View Full Version : Retaining Wall Base
I just found out that a job that I turned down last year as un-buildable, has been redesigned. The supplier had their engineers write a job spec without ever going to the site and without soil borings or load tests. They assumed 2500 psf soil bearing capacity, site really had 200 psf bearing. Site was on a hill with 3'-4' of peat and water draining on it from three sides. Below this was a layer of clay about 2' deep then bankrun for the next 10'(I had a testing company go down 16') Now they want me to excavate down to stable soil and with fabric and 3" stone make a base 3' wide to support the wall. My question is what is the peat behind the wall wants to slide? I don't want the job to fail.<br><p>----------<br>paul<br>
02-20-2000, 01:28 AM
I'd definitely involve a geo-engineer and check into geo-grid type retainments behind the wall. I know there are some other types but I'm not familiar with them. Until an engineer signs off on the design for this one, I'd keep my options open.
It's a $130K job and I don't want to rebuild it at my expense! Good point.
02-22-2000, 08:55 AM
Hey Paul - <p>As you know I do more residential than commercial, and the residential is on a smaller scale than yours. In reading this forum, it reminded me of a residential project I bid on but didn't get (nobody got it, they thought it'd cost about half of what the bid was). I met with an engineer to discuss it briefly, just to get some advice. My question is this - When you had those soil tests done on that project, was that on your dime, or did you charge the potential customer? If you charged them, I'd be interested to find out how you work that into a contract. I'm unsure of how to approach something like that. <p>Thanks
Yes, I droppped the dime and got paid back for it. I use a soil testing service, because it's my company on the line and public works jobs have alot of exposure. If something fails it's my ass. I don't have to write that in my contracts because the specs that the villages give me have that spelled out, if the job was buildable I would have eaten the cost $200-300 isn't bad insurance on a $130K job.<p>----------<br>paul<br>
02-24-2000, 08:31 PM
Paul - you are wise to be cautious on a site like this. We don't do work of that scale, but here is what I saw two years ago. Behind a Lowe's (Home improvement store) the engineers pulled the same deal, and a huge wall went up with compaction tests and the whole deal. Simultaneously, I took in about 15000 yards of unusable (wet and silty) fill material from the same site. The stuff locks up like concrete when dry, but is very unstable when wet. This leftover material shifted and blew the wall right out, subsequently we received many triaxle loads of versa-lok block, fill, and the remains of the geo-grid material. I'm not sure who paid (it was very likely the engineer on the project who was liable though). I don't know the dimensions of your project, but in this case the building was done, so the CO was waiting on the wall replacement. On a 130k job I wouldn't want to move a few thousand yards of material after the fact. If an engineer signs off on it try to find out if they worked on a similar project, or if they are just theorizing. Also make sure there is some sort of drainage system. I have a suspicion that lack of proper drainage would make the peat suck in water, then swell and shift unpredictably.<p>PS - I would like to visit you if you are working on one of those lake or river projects. It sounds interesting.<br><p>----------<br>Phil Grande - Soundview Landscape Supply - http://members.aol.com/slsnursery<br>Ivy League Landscaping - http://members.aol.com/scagrider
Phil, We are working on the prints for the extention of the Fox River Job (snapped limestone) now, it looks like next year it will go. <br>I talked to the soils man this mourning we turned the job down.<p>----------<br>paul<br>
03-01-2000, 05:19 PM
We just had a request to build a two-tiered Keystone wall---on loose clay fill. Total height for the two walls would be approx. 15'l Demanded a design fee because we knew that we'd need an engineer and a good amount of time to get it designed and spec'd properly. Client declined which was fine.:)<br>If I hadn't read all of these posts we might not have been so cautious. I even told the client about the Lowes job. Guess they think that the bottom line is more important until the wall blows out. Thanks guys. <p>----------<br>Lanelle<br>
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