Evaluation of liquefaction potential of some sites in Uyo metropolis, Akwa Ibom State, Southeastern Nigeria

Liquefaction potential analyses were carried out for some locations within Uyo metropolis, Akwa- Ibom state, Southeastern Nigeria using mostly cone penetration test data. The dominant soil is the Coastal Plain Sands. Unified Soil Classification System places soil within 20 m depth in the clayey sand (SC), silty sand (SM), poorly graded sand (SP) and dual combination of the three, namely SC-SM, SM-SP. Factor of safety (FS) was calculated for potential earth tremors with 7.5 and 4.5 moment magnitude and a peak ground acceleration (PGA) value of 0.16 g. Other than the first layer in some the sites in which values of FS is greater than 1.0, the factors of safety for the 7.5 magnitude for all depths up to 20.0 m are less than one. For the 4.5 moment magnitude, the FS is less than 1.0 in some layers and greater than 1.0 in others. Liquefaction potential index (LPI) values for the sites ranges from 1.94 to 26.65, this places the level of liquefaction severity for all the sites in the ‘very low’ to ‘very high’ category based on level of severity classification. Potential settlement of the liquefiable layers estimated at the sites ranges from 12.71 cm to 58.48 cm. Settlement values were used to correlate liquefaction zones. Liquefaction potential index has a coefficient of correlation of 0.51 with settlement values, whereas settlement values have a correlation coefficient ‘r’ of 0.9 with liquefiable layers thickness across all the sites. Liquefiable layers were correlated across three test sites using factors of safety and soil behavior index values. The implication of the study for structures in the area is that they should be constructed with an height to width ratio of less than 0.8, this will minimized damage to them in the event of an earthquake of 4.5 moment magnitude.