PRESENTATION ON FLOATING ROADS

BY MARTIN HMENSADEPARTMENT OF FEEDER ROADS, GHANA

OBJECTIVE

To share the successful results of constructing roads on peat with sand and gravel in Ghana.

BACKGROUND

• Request for access road to a fishing community at the coast

• Community cut off by two rivers, a stream and a lagoon/estuary

• Community near the confluence of two rivers • Request made for three bridges

• Length of stretch to be traversed was 450m.

STUDIES CARRIED OUT

• Profile of the depth of peat on stretch• Specific gravity of peat • Plasticity tests on gravel for fill• Quality of sand for fill• Salt and other chemical content of water• Highest level of water in lagoon• Effects of tides on highest water levels • type of vegetation and its effect.

SOME RESULTS OF THE TESTS/STUDIES

• Peat deeper than 4m all sections (Manual Auger Equipment used with little effort)

• Profile obtained at the other project site• Range of S.G of peat: 1.89 to 2.05 • Salt content: variable; ranges between 27.2% and

33.1% • Highest level of water estimated at 1.5m above ground.

TEST RESULTS ON PEAT

QUANTAB READING % NaCl S.G

4.8 33.1 1.89

4.6 30.1 1.90

4.8 33.1 2.05

4.4 27.2 2.00

4.65* 30.88* 1.96*

SOME RESULTS OF THE TEST ON THE GRAVEL FILL

Liquid Limit (LL) : Range : 27 to 33

Average : 30

Plastic limit (PL) : Range : 16 to 18

Average : 17

Plasticity Index (PI) : Range : 12 to 15

Average : 13

Maximum Dry Density : Range : 2020 to 2100 Kg/M3

Optimum Moisture content (OMC) : 7.9 to 10.7

Average : 10.0

CBR OF GRAVEL AT DIFFERENT COMPACTION EFFORTS

• 100% Proctor– Range: 63 to 96 (Average : 72)

• 98% Proctor– Range : 42 to 64 (Average : 53)

• 95% Proctor– Range : 19 to 27 (Average : 24)

• 93% Proctor– Range : 14 to 20 (Average : 18)

DECISIONS TAKEN AND

IMPLEMENTED • Bridges and viaducts not viable • A series of mass concrete pipe culverts selected • Peat in channels at river culvert positions

displaced with sand • Gravel used to fill other sections• Additional culverts to be constructed when

necessary.• Base of fill was broadened - 11m• Only the upper layers were compacted.

DCP TEST RESULTS OF FILL MATERIAL

DATE OF TEST: 11-12-2001ASEMASA – ANLO BEACHEQUIPMENT : DCP WR24900 AO1

LOCATION THICKNESS(mm) DEPTH(mm) INSITU CBR

8+200 LHS

1.8M FROM C/C

80

120

310

390

0-80

80-120

120-510

510-900

85.5

52.9

26.5

7.6

8+250 RHS

2.0M FROM C/C

310

280

310

0-310

310-590

590-900

41.8

10.8

7.2

8+300 C/C 340

560

0-340

340-900

52.9

20.6

8+400 RHS

2.4M FROM C/C

230

320

350

0-230

230-550

550-900

34.0

14.4

5.6

DCP TEST RESULTS OF FILL MATERIAL

DATE OF TEST: 11-12-2001ASEMASA – ANLO BEACHEQUIPMENT : DCP WR24900 AO1

LOCATION THICKNESS(mm) DEPTH(mm) INSITU CBR

8+400 LHS

2.0M FROM C/C

270

330

300

0-270

270-600

600-900

58.8

20.6

8.3

8+450 C/C 130

360

410

0-130

130-490

490-900

52.9

21.8

7.2

PROBLEMS ENCOUNTERED

• Objection of communities to relocation of road and loss of two bridges

• Observation of taboo days (Tuesdays)

• Demand for performance of rituals

• Equipment got stuck at sand pits

• Equipment got stuck in peat

• Slow rate of work

RECOMMENDATION AND CONCLUSION

• The floating has performed satisfactorily over a period of 8 years.

• Monitoring would be continued.• It is a cost effective option of providing access.• Perhaps this has been successful because ADT is

about 50vpd.• Take the risk to float a road under similar

circumstances to reduce cost and to provide access to deprived and isolated communities.