6) Requirements or limitations for handling/disposing of by- products resulting from ground improvement work. 7) Any known or anticipated environmental restrictions or concerns: wetlands, protected habitats, contamination, etc. 8) The nature, location (position and elevation), construction and condition of existing structures and utilities (on and near the project site), along with criteria for allowable vibrations, settlement, heave, lateral movement, etc. a) Requirements for pre- and post-construction condition surveys. 9) Access limitations/restrictions and defined routes of allowed access. This would include defining overhead structures, road and bridge ratings and utilities existing in the work areas or along available access routes. 10) Limitations on available laydown and storage areas. In addition, the specification should address the obligations, among the parties, for construction, design and certification of a stable working platform for safe operation of ground improvement equipment. Performance Requirements An effective specification for ground improvement should explicitly define the performance expectations and requirements for the improved ground based on clearly defined loading and service conditions. It must define the conditions under which the criteria are to be applied, the location at which the criteria are to be assessed and the time frame for evaluation. The specification should be explicit in defining the structures and work limits for which the ground improvement is intended. Appropriate references to project drawings and sketches are recommended. DEEP FOUNDATIONS • MAR/APR 2016 • 87
