Converting Modified to Standard Proctor
Converting Modified to Standard Proctor
(OP)
Does anyone know of a conversion from modified proctor to standard proctor for both dry density and moisture? I usually assume 90 modified = 95 standard, but I need something I can hang my hat on for this particular case, hopefully with a reference. I also assume moisture is a couple percent higher with standard. This is for pretty clean sand SP to SP-SM.
Thanks
Thanks





RE: Converting Modified to Standard Proctor
It would be a lot easier just to spend $150 and run another Proctor...then you'd know and wouldn't have to guess.
RE: Converting Modified to Standard Proctor
RE: Converting Modified to Standard Proctor
RE: Converting Modified to Standard Proctor
You simply don't know what the effect of the additional compaction energy will be for a particular soil.
AS BigH points out, there could be empirical correlations based on long experience with a particular soil type in a particular location.
I would be very suspicious of a geotech telling me there was a specific correlation between standard and modified (unless it was someone very trustworthy, like BigH).
RE: Converting Modified to Standard Proctor
In front of me I have comparative Proctors Ranging from less than 1% for an excellent, prepared Road Base and up to almost 12% for a High Plastic Clay.
ASTM C-1479-07a, Standard Practice for Installation of Pre-cast Concrete Sewer, Storm Drain and Culvert Pipe Using Standard Installations contains an interesting table (Table 3 Equivalent USCS and AASHTO Soil Classifications for Soil Designations) of approximate correlation between the Standard & Modified Proctors.
For Granular, relatively good soils (sands & gravels) the percent compaction differences are 5% between Standard & Modified Proctors.
For Fine Grained, plastic, relatively poor soils (clays & silts) the percent compaction differences are 10% between Standard & Modified Proctors.
This table was probably considered to be rather conservative for the purpose of the Standard. Also note that support of the pipe by the backfill is the ultimate criteria. Every type of construction should carefully consider the specifications with the actual needs.
BigH - this ties in nicely with your find, posted in the Foundations by Terzaghi forum: The Story of Buried Steel Pipes and Tanks, which you may find appropriate to link in this forum.
RE: Converting Modified to Standard Proctor
RE: Converting Modified to Standard Proctor
https
RE: Converting Modified to Standard Proctor