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 GEOLOGYDependency of bearing strength of rocks on texture and structurePraveen Ranjan (2014UGCE051)Prince Kumar Maurya(2014UGCE052)Shubham Raja(2014UGCE070)Guided ByDr. Ranjit Prasad
2 Introduction Of RocksRocks have been defined as “natural solid massiveaggregates 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)PorphyriticGlassyVesicular
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 structuresThe Pillow structuresThe Rocky and Blocky lavaThe Spherulitic structureThe Orbicular structureFLOW STRUCTURESSPHERULITIC STRUCTURESPILLOW 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 textureSize of grains-Coarse grained->5 mmMedium grained-5 mm-1 mmFine grained-< 1 mmShapes of grains-Breccias and conglomeratesPacking of grains-Open packed or porousFabric of grainsCrystallization 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 arrangementLamination-Layers thinner than 1 c.m.Cross Bedding-Layers are not parallelGraded 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 whichwere present in the parent rock despite metamorphicchanges.Eg-Blastoporphyritic.
8 Structure Of Metamorphic Rocks Some common structures found in metamorphic structures are:Cataclastic structure- Mylonite and SlateSchistoe structure- Mica SchistsGneissose structure- Banded gneissMaculose structure- HornfelsGranulose 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 ofrock because pillars put load on rocks and they may crush them andbridges, 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) IGNEOUSSEDIMENTARYMETAMORPHICGraniteSandstoneGneissesDoleritesLimestoneQuartziteBasaltShales50-150Marble