Geology report by jitu

Geology re

1. INTRODUTIONThe geological field visit to Malekhu was organized by the Department of Civil Engineering under Asian Institute Of Technology & Management, in order to accustom knowledge about the geological structures, their engineering significance and distribution of different rocks, soil types and study of mass movement activities. The time duration being three days from 16 th to 18th Asadh, 2072 was spend in geological field study in Malekhu, 75 Km. South-west from Kathmandu.2. Requirement of CourseEngineering geology is defined as the branch of geology which deals with the application of geological knowledge in the field of civil engineering for the construction of infrastructure such as roads, bridges, dam, tunnel etc.Engineering geology is defined in the statues of IAEG as the science devoted to investigation, study and solution of different types of engineering and environmental problem which arises as the result of interaction between the geology and the work or activities of man, as well as the prediction and development of measures for prevention remediation of geological hazards.2.1.1 Importance of engineering geology in the field of civil engineeringGeology in civil engineering concerned with the engineering behavior of earth materials. It includes investigating existing subsurface conditions and materials; assessing risks posed by site conditions; designing earthworks and structure foundations; and monitoring site conditions, earthwork and foundation construction.A typical Geo-technical engineering project begins with a site investigation of soil, rock, fault distribution and bedrock properties on and below an area of interest to determine their engineering properties including how they will interact with, on or in a proposed construction. Site investigations are needed to gain an understanding of the area in or on which the engineering will take place. Investigations can include the assessment of the risk to humans, property and the environment from natural hazards such as earthquakes, landslides, sinkholes, soil liquefaction, debris flows and rock falls.2.2.2 Geological and Mechanical Principles

o Geological timeo Rock forming mineralso Rock types, Soil Typeso Mechanical fundamentals for Engineering Geologyo Soil and rock properties

1Prepared By: Jitendra Pd. Gupta

2.2.3 Geological Structure Analysis

o Geological structures (faults, folds)o Discontinuitieso Hemispherical projection (basics and borehole analysis)

2.2.4 Applied Engineering Geology

o Landslides classification for slopes in rock and soilo Mass movement in rocko Mass movement in soilo Excavation Principles in Rock and Soil

2.2.5 Engineering Geology in Practice

o Site characterization and investigation techniqueso Case histories and examples

3. LOCATION OF STUDY AREAThe study site lies on the Malekhu river banks, which extends from its confluence to the Trishuli River to about 2.5 Km. upstream. The Site itself is called Malekhu which lies on 71 Km. towards south-west along the Prithivi Highway, in Dhading district, Central Nepal.The site was selected due to availability of different rocks, the river morphology, natural topography in small extent of area and different types of mass movement along the route.The study site is easily accessible from the Kathmandu valley, a three hours bus travel along the Prithivi Highway from Thankot can easily take us to site. The study trip was facilitated by lodging and fooding at the Malekhu chowk.4. OBJECTIVES OF FIELD STUDYThe main objective of the geological field trip was to learn the basic geotechnical skills in civil engineering regarding river morphology, site investigation, landslide and petrology. The study aimed at learning general tactics regarding identification of rocks determining their major chemical contents, determining the various geotechnical parameters such as attitude of rock bedding and the observation of various physical features regarding river channel morphology and landslidesThe main objectives of our field visit were: -

Measurement of dip and strike Study of bedding foliation Handling of compass for documentation of Engineering geological data Study of landslides Study of morphology of river channel


Rock identification in the field Identification of geological units of the Lesser Himalaya and Kathmandu Nappe Engineering geological studies along the large scale geological discontinuity

(The Mahabharat Thrust) Study of the rock slope along the road corridor To know the rock mapping techniques of the rock outcrops

5. METHODOLOGYThe geological field study of the ascertained area was carried out in the following ways.

Field reconnaissance and geological traverse of the study site. Sketch of the field topography and rocks. Photographs of the field topography and rocks. Description of the field topography and rocks.

The study team of students were accompanied and guided by our respected teachers during the field study. Traversing was done along the study site and the rock samples were observed, the attitude parameters of bedding planes were obtained by the use of Brunton Compass. The idea obtained was noted and photographs of remarkable spot were taken. A firm blow of hammer check the strength and rock types (igneous, metamorphic and sedimentary) were observed.

6. MEASUREMENT OF PLANAR FEATURE OF ROCK (Chainage about 75 m from old bridge upstream in the Malekhu Khola)6.1 Rock outcrops and exposuresThese are the terminologies used to define the rock mass that is exposed to the surface that is there is no covering soil in the surface with either herbs , shrubs or any other natural coverings. Outcrop is a geological term referring to the appearance of bedrock or superficial deposits exposed at the surface of the Earth. In most places the bedrock or superficial deposits are covered by a mantle of soil and vegetation and cannot be seen or examined closely. However in places where the overlying cover is removed through erosion, the rock may be exposed, or crop out. Such exposure will happen most frequently in areas where erosion is rapid and exceeds the weathering rate such as on steep hillsides, river banks, or tectonically active areas. Bedrock and superficial deposits may also be exposed at the earth's surface due to human excavations such as quarrying and building of transport routes.6.2 Planar features at rock outcropsThe features preserved in rock, which are responsible to found the plane surface, are called planner features. Bedding plane generally follow the deposition plane.


6.2.a Bedding PlaneIn 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 litho stratigraphic 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.6.2.b Foliation PlaneFoliation 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.6.2.c JointsIn 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.

6.3 Attitudes of geological structuresStrike 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.6.3.a 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 slopingsurface in which a horizontal line can be drawn.6.3.b Dip amount

It is the maximum angle of inclination of the rock strata with the horizontal ,and is measured in vertical plane.6.4 Types of geological compassCompass is used for the measurement of dip direction and dip amount of bedding plane, folds, joints etc. there are five types of compasses in general use.

Simple compass Clinometers compass Brunton compass Clar compass Digital compass

6.5 Handling of geological compassThe compass used in the field was the Brunton Compass. Procedures to handle the compass are as follows:a. The compass should be opened carefully.b. Measurement of the dip direction and dip angle should be done carefully.c. Measurement of the dip direction and dip angle should be done as mention above.d. The rotation of the compass parts should be done carefully in such a way that the minimum force is applied.While using the compass for the accurate measurements, the compass should be aligned in the direction of the maximum inclination.6.5.1 Measurement of the Bearing (Dip Direction)The face with the mirror should be placed parallel to the planar surface also aling its maximum inclination. Then folding the other part, i.e. main part, the main, the main part should be made horizontal by centering the spirit level in it, Then the reading/bearing shown by the needle should be recorded as the dip direction of the planar feature.6.5.2 Measurement of Inclination (Dip Angle)

The edge of the compass should be aligned in the direction of maximum slope. Then leveling the bubble in the center of the tube the angle of the structure was seen, which is the dip angle. The leveling should be dine accurately. If necessary the mirror can be used. For more accurate data, the reading can be taken at two or more places in the same planar features.6.5.3 Data measured using Brunton compass


The measurement of the planner features was done at the Bank of Malekhu khola. The following readings were taken with the help of the Brunton Compass. Readings for the dip amount and dip direction taken in the field:

S.N. Dip Direction Dip Amount Attitude Remarks

1 172 86 86/172 BP

2 228 69 69/228 JP

3 90 16 16/90 JP

4 89 49 49/89 JP

5 256 61 61/256 JP

6 175 89 89/175 BP

7 90 25 25/90 JP

8 171 86 86/171 BP

16 176 86 86/176 BP

17 290 61 61/290 JP

18 122 75 75/122 JP

19 111 74 74/111 JP

20 167 89 89/167 BP


9 165 82 82/165 BP

10 154 74 74/154 BP

11 76 49 49/76 JP

12 174 84 84/174 BP

13 226 59 59/226 JP

14 71 26 26/49 JP

15 235 68 68/235 JP

21 274 64 64/274 JP

22 95 36 36/95 JP

23 162 85 85/162 BP

24 132 76 76/132 JP

25 80 47 47/80 JP

Fig : Measuring of attitudes of bed rocks

7. STUDY OF GEOLOGICAL STRUCTURESThe structural features preserved in the rock during information of rock or after formation of rock or after formation of rock is called geological structures, fold, faults, joints etc are the examples of geological structures.Continuous deformation structures: These are the products of plastic and viscoplastic deformations e.g.: - folds, veins, foliation, cleavage etcDiscontinuous deformation structures: - These are the product of brittle deformation e.g.: - joints, faults etc7.1 FoldAny type of undulations, bending and curvatures developed in the rocks due to the action of stresses in the geological past and preserved in the rocks are known as folds. Folds are the results of plastic and viscoplastic deformation in the geological past preserved in the rocks. Folds are best displayed by stratified formations such as sedimentary or volcanic rocks or their metamorphic equivalents. But any layered or foliated rock, such as gabbro or granite, gneiss, may show folds. Some folds are a few miles across. The width of other is to be measured in feet or inches or even fractions of an inch. Folds of continental proportions are hundreds of miles wide.

Fig: Fold

7.1.1 Recognition of fold in the fieldi. The easiest and simplest way is the visual d: inspection. If we find any geological structure according to the normal definition of a fold then it can be identified as fold.ii. The repetition & omission of beds also indicates the presence of fold.iii. By plotting the attitudes of beds in map


iv. When the types of folds are to be recognized on the basis of the age consideration of the beds, the top and bottom of beds are determined by taking into account the nature, and form of the features occurring on the beds itself. Accordingly some types of folds have been inferred.7.2 FaultFaults are well- defined cracks along which the rock- masses on either side have relative displacement along the fracture plane or they are the ruptures in which the opposite blocks moved past each other. The displacement is parallel to the fracture plane. The attitude of faults is defined in terms of their strike and dip. The strike and dip of fault are measured in the same way as they are for bedding.

Fig: Fault

7.2.1 Recognition of fault in the fieldTo recognize the faults in the field, a number of criteria are used. The faults may be directly seen in the field, particularly in artificial exposes such as river-cuttings, road Cuttings, etc. In field the faults may be recognized asi.Variation in the behaviour of the groundii.Evidences of the past deformationiii.Change in bearing capacity of the materialsiv.Deviation in stress pathv.Variation in the hydraulic behaviour

7.2.2 Structure formed during faultingi. Slicken sides: They are the polished and or striated or grooved surfaces which are produced due to rubbing action of the adjacent blocks during the act of faulting. These form important evidences of faulting.ii. Gouge: - It is a finely pulverized, clay-like powered rock material, which occurs at or near the base of the faulting zones. It is obviously the result of strong rubbing action on the rocks during the faulting process.iii. Fault Breccia: - It is the crushed (and but powdered) angular, fragmentary material produced during faulting and found in some cases at or mar the base of the up thrown block. Very often the angular fragments get embedded and cemented in the gouge and produce a rock-like mass once again which is also called fault-brecciaiv. Mylonite: - This rock also called micro breccia, is extremely fine-grained and very hare and coherent. Faulting is believed to be the cause of development of such rocks. It is the metamorphic form of fault Breccia.At chainage 330m upstream from Malekhu old bridge along left bank fault zone was observed.

7.3 Joints


A joint is defined ,as a fracture in a rock between the sides of which there is no observable relative movement . They are present in most consolidated rocks of igneous , metamorphic and sedimentary origin.7.3.1 Field identification of jointsi. Joints are generally recognized in the field as faults without relative displacement. Their dimension varies within wide –limits. Sometimes they are very short in their extension, but in certain cases they are found to extend for miles together.ii. Joints commonly control the drainage pattern of an area. They also determine the shape of coastlines, because they provide a passage, whereby water may penetrate deeply into rock mass thus allowing weathering to take place.iii. Jointed rocks are pervious to fluids and may act as aquifers or reservoir rocks for oil or natural gas.iv. Sometime joints act as avenues for molten rock materials to come above the surface. It also determines the localization of some mineral deposits.7.4 ThrustA kind of reversed fault in which hanging wall has actually moved up relative to the footwall is called trust.e.g.: - Mahabharat thrust separates Nuwakot complex and Kathmandu complex.7.5 UnconformitySurface of erosional and depositional gap within a sequence of strata is called unconformity.These are usually the weak contact where the failure starts to generate. It created permeability contrast thus natural springs or discharge can occur in such places.At Chainage 100m from suspension bridge above Trishuli river along Dhading Besi old road unconformity was seen. Among series of rock strata soil and stone deposition could be seen which established an unconformity at that place.

8. STUDY AND IDENTIFICATION OF ROCK IN THE FIELD ( along the malekhu river and old Dhading Besi road )8.1 IdentificationRocks are the aggregates of minerals, which form the earth's crust. So rocks are composed of the minerals. According to the modes of origin, all rocks are categorized into three major groups. They are: -i. Igneous rocks or primary rocksii. Sedimentary rocks of secondary rocksiii. Metamorphic rockRocks are identified in the field by the study of its size of grain or texture, shape of grain layers, color, composition of minerals etc as they exposed naturally or artificially on the surface of the earth.

8.2. Igneous Rock9

Prepared By: Jitendra Pd. Gupta

These are the rocks formed by the solidification of magma either under neat the surface or above it: accordingly they are divided into two groups:a. Intrusive bodies: which are formed underneath the surface of the earthb. Extrusive bodies: which are formed due to consolidation of magma above the surface of the earth. These are also known as volcanic rocks on the basis of the depth of formation, intrusive rocks are of two type s:tectonic rocks: which are formed at very depths.Hypobysal rocks: which are formed at shallow depths.8.2.1 Identification of Igneous Rock in the field

i. Generally igneous rocks are hard, massive, and compact with interlocking grains.ii. Entire absence of fossils.iii. Absence of bedding planeiv. Random orientation of mineralsv.Usually contain much feldsparXenoliths: - The relic of the host rock preserved in the igneous rock is called xenoliths.8.3 Sedimentary RockSedimentation rocks are formed by the process of sedimentation. Sedimentation is the process by which the rocks are formed from the deposition and consolidation of sediments or precipitation of soluble material s in layers .The sediments are formed from the weathering of old rocks either igneous metamorphic and even sedimentary itself and are then eroded and transported by geological agents (water, wind, ice). These eroded and transported sediments are then deposited on the depositional basic and accumulated layer by layer one after another.According to the modes of transportation of the deposits these rocks are sub -divided into three types:i. Mechanically deposited (clastic rock)ii. Chemically and organically formed (non-clastic rock)8.3.1 Identification of Sedimentary Rock in the fieldi. Generally, soft, stratified i.e. characteristically bedded.ii. Fossils commoniii. Statification, lamination, cross bedding. Ripple marks, mud-marks etc are the usual structures.iv. No effect on the enclosing or the top and bottom rocks.v. Quartz, clay minerals, calcite, dolomite, hematite are the common minerals.E.g.: - calcite, limestone, magnesite, sandstone, shale, etc.8.4 Metamorphic RockThese are formed by the alternation of pre-existing rocks by the action of temperature, pressure added by sub-terrain fluids (magnetic or non magnetic).8.4.1 Metamorphism


It is a natural process whereby the pre-existing rocks are altered or modified under the influence of pressure, temp. & the chemical solution. Under the influence of those factors, the rocks are changed into new rocks physically and chemically .In metamorphic rocks minerals are arranged in preferred orientation.Types of metamorphism are:i.Dynamic metamorphismii.Thermal metamorphismiii.Dynamo thermal metamorphism8.4.2 Identification of Metamorphic Rock in the fieldi. Generally hard, interlocking grains and bedded (if derived from stratified rocks)ii.Foliated, gneissose, schistose, granular lose, slaty etc are the common structure.iii. Fossils are rarely preserved in rocks of sedimentary origin except slate.

iv. Common minerals are andalusite, sillimanite, cyanite, cordierite, collastnite, garnet, graphite etc.E.g.: - slate, phyllite, schist, gneiss, amphibolites etc

a. QuartziteIt is usually light colored with shades of gray, yellow. It has medium specific gravity (i.e. Sp.Gr. =7). It has quartz, as major constituents while others are mica, feldspar. It is medium grained and the texture is massive and granular.b. SlateIt is a black rock with low or medium specific gravity. Flaky minerals are quite abundant and others are hard to distinguish. The rock is compact and can be scratched by knife. It has foliation with slaty cleavage.c. MarbleIt is the rock of medium specific gravity, which is light colored. The major component is calcite. Texture is massive and granular. A knife can scratch it.d. SchistIt is the rock that has extremely variable color and specific gravity. The dominant constituent is calcite. Others are mica, quartz and special minerals like muscovite (white colored), biotite (black colored), and chlorite (green colored). The rock is fusible and the property is called schistosity.e. GneissIt is the rock with dark and light streaks or bands in alternating specific gravity are variable. Garnet (like mustard seed) can be seen in the rocks. The grain is medium or coarse. The structural feature is called gneissosity.f. PhylliteIt is a greenish and soft type of rock. It is layered and foliation plane is quite dominant with incompetent beds (the thickness less than 1cm is called foliation other it is called bed). No distinct grains can be seen. It is an igneous rock that has changed into metamorphic rock.8.5 Discussion comment


According to the observations taken in the field, most of the rocks are metamorphic in nature and sedimentary and igneous rocks in least. These are the rocks that an engineer has to deal most with in the engineering practice. The small sample tested in the laboratory cannot represent all the complex properties of the related rock. Even, if the rock has preserved the mentioned quality, it may not be capable to resist the loads as we expected because of the conditions at the site. So the strength, weathering condition, orientation and the spacing of the joints and faults etc properties has to be studied in the detail to know completely the property of the rock. These detail properties of the rocks can be known after the field visit of the rock. Site for any engineering work has to b suggested only after these detail studies of the rocks had been made. Hence field identification of rock has greater importance in the field of civil engineering practice.8.6 Major Rock type of the field areaDuring our study we found different rocks in our study area. The major rocks are summarized as follows:The metamorphic rocks found in the field are described below:8.6.1 SlateSlate is an extremely fine-grained metamorphic rock characterized by a slaty cleavage, by virtue of which it can be split into thin sheets as roofing material. Due to its low crushing strength it is also used as building material. It was found at a distance of five hundred meter north of highway.8.6.2 PhylliteIt is a medium to fine-grained metamorphic rock of complex silicate composition. The rock shows a foliated structure and represents as intermediate stage the presence of muscovite was found in the rock. This is found at the south from the highway along the stream.Dark green type of phyllite was found in the Robang Formation(RB).

8.6.3 SchistSchist is megascopically crystalline metamorphic rock characterized by the typical schistose structure. The constituent platy and flaky mineral and are arranged in irregular parallel layers of bands.8.6.4 MarbleMarble is essentially a granular rock composed chiefly of recrystallized calcite. It is characterized by a granular structure. Marble often show banded structure. Marbles are commonly used in building constructions in the form of blocks, slabs, aches, and as chip for flooring. It is also used as decorative and ornamental purpose. In Malekhu it was found at a distance of three thousand two hundred seventy five meter south from the highway.8.6.5 GneissGneiss is a megascopically crystalline metamorphic rock characterized by segregation of constitute minerals into layers of bands contrasting color, textures


and composition. Feldspar and quartz are commonly in gneiss than in Schist. Dark minerals of ampibole and pyroxene group are also common. The compact, dense, massive varieties of gneiss are used in building and road metal.In Malekhu it was found at a distance of four thousand six hundred fifty meter south from the highway. The gneiss was found in the boulder as an eye structure and so called Augen Gneiss. This was found on the Kulekhani formation (ku) of Bhimphedhi group.8.6.6 QuartziteQuartzite is granular metamorphic rocks composed chiefly of intercultural grains of quartz. The name Orthoquartizile is used for a sedimentary rock of similar composition but of different origin; it has siliceous cement. It contains sub-ordinate amount of micas, feldspars, garnet and some amphiboles which result from the impurities of the original sandstone during the process of metamorphism. The rock is generally very hard, strong, dense and uniformly grained. It finds extensive use in building and road construction.Different types of SEDIMENTRY ROCKS found in the field of study are as follows

8.6.7 LimestoneThese are the most abundant sedimentary rock formed from the non-elastic group and are composed of chiefly calcium carbonate. However the presence of dolomite, quartz, feldspar and iron oxides is rather a common mineral. Limestone is a primary source of materials for the manufacture of Portland cement and for a wide variety of limes. Its other uses are in the Metallurgical industries as a flux.It was found along the Prithvi Highway towards Gajuri as the Robang Formation (RF) as a Malekhu Limestone Formation (ML) in the Upper Nuwakot Group.8.6.8 SandstoneSandstone is a mechanically formed sedimentary rock. It is formed by the cementation of the sand particles of sized between 1/10mm to 2mm in diameter. Sandstone is perhaps the most familiar of all the rocks as it is usually quarried and used more than any other rock, for all types of buildings. The various varieties of sandstone are named after the cementing material. E.g. Siliceous Sandstone, Ferruginous Sandstone, Calcareous Sandstone, Argillaceous Sandstone etc.8.6.9 BrecciasBreccias are a mechanically formed Sedimentary rock consisting of the angular fragments. These sediments are heterogeneous in nature; cemented together by clay; iron oxide, silica or calcium carbonate and are generally of more than 2 mm size. Because of the heterogeneous character they are not used as building stines but some of the varieties which are susceptible to polish can be used for ornamental works.Igneous Rocks found in the field of study are described below:


8.6.10 GraniteGranite may be defined as the Plutonic light colored igneous rock. These are among the most common igneous rock. Two most common and essential mineral constitutes of granite are Quartz and Feldspar. The first is always recognized by its vitreous luster, with MHN 7 and cleavage less wide translucent appearance. Feldspar, forming Granite may be of two types: K-Feldspar, commonly Orthoclase and the soda bearing Plagioclase Feldspar like Albite and Oligoclase. Feldspar microcline may occur in some granite.Agra Granite was found in the right bank of Malekhu Khola south west of "Chhapan Danda".The study of metamorphic rocks (now exposed at the Earth's surface following erosion and uplift) provides us with very valuable information about the temperatures and pressures that occur at great depths within the Earth's crust.8.7 Major Rock Types of the Field Study Area

S. N.

Physical Properties Sample 1 Sample 2

1. Colour Grey White

2. Texture Non Crystalline Crystalline

3. Structure/Cleavage Foliation, Slaty Bedding

4.

5.

Sp. Gr.

Acid Test/ Hammer scratch Test

Low

_

High

React with Acid in the powder form when sample is scratched by the hammer

6. Mineral Composition Chloride, Mica, Clay Dolomite, Calcite

7. Rock type Metamorphic Sedimentary

8. Rock Name Slate Limestone(Dolomite)

9. Engg. Significance: Strength Drillability

Blastibility

Low

High

Low

High

Low

High

10. Uses Roofing Construction Materials


11. Geological Formation Benighat Slate Malekhu Limestone

S. N. Physical Properties

Sample 3 Sample 4

1. Colour Greenish Grey White

2. Texture Non Crystalline Crystalline

3. Structure/Cleavage

Foliation, Slaty Random self interlock

4.

5.

Sp. Gr.

AcidTest/ Hammer Scratch Test

Low

-

High

-

6. Minerals Serisite+Slate Minerals Muscovite,biotite, plagioclate quartz

7. Rock type Metamorphic Igneous

8. Rock Name Phyllite Granite

9. Engg. Significance:

StrengthDrillability

Low

High

High

Low

Blastibility Low High

10. Uses Robang Formation Agra Granite

S. N.

Physical Properties

Sample 5 Sample 6

1. Colour Grey Grey


2. Texture Crystalline Crystalline

3. Structure/ Cleavage

Foliation Foliation Gneissosity

4. Sp. Gr. High High

5. Minerals Quartz Feldspar, quartz, biotite, muscovite

6. Rock type Metamorphic Metamorphic

7. Rock Name Quartzite Gneiss

8.

9.

10.

Engg. Significance:StrengthDrillabilityBlastibility

Uses

Geological Formation

HighLowHigh

Construction Materials

Dunga quartzite

High

Low

High

Construction Materials, aggregate, foundation material

Kalitar Formation

S. N. Physical Properties

Sample 7 Sample 8

1. Colour White Grey

2. Texture Crystalline Crystalline

3. Structure/ Cleavage

Preferred Orientation of mineral

Foliation, schistosity

4. Sp. Gr. Medium Low


5. Acid Test/ Hammer Scratch Test

Acid reacts vigorouslySample is scratched by hammer

-

6. Minerals Calcite, silica, quartz, muscovite, pyrite

Chlorite, Clay, quartz, granite, mica granite

7. Rock type Metamorphic Metamorphic

8. Rock Name Marble Schist (garniteferrous)

9.

10.

11.

Engg. Significance:StrengthDrillabilityBlastibility

Uses

Geological formation

Medium to highHighHigh

Flooring, construction Material , raw materials for cement if calcium carbonate is more than 43%

Bhainse Dobhan marble

Low

High

Low

Construction of dry wall, flooring

Raduwa Formation

9. STUDY OF RIVER CHANNEL MORPHOLOGYRiver is a mass of water that flows along a path high to low gradient carrying different materials and responsible for different geological actions,such as erosion,transportation and dopositation of sediments.The route along which river


flows is called river valley.In engineering practice,many structures ,such as dam,bridge ,reservoir etc. are constructed in the river channels. Besides construction of infrastructures,construction materials are also barrowed from the river territory.

9.1 Types of river channel9.1.1 Straight River .The river channel in which water is flowing in the same direction on straight path is straight river channel. The prefect straight channel is rare and if present, the length will not exceed ten times its width. The straight channel is formed in the youth stage and at the head region of the river. The gradient of the river is high causing the flow of velocity high.Since the energy level of such river is high .the erosional rate is intensely higher than the deposition of the sediments.Deep scouring along the river path is higher than the side cutting.straight rivers are dominantly occurred in the Higher Himalayan region.9.1.2 Braided RiverIn this type of river ,a single river path is diverted into several paths and may converse to single later.the topography of the area is characterized by low relief. The gradient of the river path is so low and the river area is widened and flow with lower velocity.In the terai area the velocity of water in the river channel is low and waters flows from different small channels. Since the energy level of such river is low ,the deposition rate of sediments is intensly higher than the erosional rateThick successions of sediments go on depositing along the river path and river diverts to other subparts.9.1.3 Meandering RiverRiver channel in which course of river bends towards different directions within small area is known as meandering river channel. This type of river flows along zigzag path.The gradient of the river type is so moderate that the river strikes on one end and return to other direction making zigzag path. The channel is characterized by low velocity, soft rock type and is formed at the matured stage of the river.Meandering channel maintains a fairly steady width because erosion and widening of the channel on one side is balanced by deposition and narrowing on the other.9.2 Land form develop by river channel morphologies9.2.1 Oxbow LakesThe individual loops of meandering stream in the advanced stage are separated from each other that only by a narrow stripes of lands. During large water discharging time the river has tendency to flow straight the stream starts flowing in that particular region leaving the loop on one side as an isolated detached or only slightly connected parts. These isolated curves or loop shaped part of the meandering stream often contain some supplies of water when they are called the ox-bo lakes. In case of meandering rivers, the streams detach loops and


charge their path across the shortest route. An oxbow is formed when neck of the meander is reduced very much which is due to the low strength of the rock.

9.2.2 Pet HolesThese have various dimensions, shapes and are the depression, which are excavated in the riverbeds by extensive erosion. These are formed in soft rock in the cylindrical or bowl shaped. These are initiated by plucking out of pieces of soft rocks from riverbeds due to the velocity of water abrasion and further depressions.9.2.3 River ValleysIn general, every large river forms its own valley. Valley is the low land surrounded by hills of various slopes. The erosion processes due to the cutting up of the bed form the valley.

9.2.4 EscarpmentRiverbanks might have alternate soft and hard rock layers. The soft rocks get eroded quickly and the hard rocks get eroded later on. As the river continues its flow, the bank falls suddenly creating a steep slope. This is known as escarpment.9.2.5 FansWhen rivers with low gradient enter the lower surfaces, the materials brought by the river get accumulated. Also, the structure is not affected, as erosion doesn't take place as water of the river flow over the structure.9.2.6 Delta DepositionThe deltas are the triangular structures formed by the alluvial deposits at the mouth of the river. Whenever a river with high gradient enters the standing water source the river deposits some of the material brought by it. The continuous deposition of material results in the formation of delta.The number of river channels when meet at the point the flowing water looses the velocity and therefore no other way then to drop down the balance of its load right at this point of emergence at the mouth of the river known as the delta deposition.

Fig: River terrace

9.3 River channel morphology at the Trishuli-Thopal Confluencei. Erosion bank:The bank of the river, which is weaker part, has the tendency to get eroded. This is the unstable bank of the river.ii. Deposition bank:The bank on which deposition process takes place is called deposition bank.iii. Channel bar:


The accumulation of the materials at the mouth of the river is called channel bar.iv. Flood plane:The plane or the area covered by the river when the river is in the flooding condition. At these places, materials from very fine to coarser conditions are found.v. River terrace:The area that the river used in the past to cover during flooding or normal condition is called river terrace. This is the area has left the channel level to lower level and the remnants of earlier deposits to form higher level. This area is very suitable for human settlement. Gravel and sand is found in such places.vi. Side bar or Point bar:These are the remaining of deposits carried out by the river at the stage of higher discharge. This is also known as side bar.vii. Island:It is the area formed by the river deposition. It is not necessary to be at its mouth.Right bank of the Trishuli River at the height of sixty meter above the old road from Malekhu to Dhading Besi three hundred meter upstream of suspension bridge. Conference of Thopal Khola and Trishuli River.

10. ENGINEERING GEOLOGICAL DATA COLLECTIONCollection of engineering data from outcrops for certain purpose is called engineering geological data collection. Engineering data are those, which are purposed specific and quantitative. These data collected from outcrops are attitude of rock (i.e. dip and strike).10.1 Intact massIntact rock is the part of the rock mass which is free from the discontinuities. The combination of the intact rock and the discontinues form the rock mass. Size of the intact rock is small at the surface and large below the surface. It is different from different types of the rock.Intact rock strength:It has already been explained that the intact rock is the rock material without discontinuities. They have greater strength than the rock mass. Their strength can be determined in the following ways:

Check in lab: Required size of intact rock can be taken from the rock mass and checked in the lab.

Check by hammer striking: This is the cheapest and easiest way to find out the approximate strength of rock material and this can be done directly in the field. For this,

rock material is struck by geological hammer and the sound is identified. If metallic sound comes then the rock material is strong having strength more than 100Mpa and if sound is as in soil then the rock material is weak having strength


less than 10Mpa. If sound is in between metallic to soil, then strength is also in between 100Mpa to 10Mpa.

Schmidt hammer: it is also an easy but nearly accurate method to check the intact strength. it can give numerical value of strength of the rock material.Actually the hammer is a special type of hammer which measures the rebound value.

10.2 Rock MassThe collective mass formed by the rock material ana discontinuities is called rock mass. So the rock exposed on the outcrop is not rock,in fact it is the rock mass.Rock materials (intact rock)is a part of rock mass. since in actual practice discontinuties are present, rock material alone doesn't exists in nature.10.3 Parameters of Engineering Geological Data10.3.1 Rock typeThe rock are classified on the basis of the characteristics of intact rock as well as the discontinuities present.

Cleavage/foliation plane ,bedding plane Materials Particle size textures etc.

10.3.2 OrientationOrientation of discontinuities is the attitude of the discontinuities. Depending upon the slope of discontinuity rock has different strength at the different direction .If the direction of the discontinuity is in the same direction as the rock mass ,it is an unfavorable condition. But if the discontinuity is in opposite direction to the rock mass,it is a favorable condition.10.3.3 rock strengthThe strength of the intact rock is tested by Schmitt Hammer rebound test. Schmitt Hammer is the instrument used to test bearing capacity of site rock mass by rebound test. There are two ways of testing by Schmitt Hammer,one is uni-axial and another is tri-axial test.10.3.4 SpacingIt is the perpendicular distance between the two adjacent discontinuities of the same set.The space between the discontinuities set in the same direction also causes variation in the strength of the rock.The rock material in between the discontinuity is intact material .The volume of intact material governs the strength of the rock.10.3.5 ApertureAperture is the open spacing present in the rock due to discontinuity present in it .The crack due to any means like alkaline water has high tendency to dissolve calcite material may get widened up Depending upon space it is classified as widely open (>1 cm),open (2 mm-1 cm),close (<2mm),tight (<1mm).The


apertures wide and open cause the mechanical discontinuity as no stress is transferred all over the the rock. However if the open discontinuity is filled with any other material then strength is transferred. The open and close aperture if is filled by any other material then the strength and the stability of the rock increases depending upon the material type filling the aperture.

10.3.6 RoughnessIt is one of the characteristics of the discontinuity present in it. In rough discontinuity surfaces due to low friction shear strength is high. It is generally of two types rough planar(rough surface with a plane flow) rough wavy (rough surface with a wave like flow).10.3.7 SeepageIt is the flow of water under gravitational forces in a permeable medium.Flow of water takes place from point of high head to a point of low head.

11. CONCLUSIVE REMARKS

Once heard thing may be forgotten but once VISITED thing never forgotten. This main purpose of field trip conducted by AITM. Minimum knowledge require for engineers in geology field is fulfilled in this trip.

The subject GEOLOGY is really one of the most important subjects for CIVIL ENGINEER. The three day tour on MALEKHU area has proved as a chance to learn the various geological resources of the site,geological events,geological conditions, and the related area to the engineering point of view .The study was related to the practical as well as theoretical. In this tour, we saw and felt the major type of rocks in their natural condition and pictured them. The visit has yielded rich knowledge and the information about the morphology of the MALEKHU river which merges with the TRISULI river. It has also yielded good knowledge and information about the landslides and their impact on the local and national economy. The use of geological compass to find the attitude of a rock.Finally it will be better to say that if there had not been any geological trip,we would not have learnt a lot of these information as theoretical knowledge is not enough for field work. So this geological helped a lot us for study and later on during field works.
