Part 2 Dredging Process. 1Chapter 1 Basic Concepts of Soil Mechanics. 11.1 Soil Classification. 11.2 Soil Properties. 11.2.1 Phase Relationships of Soil.21.2.2 Compaction and/or Consistency. 21.2.3 Permeability. 21.3 Elementary Soil Tests. 71.3.1 Permeability Test. 71.3.2 Mohr Circle. 81.3.3 Case Study. 101.3.4 Triaxial Shear Test-Mohr Failure Envelop. 121.3.5 Direct Shear Test-Coulombs Law (1776). 131.3.6 Standard Penetration Test-SPT. 161.4 Passive and Active FailureRankines Theory of Lateral Earth Pressure. 171.4.1 Active Stress State. 181.4.2 Passive Stress State. 201.5 Stresses in the Subsoil. 201.5.1 General. 201.5.2 Determination of Vertical Stresses. 221.5.3 Overstressed or Understressed Pore Water in a Clay Layer. 241.6 Consolidation. 25Acknowledgements. 25Part 2 Dredging ProcessChapter 1 Basic Concepts of Soil Mechanics1.1 Soil ClassificationThe object of soil classification is to divide the soil into groups so that all the soils in a particular group have similar characteristics by which they may be identified. In practice, there are many different classifications are used by different institutions, most of these classification systems are based on the outcome of the particle size distribution analyses and the results of the plots on the plasticity chart of Casagrande. Table 1-1 is the internationally most accepted standardization of particle-size-ranges. Table 1-1 Internationally most accepted standardization of particle-size-ranges.fine-grainedcoarse-grainedClaySiltsandgravelstoneColloidsfine26medium620Coarse2060fine60200medium200600coarse6002mmfine26medium620coarse2060cobbles60200boulders200m (micron)mmTable 1-2 shows the British Soil Classification System for Engineering purpose (BS 5930, 1981). The name and descriptive letters used in this system are explained in table 1-3.1.2 Soil Properties1.2.1 Phase Relationships of SoilSoil is a multiphase system, containing three distinct phases: solid, liquid (water) and gas (air). In reality the pores in between the solid particles are filled with water and/or gas, figure 1-1(a); however, in order to define the phase relationships, an element of soil is schematized in figure 1-1(b).1.2.2 Compaction and/or ConsistencyFor natural deposits of soils the compaction of the encountered layer in-situ is an important feature. The compaction of an in-situ sand layer depends on largely on the particle size distribution (figure 1-2), the mode of sedimentation