Explanation Given: Number of single axle traffic at 10 , 000 lb each are 300 . Number of single axle traffic at 18 , 000 lb each are 120 . Number of single axle traffic at 23 , 000 lb each are . 100 .. Number of tandem axle traffic at 32 , 000 lb each are 100 . Number of single axle traffic at 32 , 000 lb each are 30 . Number of triple axle traffic at 40 , 000 lb each are 100 . The reliability of the pavement is . 85 % . The overall standard deviation is 0.30 . The value of initial PSI is 4.7 The value of TSI is 2.5 . The drainage coefficient is 1 . The thickness of sand mix asphalt wearing surfaceis 4 inch . The thickness of soil cement baseis 6 inch . The thickness of crushed stone sub base is 7 inch . The design life of the pavement is 10 years . Formula Used: Write the expression for the structural number. SN = a 1 D 1 + a 2 D 2 M 2 + a 3 D 3 M 3 .....................(I) Here, a 1 is the structural layer coefficient of the hot mix asphalt wearing surface layer, a 2 is the structural layer coefficient of soil-cement base layer, a 3 is the structural coefficient of crushed stone sub-base layer, D 1 is the thickness of the wearing surface layer, D 2 is the thickness of the base layer, D 3 is the thickness of the sub-base layer, M 2 is the drainage coefficient for base and M 3 is the drainage coefficient for the sub-base. Write the expression for the 18 -kips equivalent single axle load. log 10 W 18 = [ Z R S 0 + 9.36 [ log 10 ( SN+1 ) ] − 0.20 + log 10 [ Δ PSI / 2.7 ] 0.40 + [ 1094 / ( SN + 1 ) 5.19 ] + 2.32 log 10 M R − 8.07 ] .....................(II) Here, Z R is the reliability, S 0 is the overall standard deviation, Δ PSI is the loss in serviceability from the time the pavement is new until it reaches its TSI, M R is the soil resilient modulus of the subgrade and W 18 is the 18 -kips equivalent axle load. Write the expression for the number of 25 -kips single axle load that can be carried before the pavement reaches it TSI. P = W 18 Equivalent Factor .....................(III) Here, P is the number of 25 -kips single axle load that can be carried before the pavement reaches it TSI. Write the expression for the total axle load factor. W n = A F n × Number of axles .....................(IV) Here, W n is the total axle load factor for a particular load, A F n is the axle load factor . Write the expression for the loss in serviceability. ΔPSI = Initial PSI − TSI .....................(V) Here, ΔPSI is the loss in serviceability. Write the expression for the total equivalent load. Total EL = W 10 s + W 18 S + W 23 S + W 32 S + W 32 Tandem + W 40 Triple .....................(VI) Write the expression for the 18-kip equivalent single axle load. W 18 = T L Equivalent × Design Life × 365 .....................(VII) Calculation: Refer Table 4.5 “Structural-layer coefficients” of the book “Principles of Highway Engineering and traffic, 6 th Edition” For the sand-mix asphalt, a 1 = 0.35 For the soil cement base, a 2 = 0.20 For the crushed stone sub base, a 3 = 0.11 Substitute 0.35 for a 1 , 4 for D 1 , 0.20 for a 2 , 6 for D 2 , 1 for M 2 , 0.11 for a 3 , 7 for D 3 and 1 for M 3 in equation (I). S N = ( 0.35 × 4 ) + ( 0.2 × 6 × 1 ) + ( 0.11 × 7 × 1 ) = 1.4 + 1.2 + 0.77 = 3.37 Refer Table 4.1 “Axle load equivalency factors for flexible pavement, Single Axles, and TSI = 2.5 ” of the book “Principles of Highway Engineering and traffic, 6 th Edition. The axle load equivalency factor corresponding to pavement structural number 3 and axle load 10 kips is 0.118 The axle load equivalency factor corresponding to pavement structural number 4 and axle load 10 kips is 0.102 Calculate the axle load equivalency factor corresponding to pavement structural number 3.37 and axle load 10 kips using interpolation. x = 0.118 − [ ( 3.37 − 3 ) ( 0.118 − 0.102 ) 4 − 3 ] = 0.118 − ( 5.92 × 10 − 3 ) = 0.11208 Substitute 0.11208 for AF 10 and 300 for Number of axles in equation (IV). W 10 S = 0.11208 × 300 = 33.624 The axle load equivalency factor corresponding to pavement structural number 3 and axle load 18 kips is 1 . The axle load equivalency factor corresponding to pavement structural number 4 and axle load 18 kips is 1 . Calculate the axle load equivalency factor corresponding to pavement structural number 3.37 and axle load 18 kips using interpolation. x = 1 − [ ( 3.37 − 3 ) ( 1 − 1 ) 4 − 3 ] = 1 − ( 0 ) = 1 Substitute 1 for AF 18 and 120 for Number of axles in equation (IV). W 18 S = 1 × 120 = 120 The axle load equivalency factor corresponding to pavement structural number 3 and axle load 22 kips is 2.17 . The axle load equivalency factor corresponding to pavement structural number 3 and axle load 24 kips is 3.09 . The axle load equivalency factor corresponding to pavement structural number 3 and axle load 23 kips is calculated as, Axle load factor = 2.17 + 3.09 2 = 5

The minimum acceptable soil resilient modulus.

EBK PRINCIPLES OF HIGHWAY ENGINEERING A

6th Edition

ISBN: 9781119299332

Author: WASHBURN

Publisher: JOHN WILEY+SONS,INC.-CONSIGNMENT

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The minimum acceptable soil resilient modulus.

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A highway has the following pavement design daily traffic: 300 single axles at 10,000 lb each, 120 single axles at 18,000 lb each, 100 single axles at 23,000 lb each, 100 tandem axles at 32,000 lb each, 30 single axles at 32,000 lb each, and 100 triple axles at 40,000 lb each. A flexible pavement is designed to have 4 inches of sand-mix asphalt wearing surface, 6 inches of soil cement base, and 7 inches of crushed stone sub base. The pavement has a 10-year design life, a reliability of 85%, an overall standard deviation of 0.30, drainage coefficients of 1.0, an initial PSI of 4.7, and a TSI of 2.5. What is the minimum acceptable soil resilient modulus?

Q/ A flexible pavement was designed for the following daily traffic with a 12-year design life: 1300 single axles at 8,000 lb each, 900 tandem axles at 15,000 lb each, 20 single axles at 40,000 lb each, and 200 tandem axles at 40,000 lb each. The highway was designed with 4 inches of hot-mix asphalt (HMA) wearing surface, 4 inches of hot-mix asphaltic base, and 8 inches of crushed stone subbase. The reliability was 70%, overall standard deviation was 0.5, APSI was 2.0 (with a TSI of 2.5), and all drainage coefficients were 1.0. What was the soil resilient modulus of the subgrade used in design?

A flexible pavement is designed to last 10 years to withstand truck traffic that consists only of trucks with two 18-kip single axles. The pavement is designed for a soil CBR of 10, an initial PSI of 5.0, a TSI of 2.5, an overall standard deviation of 0.40 and a reliability of 90%, and the structural number was determined to be 6. Determine the number of daily trucks traveling in the peak direction.

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The minimum acceptable soil resilient modulus.

Solution Summary: The author explains the minimum acceptable soil resilient modulus, which is 9.0times 103lb/

The minimum acceptable soil resilient modulus.

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