Author: Mezie Ethelbert

Reading Time: 5 minutes Preamble: Sedimentation is the second unit operation in the water treatment process. It means that sedimentation comes after the screening. Sedimentation involves the removal of suspended and colloidal materials present in water and wastewater. It is used to separate suspended matter that is heavier than water and cannot float. That is to clarify raw water, effluent, and raw wastewater. Sedimentation or gravitational settling is usually done in a sedimentation tank and used to remove sand, total suspended solids (TSS), and flocs from the supernatant. The principle behind the operation of a sedimentation tank is to reduce the velocity of the…

Reading Time: 4 minutes Introduction: Water is one of the most used resources on earth. Common uses of water including for domestic needs, industrial applications, and recreational and agricultural purposes (irrigation). The bulk or all of the water used for these purposes is fresh water whose availability is depleting. The earth has large bodies of water (71%) when compared to the land space (29%) available for human habitation. It is expected that such a large body of water should support properly the population living on the land. However, this is not the case because the greater part of 71% of water is found in…

Reading Time: 4 minutes Introduction: Scaffolds are temporary framework systems used to support workers and materials in the construction or repair of buildings and other large structures while they work at a height (≥ 1500 mm). It is usually a modular system of metal pipes (usually mild steel and aluminum alloy tubes), although it can be made out of other materials like wood. The purpose of a working scaffold is to provide a safe place of work with safe access suitable for the work being done. A suitable scaffold must be designed to support four (4) times the weight of the workers and materials…

Reading Time: 3 minutes Introduction: Underpinning is a common term in foundation works. Underpinning in foundations becomes necessary when there is foundation failure or cracks that necessitate changing of foundations. It also becomes important when there is a need to increase the load on a building and the foundation needs to be strengthened. Reasons for Underpinning of Foundations Uneven settlement of foundations – due to uneven loading; poor soil condition. Increase in loading – due to increase/addition in floor storey or change of use. Lowering of adjacent ground – usually required when constructing a basement adjacent to existing foundations. Precautions to be taken during…

Reading Time: 2 minutes Introduction: Building/Construction works are usually outdoor works and these are mostly affected by bad weather. In countries located in the Southern and Northern hemispheres of the world, the coldest season of the year, called winter usually occur from December to February in the Northern hemisphere and from June to August in the Southern hemisphere. This weather is considered bad weather that affect construction activities. In countries located around the tropics, such as Nigeria, bad weather for construction activities is usually characterized by periods of heavy rainfall. Generally, typical characteristics of bad weather include: prolonged rain, frost, high winds, fog, snow…

Reading Time: 3 minutes Introduction: The application of geosynthetics in civil engineering construction dates back to the 1970s. These are fabric-like materials made from polymers such as polyester, polyethylene, polypropylene, polyvinyl chloride (PVC), nylon, chlorinated polyethylene, etc. Their increasing use in civil engineering construction relates to concern for waste management and sustainability together with their amenability to recycling. Geosynthetics is a broad term that incorporates geotextiles, geofoam, geopipes, geosynthetic clay liners, geomembranes, geonets, geogrids, and geocomposites that are made from synthetic materials (polymers or hydrocarbon chains). The function of geosynthetics can be summarized into five namely: separation, reinforcement, filtration, drainage, and moisture barrier. Major…

Reading Time: 5 minutes Introduction: Prior to the design of underground water retaining structures such as tanks and swimming pools, preliminary sizing of the structural members must be done. However, these sizes must be verified to ensure that they satisfy some adverse effects which the structure would be exposed to in its service life. This verification involves the stabilizing actions that tend to keep the structure stable such as the weight of the structural components of the structure together with the weight of stored water and destabilizing actions that tends to unsettle the structure such as uplift forces from underground water etc. Generally,  verification…

Reading Time: 2 minutes It is necessary to determine whether a structure is unstable, statically determinate, or redundant. For pin-joined structures, the unknown quantities are the axial force in the members and the reactions at the supports. Thus, if there are m-members and r-reactions, the total number of unknowns will be m + r. Similarly, it is possible to resolve the forces in two directions at every joint in the system. Thus, for j-joints, a total of 2j equations can be formed relating to the unknowns. Where, m = number of members; r = number of reactions and j = number of joints If…