Full Depth Pavement Patch – Stabilization of Foundation Soils

Problem

Stabilization of areas of roadways where full depth repair is to be done to minimize the need for additional cutout of poor base/sub-base/sub-grade once the roadway surface has been removed. The failure of the pavement surface is often caused by weak or insufficient support in the foundation soils. Ignoring this problem leads to premature failure of the patched pavement. Tearing out the base/sub-base/sub-grade is costly and causes significant lane closure time including daytime lane closures. The replacement of the foundation soils is often ineffective due to the inherent difficulty to compact the new soils in a small area. Adjacent panels can be negatively affected by disturbing their foundation soils during the repair.

Solution:

Utilize URETEK Deep Injection Process to stabilize the foundation soils prior to replacement of the failed pavement section. This is accomplished by drilling multiple 3/4″ holes through the existing pavement and injecting polymer through tubes, placed at minus 3′ to minus 4′ from the pavement surface. This is usually done on a 4′ grid pattern. URETEK monitors the surface using laser monitors and/or dial indicators and knows that the roadway has become adequately supported when an indication of movement is detected on the monitors. Injection is also performed one row in front and in back of the failed section. The pavement can then be removed and new pavement placed on a sufficiently strong base/sub-base.

Expected Results:

  • Foundation soils are sufficiently stiffened to support the load on the new patch.
  • Extends the life of the full-depth patch.

Benefits:

  • Zero daytime lane closures.
  • Injection is accomplished sufficiently ahead of the patching crew so that the patching process can take full advantage of the lane closure time frame.
  • Injection can be accomplished in wet soil conditions as the URETEK 486 STAR hydro-insensitive polymer will form a dimensionally stabile polymer even when injecting into saturated soils. The expansion process will also drive the water out of the soil system.
  • No disruption to utilities.

Alternates:

  • Complete removal of the weak foundation soils. Compaction of the new soils is difficult in the small area of a patch and often leads to pre-mature failure just as quickly as if the foundation soils had not been replaced. Weather can cause delays as removal of foundation soils will be postponed if inclement weather is threatening. High cost, high risk, minimal effectiveness.
  • Ignore the weak foundation soils due to high cost and minimal effectiveness of traditional replacement methods. Presumably the weak foundation soils caused the premature failure of the pavement and the cycle will likely be repeated.

Reference Documents:

  1. VDOT I-81 Projects – As part of the stabilization of joints and cracks on I-80, over 2000 LF of foundation soils under the pavement has been injected prior to replacement and installation of the patch. This was a change order on one project for 1000 LF. View Memo.
  2. ADR Forensic Photos – The entire premise of this research project for the Navy was to stabilize the un-compacted fill in 20′ Diameter bomb craters. While you do not have bomb craters on your roadways, there are certainly patches of failed concrete caused by weak foundation soils. View Photos.
  3. NAVFAC Press release – Navy was satisfied with the foundation support the URETEK Deep Injection Method provided to the concrete patches on their runways. View Press Release.
  4. Penn State University Demonstration – Summarizes the demonstration URETEK performed in 2012 at the request of PennDOT. View Demonstration.