Site Investigation is one of the first stages of any project and is conducted to determine the nature of the soil conditions. This determines whether the site is suitable for the proposed structure and enables the type and cost of foundations to be determined.
Conditions of the site should be known in advance so as to provide the interested parties with adequate information for optimal decisions to be made concerning methods that should be used in the exploration exercise.
In this project, in-situ tests were required to be undertaken supported by selected laboratory testing on bulk samples removed in boreholes thereafter support these findings by producing a description of the strata encountered in form of logs. At 0.00-3.00m artificially red gravelly compacted soil was encountered and from 3.00-10.00m the formation consisted of moderately to highly weathered Trachyte tuff.
The soils are described as A-7 clayey silty soil in accordance to AASTO classification system. This is as per the results from gradation distribution of soil that showed a percentage of 49% -71.9% passing through 0.0075m sieve. The soils contained maximum dry density of between 1653 to 1759 kg/m3 as indicated from the compaction test.
Finally in completion of the site investigation and laboratory testing programme, an interpretive report is produced setting out the results obtained including the calculations of the estimated bearing capacity of the strata encountered at various depths. From shear test safe bearing capacity was determined to be 230kPa from a depth of 1.500m-3.00m and 320kPa at a depth of 3.00-4.00m. Compressive strength of rocks obtained from site offer realistic evaluation of the bearing capacity of materials found on site, but a factor of safety should be applied to obtain the estimated bearing capacity. The safe bearing capacity values range from 483kPa to 1417kPa.