Foundation Materials Bearing Capacity of Tombia Yenagoa, Bayelsa State Nigeria Using Multichannel Analysis Surface Waves Method

Geology

This study used Multichannel Analysis of Surface waves Method from data obtained in seismic refraction survey conducted along three profiles targeted in Tombia Town of Yenagoa Metropolis was processed with aid of Easy MASW software then analysed, evaluated and interpreted for sustainable design of infrastructure, shear wave velocities deduced were used to estimate various subsurface soil parameters of geotechnical significance such as N-value, ultimate bearing capacity, and allowable bearing capacity. From the results, shear wave velocity of the first layer depth 0.95 m -1.5 m across the study area was characteristically low and ranged between 100.50 m/s - 121.70 m/s in shear wave velocity with corresponding low values N-value ranged 1.84 – 2.83, ultimate and allowable bearing capacity 20.77 Kpa -36.40 and 1.74 Kpa – 1.93 Kpa. These values indicative of soft unconsolidated alluvial deposits generally considered incompetent to support a substantial structural load. The evaluated geotechnical parameters of the second layer depth 5.01 m – 5.64 m show a marked increase in all the parameters analysed with an appreciable ultimate and allowable bearing capacity value range of 297.92 Kpa – 447.51 Kpa and 2.63 Kpa -2.76 Kpa respectively. The third subsurface layer was delineated at a depth range of 12.99 m- 15.33 m with a variable thickness range of 8.03 m – 9.67 m. Thus, the first layer is not recommended for shallow footing and foundation designs for storey buildings while the second and third layers indicate they are fairly compacted and competent for support of multi-storey building constructions using either raft or pile foundation types.

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