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Ret 565 Characteristic Soil


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Ret 565 Characteristic Soil

  3. 3. SOIL <ul><li>A knowledge of these engineering characteristics aids in the determining the degree to which to a local soil can be used in engineering project to support traffic loads or to serve as a subgrade or foundation material. </li></ul>
  4. 4. Soil characteristics <ul><li>Plasticity of soils </li></ul><ul><li>Shear strength of soils </li></ul><ul><li>Compressive strength of soils </li></ul><ul><li>Compaction of soils </li></ul><ul><li>Grain size distribution soils </li></ul><ul><li>Moisture content of soils </li></ul>
  5. 5. Shear strength of soils <ul><li>The strength of the soils determines its ability to support the loads of a structure or remain stable upon a hillside. </li></ul><ul><li>The strength of a soil is often determined by its ability to withstand shearing stresses </li></ul><ul><li>When load is applied to a soil , the load is supported by an increase in the pore water pressure until pore water can drain into regions of lower pressure. </li></ul>
  6. 6. Angle of internal friction <ul><li>SOIL TYPE ANGLE φ, DEGREES </li></ul><ul><li>Sand and gravel mixture 33 – 36 </li></ul><ul><li>Well-graded sand 32 – 35 </li></ul><ul><li>Fine to medium sand 29 – 32 </li></ul><ul><li>Silty sand 27 – 32 </li></ul><ul><li>Silt (non-plastic) 26 – 30 </li></ul>
  7. 7. Compressive strength of soils <ul><li>The tendency of a soil to decrease in volume under load. </li></ul><ul><li>The change in thickness is measured after the application of each load increment. </li></ul><ul><li>Soil particles are force closer together thus compression of the soil causes a decrease in void ratio. </li></ul><ul><li>Compressive strength of soils is important because it can be used to predict the amount of settlement that will occur from a load of a building or other structures. </li></ul>
  8. 8. Compaction of soils <ul><li>Compactness refer to how closely a mass of soil particles are packed together ; the closer the packing , the greater the compactness and the larger the weight the soil per unit volume. </li></ul><ul><li>The particles are closely packed and have a high degree of compactness. </li></ul><ul><li>A dense structure provides interlocking of particles with smaller grains filling the voids between the larger particles. </li></ul>
  9. 9. <ul><li>The lessen the tendency for displacements for the individual grains under load , and the soil is then capable of supporting heavier loads. </li></ul><ul><li>Well graded coarse material usually are dense and have strength and stability under load. </li></ul><ul><li>Loose , open structure have large voids , which will lead to settlement or disintegration when foundation or traffic loads are applied. </li></ul>
  10. 10. Grain size distribution <ul><li>Physical characteristics can be subdivided into </li></ul><ul><li>- Particles size </li></ul><ul><li>- Particles shape </li></ul><ul><li>- Gradation </li></ul>
  11. 11. Index Properties of Soils <ul><li>Soil type Index Property </li></ul><ul><li>Coarse-grained Particle-size distribution </li></ul><ul><li>(cohesionless) Shape of particle </li></ul><ul><li>Clay content </li></ul><ul><li>In-place density </li></ul><ul><li>Relative density </li></ul><ul><li>Fine-grained Consistency </li></ul><ul><li>(cohesive) Water content </li></ul><ul><li>Atterberg limits </li></ul><ul><li>Type and amount of clay </li></ul><ul><li>Sensitivity </li></ul>
  12. 12. Particles shape <ul><li>Bulky and platy </li></ul><ul><li>The term bulky is confined to particles that are relatively large in all three dimension , as contrasted to platy particles , in which one dimension is small as compared to the other two. </li></ul><ul><li>Can be subdivided into : </li></ul><ul><li>- Angular </li></ul><ul><li>- Subangular </li></ul><ul><li>- Subrounded </li></ul><ul><li>- Rounded </li></ul>
  13. 13. Angular <ul><li>Generally the best for construction because of their interlocking characteristics. </li></ul><ul><li>Angular material must usually be produce artificially , by crushing. </li></ul><ul><li>Subangular </li></ul><ul><li>Particles are those that have been weathered to the extent that the sharper points and ridges have been worn off. </li></ul>
  14. 14. Subrounded <ul><li>Particles are those that have been weathered to further degree than subangular particles. </li></ul><ul><li>If composed to of hard , durable particles , subrounded material is adequate for most construction needs. </li></ul>
  15. 15. Rounded <ul><li>The particles resembles spheres and are of varying size. </li></ul><ul><li>Because of their shape this flaky particles have a greater contact area for moisture and are undesirable for construction purposes. </li></ul>
  16. 16. Gradation <ul><li>Well graded – a soil have a good range of all representative particles size between the largest and the smallest. </li></ul><ul><li>Uniformly graded – poorly graded soil are either those containing a narrow range of particles size or those with some intermediate size lacking. </li></ul><ul><li>Gap graded – soils that have some intermediate size. </li></ul>
  17. 17. Moisture content of soils <ul><li>The moisture content of a soil mass is often the most important factor affecting the engineering characteristic of the soil. </li></ul><ul><li>It influences various soil differently ; it probably has the greatest effect upon the behavior of the soil when the soil is subjected to loading. </li></ul>
  18. 18. THANK YOU