Science of Geology

Geology

Geology is the science which is devoted to the study of earth. It deals with all the features of the earth’s surface and with the origin, composition, structure and inhabitants of the earth.

Science of Geology

Branches of Geology

The subject of geology is very large and it is divided into several branches which are as follows:

1. Physical Geology: It is concerned with the work of natural processes which bring about changes upon the earth’s surface.
2. Mineralogy : It includes the study of minerals.
3. Structural Geology : It includes the study of stratified rocks in the earth’s crust.
4. Petrology: The discussion of different types of rocks is known as petrology.
5. Stratigraphy : It is concerned with the study of stratified rocks and their correlation .
6. Palaeontology : It deals with the study of fossils.
7. Historical Geology : The study of stratigraphy and palaeontology is included under historical geology. It gives us a picture of the land and seas, the climate, and the life of early times upon the earth.
8. Economic Geology : It deals with the study of minerals of economic importance.
9. Mining Geology : It is concerned with the study of application of geology to mining engineering.
10. Engineering Geology : It includes the study of application of geology to Civil Engineering.

Liquefaction of Soil

Definition                       

                           Liquefaction refers to a phenomenon where saturated, loose, cohesionless soils lose strength due to earthquake ground motion or other sudden change in stress condition, in which material that is ordinarily a solid behaves like a liquid.

When soil becomes saturated with water, it enters a state known as liquefaction where it stops acting like a solid and starts behaving like a liquid.

Factors Affecting the Liquefaction of Soil

 Fundamental factors that influence liquefaction susceptibility of saturated sands are considered, from the background of comprehensive experimental evidence from test results on reconstituted specimens. It is shown that at identical initial void ratio-effective stress state, undrained (constant volume) behaviour is profoundly affected by the fabric that ensues upon sample reconstitution. Water pluviation simulates in-situ behaviour closely. Very loose moist tamped states are unlikely to be accessible to in-situ sands. The susceptibility to liquefaction, both static and cyclic, depends not only on the initial state variables, but is also strongly affected by the effective stress path during undrained shear. On post cyclic static loading, the virgin strain softening sand is strain softening no more, but deforms with a continually increasing stiffness if the cyclic loading terminates with a residual zero effective stress. Very small expansive volumetric strains due to pore pressure gradients during short duration loading, or after its cessation could transform a sand into a strain softening type, which otherwise would be dilative if completely undrained.

How to Avoid Liquefaction?

                           If a structure is new construction, you should check liquefaction susceptibility before you build. However, if a structure already exists, there are measures you can take to reduce the damage caused by earthquake-related liquefaction. Structures can be retrofitted and reinforced to reduce the impact of violent shaking, and the soil under and around them can also be densified, solidified, reinforced, drained and/or dewatered.

                            All buildings in earthquake-prone areas can be strengthened through bracing, reinforcing masonry, sheer plating (such as adding plates of plywood to stud walls), and bolting walls to foundations. In the interior, it’s always a good idea to strap water heaters to the wall and secure heavy objects like bookshelves and mirrors to prevent them from falling when the building shakes.

Liquefaction of Soil  Tank