Gelogical Risk Analysis of Arniko Highway Sector-4 (

GELOGICAL RISK ANALYSIS OF ARNIKO HIGHWAY SECTOR-4

(BARHABISE-TATOPANI)DHIRA PHADERA

DIPENDRA GAUTAMMADAN KHAKURELNIRAJ RAJ THAPA

KHWOPA ENGINEERING COLLEGE, DEPT. OF CIVIL ENGINEERING BATCH 2008.

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GEOLOGY OF NEPAL HIMALAYA

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GEOLOGY OF NEPAL HIMALAYA (contd…)

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GENERAL GEOLOGY OF NEPAL HIMALAYA (contd…)

• Greater Himalaya extends about 2500 Km• 230-320 Km in width and bounded between

the Indogangetic plain in the south and Tibetan Plateau in the north.

• Nepal Himalaya occupies almost 1/3 rd part of the Himalaya.

• Divided into 5 distinct morpho-geotectonic zones.

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GENERAL GEOLOGY OF NEPAL HIMALAYA (contd..)

• These 5 zones are identified by morphological, geological and tectonic features.

• Indogangetic Plain ()• Siwalik Hills (MFT-MBT)• Lesser Himalaya (MBT-MCT)• Higher Himalaya (MCT-STDFS)• Inner Himalaya (STDFS-Tsangpo Suture Zone)

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GEOMORPHOLOGY OF ARNIKO HIGHWAY

• Passes through the middle mountains of the Nepal Himalaya.

• Starts from Kathmandu (1300m).• Crosses small hillock at Sanga, the road enters

into Banepa valley.• Passes through the hill from Dhulikhel and

descends down to Panchkhal valley.• Panchkhal valley comprises deeply weathered

Lateritic red clay.

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GEOMORPHOLOGY OF ARNIKO HIGHWAY (contd..)

• Dolalghat bridge site is the lowest point of the Highway.

• Arniko highway terminates at Friendship bridge at the height of 1720m.

• Highway passes through the bank of Sunkoshi and Bhotekoshi river.

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GEOLOGY ALONG THE ARNIKO HIGHWAY

• Passes through the lesser Himalayan metasediments, central crystalline and quaternery deposits of Kathmandu, Banepa and Pachkhal valley.

• The rocks of Bhimphedi group of Kathmandu complex are exposed between Sanga Bhanjyang and south of Tatopani.

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GEOLOGY ALONG THE ARNIKO HIGHWAY (contd..)

Lesser Himalayan metasediments: (Stocklin, 1981)

-Nuwakot complex - Kathmandu complexNuwakot complex: - Lower Nuwakot group - Upper Nuwakot group

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GEOLOGY ALONG THE ARNIKO HIGHWAY (contd..)

• Kathmandu complex:• 1. Bhimphedi group• 2. Phulchoki group• It is found that the grade of metamorphism

gradually decreasing upward with the least effects of metamorphism in the upper most Tistung formation, which consists of phyllites, meta-sandstones and minor limestones.

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GEOLOGY ALONG THE ARNIKO HIGHWAY (contd..)

• In between Bhimphedi group and Upper Nuwakot group Mahabharat Thrust passes.

• Kathmandu valley filled with fluvio-lacustrine sediments of quaternary age.

• The sequence of slightly consolidated fluvio-lacustrine sediments of up to 600m thickness, consists of peat, clay, sand and gravel.

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GEOLOGY ALONG THE ARNIKO HIGHWAY (contd..)

• Kathmandu-Sanga sector of highway consists the youngest rocks of Bhimphedi group i.e. Tistung Formation, consisting of fine clastic sequence of metasandstones, phyllites and sandy limestone.

• Panchkhal valley is filled with alluvial and partly lacustrine deposits. Red clay is developed in its northern sides.

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GEOLOGY ALONG THE ARNIKO HIGHWAY (contd..)

• Mahabharat Thrust Sector: Panchkhal-Cha Khola fault.

• Rocks of Bhimphedi groups are exposed in this sector.

• Indrawati Fault Sector: Dark argillaceous slates/phyllites containing frequent intercalations of carbonaceous slates.

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GEOLOGY ALONG THE ARNIKO HIGHWAY (contd..)

• MCT sector:• Phyllites, phyllitic metasandstones, gritty

phyllites and fine conglomerate of light grey colour.

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NATURAL HAZARDS OF ARNIKO HIGHWAY

• Slope instability.• Improper road cutting in soft and highly

weathered rock• Tectonic activity (fault/thrust, frequent rock

fall/landslides during monsoon)• Cutting by the rivers• Flash floods

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GEOLOGY ALONG THE ARNIKO HIGHWAY (contd..)

• Debris flow• GLOF (Glacial lake outburst flood)- in

Bhotekoshi in 1964 and 1981• In 1987 due to intense precipitation flood

occurred in Sunkoshi river resulting the damage of diversion and power house of Sunkoshi Hydropower.

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ARNIKO HIGHWAY

• Length : 115 Km• Strategic road network connecting China• Passes through fragile geology of Nepal

Himalaya.• Sector-4 (Barhabise-Tatopani)- 28 Km.• Frequently suffered from natural geotectonic

phenomena.• Passes through highly landslide prone areas.

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ARNIKO HIGHWAY (Sunkoshi Hydropower)

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Debris flow

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Fissures in Highway

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Landslide and surface scouring

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Debris flow due to intense precipitation

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The eroded road surface

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Subduction of road pavement due to landslide as a result of stone quarrying

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Landslide overcoming the gabion

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Rock slope failure

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The alluvial deposit after landslide

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The eroded road due to landslide

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Boulders along with debris

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The gabion wall destroyed due to debris

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The slide of gabion wall due to surcharge mass from u/s

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Boulders and alluvial deposits besides highway

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Road subsidence

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Landside obstruction

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Alluvial deposit and gully erosion

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Waterway on the road surface

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Metamorphic rock exposure

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Toppling failure test (Attitude of rock)

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Exposure of metamorphic rock

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Toppled rocks on road

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Metamorphic rocks thickly bedded

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Boulders from the loose bedding of Metamorphic rock

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Toppling failure blocking the road

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Eroded bridge with settlement

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Landslide destruction of road

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Landslide and rock mass failure

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Landslide obstruction and clearance

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Rock mass failure

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Slide of mass and roadside obstruction

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Gully erosion along with debris

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Illegal stone quarrying and rock mass failure

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Surface run off accompanied by landslide

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700 m long landslide

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Slide and landslide

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Rock mass failure obstructing road

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Landslide

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Connecting road construction causing the landslide

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The existing culvert and new bridge under construction

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Gully erosion

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The landslide entered to human settlement and destroying road

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Debris flow

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The causeway damage due to scouring

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The destruction of gabion

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Landslide

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Surface runoff eroding the road

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Boulder along with slide

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Failure due to unconfirmity

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Friendship Bridge

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INSTABILITIES AT A GLANCES.N. Instability criteria No. encountered

1. Gully erosion 3

2. Debris flow 8

3. Hill slope failure 3

4. Cause subsidence 5

5. Road subsidence 12

6. Landslide 18

.7 Slide 8

8. Culvert subsidence 2

9. Slope failure 1

10. Masonry wall failure 1

11. Toppling failure 1

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SCOPE OF CASE STUDY

• Reassessment of the condition of the damaged site.

• Bioengineering planning for landslide prone areas.

• Landslide susceptibility analysis.• Recommendation of preventive measures and

design of suitable structures.

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FUTURE WORKS

• Technical paper on geological hazard analysis of Arniko Highway Sector-4

• Technical paper on Hydrological risk analysis of Arniko Highway sector-4.

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• THANK YOU