1. Dependency of bearing strength of rocks on texture and structure
ENGINEERING GEOLOGY
Dependency of bearing strength of rocks on texture and structure
Praveen Ranjan (2014UGCE051)
Prince Kumar Maurya(2014UGCE052)
Shubham Raja(2014UGCE070)
Guided By
Dr. Ranjit Prasad

2. Introduction Of Rocks
Rocks have been defined as “natural solid massive
aggregates of minerals forming the crust of Earth.”
Due to their high compressive strength and load resistant properties they are used as building materials in various fields of interest.
Their compressive strength depends on a number of factors such as its mode of formation, its composition, texture and structure, its moisture content and extent of weathering.

3. Texture of Igneous Rocks
Defined as the mutual relationship of different mineralogical constituents in an igneous rock.
Determined by the size, shape and arrangement of interlocking crystals.
Five common textures in igneous rocks include:
Coarse Grain(Phaneritic)
Fine Grain(Aphanitic)
Porphyritic
Glassy
Vesicular

4. Structure Of Igneous Rocks
Features developed on a large scale in the body of an intrusion or extrusion of igneous rocks.
TYPES:
The Flow structures
The Pillow structures
The Rocky and Blocky lava
The Spherulitic structure
The Orbicular structure
FLOW STRUCTURES
SPHERULITIC STRUCTURES
PILLOW STRUCTURES

5. Texture Of Sedimentary Rocks
Sedimentary rocks show considerable variation in their texture which depend on a no. of factors:
Origin of grains-Clastic or non clastic texture
Size of grains-
Coarse grained->5 mm
Medium grained-5 mm-1 mm
Fine grained-< 1 mm
Shapes of grains-Breccias and conglomerates
Packing of grains-Open packed or porous
Fabric of grains
Crystallization trend-Crystalline granular texture or amorphous

6. Structure of Sedimentary rocks
The large scale features developed in the rock masses during the process of their formation.
TYPES-
Stratification-Layered arrangement
Lamination-Layers thinner than 1 c.m.
Cross Bedding-Layers are not parallel
Graded bedding-Bedding on grain size

7. Texture Of Metamorphic Rocks
Chiefly there are two types of textures of metamorphic rocks-
Crystalloblastic texture-It includes textures that have been newly imposed on the rock during metamorphism.
Eg-Porphyroblastic and Granoblastic.
Palimpset(Relict textures)-It includes textures which
were present in the parent rock despite metamorphic
changes.
Eg-Blastoporphyritic.

8. Structure Of Metamorphic Rocks
Some common structures found in metamorphic structures are:
Cataclastic structure- Mylonite and Slate
Schistoe structure- Mica Schists
Gneissose structure- Banded gneiss
Maculose structure- Hornfels
Granulose structure- Granulites

9. DEPENDENCY OF BEARING STRENGTH ON TEXTURE AND STRUCTURE
Bearing capacity of rock means the strength of rock to bear the stress of load put over it. In the regions where dams and bridges are to be constructed bearing capacity of rock totally depends on texture of
rock because pillars put load on rocks and they may crush them and
bridges, dams may collapse.
Igneous rocks being compact and interlocking in texture and uniform in structure have very high compressive strength compared to sedimentary and metamorphic rocks.
In sedimentary and metamorphic rocks abundance of planes of weakness such as bedding planes, foliation, schistosity and cleavage greatly affect the strength of rock.

10. UNIAXIAL COMPRESSIVE STRENGTH RANGE OF SOME ROCKS(kg/cm^2)
IGNEOUS
SEDIMENTARY
METAMORPHIC
Granite
Sandstone
Gneisses
Dolerites
Limestone
Quartzite
Basalt
Shales
50-150
Marble