A Three-Day Short Course by Mike Jefferies and Dr. Dawn Shuttle
Critical State Soil Mechanics for Practical Engineers
Marriott Pinnacle Vancouver, 1128 West Hastings Street
February 6 to 8, 2020
The VGS will be hosting a three-day short course from Thursday, February 6 to Saturday, February 8 on the practical application of critical state soil mechanics.
Registration
Registration is limited to 40 people in total.
Registration is limited to 5 people per company.
Regular registration is $1,100, student registration is $500.
Registration forms are available here. The company registration limit will be waived closer to the event.
There are no registration spots remaining as of January 6. Registration forms and cheques will be held in the order received in the event that there are any withdraws.
Course Overview
This course was developed for the VGS as a sequel to a Cross-Canada Lecture on the history of CSSM: “Great talk, Mike, but how on earth does it all work?”. The problem being that keynote lectures or the like can essentially only draw attention to important aspects, where true understanding needs a couple of days of full-time effort; in essence, a post-grad module of an MSc. Thus, this course, which has now been taught in Atlanta, Brisbane, Cape Town, Jo’burg, Phoenix, Santiago and, Stockholm as well as Vancouver to fill-in what so many universities have failed to teach.
Why the interest in CSSM? As much as anything it has been recent dam failures, with their transitions from drained to undrained conditions in tens of seconds (or quicker), that have challenged conventional geotechnical engineering which provides little in the way of explaining how such failures develop. But, this mechanism is very simple in terms of physical principles embodied in CSSM. And, while Fundao, Cadia and Bramadinho are now prominent there is nothing new – this type of soil behaviour has been known for a century as illustrated by the Calaveras, Fort Peck, and Aberfan flowslides.
Advanced soil mechanics applies the doctrine ‘if you cannot compute, you have nothing’. This phrase derives from a most fundamental question about knowledge (search the Church–Turing thesis on Wikipedia) and, for the practical engineer, amounts to requiring that our theories ‘add up’; and the easiest way to find that out is to use a spreadsheet – which is the approach followed in this course. Properties are derived from data, but then these properties are used to formally compute the soil’s entire behaviour in laboratory tests – so checking that what you believe to be your ‘understanding’ is actually consistent with the raw measurements you made. This emphasis on using spreadsheets also naturally lends itself to learning – the course interleaves lectures with tutorial sessions in which participants pull the CSSM framework together for themselves. The course comprises four modules, each based on data and templates that are provided, to step through this learning.
The first module is about soil behaviour seen in laboratory tests – there is little theory as such here other than the idea that soil comprises particles; this all goes back to the teaching of Casagrande, Taylor, and Bishop and their insight works just as well today as in the 1950’s. This brings a common understanding about the nature of the critical state and stress-dilatancy on which CSSM is developed.
The second module looks to representing fundamental ideas about soil behaviour in a computable manner; the theory of plasticity applied to soils leads to CSSM: three simple, but simultaneous, equations that capture the entire spectrum of soil stress-strain behaviour. A sequence of developments are used: undrained Original Cam Clay (OCC) to learn numerical integration in a spreadsheet; drained OCC which is then validated to some triaxial data; exploration of why OCC does not work most of the time; generalization of the framework into NorSand (NS) that works all of the time for all loading paths and all soils. This module aims to remove the ‘mystery’ from CSSM so that participants gain confidence in the power of the underlying mechanics and no longer see CSSM as some kind of ‘black box’.
The third module then moves from ‘learning’ via spreadsheets to ‘industrial use’ via Visual Basic, a high-level language provided as part of Office. Open-code software provides a comprehensive modelling environment to assess a suite of laboratory tests using CSSM; no programming skills are needed. The initial focus is on triaxial tests to determine and validate soil properties, with extension to direct simple shear to validate CSSM in plane strain. Data will be provided, but participants are welcome to bring their own set of laboratory tests.
The fourth module is about moving to field conditions. Modules 1-3 are based on laboratory tests where we know the soil’s void ratio and type – which you likely will not know insitu. Thus, practical engineering relies on the piezometric cone penetration test (CPTu) which as well as giving all sorts of stratigraphic information is the most accurate measurement of insitu soil state. The CPTu allows laboratory-based understanding to be used in practical situations. This module will lead participants through processing CPTu data to assess the state parameter and flowslide potential, including use of the CPTwidget to provide soil-specific calibrations for the CPTu.
Analytical methods (FLAC, Plaxis, ABAQUS etc) are not dealt with in this course. Rather, this course aims to give you the tools to obtain realistic inputs for such analyses.
Course Requirements
No particular geotechnical knowledge is needed as a pre-cursor, although the course assumes a familiarity with stress and strain, standard triaxial testing, and the CPT. There is no prior reading, with the course covering everything that is needed. However, potential participants may wish to download (it is free) and read the paper ‘silt state from CPT’ from
https://www.icevirtuallibrary.com/doi/full/10.1680/jgere.16.00008 as that gives a flavour as to where the course gets to (the course will actually use an enhanced version of the software presented in this paper).
IMPORTANT: participants must be familiar with Excel and making graphs within Excel; soil mechanics is taught, not Excel ! Participants will need their own laptops.
The course is aimed at early to mid-career geotechnical engineers, although more senior people are welcome.
Tutors
The course will be taught by Mike Jefferies and Dr. Dawn Shuttle. Mike is co-author of the widely-cited book ‘Soil liquefaction, a critical state approach’ and the course roughly follows Chapter 2, 3 and 4 of that book. Dawn developed the implementation of NS in software used to analyse the Fundao and Cadia failures, as well as the CPTwidget. Andrea Lougheed will be assisting with tutorials.