Author: Mezie Ethelbert

Reading Time: 9 minutes 1. A sample of dry sand was subjected to a triaxial test, with a confining pressure of 250 kN/m2. The angle of shearing resistance was found to be 36oC. At what value of the major principal stress is the sample likely to fail? Solution Given Minor principal stress, σ3 = 250kN/m2, Angle of shearing resistance, ϕ = 36o To find, Major principal stress, σ1 =? Use, σ1 = σ3 tan2 (45 + ϕ/2) + 2c tan (45 + ϕ/2) Note: the soil sample is a dry sand, hence, cohesion, c = 0 Angle of inclination of the failure plane, θ…

Reading Time: 5 minutes A hydraulic structure is submerged or partially submerged in any body of water, which disrupts the natural flow of water. They can be used to divert, disrupt, or completely stop the flow. It also includes structures used for the storage of water such as tanks or large means of provision or conveyance of water. A common example of such is the dam. Table 1 shows common hydraulic structures and their estimated life span. S/No Types of Hydraulic Structures Estimated life span (years) 1 Earth dams, gravity dams 150 2 Loose rock dams 60 3 Steel dams 40 4 Timber dams…

Reading Time: 9 minutes Hot mix asphalt is composed of asphalt and aggregates, heated and blended into a uniform mixture in precise proportions. When a sample of paving mixture is prepared in the laboratory, it can be analysed to determine its probable performance in a pavement structure. The analysis focuses on four (4) characteristics of the mixture and the influence of those characteristics are likely to have on the mix behaviour. The 4 characteristics are: Four Characteristics of Hot Mix Asphalt Mix Density Air Voids Voids in Mineral Aggregate (VMA) and Asphalt Content Density: Density of the compacted mix is its unit weight (the…

Reading Time: 5 minutes Soil classification is the arrangement of soils into different groups in a way that the soils in a particular group have similar behaviour. It is often described as the language of the geotechnical engineer in that an engineer anywhere in the world can understand the behaviour of any soil any other place based on the class the soil belongs to, for example, if a soil is classified as SW based on Unified Soil Classification System (USCS), a geotechnical engineer anywhere in the world would understand that the soil is well graded sand that has low compressibility and high shear strength.…

Reading Time: 2 minutes The knowledge of shrinkage characteristics of concrete is necessary in the design of structures for crack control. When concrete is exposed to its service environment, it tends to reach an equilibrium with the environment. If the environment is dry, the exposed surface of the concrete loses water by evaporation. The rate of evaporation will depend on the relative humidity, temperature, water-cement ratio and the area of the exposed surface of the concrete. The first water to be lost is that water held in the large capillary pores of the hardened concrete. The loss of this water does not cause significant…

Reading Time: 5 minutes A roof is a covering over a building that protects the elements and the inhabitants from rainfall, sunshine, ice, snowfall and other adverse effects of weather etc. A roof comprises of two sections: the wood or steel section skeleton and the roof covering itself that consists either of aluminum sheets, galvanized iron sheets, zinc or asbestos sheets. Aluminum sheets is most common in Nigeria today because of many desirable properties such that it does not corrode like steel sheets and does not break like asbestos. Common aluminum roofing sheet brands in Nigeria are the: Long span aluminum, Step-tile aluminum and…

Reading Time: 2 minutes Tests required in materials proposed for soil-cement stabilization include: Liquid limit test (for classification) Plasticity test (for classification) Grading tests (for classification) Density/moisture content compaction test (to determine suitable Maximum Dry Density (MDD) and Optimum Moisture Content (OMC) for the California Bearing Ration (CBR) test) Laboratory CBR test Unconfined Compressive Strength (UCS) test Procedure to determine the cement content (According to Clause 6229 of General Specifications for Roads and Bridges-Volume II-Revised 1997) Classify the soil based on AASHTO classification (using tests a – c above). Perform British Standard (B.S.) compaction on the soil to obtain MDD and OMC using the…

Reading Time: 4 minutes Introduction A soil usually comprises of solid particles, soil water and soil air. When the soil is saturated, it comprises of solid particles and soil water. If the soil is subjected to load, the soil witnesses total stress which comprises of effective stresses (on solid particles) and pore water pressure. if the load is sustained, the pore water pressure dissipates from the pore spaces and all the load is transferred to the solid particles. This is where the Terzaghi’s effective stress principle (formulated in 1936) finds much relevance. The Principle states thus: when stress is applied to a porous material,…