1.1 Introduction
A retaining wall is a structure designed to sustain the earth behind it. It retains a steep faced slope of an earth mass against rupture of slopes faced slopes in cuts and fills and against sliding down. The retained material exerts a push on structures and this tends to overturn and slide it. Besides the self-weight, the main predominant force for analysis and design of the retaining wall is lateral earth pressure. The lateral earth pressure behind the wall depends on the angle of internal friction and the cohesive strength of the retained material, as well as the direction and magnitude of movement of the stems. Retaining walls are encountered and constructed in various fields of engineering such as roads, harbors, dams, subways, railroads, tunnels, mines and military fortifications.
As a prelude to other parts of this study, this chapter will discuss the background upon which this study was initiated, the statement of problems that led to this study, the Aim and Objectives of the study. Others are Significance of the study, Scope of work, Limitations of the Study and Definition of technical terms.
1.2 Background of Study
Retaining walls date back to ancient Egypt, where they were used to harness the great power of the Nile river. Tired of flooding and soil erosion, Egyptians built Gabion style retaining walls from reeds to divert the flow of water from the Nile into reservoirs as well as fields for farming purposes. While modern times have seen innovations in the materials used to build retaining walls, retaining wall applications have largely remained the same: preventing soil erosion, creating space and diverting water (Retainingwallcompanies, 2021).
Retaining walls are structures constructed to support earth or water or other materials such as coal, ore, etc. The retaining material is usually called as backfill. The main objective of retaining walls is to stabilize hillsides and protect it from erosion. At any place if soils are unstable, steep slopes are there, or heavy runoff is present, retaining walls are used to stop erosion. Excessive runoff can wash out roadways and structures, and protecting sediment runoff is a big environmental and water quality consideration in transportation projects like road and bridge projects. In these scenario constructing retaining walls, reduces removal of vegetation and reduction in erosion caused by runoff. Again soil will get stabilized by the vegetation. Sediments and pollutants gets filter out before they enter the water source, in this way improving water quality.
The supported material exerts a force on structures and this leads to overturning and sliding effect on it. Along with the self-weight, earth pressure is the majorly acting force for analysis and design of the retaining wall. Cohesive strength of soil and angle of internal friction are very important factors on which the lateral earth pressure depends. Earth pressures distribution is generally triangular, minimum at top of the wall and increasing towards the bottom of wall. This push force can either overturn or push forward the wall if not properly analyzed.
The most important consideration in proper design and installation of retaining wall is recognize and counteract the tendency of the retained to move down slope due to gravity. This creates lateral earth pressure behind the wall which depends on the angle of internal friction and the cohesive strength of the retained material, as well as the direction and magnitude of movements the retaining structure undergoes. Therefore, in Nigeria where the research was carried out, the activities that was conducted is to know the Analysis and Design of a Retaining Wall.
1.3 Statement of Problems
Investigation revealed that development of land, one often comes across with the challenge of creating a difference in terrain elevation over an arbitrary horizontal distance. This can often be done by creating slopes or by constructing retaining walls. Retaining walls are structures that are constructed to retail soil or any such materials which are unable to stand vertically by themselves. Cost against each optimal design of wall for particular height is calculated by using the volume of concrete and the amount of steel. Amidst the cost estimates of all the three optimal designs for particular height, a comparative study is carried out and the alternative with the least cost estimate is chosen as the best design solution.
1.4 Aim and Objectives of Study
The aim of the study is to analyze the design procedure of a Retaining Wall in Enugu metropolis. In achieving this aim, the following specific objectives were laid out as follows:
- To identify the various methods of designing a Retaining Wall in Enugu metropolis
- To identify eh specific problems associated with the design of Retaining Wall
- To assess the effectiveness or adequacy of the existing system of design of Retaining Wall in Enugu metropolis
1.5 Significance of Study
The study is significant to the extent that the findings will be used in providing stability for earth or materials where conditions disallow the materials from summing its nature al slope or stability. There are many factors affecting or militating against the stability of retaining walls. These include the level of water table behind the wall, size of the base of the wall and nature of the soil retained.
This study will be of immense benefit to other researchers who intend to know more on this study and can also be used by non-researchers to build more on their research work. This study contributes to knowledge and could serve as a guide for other study.
1.6 Scope of the Study
The study focuses on the Analysis and Design of a Retaining Wall in Enugu metropolis, Nigeria.
1.7 Limitations of the Study
During the course of this study, many things militated against its completion, some of which are:
- Time Constraint: The time frame given to accomplish this project was very short due to school academic calendar and it was carried out under pressure which made the researcher not to implement some necessary features.
- Research material: availability of research material is a major setback to the scope of the study.
- Frequent power failure: This made the researcher append more money on fuel to ensure sustainable power.
- Financial Constraint: Insufficient fund tends to impede the efficiency of the researcher in sourcing for the relevant materials, literature or information and in the process of data collection (internet, questionnaire and interview).
1.8 Definition of Terms
For purpose of understanding of this study definition of certain terms as are applicable to this study will be advance.
Management: As a process by which responsible persons in an organization (managers or executives at all levels of management) combine resources in achieving a given objectives goals or ends (ANN, 1 OGBo andTim Adibe, 2006).
Strategies: Is a plan for dealing with uncertain future circumstances (Tim Adibe 2006).
Prospective: Hopes and expectation for success according to concise oxford dictionary, prospects in relation to this are the hopes and expectations that refuse management will become successful or unsuccessful given the existing efforts and attempts to solve the problems (Oluwande 1983).
Problems: This refers to doubtful or difficult matter requiring a solution. Something hard to understand or accomplish or difficult to deal with (cornice oxford dictionary).
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