Question

1. Classify the igneous rocks according to their depths and evaluate them in terms of their usability as foundation, tunnel and material (such as aggregate, anchoring, building block).

Answer 1

Answer :-

Igneous Rock:-

Igneous rocks are those that solidify from magma, a molten mixture of rock-forming minerals and usually volatiles such as gases and steam. Since their constituent minerals are crystallized from molten material, igneous rocks are formed at high temperatures. They originate from processes deep within the Earth—typically at depths of about 50 to 200 kilometres (30 to 120 miles)—in the mid- to lower-crust or in the upper mantle. Igneous rocks are subdivided into two categories: intrusive (emplaced in the crust), and extrusive (extruded onto the surface of the land or ocean bottom), in which case the cooling molten material is called lava.

Generally base rock, especially of igneous origin, is the strongest foundation material.

Igneous Rock is a solid cumulative of minerals located in the earth's lithosphere. They have been used by mankind through history as a basic construction material. There are huge variation within each type of rocks depending on their engineering properties rocks have been used in various construction works.

Generally Rocks are using for making bricks, fire places and kitchen counter of our homes, dams, buildings, rail way ballast, pavement material, road metal, concrete aggregates etc.

* Rocks are extremely important in terms of their stability and strength as a geological material on which construction foundation are made.

Rock foundations are always prefered because rocks offer a number of advantages compare with soil in terms of stability and durability. Even the weakest rock is better in strength and reliability compared to good soils.Rocks such as limestone, granite, sandstone, shale and hard solid chalk have a high bearing capacity which are extensively used for foundation.

Igneous Rocks in Concrete aggregate

Concrete is made by mixing fine aggregate, coarse aggregate, cement and water. The raw material for making cement is also obtained by rocks.

Aggregates are used in concrete for very specific purposes. The use of coarse and fine aggregates in concrete provides significant economic benefits for the final cost of concrete in place. Aggregates typically make up about 60 to 75 percent of the volume of a concrete mixture, and as they are the least expensive of the materials used in concrete, the economic impact is measurable.

Tunnel engineering generally classify rocks on the basis of resistance to deformation (strength), amount of weathering, and general resistance to weathering.A igneous rock may be very resistant to weathering, but may have also have been subjected to a very long period of time, which may result in significant weathering. In general, the strength and resistance to weathering of a rock is derived from the class of rock. Igneous and metamorphic rocks, in general, are more resistant to deformation and weathering than sedimentary rocks.

Conclusion:-

- In all around the world , stones and rocks were the first building blocks use to make structures and even today they are the most important source for building materials after wood. In order to carry out civil engineering projects safely and successfully, such as constructing road, bridges, tunnels, tanks, reservoirs and buildings, selection of site is important from the view point of stability of forndation and rock forming region, their physical nature, permeability, faults, joints etc. Careful studies bring out the inherent advantage or disadvantage of a site and such studies go a long way either in reducing or in the cost of a structure.