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Dependency of bearing strength of rocks on texture and structure

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Presentation on theme: "Dependency of bearing strength of rocks on texture and structure"— Presentation transcript:

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

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.

IGNEOUS SEDIMENTARY METAMORPHIC Granite Sandstone Gneisses Dolerites Limestone Quartzite Basalt Shales 50-150 Marble

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