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Archive for January, 2007

Earthquake Info for India

Posted by Kshitija Nadgouda on January 27, 2007

I came across a site created by Mr. Kishor Jaiswal that gives a lot of good information on earthquakes in general and about India in particular.

You can take a quiz on earthquakes or view an animation that shows how stress build-up leads to an earthquake.

The Seismology Division of the India Meteorological Society deals with the monitoring of earthquakes in and around India.

indiaquake.jpg
(Courtsey: Columbia News)

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Copyright Kshitija Nadgouda.

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Slope stability software

Posted by Kshitija Nadgouda on January 4, 2007

There is plenty of software available these days to do pretty much everything one can think of. As a geotechnical engineer, the software programs I have used most often have to be the ones available for slope stability or for geogrid design of a (soil) slope, besides using AutoCAD and gINT. Discussing AutoCAD and gINT calls for separate posts!

For a very comprehensive list on the different geotechnical and geoenvironmental software programs avaiable, check out the GGSD website. They list thousands of software programs, ranging widely in cost and applications.

The site lists a whopping 53 different programs for slope stability of soil alone!
The programs that I have most extensively used from the list are:

  1. XSTABL
  2. GSLOPE
  3. SLIDE

XSTABL is a DOS-based program and hence has not many takers. However, it does give a reasonably good graphical output. Although DOS-based, it is fairly easy to input data and has a good help feature. It allows the user to see the progress of the data while entering so you can edit any errors one may have made. It gives you an option of circular or non-circular search for failure surface. It uses Bishop and Janbu methods to calculate the factor of safety. The biggest advantage of the program is that it is relatively cheap! It costs US $450 only!! That roughly converts to approximately Indian Rs. 20,000 excluding any shipping and handling fees that may be added. A demo version is available at their website.

I primarily used GSLOPE for design of geogrid-reinforced slope stability checks. It is Windows-based and very user friendly. The program uses Bishop’s Modified method and Janbu’s Simplified method for calculating the factor of safety. It allows either method to be applied to circular, composite, and non-circular surfaces (which is not very correct – non-circular surfaces should be analyzed using Janbu method – not Bishop’s modified method). Data input can be done by either entering the co-ordinates of slope geometry or also be entered using a mouse (i.e. drawing the slope surface or subsequent soil strata). One good feature is that the analysis is real-time, i.e. if you modify a non-circular slip surface, it will update the factor of safety immediately. The program costs about Indian Rs. 45,000 (US $995) and additional cost for shipping and handling, roughly Indian Rs. 2,000. It provides a demo version for trial.
GLSOPE

SLIDE is a more complex program and very comprehensive. It has a steep learning curve, but can do a detailed study of the problem at hand. It can even perform probabilistic and sensitivity analysis. One can perform back-analysis of a slope that has failed, to determine the soil properties. Groundwater seepage analysis can be easily performed. Although it has a steep learning curve, the documentation and tutorials provided with the software are extremely useful.
The program has 10 different methods by which you can analyze a given slope. All analysis is performed simultaneously and the results are viewed in a separate “Interpreter” window. It has a CAD-like interface and so it is easy to draw the slope and soil strata during modeling. SLIDE doesn’t allow a demo version download and costs a whopping US $1495 plus shipping and handling, approximately Indian Rs. 67,000!
SLIDE

Some free software like STABLE is also available. My next task is to look at these freewares and review them!

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