Structural Engineering: RE: Soils Reports

Neil, I recall years ago a similar situation with expansive rock in an area around Stanford, but I think it was in Sharon Heights. The buildings were constructed on pier and grade beam without knowing about the expansive rock that the piers were drilled into. Later I worked on a new house on the stanford campus. It had expansive rock, and isolating the grade beams would not solve the problem because the pier itself was subject to raising even if the grade beams had a void space.

Jeff

From: Neil Moore [mailto:nma@omsoft.com]
Sent: Tuesday, July 22, 2008 8:22 AM
To: seaint@seaint.org
Subject: RE: Soils Reports

Yes, that's the kind of stuff we see here in "Cali" also. Had one case in Woodside where there was two different types of rock running diagonally under the house with a clayey overburden. The house was on piers but there was expansive soil above the rock and no one provided some sort of space under the grade beams or considered the drag on the sides of the piers. Also the top of the piers had extra concrete at the top which also contributed. Had a good investigative geotech as I had wasn't aware that some rock expands.

House was trashed by the movement but the people were still living in it - beautiful house - exclusive setting - maybe worth 7 mil. No mold at that time.

Neil

At 07:12 AM 7/22/2008, you wrote:

I don't know about Cali, but in my neck of the woods, we have vastly varying soils within a subdivision. Just going across the street we see a completely different soil. One house I had to do a condition assessment on was built ½ on an expansive clay and the other ½ on a collapsing sand. You should have seen the look on the Geotech when they were running a water level. Turns out a deep foundation should have been required, and we ended up doing a helical pier underpinning effort. In N.W. Wyo, I recommend it to everyone building to get a geotech report. For us, it's more than just soil bearing pressure, but also soil reaction. Don't know what the soils are like in Cali.

Sincerely,
David Maynard
Gillette, WY

From: Steve Gordin [ mailto:sgordin@sgeconsulting.com]
Sent: Monday, July 21, 2008 6:27 PM
To: seaint@seaint.org
Subject: Re: Soils Reports

Tim,

It was discussed earlier in the year. In my experience, in 80% of the projects, 1,000 PSF suffices (as it should), if not - find a geotech familiar with the area to write a memo reflecting the requirements of the 2007 code (another 15%), if not - then a full blown soil report will be required.

V. Steve Gordin, SE
Irvine CA

----- Original Message -----

From: Pinyon Engineering

To: seaint@seaint.org

Sent: Monday, July 21, 2008 14:37

Subject: Soils Reports

Hi,

In the new 2007 California Building Code -- section 1802 requiring a soils report for all new projects - even single family homes! what is the reason for this . Do the geotechnical engineers need more work - Were there any spectacular failures I missed that caused this provision?

any comments or insight

Tim Rudolph

Bishop CA