AASHTO's Standard Specifications for Transportation Materials and Methods of Sampling and Testing, 33rd Edition and AASHTO Provisional Standards, 2013 Edition are now available for pre-order, delivery will start later this month. The 33rd Edition of the Materials Book contains 400 materials specifications and test methods commonly used in the construction of highway facilities, including 60 revised and 7 new specifications and test methods. The specifications have been developed and maintained by transportation departments through participation in AASHTO's Subcommittee on Materials. [Source: AASHTO Bookstore. Image: AASHTO]
Michael McVay and Khiem Tran of the University of Florida have produced a report for the Florida DOT on the detection of sinkholes using full-field seismic waves. Here is the abstract:
This research presents an application of two-dimensional (2-D) time-domain waveform tomography for detection of embedded sinkholes and anomalies. The measured seismic surface wave fields were inverted using a full waveform inversion (FWI) technique, based on a finite-difference solution of 2-D elastic wave equations and Gaussâ€“Newton inversion method. The key advantage of this approach was the ability to generate all possible wave propagation modes of seismic wave fields (body waves and Rayleigh waves) that were then compared with measured surface data to infer complex subsurface properties. Both the pressure wave (P-wave) and shear wave (S-wave) velocities were inverted independently and simultaneously. The FWI was applied to two synthetic and four real experimental data sets. The synthetic inversion results showed that the inversion was capable of detecting layering (e.g., strong over weak), and anomalies; in addition, the initial input velocity profile for the inversion was straightforward (i.e., linearly increasing with depth). The developed FWI algorithm could run on raw collected data with a minimum manual effort (no picking of first-arrival travel times). The inversion results of real data sets showed that the waveform analysis was able to delineate: 1) an embedded concrete culvert; 2) extent of multiple existing sinkholes/chimneys; and 3) a complex profile with an embedded void (unknown at time of data collection) and highly variable bedrock both laterally and vertically. Independent invasive testing (standard penetration test, SPT, and cone penetration testing, CPT) was conducted to verify the seismic test results. Finally, for the cases presented, the 2-D full waveform inversion was found computationally practical, i.e., the results were achieved in 2-4 hours of computer time on a standard laptop computer.
An article in TBM magazine provides a nice overview of cellular concrete technology. I never knew this (although it makes sense) but the material was used primarily as a lightweight floor leveling product for high-rise construction when it first came to the US in the 1950s. The article finishes with an overview of why cellular concrete is well-suited for grouting applications associated with tunneling and pipeline work. [Source: Read the full article at Tunnel Business Magazine via Cell-Crete Newsletter. Image: Tunnel Boring Magazine]
The Washington State Department of Transportation has released a report that provides a reference for geotechnical engineers and hydrogeologists on designing horizontal drainage systems to improve slope stability. Here's the report abstract:
The presence of water is one of the most critical factors contributing to the instability of hillslopes. A common solution to stabilize hillslopes is installation of horizontal drains to decrease the elevation of the water table surface. Lowering the water table dries a large portion of the hillslope which increases the shear strength of the oil, thereby decreasing the probability of slope failure. The purpose of this manual is to provide a single comprehensive reference for geotechnical engineers and hydrogeologists on designing horizontal drainage systems to improve slope stability. Guidelines are provided for translational and rotational failure and consider fractured systems. Basics of hydrogeologic and geotechnical terminology, site characterization and conceptualization, groundwater modeling techniques and template projects help to guide the user with respect to identifying important parameters to drainage design. An iterative approach is presented for determining the minimum drain construction to lower water levels enough to keep the factor of safety (FOS) greater than 1.2.
TRB's second Strategic Highway Research Program (SHRP 2) Renewal Project R23 has released a prepublication, non-edited version of a report titled Using the Existing Pavement In-Place and Achieving Long Life that describes a procedure for identifying when existing pavements can be used in place as part of the rehabilitation solution and the methods necessary to incorporate the original material into the new pavement structure while achieving long life.
In addition to the report, Renewal Project R23 also developed an interactive computer software program that helps users through the decision process. The software also provides all of the resource documentation related to the project. [Source: TRB. Image: TRB/SHRP2]
The USGS issued a press release at the beginning of May highlighting the possibility of accessing USGS topo maps and other USGS imagery on mobile devices such as Android, iPhone and iPad. The USGS is not producing apps, but they are making the data available to developers. They highlight two Android apps using the data:
The most likely candidate for an app for iOS is called Galileo. It sounds like you need to do some legwork before using the apps. They discuss a Java-Based open source project that allows you to create "mobile atlases" on your desktop PC or Mac based on USGS maps at various scales that you can transfer to various mobile apps to take the maps with you on your device for use when you are outside cell phone coverage. The program you need is called Mobile Atlas Creator. There are some basic instructions in the full USGS Press Release. [Source: USGS Press Release via Geology.com. Image: USGS]
TRBâ€™s National Cooperative Highway Research Program (NCHRP) Innovations Deserving Exploratory Analysis (IDEA) Final Report for NCHRP-IDEA Project 145: Extraction of Layer Properties from Intelligent Compaction Data examines a methodology that was developed to extract layer elastic modulus/stiffness from composite soil stiffness and global positioning system-based location provided by currently available vibratory intelligent compaction rollers.
Dimitrios at Deep Excavation LLC wrote this article a couple of months ago for his monthly newsletter. He contends that for multi-level braced excavations, the AASHTO LRFD code could produce unconservative results. From his article:
The currently adopted design methods for AASHTO (2010) LRFD appear to produce inconsistent and possibly unsafe designs for many multi-level braced excavations. Limit-equilibrium analyses combined with LRFD methods appear to severely underestimate benchmarked wall bending moments. For this reason, analyses in this paper suggest that limit-equilibrium methods should not be used to design the wall bending resistance for multi-level-braced excavations.
A new publication was released from the TRB's NCHRP program on Geofoam Applications in Slope Stability Projects.
TRB's National Cooperative Highway Research Program (NCHRP) Research Results Digest 380: Guidelines for Geofoam Applications in Slope Stability Projects explores the use of expanded polystyrene-block geofoam for slope stabilization projects. For the purpose of the report, slope stabilization projects include new roadways as well as repair of existing roadways that have been damaged by slope instability or slope movement.
I came across this interesting website recently. The Terrainator (is that a nod to Phineas and Ferb?) uses digital elevation model data to create a 3-D model that it can export to a site called Shapeways where it will be created using 3-D printing technology. The standard models are less than 3-inches square and a fraction of an inch tall. The cost is computed based on the amount of material needed to generate the model. This tiny model will run you somewhere in the neighborhood of $30. They recently added the capability to create larger models, but the price goes up to nearly $200 for a model roughly 8 or 9 inches square which seems to be about the max. The screen capture at left is of the US 89 Bitter Springs Landslide area in Northern Arizona. Terrainator has 10m USGS DEM coverage of most of the western US, and coarser coverage of the UK and other areas of Europe. Could make a great gift for a geologist or engineer in your life. But you need to pick someplace with pretty good relief to make it look interesting. [Source: . Image: Shapways.com]