trenchless projects
Workhorse Machine makes progress in Difficult Ground
A rebuilt Robbins 3.5 m (11.5 ft) diameter Main Beam TBM has yet another milestone to add to its storied career: an unexpected cavern, encountered and successfully passed through.
Contractor Eiffage Civil Engineering is operating the machine, which launched in 2017 for the Galerie des Janots project in La Ciotat, France. The cavern, studded with stalactites and stalagmites and measuring 8,000 cubic meters (283,000 cubic ft) in size, was grazed on the tunneling operation’s left side. The crew named the cavern “grotte Marie Lesimple” after their site geologist.
“We hit the corner of it. To cross it, we had to erect a 4 m (13 ft) high wall of concrete so the TBM would have something to grip against,” explained Marc Dhiersat, Project Director of Galerie des Janots for Eiffage. A small door allowed access inside the cavity, which formed naturally at a point 60 m (200 ft) below the surface. The TBM was started up and was able to successfully navigate out of the cavern in eight strokes without significant downtime to the operation.
“This is certainly unusual, to come across a cavern of this size and significance. It is somewhat related to the geology, with karstic and volcanic formations having the most potential for underground cavities,” said Detlef Jordan, Robbins Sales Manager Europe. Karst cavities were a known risk during the bore, but the cavern was not shown in vertical borehole reports conducted from the surface along the alignment.
A further 1.8 km (1.1 mi) will need to be tunneled before the 2.8 km (1.7 mi) tunnel is complete. “It is possible there could be more unknown caverns. We have a geotechnical BEAM system on the machine, and are conducting probe drilling, shotcreting, and maintenance in a separate shift,” said Dhiersat. The BEAM system, standing for Bore-tunneling Electrical Ahead Monitoring, is a ground prediction technique using focused electricity-induced polarization to detect anomalies ahead of the TBM.
The crew encountered difficult ground conditions early on in the bore, consisting of limestone with powdery clays. “When the machine is boring it does well. We have good production and it’s a good machine for hard rock. But sometimes it’s not hard rock that we encounter,” said Dhiersat. The weak rock and clay conditions necessitated ground support including resin-anchored bolts and rings in bad ground, topped with a 10 to 15 cm (4 to 6 in) thick layer of shotcrete. Despite five months of poor ground conditions, Eiffage is optimistic that conditions will improve and the tunnel will be complete in the next four to five months.
Galerie des Janots is one of the fourteen operations designed to save water and protect resources, which are being carried out by the Aix-Marseille-Provence metropolis, the water agency Rhône Mediterranean Corsica, and the State Government. The future Janots gallery will replace existing pipelines currently located in a railway tunnel—these original pipes have significant deficiencies with estimated water losses of 500,000 cubic meters (132 million gallons) per year.
The completed tunnel will pass under Le Parc National des Calanques, with cover between 15 and 180 meters (50 to 600 ft), in order to replace the pipes that are currently being utilized for the water supply networks. “The current pipes have a capacity of transit limited to 330 liters (87 gallons) per second, which is largely insufficient in the summer period. The objective of the operation is to secure the lines and increase capacity to 440 liters (116 gallons) per second,” said Dhiersat.
Image 1: The Robbins TBM encountered an unexpected cavern measuring 8,000 cubic meters (283,000 cubic ft) in size.
Image 2: Despite continued difficult ground, contractor Eiffage is confident in the Robbins TBM performance and optimistic that the tunnel can be completed in four to five months.
Industry News, trenchless projects
The University of Central Florida purchased a Vac-Tron AIR 373 SDT vacuum excavator in 2016 and shared the benefits this unit has created for the facilities.
“We didn’t have an initiative on campus to do soft digging and locating, so we went looking for a solution and Vac-Tron came out to be the best value for our money,” said Anthony Lugo, UCF Utility Supervisor.
Project Descriptions
Some of the initiatives that UCF utility workers handle daily include identifying and mapping the location of utility lines.
“We have a lot of old utility lines in the ground that haven’t been located in many decades. They have never been marked properly, and it is our job to find them, mark them, and put them on the map. Finding those lines can be time consuming and intrusive to the property. But the biggest obstacle, when you are part of the utility crew, is safety, you don’t want to hit electrical lines with a shovel.” said Lugo.
The utility crew is also responsible for emergency water line breaks. “Prepping the area for a water line break repair is a tedious job and time is of the essence.” added Lugo.
Solution
The Vac-Tron AIR 373 SDT vacuum excavation unit. The UCF AIR unit is powered by an 83 HP Yanmar diesel engine and comes standard with a 300-gallon debris tank, air pressure of 150 CFM at 170 PSI, hydraulically operated full-open rear door with auto engage safety latch, and one 100-gallon water tank. This unit also has the Patented Remote Debris Tank, which collects the dry material and then can be positioned back over the hole to put back into place without causing much disruption to the surroundings.
Upgrading from traditional methods of excavation, an excavator or hand shovel, to a Vac-Tron unit has greatly increased efficiency for the UCF utility crew. “It made things faster, it made things safer. It saves us a lot of time, what used to take 4-6 hours, now only takes 1-2 hours. We aren’t spending any unnecessary time doing a job.” said Lugo.
“The biggest thing is safety, safety is the key aspect. The Vac-Tron unit allows us to be safe in an expedited fashion. This is considered soft digging, which is just basically pulling the dirt out of the ground so you’re not striking anything. You could hit a high voltage electrical line, high pressure water or gas line, any number of things, and the Vac-Tron AIR unit helps to eliminate that.” stated Lugo.
Results
- Potholing quickly to locate old utility lines for identification and mapping
- 4-6 hour projects now take 1-2 hours
- Respond quicker to water line breaks
- Quicker repairs to water line breaks with the power of the vacuum excavator removing debris
- Cleaning of storm drains in an efficient way
- Wastewater spills quickly cleaned up
- Less intrusive to the campus’ infrastructure
- Less disruption to the environment
Multiple departments at UCF are also using the Vac-Tron unit. For example, the Landscaping and Recreation crew uses it to clean out storm drains, and the Design and Construction team will request it to locate lines for future construction on the campus. UCF has found multiple uses for the Vac-Tron unit. “This has been a godsend because we can actually find things without being as intrusive to the campus’ infrastructure. For the value we are getting, it has turned out to be priceless!” added Lugo.
Check out the full interview and video footage of the unit in action at UCF https://www.vactron.com/utility-crew-ucf-vacuum-excavation-case-study/.
Industry News, trenchless projects
HDD with Fusible PVC® pipe saves Commission $200,000
Overview
The Howard County Regional Water Commission (HCRWC) was formed in April 2008 with the intent of being a wholesale water provider for the City of New Franklin, the City of Fayette and Howard County CPWSD #1. MECO Engineering has been involved with HCRWC since day one in an effort to assist with design and funding of the required infrastructure. The necessary infrastructure consisted of an alluvial well field, water treatment plant, water tower and distribution mains.
The distribution system design consisted of approximately 68,000 feet of 12-inch waterline, 1,200 feet of 10-inch waterline and 1,200 feet of 6-inch waterline with the majority of the pipe to be installed by conventional open-cut installation. However, there was still a significant amount of the 12-inch waterline that could not be installed by conventional open-cut construction
based on environmental concerns such as creek crossings or as a result of private property disturbance agreements tied to the issuance of easements. As a result, approximately 8,800 feet of the 12-inch line would need to be installed using horizontal
directional drilling (HDD) installation methodology.
The original plans and specifications included HDPE pipe for the HDD portions of the job. However, during the bid process, Fusible PVC® pipe was allowed as an alternate material for the HDD sections. As a benefit, Fusible PVC® pipe would be able to match the bell-and-spigot PVC pipe being installed in the open cut portions of the job, while the HDPE pipe would need to be upsized in order to provide the same inside diameter. Ultimately the project allowed for two material options in the HDD portion of the job, 12-inch DR 21 Fusible PVC® pipe and 14-inch DR 9 HDPE pipe.
Bids were opened on July 8, 2015 and based on utilizing Fusible PVC® pipe for the HDD sections, C&S Construction out of New London, Missouri was the low bidder. In fact, their bid provided a $200,000 savings due to installing Fusible PVC® pipe instead of the HDPE pipe that was originally specified.
The distribution system portion of the work lasted approximately eight months with all of the Fusible PVC® pipe being installed and tested without any issues.
“We have installed Fusible PVC® pipe on multiple jobs. We really like the way it performs. For this project it allowed us to drill a smaller hole when compared to the HDPE option. Since most of these drills occurred in rock, a smaller hole provides substantial savings of both time and money.” Clinton Ray, Owner Ray’s Construction
Project Story submitted by Underground Solutions, Inc., 858.679.9551
www.undergroundsolutions.com
Industry News, trenchless projects
Fusible PVC® pipe for fault crossings, curvilinear alignments and restrained joint sections
The Los Carneros Water District Recycled Water Project was designed t
o provide the Los Carneros Water District (LCWD) service area, located just south of Napa, California, with a reliable recycled water supply. This system is used to offset groundwater use during the summer irrigation season allowing more potable water to be available for critical consumption.
This project included the construction of 8.6 miles of 6- to 20-inch diameter recycled water pipelines to provide a distribution system which supplies recycled water to portions of residential landscape and agricultural land within LCWD. The recycled water will be sourced from the Napa Sanitation District’s existing Soscol Wastewater Treatment Plant (WWTP). The system is located within existing road right of ways and did not require new pump stations or storage facilities. All storage and pumping requirements are met using Napa Sanitation District’s Soscol WWTP facility. The project serves approximately 115 parcels or 3,800 acres of irrigable land within the District with approximately 1,300 acre-feet of recycled water per year. Irrigation water users connect their own irrigation systems and facilities to various turnouts on the system to provide the recycled water to their private lands and fields.
The District bid Fusible PVC® pipe, with its thermally butt-fused joint, as the base bid for restrained joint areas, fault crossings and curvilinear alignments that exceeded the allowable deflection of conventional bell-and-spigot pipe. The District also allowed mechanically restrained bell-and-spigot PVC pipe, using bell restrainers with 316 stainless steel hardware for the restrained pipe lengths. The bell restrainer also needed to be wrapped in an AWWA approved four-part petrolatum tape wrap system for corrosion control. JMB Construction, the low bidder on the project, elected to use Fusible PVC® pipe in the restrained areas as the most cost-effective option.
Approximately 20 percent of the pipeline was constructed with Fusible PVC® pipe. Fusible PVC® pipe addressed several specific design elements that conventional bell-and-spigot PVC pipe could not. These included seismic fault crossings where the fusion joint provides a fully restrained joint that resists ‘pull-out’ during earth movement. It also included curvilinear horizontal and vertical pipeline alignments that
exceed the allowable deflection capability of bell-and-spigot joining technology. Finally, it was used as the non-corrosive restrained-joint pipeline required to resist axial thrust at fittings and appurtenances along the pipeline. Fusible PVC® pipe is the only PVC restrained joint meets the requirements of the AWWA C605 PVC pressure pipe installation standard, regardless of pipe size.
JMB Construction’s Sean Quinn commented, “JMB has utilized and installed Fusible PVC® pipe on many projects including HDD, sliplining, pipe bursting and open cut installations. This is another project in a long line of successful projects using Fusible PVC® pipe.”
Image 1: Placing the restrained, Fusible PVC® pipe length under existing utility crossings
Image 2: JMB used standard, mechanical joint ductile iron fittings with restrainer glands to assemble the pipe system
trenchless projects
Expansive Metro Project Will Provide Transportation Within Rapidly Developing City
On Tuesday, October 31, 2017, a 6.65 m (21.8 ft) diameter Robbins EPB TBM broke through at Chennai Metro, making this the third tunnel the machine has bored for the project and for contractor Afcons Infrastructure Ltd. The three separate bores for the EPB are part of an increasing trend, as many Robbins EPBs have been used on multiple tunnel drives with good performance. Robbins EPBs are built one third heavier than any other EPB on the market and are designed for 10,000 hours of usable life, making them ideal machines for use over many kilometers. “Robbins is known for designing resilient machines,” said Mr. Gopal Dey, Afcons Senior Manager. “For this project, we needed a machine that was specifically tailored to project conditions from soft clay to mixed ground with rock. Robbins EPB TBMs have unique design features that optimize the machine for the geology.”
After completing its original twin tunnels, the EPB was refurbished in preparation to bore its latest 1.8 km (1.1 mi) section. During refurbishment, the inner seal greasing system was changed from auto to manual mode and the foam nozzle system was modified. These changes optimized the machine for excavation in the highly variable mixed face conditions encountered in the first two tunnels.
The EPB was launched on February 3, earlier this year. According to contractor Afcons, the machine faced a major challenge right out of the gate. “When the TBM came out of the launching shaft, a few rings were erected and then the machine had to cross a live railway track, which meant there would be a possibility of ground settlement,” said Afcons Director, Mr. Manivannan. “At this stage, we had to closely monitor TBM face pressure and advance the machine at a uniform rate to ensure proper primary grouting.” The bore’s geology mainly consisted of clayey sand and about 60 meters (197 ft) of mixed ground.
“We [Afcons] chose this machine for this project due to the underground geology in Chennai, which continuously changes from soil to mixed ground,” said Mr. Dey. “We also liked that Robbins EPB machines are designed with active articulation to allow the machine to turn or steer with ease.” During active articulation, thrust cylinders react evenly against the entire circumference of the tunnel lining, even in a curve—a design that eliminates the problem of tunnel lining deformation. “This feature enabled the machine to negotiate through well-controlled conditions,” added Mr. Manivannan.
With all three tunnels, Robbins Field Service members were on location to assist and support as required. During the course of each bore, Robbins was there to advise Afcons on how best to maneuver through challenging ground and provide instruction for machine operation. The ability of the contractor and manufacturer to work well together, as Robbins and Afcons have throughout their contracts, was critical to the good advance rates. The result was a robust machine that advanced at rates of 80 mm (3 in) per minute in challenging conditions.
This latest tunnel connects multiple stations along the metro line, starting from Washermenpet through to Sir Theagaraya and to Kurukpet. The Chennai Metro Project will provide much needed transportation to a rapidly developing city.
Image 1: On Tuesday, October 31, 2017 a 6.65 m (21.8 ft) Robbins EPB made its third breakthrough at India’s Chennai Metro.
Image 2: Robbins and contractor Afcons celebrate the breakthrough and good performance of the EPB, which achieved rates up to 80 mm (3 in) per minute in mixed ground conditions.
Desiree Willis
Technical Writer
Email: willisd@robbinstbm.com
Direct: 253.872.4490
The Robbins Company
Industry News, trenchless projects
SANTA CRUZ ACCOMPLISHES EMERGENCY HORIZONTAL DIRECTIONAL DRILL FOR
LOMBARDI GULCH CROSSING
HDD provides a rapid and reliable way to replace aging steel pipeline
Overview
The City of Santa Cruz Water Department (SCWD) has long anticipated the need to assess, design and build a new pipeline system as part of the existing North Coast System (NCS) which delivers raw water to their water treatment plant. The existing NCS is a series of stream diversion structures and collection
conduits and includes approximately 16 miles of pipelines that are nearing, or have exceeded, their design life and must be replaced. The replacement pipeline is a series of phased projects and will provide a water delivery system that will be reliable for the next fifty years or more.
Phase 3 of the overall initiative included the replacement of 18,600 feet of primarily 24-inch diameter pipe using open cut methodology. Additionally, five trenchless crossings, one horizontal directional drill (HDD) crossing under sensitive environmental habitats and four horizontal auger bores crossing under California Department of Transportation and railroad right-of-ways were included in Phase 3.
In 2015, this phase of the NCS project had been designed but had not gone out to bid when a failure of a 1,200-foot critical section of the existing steel pipeline at the Lombardi Creek Crossing location prompted SCWD to schedule that section for immediate replacement. Site conditions at this location required replacing the pipeline using HDD installation methodology. Its location within the Wilder Ranch State Park elevated environmental concerns because the park has strong biological, scenic, cultural and recreational values.
The replacement of the Lombardi Creek crossing began in late 2015 after selecting the HDD Company from Granite Bay, California to be the contractor. The actual drill alignment length was approximately 1,300 feet with an elevation change of approximately 60 feet. Entry and exit angles were approximately 10 degrees. The final alignment was 25 feet below the bottom of the creek. 24-inch DR 18 Fusible PVC®
pipe was selected as the replacement pipe. Overall, the drill alignment and bore preparation took four weeks. While the bore hole was being drilled and reamed, the Fusible PVC® pipe was fused by Underground Solutions. Once the bore hole was prepared, the Fusible PVC® pipe was pulled into place,
a process that took approximately 8 hours. The replacement project took two months from mobilization to pressure test and the replacement pipe was placed into service after completion. This new segment will be tied into the new NCS Phase 3 pipeline when it is complete.
Project Manager Kevin Crossly stated, “The Lombardi Gulch HDD Undercrossing is the largest and longest installation of Fusible PVC® pipe to date for the City of Santa Cruz. The City was very pleased during all phases of the project with Underground Solutions which provided technical support solutions during design of the project. When the City experienced the 0.5 MGD leak and fast tracked the construction phase, Underground Solutions was responsive to the project requirements to secure, fabricate, deliver and fuse the 1,300 LF of pipe that was ultimately installed on a very aggressive schedule of approximately eight weeks. Fusible PVC® pipe is a great product that Underground Solutions will support and stand behind. We will definitely consider using Fusible PVC® pipe on future projects.”
A rebuilt Robbins 3.5 m (11.5 ft) diameter Main Beam TBM has yet another milestone to add to its storied career: an unexpected cavern, encountered and successfully passed through.
“This is certainly unusual, to come across a cavern of this size and significance. It is somewhat related to the geology, with karstic and volcanic formations having the most potential for underground cavities,” said Detlef Jordan, Robbins Sales Manager Europe. Karst cavities were a known risk during the bore, but the cavern was not shown in vertical borehole reports conducted from the surface along the alignment.
