In-situ Tests on Soil In situ testing is a division of field testing corresponding to the cases where the ground is tested in-place by instruments that are inserted in or penetrate the ground. In-situ tests are normally associated with tests for which a borehole either is unnecessary or is only an incidental part of the … Read more
How to Classify Soil Visually on site? Purpose: Visually classify the soils. Standard Reference: ASTM D 2488 – Standard Practice for Description and Identification of Soils (Visual – Manual Procedure) Significance: The first step in any geotechnical engineering project is to identify and describe the subsoil condition. For example, as soon as a ground is … Read more
Standard Penetration Test (SPT) Procedure Aim To perform standard penetration to obtain the penetration resistance (N-value) along the depth at a given site. Equipment & Apparatus Tripod (to give a clear height of about 4 m; one of the legs of the tripod should have ladder to facilitate a person to reach tripod head.) Tripod … Read more
Depth and Spacing of Trial Pits & Borings The depth and spacing of trial pits or exploratory borings should be such as to give a true picture of the underlying soil, with regard to any major changes in thickness, depth or properties of the strata over the base area of the structure and in its … Read more
Values of Safe Bearing Capacity The safe bearing capacity of soil should be determined on the basis of soil test data or by performing some field test such as Standard penetration test or Plate load test etc. However, in the absence of soil test data, the values of safe bearing capacity (S.B.C) as given in … Read more
Laboratory Vane Shear Test of Soil Aim To determine shear strength of clay soil using laboratory vane shear apparatus. Theory In soil, shear strength is contributed by the two properties. Cohesion, and Angle of internal friction In pure clays the shear resistance due to internal friction is negligible. Hence, the complete shear strength in clays … Read more
Boring Methods of Exploration The boring methods are used for exploration at greater depths where direct methods fail. These provide both disturbed as well as undisturbed samples depending upon the method of boring. In selecting the boring method for a particular job, consideration should be made for the following: The materials to be encountered … Read more
On-Site Identification & Classification of Soil The principle terms used by civil engineers to describe soils are Gravel (particle size larger than 4.75 mm) Sand (particle size within 4.75 mm to 0.075mm) Silt & Clay (particle size less than 0.075mm) Most natural soils consist of a mixture of two or more of these constituents and … Read more
Components Contributing Settlement of Soil Total settlement ρ in mm, which is the response of stress applied to the soil, may be calculated as the sum of three components ρ = ρi + ρc + ρs Where, ρ = Total settlement, mm ρi = Immediate or distortion settlement, mm ρc = Primary consolidation settlement, mm … Read more
Electrical Resistivity Test of Soil This method depends on differences in the electrical resistance of different soil (and rock) types. The flow of current through a soil is mainly due to electrolytic action and therefore depends on the concentration of dissolved salts in the pores. The mineral particles of soil are poor conductors of current. … Read more