July 2004

New Personnel: Dr. David Russell will join Itasca Consulting Group, Inc. starting September 1, 2004. Dr. Russell has a degree in Theoretical and Applied Mechanics from Cornell University. In addition, he has 10 years of experience programming Itasca codes, having worked for Itasca as a principal software developer from 1989 to 1999. Dr. Russell's expertise in computational fluid dynamics and object-oriented programming will be a valuable asset in the development of Itasca codes. We look forward to having Dave working with us again.

Ongoing Work: Itasca engineers have recently applied FLAC and FLAC3D to the solution of ground freezing problems. Ground freezing is commonly used for groundwater control or excavation support in underground construction projects and is achieved by circulating refrigerated coolant through subsurface pipes. This results in a gradual conversion of soil water to ice, converting the soil to a strong impermeable material. Analyses to date have focused on modeling the freezing process itself to predict the rate and extent of pore ice development around freeze pipes, and the stability of excavations such as tunnels and shafts within frozen ground. In cases where there is no groundwater flow, the ground freezing process has been modeled successfully using the codes' thermal conduction logic along with FISH functions to account for conductive and convective heat transfer at the freeze pipes, the addition of latent heat during freezing, and the changes in thermal conductivity that accompany pore ice development. Problems involving groundwater flow have required more sophisticated coupling of the thermal conduction, thermal advection and fluid flow processes within FLAC and the development of additional FISH functions to account for the changes in permeability with freezing. The recent addition of thermal advection logic to FLAC has made it an exceptionally powerful tool for predicting the rate and extent of ground freezing - an important consideration when evaluating the viability of ground freezing as a method for soil stabilization and also for proper scheduling of ground freezing within project timelines.

Figure: temperature contours around two freeze pipes (in white). The extent of the contour indicates where the ground is completely frozen. Groundwater flow (green vectors) is redistributed around the impermeable frozen ground and transfers heat energy, slowing the overall rate of ground freezing and causing preferential freezing on the downstream side of the freeze pipes.

Feature Added:Built-in Hoek-Brown Constitutive Model
has been added to the FLAC 5.0 pre-release. This model implements the Hoek-Brown failure criterion and incorporates a plasticity flow rule that varies as a function of the confining stress level. The new feature, along with documentation, is available now from the FLAC 5.0 Pre-Release download page. The "Revision History" on the page indicates all the changes and additions that have been made to date on FLAC 5.0.

UpdateAlert:

Updated since 6/1/2004:

Dr.-Ing. habil. Heinz Konietzky of Itasca Consultants GmbH is a member of the Scientific Committee and co-chair of the "Numerical Modelling – Continuum versus Discontinuum Models" session at the upcoming ISRM Regional Symposium EUROCK 2004, which is to be held October 7-9 in conjunction with the 53rd Geomechanics Colloquy. The International Society of Rock Mechanics (ISRM) was founded 1962 in Salzburg, where the upcoming conference will be held. During the conference several topics related to design, construction, monitoring, and maintenance of geotechnical projects will be addressed. In addition to Dr. Konietzky, Itasca offices will be represented by individuals presenting papers and in attendance, including Daniel Billaux and Mark Christianson. Itasca will also participate as an exhibitor. Please stop by the booth if you plan to attend the conference.

Upcoming Conferences

Visit the conference web site for more information

See the Second Circular and Preliminary Program (.PDF, opens in new window)

Aside from scheduled, open training classes, an excellent opportunity for training in Itasca software is client-originated training, where the impetus for the training is at the user's request. Advantages to client-tailored training include: schedule flexibility, advantageous location (clients can choose whether to train at an Itasca office or to have an instructor visit their location), and the ability to collaborate in framing the training curricula to meet the client's needs. Such types of training occur on a regular basis. In the past month, two such training courses occurred: Alberto De Donati from IMIFABI in Italy recently spent three days at the Itasca office in Minneapolis receiving training in 3DEC; and JoinusSoft, Itasca's agent in Singapore, recently provided UDEC and FLAC3D training to six individuals seeking to develop a facility with those codes.

A newly proposed PFC model developed by Dr. Denis Zyryanov of the Institute of Water Problems of RAS (Moscow) has been especially designed for materials that possess complex underlying physics such as strain-rate sensitive strength, widely observed for example in ice samples. The adjacent figure demonstrates the penetration of two projectiles into a wall with normal strength depending upon the corresponding strain by exponential law. The upper projectile moves two times faster than the lower one. The higher the projectile velocity, the more brittle material behavior is observed (circle 1 in contrast to circle 2).
 

Q: “Is there an alternative to the hardware lock for securing my Itasca code?”

A: The code must be locked using a hardware device. However, Itasca has recently made available an option to use a USB-based hardware lock instead of the usual LPT1-port device. New code purchasers may exercise the option to choose from either type of device. Current code users who have LPT1-port keys may change to the USB-type key for a nominal charge.

The following articles by HCItasca professional staff have been published since April 2004.

Detournay, C., B. Wu and C. Tan. (2004) "Hydro-Mechanical Modeling of Damage Around Borehole in Laboratory Experiments," in Gulf Rocks 2004: Rock Mechanics Across Borders & Disciplines. Proceedings of the 6th NARMS Conference, Houston, June 2004, D. P. Yale, S. M. Willson, and A. S. Abou-Sayed, Eds. Paper no. ARMA/NARMS 04-590.

Konietzky, H., T. Gröger and L. te Kamp. "Simulation of Time-Dependent Damage and Microfracturing via Particle Methods," in Proceedings ICLODC 2004 (Bochum), Ruhr-University Bochum, SFB398, S. 131-140. F. Stangenberg et al., Eds. ISBN 3-00-013257-0, 2004.

Konietzky, H., K. Lorenz and W. Witter. "Simulation of Landslide Movements Based on a Multidisciplinary Approach," Felsbau, 22(2), 23-32 (2004).

Witter, W., and H. Konietzky. "Hangrutschungsrisiko an der Talsperre Schönbrunnn," Wasserbauliche Mitteilungen des Instituts für Wasserbau und THM der TU Dresden, 27, 1-19 (2004).

If you are interested in obtaining a copy of these articles, we invite you to contact HCItasca for assistance.

   ©2004 HCItasca, Inc.

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