"John N. Puder was contacted as our choice for a difficult job. We have done some very tricky, high profile projects with John which were finished on time and on budget. To do the impossible takes a team that can work together, communicate, and give and take what is necessary. JNP is a sterling example of the type of contractor needed to do the impossible." ~ Geotechnical Professional Engineer
Holmes Correctional Institution Project Bonifay, FL |
Compaction Grouting - Sinkhole Remediation
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| Top: Vertical grout pipe installation underway
using an MKT #5 hammer. Bottom: Grouting had just begun when a 30-foot diameter sinkhole opened up within the work area. |
Over the course of several years, a portion of heavily travelled SR 434 had exhibited recurring pavement settlement that the Florida Department of Transportation (FDOT) had rectified by surface treatment. Later, FDOT conducted a comprehensive evaluation of the subsurface conditions in order to arrive at a permanent solution to the problem. Results indicated that the settlement was due to cover-subsidence sinkhole activity which, if not properly addressed, could potentially lead to catastrophic highway collapse. FDOT therefore undertook to stabilize the subsurface material by compaction grouting before resurfacing the roadway. John N. Puder (JNP) was retained by C.A. Meyer Paving and Construction of Orlando, FL to perform the work.
Meeting the challenge of dealing with tight site conditions, maintaining traffic patterns, and working with heavy traffic flow in close proximity to the construction zone required a cooperative effort between JNP, C.A. Meyer, FDOT engineers, and Professional Service Industries, Inc. The latter monitored the work under FDOT direction. This project subsequently received an Associated Builders and Contractors (ABC) Subcontractor Eagle Award.
Grouting Program
The grouting program was designed to be performed in three phases to maintain traffic flow. Phase 1 involved the center 20 feet of the roadway. Phases 2 and 3 involved the west and eastbound travel lanes respectively.
An MKT #5 hammer was selected to advance 3-inch diameter vertical grout pipes on a nominal 20-foot primary grid pattern to top of karstic limestone at 60 to 80 feet below grade. In order to ensure that travel lanes stayed free, angled rotary drilling was used where necessary. Low slump (4 to 6-inch maximum) grout was pumped under 100 psi pressure to first seal the surface of the limestone. Grouting then continued upwards as the grout pipes were withdrawn in 2-foot increments, creating a series of interconnected grout “bulbs” to displace and thus densify the adjacent loose soils.
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| Top: During the work, angled rotary drilling
was performed where necessary to ensure travel lanes stayed open. Bottom: Phase III grouting nears completion on east bound travel lanes.. |
At each stage, grouting was performed until line pressure of 300 psi was reached or slight surface heave was observed. Where primary grouting did not meet either criterion, secondary grouting was performed at the midpoint of the primary grid.
Cover Collapse
Grouting for phase 1 had just begun when cover collapse created a 30-foot diameter sinkhole within the immediate work area that also encroached into a traffic lane designated to remain open by FDOT. Immediate backfilling of the crater to replace the raveled soils, followed by strategic grout pipe installation and carefully controlled grouting operations by the JNP crew, were all instrumental in the fast restoration of a stable road base and minimized interruption to traffic flow.
The remaining two phases of the grouting program were completed without incident. A total of 54 locations were injected over the 60-day grouting program, with +1100 cubic yards of grout pumped.