Railroad Subgrade Soil Stabilization Lift, and Re-alignment

A 70 foot section of railroad track near Green River, Wyoming had experienced ongoing settlement issues. During springtime, and high water events, the area required weekly re-compaction and leveling. The replaced ballast would continually sink into the wet subgrade soils.

A factor that contributed to the problem, is that the area is located at a drainage point of the surrounding hillsides.

Settlement of the subgrade soils was a continual problem for the railroad as well as the unsafe conditions for freight trains and their personnel travelling over this section of track.

Keeping the track open and safe was a major concern for the Rail Company.

CST partnered with Watco Rail representative Neal Ward to design an effective repair solution for the settled areas of track.

An initial site survey was conducted on all areas of the settled rail. Areas for treatment were identified and a site specific injection design was created to lift the settled areas, and stabilize the subgrade soils beneath the track and ballast to mitigate against any future settlement.

CST installed a high density structural polymer at pre-determined depths to treat weak soil and lift the settled track sections. Crews alternated between sections to allow train traffic to continue through the area.

All sections of settled track and weak soil zones were stabilized.

Injections made into the weak soil zones effectively pushed water away from the areas, and provided a protective barrier beneath the ballast, to stabilize and protect the area against future settlement.

Railroad track was lifted, and realigned to provide a stable, safe passage of the company’s freight trains and personnel traveling across the tracks.

All work was completed in a matter of 3 working shifts without major closure or disruption to trains traveling through.

Colorado Bridge Approach Slab Settlement Lift

Bridge Approach Slab Settlement Repair – Crystal Valley Parkway, CO

Asphalt Pavement Lift of a Bridge Departure where the Subgrade had settled and the pavement needed to be lifted

In Castle Rock, CO, along the Crystal Valley Parkway, the Town of Castle Rock, CO was experiencing bridge approach slab settlement of 1,900 SF of bridge approach, departure, and sleeper slabs on two bridge ends and adjoining pavement. Settlement of adjacent sidewalk had also occurred causing an unsafe driving situation as well as dangerous conditions to pedestrians utilizing the crossover sidewalk area. The unstable subgrade reaching below the sleeper slab would need to be treated to stabilize the area before mill and fill of asphalt pavement could be performed.

Bridge Approach Slab Settlement Solution

CST partnered with the Town of Castle Rock, utilizing their Deep Injection process to treat unstable soil, lift the slabs, and realign sidewalk and pavement areas. Dynamic Cone Penetrometer soil tests were performed to correctly identify the weak soil zones. Injection tubes were placed at depth and expanding structural polymer injected to densify and provide stabilization of subgrade soils. Once the soil is stabilized, injections are continued to provide lift and realignment of the slabs and overlying pavement. The CST Deep Injection process provides proper support to the soil and heavy sleeper slabs to mitigate against future bridge approach slab settlement and movement, while also providing a solid subgrade for pavement.

Repairs were made in two shifts while allowing traffic to continue utilizing the area vs. time and money spent to reroute. Foundation soils were significantly strengthened to mitigate against future settlement. Bridge approach and departure slabs were lifted back to original elevation as well as stabilization and lift of sidewalk areas. Subgrade soils were quickly and effectively stabilized to provide a strong base for asphalt pavement mill and fill operations. The added benefit of water cutoff effectively arrests soil erosion within the area. Significant savings to municipalities and tax payers vs. alternative methods of rip out and replace. Extended use life of the bridge, sidewalk, and pavement.

Culvert Annular Void Fill

Utah DOT Culvert Annular Void Fill

Objective of this project was to fill annulus between culvert and surrounding embankment. The outer pipe was rusted out at the bottom and water was leaking in between the two pipes and coming out bottom of joint. Goal was to seal leaks in an outer pipe, surrounding smaller pipe and fill voids.

Critical elements of this project were dealing with the rusted out bottom of the outer surrounding pipe. Large amounts of water needed to be pushed out and fill resultant voids to assure pipe support and stability.

Dry Fork Mine Rail – Gillette, WY

Load Out & Rail Void Fill & Stabilization

CST Deep Injection Technologies were employed to fill voids and stabilize the floor in the Train load-out building and along rails in the loading area of the Dry Fork Mine in Gillette Wyoming.

Floor stabilization, void fill, and sub-grade stabilization of the building and adjacent track area were completed in three shifts by Concrete Stabilization Technologies, Inc., providing the customer with a permanent solution for their production site.

Douglas County Sheriff MSE Wall Repair – Highlands Ranch, CO

Douglas County Sheriff MSE Wall Repair – Highlands Ranch, CO

Concrete Stabilization Technologies, Inc. partnered with the Douglas County Facilities Management division of Douglas County, CO to stabilize the MSE walls at the Douglas County Sheriff Sub-Station in Highlands Ranch, CO.

CST was referred by a geotechnical engineering firm to provide a solution to stabilize portions of distressed MSE wall. The geotechnical report indicates low density soils between base of wall and top of storm sewer pipe installed approximately 16’ prior to MSE wall. A section of the MSE wall was slated to be rebuilt after soil stabilization project was completed.

Patented processes were used to increase bearing capacity and stabilize the West and East MSE wall in the sewer trench area of the facility for an area of approximately 60 LF. CST’s deep injection method was performed to reinforce low density soils between top of storm sewer pipe and bottom of MSE wall. The distressed MSE wall was monitored with laser levels during the injection of expanding structural polymer into the underlying soils. Injections were also performed around a manhole to void fill and seal joints.

Video camera inspections were done before and after injection to verify pipe condition. The patented injection processes used in this stabilization project saved the customer from excavating and possibly replacing the pipe.

This project was completed on time and on budget!

Salt Lake City Industrial Road Restoration – UT

Patching, Diamond Grinding and Joint Resealing

Located close to downtown Salt Lake City, Industrial Road at California Avenue needed some well deserved repair. Industrial Road is a critical concrete pavement thoroughfare for industrial traffic and heavy duty trucking in the area as it is located adjacent to a major truck stop and trucker fuel depot. The majority of the concrete pavement was structurally sound but, due in part to sub-grade softening caused by surface water intrusion through the joints, the pavement exhibited differential settlement between the slabs measuring up to 1.5-inches. The combination of constant heavy truck traffic and the presence of water in the sub-grade facilitated continued erosion beneath the slabs.

Although the owner, the Salt Lake City Corporation, considered replacing all concrete slabs. They opted instead to preserve the existing concrete. After all, only 10 percent of the slabs showed cracking. The methods chosen for repair were soil foundation stabilization, slabjacking, slab replacement, stitch-in-time crack repair, dowel bar retrofit (DBR), diamond grinding and joint resealing. A total of 326 dowels were retrofitted on the 1,461 square-yard project. A series of 5/8 inch holes were drilled through the slabs to facilitate the injection of high density expansive polymers into the sub-grade soil to a depth of 3.5 feet. With the deep injection process complete, the same polymers were then injected at the slab/sub-grade interface through the same 5/8-inch holes to fill fissures and voids as well as to lift each concrete slab to match the elevation of adjacent slabs. This process minimized the differential settlement between the slabs. Additional lifting was then employed beneath the slabs to create a 1.5 percent drainage slope from the crown of the road to the curb to facilitate better drainage and safety.

This design engineer decided to test an innovative new crack stitching procedure utilizing polyurethane material and fiberglass panels. The CST Stitch-In-Time process was selected and used beneath five slabs that contained minor cracks. Following the slab stabilization and lifting operations, the Stitch-in-Time process required the placement of ½ inch fiberglass panels (stitches) within saw cuts made perpendicular to the slab crack. The cuts were then filled with clean pea gravel and an acrylic bonding material was poured into each cut. Four stitches were placed in each candidate slab.

Following the stabilization, lifting and stitching operations, the retrofit dowel bars were installed in the slabs, severely cracked slabs were removed and new concrete was placed in the necessary areas. Once the concrete was fully cured, the entire area was diamond ground to remove remaining surface defects, increase smoothness and provide a safe, high friction wearing surface. The joints between the slabs were then cleaned and resealed to prevent the intrusion of water and incompressible materials. As a final step, a sealing compound was applied to the concrete surface to provide additional protection.
Another challenge was slab cutting at the joints prior to the lifting process. The summer heat caused slab expansion, which can bind the saw blades and restrict a slab’s upward movement. To prevent this occurrence, a chisel-shaped device was inserted into the saw cut adjacent to the trapped blade and pressure was applied to spread the cut sufficiently to allow the blade to be extracted.

The project was scheduled for 90 days but was completed in a mere 62 days and was under budget. As a result of this successful project, the owner has chosen to use concrete pavement preservation on future projects within the city. The combination of using high density expansive polymers in conjunction with other concrete pavement preservation techniques including dowel bar retrofit and diamond grinding should extend the life of this pavement for approximately 15-20 years.
According to Mike Kendell of SLC Engineering, “Ride quality was greatly improved and Salt Lake City is satisfied with the results.”