Author: Mezie Ethelbert

Reading Time: 6 minutes Principle In the unconfined compression test a cylindrical specimen of cohesive soil is subjected to a steadily increasing axial compression until failure occurs. The axial force is the only force applied to the specimen. The test is normally carried out on cylindrical specimens of a length equal to about twice the diameter. Nominal diameter range from 38 mm to 100 mm. The specimen length should be as close to twice the diameter as the nature of the soil and the end preparation will permit. The length may vary from 8 % under-size to 12 % over-size without significantly affecting the…

Reading Time: 2 minutes The study of the behavior of fine-grained soils is one of the most important to a geotechnical engineer because any soil that contains more than 50% of fine-grained soils (soils passing sieve size 425 μm sieve), the behavior of the soil is controlled by these fines and they abundantly occur in nature. Field classification of fine-grained soils is often required in practice and the common methods to do this would be shown in this post. A natural heap of soil usually contains coarse-grained particles and fine-grained particles and sometimes organic soils. Highly organic soils often classified as peat can be…

Reading Time: 6 minutes Liquid Limit General Wherever possible the test shall be carried out on soil in its natural state. With many clay soils it is practicable and shall be permissible to remove by hand any coarse particles present, i.e. particles retained on a 425 μm test sieve. In the definitive method the soil shall not be allowed to become dry before testing. Where air drying is required the method used shall be stated. Procedure Step 1: Take a sample of about 300 g from the soil paste and place it on the glass plate. Step 2: Mix the prepared paste for at…

Reading Time: 3 minutes General: The procedure for determining the pH value, by the electrometric method, which gives a direct reading of the pH value of a soil suspension in water is described here. This method can also be used for determining the pH value of a sample of ground water. NOTE: Good practice in chemical testing requires that duplicate specimens should be tested. In each of the test methods the measurement of only one value of the overall result is described. It is recognized that it is necessary in many practical applications to make a number of tests in order to obtain a…

Reading Time: 7 minutes General: Water is present in most naturally occurring soils. The amount of water, expressed as a proportion by mass of the dry solid particles, known as the moisture content, has a profound effect on soil behaviour. In this context a soil is “dry” when no further water can be removed at a temperature not exceeding 110 °C. Moisture content is required as a guide to classification of natural soils and as a control criterion in recompacted soils and is measured on samples used for most field and laboratory tests. NOTE: In some situations, for example in the field control of…

Reading Time: 10 minutes Introduction: Design of machine foundations come under the topic of soil dynamics in geotechnical engineering. Dynamic forces in soil could originate from sources such as: EarthquakesBlasts engineered by manPile drivingLanding of aircraft,Action of wind and running waterOperation of heavy machines etc Generally, soil dynamics could be applied in the following fields: Vibration and settlement of structure, and of foundations of machineryDensification of soil by dynamic compaction and vibrationPenetration of piles and sheet piles by vibration or impactDynamic and geophysical methods of explorationEffects of blasting on soils and rock materialsEffects of earthquakes and earthquake-resistant design of foundations Machine Foundations Machines generate…

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Reading Time: 3 minutes There are standard methods to determine the vertical effective stress σoˡ (always calculated from the ground surface to the required depth) and increase in the vertical effective stress, Δσˡ (usually calculated from the lower face of the foundation). These can be found in standard textbooks. For the quick determination of Δσˡ, the method known as 2:1 method would be explained below. This method is based on the assumption that the stress from the foundation spreads out with the vertical-to-horizontal slope of 2:1. 2:1 method explained For rectangular borings, the diagram in Figure below applies; From the Figure above, ΔσDˡ =…