RESULTS AND DISCUSSION

SIEVE ANALYSIS

The particle size analysis shows that the percentages passing number 200BS sieve are 22.18% and 13.02% for borrowpits 1 and 2 respectively. These are shown in figure 1and 2
[CHART]
Figure 1: Particle size distribution for borrowpit 1
[CHART]
Figure 2: Particle size distribution for borrowpit 2

ATTERBERG LIMIT

The results show that borrow pit 2 has sandy particle sizes predominating. Hence the soil sample as a result of its particle size composition happens to be a cohesionless soil with no plasticity while pit 1 has liquid limit of 32.5%, plastic limit of 27.77%, plasticity index of 5% and shrinkage limit of 5.8%. The result is shown in figure 3. Federal ministry of works general specification requirements for roads and bridges (1997) recommend liquid limit not greater than 50% for sub-grade and not greater than 35% for sub-base and base course. Also, plasticity index not greater than 30% for sub-grade and not greater than 12% for both sub-base and base. From the soil samples, both borrowpits fall within this specification, thus making them suitable for sub-grade, sub-base and base material.
[CHART]
Figure 3: Liquid limit for borrowpit 1

4.3 NATURAL MOISTURE CONTENT

The natural moisture content for the soil samples are 9.7% and 5%. These values are suitable in accordance with Emesiobi (2000) which states the classification for moisture content for different soil types and indicate that natural moisture content in soil may range from below 5% to 50% in gravel and sand.

SPECIFIC GRAVITY

The Specific gravity of the samples are 2.60 and 2.67, these values are suitable in accordance with wright (1986) who states that the standard range of values of Specific gravity of soils lies between 2.60 and 2.80.

CALIFORNIA BEARING RATIO

The soaked CBR value for the soil samples are 70% and 66%. Federal ministry (1997) recommended soaked CBR for sub-grade and sub-base soils not less than 5% and 30% respectively. For the base (unsoaked and soaked CBR) not less than 80%. The result for soil samples shows that all the soils are suitable for sub-grade and sub-base course. The graphs are shown in Figure 4 and 5
[CHART]
Figure 4: CBR graph for borrowpit 1
[CHART]
Figure 5: CBR graph for borrowpit 2

COMPACTION

The maximum dry density for the soil samples are 1.82Mg/m3 and 2.096Mg/m3 while that of optimum moisture content are 16.24% and 13.5%. Figure 6 and 7 shows the behavior of the soil for compaction.
[CHART]
Figure 6: Compaction graph for borrowpit 1
[CHART]
Figure 7: Compaction graph for borrowpit 2

UNCONFINED COMPRESSIVE STRENGTH TEST

[CHART]Figure 8 shows the behavior of the soil samples for the strength test. The unconfined compressive strength qufor borrowpit 1 is 91.5kPa. This shows that the shear strength of the soil samples is adequate for use as either a foundation or sub-grade material. Borrowpit 2 has no unconfined compressive strength value because it is a sandy material and a cohesionless soil does not form an unsupported cylindrical shape
Figure 8: Unconfined compressive strength graph for borrowpit 1

CLASSIFICATION OF THE SOIL SAMPLES

According to AASHTO soil classification borrowpit 1 can be classified as A-2-4 material (silty or clayey gravel and sand). They are rated as good materials for sub-grade material; it also satisfied condition for construction materials while borrow pit 2 can be classified as A-3 material (fine sand) which is non-plastic. They are also rated as excellent to good material for sub-grade.

CONCLUSION

From the tests carried out on the soil samples obtained from the two borrow pits around Afe Babalola university, Ado-Ekiti, Ekiti State Nigeria. The sieve analysis shows that the samples have less than 35% passing 200BS sieve. Borrowpit 1 contains silty or clayey gravel and sand while borrowpit 2 contains fine sand. The unconfined compressive strength of borrowpit 2 could not be obtained as it is a sandy material. Hence borrowpit 1 can be classified as A-2-4 material (silty or clayey gravel and sand) while borrowpit 2 can be classified as A-3 material (fine sand).
The samples are granular materials which can be used as a subgrade and subbase materials.

RECOMMENDATION

Soil samples should be collected and taken to the laboratory for testing before the commencement of earthworks on site. Further geotechnical investigation can also be done on other borrowpits at Bank road, Ilawe road, Iworoko road, and Ikere road, Ado-Ekiti, South Western Nigeria.