Title 123 Pavement Design.pdf ✅

At the bottom of the subbase layer, the bearing material is the subgrade and x = tb + tsb. tsb = 0. 564√ W fsg − tb − r Where: t = thickness of rigid pavement W = static wheel load f = allowable bearing stress r = radius of contact area 2.3. Thickness of Pavements using other Provisions. The following methods use experimental data to determine the pavement thickness. • Expansion Pressure Method t = expansion pressure pavement density • California Bearing Ratio t = √W[ 1. 75 CBR − 1 Pπ] 1 2 • McLeod’s Method (Plate Test Method) t = K log P S Where: t = thickness of rigid pavement W = static wheel load CBR = California bearing ratio = stress for 5 mm penetration of soil stress for 5 mm penetration of standard K = McLeod’s constant P = wheel load pressure S = subgrade pressure An alternative method when using CBR is to use a graph. After the CBR is computed, project its value vertically at the graph until the appropriate curve is hit and shift horizontally to see the matching thickness. An example for CBR = 10% and type G traffic is shown below.
3. Other Parameters for Pavements 3.1. Shrinkage Factor The shrinkage factor of the soil is the ratio of its settlement to the original thickness (see HGE 17: Consolidation) SH = ∆H H = ∆e 1 + eo Where: ∆H = change in thickness H = initial thickness ∆e = change in void ratio eo = initial void ratio 3.2. Stiffness Factor ST = √ Eb Ep 3 Where: Eb = modulus of elasticity of subgrade Ep = modulus of elasticity of pavement 3.3. Modulus of Subgrade Reaction SR = stress deflection 3.4. Traffic Index. TI = 1. 35(EWL) 0.11 Where: EWL = equivalent wheel load 4. Joints and Reinforcements 4.1. Contraction Joints Contraction/construction joints are joints placed transversely across the pavement at regular intervals to release some tensile stress or to provide a suitable transition. Using summation of forces, ∑Fh = 0: tension = friction between pavement and soil fcBt = μN ∑Fv = 0: N = weight of pavement segment = γ ( L 2 ) (Bt) fcBt = μγ ( L 2 ) (Bt)