Question

1) Determine ODOT flexible pavement section for an urban arterial road (ADT< 1500) with the following properties: Subgrade CBR = 4 ESALS = 6,000,000 2) Determine the Effective k for the following: Subgrade CBR = 5 5" Item 304 Aggregate Base 3) Determine the ODOT Rigid Pavement Design for an urban freeway with asphalt shoulders given the following: 8" ODOT Item 304 Aggregate Base Subgrade CBR = 4 ESALS = 50,000,000 - 25 year Design Life

Answer 1

Hi there, kindl post only one question at a time. These questions are quite involved and we need spend time to explain many things, and we get credit per question. I will try to answer two questions.

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Question 1)

for CBR = 4, resilient modulus = 1500*CBR = 6000psi

ESALS = 6000000

assume its a 3 layered design with Structural Number 5.

Assume that the pavement is 95% reliabile, and an overall standard deviation of 0.40

Now use the flexible pavement design formula to calculate the thickness. This formula is known to be

108 10 + APSI 4.2-1.5 log 10 (W18) = 2,ⓇS,+9.36 xlog 10(SN+1) - 0.20+ 1094 0.40+ (SN + 1) 519 +2.32x log10(M)-8.07

where SN = WE NEED TO FIND THIS

W₁₈ = predicted number of 18 kip loads i.e ESALs = 6000000

Z_R = -1.645, S₀ = combined standard error of traffic prediction and performance predictions we assume it to be 0.40

Delta PSI = difference between initial design serviceability index P₀ and terminal design serviceability index P_t (assume initial index = 4.5 and terminal serviceability index = 2.5

= 4.5 - 2.5 = 2.0

So we get S = 3.9413

ZR So SN APSI MR 6000 log10 W 18 6.778200275 W18 calculated 6000677 W18 actual 6000000 -1.645 0.4 3.9413 2

So your design should be such that the STRUCTURAL NUMBER OF PAVEMENT = 3.9413

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QUESTION 2)

Subgrade CBR = 5,

We know relationship between CBR and modulus of subgrade reaction is given by

1000 100 California Bearing Ratio, CBR (%) General soil, Indonesia Standard 2003 Lime Treafted Ferro Laterite Soil, Sang Z, et al., 2017 Cement Treated Sediment Soil, Yusuf H. let. al., 2013 10 1 0 20 120 140 40 60 80 100 Subgrade Modulus,k (kN/m²) per mm

So for CBR = 5, subgrade modulus is approximately = 30 Kn/m2/mm = 30 * 10⁶ N/meter³ = 110.518 pci

so k value = 110.518 pci

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Please post question 3 separately and I will answer it.

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