Posted in Academic Issues, Civil Engineering

Yes, Civil Engineers, Things Move —

A salutary reminder from Y. Ryabov’s An Elementary Survey of Celestial Mechanics: There is of course no sense in asking why the planets rotate or why they have motion in general. Everything in the universe, from the smallest dust particle to colossal cosmic bodies, is in constant motion. There is no such thing as matter […]

Yes, Civil Engineers, Things Move —
Posted in Academic Issues, Geotechnical Engineering

Ohio DOT’s Rendition of the AASHTO Classification System

With the Unified soil classification system, there are many ways of diagramming it. One of those was presented in the last post. With the AASHTO system, there’s generally only one, as shown in the Soils and Foundations Reference Manual. For classification this is pretty much it, but it’s not very informative when it comes to getting a “feel” for what these classifications mean.

Below is a chart from the Ohio Department of Transportation (about the only DOT I know of which uses the AASHTO system for just about everything they do) which describes each AASHTO classification in words and attempts to describe the type of soil for each type in the system.

AASHTO Soil Classification System as Described by the Ohio Department of Transportation
Posted in Academic Issues, Geotechnical Engineering, Soil Mechanics

Unified Soil Classification, from NAVFAC DM 7

In the course of teaching my Soil Mechanics class, I’ve tried numerous different charts and methods for teaching the Unified system of soil classification. Probably the most success I’ve had is with the one from NAVFAC DM 7, and it’s below. (I’ve included the plasticity chart for completeness.)

An example of how this works is here.

NAVFAC DM 7 remains a popular reference book for geotechnical engineers, and ordering information is here.

Posted in Academic Issues, Geotechnical Engineering

Weight and Volume Relationships for Soils, from NAVFAC DM 7

Over the years, student and practitioner alike have to deal with weight and volume relationships in soils and the dimensionless constants (water content, void ratio, porosity, degree of saturation and so forth.) There are many different “cheat sheets” dealing with this, but the best one IMHO is the one from NAVFAC DM 7, presented below.

All of the variables you need are defined in the chart. It’s set up for unit volumes, but can be used with densities (but I’d read this first.)

DM 7 remains the single most used reference (directly or indirectly) in the geotechnical world. Click here to see how you can order your copy.