bimrocks.com is an accessible  source of information on bimrocks for geological and geotechnical practitioners. The only other site like this one is my original bimrocks site, hosted by Geoengineer.org

October 2020 UPDATE: After 10 years of stasis, the site will shortly be undergoing a much-needed refurbishment. There is content to add, stuff to discard, and new ideas to share with the increasing number of people interested in bimrocks (and bimsoils).

What are bimrocks?

  • block-in-matrix rocks
  • mixtures of rocks composed of geotechnically significant blocks within a bonded matrix of finer texture
  • melanges, fault rocks, weathered rocks, etc.
  • geologically, spatially, and mechanically heterogeneous
  • trouble$ome to geotechnical engineers, geologists, contractors and owners

The words “geotechnically significant” in the above definition of bimrocks mean that there are criteria for scale, strength contrast, proportion and size of blocks. In bimrocks, blocks must have mechanical contrast with the matrix and, at the scales of engineering interest (from laboratory to site) there must be enough blocks of a size range to contribute to the overall strength of the rock mass.

Isn’t bimrocks just a silly word?  No!. “Bimrocks” is a word that I coined in 1992. “Bimrocks” is not a geological word, but simply describes the vast range of geological fabrics of strong blocks mixed with weaker matrix. Since there are no geological shadings to the word, engineers can focus on the characterization challenges rather than fuss about the geological origins of bimrocks.

Aren’t bimrocks rare? No, they are very common and thus there is no excuse for geopractitioners (like me) to avoid characterizing them. Bimrocks  include many complex geological mixtures of relatively strong blocks surrounded by weaker matrix: fault rocks, weathered rocks, lahars and melanges. Chaotic melanges  are the most difficult bimrocks to characterize. You can learn more here about melanges, and the role that one Northern California melange had in my life and research.

There are also bimsoils: Bimsoils are analogous to bimrocks but are composed of blocks embedded in soil (unbonded materials) with weak to no strength between blocks and matrix. such as weathered rocks, saprolites, lahars, debris flows, and colluvium.

So what? Who cares? Bimrocks and bimsoils universally frustrate the economic and accurate characterization, design and construction  of civil  engineering works.  Bimrocks are troublesome to geopractitioners, including geotechnical engineers and geologists. Owners and contractors care a lot, too – they lose money because of the troubles, although their lawyers help resolve the troubles.

How can this site help? My bimrock websites are likely the only sites where you can easily find useful and free information on working with melanges and other bimrocks: papers, presentations, short course literature, etc.

Need information:?   You are not alone in trying to work with geological complexity!

For some overall guidance see the Introduction and Summary Lectures for the Short Course taught in 2017 at Medellín, Colombia (Lecture PDFs can be downloaded); or, the annotated  but clunky-looking  “Introduction to Bimrocks”,

Also useful may be the 2011 paper: Geopractitioner Approaches to Working With Anti-Social Melanges, a chapter in the book Special Paper 480: Mélanges: Processes of Formation and Societal Significance, by John Wakabayashi and Yildirim Dilek, published by the Geological Society of America.

2018 Field Trip Guide provides a  snap shot view of San Francisco area bimrocks – with some touristic chatter.

This site offers many papers, presentations, dissertations, posters, Short Courses and photographs by myself and others who have kindly extended their permission for me to host their work. Please contact me if you want to contribute content to this site but note that I only post useful and well-presented material.

Use the resources freely, but please credit  authors! All resources are provided on the condition that they be used for sole use, and for the non-commercial purpose of scientific and engineering research.

Visit my bimrocks blog for infrequent thoughts, ideas, information  and comments by myself and the occasional visitor.


Questions, comments, contributions?  Contact:  edmedley@bimrocks.com