A flexible pavement is designed with 4 inches of sand-mix asphalt wearing surface, 6 inches of dense-graded crushed stone base, and 8 inches of crushed stone subbase. All drainage coefficients are 1.0. The initial PSI is 4.5, the TSI is 2.5, the soil resilient modulus is 12,000 lb/in², reliability is 90%, the overall standard deviation is 0.4, and the design life is 15 years. A design mistake was made that ignored 100 daily passes of trucks with 22-kip single and 30-kip tandem axles. What crushed stone subbase thickness should have been used? [Do not interpolate the axle equivalency factors, use the closest values]

A flexible pavement is designed with 4 inches of sand-mix asphalt wearing surface, 6 inches of dense-graded crushed stone base, and 8 inches of crushed stone subbase. All drainage coefficients are 1.0. The initial PSI is 4.5, the TSI is 2.5, the soil resilient modulus is 12,000 lb/in², reliability is 90%, the overall standard deviation is 0.4, and the design life is 15 years. A design mistake was made that ignored 100 daily passes of trucks with 22-kip single and 30-kip tandem axles. What crushed stone subbase thickness should have been used? [Do not interpolate the axle equivalency factors, use the closest values]

Traffic and Highway Engineering

5th Edition

ISBN:9781305156241

Author:Garber, Nicholas J.

Publisher:Garber, Nicholas J.

Chapter19: Design Of Flexible Highway Pavements

Section: Chapter Questions

Problem 11P

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A flexible pavement is designed with 5 inches of hot-mix asphalt (HMA) wearing surface, 6 inches of hot-mix asphaltic base, and 10 inches of crushed stone subbase. All drainage coefficients are 1.0. Daily traffic is 200 passes of a 20-kip single axle, 200 passes of a 40-kip tandem axle, and 80 passes of a 22-kip single axle.If the initial minus the terminal PSI is 2.0 (the TSI is 2.5), the soil resilient modulus is 3000 lb/in2, and the overall standard deviation is 0.6, what is the probability(reliability) that this pavement will last 20 years before reaching its terminal serviceability?
A rigid pavement is designed with a 10-inch slab,an Ec of 6 million lb/in^2, a concrete modulus of rupture of 432 lb/in^2, a load transfer coefficient of 3.0, an initial PSI of 4.7, and a terminal serviceability index of 2.5.The overall standard deviation is 0.35, the modulus of subgrade reaction is 190 lb/in^3, and a reliability of 90%is used along with a drainage coefficient of 0.8. The pavement is designed assuming traffic is composed entirely of trucks (100 per day). Each truck has one 20-kip single axle and one 42-kip tandem axle (the effect of all other vehicles is ignored). A section of this road is to be replaced (due to different subgrade characteristics)with a flexible pavement having a structural number of 4 and is expected to last the same number of years as the rigid pavement. What is the assumed soil resilient modulus? (Assume all other factors are the same as for the rigid pavement.)
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. On one section of this roadway, beneath an underpass, an engineer uses an 8-inch rigid pavement in an attempt to have it last longer before resurfacing. How many years will this rigid-pavement section last? (Given the same traffic conditions, modulus of rupture = 800 lb/in2, modulus of elasticity = 5,000,000 lb/in2, load transfer coefficient of 3.0 and drainage coefficient of 1.0.).
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, ¨PSI 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?
B. A rigid pavement with a 10-inch slab thickness, 90 percent reliability, E. = 4 million lb/in², 600 lb/in² modulus of rupture, 150 lb/in³ modulus of subgrade reaction, a 2.8 load transfer coefficient, initial PSI of 4.8, final PSI of 2.5, overall standard deviation of 0.35, and a drainage coefficient of 0.8 is designed. The pavement's design life is 20 years. The three-lane road is built for vehicles with one 20,000-pound single axle, one 26,000-pound tandem axle, and one 34,000-pound triple axle. Calculate the projected daily truck traffic on the three lanes.
A flexible pavement is constructed with 4 inches of hot-mix asphalt (HMA) wearing surface, 8 inches of emulsion/aggregate-bituminous base, and 8 inches of crushed stone subbase. The subgrade has a soil resilient modulus of 10,000 lb/in^2, and M2 and M3 are equal to 1.0 for the materials in the pavement structure. The overall standard deviation is 0.5, the initial PSI is 4.5, and the TSI is 2.5. The daily traffic has 1080 20-kip single axles,400 24-kip single axles, and 680 40-kip tandem axles. How many years would you estimate this pavement would last (how long before its PSI drops below a TSI of 2.5) if you wanted to be 99%confident that your estimate was not too high
A flexible pavement is constructed with 5 inches of sand-mix asphaltic wearing surface (a = 0.35), 9 inches of dense-graded crushed stone base (a = 0.18), and 10 inches of crushed stone subbase (a = 0.11). The base has a drainage coefficient of 0.90 while the subbase drainage coefficient is 1.0. Determine the structural number of the pavement. 3.98 4.47 4.76 4.31
A flexible pavement has a structural number of 3.8(all drainage coefficients are equal to 1.0). The initialPSI is 4.7 and the terminal serviceability is 2.5. The soilhas a CBR of 9. The overall standard deviation is 0.40and the reliability is 95%. The pavement is currentlydesigned for 1800 equivalent 18-kip single-axle loadsper day. If the number of 18-kip single-axle loads wereto increase by 30%, by how many years would thepavement’s design life be reduced?
A northbound direction on an interstate highway consists of four lanes of flexible pavement. It is conservatively designed with a 10-inch sand-mix asphaltic surface, 10-crushed stone base, and a 10-inch crushed-stone subbase (all drainage coefficients are 1.0). The subgrade CBR is 3, the overall standard deviation is 0.4, and the reliability is 95%. The initial PSI is 4.6 and the final PSI is 2.5. Daily total northbound road traffic consists of 51,000 cars (each with two 2-kip single axles), 840 buses (each with two 20-kip single axles), and 1,000 heavy vehicles (each with one 12-kip single axle and two 34-kip tandem axles). How many years was this pavement designed to last?
A rigid pavement on a new interstate (3 lanes each direction) has been conservatively designed with a 12- inch slab, an Ec of 5.5 x 106 lb/in2 , a concrete modulus of rupture of 700 lb/in2 , a load transfer coefficient of 3.0, an initial present serviceability index of 4.5, and a terminal serviceability index of 2.5. The overall standard deviation is 0.35, the subgrade CBR is 25, and the drainage coefficient is 0.9. The pavement was designed for 600 30-kip tandem axles per day and 1400 20-kip single axle loads per day. If the desired reliability was 90%, how long was this pavement designed to last?
A rigid pavement is being designed with the same parameters as used in Problem 4.5. The modulus of subgrade reaction is 300 lb/in? and the slab thickness is determined to be 8.5 inches. The load transfer coefficient is 3.0, the drainage coefficient is 1.0, and the modulus of elasticity is 4 million 1b/in?. What is the design modulus of rupture? (Assume that any parameters not given in this problem are the same as those given in Problem 4.5.) 4.5 for reference: A flexible pavement was designed for the following daily traffic with a 12-year design life: 1300 single axles at 8000 Ib each, 900 tandem axles at 15,000 1b each, 20 single axles at 40,000 Ib each, and200 tandem axles at 40,000 lb each. The highway was designed with 4 inches of HMA wearing surface,
A flexible pavement was designed to have a 6-inch sand-mix asphaltic surface, 8-inch soil-cement baseand a 21-inch crushed-stone subbase (all drainagecoefficients are 1.0). The pavement was designed for800 12-kip single axles and 1600 34-kip tandem axlesper day in the design direction. The reliability used was90%, the overall standard deviation was 0.35, initial PSIwas 4.7, the TSI was 2.5 and the soil resilient moduluswas 2582 lb/in2. If the road has three lanes in the designdirection (and was conservatively designed), for howmany years was the pavement designed to last?