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ASSESSMENT OF THE UNSATURATED GEOTECHNICAL PROPERTIES OF SOME LATERITIC SOILS IN ADO-EKITI, SOUTH-WESTERN NIGERIA.UDUEBOR MICHEAL A.CVE/06/7988MAY, 2014Supervisor: prof. s.a. olaMy name is UDUEBOR MICHEAL A. with matric number CVE/06/7988.I am here to present my propositional seminar on the research topic ASSESSMENT OF THE UNSATURATED GEOTECHNICAL PROPERTIES OF SOME LATERITIC SOILS IN ADO-EKITI, SOUTH-WESTERN NIGERIA.1INTRODUCTIONUNSATURATED SOILSINTRODUCTIONOptimization of factors of construction is being harped upon more and more these days owing to the increased need for engineering infrastructure and the limited available material for the same.

One of the very first requirements in every building and construction effort is the maximization of limited available resources and the reduction of losses via avoidable expenses. Optimization of the factors of construction is being more and more emphasized due to the limited available material for construction.

If you dont minimize cost, the cost will minimize you Engr. O.S. Aderinola3INTRODUCTIONPart of the efforts at ensuring maximization of the limited resources has also been the recent look into the widely neglected area of unsaturated soil mechanics, with intent of ascertaining to a confident level the properties, characteristics and behaviour of soils in unsaturated soil conditions. One of the ways being looked into globally is the study of soils in their unsaturated states, with a view at trying to understand to a confident level their properties, characteristics and behaviour. This would further help us utilize the favourable factors therein. It has been found out by recent study that utilizing the soil at its optimum unsaturated state in construction can reduce the cost of a project by up to 70% (Minnesota Department of Transportation, 2007-11 Pavement Design Using Unsaturated Soil Technology). This is because there is an enhancement of the strength and other properties of the soil while in its unsaturated state.4AIM AND OBJECTIVESRESEARCH FOCUSAIM AND OBJECTIVESIn practice, several design and maintenance measures are undertaken to maintain unsaturated conditions because they provide favourable engineering properties. However, the conventional procedures for design are often based on empirical procedures and not on unsaturated soil mechanics principles.

Also worthy of note is the fact that although our design measures ensure that the worst case scenarios of complete submersion and saturation are taken care of, there is a seldom occurrence of this owing to the fact that we also place in measures to ensure that these worst case scenarios dont occur. Example is the use of cambering and drains on a road pavement alongside the elevation of the embankment above the water table.6AIM AND OBJECTIVESThe aim of this research is to determine the unsaturated geotechnical properties and behaviour of selected lateritic soils.The aim of this research is to determine the unsaturated geotechnical properties with a view at understanding the behaviour of selected lateritic soils under unsaturated conditions.7AIM AND OBJECTIVESThe objectives of the research include;Carrying out laboratory investigative tests to determine the unsaturated strength properties of the soils.Obtaining baseline information that would aid unsaturated soil mechanics calculations and evaluation.Comparing results with known models to check if they would prove valid, and if found otherwise create a model suitable to the selected soil.

The objectives of the research include;Carrying out laboratory investigative tests to determine the unsaturated strength properties of the soils.Obtaining baseline information that would aid unsaturated soil mechanics calculations and evaluation.Comparing results with known models to check if they would prove valid, and if found otherwise create a model suitable to the selected soil.

8JUSTIFICATIONWhy This Research?JUSTIFICATIONAs pointed out by Fredlund and Rahardjo (1993), classical soil mechanics and geotechnical engineering have been often taught with an implicit assumption that soil is either dry (0 per cent saturation) or saturated (100 per cent saturation).

As mentioned earlier soil mechanics and geotechnical engineering have been often taught with an implicit assumption that soil is either dry (0 per cent saturation) or saturated (100 per cent saturation). This is actually not true

10JUSTIFICATIONIn many engineering problems, however, a soil is often neither saturated nor dry. Relatively, limited research has been conducted on unsaturated soils so there is an urgent need to improve the understanding of the behaviour and mechanics of an unsaturated soil especially as regards to tropical soils.Compared to Classical soil mechanics, Relatively, limited research has been conducted on unsaturated soils so there is an urgent need to improve the understanding of the behaviour and mechanics of an unsaturated soil especially as regards to tropical soils. Majority of the work on unsaturated soils have been carried out in the United States and Canada with notable names like Prof. Fredlund, Prof. Ng which have all utilized native soils for their experimental studies.11SCOPE OF THIS STUDYThe Extent of This ResearchSCOPE OF THIS STUDYThe study intends to characterize the water retention characteristics curves, shear strength versus Suction for two tropical lateritic soils previously selected by Abe (2008). These would be carried out on each soil sample at several suctions and two compacted densities.For this study, two tropical lateritic soils previously selected by Abe (2008) would be used. It is expected that tests would be carried out at two compacted densities under varying suction conditions.1314LOCATION OF THE STUDY AREALocation of the ResearchLOCATION OF THE STUDY AREAThe study area is located in Ado-Ekiti, the Capital of Ekiti State, South-Western Nigeria. The area is readily accessible by a network of roads which also link the area with nearby towns.The two soils are located within Ado-Ekiti, the Capital of Ekiti State in Nigeria16Road Map of Ado-EkitiSource: Google Map, 2014

Map Showing Sample Location 1 (SL1), Abuja Hostel, Federal Poly., Ado-Ekiti.Source: Google Maps, 2014

SL1The first sample location is the Abuja hostel of the Federal Polytechnic, Ado-Ekiti18Map Showing Sample Location 2, (SL2) Health Centre along Igirigiri Road in Odo-Ado quarters, Ado-EkitiSource: Google Maps, 2014

SL2While the second location is the health centre along igirigiri road, odo-ado quarters also in Ekiti state. These two locations have been selected for the study because although they occur within the same region, their geologic formation and characteristics are distinct and different from each other Ebisemiju (1993).19EXPECTED CONTRIBUTION TO KNOWLEDGEAddition to KnowledgeEXPECTED CONTRIBUTION TO KNOWLEDGEAdd to knowledge in the area of unsaturated soil mechanics especially with a look at tropical soils.It would provide necessary baseline information for future research efforts into the behaviour of soils under unsaturated conditions.It is expected that this research wouldAdd to knowledge in the area of unsaturated soil mechanics especially with a look at tropical soils.It would provide necessary baseline information for future research efforts into the behaviour of soils under unsaturated conditions.

21EXPECTED CONTRIBUTION TO KNOWLEDGEProvide data necessary for the determination of the unsaturated shear strength properties and characterization of the water retention characteristics of the selected tropical soil which would serve useful in provision of a more economic design both in building and road construction worksDetermination of the unsaturated shear strength properties and characterization of the water retention characteristics of the selected tropical soil which would serve useful in provision of a more economic design both in building and road construction works

22MATERIALS AND METHODOLOGYResearch ProcessMATERIALSDisturbed and undisturbed lateritic soil samples from tests pits dug manually around the study area would be obtained with depths ranging from 1.0 to about 2.0 m deep. Twenty (20) soil samples would be categorized and labelled with respect to location and sample type. Predefined Soil Test Sample Categorization.LocationBeside Abuja hostel of the Federal Polytechnic (SL1)Health centre along Igirigiri road (SL2)Sample TypeNon Reworked Soil (NRS)6 SamplesNon Reworked Soil (NRS)6 SamplesTermite Reworked Soils From Top of Termitarium (TTRS)2 SamplesTermite Reworked Soils From Top of Termitarium (TTRS)2 SamplesTermite Reworked Soils From Bottom of Termitarium (BTRS)2 SamplesTermite Reworked Soils From Bottom of Termitarium (BTRS)2 SamplesMETHODOLOGYAs this study is concerned only with the unsaturated soil properties of the soil, little preliminary tests would be carried out. The tests required for determining the unsaturated soil properties of the selected soils are briefly outlined below. METHODOLOGYBulk Density Test (BS 1377- 4:1975)This test would be carried out both on the field and in the laboratory. This is to determine the in-situ bulk density of the soil in order to produce soil test samples with similar packing in the laboratory.

METHODOLOGYCompaction Test (BS 1377- 4:1975)The compaction test would be carried out to determine the maximum dry density of the soil samples for the given compactive effort and the moisture content at which it is achieved. This would provide a standard density for all the samples to be used in carrying out the test.

METHODOLOGYSWCC Test (ASTM D 6836 02)The Soil Water Characteristic Curve Test would be carried out in accordance with ASTM D 6836 02, the designated standard test method for the determination of the soil water characteristic curve using a pressure chamber with gravimetric measurement.

METHODOLOGYSaturationEquilibrationSuctionGravimetric Measurements

METHODOLOGYUnconsolidated Undrained (Triaxial) Test (BS1377-8:1990)Six (6) samples from both locations would be tested at five (5) different levels of saturation, making a total of thirty (30) tests to be carried out.

31METHODOLOGYA uniform pressure (being the calculated overburden pressure) would be applied to the soil, and the shearing process started immediately at a strain rate of 0.5mm/min without allowing any drainage of water. In this test there will be no dissipation of pore water pressure from the soil sample during the entire testing time.

32METHODOLOGYTests also would be carried out at varying strain rates to determine the effect of the rate of strain on the strength properties of the selected soil samples.

33PROJECT SCHEDULERESEARCH DURATIONPROJECT SCHEDULEIt is expected with a high level of allowance given for contingencies that the study would be concluded in sixteen (16) weeks, and average of four (4) months. The sequence of work for this research is outlined with specific durations indicated below.

35Sequence of WorkSequence of WorkDuration (Weeks)Visit to Study area, Recovery of soil samples, In-Situ soil test/investigation1Laboratory Tests, Analysis of Results10Collation, Correlations, Discussions, Report Writing3Thesis Report, Final Seminar2Total16THANK YOU FOR LISTENING