Geotechnical Materials - Essay Example

Geotechnical Material What is a rock The Earth we live on is composed of a huge mass of rock; from the tallest mountain ranges to the beds of the seven oceans rocks have set the base on this earth. Various types of rocks and minerals have been found on Earth. Most of the rocks on the Earth's are produced from merely eight elements the oxygen, silicon, aluminum, iron, magnesium, calcium, potassium, and sodium, but these elements are pooled in a number of ways to make rocks that are extremely distinct. Rocks and soil texture is frequently changing. Wind and water erode them along and transmit specks of rock away; the minute particles gather in a lake or ocean and solidify into rock again. The oldest rock that has ever been found on the earth surface is more than 3.9 billion years old. While the universe itself is aged at least 4.5 billion years, but rocks from the start of Earth's history have altered so much from their actual shape that they have become new classes of rock. By evaluating how rocks form and modify, scientists have developed a strong perception of the Earth we commute on and its roots. Different types of Rocks Archaeologists categorize rocks in three factions, with regards to the chief Earth procedures that shaped them. The three rock categories are igneous, sedimentary, and metamorphic rocks. Igneous Rocks Igneous rocks are formed from liquefied rock that has subjected to lower temperature and hardened. Deep within the earth the affect of high temperatures and pressure melts the rocks that exist deep within the surface. The molten rock also called the magma can the flow upward in the form of a volcano and be erupted on to the earth's facade. When this molten rock cools, the process is slow and usually occurs at areas thousands of feet deep, crystals are formed from the melted liquid, and a coarse-grained rock result. When the magma cools quickly, typically near or at the Earth's surface, the crystals are really minute, and a fine-grained rock forms. An extensive variety of rocks are created by diverse cooling rates and distinct chemical compositions of the original molten rock. Obsidian i.e. volcanic glass, granite and andesite porphyry are three of the many kinds of igneous rocks. Sedimentary Rocks These rocks are formed at the facade of the Earth, either in water or on land surface. They are lined clusters of sediments-fragments of rocks, minerals, or animal or plant matter. Temperatures and pressures conditions are moderate or even low at the Earth's surface, and sedimentary rocks reflect this reality by their form and the minerals they constitute. Most sedimentary rocks become paved together by minerals and chemicals or are held jointly by electrical attraction; but, some still remain loose and insecure. The films are typically parallel or almost parallel to the surface of the earth. If they are at large angles to the earth's surface or are tangled or conked out, a certain kind of Earth movement has taken place since the rock was fashioned. Sedimentary rocks are being produced around us all the time. Compressed and dehydrated mud flats solidify into shale. Metamorphous Rocks Sedimentary and igneous rocks are occasionally exposed to extreme pressures conditions or are heated so intesely that they are completely changed into an entirely new class of rock family. They are changed to metamorphic rocks, which are formed deep within the Earth's crust. Rocks do not melt duing the process of metaorphism, but instead are transformed into denser, more consolidated rocks.Distinct kinds of minerals are produced either by restructuring of mineral components or by mixing and reacting with fluids that enter the rocks. Some kinds of metamorphic rocks are strongly joined or foliated i.e. their minerals are arranged in such a parralel way that their rocks have a striped appearance. Effects of Pressure and temperature can even modify the propoerties of previously metamorphised rocks and convert them into new types Classification and Structure Rocks Rocks are classified in various manners by compositions of mineral and chemical, by the texture of the component particles and by the methods that they were created. These features differentiate rocks into igneous, sedimentary and metamorphic types. They may also be further categorized according to their particle size. The conversion from one rock type to another is explained by the geologist as the all important rock cycle. Igneous Rocks Igneous rocks are formed from magma and are divided into two broad types Intrusive and extrusive, these are further classified on the basis of texture and composition into a number of other categories. Intrusive igneous rocks are formed by magma that cools and hardens within the earth these rocks that are formed are coarse grained. The mineral grains in such rocks can generally be identified with the naked eye. Intrusive rocks can also be categorized according to the shape and size of the invasive body and its relation with the other structures into which it encroaches. Intrusive igneous rocks that are formed at a depth in the earth surface are termed as abyssal and those that are formed nearer to the surface are termed as hyperabyssal. These rocks are light colored and their lines display the movement of lava flow. Extrusive rocks are formed at the earth's surface due to the partial melting of rocks within the crust and mantle. The magma erupts and reached the surface of the earth where it is cooled and turned into a rock. As lava cools and crystallizes quickly, it has fine particles. When the cooling is quick such that the minute crystals cannot be formed via extrusion, the resulting that is formed is in the form of the glass, one of the most famous examples of such rock is odsidian. On the other hand if the cooling of the lava occured slowly, the rocks that are formed would be coarse-grained. Moreover the igneous rocks are classified on the basis of their texture namely Porphyritic, Glassy and Vesicular texture. When magma cools slowly at first but then rock cools more rapidly as it nears the earth's surface. Large crystals are produced that are embedded within a mass of smaller ones. For example Granite. Viscous magma cools quickly and crystals are unable to form such rocks are of glassy texture for example Obsidian. Gaseous magma cools quickly this makes bubbles and the rock that forms is full of holes called vesicles an example this form of an igneous rock is pumice. Sedimentary Rocks These kinds of rocks are found on earth and water and are formed by either weathering in situ or by erosion of water and land. Popular rocks like chalk, sandstone and limestone belong to this category of rocks and are classified into three main categories Clastic, Biochemical and chemical precipitate. Clastic sedimentary rocks are formed from rocks that have broken down into fragments by erosion of wind or water and have been deposited elsewhere. Such rocks are found in both coarse and fine grains and have great commercial value. Biochemical sedimentary rocks have constituents that are composed of living organisms of animal and plants these are formed at the ocean floor. Chemical Precipitate sedimentary rocks form when mineral solutions, such as sea water, evaporate into the atmosphere. These are angular in shape and are composed of layers and cracks which have been created due affect of mud and ripples. Sedimentary rocks are layered but are extremely strong and stable. Metamorphic Rocks These rocks are formed by the effects of atmosphere on the sedimentary and igneous rocks. These are classified by the chemical and texture into two broad categories foliated and non-foliated. Foliated rocks are formed when they are subjected to a strong compressive force is applied in one direction. It is formed by the application of differential stress that deforms the rocks into one plane. These arranged compressions give foliated rocks a [planar or band shape .Non-foliated rocks are not subjected to planar pressure and hence their mineral grains are not arranged in planed or bands. Metamorphic rocks are easy to cut and polish and are thus utilized in building of houses. Such rocks are less stable. Excavation Techniques Geotechnical excavation involves the removal of soil, sediment, or rock that is found on artifacts or other proof of human actions. Primary stages of excavation consist of techniques which were destructive in nature and consisted of random digging and removal of matter with no location data recorded. Modern techniques often involve low paced, meticulous extraction of sediments in very thin stratas, detailed sifting of sediment samples. Full face drilling, NATM, Spiling/ forepoling and Ground freezing are some of the techniques that are utilized in excavating soil and rocks from the earth during research excavation. Full face drilling It involves the conventional drill and blast method along with the conventional drill blast method it involved digging the entire rock in one day. The high pressure of head against the face of the tunnel leads to the crushing of the rock at the face it is much quicker method and involves handling of weakness point with much more flexibility. NATM It is based on ancient design and construction techniques but incorporates modern observational methods and makes use of technology. It involves mobilizing the maximum strength of mass by deliberately allowing some deformation in the rock in order to reduce the necessary input pressure. Spiling/ Forepoling The above stated technique is used in adverse rock mass conditions where the stand up time is low. It consists of a three step process involving a drill in series of holes in a semicircular pattern installing steel pipes or rock bolts into holes. The following step involves excavating the rock in short incremental steps. These steps are further repeated until excavation is complete. Ground Freezing Ground freezing is used under poor rock conditions. State of art technology is used to make the construction of tunnel possible. It is a four step process: Drilling of holes for freezing materials Careful excavation Rocks support When the permanent rock support is established excavation is carried out. Importance and Uses of Rocks Rocks have an enormous impact on the cultural and technological progress of the human civilization. Lithic technology identifies some of the ancient and frequently used technologies. The extraction of rocks for their metal ore substance has been one of the most significant factors of human development. Human civilization's development has been determined by the variety of metals available from the rocks of an area. The prehistory of culture is characterized into the Stone Age, Iron Age, and Bronze Age. Rocks have been and persist to be used to construct buildings and transportation. Igneous rocks are significant as their minerals and world chemistry give information about the constitution of the mantle, from where several igneous rocks have been dug out, and the temperature and pressure conditions that permitted this excavation. Several Various items of everyday use are made up of these rocksincluding cars, tooth brush, video tapes, roads etc. Igneous rocks are especially used in making buildings, monuments, tombstones, arrowheads and knives in scouring, scrubbing, and polishing materials. Sedimentary rocks are commercially significant in that they can easily be utilized as building material because they are soft and can be easily cut. For example, the White House in Washington DC is made of sandstone which is one of the premier examples of sedimentary rocks. Limestone is one another important mineral which is an example of sedimentary and is best utilized in making skyscrapers. Metamorphic rocks are used in tiling of house floors and bathrooms. Marble one of the important metamorphic rocks Marble is extensively utilized in making floors and sculpting statues. Many great monuments of the world specially Taj Mahal, one of the wonders of the world was entirely carved out of marble. Architechture and sculptry involve an enormous use of metamorphic rocks. Rocks continue to offer great commercial value and with this view in sight the excavation of rocks and minerals has continously been intesified Bibliography 1. Barker, R M (1997). Collecting rocks. Retrieved July 20, 2007, from USGS Web site:http://pubs.usgs.gov/gip/collect1/collectgip.html Read More