Soil Nail Wall 4 Production Nail Installation Begins

After completion of verification nail testing and waiting for the proper soil nail materials to be delivered, Teichert Construction began installation of production nails at the Soil Nail Wall 4. The results of verification nail testing confirmed the appropriate soil nail lengths as well as allowed for a redesign of the nail layout for ease of construction. Six inch diameter holes are drilled into the hillside to design lengths prior to installation of the actual steel nail. Grouting of the nail must take place immediately after drilling to prevent cave-ins. Wire mesh and steel reinforcement are then installed along the soil cut face prior to the installation of the shotcrete wall facing.

Installed soil nails along with the Soil Nail Wall 4 cut face extend outward. The black geocomposite drain strips are installed against the soil and will be extended down as each soil nail lift is excavated.

Reinforcing steel bars extend above the cut face to eventually support the extension of a concrete cantilever wall.

Shotcrete installation operation at Soil Nail Wall 4.

A soil nail extends through the reinforcing steel, wire mesh, and initial layer of shotcrete.

Soldier Pile Wall 2 Work Begins

Teichert Construction began construction of Soldier Pile Wall 2 at the southern project limit. Besides the use of soil nails to secure the hillside along Vasco Rd, soldier pile wall retaining systems will be used to stabilize the minor hillside cuts. Approximately 20 to 30 ft deep holes are drilled to accommodate concrete cast in place steel piles. Timber lagging will be installed in between the steel piles prior to the final concrete facing wall. Upon completion Soldier Pile Wall 2 will be approximately 12 ft tall at the highest location.

Drilling rig staged at Soldier Pile Wall 2 location.

Drilling down to pile tip elevation.

Steel pile secured in the proper location prior to concrete pour.

Brushy Creek Bridge Abutments Complete

Teichert Construction completed the Brushy Creek Bridge abutments by pouring them in early August. The abutments secure the bridge structure itself to the footing foundation. Steel reinforcement extends from the footing up into the abutment, which will eventually connect to the bridge deck.

View of Abutment 1.

Falsework installation at Abutment 2.

Laying out falsework girders at Abutment 1.

Brushy Creek Bridge Abutment Work Begins

Earlier this past week, Teichert Construction completed the Brushy Creek Bridge concrete footing pour. Upon completion of this operation, construction workers stripped the wooden forms to expose the concrete footing and began erecting the abutment forms. As this operation proceeds, one can visualize the bridge structure itself as the foundation begins to come up. Reinforcing steel (vertical bars) were installed in the footing to extend up into the abutments to secure the bridge to the footing foundation.

Stripping the footing forms at Abutment 2.

View of Abutment 2 footing (foreground) with Abutment 1 forms in the distance.

Abutment 1 forms being erected.

Brushy Creek Bridge Footing Pour

This past week Teichert Construction completed their first major concrete operation, Brushy Creek Bridge footing pour. A concrete pumping truck set up between the two bridge abutment footings while concrete trucks lined up to supply the materials. County Inspection staff monitored the pour itself while County Materials Testing laboratory staff verified the material quality and obtained samples for further quality assurance sampling.

Concrete being pumped into the Abutment 1 footing form.

Concrete at the Abutment 1 footing, lowest step.

County Materials Testing Laboratory Staff obtaining concrete samples onsite for quality assurance compressive strength testing.

Bridge Footings and Shotcrete Test Panels

This past week Teichert Construction began forming the bridge footings and installing the rebar in anticipation for a concrete pour next week. The recently driven piles are anchored to the footing via rebar which also extend up into the bridge abutments. Pre production soil nail wall work continued this pass week with additional verification nail testing and pre construction shotcrete test panels. Upon installation of production soil nails, shotcrete will be used to in conjunction with wire mesh and reinforcing steel to form the retaining wall face itself. This will maintain the wall face integrity while the soil nails stabilize the hillside behind the retaining wall. Test panels of shotcrete are built by Teichert Construction prior to actual wall construction for Construction Inspection to verify the quality of shotcrete workmanship and confirm its strength properties prior to production.

Concrete forms and rebar at the Abutment 1 stepped footing.

Concrete forms and rebar at the Abutment 2 footing.

Construction of a shotcrete test panel (with reinforcing steel).

Pre production shotcrete at a verification nail face.

Pile Driving and Verification Nails

This past week Teichert Construction completed pile driving installation for the abutment foundation at Brushy Creek. Forty-five to 60 ft long steel H-beams were driven into the soil beneath the abutment footing to provide a secure and stable foundation for the bridge widening. The piles are struck by a pile hammer with sufficient energy to drive the steel through the surrounding creek alluvium and deep into bedrock. Observation of the pile driving operations by County Inspection confirmed the existence of a hard sandstone layer (at shallow depths at the northern abutment) within the foundation's geological layer. This rock stratification provides a good substrate for the piles to secure the bridge footing and abutment. Other construction operations last week included the completion of exploratory drilling for the soil nail retaining walls at the northern and southern project limits. Verification nails were installed to confirm County Design's soil assumptions for the retaining walls. Soil nail retaining wall systems will be constructed as part of the Vasco Rd Safety Improvements project. "Soil nails" of various lengths are installed in bored holes along the hillside. The nails are then grouted in place with high strength concrete. As a complete system, the friction created between the grouted nails and existing soils secure the hillside and prevent slides from occurring. The current verification nail process consists of installing test nails at various locations to identify current soil conditions and quantifying the load the designed soil nails can sustain. Upon completion of this verification process, the "production" nails can be re-designed (shortened) to reduce costs if the existing soil conditions are better than originally anticipated.

Teichert Construction pile driving rig setting up at the southern abutment.

Pile driving at the southern abutment.

Piles driven (at the northern abutment) into the existing sandstone layer, which encountered competent bedrock at shallower depths than expected.

Teichert Construction drill rig beginning to bore for a verification soil nail.

Inclinometers and Bridge Foundation Work Begins

This week Teichert Construction started to access the hillside north of Brushy Creek bridge to prepare for installation of 2 retaining wall structures. Part of this preparation work is exploratory drilling and inclinometer installation. Exploratory drilling in the hillside is necessary for County engineers to confirm the existing hillside soil conditions and make any necessary modifications to the retaining wall design prior to actual installation. Inclinometers are plastic casings (90 ft in depth) installed on the hillside that are located behind the retaining wall location that measure any hillside movement. Measuring any "hillside" creep is necessary as part of the overall installation process to ensure that retaining wall construction isn't affecting slope stability and as well as providing long term maintenance monitoring. Progress continues with the Brushy Creek bridge widening effort as Teichert Construction crews excavated for foundation footings at the south abutment. This operation will be followed with pile driving, anticipated to begin next week (6/28/10).

Looking north at an inclinometer location. Note, the portion of the hillside, leftside in the picture (down slope) will be excavated for the retaining wall itself.

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Inclinometer casing.

Teichert Construction crew excavating the footing for the southern abutment.

EXPECT DELAYS: 6/24

Teichert Construction will be implementing 1 lane traffic control along Vasco Rd (at Brushy Creek bridge) on Thursday, 6/24/10, from 9 am to 3 pm. Commuters should expect delays while County biologists work on the bridge to re attach netting to prevent birds from nesting on the bridge structure itself. Surprisingly, the concrete angle points on bridges are prime habitat for birds to form "mud" nests. Birds that form new homes on the bridge may delay the project so County biologists monitor and implement measures to prevent birds from establishing nests. On Brushy Creek bridge, netting is installed under the bridge at the abutments and along the edge of deck. Due to the high winds, netting must be constantly maintained and reattached to prevent it from blowing onto the roadway itself or falling into the creek, which is sensitive habitat.

Netting installed under Brushy Creek bridge at the angle point created by the existing abutment and superstructure.

Brushy Creek Bridge Demolition

Teichert Construction crews completed the majority of the Brushy Creek Bridge demolition this week. The demolition operations were limited to the existing barrier rail on the bridge along northbound Brushy Creek Bridge. A minimal portion of the existing deck was removed so the final concrete pour (closure pour) will transition the existing bridge deck to the new bridge grades. Portions of the exposed rebar on the existing bridge will connect to rebar/concrete in portions of the new bridge widening.

View of the existing bridge with the northbound barrier rail removed and exposed rebar.

County Construction Inspection reviews the operation to confirm the limits of demolition and ensure that the existing structure remains undamaged.