Geo-Trends Review

Hi All,

I'm working as a Consultant Engineer a query has arising on a project in relation to the Vibrating Hammer Check as described in Annex A of EN 13286-4:2021. This check requires a minimum dry density of 1.74Mg/m3 within a moisture content range of 2-3% being achieved for the hammer to be accepted.

A performance check has been conducted on a vibrating hammer proposed for use in the project. However, the required minimum dry density is not being achieved with an average dry density of 1.56Mg/m3 being measured in several performance checks. The hammer used is 1100W in excess of the required 600W with the load applied to the sample in the mould being 36kg, within the limits of 30-40kg. This check was repeated using different uncrushed sand samples from a site in Ireland that have been graded to the required specification (1kg of the soil retained on the 0.3mm sieve blended with 4kg of the soil retained on the 0.425mm sieve per sample) and the moisture content has been measured to be within the permitted range.

It is noted that in laboratory guidance by Head that the 1.74Mg/m3 value is only applicable for an unused sample of clean, dry silica sand from the Woburn Beds of the Lower Greensand in the Leighton Buzzard district and that other types of sand will give different results. Thus the thinking is that the specific gravity of the sand is affecting the result and not reaching compliance. It is noted that this is a Euronorm so I am curious to see has this resulted in queries by others.

Has anyone come across this previously or have insights on this topic? Any guidance would be much appreciated.

Hi Everyone,

Im working as a Consultant Engineer and have observed Nuclear Density Test results along with Sand Replacement Results which are slightly above the Zero Air Voids Line on a soil stabilisation project. Testing has been done to confirm the specific gravity of the natural untreated soil alongside checks on site to verify same soil used and the equipment used is functioning correctly. I have hypothesised that the addition of a nominal quantity of cement as part of the soil stabilisation process has resulted in the specific gravity increasing and thus raising the zero air voids line. Calculating the quantity of cement with a specific gravity of 3.15 to obtain the specific gravity indicated by the results however does not tally with the binder used on site. Could the reasoning be that there is a chemical reaction undergoing that is affecting the specific gravity?

Has anyone come across this previously or have insights on this topic? Any guidance would be much appreciated.