Soil Mechanics and Foundation Engineering (General Engineering) (SSC JE)

The soil suspension passing 75 µ IS sieve is subjected to the sedimentation analysis.
• The material passing 4.75 mm IS sieve but retained on 75 µ IS sieve is subjected to fine sieve analysis.

Sheep foot roller is mostly used for the compaction of earthen embankment of clayey soil. Various types of equipment is used for soil compaction–

Fineness modulus of sand–
1. Fine sand → 2.2 - 2.6 2.
Medium sand → 2.6 - 2.9 3.
Coarse sand → 2.9 - 3.2
As the fineness modulus increases the size of particle increases and the find aggregate having F.M. more than 3.2 is not suitable for concrete work.
Note–FM of coarse aggregate (6–8.5)

Aeolian soil–The soil which is made of sand particles deposited by wind at a certain place is called as aeolian soil.

Colluvial soil–It is formed due to deposit of soil in low areas due to land-slides.

Glacial soil–Soils are formed due to deposits of particles through glaciers , those soils are called as glacial soils.

Indian Standard soil classification system :
• Soil classification based upon grain size (m)
(i) Fine gradient soil
• Silt → (0.075-0.002) mm
• Clay → (< 0.002) mm
(ii) Coarse gradient soil
• Sand → (0.075-4.75) mm
• Gravel → (4.75-80) mm
(iii) Cobbler → (80-300) mm
(iv) Boulder → (> 300) mm

Unified Soil Classification System–
Originally developed by casagrande (1940), the unified soil classification system was used for air field construction during World War II.
Various soils are classified into four groups–(i) Coarse grained, (ii) Fine grained, (iii) Organic soils and (iv) Peat. There are in all 15 groups of soils - 8 groups of coarse grained soils, 6 groups of fine grained soils (including organic soils) and 1 group for peat.

• The coarse grained soils are further subdivided into eight basic soil groups. The fine-grained soils are further subdivided into nine basic soil groups. Highly organic soils and other miscellaneous soil materials are placed in one group.
• Thus in the ISC (Indian Standard Classification) system soils are classified into 18 groups.

Bearing capacity–The maximum load which the soil can take per unit area without yielding or displacement is called its bearing capacity.