After saturated conditions weaken a 3 foot thick concrete base under a long span of rail track, URETEK crews work in tight conditions with over 12,000 volts buzzing overhead to stabilize the compromised track using structural grade polymer. www.uretekicr.com
Nicholson Construction built a cutter soil mixed (CSM) retaining wall for an unusual application at the Hill Air Force Base in Ogden, Utah. A 50-ft diameter by 50-ft deep shaft was constructed using CSM as temporary shoring to construct a turntable and pylons to allow an F-22 Raptor and other stealth aircraft to be raised to a height of 20 feet to allow radar testing of low observable coatings (stealth paint). The CSM shoring was also used for a portion of access tunnel for the shaft and pylons. The CSM panels were overlapped to create a water-tight seal and prevent seepage and eliminate the need for dewatering, a tricky and expensive proposition with the contaminated ground present at the site. Read more about the project at the link below. [Source: Nicholson Construction. Image: Nicholson Construction]
US Wick Drain of Leland North Carolina recently completed the world's largest marine barge wick drain installation...over 12 MILLION linear feet. The wick drains will allow timely consolidation of marine sediments supporting dikes for the new Craney Island Port in Norfolk, Virginia. The equipment was installed with APE wick drain installation machines through steel pipe-lined holes in the barge. Engineers predict 21 feet of settlement once the wick drains are preloaded. [Source: APE News via National Driller. Image: APE News (Backus Aerial Photography)]
I kept the same title of the source article for my post...it is a very simple explanation of the enhanced geothermal systems or EGS process of extracting geothermal energy from hot, dry rocks...even if it is a little sensationalized. The AP article describes the well-funded Newberry Crater Geothermal project in Central Oregon. The project is being run by AltaRock Energy, Inc. of Seattle and Davenport Newberry Holdings LLC of Stamford, Conn. with $43 million in funding from the US Federal Government, Google and other investors.
The site is an inactive volcano that has not erupted since before the last ice age. There is plenty of heat available, but unlike conventional geothermal projects, there is no water in the formation and/or the rock is too impermeable for the fluid to flow. Enter the EGS technology, which involves something they are calling hydroshearing, where water is injected into the hot boreholes along with some kind of polymer particles (not sure of the size). The cold water contacting the hot rock causes fractures to form, and the polymer particles keep the cracks open allowing water to flow deeper into the formation and form additional cracks. Eventually the polymer melts away. This process is similar to the hydrofracking I've posted about recently, but the oil and gas industry uses sand to wedge the fractures open and there was no mention of chemicals in the EGS process.
One major concern with EGS and most geotehrmal projects is the possibility of induced seismicity, or man-made earthquakes, something that has been in the news a great deal recently. The testing will involve injecting water at a rate of 800 gallons per minute into a borehole 10,600 feet deep. The projected fractured area is from 6,000 to 11,000 feet below the ground surface in a radius of approximately 1,700 feet around the borehole. The extent of the fracturing and presumably the magnitude of any seismic activity will be monitored using a network of seismic sensors. [Source: Yahoo! Green (AP) via ASCE SmartBrief. Image: Newberry Geothermal]
Crux Subsurface, Inc. of Spokane, WA was recently awarded a contract by San Diego Gas and Electric to provide design and installation of micropile foundations at 16 tower locations along a 7 mile stretch of power line for a wood to steel replacement project. Crux is best known for their difficult access and extreme access geotechnical construction and geotechnical investigation work, including helicopter access in rugged terrain which seems to be the case on this project. The work is scheduled to begin this month. [Source: National Driller. Image: National Driller]
A steel sheet pile cofferdam has been built around the HMS Alliance, a British submarine launched in 1945. The cofferdam will be infilled to create a safe place to perform restoration work. [Source: New Civil Engineer. Image: NCE]
The Fitzsimmons Creek run-of-river hydroelectric project consisted of a number of geotechnical challenges for design team member Golder Associates. The project site is in British Columbia's Coastal Mountains, and ran adjacent to the bobsleigh (or bobsled) track built for the 2010 Vancouver Winter Olympics. Some of the interesting geotechnical aspects included geohazard analysis for debris flows and historic slides, new retaining walls, lightweight concrete fill, anchor block design, rock slope stability at the power house, micropile stabilization of slopes, draped mesh rock suport, seepage analysis at the intake and spillway and more. A very fascinating project! [Editor] Disclaimer: Golder is GeoPrac.net owner Randy Post's employer. [/Editor] [Source: Golder.com Geotechnically Speaking. Image: Golder]
An arena being built for the Philadelphia Flyers' minor league affiliate hockey team will be founded on micropiles to mitigate possible sinkhole problems in the limestone bedrock. The arena in located at the site of a catastrophic collapse of a building, Corporate Plaza, in 1994. The collapse was blamed on sinkholes under the foundation that caused settlement and the rupture of a water main, flooding the area and exacerbating the issue. The building eventually had to be demolished. [Source: Morning Call via AGC SmartBrief. Image: CHUCK ZOVKO, The Morning Call]
Imagine a tower taller than the empire state building, surrounded by a greenhouse structure a mile in diameter all designed to generate renewable energy to power 100,000 homes using thermal updrafts to turn turbines. Sound like science fiction? The folks at EnviroMission Limited don't think so and they plan to build just such a structure in the Arizona desert. And geotechnical engineering firm Terracon has just signed on with EnviroMission to 'provide initial geotechnical engineering analysis, geo-seismic analysis and geotechnical consulting services for the Solar Tower power station development in Arizona.' Click through for the press release. [Source: PRWeb]
The US Army Corps' Wolf Creek Dam foundation remediation project in is the largest and most complex foundation remediation project in the world according the the contractor PM. It involves the installation of a massive cutoff wall to stop seepage in the karst bedrock beneath the Dam's embankment and right abutment. The project team recently reached a significant safety milestone, 500,000 work hours without a lost time accident. The project is approximately 62 percent complete. The contractor is Treviicos-Soletanche, a joint venture of Treviicos and Soletanche, the parent company of GeoPrac.net sponsor Nicholson Construction. [Source: National Driller. Image: USACEPublicAffairs Flickr]
Dr. Dave has a nice post about rapid drawdown slope failures and he ties it in to a neat video (below) of the removal of the Condit Dam in Washington state. The video shows some time lapse photography of the water receding, and pulses of slope failures occurring after the dam was disabled using explosives. The full dam removal will follow. [Source: The Landslide Blog]