Lateral loads on bridges can result from earth pressure, seismic forces, wind loads, traffic or even ship impact or wave action. In cases where lateral loads govern, it is not uncommon to see designers add additional piles or drilled shafts or increasing the size of pile or shaft caps. This document by the Transportation Research Board provides recommendations for ground improvement methods for improving lateral resistance of weak soils, including a simplified approach for assessing the lateral resistance of improved soils using commercially available software packages. [Source: TRB. Image: TRB]
Many geoengineers and geologists have used the Structural Geology of Rocks and Regions textbook in structural geology class, and beyond. One of the authors, Dr. George Davis of the University of Arizona (emeritus) was recently on hand at the GSA's annual meeting to unveil a new edition of the book being published by Wiley. According to the AZ State Geologist's blog, the new edition will be available in mid-November.
On a personal note, I was fortunate enough to have Dr. Davis as my professor for structural geology at the U of A when I was an undergrad in geological engineering. I believe it was his last semester teaching the undergraduate course before he accepted a position as provost of the University. I still remember his engaging lectures and field trips. He was one of the very best instructors I had in my time at the U of A, for both my bachelors and masters. [Source: Arizona Geology. Image: Arizona Geology blog]
Every 6 months, the Business Practice Committee of ASFE conducts an "Industry Snap Shot" survey to gauge the state of our industry. They just had their fall meetings in Phoenix where the results from September's survey were presented. 60% of respondents were pessimistic about the next 6 months compared to 40% in the previous survey. Click through to ASFE for the full PowerPoint slideshow (It's only a few slides). [Source: ASFE: The Geoprofessional Business Association]
TRB's National Cooperative Highway Research Program (NCHRP) Report 697: Design Guidelines for Increasing the Lateral Resistance of Highway-Bridge Pile Foundations by Improving Weak Soils examines guidance for strengthening of soils to resist lateral forces on bridge pile foundations.
The report presents computational methods for assessing soil-strengthening options using finite-element analysis of single piles and pile groups and a simplified approach employing commercially available software. [Source: TRB. Image: TRB]
Phew, that's a mouthfull. The FHWA has recently posted a YouTube version of their 19-minute video (below) showing how to build geosynthetic-reinforced soil integrated bridge systems (GRS-IBS). The video is based on the content in the Interim GRS implementation guide released at the beginning of the year.
The September AEG News magazine mentioned this GPS based motion tracker by Applied Geomechanics for monitoring of bridges, dams, natural hazards and other features to a high degree of accuracy. The 3D Tracker systems include a base station and one or more receivers that connect via wireless internet to the 3D Tracker Software at a remote PC or optionally to a secure server (run by the vendor?). There are multiple graphical interface options for visualizing the data, and alarms can be set for various movement conditions. [Source: Applied Geomechanics via AEG News. Image: AEG News]
As engineers and geologists, we frequently use Excel charts to communicate data...but which chart types are the best at communicating data, and which ones should be avoided? This is one Excel charting expert's views on the issue. [Source: Peltier Tech Blog. Image: Peltier Tech]
Corey Berrien of JES Foundation Repair contacted me regarding some upcoming seminars in the Virginia area on Helical Foundation Systems, Helical Soil Nails and Push Piers. If you are interested, click through for more info.
Drill and Blast and Tunnel Boring Machine are two common types of tunnel construction methods. But roadheaders have been around for many years, getting their start in the coal mining industry. So where do they fit into the equation? According to Hans Greve, a Vice President with Aker Wirth, a manufacturer of roadheaders:
There are three basic ways to build a tunnel: convential drill-and-blast, fully mechanized with a TBM, or the in-between method with a roadheader," Greve said. "The roadheader is used for short tunnels - about 2 to 3 km [or about 1.5 miles] - that have self-supporting rock. But if the rock is too hard, the progress rate drops and the cost of wear and tear increases, so there is a certain point where roadheaders are no longer cost-effective.
These guidelines provide professionals evaluating site-specific conditions in areas known or suspected to be subsiding with a standardized minimum level of investigation for land-subsidence and earth-fissure hazards. The guidelines do not include systematic descriptions of all available investigative techniques or topics, nor is it suggested that all techniques or topics are appropriate for every project. Variations in site conditions, project scope, economics, and level of acceptable risk may require that some topics be addressed in greater detail than is outlined in these guidelines. However, all elements of these guidelines should be considered in comprehensive land-subsidence and earth-fissure hazard investigations, and may be applied to any project site, large or small. These guidelines are largely modified from draft recommendations prepared by Lund and others (2010). That draft, in turn, was developed using existing guidelines for preparing engineering geologic reports in Utah (Utah Section of the Association of Engineering Geologist, 1986), guidelines for evaluating surface-fault-rupture and land-subsidence hazards in Nevada (NESC, 1998), and guidelines for evaluating surface-fault rupture in California and Utah (California Geological Survey, 2002; Christenson and others, 2003), with additions and comments from various professionals involved in land-subsidence and earth-fissure investigations.
The Arizona Land Subsidence Interest Group contributed this report to the AZGS. I am a member of the group, albeit an inactive one. This document was commented on extensively by experts in consulting engineering geology, geotechnical engineering as well as agency representatives from the AZGS, APS, ADWR and others. Kudos to the group and those individuals who spearheaded the creation of this valuable resource. [Source: AZGS Document Repository. Image: AZGS]
Although exploratory borings and engineering studies during design are an integral part of foundation engineering, the axial resistance of a driven pile foundation is ultimately determined by the criteria used to decide when to stop driving the pile during construction. The use of test piles for the purpose of developing the pile installation criteria can be instrumental in building driven pile foundations that are reliable and cost-effective. Nationwide practices for developing pile driving criteria range from the use of very simple formula without any test pile verification to the use of pre-production test piles with dynamic measurements during installation and static load testing. Many agencies employ a range of technologies and methods based on the size of the project, the type of pile, and the predominant ground conditions. However, this issue is handled differently from state to state based on local experience, economics, and other factors.
This synthesis provides a survey of the current practices used by transportation agencies to develop pile driving criteria, with special attention placed on the use of test pile data. The survey consists of questionnaires sent to all 50 state departments of transportation plus the District of Columbia and Puerto Rico; 44 of the 52 agencies provided responses. In addition, a Phase II Survey was performed by telephone interview with nine agencies representing a broad geographical distribution of large states that have extensive pile foundation construction projects.
The information collected indicated that practices used by transportation agencies to develop pile driving criteria for production pile installation can be described as highly variable in terms of the level and sophistication of the testing performed. To some extent, such variability in test pile requirements may reflect the inherent variety in project size, complexity, ground conditions, pile type, etc. However, a significant component of the variation in pile driving criteria may be related to the pace of implementation of new approaches to pile testing and variation among agencies with respect to training, experience, and acceptance of new technology.