7/25/2019 Design CBR and R Modulus

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1. A minimum of 6 to 8 values are usually used to determine the design subgrade resilient

modulus. Design resilient modulus is defined as the modulus value that is smaller than

60, 75, or 87.5 % of all the test values.

ESA !esign "# 

$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$

10&  60

10& ' 106  75

(106  87.5

). *he results of eight tests +rodued the follo-ing subgrade resilient modulus values &).8,

5/.8, 60.7, 65.6, 6.0, 78.0, 8).1 and /.) "+a. !etermine the design subgrade resilient

modulus for ESA of 10&, 105 and 106.

Design Reliability

or eah of the uniform setions, the 23# design value must be alulated using the

reliability of the road ategory. *here are t-o basi methods that an be follo-ed for suh

analyses

a4 Standard normal distribution method

*his method uses the assum+tion that the 23# results in a uniform setion are normally

distributed. *his is a reasonable assum+tion for most ases of subgrade onditions. *hereafter 

the method uses a basi statistial a++roah.

23# design ' . S

9here

23# design 23# design value given the reliability of the uniform setion

average 23# value of the subgrade in the uniform setion

statistial oeffiient for a given level of reliability

S standard deviation for the 23# values in the uniform setion