Settlement characteristics in Tuff Rock

[Quence]

"Tuff (from the Italian tufo), also known as volcanic tuff, is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is compacted into a solid rock in a process called consolidation. "

You can't dig into Tuff rock with showel but need to use demolition hammer.

What is your experience about Tuff Rock.. especially weathered tuff rock? Can it cause foundation settlement too? To what degree?

 

[Mad Mike]

Quence,

You're broadly categorising what is already a blanket term for a rock type...just as with clay-derived rocks, the properties of tuff relate to its geochemistry.

We get some tuffas in central Africa that weather rapidly into a horribly active clay soil, whereas in our southern regions, we get siliceous tuffas that are completely inert, relatively hard and welded.

If you require a demolition hammer to remove the stuff, I can't see why settlement would be a concern. If you want to know the properties of your tuff specifically, you will have to go and test it. If durability of the rock is a consideration in your design, test for this carefully, including microscopic examination of the rock thin sections.

All the best,
Mike

 

[hokie66]

Where is the tuff located? Brisbane tuff is very hard, with negligible settlement under high rise buildings. Makes for excellent tunnel boring.

 

[Quence]

What do you make of lithic lapilli tuff? Its also called adobe. Why is it called adobe? Can it settle?

 

[fattdad]

UCS, structural orientations, presence of water, nature of discontinuities. . . BAM, you get the RMR (rock mass rating) or the GSI (geologic strength index).

So, you need core, RQD and other such etcetera and you'll be in a better position to describe the rock-mass properties.

Some of these rocks can degrade. So, durability can be a factor as the rock mass of today may not have the same strength as the rock mass of tomorrow.

Good luck, but we just don't have enough information.

f-d

ípapß gordo ainÆt no madre flaca!