ANALYZING THE BEARING CAPACITY OF THE SOIL

ABSTRACT

The design of shallow foundations is based on the evaluation of the soil's bearing capacity. In order to develop an improved approximation of the foundation soil bearing capacity a numerical modelling method that better represents the soil's constitutive behaviour is required. This study is to analyse the bearing Capacity of soil for shallow foundation using Plaxis 3D a case study of School of Basic Medicine Site, University of Benin, Benin City. Soil samples were obtained from four boreholes at a depth 1m and 2m for each borehole from School of Basic Medical Sciences at complex, University of Benin. Index properties were carried out on the samples such as Bulk density test, moisture content test, specific gravity test, sieve analysis test, Atterberg limit test as well as strength or engineering properties test such as compaction and triaxial test were carried out on the samples. The bulk unit weight of the soil samples were determined to be 16.7 KN/𝑚3 , the natural moisture content (NMC) result is gotten to be 10.24%, the Specific Gravity (Gs) as 2.44, the liquid limit was obtained to be 38.90% Plastic limit as 22.26% and Plasticity Index as 16.23% which indicate that the soil is of medium plasticity. From sieve analysis, the soil was classified as an A-7-6 soil according to AASTHO (American Association of State Highway and Transportation) system classification. The OMC and MDD were 15.18% and 1.75g/cm3 respectively. The Triaxial tests results shows that cohesion C as 29.63KN/𝑚2 and frictional angle (phi) ∅ as 6.94.This indicates the soil is silt-clay soil. The safe bearing capacities obtained from Terzaghi’s analytical method of analysis was obtained as 191.11KN/𝑚2 and the safe bearing capacities from obtained Plaxis 3D as 186.27 KN/𝑚2 . Following from the results from Plaxis 3D software and Terzaghi’s analytical method, plaxis 3D gave a more conservative results having least safe bearing capacity for the analysis so this effect, the Plaxis 3D is suitable for analysing the bearing capacity of the soil for shallow foundation.