Determination of the Bearing Capacities of Sandstone and Shale Lithologies from Shear Wave Velocity in the Niger Delta Sedimentary Basin, Nigeria

摘要

The bearing capacities and coefficient of subgrade reaction of sand and shale lithologies of Niger Delta sedimentary basin, Nigeria have been computed from shear wave velocities using a relatively simple formula. The shear velocities were obtained from five oil exploratory wells. The computed ultimate bearing capacities of the sand ranges from 3141.755 to 5593.447 kN m~(-3) with an average of 4367.601 kN m~(-3) while, that of the shale ranges between 2487.786 and 6335.588 kN m~(-3) with an average of 4411.687 kN m~(-3). The computed allowable bearing capacity of the sand varies from 1047.252 to 1864.482 kN m~(-3) while that of the shale lithology is from 829.262 to 2111.863 kN m~(-3). Furthermore, the estimated subgrade reaction for the sand varies between 41890.07 and 74579.29 kN m~(-3) while that of the shale is from 33170.48 to 84474.5 kN m~(-3). The results show that the bearing capacities of the sand and shale lithologies are very high. This may be attributed to high consolidation and compaction of the formations in the subsurface and thereby resulting in the stability of most foundations in the area. Although, the shale lithology has a high bearing capacities and coefficient of subgrade reaction yet it is not advisable to put foundation on it whenever it is close to the earth surface because when it has the ability to swell/contract whenever it absorb or looses water it.