Its aim is to assess your knowledge on computational procedures for pavement structural evaluation and analytical overlay design.
Q1. A motorway section of length 7 km was tested with an FWD. Deflections were measured at 200 m intervals along the above section. The deflections were recorded at radial distances of 0, 0.6 and 1.5 metres from the centre of the load. The applied stress was 700 kPa and the radius of the loading plate was 15 cm.
The construction details of the pavement were as follows:
1. Layer 1: bituminous material, thickness 19 cm
2. Layer 2: granular material, thickness 40 cm
3. Layer 3: subgrade soil, good drainage conditions.
The temperature during testing was 200C.
The overall pavement condition should have been above average.
The deflection data were as follows:
Deflections (microns)
|
Chainage (km)
|
d(0)
|
d(600)
|
d(1500)
|
|
0.200
|
424
|
296
|
22
|
|
0.400
|
267
|
205
|
28
|
|
0.600
|
288
|
204
|
14
|
|
0.800
|
248
|
192
|
15
|
|
1.000
|
220
|
164
|
17
|
|
1.200
|
174
|
139
|
23
|
|
1.400
|
252
|
174
|
20
|
|
1.600
|
229
|
168
|
20
|
|
1.800
|
169
|
129
|
25
|
|
2.000
|
210
|
155
|
14
|
|
2.200
|
179
|
135
|
20
|
|
2.400
|
217
|
170
|
23
|
|
2.600
|
224
|
163
|
26
|
|
2.800
|
351
|
239
|
18
|
|
3.000
|
649
|
305
|
19
|
|
3.200
|
363
|
271
|
28
|
|
3.400
|
353
|
256
|
21
|
|
3.600
|
312
|
234
|
22
|
|
3.800
|
359
|
222
|
19
|
|
4.000
|
565
|
309
|
30
|
|
4.200
|
443
|
284
|
26
|
|
4.400
|
432
|
286
|
27
|
|
4.600
|
339
|
235
|
16
|
|
4.800
|
395
|
264
|
12
|
|
5.000
|
270
|
197
|
20
|
|
5.200
|
346
|
254
|
23
|
|
5.400
|
298
|
203
|
20
|
|
5.600
|
275
|
190
|
17
|
|
5.800
|
336
|
222
|
18
|
|
6.000
|
485
|
292
|
20
|
|
6.200
|
511
|
333
|
30
|
|
6.400
|
273
|
200
|
22
|
|
6.600
|
271
|
180
|
14
|
|
6.800
|
225
|
173
|
23
|
|
7.000
|
250
|
174
|
19
|
Useful note for tutor
You can solve it in this way
|
1
|
d(0)
|
d(600)
|
d (1500)
|
60
|
R
|
t1
|
t2
|
V
|
E1
|
E2
|
E3
|
d(0,c)
|
E
|
t
|
c
|
Nf
|
Nd
|
N
|
|
|
|
|
|
|
|
|
|
|
|
=2.5
|
Surface module concept
|
Seek function
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Q2
Using a spreadsheet, and both the Surface Modulus concept and the Method of Equivalent Thickness (MET) in a simplified manner, analyse the structural condition of the road section by estimating (a) the moduli of the layers and (b) their remaining life using the following relationships:
Nf = ((5620)/εl)1.16
Nr = ((15000)/εc)3.95