I. Answer each of the following statements with either True or False
Transcription
I. Answer each of the following statements with either True or False
I. Answer each of the following statements with either True or False (10 grades): 1. Interface deflection between two layers in a flexible pavement is inversely proportional to the modulus of the underlying layer. T 2. The slope variance of a pavement is an indication of rutting occurring in the pavement. F 3. As the vertical compressive strain on top of the subgrade layer decreases, the number of load applications to rutting failure decreases. F 4. Fatigue cracking is a non-load related cracking pattern that occurs in flexible pavements. F 5. The structural behavior of a pavement is related to the ability of the pavement to satisfy the needs of the users of the pavement. F 6. The present serviceability index (PSI) of a pavement is an index determined based on ride quality ratings made by a panel of raters. F 7. The performance index of a pavement is the PSI versus time. T 8. Transfer functions are distress models used to convert pavement responses into pavement performance. T 9. Skid resistance of an asphalt pavement is affected by bleeding distress occurring on the surface of the pavement. T 10. Distresses are considered the major correlation factor for computing the PSI of a pavement. F II. Please complete each of the following statements (20 grades): 1. The slope variance of a pavement is an indication of wheel path roughness ……………………….. in the pavement. 2. According to research studies in the US, the pavement longitudinal profile or roughness ………………………… provides the major correlation variable for computing PSI. 3. As the tensile strain at the bottom of the HMA layer increases, the number of load applications to fatigue failure decreases …………………. 4. As the vertical compressive strain on top of the subgrade layer decreases, the number of load applications to rutting failure increases…………………. 5. In flexible plate theory for flexible pavements, the pressure ………………. is the same at all points on the plate but the deflection ……………….. is different from point to point under the plate. 6. In case of a stabilized base layer used in an asphalt pavement, the critical response for fatigue cracking is the tensile strain at the bottom of the stabilized base layer …………………………. 7. Interface deflection between two layers in a flexible pavement is inversely proportional to the modulus of the second (underlying) …………………… layer. 8. A smoother pavement will have a higher ……………….. PSI. 9. Transfer functions are distress models used to convert pavement responses into pavement performance or distress ……………………….. III. In a Marshall test, the percentage of asphalt binder by total weight of aggregate is 5.2 percent. The bulk specific gravity of aggregate (Gsb) = 2.525, the specific gravity of asphalt binder (Gb) = 1.000, and the density of water w) = 1.000 g/cc. If the absorbed asphalt (P ba) is 1.8 percent by total weight of aggregate, and the voids in total mixture (VTM) is 4.0 percent, answer the following questions (30 grades): Va = VV Air Vma Asphalt Vfa = Vbe Vb Vba Vmb = VT Vmm Vsb = VAgg-bulk Aggregate Vse Vsa 1. The effective asphalt content (Pbe), percent by total weight of mixture equals to …………………3.23 %. 2. The bulk specific gravity of the compacted mixture (Gmb) is ……………….2.348. 3. The voids in mineral aggregate (VMA), percent by total volume of mixture equals to ………………………..11.59 %. 4. The theoretical maximum specific gravity of the loose mixture (Gmm) is ……………….2.446. 5. The voids filled with asphalt (VFA), percent by volume of total voids is …………………..65.49 %. IV. A circular loading is applied on a three-layered asphalt pavement system as shown in the figure below. If the radial tensile strain on the top of the subgrade layer is 215 microstrains, the radial tensile strain at the bottom of the asphalt layer is 304 microstrains, and the vertical compressive stresses at the bottom and top of the base layer are 3.2 psi and 10.8 psi, respectively, answer each of the following questions (30 grades): a q HMA, E1 = 250,000 psi h1 Base, E2 = 12,500 psi h2 Subgrade, E3 = 6,250 psi Note: Use –ve for tension and positive for compression. The required stresses and strains are under the centerline of the wheel load. 1. The vertical compressive strain (in microstrains) at the bottom of the asphalt layer is 608 ………………… 2. The vertical compressive strain (in microstrains) at the top of the base layer equals to 608 …………………….. 3. The vertical compressive strain (in microstrains) at the bottom of the base layer is 430 ………………………… 4. The vertical compressive strain (in microstrains) at the top of the subgrade equals to 430 ………………………….. 5. The radial tensile strain (in microstrains) at the top of the base layer equals to 304 ……………………….. 6. The vertical compressive stress (in psi) at the bottom of the asphalt layer is 10.8 …………………… 7. The radial tensile stress (in psi) at the bottom of the asphalt layer is equal to 141.2 ……………………….. 8. The radial compressive stress (in psi) at the top of the base layer equals to 3.2 ………………………….. 9. The radial tensile stress (in psi) at the bottom of the base layer equals to 2.2 …………………………….. 10. The radial compressive stress (in psi) at the top of the subgrade layer is 0.5 …………………………..