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PRESENTATION ON FLOATING ROADS BY MARTIN HMENSA DEPARTMENT OF FEEDER ROADS, GHANA.
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Transcript of PRESENTATION ON FLOATING ROADS BY MARTIN HMENSA DEPARTMENT OF FEEDER ROADS, GHANA.
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.