SEMINAR REPORT

ON

VARUNAVAT PARVAT LANDSLIDE

GUIDE- SUBMITTED BY-

Miss BHARTI SAINI ANUJ DHYANI SEC-A ROLL NO. 25 VII SEM CIVIL ENGINEERING

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I. CERTIFICATE

This is to certify that Mr. Anuj Dhyani of B.Tech VII sem, Civil engineering has successfully completed his term work in seminar report presentation for the session 2011-12 , under the guidance of Miss Bharti Saini . The report submitted by her is in accordance with the technical requirements and fulfills all the necessary criteria.

(Seminar co-ordinator) (Head of Department)

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II. ACKNOWLEDGEMENT

I am taking up this opportunity to acknowledge the support of all those people who played a vital part in the completion of this report. My first sincere regards are for the Chairman Sir of our University, Mr. Kamal Ghansala and my respected HOD Sir, Mr. K.K Gupta for providing me a platform to perform. I sincerely appreciate the help which I got from my seminar co-ordinator, Miss Bharti Saini, who helped me right through the beginning .I would also like to thank my friends for supporting me through various phases and keeping me in high spirits against all odds.

ANUJ DHYANI

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III. ABSTRACT

A landslide is a complex dynamic system. An individual ‘landslide’ characteristically involves many different processes operating together, often with differing intensity during successive years. A landslide that struck the hill of the Varunavat on 23 September 2003 and endangered theUttarkashi township is a living example.

At the foot of the parvat lies the Uttarkashi township. Uttarkashi township, located on the right bank of the Bhagirathi river, is known to have had a history of natural disasters, including the mass movement activities. A disastrous landslide in the area on the slopes of theVarunavat Parvat struck late in the night on 23 September 2003, immediately after the rainy season. Both natural and human-induced factors are responsible for this slide, however, the main triggering factor is the surface and groundwater.

The main treatment works of the Varunavat Parvat landslide area have been completed in 2008 and it is worth highlighting that there is no sliding from the treated parts for the last three years, despite unusually high rain fall (maximum in the last three decades) in Uttarakhand in the year 2010. The contribution of GSI in the for warning of Varunavat Parvat landslide hasbeen duly reflected in the Press Release of Ministry of Mines, Govt. of India dated 12.01.2005 (copy enclosed) which itself is the testimony to the importance of the role which GSI, Uttarakhand Unit, Dehradun has played in the treatment of Varunavat Parvat Landslide.

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IV.TABLE OF CONTENTS

I. CERTIFICATE………………………………………………………..2

II. ACKNOWLEDGEMENT……………………………………………3

III. ABSTRACT…………………………………………………………4

TOPIC PAGE NO.

1. INTRODUCTION………………………………………………7

2. Geology and Tectonics………………………………………10

3. Causes of Landslide…………….…………………………....11

4. Immediate initiatives undertaken……………………...13

5. Geotechnical Investigations…………………………....15

6. Treatments and Stabilisation Measures……………….16

7. Current Status of Landslide …………………………..18

8. Conclusion …...………………………………….…..19

9. REFERENCES…………………………………………….……20

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IV.TABLE OF FIGURES

TOPIC PAGE NO.

1.a-View of Varunavat Parvat before Landslide………………..…….7

1.b-View of Varunavat Parvat after Landslide and Development of three Chutes…………………………………………………………………..8

2-a Geological map of the area……………………………….…………10

3-a Line diagram of daily rainfall plot for July–September 2003………113-b Average annual rainfall totals for the years 1990–2003…………....11

4-a View of Ramlila Groung catchpit……………………………………13

4-b Removal of muck at Ramlila ground…………………………………146-a Stabilisation in rock by means of Rock bolting, Chain link Shotcreting and Cable Anchoring ineased slope……………………………………….16

6-b Support by means of Concrete wall and Wire crate wall in the Crown..17

6-c Slope Stabilisation in Overburden Material by means of Geo‐jute…. ..17

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1. Introduction

Uttarkashi town (Long.78º 26’E, Lat.30º44’N) is located at the toe of the hill slopes of the Varunavat Parvat , on the right bank of Bhagirathi river, at an elevation of ±1150m. It is located at a distance of 155km from Rishikesh on Rishikesh – Gangotri National Highway (NH‐108). River Bhagirathi is passing through the centre of the town almost half of which is located at the base of Varunavat Parvat.

1.a-View of Varunavat Parvat before Landslide

A massive landslide on Varunavat Parvat started on 24 Sept. 2003 subsequent to the incessant rains in the area. The landslide activity progressed eastward from Ram Lila ground to Masjid Mohalla. The slide activity buried a number of civil structures like houses, govt. offices, hotels, etc. which were located by

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the side of NH‐108 at the toe of the hill. Almost 3000 people were affected by the Varunavat slides and property worth Rs 50 crores was damaged. However, it is worth mentioning that no loss of human life occurred during this disastrous slide activity because of timely proactive action taken by the district administration on the basis of early warning given by GSI. The National Highway (NH‐108) was completely blocked by debris flow.

1.b-View of Varunavat Parvat after Landslide and Development of three Chutes

Due to blockade of this highway a 145m long alternate route was opened between Sanskrit Mahavidyalaya‐Mahisasur‐Mardini temple areas. During sliding activity and blockade in Tambakhani area the traffic was diverted via Joshiyara‐Tiloth –Collectorate‐Durga temple route.

GSI geologists while working in this area about one month before the landslide noticed some indications of slope movement on Varunavat Parvat on 21‐24 August 2003 and advised the district administration for immediate evacuation of the high risk zone at the toe of the hill, i.e. Varunavat Parvat. The prompt action taken by the district authorities on this advice from 24.09.03 onwards by

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warning / evacuating the residents from identified high risk zone savedhuman lives when the disaster struck the area.

A total of 293 buildings including 23 government buildings were identified. The landslide damaged 81 buildings completely. 212 buildings prone to damage have been identified in buffer zone.

As soon as the enormity of the hazard was realised by Uttarakhand Government an expert committee was formed by Chief Secretary, Uttarakhand in Sept.2003 to suggest immediate remedial measures with GSI as its member. Thereafter, a Central Composite team was formed by the Ministry of Home Affairs, Govt. of India, New Delhi vide letter No. D27‐05/2003‐NDM‐1 dated 21.10.2003 with Director, GSI as coordinator of the team to assess the situation and to find out possibilities of the stabilisation of Varunavat Parvat as an interim measure and also to explore the feasibility of permanent stabilisation for habitation.

Subsequently, a Task Force was set up under the chairpersonship of Joint Secretary, Ministry of Home Affairs (MHA), Government of India. Under the aegis of this Task Force, a Technical Committee was formed for which Director, Geological Survey of India, Uttarakhand Unit, Dehradun was made the Chairman.

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2. Geology and Tectonics

Uttarkashi town is located in the Lesser Himalayan geotectonic block and it is bounded by two major thrust faults ‐‐ Main Central Thrust (MCT) and Srinagar Thrust (ST). The MCT exists in the north east of Uttarkashi, separating rocks of Garhwal Group and Central Crystalline. The Srinagar Thrust lies in the southwest of Uttarkashi and along this tectonic plane rocks of Garhwal Group and Jaunsar Group are juxtaposed. The Garhwal Group (Proterozoic age)comprises quartzite, phyllite and metabasic rock and these dip 15º‐45º in N10º‐40ºE direction i.e. into the hill. The rocks forming Varunavat hill are composed of thinly bedded quartzite and phyllite which are highly weathered, destressed, decomposed, jointed and fractured. The hill slopes are of the order of 45º‐60º except at the top of the hill where the slopes are gently sloping. The top portion of the Varunavat hill is occupied by loose, unconsolidated, overburdenmass, exhibiting gentle topography. The top is at El.±1800m where as the toe part of the hill is at El.±1100 above msl. The interface of overburden mass and underlying rocks is at El.±1650m. Uttarkashi lies in Zone‐V of Seismic Zoning Map of India and it has a recorded seismic history.

2-a Geological map of the area. Rocks constituting the VarunavatParvat are mainly quartzite and phyllites belonging to Damta group.

3. Causes of Landslides

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The continuous heavy rains in the area led to saturation of the overburden/loose mass occupying the top of the hills above the El.±1650m supporting luxuriant vegetative cover and resting on densely vegetated rocky slopes of weathered quartzite. The saturation by rainwater increased the increase in pore pressure in the overlying overburden mass and lubricated the underlying fractured weathered rock mass. This had in fact reduced shear resistance of theslope materials and thus triggered the slides. Once the slides were triggered, the fast movement of debris flow carried along them uprooted pine trees down the slope and buried the human settlements located at the toe of the hill around Ram Lila ground, Horticulture colony and Masjid Mohalla. The slope movement continued for about a month with dust clouds and then subsided. Past anthropogenic activities especially in the toe of the hill have also rendered the hill slopes vulnerable.

, 3-a Line diagram of daily rainfall plot for July–September 2003.

3-b Average annual rainfall totals for the years 1990–2003.

Daily rainfall plot for July–September 2003 are shown in Figure 3 a, whereas

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Figure 3 b depicts the average annual rainfall for the last 14 years. This clearly shows that the rainfall for the year 2003 is above normal. The slide startedon the day that the rainfall ceased, i.e. 23 In addition to rainfall, several factors probably contributed to slope failure.

(i) Geological structures like shattered, fragmented and highly jointed rocks and topography like steep slopes, interacted to provide the geometry conducive to sliding

(ii) The landslide occurred at the end of the rainy season, which normally is towards the end of September and the groundwater was probably near its highest seasonal level. Rainfall from 17 to May 23 was 72 mm and the week after, the total rainfall was about 73 mm. October and November, no rainfall had been recorded. This marks the near end of the rainy season. Short-duration rainfall certainly could not have produced abnormally high antecedent groundwater levels. It is the collective rainfall of many months that has caused the pore water pressure to rise.

(iii) An unlined canal extended across the crown of the slide. Unsubstantiated reports suggest that the water may have percolated for several months before the slide, which could have significantly raised the groundwater level in the hillside and thus reduced the shear resistance. Infiltration from this canal, along with the copious rainfall, probably also led to further failure of the hill mass.

(iv) Steep-cut slopes for roads, pathways and residential and commercial buildings near the base of the slope may have further destabilized the slope by removing the basal support.

4. Immediate initiatives undertaken

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Immediately after the slide activity an action plan was proposed and adopted forimmediate implementation which included following points:

i) Creation of a buffer zone, close to the toe of the Varunavat. It was re‐demarcated by experts from GSI and CBRI as high risk zone.

4-a View of Ramlila Groung catchpit

ii) Removal of slide material accumulated close to Ram Lila ground along the NH for resuming vehicular traffic

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4-b Removal of muck at Ramlila ground

iii) Starting of geological mapping by GSI in the area as and when site conditions permitted amidst intermittent slide activity in the area. The mapping was confined to accessible slopes only and the rock conditions were interpreted from nearby exposed area.

iv) Construction of an approach track to the crown of the slide for taking up initial stabilisation of overburden slopes.

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5. Geotechnical Investigations

For suggesting permanent stabilisation measures in the slide area, the site specific geological /geotechnical studies proposed were :-

i) Surveying and contouring of the slide area on using Total Station.ii) Geological and structural mapping .iii) Geophysical surveys.iv) Geo‐mechanical testing of overburden mass.v) Slope stability analysis numerical modeling .vi) Monitoring of slope movement by Automatic Target Recognition

(ATR).vii) Studies for bio‐restoration of overburden slopes (by Forest

Research Institute, Dehradun).

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6. Treatments and Stabilisation Measures

Following main treatments were decided for the Varunavat Parvat.

i) Removal of slide mass and grading of the slopes above El 1670m.ii) Treatment of the Crown Portion El ± 1895m ‐El ± 1670m with the

help of rock bolting and shotcreting in the rock and bio‐restoration in the overburden mass.

iii) Cable anchoring in two rows above El ±1670m.iv) Grading of slopes between El ± 1670m ‐ El ± 1550m and

stabilisation by means of geo‐synthetics/geo‐jute, rock bolting and shotcreting in areas where rock is encountered.

v) Treatment along the three chutes, viz. Ramlila Ground, Masjid Mohalla and Tambakhani chutes.

vi) Construction of geo‐grid wall at the toe of Tambakhani chutevii) Construction of a concrete wall at the toe of Ramlila Ground

Chute so that a catch pit is created back of it.viii) Construction of a main catch drain all along the toe of Varunavat Parvat to collect the drainage flowing down the three chutes and through the intervening areas.ix) Construction of a bye‐pass tunnel below Tambakhani chute.

6-a Stabilisation in rock by means of Rock bolting, Chain link Shotcreting and Cable Anchoring ineased slope

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6-b Support by means of Concrete wall and Wire crate wall in the Crown

Portion

6-c Slope Stabilisation in Overburden Material by means of Geo‐jute

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7. Current Status of Landslide

The main treatment works of the Varunavat Parvat landslide area have been completed in 2008 and it is worth highlighting that there is no sliding from the treated parts for the last three years, despite unusually high rain fall (maximum in the last three decades) in Uttarakhand in the year 2010. The contribution of GSI in the for warning of Varunavat Parvat landslide has been duly reflected in the Press Release of Ministry of Mines, Govt. of India dated 12.01.2005 which itself is the testimony to the importance of the role which GSI, Uttarakhand Unit, Dehradun has played in the treatment of Varunavat Parvat Landslide.

GSI has recommended for post‐treatment monitoring of the treated part of theVarunavat Parvat landslide through a comprehensive monitoring scheme with the help of instruments and an Automated Radar system, in order to assess the effectiveness of the support measures.

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8. Conclusion-

There have been a variety of natural hazards, including occasional mass movements of destructive impact in the Himalyan Range and the adjoining regions in the past6. The year 1978 witnessed widespread flooding and landslide activity due to cloud bursts and flash floods in the region. Landsliding in June 1980 had taken a toll of 24 human lives in Uttarkashi District. The disastrous landslide of 23 September 2000 in the area caused widespread damage. All these make it necessary to properly evaluate the potential hazards and suggest appropriate counter measures for futuredevelopment of steep mountain sides and narrow valleys. Based on remote sensing data, this particular stretch of area has been classified as potential landslide hazard zone7. However, on the spot field investigations are necessary to pinpoint the exact areas susceptible to failure under a givenset of conditions.

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9. References

1. Geological Survey of India, pdf. Cs_varnavrat-slide.2. Valdiya, K. S., Wadia Institute of Himalayan Geology, Dehra Dun, slide1980, p. 292.3. Agarwal, N. C. and Kumar, G., Geology of the upper Bhagirathi andYamuna valleys, Uttarkashi Distt, Kumaum Himalaya. HimalayanGeol., 1973, 3, 1–23.4. IAEG (Commission on landslide). Bull. Int. Assoc. Eng. Geol.,1990, 41, 13–16.

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