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Thanks Zelgar, 1. lifts are 400 to 450mm. When compacted with the impact roller, this would produce a relatively smooth clay surface, much like you'd get from a smooth-drum roller. 2. Not yet confirmed. See point 3. 3. No - they've tested to a 300mm depth on their 400 to 450mm layers. You're...

Hi All, I have a modest-sized earthworks site where the full depth of the proposed earthworks (cutting 10'; filling 10') is in a silty clay residual dolerite soil. The site is very gently sloping so the volumes are larger than the depths of the earthworks would suggest. The clay soils are of...

A quick note - just make sure you have interpreted the properties of your rock-fill correctly. What invariably happens, regardless of the packing and preparation of the rockfill layers, is that you get pockets of fines, at least to the extent that the fines can govern the strength of the...

I follow the same reasoning as McCoy - there are "rules of thumb" if I recall, that in a very well-jointed rock mass with poor joint quality, you would divide the rock UCS by 10 to obtain a safe allowable bearing pressure; in the instance of a tight rock mass you would divide the UCS by 3 for...

Thanks very much All - the positive feedback is a warm reminder of the good times we're living in! To date I have secured one chap in South Africa who would be capable of undertaking the review, and I will use the advice on this thread to try and secure a second and third. You guys are the...

Thanks very much for your assistance Geotech - I will contact Alexei early next week. I've e-mailed EireChch. Best, Mike

Hi All. I'm involved in a job which has gone horribly pear-shaped. It entailed the construction of a high earth-fill embankment which would support a major warehouse with very flat floors. The Engineer's design specification for the bulk fill was 95% Mod. AASHTO minimum. I gave predicted...

Your crushed limestone is not carrying all the load itself - it is distributing the load down onto your natural soil consisting of clayey sand. That is the reason you wouldn't design to the bearing capacity of the crushed limestone. For stability reasons, your plinth or footing is normally a...

I managed to find a photo of a cutting on the adjoining site, which has almost exactly the same subsoil profile as the current site...the upper mantle of dark red-brown soil that you see in this photo is the same residual dolerite clay-silt indicated on my sketch, which will form the foundation...

Thanks Guys for all the valued responses. See below a sketch profile - we'll be taking the top off a natural hill, and filling out on the side-slopes. As noted by GeoEnvGuy, in general, we are putting fairly free-draining fill on the side of a dry hill. The free-draining fill material is...

Mike, Thanks so much for your quick and informative response. My bulk fills will be built up over a deep residual clay-silt profile (no significant transported soils, just a thin colluvial mantle), but for the bulk fill itself I will be using free-draining, rocky material in the lower layers at...

Hi All, I have a site where the intention is to construct high fill embankments (50 - 70')on a hillside where there is no permanent water table. At a couple of locations on the hillside, broad, ephemeral drainage lines occur. My field testing has identified perched water tables through discrete...

My sincere thanks for this BigH - I shall put it to good use. I am often left overwhelmed by the complexity of it all; I'm a relatively simple Engineering Geologist, as opposed to a Geotechnical Engineer, and am pretty much in awe of the level you guys are at. I shall do my best to understand...

BigH - your response is a huge help, so my sincere thanks for it and for the references. Your description paints a good picture of how I should go about analyzing it. My geology is as good as it could possibly get...the bedrock is weathered granite and so the transported alluvial soils are...

EireChch, Thank you for the detailed and informative response. See my sketch below - I'm comfortable calculating settlements beneath a new fill embankment, but in my case we are doing a widening of variable width on the shoulder of an old fill embankment. In some cases the widening will be a...

Thanks GeoEnvGuy - I don't have access to finite modelling software, so will be jumping between Settle3D and hand calculations. In general, the drainage lines contain a few metres of loose to medium dense sand. We have very little clay, so long term remoulding is not something I'm worried...

Hi All, I've just commenced the geotechnical investigations for a highway widening which seeks to add an additional carriageway to our existing highway. There are some substantial fills (10 - 20m high) along the route, mostly coinciding with drainage structures (large culverts) beneath, and I...

So you're comparing apples with oranges now- the borehole SPTs have been performed at intervals through the profile; the CPTs are continuous. The sensitivity of the clays is a factor in the SPT interpretation. Without any information on the size of the site, spread of the field tests, I can...

Do you have staff who witnessed the complications with the soil profile, observed the Contractor making every attempt to deal with them using standard equipment, and then finally as a last resort, give him written permission to bring on heavier equipment to deal with the situation? My local...

Ditto to both of the above. Are you not preparing a bulk earthworks platform prior to piling the foundations? Or are you suspending structures over the 30 degree slope, which I'm assuming is a natural slope as opposed to a fill embankment? Your post suggests it's quite a large development, so...