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George Marshall - FW: any luck yet
From: "DeGroot, Dan" <ddegroot@burnip.com>
To: George Marshall <gmarshall@coppelltx.gov>
Date: 5/13/2010 7:17 AM
Subject: FW: any luck yet
George: I had our structural guy do a preliminary look over the spread footing retaining wall. Below is what he
emailed back. We will need to discuss this after I have spoken with him on the phone. I will be out most of the
day today in two separate walk throughs and then out tomorrow. I will call Monday. We have the quantities
done, just revising some of the spec pay items to match and getting the numbering correct.
From: Ackerman, Jeffrey
Sent: Wednesday, May 12, 2010 5:57 PM
To: DeGroot, Dan
Subject: RE: any luck yet
Dan,
I ran the numbers today for the TxDOT standard drawing 8-foot high pressure wall with the data from the
geotech report. The numbers did not come out well. The factor of safety for sliding was not met, 0.82 where
you need to have at least 1.5. I can't find anywhere on the standards what friction factor they use or if they are
counting passive pressure against the footing or key. The geotech report said to use a friction factor of 0.30,
which is on the low end of what we normally use. It also said to ignore passive pressure until you get 3-feet
below the surface, which is lower than the bottom of the footing and key. I also just ran the numbers for the
earth pressure and 2-foot of surcharge pushing on the wall. I should also add pedestrian load from the railing,
which is 50 plf on each rail, which will obviously make it worse.
I will be in the office all day tomorrow if you want to discuss this further. Looks like you will need the wall to be
designed and detailed for the conditions you have at this particular site.
Jeff
From: Ackerman, Jeffrey
Sent: Tuesday, May 11, 2010 5:56 PM
To: DeGroot, Dan
Subject: RE: any luck yet
Dan,
Sorry for not getting back to you, I got sidetracked on Friday, our office power went out on Saturday and I was
out of the office yesterday and today. I took a quick look through the plans and the standard drawings. For one
thing, you should be able to use the high-pressure drawing since your allowable pressure is 2,000 psf. Based on
the cross sections, your tallest wall is about 8-feet from bottom of footing to top of wall in a few locations.
Tomorrow morning I want to run some quick numbers in our program to see if the toe can be reduced to what
you want for the 8-foot section.
Jeff
From: DeGroot, Dan
Sent: Tuesday, May 11, 2010 9:37 AM
To: Ackerman, Jeffrey
Subject: any luck yet
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Lowell D. DeGroot, P.E.
Senior Project Manager
GSWW, A Division of Burgess & Niple, Inc.
11117 Shady Trail
Dallas, Texas 75229
972.620.1255 Ext. 6016
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