EVALUATION OF BEARING CAPACITY OF SOIL LAYERS
This project dealt with the evaluation of bearing capacity of soil layers using standard penetration test as a guide, a case study of Owerri federal constituency which comprises Owerri North, Owerri West and Owerri Municipal, Imo State. It is carried out to ascertain the bearing capacities of soil existing in above three locations namely; Owerri North, Owerri West and Owerri Municipal all in Owerri Federal Constituency of Imo State. Standard penetration test was used among other methods due to its simplicity. Soil samples of one meter and two meter depths were collected from three locations under study. The soil samples were tested for the bulk density, dry unit weight, natural moisture content and finally with the use of Terzaghi’s general equation qf = CNC+rD+Nq1/2rBNr, the bearing capacities of the soil samples were calculated and analyzed. From the results of the experiments, it was observed that Naze and Uratta representing Owerri North have the maximum bearing capacities of 1046KN/M2 and 1417KN/M2 which attributed to their high resistance to structural load.
1.1 BACKGROUND OF THE STUDY
The term Bearing Capacity is the largest intensity of pressure which may be applied to a structure to the soil without causing failure of soil in shear or excessive settlement.
All the Engineering structures such as Dams, Buildings, Bridges, Culvert, etc are founded on the soil and their loads are transferred to the underlying sub-strata through foundations. To ensure safe transfer of the load to the underground soil in such a manner that no shear failure or excessive settlement occurs, there is need to ascertain the bearing capacity or the resistance of the sub-strata.
Because of the structural collapse which is becoming rampant, this project research is channelled towards the evaluation of bearing capacity of the different soil layers to ascertain their resistance to structural load.There are other methods of evaluating the bearing capacity of soils such as:
Plate Load Test
Cone Penetration Test
But the method employed in this project is Standard Penetration Test due to its simplicity.
There are many types of Bearing Capacity which include:
Allowable Bearing Capacity which deals with the maximum pressure applied to the soil such that the induced stress in the soil is lesser than its capacity and the settlement in the soil is within the tolerance limit of the super structure.
1.2 AIMS AND OBJECTIVES OF THE STUDY
The purpose of this project is to determine the bearing capacity of soil layers existing in different locations within the Owerri Federal Constituency.
As the bearing capacity of soil layers vary from place to place and with depth, this project work will assist Engineers in recommending the type of structure to be erected on any part of the soil within the Owerri Federal Constituency.
Another objective of this study is in comparison with its case study at three locations thus: Nekede, Naze and Owerri municipal all in Owerri Federal Constituency.
This project work will also help to bring to the knowledge of the stake holders the soil strata and the depth to which foundations have to be safely established for effective transfer of structural load to the soil.
1.3 SCOPE OF THE STUDY
While carrying out this project on the bearing capacity of soil layers, soil samples were collected from these locations; Nekede, Naze and Owerri municipal all in Owerri Federal Constituency of Imo State for analysis. The scope of this project work involves going to the three locations for the collections of soil samples, laboratory test, experimentation and analysis of data using standard penetration test as a guide and finally the result of the analysis.
1.4 DEFINITION OF TERMS
COHESION (C): This is defined as the frictional resistance between soil grains.
ANGLE OF INTERNAL FRICTION(Q): This is defined as the angle occurring between the base and the shear plane.
BULK DENSITY ( w): This is the mass of the dry soil material including the solid particles and any contained water to its volume including voids.
DRY DENSITY ( d): This is the mass of the dry soil material after drying to a constant weight at 105OC contained in a unit volume of undried material.
MOISTURE CONTENT (w): This is the quantity of water which can be removed from the soil by heating at 105OC expressed as a percentage of the dry weight.
Nr, Nc, Nq: These are defined as the dimensionless bearing capacity factors which depend on the angle of material friction. ?.
NET ULTIMATE BEARING CAPACITY (Qnm): This is the minimum net pressure intensity causing shear failure of soil.
NET FOUNDATION PRESSURE (Qnf): This is the total foundation pressure less the effective weight of the soil permanently reduced.
NET SAFE BEARING CAPACITY: This is the bearing capacity divided by factor of safety.
ANGLE OF OBLIQUITY: This is defined as the angle formed by the resultant of frictional force and downward vertical force with the normal to the plane.
EVALUATION OF BEARING CAPACITY OF SOIL LAYERS