Residual Soil

[BigH]

Off for a two day workshop the 26th and 27th July with Dr Laurie Wesley on residual soils. . . should be interesting. Will post some info after I get back from our short Thailand vacation.

Cheers

 

[fattdad]

looking forward to anything you can share. That stuff's all over the Piedmont! Mica crazy! Well, unless you are in a Triassic basin. Then it's smectite crazy!

Curious about their thoughts on DMT and CPT.

Curious about their thoughts on relic structure, 'cause I've seen some crazy stuff in that regard too! Slope stability of residual granite for example! Who would have thought a 2:1 slope would have failed? All according to a vertical fracture in the parent granite, that gave the 10-ft deep tension crack!

Sure, that'd be an interesting workshop!

f-d

ípapß gordo ainÆt no madre flaca!

 

[Okiryu]

Hi BigH, hope the workshop was interesting... if you can share any information about engineering properties of compacted residual soils, it will be appreciated !

 

[BigH]

It was quite interesting. I will see what I can do about finding a url to post some of the sections.

A few points, though:

1. There really needs to be a distinction between sedimentary soil and residual soil. Residual soil has no preconsolidation pressure . . . and Dr. Wesley feels that e-log p curves are wrong - should be plotted as e-p curves (natural scale).
2. Residual soils cannot be lumped together in a similar fashion as sedimentary soils . . . ash soils, for instance, in Indonesia, are a totally different animal than residual granite soils and as fattdad points out the micaceous soils of the Piedmont have their own set of problems.
3. Relic jointing planes are, in fact, important. I've seen slopes of 20deg fail due to relic joints or previous slides.
4. Weathering of residual soils, too, are not equal. Most point to the 6 stages that have been published in many books; these were developed for Hong Kong granitic soils and do not represent soils such as limestone where any weathering into residual soil is very very thin.
5. Some residual soils have remoulded strengths almost similar to that of the peak strength - in other words, some do not show even the slightest of sensitivity.
6. For any correlations - these should definitely be based on local experience.
7. Dr. Wesley is a firm believer in the CPT - in fact, much of his experience was in Indonesia and at the time Indonesia was only one of three countries that really carried out CPT testing (Netherlands was the other - Indonesia was a colony of the Netherlands).
8. He suggests that consideration be given, in compaction control, to using vane shear testing or DCPT or CPT to control lifts rather than proctors and nuclear or sand cone testing. Strength of 150 kPa to 200 kPa and saturation levels of between 5 to 8%. Some residual soils have no "set" optimum and actually soften with additional "overcompaction" effort.
9. When doing laboratory testing, such as Atterbergs or Proctors, DO NOT DRY OUT THE SOIL FIRST, then rewet for the testing. This can drastically change some properties. There are some residual soils that if you heat to over 70degC, it starts to drive away the "bonded" water and not just the "free" water.

Again - I will try to find a way to post of these for you to all see. Else, send me your email addy and I will try to sent them to you. I have some of the emails from this group but not all. I can be found at bohicafries on google's email addy.

 

[fattdad]

any distinction between residuum in metamorphic rocks v. igneous/sedimentary rocks? I ask because metamorphic rocks can be somewhat unstable as their minerals are all related to a stress/temperature history that was very unique and not longer around.

Interesting bullet list BigH!

f-d

ípapß gordo ainÆt no madre flaca!

 

[BigH]

Do not specifically remember (at this time) any comments to that nature - other than all residual soils should be treated "independently" - as they will have different properties and behaviour. I will see what I can find out - might take a while.

 

[BigH]

fattdad - might take a look at this - just found it. Went over a little bit but it looks promising to provide information - perhaps not exactly what you are looking for but . . .

https://era.library.ualberta.ca/files/794080361/4051304.pdf

 

[BigH]

See link for file on compaction of residual soils that Dr Wesley presented that I alluded to in the OP. The file will be available for 14 days from 2017-Aug-08T1330(GMT+8)

https://file.town/download/hvtvd8peynmsfzica256qicgf

 

[Okiryu]

Hi BigH, sorry I could not download the file. Could you send it to jimmyok19atyahoo.com? Thanks !

 

[Okiryu]

BigH, thanks a lot ! I have received your files.