|Title:||AN INVESTIGATION OF THE RELATIONSHIP BETWEEN STANDARD PENETRATION TEST AND SHEAR WAVE VELOCITY FOR UNSATURATED SOILS (A CASE STUDY OF THE EARTHQUAKE PRONE AREA OF THE ALBERTINE GRABEN)|
|Publication Type||Journal Article|
|Year of Publication||2014|
|Authors:||Robert TUMWESIGE, Anthony GIDUDU, Umaru BAGAMPADDE, Conor RYAN|
|Abstract:||When an earthquake occurs, seismic waves radiate away from the source and travel rapidly through|
the earth’s crust. When these waves reach the ground surface, they cause shaking that may last from a few seconds to minutes. The nature and distribution of earthquake damage is strongly influenced by the response of soils to dynamic loading. This response is controlled to a large extent by the dynamic soil properties such as stiffness, damping, Poisson’s ratio and density. The prediction of ground shaking at soil sites requires knowledge of the soil expressed in terms of shear wave velocity (Vs). It is preferable to measure Vs by in situ wave propagation tests. However, it is often not economically
feasible to conduct these tests at all locations. On the other hand the Standard Penetration Test (SPT)
is the most common in situ site geotechnical test which is carried out in most site investigations.
Hence a reliable correlation between Vs and SPT would be of considerable advantage, reducing the
cost of site investigations. This paper presents, therefore, the development of an empirical relationship between Vs and SPT N-value for the soils of Kasemene Oil exploration area located in Buliisa District in Uganda. As part of an attempt to mitigate the effects of earthquakes in the area, a model is needed to predict Vs required for site response analysis. The effect of correcting Vs and SPT N-values on the model was evaluated and the model was also compared with published models. The process involved correlating 273 data pairs of Vs and SPT N-values which were measured at the same depth. The extensive Vs measurement was carried out using the Multichannel Analysis of Surface Waves (MASW) technique. The SPT N-value data was measured from boreholes drilled within the boundaries of the MASW survey lines. Results show that the relationship between Vs and SPT N-value depends on the effective overburden stress, and that ignoring the influence of effective overburden stress creates bias in the model. It was also found out that none of the published models fitted the data well and there is tremendous difference in the Vs values predicted by these models. The model exhibits good prediction performance and can be used to predict shear wave velocity for soils within the study area or for areas with a similar soil type.