jdonville,
I believe the discussion of anchors would dissappear with a "stair-step" configuration because I assume each of the steps would be less than a 1:6 slope. This type of configuration is what we would recommend next if the inclination of the bedrock is too steep for comfort with anchors.
jike,
Thanks for your comments. If we look only at geometrical affects of the incline (not how wind loads, etc affect the design), and assuming a coefficient of friction between rock and concrete of about 0.65, then the FS would be about 3 with a 1:6 incline (and no pins). This isn't too bad if...
I've seen several references to keying and/or doweling spread footings into bedrock when the incline of the bedrock exceeds 1V:6H. However, I have not been able to find a reference for the steepest recommended incline before consideration should be given to blasting, etc, to level it. Does...
Everyone,
Thanks for the heads up from the Structural Engineering perspective. I come from a soils background and am not very strong when it comes to the redistribution of forces within a structure. I'll take the guidance any day!
Focht3,
Great answer! No matter how "fancy" you get with the analysis, it always comes back to the fundamentals, doesn't it? I'll see what I can find out about the proposed construction sequencing. Thank-you for your thoughts on this one.
Focht3 and gandersen,
Thank-you for the input. Focht3, this project is in Madison, Wisconsin, it's glacial deposits (on a sideslope of a ridge so generally it's lacustrine soil overlying deeper glacial till). The soil profile is lean clay and silt in the upper 1/2 then clean sand with gravel...
Is anyone aware of research that might indicate a non-traditional lateral stress distribution (i.e., something other than linearly increasing with depth based on Rankine pressure distribution) might be appropriate for deep basements? I am not aware of anything, but I have a client who was told...
To all - water table is in the lower sand soils, silts and clays are above the water table. Lower sand is also pretty clean (less than 5% P200) so build-up in upper layers is not too likely. However, keeping the water table depressed in the sand layer does require free draining material (and...
BigH,
Interesting thought about ka possibly being suitable because of the levels of restraint, I had not thought about that one. I've recommended the composite vertical drainage mat in reports, but I've never had anyone bite on that alternative (us Midwesterners are sometimes way too...
cdh61 - I'd typically recommend an at rest equivalent fluid pressure of between 80 and 90 psf for the typical native clay soil in our area, for our recommended sand fill I'd typically recommend between 45 and 55 psf. As you can see, that's a fairly major difference for the wall design. Because...
Point well taken. I guess I grow tired of seeing "cookie cutter" reports from my colleagues where the word "impractical" could be replaced with the word "obsurd" because the writer has not thoroughly thought through the recommendations being made.
kmerl and Focht3,
Thanks for the comments. You comments are in line with my thoughts (which is reassuring!). kmerl, I come from clay/silt country so we always recommend replacing the native soils with free draining sand soils to reduce the pressure on the wall. Manufactured material is...
Is anyone aware of recommendations for a minimum backfill width for basements to allow a) proper drainage and b) to allow the use of the lateral earth pressure values of the backfill instead of native soil? I've not to date commented about this in my reports, but a client showed me a report...
dirtsqueezer,
Our firm has used it to locate old graves in a pauper cemetary for a roadway realignment project. Worked well, but we weren't about to calibrate the data with a backhoe! The few times we've used it, we've rented it from the manufacturer. It's been my belief that the best use is...
VOD,
Thanks for the information. Concerning berming, on some existing tower sites we've also noticed that they tend to place the majority of the soil across the front half of the anchor, the remainder wraps around the guy wire support (with very little of the berm being on the side of the...
