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.

Teton Building Column Reinforcement – Cheyenne, WY

Concrete Stabilization Technologies, Inc.’s crews began work on the column repair & rehabilitation project at the Teton Building in Cheyenne, Wyoming Monday, June 25th, 2012. The project began by placing shoring and re-moving and cleaning up the deteriorated columns. The following day, the concrete floor was removed from the area. A short break in the work was taken to allow tenants to continue working without disruption. During the lunch break, the concrete around the columns was broken up and removed. The column depth below the top of the concrete floor was approximately seven inches (to the top of the foundation pad). The foundation pad is approximately 5 feet by 5 feet and foundation pad thickness is 2 plus feet.

Crews arrived on the job site at 7:00 a.m. the following day and returned all of the rental equipment. A call was made to order concrete to arrive at 1:00 p.m. At 8:00 a.m., we started applying the primer with a paint brush to the north column. At 8:21, we started applying the Tac-coat with a plastic 8” putty knife. At 8:40 a.m. we started wrapping the carbon fiber (33” H x 8’ L) to the Tac-coat and then applying the saturation coat with a small paint roller on top of the carbon fiber material. Once the satu-ration coat was applied, we broadcast small rock to the epoxy to give the stucco a surface to bond with. We finished the north column at 9:05 a.m. and then moved to the south column. At 9:15 a.m., we applied the primer and at 9:30 a.m., applied the Tac-Coat. At 9:55, the carbon fiber (4’H x 8’L) and the saturation coat, then small rock. The south column was completed at 10:17 a.m.

At this point, we set 1/2” rebar dowels in the slab surrounding the columns and then cleaned up the broken out concrete around the columns and hauled off to Simon Contractors for recy-cling. At 1:00 p.m. the 6 sac, 4,000 psi concrete arrived and we poured and finished the concrete around the columns. We built a curb by the block wall by the north column. At 2:30 p.m., we took down the shoring posts and loaded the truck for demobilization.

Campbell County Detention Center – Gillette, WY

Concrete Stabilization Technologies, Inc., partnered with Campbell County Public Works Department and CEI Engineering, to repair the foundation of the Campbell County Detention Center in Gillette Wyoming during the summer of 2001.

Column Stabilization, Interior Wall Lifting, Floor & Thickened Slab Lifting, Void Fill, and Soil Densification were preformed in the facility to correct a number of settlement issues. Crews began on the outside columns of the building, lifting and stabilizing exterior columns. Using the CST DI process, the soil was stabilized around the columns, voids filled, and columns were placed back on original center. Post testing of the soils in the area proved significant increase in the soil densification, arresting any further settlement issues from occurring. Crews continued work inside the facility, with injections placed to lift and stabilize the floor slabs and lift walls back to grade.

Work performed at the Campbell County Detention Center was done during normal hours of operations, with very minimal disruption to staff or residents of the facility. Security of the residents was not compromised due to the non-intrusive methods and procedures employed by the CST technology. Work was performed in situ, and by utilizing the CST technologies, Campbell County not only saved money by avoiding a rip out and replace scenario, but also avoided the hassle of having to relocate residents and staff. The project was completed on time and below the original estimate. Repairs made to the Campbell County Detention Center over a decade ago, are still holding strong!

Home Foundation Lift – Pine Haven, WY

Concrete Stabilization Technologies, Inc., partnered with Homeowner, Jim Noecker, and Engineer, Ed Scott, P.E. of CEI Engineering to provide a solution for Jim Noecker’s residence in Pine Haven Wyoming. Since construction of the Noecker residence, the home had experienced cracking & separation of the walls, doors sticking, and deformation of the roof. The problems were thought to be caused at least partially by heave or swelling shale in the subdivision where the residence was built.
Dennis Russell with STRATA Geotechnical Engineering performed soil tests. Dennis determined that swelling soils were not a problem, and a plan was developed for repairs using CST’s technologies.

The original estimate for this project was $59,850 plus $8,000 if resistance piers were needed to get the lift of the residence. A second CST truck was used for the final lift of the home. As a result, assistance of resistance piers was not necessary to return the home and floors to grade. The home was lifted approximately three inches on the side with most settlement. Final elevations of the foundation and floors were within 1/2 inch tolerance and soils were stabilized.

The foundation still has the original design and by using the CST technologies, we do not have to worry about having half of the foundation on piers and half on spread footers. This is an important feature of using the CST technologies to prevent future problems in having mixed foundation combining deep foundations (piers) with shallow foundations (footings) on structures.

Final construction cost for repairing and stabilizing was below the original estimate and came in under budget at a total of $55,743.00.

The Homeowner, Jim Noecker, contacted CST in May of 2012 with an update of their residence, stating that they are very impressed! Jim stated that there was “not one new crack or sign of any further move-ment. You guys did a great job and the house seems very stable now. No doors out of square, roof looks normal, and the deck is now level. Glad to see it made it at least one year with the fix and hopefully many more to come. Thanks again for your expertise!” – Jim Noecker

Crescent Electric Supply – Gillette, WY

Structure Characteristics: The building is a single story structure approximately 80 feet by 125 feet in size and consists of wood post and beam framing, such as a pole building. The walls are constructed of wood posts, embedded in concrete piers at approximately 8 feet on center. The posts provide the vertical and lateral support for the walls and roof. The roof is framed with preengineered wood roof trusses. The floor of the building consists of a 6 inch thick reinforced concrete slab on grade. A septic tank and a leach field are situated along the west side of the building.

Problems That Prompted Repair: The building and concrete slab on grade were experiencing settlement. The settlement had caused cracks in the concrete slab on grade and interior finishes of the office area of the building. The majority of settlement occurred along the west side of the building and the concrete slab on grade in the warehouse were cracked the entire length of the building. Cracking ranged 3 to 8 feet east of the west wall. A slab construction joint existing in the center of the building and spans north/south. The joint appeared to have separated as a result of the slab settlement along the building.

Inspection/Evaluation Methods: A structural Observation and Geotechnical Soil Study were performed. Field investigation also performed with the use of a Dynamic Cone Penetrometer (DCP). The primary purpose of this tool is to locate the weak zones in the soils and quantify the comparative degree of ground densification improvement achieved by the deep injection process, as exhibited by the increased number of percussive blows required to penetrate the treated soil mass, when compared to a pre-injection test performed within the confines of the treated mass.

Test Results: The geotechnical study and structural observation indicated that the soils underlying the foundation and concrete slab on grade consisted of soft clays with considerably high moisture content. These soils are notorious for settlement and collapse upon wetting. It was determined that the settlement had high potential to continue if the problem was not addressed. Separation of the slab joint was determined to have been caused by the settlement of underlying soils. DCP Test results indicated weak soils at depths of 7 feet.

Causes of Deterioration: Deterioration was caused by a leak from a collapsed water tank in 2008 west of the building, effluent from the septic system, surface runoff, or a combination of these influences. Soft clay soils surrounding and beneath the structure and slab contributed to the settlement and associated damaged slab and interior finishes of the building.

Repair System Selection: Selection of the repair system was based on recommendations resulting from structural evaluation of the building. Due to the soil conditions and probability of future settlement, “Deep Injection”, using expanding structural Geo-Polymer, was chosen for correcting the settlement issues.
Site Preparation: Penetrometer testing was performed and reviewed. Mapping of the warehouse floor was completed. Profiles for settlement and finish target elevations were performed.

Demolition Method: No demolition of the existing concrete slab on grade was necessary due to
the utilization of the “internationally patented Geo-polymer injection system”. All soil remediation work was completed “In Situ”.

Surface Preparation: Surface preparation of the slab, and soil surrounding the outer perimeter of the building, prior to injecting was unnecessary. This is due to the unique nature of the expanding Geo-Polymer technology utilized. Minimal cleanup of the joint area was performed before epoxy was injected and caulking repairs were performed in the west joints and wide joint in the center of the warehouse. The crack repair and joint sealing was performed in the floor slab. Cracks were mechanically routed and gravity fed structural epoxy was injected into the cracks. Caulking of the joints was completed using a urethane sealant as specified by the engineer. Approximately 136 linear feet of cracks and approximately 124 linear feet of control joints were primed and caulked.

Application Method Selection: Repairs required utilization of a specialty technique. The foundation type (posts embedded in shallow concrete piers) does not lend itself well to helical pier stabilization. Stabilization of the underlying soils, individual concrete piers, and the concrete slab on grade itself needed to be modified in order to arrest future settlement. Therefore, the best method of application and method of repair was determined to be the injection of expanding structural Geo-Polymer.

Repair Process Execution: Initial testing of the soils were performed and analyzed to determine injection depths necessary to stabilize the underlying soil structure. Areas to be addressed were mapped and injection ports were prepared beforehand to accommodate frozen soil conditions at the time of repair. The injection of the patented Geo-Polymer material was used to penetrate deeply into the sub grade at depths of an estimated seven feet. Voids beneath the slabs were filled, and slabs lifted back to original elevations. Sub grade soils were stabilized using this Internationally Patented Technology. Deep Injection permanently altered the soil structure, thus stabilizing and preventing future settlement. Once soils were treated, the slab joints were sealed and caulked with epoxy as specified by the project engineer.

Structural floor repair: Sub contractor, gravity fed low viscosity epoxy into the floor cracks to re- establish the original monolithic strength.
Control joint sealants: Sub contractor mechanically cleaned the sides of the existing control joint and caulked with urethane primer and sealant.

Unforeseen Conditions Found: The work was performed in January which added concern for frozen ground and cold temperatures. The settlement originated below frost line. The Project Superintendent made additional efforts to keep equipment warm. The exothermic reaction of the Geo-polymer materials provided further protection against frozen conditions.

It was decided to perform the work on the client’s preferred schedule if possible. One of the unique characteristics of the Geo-Polymer is that it will not freeze during injections (it is not a water based material). Since unit weight was minimized and polymer did not add burden to weakened sub- grade, frozen ground and cold temps did not interfere with the work schedule.

Special Features and benefits of Geo-Polymer Deep Injection Repair Process:

  • Eliminated cause of settlement and future potential settlement resulting from the water spill.
  • Raised building and slabs to original elevation.
  • Saved concrete slab, and interior finish from further damage.
  • No downtime to business, timely, safe, clean.
  • All work done from above ground without excavation, In-Situ.
  • The Business was able to remain fully open during repairs with very little disruption to activities.
  • Floor sub-grade was restored to give full support for heavy forklift traffic.
  • Structural repair of floors was completed with full co-ordination of warehouse use.
  • Project was completed using permanent and economical, “Deep Injection” of Geo-Polymer.

Battle Mountain Highway Frost Heave – Encampment, WY

Abstract

This project investigated a novel procedure to reduce or prevent subgrade freezing non-destructively by injecting a two part rigid polymer foam at the top of the subgrade. Controlled injection of a CST expanding structural polymer foam created a continuous three inch thick layer of insulation that significantly reduced the heat loss from the deeper soil and prevented the upward movement of water from the warmer regime under the foam to the upper frozen regime above the foam, preventing segregational freezing in the upper zone. The construction time for the 170 foot section was one week for injection and milling the surface. Construction was contained in one lane, leaving a lane open for the entire duration without a detour, increasing safety and minimizing impact for the driving public.

Additionally, a procedure is developed for estimating the thickness of the foam layer required for other sites with different average temperatures.

Objectives

  • Can foam be injected nondestructively to level the road surface and make the road safer to drive without full reconstruction?
  • Will the foam layer provide a sufficient thermal barrier to prevent heat loss and reduce frost heave?
  • Will a continuous layer of foam create a barrier to vertical water movement and reduce spring thaw degradation?

Background

  • This section of Highway WY-70 was constructed in the early 1980’s. The highway crosses a crystalline caprock ridge outcrop that the contractor had difficulty removing.
  • The contractor was allowed to alter the design to leave the ridge intact and place three feet of compacted silty sand fill over the rock with the sub-base and base course on top over a distance of 150 feet.
  • Lateral drains and cross drains have not completely removed the water under the pavement. .
  • The combination of a frost susceptible silty sand, extended cold temperatures and the availability of water provide the necessary pieces for segregational frost heave.
  • Measured heaves of three inches and reported heaves of four to six inches created a dangerous bump over a short distance of 75 feet. In addition, a drain installed over the caprock was backfilled with non-heaving backfill which created a dip significant enough to flip snowmobiles off of trailers when traveling faster than the posted speed.

Proposed Solution

A standard technique to control frost heave is to place several layers of foam insulation panels below the sub-base course. This requires a full reconstruction of the site. A process was proposed to inject a three inch thick layer of a two part structural polymer foam at the bottom of the sub-base without removing the existing road surface.

Construction

Concrete Stabilization Technologies, Inc (CST) injected the foam through a series of 3/4 inch diameter, 18 inch deep holes drilled through the road surface on a 6 foot grid. Three inches of foam were injected over the area with the most heave. Additional injections provided tapered zones to smooth the transition from the original road surface to the full thickness zone.

The process required two trucks and a four person crew to complete the work in four days. All the work was performed in one traffic lane at a time while keeping the other lane open for traffic. Because of the poor road surface before the injection, the surface was milled at a later time. The subsequent road surface was sufficiently leveled to make the mediation unnoticeable.

Injection and Instrumentation Locations

  • Thirty survey points at 10 feet centers were measured over a 300 foot distance on five rows located at:
    • The centerline of the road,
    • The centers of the two lanes, and
    • The north and south edges of the lanes.
  • Five piezometers located in the north and south shoulders of the road.
  • Six boreholes with thermistors to measure the temperatures in the soil profile. One thermistor in each hole was located:
    • Above the injection point and the foam layer,
    • Below the foam layer, and
    • Ten inches below the foam.
    • One or two other thermistors were located lower depending on the depth to bedrock.

Results

The upper figure shows the measured elevation changes from the summer baseline along the center of the east bound lane.

    • The thin solid black line shows the heave in January prior to the injection of the foam. The dip at STA 2+10 is the location of a French drain that was backfilled with non-heaving sand.

 

    • The heavy black line shows the foam thickness averaging 3 inches with tapered edges to the east (STA 2+40 to 2+70) and west (STA 1+70 to 1+40).

 

    • The colored lines show the elevation differences in the two winters after injection. The total heave over the treated zone is generally less than 0.5 inches and is less than the natural heave outside the treated zone. The lower figure

 

    • shows the elevation changes along the centerline of the west bound lane. Substantial heave is shown where the foam thickness is only 1.0 to 1.5 inches.

 

 

The upper figure shows the measured elevation changes from the summer baseline along the center of the east bound lane.

  • The thin solid black line shows the heave in January prior to the injection of the foam. The dip at STA 2+10 is the location of a French drain that was backfilled with non-heaving sand.
  • The heavy black line shows the foam thickness averaging 3 inches with tapered edges to the east (STA 2+40 to 2+70) and west (STA 1+70 to 1+40).
  • The colored lines show the elevation differences in the two winters after injection. The total heave over the treated zone is generally less than 0.5 inches and is less than the natural heave outside the treated zone. The lower figure
  • shows the elevation changes along the centerline of the west bound lane. Substantial heave is shown where the foam thickness is only 1.0 to 1.5 inches.

The lower figure shows the elevation changes along the centerline of the west bound lane. Substantial heave is shown where the foam thickness is only 1.0 to 1.5 inches.

This figure shows the elevation changes along the centerline of the west bound lane. Substantial heave is shown where the foam thickness is only 1.0 to 1.5 inches.

The heavy black line in the below graph shows the thickness of the foam being about 3 inches under the east bound lane and tapering to zero under the west bound lane.

  • The thin colored line is the measured heave in the year before construction.
  • The other colored lines are the measured heaves during the two winters after construction.
  • The heave on the south edge (-12 feet) is caused by edge effects and local freezing.
The heavy black line in this graph shows the thickness of the foam being about 3 inches under the east bound lane and tapering to zero under the west bound lane. The thin colored line is the measured heave in the year before construction. The other colored lines are the measured heaves during the two winters after construction. The heave on the south edge (-12 feet) is caused by edge effects and local freezing.

Conclusions

  • Transferability of the control strategy is possible if the weather conditions in the new corridor are similar (i.e. defined by the same weather variables) to the corridor where the control strategy was developed.
  • It would be beneficial to train the decision trees with the storm data collected at the new corridor.
  • The system should be monitored till it is recommending desirable speed limits based on real time weather and traffic information.
  • From the simulation results it is observed that proposed control strategy is performing slightly better than WYDOT’s manual protocol.
  • If the control strategy is to transfer a completely new corridor, it would be ideal to collect some storm data and train the decision trees before using the control strategy in real time.