Yes, the piroclastic pumice/clastic is easy breakdowhn with the roller. But
the problem is the compactation. Proctor density these material
(traquitiques ignimbrites) is 1,5 gr/cm3 and the moisture is 40%.
The distribution of voids and tubes is random and I can't make infinity
drill. It's very expensive. I think that the electric geophysic can be
interesting for these volcanic rock/soils.
I usually see the investigation wells but the samples are very very
disturbed with low recuperation. I have serious problems for identification
this samples.
My theory, I think the drilling holes are valid for soils (clay, sands) and
hard rock. Soft rocks, gravel and blocks are very disturbed for the drilling
holes and the geotechnical parameters are not obtains.
Regards
----- Original Message -----
From: "Jeff Farrar" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, April 24, 2001 4:17 PM
Subject: Re: Fw: Volcanic soils
The soft rock is a problem - I worked with a compaction issue for NOAA in
Hawaii. The materials were gravel to cobble size pumice/clastic material.
It would breakdown easy with the roller.
You could run shear tests on the material - but of course scale is a
problem. I would think though that you could scalp the sizes down and still
get some data on strengths.
The strength distribution in the natural ground flow/eject areas should be
highly variable - voids, tubes etc. You have to drill to look for those.
But light structures should not be a problem.
Sorry not much help - there are no insitu tests you can use - just drill it
and observe it??
Regards
Jeffrey A. Farrar M.S., P.E.
Bureau of Reclamation
Earth Sciences and Research Laboroatory
Denver Federal Center Bldg 67, rm 152
PO Box 25007 D-8340
Denver CO 80225
303-445-2333
fax445-6341
[log in to unmask]
>>> ICINCO LAS PALMAS <[log in to unmask]> 04/24/01 09:05AM >>>
It's true. Andosols are susceptible moisture content. But the rainfall can
rise the moisture content quickly here. So, the break of conductions is very
frecuently.
Other problems and the volcanic islands are geotechnical parameters in the
soft rocks, p.e. ignimbrites, piroclastic surge, ash and pumice and other
types of rock-soils. These materials is impossible know the geotechnical
parametes because I can't test in the soil laboratory. Anybody can help me?
Thank you.
José María Morales
----- Original Message -----
From: "David Toll" <[log in to unmask]>
To: "'ICINCO LAS PALMAS'" <[log in to unmask]>;
[log in to unmask]
Sent: Tuesday, April 24, 2001 9:33 AM
Subject: RE: Volcanic soils
> It is worth re-emphasising the point made by Jason concerning the effects
of
> drying on measuring moisture content - and clearly this affects the index
> properties. Andosols, allophane-rich and halloysitic soils found in
volcanic
> regions are particularly susceptible. Soils that have liquid limits of
well
> over 100 when tested in their natural state appear to be non-plastic when
> they have been oven dried. Therefore it is meaningless to quote Atterberg
> limits without specifying the method of preparation. Mixing times during
> specimen preparation also affects the results (see for example, Newill, D.
> (1961) Geotechnique, 11, pp 302-318). Similar problems are found with
other
> basic properties, such a determining clay fraction.
>
> David Toll
> ------------------------------------------------------------
> Dr David Toll
> University of Durham
> School of Engineering
> South Road
> Durham, DH1 3LE, UK.
> Tel: (+44/0) 191 374 2566 Fax: (+44/0) 191 374 2550
> e-mail: [log in to unmask]
> www: http://www.dur.ac.uk/~des0dt/
> -----Original Message-----
> From: Geotechnical Engineering Email List
> [mailto:[log in to unmask]]On Behalf Of ICINCO LAS PALMAS
> Sent: 23 April 2001 18:45 PM
> To: [log in to unmask]
> Subject: Volcanic soils
>
>
> Hi! I work in the Canary Islands. These islands are volcanics and I don't
> find information about the parameters of th geotechnical soils and rocks
> (basalts, piroclastics, expansive clays and other soft rocks). It's very
> difficult the clasification of this materials!!!
>
> Thank you
>
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