Newsroom - April 2017
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The Thelen/Geotechnology – Cincinnati Branch has just begun the third year of a three-year design-build project for the new MLK interchange in Cincinnati, Ohio. The Prime Contractor is Kokosing Construction and the lead designer is HDR Engineering. This $80+ million project includes the construction of two new bridges, widening and/or improvements to three additional bridges, removal of two bridges, construction of six ramps, extensive retaining walls and improvements to other roadways in the vicinity of the interchange.
Thelen/Geotechnology provided geotechnical drilling and laboratory testing services during the design of the project. Project challenges included significant changes in rock elevation with rock excavation required in some areas, wick drains necessary to expedite consolidation of weak soils in other areas, and urban fill that required overexcavation and replacement.
During the construction phase, Thelen/Geotechnology is providing ongoing construction review services including density testing for the embankments, wall and utility backfill, concrete testing, and testing for the cement stabilized subgrade.
The project will significantly improve the travel time and access to Cincinnati Uptown, Cincinnati Zoo, and University of Cincinnati areas. The project began in the fall of 2014 and is scheduled to be completed in the summer of 2017.
Please contact us for more information regarding our services for your next Design-Build project.
The future beneficial use of fly ash seems to be ‘up in the air.’ Recent USEPA air pollution control regulations are resulting in the production of fly ash with uncertain chemical properties, typically additional carbon and heavy metals content. These properties may restrict or possibly prohibit the use of some historically available fly ash sources for use in concrete or for soil stabilization/modification.
The spotlight on fly ash is due to operational and equipment modifications at coal-fired power plants to meet new air pollution control regulations. Changes include the introduction of powdered activated carbon (PAC) into the flue gas upstream of particle control devices to reduce the expulsion of heavy metals into the air. Fly ash with higher heavy metal and carbon content is expected.
Fly Ash and Concrete
The use of fly ash to produce a more durable and stronger concrete is a well-established practice. Historically, fly ash included a small percentage of unburned carbon. Carbon can adversely interact with the concrete surfactants used to induce air entrainment. Consequently, current practice limits the percentage of carbon in fly ash designated for use in concrete. The concrete industry recognized this adverse effect and is developing processes to use high carbon content fly ash in concrete.
Fly Ash and Soil Improvement
Fly ash is frequently used to reduce the swell potential of highly plastic soils, increase the workability of wet soils, and increase the strength of pavement subgrades. The increased heavy metal content in some fly ash sources is resulting in some States (such as Missouri) reviewing a maximum amount of fly ash that can be used in unencapsulated beneficial reuse without receiving prior authorization or demonstration that adverse effects to human health and the environment would not occur.
Geotechnology continues to monitor these technical and regulatory changes on behalf of our clients. During this transition, our engineers communicate with regulators, the fly ash brokers, and review the fly ash chemical analysis reports to provide sound recommendations based on the available information.
It is important to know that individual states may have more restrictive requirements or permitting but to learn more follow the link below.
Geotechnology, Inc., a leading provider of geotechnical and environmental engineering, geophysics, water resource management, materials testing and drilling services, has announced that Tim Wilson has been promoted to Field Safety Specialist working in the Geotechnology Corporate Group.
A registered geologist, Wilson has been a member of the Geotechnology team for more than 15 years. He most recently served as a Senior Geologist in the Geophysics Group in St. Louis where he led geophysical investigations for the past eight years.
As Field Safety Specialist, Wilson’s primary responsibilities include conducting field safety observations and providing safety resources to Geotechnology staff on project sites throughout the United States. He will be based in the St. Louis office.
“Tim’s diverse and hands-on experience in several of Geotechnology’s operational groups will be an asset to identifying and controlling the hazards that our field staff face on a daily basis,” said Geotechnology Corporate Risk Manager Joe Darmody. “I am looking forward to working with Tim to improve the safety of our field operations company-wide.”
Wilson is a graduate of Arkansas Tech University, where he received a Bachelor of Applied Science (B.A.Sc.) in Geology/Earth Science.
Our geophysics team explains the use of ground penetrating radar (GPR) for pavement projects for Fox 2 news.
Fox 2 Link: Creve Coeur using radar for pavement projects
The Tennessee Valley Authority (TVA) is currently constructing a new facility in Memphis, Tennessee. The facility includes combustion turbine-generators, a turbine hall building, two heat recovery steam generators, one steam turbine generator, tanks, pipe racks, cooling towers, warehouses, and an administrative building. The project site is approximately 1 ½ mile to the east of the Mississippi River and approximately ½-mile to the south of Lake McKellar. The soils in the general area of the site consist of dredged materials, uncemented and young river deposits. The site is within the zone of influence of the New Madrid Seismic Zone (NMSZ), which has produced large earthquakes in the past.
TVA had a preliminary geotechnical subsurface exploration (SE) conducted during the planning phase. Kiewit Power (KP) retained Geotechnology to provide a geotechnical review of the preliminary SE during the bidding process. Based on the review, it was concluded that a supplementary SE is needed to provide sufficient design information. TVA then selected KP to provide design and construction services. KP retained Geotechnology to perform the supplementary SE, which included additional conventional drilling and in situ testing (SPT), sampling, laboratory testing, Cone Penetration Testing (CPT), and a site-specific seismic study. KP also retained Berkel and Company Contractors, Inc. (Berkel) to install Displacement Auger Pressure Grouted (APG-D) piles to support heavy loads and Cast-in-place Ground-improvement Elements (CGEs) for ground improvement purposes.
KP engineers faced a major challenge during the design phase: lateral spreading during the design earthquake event required by the 2012 International Building Code (IBC). Based on the results of the preliminary SE, a lateral displacement (LD) of 60 inches was estimated. To mitigate the LD impact, additional ground improvement was required by installing the CGE’s at tighter spacing. Additional piles were also required to limit the expected lateral movement of superstructures. The expected additional cost was around $30M. KP requested that Geotechnology perform analyses to evaluate the potential for lateral spreading due the design seismic event stated in the IBC.
Geotechnology engineers used two methods to estimate lateral spreading. The analyses utilized both SPT and CPT results, actual topographical information between the site and Lake McKellar and the site-specific seismic study results. The engineers also considered the database used for developing the analysis methods, the nearest distance to the possible seismic source, the uncertainty in developing the analysis methods, and they reviewed historical data (a 1910 USGS report) related to LD observations in the NMSZ. Based on the extensive study performed by our engineers, an estimated average LD of 6 inches was recommended. Accordingly, KP design engineers concluded the additional ground improvement and piles are not necessary, thus reducing the estimated construction cost by approximately $30M. The project is currently under construction, and it has a target completion date of early 2017.