A Research Paper on Stabilization of Soil by using Bituminous Material
UDI White Paper - Dr Brown - 2010
1. White Paper
URETEK Deep Injection (UDI) Process
June 28, 2010
Randall W. Brown, PhD, PE
Vice President for Engineering
URETEK USA, Inc.
PURPOSE
The purpose of this paper is to provide a technical discussion of the URETEK Deep
Injection (UDI) process to engineering professionals involved in evaluating insitu
soil stabilization alternatives.
UDI Definition
The proprietary UDI process (U.S. Patent number 6,634,831) is a technique for
stabilizing weak and/or poorly compacted foundation soils insitu and leveling
structures (including pavements) by injecting a high-density polyurethane into the
foundation soils.
Expansive forces are created when the two components of the specially formulated
high-density polyurethane polymer (U.S. Patent number 6,521,673) react. Prior to
the reaction, the low viscosity polymer flows easily into the voids and weak zones in
the soil mass. As the reaction occurs, the expanding polymer compacts the
surrounding soils. The resistance necessary for compaction to occur is achieved by
the soil overburden and by creating a stabilized mass in the upper elevations by the
top down injection pattern.
In sum, the UDI process is a chemical compaction grouting technique using a low-
viscosity polymer that also infiltrates certain soils. The polymer components are
formulated to resist the intrusion of water which could compromise the integrity of
the polyurethane being formed during the reaction.
2. UDI Tenets
Since the UDI patent is 12-pages long, a detailed discussion of each paragraph and
drawing therein is well beyond the scope of this paper. However, four fundamental
tenets may be used to distinguish the UDI process:
1. The polymer is placed via an injection tube. The tube allows the polymer to be
“surgically” placed in the strata where stabilization is needed.
2. Multiple injection tubes are used to promote full coverage throughout the area
being stabilized. As mentioned above, the injection tubes are inserted to
depths within the soil mass that require stabilization.
3. The injected substance is a two-component, high-density polyurethane
characterized by its rapid expansion and large volume increase (a minimum of
5 times its original volume is specified). These characteristics are caused by a
chemical reaction between the two components.
4. Movement is monitored at the surface during the injection process. The first
movement indicates the soil mass has been stabilized at that injection point.
If stabilization is the desired goal, injections at that injection point cease.
Since the soil mass refuses to accept more polymer into the matrix at that
injection point, subsequent injections will result in an upward movement,
detectable on the surface. This phenomenon is desirable if the project
requires leveling of the structure.
UDI Project Development
UDI is an engineered solution. While variables such as soil/water conditions, loads,
and client budgets (just to name a few) make each UDI project different, there are
shared aspects. Consequently, a protocol for developing UDI projects has evolved
over time.
1. Assess the Site
a. Collect available geotechnical information
b. Execute Dynamic Cone Penetrometer (DCP) tests
c. Examine the structure for load-related distresses
d. Determine current loading and projected loading
2. Design the Treatment Plan
a. Review the geotechnical information and DCP test data
i. Identify weak and poorly compacted soil layers
ii. Examine lab results (soil classification, sieve analysis, etc.)
3. b. Select injection pattern and depths
c. Develop injection specifications
i. Polymer characteristics (density, lift capability, etc.)
ii. Injection pressure
iii. Injection temperature
iv. Shot length and sequence
3. Perform Cost Analysis
a. Estimate polymer quantities
b. Calculate mobilization and installation costs
c. Reconcile costs to available budget
4. Prepare Project Proposal
a. Internal review
b. Client review
c. Revisions (as required)
5. Execute Project
a. Upon receipt of Proposal Acceptance
b. Upon receipt of Notice to Proceed (NTP)
6. Post-injection Assessment of Site
Soil/Polymer Interaction
The interaction of the polyurethane grout and the soil mass is a complex issue. The
relationship is governed by soil properties (particularly – density, grain size,
porosity, degree of saturation) and polymer properties (namely – chemical
composition and viscosity). Moreover, the interaction can be adjusted for better
effectiveness by varying injection temperature, injection pressure, shot duration,
and shot sequencing in the field.
Despite the complexity, the following trends have emerged.
1) Aggregate Bases/Subbases and Coarse Sand
a. Polymer travels into the void space and displaces water (if present).
The polymer remains, starts to cure, and acts as a binder.
b. Lower percentages of smaller particles in these soils permit greater
infiltration into the layer prior to expansion.
c. These soils benefit from the dual events of polymer infiltration (binding)
and polymer expansion (compacting).
d. The injection process is repeated until surface movement is detected
indicating the soil is now stable and the expansion force is constrained
in all directions except up.
4. 2) Saturated Fine Sands
a. Polymer expansion displaces the water and flowable soils.
b. Polyurethane encapsulates the remaining soil and begins to “set up”.
c. The injection process is repeated until surface movement is detected
indicating the soil is now stable and the expansion force is constrained
in all directions except up.
3) Layers with Silts and Clay Size Particles
a. The polymer infiltrates weak lenses in these layers.
b. As the polymer begins to expand, it encapsulates and compacts the
surrounding soils.
c. The injection process is repeated until surface movement is detected
indicating the soil is now stable and the expansion force is constrained
in all directions except up.
4) Organic Soils
a. When operating in soft soils, the polymer reaction time is accelerated so
the polymer spends little time moving laterally.
b. The rapid reaction time causes the polyurethane to form a vertical shear
wall within the soft soil mass.
c. By designing the injection pattern, these walls can be shaped into an
interconnected series of confinement cells (a honeycomb-type
arrangement) capable of supporting loads.
Photographs of various UDI-stabilized soil systems are attached to this document.
Conclusion
The URETEK Deep Injection (UDI) process has proven an efficient and effective
technique for insitu stabilization of a variety of soils. Through its research and
forensic investigation programs, URETEK continues to gain knowledge of the
technology’s capabilities and limitations.
7. Stabilization of Uncompacted Crater Backfill Material for the U. S. Navy
Excavating Native Soil to Expose the Crater Repair (notice the veins of polymer)
Intact Extraction of the Stabilized Crater Repair
8. Forensic Excavation of a UDI-Stabilized Peat Deposit
(Note map depicting confinement cell locations)
