Determination Of Geotechnical Properties Of Soil For The Strip Foundation

Building Technology | Civil Engineering | Engineering

The determination of geotechnical properties of soil plays a crucial role in designing and constructing a strip foundation. Soil investigations, including tests such as Standard Penetration Test (SPT), Cone Penetration Test (CPT), and laboratory tests like grain size analysis, Atterberg limits, and shear strength tests, are essential to ascertain the soil’s characteristics. These properties, including soil type, compaction characteristics, moisture content, plasticity index, cohesion, angle of internal friction, and bearing capacity, significantly influence the design and performance of strip foundations. By accurately assessing these geotechnical properties, engineers can optimize the foundation design, ensure structural stability, and mitigate potential risks associated with settlement, differential settlement, or bearing capacity failure, ultimately enhancing the overall structural integrity and longevity of the construction project.

ABSTRACT

This study aims at establishing the sub-soil types and profile to ascertain the engineering characteristics of the underlying soils in Onne area of Rivers State, Nigeria and recommend appropriate foundation design and construction for large scale ground and elevated water storage facilities in the area. Four borings were accomplished using a percussion rig with the aid of augers. Representative samples were analyzed in the laboratory in accordance with relevant geotechnical engineering standards. Results of the study revealed that within the maximum depth of 15m of boring, the area was found to consist of about 0.2m thick of organic topsoil followed by light brown sandy-clay underlain by a light brown to yellowish brown fine to medium grained, medium dense sand up to 15m depth of investigation. The study also reveals that superficial light brown sandy clay is suitable in quality to carry shallow or raft foundation load development and also has thickness to completely dissipate the influence of such foundations in the area. For such foundations which could be placed between 1.0m and 3.0m depth, an average allowable bearing pressure qa of100kN/m² is recommended for the area. The size of projects in the area in terms of loading presupposes that a shallow foundation placed at a minimum of about 900mm below existing ground level may be appropriate. For such foundation and for a maximum consolidation settlement of about 60mm, an allowable bearing pressure of 100kpa is recommended.

TABLE OF CONTENTS

COVER PAGE

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWLEDGEMENT

ABSTRACT

CHAPTER ONE

INTRODUCTION

BACKGROUND OF THE STUDY
AIM OF THE STUDY
SIGNIFICANCE OF THE STUDY
APPLICATION OF THE STUDY
SCOPE OF THE STUDY
PROJECT ORGANIZATION

CHAPTER TWO

LITERATURE REVIEW

OVERVIEW OF FOUNDATION
REQUIREMENTS OF A GOOD FOUNDATION
SOIL MECHANICS
GEOTECHNICAL INVESTIGATION
REVIEW OF STRUCTURES FOUNDATIONS
TYPE OF FOUNDATION
OVERVIEW OF STRIP FOUNDATION

CHAPTER THREE

3.0 MATERIALS AND METHODS

3.1 STUDY AREA

3.2 MATERIALS

3.3 METHOD

CHAPTER FOUR

4.0 RESULTS AND DISCUSSION

CHAPTER FIVE

CONCLUSION
RECOMMENDATION

CHAPTER ONE

1.0 INTRODUCTION

1.1 BACKGROUND OF THE STUDY

It has been observed in recent times, that many property developers in Nigeria ignore drastically the role of geotechnical information in the planning, design, construction, operation as well as safety of civil engineering infrastructures. This neglect results to failure of structures (Annoret al., 1987; Amadiet al., 2012; Youdeowei &Nwankwoala, 2013). Frequent structural failure of civil engineering infrastructures in parts of Port Harcourt Metropolis has become a source of worry to so many persons. It is for this reason that a clear understanding of the occurrence, composition, distribution, geologic history as well as the geotechnical properties of subsurface soils in the area is necessary. Considering the fact that the Eastern Niger Delta is within the coastal zone, geotechnical investigation /considerations are very desirable. The coastal zone which comprises the beach ridges and mangrove swamps is underlain by an alternating sequence of sand and clay with a high frequency of occurrence of clay within 10m below the ground surface. Because of the nearness of these compressible clays to the surface, the influence of imposed loads results to consolidation settlement. The impact of the imposed load is exacerbated by the thickness and consistency of the compressible layer. This, in addition to other intrinsic factors contributes to the failure of civil engineering structures.

The knowledge of the geotechnical characteristics of Onne, Rivers State, Nigeria is very desirable for design and construction of foundation of future civil engineering structures in order to minimize adverse effects and prevention of post construction problems. Some studies have been carried out on geotechnical properties of the sub-soils generally (Nwankwoala &Amadi, 2013; Oke &Amadi, 2008; Okeet al., 2009).For the purpose of generating relevant data inputs for the design and construction of foundations for proposed structures, it is imperative that the site be geo-technically characterized through sub-soil investigation. This paper therefore, aims at establishing significant subsoil types and profile, investigation of the engineering characteristics of all such sub-soils to generate the required data relevant to the foundation design and construction of structures.

1.2 AIM OF THE STUDY

This study aims at establishing the sub-soil types and profile to ascertain the geotechnical characteristics of the underlying soils used for strip foundation.

1.3 SIGNIFICANCE OF THE STUDY

Determining the geotechnical characteristics of any soil is important; it will be helpful for civil engineering for their design and construction of foundation structures in order to minimize adverse effects and prevention of post construction problems.

1.4 APPLICATION OF THE STUDY

This study can be useful to both student of this department for their future construction and also to the civil engineer also for their construction works.

1.5 LIMITATION OF THE STUDY

There are different types of foundation and all of them use sand for their construction, but in this work we focus on determining the geotechnical properties of soil for strip foundation.

1.6 PROJECT ORGANISATION

The work is organized as follows: chapter one discuses the introductory part of the work, chapter two presents the literature review of the study, chapter three describes the methods applied, chapter four discusses the results of the work, chapter five summarizes the research outcomes and the recommendations.

CHAPTER FIVE

5.1 CONCLUSIONS

The superficial light brown sandy clay is suitable in quality to carry strip foundation load from proposed development and also possesses thickness to completely dissipate the influence of such foundations. For such foundations which could be placed between 1.0m and 3.0m depth, an average allowable bearing pressure qa of100kN/m²is recommended for the site. The safe working loads of piles are dependent on factors such as pile diameter, founding depth and method of installation which is usually best determined by a specialist-piling contractor from a pile load test. Ultimate pile capacities for axial loading for 406mmÆ, 500mmÆ and 600mmÆtubular driven steel piles have been estimated for the project. Soil profile and geotechnical data obtained from the site were used for the analysis.

5.2 RECOMMENDATION

It is generally accepted that strip foundation design is not complete without load test. Therefore it is recommended that load test be conducted at the site to ensure the design adopted can be safely carried.