Geotechnical engineering

The first step to start any construction is the geotechnical investigation studies , these studies include type of soil , types of rock in the site and the it's topography .

Soil : 

There are many things that we have to know about the soil :
1- type of soil
2- physical properties
3- friction coeffecient angle
4- shear stresses
5- normal stresses
6- thermal resistivity

Any factor of these will affect on the excavation and foundation , for an example , for the weak soil may be we should use raft foundation or piles but for strong soil may be we use single footing . It doesn't affect just the type it's affect the thickness and other dimensions .

Rocks : 

The rocks are divided in three types :
1- Igneous rocks
2- sedimentary rocks
3- metamorphic rocks

Each one of these types differ from the others by physical properties , chemical properties , uses , textures and the procedure that resulted from .

Igneous rocks :

The igneous rocks is the result of magma or lava cools or hardens .

*magma is inside earth's interior 

*lava is outside earth crust

Igneous rocks are classified depending on : 

Texture size : texture mean how a rock looks and feels , and its based on the grain size .

Where the rock is made : rocks that cool slowly have larger crystals , but rocks that cools fast have smaller crystals .

Materials that the rock made from : the major silicate rock forming elements are : O , Si , Al , Fe , Mg ,K , Na , Ca . 

*When the silica percentage decrease the rock will become darker .

*Glassy texture means that the rock have no crystal grains .

In the next post we will talk about other types of rocks : sedimentary and metamorphic rocks .