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An evaluation of a two-lane pavement has been performed. Deflection measurements were carried out in one outer wheel path. These measurements were done using a falling weight deflectometer FWD. The load applied was 50 kN, the diameter of the loading plate is 300 mm and the loading time was 0.02 s. The temperature of the asphalt during the tests was 25 °C. The deflection measurements every 250m are provided below. The bottom two lines give the average and standard deviations respectively. All deflections are given in μm. loc DQ DO.2 DQ.3 DQ.6 DQ.9 D1.2 D1.5 D1.8 D2.1 1 474 2 512 3 380 4 415 5 508 6 465 7 369 8 423 9 409 10 359 11 473 12 516 13 417 14 393 15 355 16 437 17 435 18 470 19 366 20 304 Ave 424 Stdev59 282 300 219 236 343 318 218 284 281 239 266 285 253 250 252 291 291 344 206 185 267.15 43 237 194 155 257 208 163 178 138 106 194 149 111 302 244 195 278 227 186 175 135 105 239 202 171 244 208 176 207 174 145 210 149 109 228 158 111 214 156 112 208 173 144 221 192 166 240 186 149 245 194 154 295 231 186 164 132 104 154 125 101 224.5 178.75 142.45 41 35 32 125 127 83 84 156 152 83 144 148 121 82 82 83 119 142 121 123 151 83 82 114.55 29 101 101 67 66 126 126 67 123 125 101 65 64 64 100 122 99 100 124 67 67 93.75 25 84 82 55 53 104 105 55 105 106 85 53 52 52 84 105 83 83 104 55 56 78.05 22 70 69 46 45 87 89 46 90 91 72 45 44 44 72 91 70 70 88 46 47 66.1 19
The pavement shows significant crocodile cracking at locations 1, 2, 5, 6, 10, 11, 12, 20. Pumping appeared to have occurred at locations 1, 2, 11, 12. At these locations also permanent deformation developed to a depth of around 10 - 15 mm. Only at location 12 the rut depth is 20 mm. The falling weight deflection tests were taken at a temperature of 25°C. It may be assumed that the pavement temperature is the same as the air temperature. The distance between the different deflection test locations is 250 m. Two test pits were made, one on location 12 and one on location 14. Some of the observations made were as follows: Asphalt layer Location 12 Subgrade Good condition, firm Layer was cracked and there appeared to be no adhesion between the asphalt layer and the base. Asphalt pieces looked very dry and hardened. Base layer In a fairly sound condition. Appears to be a G3 material. Two DCP test were taken after the asphalt layer was removed and before making the test pit. One reading gave a DCP value of 5 mm/blow and the Subbase layer Not in a very good condition. Material easily came loose and showed signs of crumbling it. The two DCP values that were obtained for this layer were 3 mm/blow and 1.5 mm/blow other one of 8 mm/blow
14 Asphalt layer showed good adhesion with base. No cracks visible. Mixture looked dry and is probably hardened significantly. Because the layer was not cracked it was possible to take cores and have them analyzed in the lab on composition. The following results were obtained: void content 6%, bitumen content 10% by volume, Penetration 32, Softening point = 60 °C. From the construction records it is known that the penetration of the bitumen immediately after construction was 50. Most probably G2 type material. Sound condition Two DCP tests were taken and both readings showed values of less than 1mm/blow Very good condition. Hard layer showing no signs of crumbling. DCP test was not very useful because of low penetration. Fair condition but being a bit moist.
The original pavement has been designed assuming the following values: Asphalt surfacing: Haspahlt = 40 mm, Easphalt = 2700 MPa, G2 base: Hbase = 150 mm, Ebase = 400 MPa, C3 subbase: Hsubbase = 250 mm, Esubbase= 3500 MPa, Subgrade: Esubgrade = 150 MPa and was supposed to last between 3 - 10 million repetitions of an 80 kN axle (TRH 14, ES8 or SAPEM ES10, Road Cat A, granular base - dry region). A recently performed traffic count indicated that the road is travelled by 5000 vehicles per day per direction and that the percentage of heavy vehicles was 20%. The composition of the fleet was such that on average each heavy vehicle had two 80 kN axles. The road was 15 years in service at the time of the traffic counts and deflection analysis. The traffic growth has been evaluated as 6% per year.
Questions: a) Plot a figure showing the series of deflection values at different locations loc i.e. deflection value Y-axis versus location loc value on X-axis ; for a series of geophone offsets 8, (in the legend). [5] b) Determine the cumulative sums plot for the maximum deflection and the surface curvature index SCI or BLI being do- d0.3 repeat this exercise for MLI and LLI. [6] c) How would you approach your residual life analysis and design of maintenance strategy? Would you do that based on homogeneous sections and if so, which sections would you discriminate? Please explain the reasons for your decision.[3] d) If you would decide not to use homogeneous sections which approach would you follow? Hint 1: you might decide to give some locations a special treatment. Hint 2: it might be an idea to first calculate the deflection profile of the structure as designed and to determine the lifetime of that pavement. Furthermore, you could have a look into the combination of deflection and thickness information. [6] e) Prepare a strip map for the composite pavement evaluation data for the entire road. Use a selfmade spreadsheet [6] f) Determine the amount of 80 kN axle loads that have been applied on the pavement during the 15 years life span. [4] g) Propose a maintenance strategy that extends the pavement life with another 15 years. Provide the full summary of your (rehab) design methodology using the SAMDM design method (Theyse et al). Provide the required Rubicon outputs with the LET tool. Copy and paste the relevant outputs in the final assignment [8]