Application of Mammoth Vibro-Tamper (MVT) for the Shallow Compaction at Airport Runway Expansion Project on Florida Limestone Ground-Paper

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The Fort Lauderdale–Hollywood International Airport runway expansion encountered cavities and variable limestone–sand soils that required ground improvement to support aircraft operations. Mammoth Vibro-Tamper (MVT) was accepted as an alternative to Deep Dynamic Compaction (DDC), primarily to reduce vibration and noise near existing facilities. Work on the 1.5-mile runway was completed between 2012 and 2014 without project delays.<br /><br />MVT uses a large vibrating steel plate to densify shallow ground. Project testing showed stronger improvement than DDC: average post-treatment SPT-N values were 25.6 for MVT versus 15.2 for DDC, while the proportion of tests failing the required 70% relative-density criterion was 9.7% versus 32.7%. The authors also report that MVT produced greater compaction energy and higher productivity, and could treat the full area. Some compaction effects were measured to about 17 feet.<br /><br />Two adaptations improved performance in the difficult limestone ground. Trenches excavated to 10 feet deep and 3 feet wide fractured hard limestone and helped collapse cavities before MVT treatment, increasing SPT values. A two-stage tamping sequence was effective where groundwater surfaced during the first pass: a later second pass achieved further densification.<br /><br />Vibration monitoring showed substantially less impact from MVT than from DDC, particularly within 150 feet of the equipment. The report concludes that MVT is an effective, lower-vibration option for shallow compaction in suitable ground, although uniformly sized porous limestone gravel in part of the eastern runway area could not be compacted using the proposed approach.

Keywords

Fort Lauderdale–Hollywood International Airport

runway expansion

Mammoth Vibro-Tamper

Deep Dynamic Compaction

ground improvement

limestone soils

soil densification

vibration reduction

SPT-N values

limestone cavities