(c) A newly constructed 4 lane-highway failed after 3 years in service which is expected due to inadequate design. Therefore the thickness design is revised for investigation. At the time the road was designed, the total of commercial vehicles per day for both directions is 1000. The road was designed to last for 20 years and the traffic growth used was 5%. The mean CBR value of the rolling terrain subgrade is 11% with standard deviation of 2.5%. The damaged part of the road has been cut, drilled and measured. Detailed commercial vehicle classes from the axle load study and thickness of the pavement layers from the core samples are as follows: Axle load study for 24 hours: Class Percentage (%) 25 CVI 20 CV2 CV3 15 CV4 10 CVS 20 Core sample: Thickness, mm Layer Wearing course Binder course Road base Sub-base 40 80 150 300 Using the given tables (Tables Q4a-g), inspects the pavement thickness design and give your comments. (15 marks) EQUATIONS ESALy1 = ADT x 365 x PCV x LEFxLxT ESALDES= ESALYX [(1 + r)*- 11/r Vi = V:(1+r) Subgrade strength (60% probablity) = Mean - 0.253 x SD Subgrade strength (70% probability) = Mean -0.525 x SD Subgrade strength ( 85% probability) = Mean - 1.037x SD TABLE 04 Lane distribution factor, L Number of Lanes in one Lane distribution factor, direction) L One 1.0 Two 0.9 Three and more 0.7 TABLE 04b Terrain factor, T Type of terrain Terrain factor, T Flat Rolling 1.1 Mountainous/steep 1.0 1.3 factor CVI TABLE 04 Load equivalence factor Vehicle Load equivalence HPU class designation Class Buses (2 axles) 3.9 Buses (3 axles) CV2 2.8 Rigid vehicle (4 axles) CV3 Articulated trucks (3 axles) CV4 7.1 Articulated trucks (4 axles) CV5 6.1 2.6 Traffic Category TABLE 04d Traffic categories Design Traffic (ESAL 106) Probability (percentage) applied to properties of subgrade materials TI T2 300D TAHLE Q Class of subgrade strength CBR, Subgrade category Modulus, MPa Range Design input SGI S-12 SO-120 GO SO2 121-20 SO-140 120 SG3 2011-30 100-150 140 SG4 >30 120-150 180 TABLE 041 Pavement structure Trafie category based on million ESALSO KN Subgrade category. % 1 1-2 2.1-10 10.1-30 >>30 TI T2 T3 T4 TS BSC: 5 BSC: 14 BSC:S Subgrade improvement Subgrade improvement SGI: CAB: 25 CAB: 20 BC: 13 5-12 GSB: 15 GSB: 15 CAB: 20 GSB: 20 recommended recommended BSC: 5 BSC: 5 ESC: 5 BSC 5 BSC: 14 CAB: 20 SG2: CAB: 20 BC: 13 EC/BB: 15 EC/BB: 19 12.1-20 GS: 15 GSB: IS CAB: 20 CAR: 20 CAB: 20 GSB: 20 GSB: 20 BSCS GSB: 20 ESC:S BSC: 5 BSC: 12 ESOS SG3: CAB: 20 CAB: 20 BC: 13 BC/BR: 1S BO/BB: 19 20.1-30 GSB: 10 GSB: 10 CAB: 20 CAB: 20 CAB: 20 GSB: 15 BSC:S GSB: 15 BSC:S GSB: 15 BSCS BSC: S BSC: 10 CAB: 20 SG4: CAB: 10 BC: 13 BC/BR: 15 BC/BB: 19 >>30 GSE: 10 GSB: 10 CAB: 20 CAR: 20 CAB: 20 GSB: 10 GSB: 10 GSB: 10 Abbreviation Subbase GSB TABLE 04 Summary of abbreviation Designation Description Crushed granular material with maximuth 10% fies Crushed granular material with Crushed aggregate maximum 10% Course bituminous base mix (AC28) Binder course Coarse bituminous mix (AC28) Surface course: Dense graded Medium to fine bituminous mit (ACIO or AC14) CAB Bituminous BB BC BSC AC (c) A newly constructed 4 lane-highway failed after 3 years in service which is expected due to inadequate design. Therefore the thickness design is revised for investigation. At the time the road was designed, the total of commercial vehicles per day for both directions is 1000. The road was designed to last for 20 years and the traffic growth used was 5%. The mean CBR value of the rolling terrain subgrade is 11% with standard deviation of 2.5%. The damaged part of the road has been cut, drilled and measured. Detailed commercial vehicle classes from the axle load study and thickness of the pavement layers from the core samples are as follows: Axle load study for 24 hours: Class Percentage (%) 25 CVI 20 CV2 CV3 15 CV4 10 CVS 20 Core sample: Thickness, mm Layer Wearing course Binder course Road base Sub-base 40 80 150 300 Using the given tables (Tables Q4a-g), inspects the pavement thickness design and give your comments. (15 marks) EQUATIONS ESALy1 = ADT x 365 x PCV x LEFxLxT ESALDES= ESALYX [(1 + r)*- 11/r Vi = V:(1+r) Subgrade strength (60% probablity) = Mean - 0.253 x SD Subgrade strength (70% probability) = Mean -0.525 x SD Subgrade strength ( 85% probability) = Mean - 1.037x SD TABLE 04 Lane distribution factor, L Number of Lanes in one Lane distribution factor, direction) L One 1.0 Two 0.9 Three and more 0.7 TABLE 04b Terrain factor, T Type of terrain Terrain factor, T Flat Rolling 1.1 Mountainous/steep 1.0 1.3 factor CVI TABLE 04 Load equivalence factor Vehicle Load equivalence HPU class designation Class Buses (2 axles) 3.9 Buses (3 axles) CV2 2.8 Rigid vehicle (4 axles) CV3 Articulated trucks (3 axles) CV4 7.1 Articulated trucks (4 axles) CV5 6.1 2.6 Traffic Category TABLE 04d Traffic categories Design Traffic (ESAL 106) Probability (percentage) applied to properties of subgrade materials TI T2 300D TAHLE Q Class of subgrade strength CBR, Subgrade category Modulus, MPa Range Design input SGI S-12 SO-120 GO SO2 121-20 SO-140 120 SG3 2011-30 100-150 140 SG4 >30 120-150 180 TABLE 041 Pavement structure Trafie category based on million ESALSO KN Subgrade category. % 1 1-2 2.1-10 10.1-30 >>30 TI T2 T3 T4 TS BSC: 5 BSC: 14 BSC:S Subgrade improvement Subgrade improvement SGI: CAB: 25 CAB: 20 BC: 13 5-12 GSB: 15 GSB: 15 CAB: 20 GSB: 20 recommended recommended BSC: 5 BSC: 5 ESC: 5 BSC 5 BSC: 14 CAB: 20 SG2: CAB: 20 BC: 13 EC/BB: 15 EC/BB: 19 12.1-20 GS: 15 GSB: IS CAB: 20 CAR: 20 CAB: 20 GSB: 20 GSB: 20 BSCS GSB: 20 ESC:S BSC: 5 BSC: 12 ESOS SG3: CAB: 20 CAB: 20 BC: 13 BC/BR: 1S BO/BB: 19 20.1-30 GSB: 10 GSB: 10 CAB: 20 CAB: 20 CAB: 20 GSB: 15 BSC:S GSB: 15 BSC:S GSB: 15 BSCS BSC: S BSC: 10 CAB: 20 SG4: CAB: 10 BC: 13 BC/BR: 15 BC/BB: 19 >>30 GSE: 10 GSB: 10 CAB: 20 CAR: 20 CAB: 20 GSB: 10 GSB: 10 GSB: 10 Abbreviation Subbase GSB TABLE 04 Summary of abbreviation Designation Description Crushed granular material with maximuth 10% fies Crushed granular material with Crushed aggregate maximum 10% Course bituminous base mix (AC28) Binder course Coarse bituminous mix (AC28) Surface course: Dense graded Medium to fine bituminous mit (ACIO or AC14) CAB Bituminous BB BC BSC AC