(3/20/2014) Geofoam Provides Solution for Underground Coal Mine Tunnel
Denver, CO - About 30 miles east of Salina, Utah, nestled in the western bituminous region of Sevier County, is Convulsion Canyon. This is home for a productive Southern Utah Fuel Co. underground coal mine, where a longwall mining system and continuous miner units extract more than 6 million tons of coal each year.
New haulage and belt line tunnels were constructed in 2011 to increase production. In the fall of 2012, the mining company determined that it would be advantageous to construct a storage building above the underground tunnels. But the haulage tunnel, which was buried an average of 12ft below the existing grade, was not adequate to support the necessary loads.
The mine assigned the project to Jones & Demille Engineering, where project manager Kendrick L. Thomas, P.E., took the helm. According to Thomas, several options were evaluated including:
• A micropile and grade beam system.
• A structural retrofit of the tunnel.
• Geofoam.
“Calculations for the micropile and grade beam system showed that it was a feasible option,” Thomas said. “Calculations for the structural retrofit were performed as a quick check and indicated that it would be very difficult to get that option to work structurally. An analysis of the cost and construction schedule for each option revealed that geofoam could be installed much quicker and for far less money than the other two,” Thomas said.
“During the decision-making process, we could see that geofoam would also give us the most flexibility for the positioning of the building. The mine was looking at several possible locations for the building and geofoam allowed them the flexibility to position the building any way they wanted, whereas micropiles and grade beams would have tied the building location down to one spot that they were not sure they wanted to stick with,” Thomas explained.
The installation of expanded polystyrene (EPS) 29 geofoam, with a termite resistance treatment, looked to be a good solution. So the construction company installed 28,000ft³ of the termite-resistant EPS 29 geofoam. In keeping with the mine’s commitment to environmental stewardship, the geofoam was manufactured with 5% recycled content, then it was transported from the Murray, Utah, plant to the mine site.
It is unusual for a client to ask for recycled content in geofoam applications. Although we can manufacture EPS with up to 35% recycled content, recycled EPS is more often used in packaging applications. The recycled EPS geofoam is the most environmentally sound product possible for this application.
EPS geofoam blocks were installed 8ft deep for a length of 80ft, and two layers of the blocks were stacked 6ft deep for the width of 50ft to reduce weight on the underground tunnel. A 6-in. concrete load distribution slab was then placed on the top surface of the geofoam.
Each project using Foam-Control EPS Geofoam should be designed by a professional engineer. The engineer or project specifications should be consulted to determine the ASTM D6817 Type required for the project loading conditions.
For most applications, long-term design loads should not exceed the linear elastic range of Foam-Control EPS Geofoam. Combined live and dead load stresses should not exceed the compressive resistance at 1% strain. In general earthwork applications (such as levees, dikes, berms, etc.) uplift buoyancy force must be counteracted with overburden or restraint devices, such as geogrids, geomembranes, hold down devices, etc.
Geofoam has been used in geotechnical applications worldwide for more than 30 years. “Geofoam’s popularity has begun to grow exponentially in the past decade,” said Frank Kiesecker of ACH Foam Technologies, a leading manufacturer of geofoam. “This is due to its strong and lightweight physical properties and in part to the ‘greening’ of the construction industry. Geofoam has properties that fit the green model: It can be recycled, it is impervious to weather, it is produced without CFCs HFCs, HCFCs or formaldehyde - and with very little waste. Any clean post-industrial scrap or recovered product can be ground and turned into new EPS products or thermally processed into a resin to make other products such as garden furniture, coat hangers and disposable cameras.”
Geofoam Characteristics:
• Lightweight - 1% of traditional earth materials
• Strong- compressive resistance @ 1% deformation ranges from 2.2 psi to 18.6 psi.
• Engineered - reduces labor and project costs
• Arrives at the job site prefabricated and ready to place
• Impervious to the elements – not subject to installation delays due to weather
• Retains its physical properties under engineered conditions of use
About ACH Foam Technologies
For over four decades ACH Foam Technologies has been an industry leader in EPS manufacturing, providing products for construction, geotechnical, packaging, and industrial applications. With locations throughout the U.S., ACH is positioned to offer convenient, valuable, and complete solutions for its customers. ACH recycles 100% of its post-industrial EPS and is actively involved in recycling post-consumer EPS as well.
