Asess your knowledge on computational procedures for

Question

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:

N_f = ((5620)/ε_l)^1.16

N_r = ((15000)/ε_c)3.95