Nepal is a mountainous country. Since the Himalayan range is a result of collision of Tibetan and Indian plates, the zone is the most active tectonic zone. The area is widely known for its complex structural deformation. Due to this, Nepal is suffering from different types of geo-hazards and instabilities. The rapid construction of infrastructure such as roads, irrigation, cannels and dams, tunnels, without due relating geology and engineering may cause the failure of such infrastructures. So, civil engineering students must have the knowledge of geology for planning, investigating and constructing.

We have completed this report, which entitled “GEOLOGICAL FIELD TRIP” which is based on practical knowledge on geology. We would like to express our sincere gratitude to Mr. Basanta Devkota for his guidance and invaluable suggestions.

Finally, we are thankful for the geological field trip conducted   under Institute of engineering by Sagarmatha Engineering College.

For Civil Engineering students, the geological field trip had made aware about different aspects of geography. Being the students of Civil Engineering, we are carrying on our report entitled “Geological field trip.” This actually uplifts the creativity of the students and helps to gain some practical knowledge on the matter on field. It’s great pleasure to express our sincere gratitude to our respected teacher Mr. Basanta Devkota, for his enthusiastic support, guidance and confidence towards us. His valuable suggestions helped greatly on gaining knowledge and completing the report successfully. We are grateful for his remarkable suggestions and encouragements and for his excellent guidance and helping us to focus our aims towards the proper direction on achieving the proper knowledge on geography.

Finally we are grateful of having such a cooperative company .Every attempt has been made to make this report as informative, compact, and to the point as far as possible. Lastly, we would like to appreciate for any suggestions and comments regarding to the report that may be helpful to raise our confidence and knowledge.                            

Geology is the study of the earth, its history, its exterior as well as interior, and the processes that act upon it. Geology is an important way of understanding the world around us, and it enables scientists and geologists to predict how our planet behaves. So, study of geology is carried out to try to understand the natural hazards and forecast potential geologic events, such as volcanic eruptions or earthquakes.

  The geological field visit to Malekhu was organized by the Department of Geology under Institute Of Engineering, 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 two days 3rd Feb and 4th Feb was spent in geological field study in Malekhu, 75 Km. North West from Kathmandu

The main objective of the geological field trip was to learn the basic geotechnical skills in civil engineering regarding mass movement, site investigation, landslide and construction material. The basic objectives of field visit are:

Ø Study of mass movement and its control measures.

Ø Study of site selection for construction material.

Ø Study of rock failure condition.

Ø Study of geological condition around dam site and tunnel alignment.

Ø Study of rock mass and its classification by RMR system

Ø Preparation of engineering geological map.

Disintegrated and fragmented rock materials due to mechanism of weathering processes (mechanical, chemical And Biological) are called rock wastes. Generally movement of rock waste unlocks down the hill slope is called mass movement of rock west or simply mass movement.

Any sort of mass movement of weathered  debris with any rate whether on hill slope or valley side  depends on the ratio between shearing forces(stress) and resistance of materials to shearing forces (shearing resistance of materials) as follows.

       Fs=   Shearing resistance of materials

                 Magnitude of shearing force

Where, Fs= Factor of Safety

For, Fs=1           Equilibrium condition

     <!–[if gte msEquation 12]>      ><![endif]–>1       Stable

          <!–[if gte msEquation 12]><<![endif]–>1        Unstable i.e. mass movement occurs

Ä Water when gets collected in pores, the more stress is increased due to weight as well as shearing strength of material get decreased which cause the mass movement.

Ä Transitory states such as earthquake.

Ä Toe cutting –bank cutting on the river.

Ä Artificial structure on sloppy area cause different types of failure.

Depending upon movement; mass movement area of three types,

(i)Slope failure (ii) Landslide (III) Debris flow

The Slope failure is the movement of weathered surface oil layer /rock of steep slope in small dimension and rapid movement .In this there may be absence of slip surface. The main cause of this type of failure is steep slopes, loose soil, and excavation of rock or soil on downhill side.

It is movement of deposited or eroded sediments along the stream. Debris flow involves down slope movement of enormous amount of viscous soils and boulders either separately or mixed together and occurs mostly along river valley sides. The differences between debris flow, earth flow and mud flow is

related to size of particles and amount of water. The size of particles decreases from be debris flow to mud flow. Debris flow have 20-80<!–[if gte msEquation 12]>%<![endif]–> practicles coarser than sand sizes, where as earth flows and mud flows are 80 percent or more mud and sand. Earth flow is promoted by excessive water received mostly through rainfall so the materials are oversaturated. They are more common on planar hillsides or valley sides having alluvium, rich in clay minerals.

  The landslide is defined as the down slope transport of mass of soil and rock material along a slip surface under the influence of gravitational force. Landslide can be also defined as a type of mass movement which has a clear sliding surface with large dimension, occurs in gentle slope and moves slowly and continuously basically due to the influence of water and gravity.

They are abrupt movement of the slope that separates from steep slopes and cliffs, the movements occur due to free fall or bouncing. Depending upon the type of materials  involve, it may be called rock fall, and soil or earth fall ,debris fall.

Table:-Classification of landslides( after Vasner ,1978)

They are blocks of rock that tilt or rotate forward on a pivot or hinge and then separate from the main mass, fall on the slope, and subsequently bounce and roll down the slope.

There are movements caused by finite shear failure along one or more surface of rupture which are visible or whose presence can be inferred. The two principal types of slide are rotational and translational.

These slides refer to failure involving sliding movement on the circular or near circular surface of failure.

These are non-rotational block slides involving mass movements on more or less plans surface. The movement of a translational slide is controlled by weak surface such as bedding, joints, foliation, faults and shear Jones.

These Failure are caused by liquefaction where by saturated, loose, cohesion less sediments are trans formed into a liquid state. Rapid ground motions such as those caused by earthquake are responsible for this phenomenon.

Flows are rapid movements of materials as a viscous mass where inter-granular  movements of predominate over shear surface movements.

These are slide in which the failure occurs due to a combination of above type of movements.

Ä Effect of landslide is not occur where massive and non-porous igneous rocks are found.

Ä Rock developed with bedding and foliation plain are week in nature which is directly  affected by water which cause landslide.

Ä It reduces the strength of rocks.

Ä Physical weathering  cause the creation of loose surface and direct effect of water reduce it’s strength and hence tends to the result of landslide.

Ä Chemical  weathering cause the rock material convert into the clay material which is very prone to landslide.

Ä Joint, fault, fold are very weak zone causing the less strength of rock.

Ä Water enter through the crack cause the shearing strength decreased and hence landslide occurs.

Ä Properties related to conductivity, resistivity, porosity, permeability, Etc.

Ä Highly porous material vulnerable to landslide.

 Ground water Movement:-

Ä Due to movement of groundwater pore water pressure exerted causing the shearing strength less and cause landslide.

Ä In geological terms it is rainfall and major causative factor for landslide.

Ä Cause the bank cutting whereas material saturated by water and very weak to resist landslide.

Ä Due to increase in slopes materials become unstable and may cause landslide.

 Vegetation:-

Ä Sometime vegetation done unscientifically may cause landslide because roots beneath the earth surface may cause development of cracks and on slopy area load also may increase.

Ä Wind blow may cause tall tree shakes and loosen the soil surfaces,.

Ä Long shaking on earth surface may cause distracts in strength of materials.

Ä High magnitude of earthquake is always prone to everything.

 Retaining walls are relatively rigid walls used for supporting the soil mass laterally so that soil can be retained at different levels on two sides.

made by filling stones on wire net

  Stone masonry wall:-

made by joining stones by cement.

     Concrete masonry wall:-

            made by mixtures of aggregates and cement

These are applied to resist the thrust of sliding soil mass directly and prevent small scale landslide.

Steel pile of 200-600mm is driven through the sliding surface to control landslide movements directly. this is used in very urgent and importance locations. Piles are installed from the center to the lower part of landslide blocks. It reinforced the ground mass and prevent from sliding.

It is applied to prevent a landslide through the tensile strength  of steel wire or bar, which anchor the sliding  soil mass to bedrock.

To drain out the water which helps the water not to be collected in pores.

Perforated pipes are wrapped by geo texture  material allowing only water to pass out but not soil or rock materials.

It is drilled up to their where the effect of ground water is present.

The soil removal after trimming of slope is main function for correction. Sliding force can be reduced through the partial or entire removal   of the sliding mass from the crown side of landslide mass.

Initial stage of landslide is erosion so it must be controlled. Different type of structured made on river and sloppy area to control measure.

Ä U-shaped dam are made to reduced the velocity of water.

Ä To control the gully erosion

Ä To control the sediments carried by water

Ä Series of single wall are made across the bank of river called spur.

Ä Wall made along the bank of river called dike.

Ä Steps like structure are made on sloppy area to control the velocity of water and to drain out.

Combination of civil structure and vegetation to stabilize the slope and the best techniques for slope stabilizing.

The function of civil structures to stabilize the slope

(A)Catch:- to catch the unstable material

(B)Armour:-to cover the unstable part

(C)Anchor:- to join the unstable and stable portion

(D)Reinforce:-To increase the strength 

(E)Support:-to provide support on slope

(F)Drain:-To properly draining out the water

These all functions must be fulfilled by civil structure. Vegetation also done all these functions. So, proper and scientific vegetation is very importance in bio-Engineering.

Rock mass classification systems are used for various engineering design and stability analysis. These are based on empirical relations between rock mass parameters and engineering applications, such as tunnels, slopes, foundations, and excavatability. The first rock mass classification system in geotechnical engineering was proposed in 1946 for tunnels with steel set support.

The Rock Mass Rating (RMR) System is a geo-mechanical classification system for rocks, developed by Z. T. Bieniawski between 1972 and 1973. It combines the most significant geologic parameters of influence and represents them with one overall comprehensive index of rock mass quality, which is used for the design and construction of excavations in rock, such as tunnels, mines, slopes and foundations

Slope failures are major natural hazards that occur in many areas throughout the world. Slopes expose two or more free surfaces because of geometry. Plane, wedge, toppling, rock fall and rotational (circular/non-circular) types of failure are common in slopes (Figure 1). The first four are more predominant in rock slopes and are primarily controlled by the orientation and the spacing of discontinuities planes with respect to the slope face. The pattern of the discontinuities may be comprised of a single discontinuity, or a pair of discontinuities that intersect each other, or a combination of multiple discontinuities that are linked together to form a failure mode. The types of slope failure are primarily controlled by material properties, water content and foundation strength.

A rock slope undergoes this mode of failure when combinations of discontinuities in the rock mass form blocks or wedges within the rock which are free to move. The pattern of the discontinuities may be comprised of a single discontinuity or a pair of discontinuities that intersect each other, or a combination of multiple discontinuities that are linked together to form a failure mode.

A tunnel project must start with a comprehensive investigation of ground conditions by collecting samples from boreholes and by other geophysical techniques. An informed choice can then be made of machinery and methods for excavation and ground support, which will reduce the risk of encountering unforeseen ground conditions. In planning the route the horizontal and vertical alignments will make use of the best ground and water conditions.

Tunnels are dug in types of materials varying from soft clay to hard rock. The method of tunnel construction depends on such factors as the ground conditions, the ground water conditions, the length and diameter of the tunnel drive, the depth of the tunnel, the logistics of supporting the tunnel excavation, the final use and shape of the tunnel and appropriate risk management.

There are three basic types of tunnel construction in common use:

·        Hard rocks like granite, gneiss, quartzite, etc. is favorable than weak rocks like slate, phyllite, etc.

·        Horizontal or slightly dipping rocks with the strike parallel to the axis of the tunnel.

·        Steeply dipping formations with the strike perpendicular to the axis of the tunnel.

·        Anticline is favorable.

·        Tunnel is faulted and sheared zone is very unfavorable.

·        Joints in general play very negative role.

·        Large quantity of water flow is very unfavorable; this problem arises when the tunnel is located below the water table.

·        Tunnel entrance should be free from any type of instability.