huangyhg

how can determine subgrade modulus
if i have beareaing capacity ( 10 tn/m2 ) , how i can determine the value of ( subgrade modulus ) for this soil
do a plate load test.
. . . and then the fun begins . . .
bigh...i forgot to mention you then have to figure out what it means!
bigh,
please rescue me if i slip.
the allowable soil bearing pressure is given for a max. settlment of 25mm (1"), so, conservativle, we can assume that the modulus of subgrade reaction is 40x abp (in metric units) or equal to abp (in us units). sounds basic so far right?
my question is: is factor of safelty used for the allowable bearing pressure incororated before the 1" settlement or after. in other words, what caused the 1" settlement: the abp or abpx sf?
since i'm exclusively a structual guy, my tendency is to always ask a geotech guy about subgrade modulus.... by the way, it is often difficult to get them to commit to a value (probably because is soil is never really elastic). that's why my old company always made sure that providing this was part of the contract.
josh
i would think the elastic modulus would be a good bit stiffer than indicated by the maximum settlement figures.
ailmar - the allowable bearing pressurefff"> is, in my view a serviceability issue (viz., settlement). there is no "factor of safety" on it other than conservatism in estimating the settlements under the bearing pressures. allowable bearing capacityfff"> is based on shear and, of course there is a safety factor involved or load reduction factors (coming at it from the other end).
the net allowable bearing pressure to get 25 mm settlement is really size dependent as well. as the footing gets larger, with the same bearing pressure (and assuming consistent soil behaviour below), the settlements will obviously increase. this is why you will many times see a curve of allowable bearing pressure (for service limit) vs width of footing.
you can determine the "operative" subgrade modulus at your bearing pressure from knowing the settlement vs pressure curve for each size of footing.
hope this makes sense? i've got sliding and seepage on the mind today . . .
carlb: - but you blew it by apologising!!
thank you (ailmar) & please tel me what you men ( abp ) ?
allowable bearing pressure (abp)

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