malekhu geology tour report Pulchowk campus

Institute of Engineering

Pulchowk Campus

Pulchowk, Lalitpur

A

Field Report

On

Engineering Geology

(EG523CE)

(Malekhu, Dhading)

Submitted To: Submitted By:

Prakash Chaddra Ghimire Bishnu Prasad evkota(063bce026)

Geology Section Hari Prasad Paudel (063bce033)

Department of Civil Engineering Kosha Raj Rimal (063bce042)

Lalan Yadav(063bce045)

Manish Man Shakya (063bce048)

Date: -26^th may 2008

aCKNOWLEDGEMENT

At every step, an engineer has to encounter earth and earth, as a material or as construction site. So it proves the importance of geology to civil engineering professionals. He or she must go through the inner core of engineering geology for his/her perfection and for professionalism.

The trip was really fruitful to us and certainly we got a lot of knowledge about the earth.

Thank you Er. Praksh Chandra Ghimire for sharing a part of his brain. Thank you Mr. Ajaya sir and Pal??……. sir to help us in field and giving complete suggestions. We also express our deep sense of gratitude to other geologist from TU for their guidance during field visit. Thanks for Mulmi sir too for printing this report. At last, we would like to thank all our friends of other groups who cooperate kindly in team work ………………………...All of you did a wonderful job to lay out these pages.

At last, we would like to express our gratitude to our college, institute of engineering. We are proud of being students of pulchowk campus.

Bishnu P. Devkota (063bce026)

Hari P. Paudel (063bce033)

Kosha Raj Rimal (063bce042)

Lalan Yadav (063bce045)

Manish Man Shakya (063bce048)

table of content

01. Introduction………………………………………………………………….

8 introduction

8 Objective of the study

8 Location of study area

02. Study of mass movement and study of preventive and corrective measures…

8 Mass movement

8 Causes

8 Classification

8 Prevention and corrective measures

8 Description of each location

8 Sketches and photographs

03. Measurements of attitude of planar features of rock……………………

8 Types of geological compass

8 Handling of geological compass

8 Rock outcrops

8 Exposures

8 Planar features and Attitude of planar features

8 Observed data in the field

8 Sketches and photographs

04. Identification of rocks in the field……………………………………………

8 Rock and its classification

8 Rock and its identification

8 Types of rock identified in the field

8 Description of each location

8 Engineering significance of the rock

8 Sketches and photographs

05. Geology of study area………………………………………………………

8 Regional geological framework

8 Geological formation

8 Rock types in the formation

06. Study of geological structures in the field……………………………

8 Geological structures

8 Types of geological structures

8 Geological structures observed in the field

8 Civil engineering significance of the geological structures

8 Sketches and photographs

07. Study of river channel morphology………………………………………

8 River morphology

8 Types of river morphology

8 Features developed by river channel

8 Civil engineering significance of river channel

8 Sketches, photographs, description of the location

08. Engineering geological studies of the rocky outcrop……………………

8 Define engineering geological data

8 Parameters of engineering geological data

8 Engineering geological data observed in the field

8 Civil engineering significance of the geological data

09. Rock mass…………………………………………………………………

8 What is the rock mass

8 Classification of the rock mass

8 Sketches and photographs

10. Conclusions………………………………………………………………

References…………………………………………………………

1.0 introduction

1.1 Introduction

What lies on the earth and inside it?

The curiosity gave birth the geology; the science of earth. It is an applied science, which deals with hills and mountains, valleys and Georges, and along lonely forests and rugged terrain. In geological fieldwork examination of the outcrops of rock, bodies upon the earth surface are carefully studied in details and reasonable inference on the geological structure and history of the region are drawn. With good approach to the geology and reasonable common sense of logical interpretation, one can form a neat picture of the geology of the region.

The three days from 11^st of Jestha to 13^th of Jestha we were taken to Malekhu for geological study. First day, we learnt the mass movement activities in the area along highway and also were taught to handle the geologist compass to measure dip and strike. On the second day, we got ideas about river morphology, identification of rock and different geological units of lesser Himalaya and Kathmandu nappy. On last day, we had learnt; how rock mapping is done? This performance was very effective for knowledge and experience. However the three days trip was not sufficient to fulfill the thirst of us.

1.2 Objectives of the Study

Ø To measure strike of bedding plane

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

Ø To identify the rock type and its property.

Ø To understand the River morphology

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

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

Ø To Study the mass movement.

1.3 Location of study area

Malekhu lies on lesser Himalayan unit of Nepal. It has peculiar geological features within a small range of area. The Malekhu V.D.C. of Dhading district lies about 70 Kms south west of Kathmandu valley and is located at latitude of 27o 50' 38'' to 27o 45' 50'' and longitude of 24o49'5'' to 84o50' 50’’. It is situated on the bank of Trishuli and Malekhu river. The Trishuli river is running from the eastern direction to the western diredtion and the Malekhu river from south to north which mingles into the Trishuli river. Also, the Malekhu river has a tributary namely the Apakhola which meets the Malekhu river at a distance about 3 kms from the Malekhu bazzar. Climatically Malekhu is a sub-tropical zone. Mainly the rainfall is during the monsoon.

2.0 Study of Mass Movement Activities and Their Preventive and Corrective Measures

Mass movement

Mass movement is one of the most challenging slope process related to the potential energy developed due to the gravitational stress may or may not influenced by the pore water pressure. Slope failure, landslides and debris flows are the major mass movement’s phenomena. As the mechanism of the mass movement differ the necessary treatments and stabilization measures are also different from its complex type of mass movements are frequent in the area, which makes the treatment more challenging.

Classification of mass movements:

1. Landslide

2. Slope failure

3. Debris flow

Landslides

Large dimensional slow to sometimes rapid but continuous movement of large weathered rock or soils on a clear slide surface are called the landslides. Sliding surface usually contains clay and the activities are influenced by the ground water. Treatments of the landslides are expensive and site specific. Effective treatments of the landslides demand the geo-technical investigation of the unstable area. Stability measures in the landslides are big challenges for many of the civil engineering structures.

Slope failure

Relatively small dimension movements of weathered rock or soil layer in the slopes are called as slope failures could lead to more stable configuration may redistribute the rock material in less steep slopes and it relief the stress by reducing the high concentration of stress usually present at the valley bottoms. At the same time slope failure weaken the rock mass providing the already sheared surfaces at the residual strength, the reactivation of instabilities as once failed rock mass has not always reached complete stabilization. The slope failure loosen the rock mass and open the stress relief joints or fractures. Cleaning of the debris is considered as the best solution in case of the slope failure along the road but it could sometimes lead to disaster landslides. Smaller magnitude slope failure was generated in the Krishna Bheer in the monsoon of 2000, which leads to disaster landslides during of the same year.

Flow/spread/creep

When the shear strength of the big slope material considerably reduced the rapid movements of the solid earth materials including large volume of water can take place. If the material is complex debris such phenomena are called debris flow. If the flow is fine the phenomena is called odd flow. Sometimes the viscous materials could spread down slope. The flow but continuous movement of the slope containing the thicker soil, largely without any distinct slip surface is recognized as creeping. Stability measures against flow spread and creeping are complex and demands considerably high costs.

For individual location of individual exposure, the traditional basic classification of the instability mechanism of the rock is also applicable.

Ø Curvilinear slip

Ø Plane sliding

Ø Wedge sliding

Ø Toppling

Ø Buckling

Conclusive remarks

Hill slope stability mechanism in Nepal is complex, which made the stabilization of a slope a challenging task for the civil engineers. A sound knowledge of the instability classification and the stability analysis helps them to choose the most effective stabilization measures and hence to face the challenges brought by the hill slope instability.

Preventive measures

Ø Concrete machinery wall

Ø Gabion wall

Ø Planting grasses

Ø Proper drainage system e.g. Cascade...

Ø Making balanced natural system i.e. removing disturbance in the area e.g. vehicle load etc. as possible.

Description of mass movement in each location, causes and prevention:

Location no- A “Mass Movement”

Typical example of mass movement (landslide, slope failure and debris flow) was found at the left side of the Prithivi highway when moved from Kathmandu. It was found at the chainage of 17km along Tribhuwam Rajpath. The abnormality formed is may be due to the construction of the road.

Causes

It is due to:

Ø Road construction and the stress developed my road vehicle.

Ø Potential energy and gravitational energy.

Remedy:

It can be stabilized by:

Ø Plantation of grass

Ø Gabion wall, Stone machinery wall, Creep wall etc.

Ø Check wall

All these work has been implemented in this failure and is seen to be under improved condition towards stabilization.

Location no- B “Anchor Work”

Typical example of the “Anchor work” had seen about 100m ahead from the “location no- A” along the Tribhuwan rajpath. The anchor work has seen to be implemented for making the road free from mass movement.

Location no- C “Continuous Moving Mass”

A typical example of the continuous moving mass had observed about 100m ahead from the “location- B” along the Tribhuwan Rajpath. We can say that the mass is moving continuously it is because of:

Ø Tilted trees

Ø Deformed Gabion wall

Location no- D

Belkhu Khola Bridge, on the Prithivi highway is the next location we observe. This location was chosen for the study of bridge site selection .the Bridge was newly constructed after destruction of older bridge due to flood. The older bridge was laid below the flood plane under estimated by engineers and went away. The new one lies quite above than the older one and safe for the recent flood level.

The bridge site should select over the level where the recent flood level occurs but shouldn’t under or over estimate.

The natural visible part i.e. outcrops of earth also we had seen from the same location. Puzzling fact was that, the slope was vertical and stable too. Normally, the slope of 35 to 65 is quite unstable. The outcrop lies at the right bank of the Trishuli River. The green band could be seen from belkhu Khola Bridge that is vegetation. Permiability contrast between two-layer gives room for seepage flow resulting vegetation.

Location no- E “Complex Landslide”

A complex landslide had observed at the chainage of +42km along the Prithvi highway from Kathmandu. Three types of remedies had seen implemented in this area and are

Ø Cascade drainage for surface drainage.

Ø Gabion wall for stabilizing continuous moving mass.

Ø Stone machinery wall for stabilizing the fixed mass in the bed rock with weep hole and sub-surface drainage system.

Ø Planting of proper type of the grass.

Location no- F “Rock Slope Failure”

Rock slope failure has observed at the chainage of +42km along the Prithivi highway from Kathmandu. The location consists of tension cracks on the rock surface. This part lies exactly over the crown of the plane failure, wedge failure, slope failure.

Causes:

Ø Dynamic load by vehicle.

Ø Improper cutting of rock bed during road construction

Remedy:

Ø Crack should be filled by fine cementing materials.

Ø Gabion walls as catch wall may be effective to resist differential stress and we had seen implemented in the field.

Ø The road alignment can be shifted inward if possible.

Now days this rock has seen to be going towards temporarily stabilization.

Thus, by studying various mass movement activities at the area, we have concluded how it occurs? What are the causes and its prevention measures? Actually, it depends upon the nature and mechanism of the failure and its location.

3. Measurement of Attitude of Planner Features Of Rock

3.1 Types of compass are as follows:

1. Clinometers compass:

The compass, which can measure bearing and orientation with two sets. Since it doesn’t consist the sprit level, it should leveled by approximation and may not be accurate.

2. Burnton compass:

It consists of sprit level and can measure bearing and inclination with relatively less error.

3. Clar compass:

It can read both inclination and bearing at once. Relatively easier to handle.

4. Digital compass:

Displays digits as reading. Easy to handle.

5. Digital PC compass:

The compass directly connected to the computer. Do not need to booking.

3.2 Handling of geological compass:

A geological compass is used to measure the attitudes of the geological features. The compass was mainly used for measuring the bearing of object with respect to north and to measure inclination .The main operation of geological compass consists of opening the compass carefully, leveling the spirit level and placing the compass on the planer feature for measurement.

3.3 Rock outcrops:

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.

Outcrops allow direct observation and sampling of the bedrock in situ for geologic analysis and creating geologic maps. In situ measurements are critical for proper analysis of geological history and outcrops are therefore extremely important for understanding earth history. Some of the types of information that can only be obtained from bedrock outcrops, or through precise drilling and coring operations, are; structural geology features orientations (e.g. bedding planes, fold axes, foliation), depositional features orientations (e.g. paleo-current directions, grading, facies changes), paleomagnetic orientations. Outcrops are also critically important for understanding fossil assemblages, paleo-environment, and evolution as they provide a record of relative changes within geologic strata.

3.4 Measurements of attitude of planar features of rocks in the field

Location No- L1:

About 100m far from the old (broken) bridge along Prithvi Highway.

S.N.	Dip Direction (degree)		Dip Amount (degree)	Attitude	Plane	Remarks
Observed By Bishnu Prasad Devkota
1	263		60	60/263	J.P
2	117		68	68/117	B.P
3	348		85	85/348	J.P	J.P=Joint Plane
4	087		42	42/087	J.P
5	080		14	14/080	J.P	B.P=Bedding Plane
6	085		13	13/085	B.P
7	265		56	56/265	B.P
8	079		32	32/079	J.P
9	175		82	82/175	B.P
10	356		19	19/356	J.P
Observed By Hari Prasad Poudel
1	090	36		36/090	J.P
2	265	50		50/265	J.P
3	180	86		86/180	B.P
4	245	65		65/245	J.P
5	220	73		73/220	J.P
6	082	53		53/082	J.P
7	165	88		88/165	B.P
8	080	58		58/080	J.P
9	252	54		54/252	J.P
10	082	27		27/082	J.P
Observed By Kosha Raj Rimal
1	271	51		51/271	J.P
2	082	14		14/082	J.P
3	162	53		53/162	B.P
4	172	56		56/172	B.P	J.P=Joint Plane
5	088	26		26/088	J.P
6	344	74		74/344	B.P	B.P=Bedding Plane
7	263	20		20/263	J.P
8	171	86		86/171	B.P
9	164	84		84/164	B.P
10	281	53		53/281	J.P
Observed By Lalan Yadav
1	345	6		6/345	B.P
2	170	12		12/170	J.P
3	175	5		5/175	B.P
4	084	12		12/084	J.P
5	164	5		5/164	B.P
6	265	70		70/265	J.P
7	276	60		60/276	J.P
8	068	36		36/068	J.P
9	255	32		32/255	B.P
10	256	69		69/256	J.P
Observed By Manishman Shakya
1	280	58		58/280	J.P
2	295	65		65/295	J.P
3	350	75		75/350	B.P
4	180	87		87/180	B.P
5	172	80		80/172	B.P
6	280	55		55/280	J.P
7	265	30		30/265	J.P
8	255	62		62/255	J.P
9	163	84		84/163	B.P
10	095	10		10/095	J.P

4. identification of rocks int the field:

4.1 Rock mass

In geology, rock is a naturally occurring aggregate of minerals and/or mineraloids. The Earth's lithosphere is made of rock. In general rocks are of three types, namely, igneous, sedimentary, and metamorphic. Petrology is the scientific study of rocks.

4.2 Classification of rocks

1. Sedimentary rocks:

The sedimentary rocks, as the name indicates, are those rocks which are derived from the consolidation of sediments of the preexisting rocks (igneous, sedimentary or metamorphic) under the influence of mechanical, chemical or organic activities of the denuding agents (i.e. wind, running water, glacier etc.)

The products of wear and tear of the rocks due to natural agencies like blowing wind, running water, percolating underground water etc when subjected, under favorable conditions to sedimentation and subsequent compaction results in the formation of rock masses due to pressure and temperature conditions which are known as the sedimentary rocks. Well known examples are sandstone, lime stone, shale etc.

2 Metamorphic rocks:

The rocks formed from the pre-existing rocks (igneous, sedimentary or metamorphic) by the processes of metamorphism (Greek, Meta=Change, morphe=form). It is a process by which existing rocks are modified under the influence of heat pressure or both

The ultimate product of metamorphism of already existing igneous, sedimentary or even metamorphic rocks incorporating temperature, pressure, stress, chemically active substances are called metamorphic rocks, e.g. Slate, Marble, Schist, Gneiss, Phyllite.

3 Igneous rocks

Primary or first formed rocks are called igneous (Latin, Ignis=Fire) rocks. It has been observed in deep wells, borings, mines, etc. that the temperature increases with the depth, generally there is an increase of 1^o C for every 40m. depth.

The consolidation of magma results in the formation of igneous rocks e.g. of igneous rocks are granite, rhyolite. The magma remains in the molten state; so long its physical and chemical environments remain unchanged. But whenever some changes (pressure, temperature etc) takes place; the magma no longer remains in molten state, but is changed into solid state called rock. Those rocks, which are formed directly by the solidification of magma on the earth's surface or below it, are called igneous rock.

4.3 Identification of rock in the field

Location no.L2

About 400m from the hanging bridge over the Trishuli River along Thopal Khola. Hanging bridge is about 100m from the Prithvi highway towards north and along the way of Thopal Khola. The study of River Channel Morphology had done in this location which is described later.

Location no.L3

About 200m from the hanging bridge over the Trishuli River along Thopal khola i.e. in between location L2 and the hanging bridge. Following things we observed in this location

1. Slate Rock

2. Unconformity

3. Limestone Rock

Slate Rock:

Description:

S.N.	Physical Properties
1	Sample number	01
2	Color	Grayish
3	Texture	Non crystalline
4	Structures	Foliation plane/slaty cleavage
5	Grain size	Fine
6	Sp. Gravity	Low to medium
7	Acid test	No reaction
8	Mineral comp.
9	Origin/rock type	Metamorphism
10	Engineering properties	Low strength, slightly weathered, slaty cleavage and soapy feel
11	Identification	Slate
12	Uses	Roofing, in electrical industry as switch board, bases and various turned or shaped parts due to its insulating property

v The attitude of this formation is,

Strike: E to W, N 33 E

Dip direction: 152

Dip amount: 86

Limestone Rock:

Description

S.N.	Physical Properties
1	Sample number	02
2	Color	White
3	Texture	Crystalline
4	Structures	Bedding plane
5	Grain size	Medium
6	Sp. Gravity	Medium to high
7	Acid test	Vigorously reacts with HCl
8	Mineral comp.	Calcite
9	Scratch test	Scratched by hammer
10	Origin/rock type	Sedimentary
11	Engineering properties	Porous, permeable
12	Identification	Limestone
13	Uses	Raw material for cement and sometimes in flooring

v The attitude of this formation is ,

Strike: N 70E to S 40 W

Dip direction: 2

Dip amount: 83

Location no.L4

Typical fold had observed in this location and is described later.

Location no.L5

Typical fold had observed in this location and is described later.

Location no.L6: Amphibolite

Amphibolite was found at this location.

Description

S.N.	Physical Properties
1	Sample number	03
2	Color	Dark green
3	Texture	Crystalline
4	Structures/cleavage	Foliation plane/slaty
5	Grain size	Fine to medium
6	Sp. Gravity	High
7	Acid test	No reaction
8	Mineral comp.	Horn blend
9	Origin/rock type	Metamorphism
10	Engineering properties	High strength
11	Identification	Amphibolite
12	Uses	Can be used as aggregates, dimension stone and other constructional applications

v Magma intrusion into the robang phyllite.

v Hard, gave metallic sound when hammered.

v Massive rock, couldn’t found any exact orientation.

Location no.L7

phyllite was found at this location.

Description:

S.N.	Physical Properties
1	Sample number	04
2	Color	Silver white
3	Texture	Crystalline
4	Structures/cleavage	Foliation plane/slaty
5	Grain size	Medium to coarse
6	Sp. Gravity	Low to medium
7	Acid test	No reaction
8	Mineral comp.
9	Origin/rock type	Metamorphic
10	Engineering properties	Low strength
11	Identification	Phyllite
12	Uses

v The attitude of this formation is

Strike: N 55E to S 55 W

Dip direction: S 35 E

Dip amount: 50

Location no.L8

Description

S.N.	Physical Properties
1	Sample number	05
2	Color	Dirty white
3	Texture	Crystaline
4	Structures/cleavage	Folliation plane/slaty
5	Grain size	Medium
6	Sp. Gravity	Medium
7	Acid test	No reaction
8	Mineral comp.	Quartz
9	Origin/rock type	Metamorphic
10	Engineering properties	High strength, durable
11	Identification	Quartzite
12	Uses	For making reeling in home applications, building stone, road metal, concrete aggregates

Location no.L9 “Schist”

Schist was found in this location.

Description

S.N.	Physical Properties
1	Sample number	06
2	Color	Silver white
3	Texture	Crystalline
4	Structures	Schistosity
5	Grain size	Fine to coarse
6	Sp. Gravity	Low to medium
7	Acid test	No reaction
8	Mineral comp.	Garnet, chlorite, quartz,hornblend,talc
9	Origin/rock type	Metamorphic
10	Engineering properties	Low strength, incompetent, harmful and undesirable rock
11	Identification	Schist
12	Uses	Rock foundation, building stone, aggregate for concrete, road material

Found right bank of malekhu about 3.5km south from Malekhu Bridge.

v The attitude of this formation is

Strike: N 75E to S 75 W

Dip direction: S 15 E

Dip amount: 75

Location no.L10: “Marble”

Marble was found in this location.

Description

S.N.	Physical Properties
1	Sample number	07
2	Color	White
3	Texture	Crystalline
4	Structures	Foliation plane
5	Grain size	Coarse
6	Sp. Gravity	Medium
7	Acid test	Vigorous
8	Mineral comp.	Calcite
9	Scratch test	Scratched by hammer
10	Origin/rock type	Metamorphic
11	Engineering properties	High strength, less porous, has rust due to iron of pyrite
12	Identification	Marble
13	Uses	As face works like flooring, wall panels, statue making, tabletops and other decorative works

Location no.L11: “Granite”

The boulder of granite was found in this location near location L1.

Description

S.N.	Physical Properties
1	Sample number	08
2	Color	White
3	Texture	Crystalline
4	Structures	Foliation plane
5	Grain size	Coarse
6	Sp. Gravity	Medium
7	Acid test	Vigorous
8	Mineral comp.	Most important is calcite and the others are olivine, garnet, graphite
9	Scratch test	Scratched by hammer
10	Origin/rock type	Metamorphic
11	Engineering properties	High strength
12	Identification	Granite
13	Uses	As aggregates, foundations in the construction and as slab

Location no.L12: “Gneiss”

Gneiss was found at this location just near the location1.

Description

S.N.	Physical Properties
1	Sample number	09
2	Color	White
3	Texture	Crystalline
4	Structures	Preferred orientation, gneisocity
5	Grain size	Coarse
6	Sp. Gravity	High
7	Acid test	No reaction
8	Mineral comp.	Quartz, plagioclase, biotite, muscovite
9	Origin/rock type	Metamorphic
10	Engineering properties	High strength, durable, non-porous, impermeable
11	Identification	Gneiss
12	Uses	as flooring mill and for building stone or material

Further:

v Bands of light and dark color minerals.

v Gneissocity is very high.

v Have weak planes.

v High shear strength.

v Perfect foliation plane.

Thus all three types of rock we had found at our field area. Mostly there were metamorphic rock and then sedimentary and lastly igneous. For civil engineers, only identification of rock is not sufficient. He or she should have an idea about the engineering significance of specific rock type. We all had learnt on this basis and partially we got it too.

5.0 GEOLOGY OF STUDY AREA

5.1 Location of study area

Malekhu lies on lesser Himalayan unit of Nepal. It has peculiar geological features within a small range of area. The Malekhu V.D.C. of Dhading district lies about 70 Kms south west of Kathmandu valley and is located at latitude of 27o 50' 38'' to 27o 45' 50'' and longitude of 24o49'5'' to 84o50' 50’’. It is situated on the bank of Trishuli and Malekhu river. The Trishuli river is running from the eastern direction to the western direction and the Malekhu river from south to north which mingles into the Trishuli river. Also, the Malekhu river has a tributary namely the Apakhola which meets the Malekhu river at a distance about 3 kms from the Malekhu bazzar. Climatically Malekhu is a sub-tropical zone. Mainly the rainfall is during the monsoon.

6.0 recognition of geological units:

Nepal lies at active tectonic region. Indian plate has been penetrating the Asian plate continuously. Due to this several thrusts were formed and forming till today .the Himalayas also formed due to tectonic activity.

There are mainly following thrusts.

1) Main central thrust

2) Main boundary thrust

3) Main frontal thrust

The Mahabharat range lies between mft and mbt. Similarly, siwalik range lies below mft. Our Study area lies between Kathmandu complex and nuwakot complex, both is the member of Mahabharat synclonyrium.

The study area starts from benighat slate, Maluku limestone, robang formation (robang phyllite with dunga quartzite) to raduwa formation ( garnetiferous shist). This is the boundary between nawakot and Kathmandu complex and known as Mahabharat thrust. Then we had found the formation named bhainsedovan marble.

6.1 Geological structures

Geological structure is the study of the permanent deformation and rock failure created by the changes in stress through geologic time. It is by far the most important aspect of geology for the engineer to understand. Tectonic processes are responsible for the many discontinuity planes (fractures, faults, joints) that permeate rock masses controlling their strength, stress-strain characteristics and the transmission and storage of fluids.

6.2 Phenomenon of geological structures

Phenomenon of structures may be conveniently subdivided into two groups:

Ø Brittle structures - recording the brittle-elastic failure of rocks in the past. Faults and joints fall in this broad category.

Ø Ductile structures - preserving the permanent viscoplastic deformation of rock throughout geologic time. Folds and metamorphic foliations are the expression of this type of structure.

6.3 Major geological structures:

During the course of trip to Malekhu area, we came across varieties of structure like joints, folds, fault, etc.

1. Joints

It is a fracture, which is relatively planer along which there has been little or no obvious displacement parallel to the plane. The joints were formed almost parallel, which are called a set of joints.

Almost at all location, we found the joints on the outcrop of the rock mass. It can be easily predict. And have great significance in engineering geology.

2. Folds

Folds are ductile deformation on the structure. They are the strata permanently deformed either by buckling or fracturing, if subjected to stress in a rock mass, and they cannot resist. Type of deformation depends upon mechanical properties of rocks and the nature of stress when applied slowly deep on the earth.

3. Fault

Fault is a rupture plane along which the opposite walls are moved each other. This movement may vary from a few cm to many km depending upon the magnitude and nature of the stress and the resistance offered by the rocks. The faults are also caused due to earthquake but it is still a complicated geological problem, which awaits satisfactory solution. Whether the earthquakes are caused due to faulting or faults are caused due to earthquake. The fault is occurred due to the plate movements, which creates the shear stress. The metamorphic form of gauge and breccia is called mylonite.

4. Unconformity:

An unconformity is a buried erosion surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval of time before deposition of the younger, but the term is used to describe any break in the sedimentary geologic record

v Disconformity

An unconformity between parallel layers of sedimentary rocks which represents a period of erosion or non-deposition. A paraconformity is a type of disconformity in which the separation is a simple bedding plane; i.e., there is no obvious buried erosional surface.(AGI, 366) A blended unconformity is a type of disconformity or nonconformity with no distinct separation plane or contact, sometimes consisting of soils, paleosols, or beds of pebbles derived from the underlying rock.

v Nonconformity

A nonconformity exists between sedimentary rocks and metamorphic or igneous rocks when the sedimentary rock lies above and was deposited on the pre-existing and eroded metamorphic or igneous rock.

v Angular Unconformity

Angular unconformity at Vallis Vale.

An unconformity where horizontally parallel strata of sedimentary rock are deposited on tilted and eroded layers that may be either vertical or at an angle to the overlying horizontal layers. The whole sequence may later be deformed and tilted by further orogenic activity.

v Paraconformity

An unconformity where beds above and below are parallel and no erosional surface is evident. Paraconformity can only be recognized based on the gap in the rock record when rocks of a particular age are absent from the sequence of rocks.

6.4 What kind of geological structures, we found at the area?

Location no- L4

A typical plunge fold was found at the left bank of malekhu khola just about 200m far from new Malekhu Bridge.

Description:

v Brown colored rock with plunging fold.

v Plastic and ductile deformation.

v Asymmetric fold.

v Affected by physical weathering.

v Hard in hammering.

One should have an idea about the engineering significance of folds.

Some of these are:

1. Repetition of beds may give a surprise to an engineer.

2. Shattering in rocks causing permeability contrast and loss in strength.

3. The crest and trough have reasonably low strength than other part.

4. Folds are more sensitive in tunneling.

Location no- L5

At this location, we have found an example of fault. The location lies about 300m from Malekhu Bridge. It consists of fault breccia and fault gauge. Fault breccia is the crushed and angular fragments .it was embedded and cemented on the fault gauge. Gauge was pulverized clay like powdered rock mineral. It was occurred at the base of the faulted zone. it was formed due to the strong rubbing action on the rocks during the faulting process.

Engineering considerations of the fault:

· The shear zone and fault zone serve as easy pathways to water, which can cause leakage in dam construction.

· The faulted rock is very weak in strength and can’t be suitable for foundation.

· Once the shear zones become reaching in water, slippage is highly facilitated.

Location no- L9

The location where the garnet ferrous schist was found, we also met the major thrust zone named as mahabarat thrust. Thrusts are reverse faults and commonly dominate the structure of collision mountain belts. Some thrusts have moved a long way - many mountain belts have thrusts that have moved many tens of kilometers.

Once upon a time, the top of mt.everest lies at the bottom of the Tethis Sea. It has been raised due to thrust resulting by tectonic activities.

The picture below is of the area from where the mahabharat thrust passes. It was identified by the dipping of the boundary rock .it separates the nawakot complex with Kathmandu nappe.

Besides these major geological structures, we also found some deformation structures like:

Veins:

Joints filled my filler material. sometimes, the strength of filler material is more than the parent material.

Lenses:

Same as veins, only difference in shape. It looked like an optical lens.

Boudinage:

Variation in width of vein.

Tension gases:

Deformation structures due to shear stress in the mass.

6.5 Engineering significance of the geological structures

The most striking features of rocks as engineering materials is that they are not simple, isotropic, elastic and continuous but very complex, strongly anisotropic, inelastic discontinuous. It is virtually impossible to deduce the stress history of rocks from their observed deformation. There are always many ambiguous deformation paths that could have been followed to produce what is observed.

7. study o river channel morphology:

7.1 What is river channel morphology?

Appearance of river channel and the study of its external feature are known as morphology of river channel. In most cases the tendency of river is to flow towards the sea. The highland or the mountainous regions from where the river originates is called its head region. From the head region, the river flows through gradually decreasing slopes and then through almost flat lands before it actually empties into the sea. The place where a stream or river empties into the sea is called its mouth.

7.2 Types of river channel morphology

1) Straight river channel

This kind of river channel has its flow of water in straight form. This is mostly possible in hard rocks. Presence of fault changes the course of flow of river channel. From head to mouth, a river may exhibit a variety of geological activity. This is head region; it flows with roaring speeds acquiring energy by virtue of which it is capable of cutting down even the hardest rocks along and across its course.

In this type of river channel, deposition is not possible. It is associated only with erosion. The gradient of straight river channel is quite high and discharge is quite low.

2) Meandering River Channel

River channel in which the course of the river is bent towards different direction within small area is known as meandering of river. It mostly possible in soft rocks. In middle reaches, the river becomes mature. It has already acquired some load to carry down and the capacity to cut vigorously is gone. It does erode but only selectively, changing its course where it finds obstructions, which are insurmountable. It meanders profusely, i.e. changes its course again and again through a small area. It flows in loops. Menders are therefore typical character feature of a mature river. The gradient of meandering river channel is quite low which increases the possibility of meandering. The discharge is quite high which also contributes to meandering of a river. In this type of river channel, erosion and deposition are frequent and approximately equal.

3) Braided River Channel

Rivers, in which flow of water is along different channel within the same river, are said to have braided river channels. This type of river channel is generally present in the flat lands near its mouth. Amount of discharge varies accordingly to the season in such river channel. Braided river channel account for more deposition and less erosion i.e. depositions predominant over erosion.

7.3 What factor erosion and deposition depends?

Erosion depends upon:

Velocity

v The gradient of the channel

v The volume of water in the stream

v The nature of the channel (whether rough or smooth)

v The load of sediment in the stream at a given point of time.

Lithology

The nature of rock along the riverbed and sides also can affect the rate of erosion. Some types of rocks are more easily eroded by stream water than the other exactly identical eroding conditions. Thus, of a limestone and sandstone forming bedrock of a stream and lying side by side (at the same gradient), limestone will suffer erosion at a higher rate compared to sandstone. This is because limestone has a lower hardness and a chemical composition favorable for solvent action of water.

Load

If a stream is fully loaded i.e. it is incapable of taking any further load, then the tendency to erode the rocks of the channel will be correspondingly reduced. Its major power is used in transporting load on the contrary an unloaded stream can erode the rocks more effectively.

Deposition is due to, energy, environment, and time

7.4 Engineering significance of river channel morphology

Ø Alluvial Fans and Cones

These are cone shaped accumulation of stream debris that is commonly found at places where small intermittent streamlets coming down from hills enter the low lands. The apex of such a deposit points up hill and its slope may range from almost flat to as much as 50. When the slope of the deposits is below 10, the alluvial deposit is known as alluvial fan, and when it is from 10-50, the deposit is known as alluvial cone. Alluvial fans and cones show contrasting patterns in distribution of fragments and particles of various sizes at their apices, peripheries and in the main body. Further repeated accumulations over an initial fan or cone contribute to its considerable growth. Alluvium is usually very porous and will be compressible if rich in clay and permeable if composed of gravel, sand or silt.

Ø Flood Plain Deposits

Floodwaters are invariably heavily loaded with sediments of all types. When these waters overflow the banks and spread as enormous sheets of water in surrounding areas, their velocity gets checked everywhere due to obstructions. As a consequence they deposit most of the load in the form of a thick layer of mud, so commonly seen after major flood. Since such a process may get repeated year after year, the low lying areas surrounding major rivers are actually made up of the layers of mud deposits laid after a number of floods. These are generally level or plain in nature and extensive in area and are called Flood plains. All the plain around major rivers are actually flood plains. These are invariably very fertile in nature and hence have been supporting population. Two major types of flood plains known as convex flood plains and flat flood plains are known.

Ø Deltas

Deltas are defined as alluvial deposits of roughly triangular shape that are deposited by the rivers at the points where they enter into the sea. Herodotus first used this term for the deposits of the river Nile at its entry into the Mediterranean Sea. Deltas are very complex in their structure. A number of fractures are involved in their formation, evolution and modification.

Ø Oxbow lake:

The isolated curve or loop shaped part of meandering river often contains some supplies of water known as oxbow lakes.

8.0 ENGINEERING GEOLOGICAL STUDY OF THE rock outcrop:

8.1 Engineering geological data

There are some factors whose condition in case of rock are observed and recorded in order to determine the age of the rock is simply known as engineering geological data. These data also helps us to determine the present condition and the nature of the rock.

8.2 Importance of engineering geological data:

Purpose specific geological data collected from field (rock mass) which can be quantified and used as design parameter. It is quantities diagnosis of an area. It must be purpose specific. Site investigation is the investigation of particular area for specific purpose data collection. It is very essential to draw any engineering geological map or to solve any geological problems.

We always deal with a rock mass not only with a block of rock. Rock mass means intact rock with its discontinuities. In many cases, the technicians are in dark in this aspect. He or she collect a piece of sample and take it to the lab and conclude his/her result. This is not a correct way to publish any geological decision. In fact, it is much more important to know the entire rock mass up to our concern.

8.3 Parameters of engineering geological data

v Rock type:

1. Sedimentary

2. Igneous

3. metamorphic

v Rock strength

1. High

2. Medium

3. Low

v Weathering grade

1. Fresh weather (w₀)

2. Slightly weathered (w₁)

3. Moderately weathered (w₂)

4. Highly weathered (w₃)

5. Completely weathered (w₄)

6. Residual soil (w₅)

v Rock Quality Designation (R.Q.D)

It is expressed in percentage. The expression for RQD has is:

RQD=115-3.3*J_v

Where J_v = Joint volume. I.e. number of joint per unit volume.

v Spacing of discontinuity

It is expressed in cm and all the discontinuity is taken under considered area.

v Aperture or separation of discontinuity

1. Tight (<.1cm)

2. Open (expressed in cm, all the data are taken)

3. Wide (>30cm)

v Infilling materials

v Persistence

v Roughess of discontinuity

1. Smooth

2. Rough

3. Undulated

v Number of joint set

v Orientation of joint set

Expressed including dip amount and dip direction, (i.e. dip amt/dip dir)

v Ground water condition

1. Dry

2. Dripping

3. Seepage

4. Flowing

5. Damp/wet

8.4 Geological engineering data in the field

S.N.	Parameters	Properties	Remarks
1	Rock type	Sedimentary
2	Rock strength	High
3	Weathering	W1
4	R.Q.D. test	62.2
5	Spacing of discontinuity	5.5,2.5,23.5,6.8,3.5,10	In cm
6	Aperture of discontinuity	tight
7	Infilling materials	Calcareous
8	Persistence	90%
9	Roughness of continuity	Rough
10	No. of joint set	3
11	Orientation of joint set	83/165, 5/251, 19/65
12	Ground water condition	Dry

S.N.	Parameters	Properties	Remarks
1	Rock type	Sedimentary
2	Rock strength	Medium
3	Weathering	W2
4	R.Q.D. test	82
5	Spacing of discontinuity	9,10,6,3.5,12.5,6	In cm
6	Aperture of discontinuity	Tight
7	Infilling materials	Clay
8	Persistence	95%
9	Roughness of continuity	Smooth
10	No. of joint set	3
11	Orientation of joint set	80/162,24/72,56/77
12	Ground water condition	dry

S.N.	Parameters	Properties	Remarks
1	Rock type	Sedimentary
2	Rock strength	High
3	Weathering	W1
4	R.Q.D. test	75.4
5	Spacing of discontinuity	16,15,9,14,9,3,5,10,7	In cm
6	Aperture of discontinuity	Wide
7	Infilling materials	Clay
8	Persistence	90%
9	Roughness of continuity	Smooth
10	No. of joint set	3
11	Orientation of joint set	83/189,88/267,8/082
12	Ground water condition	dry

S.N.	Parameters	Properties	Remarks
1	Rock type	Sedimentary
2	Rock strength	High
3	Weathering	W1
4	R.Q.D. test	82
5	Spacing of discontinuity	15.65,13.2	In cm.
6	Aperture of discontinuity	Tight
7	Infilling materials	Clay and sand
8	Persistence	50%
9	Roughness of continuity	Smooth
10	No. of joint set	3
11	Orientation of joint set	36/265,84/305,70/269
12	Ground water condition	Dry

S.N.	Parameters	Properties	Remarks
1	Rock type	Sedimentary
2	Rock strength	High
3	Weathering	W1
4	R.Q.D. test	83
5	Spacing of discontinuity	3,5.9,2,8,4.6,12	In cm.
6	Aperture of discontinuity	Tight
7	Infilling materials	Clay
8	Persistence	70%
9	Roughness of continuity	Smooth
10	No. of joint set	3
11	Orientation of joint set	83/189,88/267,8/082
12	Ground water condition	Dry

9.0 ROCK MASS:

9.1 The objectives of rock mass classifications are to:

Ø Identify the most significant parameters influencing the behaviour of a rock mass.

Ø Divide a particular rock mass formulation into groups of similar behaviour – rock mass classes of varying quality.

Ø Provide a basis of understanding the characteristics of each rock mass class

Ø Relate the experience of rock conditions at one site to the conditions and experience encountered at others

Ø Derive quantitative data and guidelines for engineering design

Provide common basis for communication between engineers and geologists

9.2 Engineering significance of rock mass classifications:

Ø Improving the quality of site investigations by calling for the minimum input data as classification parameters.

Ø Providing quantitative information for design purposes.

Ø Enabling better engineering judgment and more effective communication on a project.

9.3What is rock mapping?

The main purpose of the rock mapping for much of its history has been reconnaissance mapping of large regions whose geology was essentially unknown. Conclusively Rock mapping (geologic maps) is the plotting of target formations and terrains on maps or aerial photographs for later compilation.

9.4 How it can be done?

9.4.1 Stereo photography

Stereo photography is the practice of having successive [aerial] photographs overlaps the next by 55%-60%. This pair (known as a stereo pair) is used with either a stereo viewer, stereo plotter, or digitized for use with soft-copy stereo programs to view the desired area in three dimension (3-D). The stereo photography helps effectively in rock mapping by providing clear 3D image of the rock. Dip direction, dip amount and strike can be found from the photograph. About 1km north from richoktar, two photographs of the rocky outcrop were taken simultaneously from the same point at a distance.

9.4.2 Grid survey

The mapping technique is just based on the plotting the points on square blocked sheet. A grid of reasonable scale has to make first than the attitude of the foliation and bedding can be plotted in the grid. And lastly, the respective points are joined.

9.4.3 Scan line survey

Scan line survey is a sampling technique whereby information is detailed along a single pass of the recording device. The process is repeated at intervals to cover the desired area. Scan Line Survey is mostly used in engineering structure. The discontinuities, which impart the loss of strength of the rock, are found out by this method. This survey is carried out on the road alignment before its construction. The rocky outcrop has been surveyed for the different structural feature of the rock mass. The total span of the survey was carried out within 10 meters at the level of the road and 2 meters high from it.

10.0 conclusions:

At last we had concluded the malekhu and its surrounding is the answer for geological curiosity. Actually, the malekhu is small in area but it has large amount or numbers of the geological phenomenon and hence it can provide broad knowledge for the learners.

Along the Malekhu River, we found sedimentary rock and gradually metamorphosed from phyllite to crystalline schist and along the way to Dhading, it gradually metamorphosed to lime stone to phyllite and then to slate.

Every major bed was dipped in north direction. This proved the tectonic movement along the way from south to north.

Besides this, we have learnt different methods of geological data collection measures and the way, how rock mapping is done.

Handling the compass and to measure the attitude of rock outcrop is now very easy to us.

By, the river channel morphology we knew that, how the river flows, what are the factors affecting erosion and deposition and how it occurs.

Really ...........beyond expectation! We do salute to our respective teachers again!!

REFERENCES:

v Data collected during the field visit

v Sketches drawn and photo taken in the field

v http://www.geocities.com/s_m_s_2002/geoall.html

v http://www.geocities.com/razesh55/geotour.htm

v http://www.google.com.np/

v http://www.geology.edu.np

v Engineering Geology:

By Prakash Chandra Ghimire

Mahesh Singh Dhar

v A Text Book of Engineering Geology

v Recent Publications related to the subject matters and other sites.