EFFECTOFWATERTABLEVARIATIONSONSOILSTRENGTH PARAMETERS.

This research investigates the geotechnical implications of water table fluctuations on the stability of near-surface soil strata by evaluating the relationship between fundamental soil index properties and measured shear strength parameters. Laboratory testing on soil samples recovered from 1.0 meter and 2.0 meter depths from warri, encompassing Specific Gravity (Gs),Compaction,AtterbergLimits,andTriaxialCompressiontests. The analysis revealed a critically poor soil profile characterized by low Specific Gravity (Gs < 2.54) and negligible cohesive strength (C as 0kPa}) across both strata, strongly indicating the presence of organic or highly compressible lightweight solids. The study's primary finding is the exceptionally low angle of internal friction (19.4 at 1.0 m and 16.7 at 2.0 m). This deficiency means that the soil's shear strength is entirely frictional and thus 100% dependentoneffectivestress. Theresultsdemonstratethatwatertableriseposesanacuteriskbycausingaseverereduction in�, leading to an immediate and significant loss of shear strength and bearing capacity, confirming the extreme moisture sensitivity of the subgrade. Consequently, the soil is classified as unsuitable for foundation support without extensive ground improvement. Mitigation recommendations include removal and replacement or deep foundations to bypass the weak, high-risk zone, providing essential data for informed foundation design and geotechnicalriskassessment.