OBJECTIVES AND METHODOLOGY

2.1 OBJECTIVES

To gain the exact knowledge of our study, the study with in the class is insufficient for any subject. Therefore field study is must for any subject. The study of geology with in the class is incomplete education. Therefore field study for geology is most necessary things.

The main objectives of our field visit are as follows.

·         To measure strike of bedding plane

·         To measure the dip direction and dip amount of the bedding planes and joints

·         To identify the rock type and its property.

·         To understand the River morphology

·         To estimate, where the bridge site should be selected?

·         To be clear enough about joints, faults and folds.

·         To Study the mass movement

·         To realize the need of geological knowledge in the field of civil engineering.

2.2 METHODOLOGY

Following are the methodology that was implemented.

2.2.1 Desk study: The geological map of the region given to us was thoroughly studied so that we could get an idea of the important rock types and other significant geological characters of the ambience. The guidance of teachers was carefully listened so that we could do better in the field. Important papers and documents were studied properly so that it would help in the field. So in overall we studied the theoretical portions first.

2.2.2 Field Study: It is the most important method of all. Here we studied each and every detail in the field that was necessary. Different places suitable for the geological study were selected and their location was determined by the map and the observation related to such structures were taken and copied such as physical appearances, orientation, geological structures. We followed teachers’ instructions and worked accordingly. All details were noted in the diary. The different rock types at various locations and their properties were noted down. The specimens were numbered and the location of the outcrop was marked in the map. Samples of each type of rocks were also collected. All the available information such as the changes in rock type or the structural characteristics of the outcrop seen was also recorded with the help of photographs and sketches along with text description. Various morphological structures of rivers were also studied there.

INSTRUMENTS USED

§  Hammer

A geological hammer was used to test the hardness of rock in the field. It was performed by striking  the tip of hammer and the surface of the rock whose hardness was to be determined. Hammer was used extraction of the sample.

§  Brunton Compass

A Brunton Compass was used for the determination of attitude parameters. A compass works on the simple principle that a freely suspended magnet aligns itself along the magnetic meridian, when it comes to rest, thus pointing in the north-south relation. The dip direction and dip amount of the rock beds are possible to measure by the use of Brunton Compass. While measuring dip, not only angle but direction of dip also should be noted. The sides of the body of Brunton Compass are placed parallel to the rock bedding for which the attitude is to be determined. To measure the dip direction, the north of the Brunton Compass was placed in the same direction of the dip and the bearing pointed by the compass needle was noted, which gives the dip direction of the rock beds. 

§  Clinometers

The clinometer is an optical device and we used it for measuring elevation angles above horizontal. The most common instruments of this type currently used are compass-clinometers from Suunto or Silva. Compass clinometers are fundamentally just magnetic compasses held with their plane vertical so that a plummet or its equivalent can point to the elevation of the sight line. A better clinometer (I believe) is the Abney hand spirit level or clinometer, where the object sighted and the level bubble can be seen simultaneously, so that the index can be set accurately. An Abney clinometer is shown in the photograph. A spirit level is so-called because it contains alcohol in a tube of large radius, in which the bubble moves to the highest point. Spirit levels are used for accurate surveying, although automatic levels that go back to the principle of the plummet are now frequently found, and are easy to use.

§  iber glass tape

Long fiberglass tape measure have an open reel case on this long surveyor's tape helps us more easily rewind tape. Design keeps dirt from getting trapped inside case. Non-stretch fiberglass tape is durable and waterproof. It is longer than ordinary measure of length.we used it during RMR

Planner features at the rocky outcrops

The features preserved in rock, which are responsible to found the plane surface, are called planner features. Bedding plane generally follow the deposition plane.

ü  BEDDING PLANE

In geology a bed is the smallest division of a geologic formation or stratigraphic rock series marked by well-defined divisional planes (bedding planes) separating it from layers above and below. A bed is the smallest lithostratigraphic unit, usually ranging in thickness from a centimeter to several meters and distinguishable from beds above and below it. Beds can be differentiated in various ways, including rock or mineral type and particle size. The term is generally applied to sedimentary strata, but may also be used for volcanic flows or ash layers.

In a quarry, a bedding is a term used for a structure occurring in granite and similar massive rocks that allows them to split in well-defined planes horizontally or parallel to the land surface.

ü  FOLIATION PLANE

Foliation is usually formed by the preferred orientation of minerals within a rock. Foliation is  any penetrative planar fabric present in rocks. Foliation is common to rocks affected by regional metamorphic compression typical of orogenic belts. Rocks exhibiting foliation include the typical metamorphic rock sequence of slate, phyllite, schist and gneiss.

Foliation in areas of shearing, and within the plane of thrust faults, can provide information on the transport direction or sense of movement on the thrust or shear. Generally, the acute intersection angle shows the direction of transport. Foliations typically bend or curve into a shear, which provides the same information, if it is of a scale which can be observed.

ü  JOINTS

In geology the term joint refers to a fracture in rock where there has been no lateral movement in the plane of the fracture (up, down or sideways) of one side relative to the other. This makes it distinct from a fault which is defined as a fracture in rock where one side slides laterally past to the other. Joints normally have a regular spacing related to either the mechanical properties of the individual rock or the thickness of the layer involved. Joints generally occur as sets, with each set consisting of joints sub-parallel to each other.

Joints form one of the most important types of discontinuity within rock masses, typically having no residual strength.

Attitudes of the geological Structures

Strike and dip refer to the orientation or attitude of a geologic feature. The strike of a stratum or planar feature is a line representing the intersection of that feature with the horizontal. Strike and dip are determined in the field with a compass and clinometer or combination known as a Brunton compass.

ü Strike:

The strike line of a bed, fault, or other planar feature is a line representing the intersection of that feature with a horizontal plane. On a geologic map, this is represented with a short straight line segment oriented parallel to the strike line. Strike (or strike angle) can be given as either a quadrant compass bearing of the strike line (N25°E for example) or in terms of east or west of true north or south, a single three digit number representing the azimuth, where the lower number is usually given (where the example of N25°E would simply be 025, and the other value of 205 is discarded), or the azimuth number followed by the degree sign (example of N25°E would be 25° or 205°). The dip gives the steepest angle of descent of a tilted bed or feature relative to a horizontal plane, and is given by the number (0°-90°) as well as a letter (N,S,E,W) with rough direction in which the bed is dipping. One technique is to always take the strike so the dip is 90° to the right of the strike, in which case the redundant letter following the dip angle is omitted. The map symbol is a short line attached and at right angles to the strike symbol pointing in the direction which the planar surface is dipping down. The angle of dip is generally included on a geologic map  without the degree sign. Beds that are dipping vertically are shown with the dip symbol on both sides of the strike, and beds that are flat are shown like the vertical beds, but with a circle around them. Both vertical and flat beds do not have a number written with them.

ü Dip direction :

It is the direction of the rock strata towards which it dips i.e. inclined and it always lies at right angle to the strike. Strike is the direction on sloping surface in which a horizontal line can be drawn.

ü Dip amount :

It is the maximum angle of inclination of the rock strata with the horizontal, and is measured in vertical plane.

2.2.3 Report Writing: Finally a field report was made on the basis of all the observations and findings which summarized all our activities performed at Malekhu. It also included all the geological information gathered at the various sites and locations we reached in the Malekhu area. Report gives all the information about the area we worked on.