assessment of a failed slope on mandi-pathankot … fileanalysing complex slopes. midas gts nx is...

International Journal of Technical Innovation in Modern

Engineering & Science (IJTIMES) Impact Factor: 5.22 (SJIF-2017), e-ISSN: 2455-2585

Volume 4, Issue 7, July-2018

IJTIMES-2018@All rights reserved 561

ASSESSMENT OF A FAILED SLOPE ON MANDI-PATHANKOT HIGHWAY,

HIMACHAL PRADESH USING MIDAS GTS NX

Nitin Ankur 1 ,Vinod K. Sonthwal

2

1 M.E. Student, Civil Engineering Department, NITTTR Chandigarh

2 Associate Professor, Civil Engineering Department, NITTTR Chandigarh

Abstract— Slope failures are one of the most recurring disasters in hilly areas resulting in loss of life and

infrastructure. With the advancement in computer programming, the drawback of simple and popular traditional

Limit equilibrium methods have been subdue by Finite Element Modelling which uses strength reduction method for

analysing complex slopes. MIDAS GTS NX is FEM based software which enables to predict cause and type of failure.

The paper focuses on determination of factor of safety of a failed slope on Mandi-Pathankot highway using MIDAS

GTS NX.

Keywords— Slope stability, 3-D Modelling, Finite Element Modelling, Strength Reduction methods, MIDAS GTS NX

I. INTRODUCTION

With the increase in rapid and ambiguous construction practices in hilly areas, there are severe chances of slope failure.

Slope failures are more prominent during rainfall or any seismic activity. NH-154, road connecting Mandi and Pathankot

is highway of national importance. Slopes along this highway are prone to failure during monsoon periods. The area has

witnessed massive landslides in recent past resulting in immense requirement for conducting slope stability analysis in the

region. Various methods of slope stability analysis have been developed over the years to prevent or minimise the extent

of slope failure. Traditional limit equilibrium method is the most simpler and popular method, being practiced around the

world [1]. Despite of its simplicity, method has some drawbacks involving the assumption of dividing soil mass into slices

which further necessitates further assumptions regarding side forces [2][3]. With remarkable development in computing

resources, Finite element method (FEM) has turned out to be a potent and expedient alternative for traditional limit

equilibrium methods [4]. In FEM, there is no assumption regarding the shape of failure, location of failure, slices and side

forces. FEM considers the failure naturally through weak zones where shear strength is unable to withstand driving forces

[3][4].The most famous technique for executing finite element modelling analysis of a slope is shear strength reduction

(SSR) approach [3]. The SSR is a simple approach which includes reducing the failure envelope by a factor of safety and

analyse FEM models until and unless deformations become unacceptable [5].

II. RELATED WORK

With the advancement in stability analysis methods using finite elements, various studies have been conducted for

analysing slopes using finite element method. Griffths and Lane [3] compared limit equilibrium methods with finite

element methods by performing slope stability on 30 different slopes and concluded that Finite element method is a well-

grounded and vigorous method for determining Factor of safety and performing slope stabilisation analysis. Hammah et

al. [4] recommended the widespread use of FEM as it is possible to visualise failure mechanism in LEM which is not

possible in limit equilibrium methods. Tao Xiang [6] investigated the stability of a landslide with the help of MIDAS GTS

NX and suitable remedial measures were suggested. Sakia and Dey [7] carried out the static and dynamic slope stability in

Sonapur, Meghalya using MIDAS GTS NX program. Goel and Sonthwal [8][9] conducted a slope stability study in Morni

Hills area Haryana India using MIDAS GTS NX and recommended the use of this software for slope stability analysis.

International Journal of Technical Innovation in Modern Engineering & Science (IJTIMES) Volume 4, Issue 7, July-2018, e-ISSN: 2455-2585,Impact Factor: 5.22 (SJIF-2017)


III. METHODOLOGY

Disturbed soil samples were collected from a failed slope on Mandi-Pathankot Highway and series of tests were

performed for determining the properties required for performing slope stability analysis in MIDAS GTS NX. The

properties of soil sample obtained from laboratory tests are given in Table I. A 3-D model of the failed slope was made on

MIDAS GTS NX and properties were assigned to different strata as obtained in laboratory. A hybrid mesh of size 5 is

adopted for the study and higher order elements were considered. 3-D model in MIDAS GTS NX is then post processed

using Strength Reduction Method for the determination of factor of safety of the slope in dry as well as rainy period.

TABLE I

SOIL ENGINEERING PROPERTIES OF SOIL SAMPLES

S. NO. PARAMETERS SAMPLE 1 SAMPLE 2 SAMPLE 3 SAMPLE 4

1. Bulk weight (kN/m3) 15.48 24.6 19.49 19.21

2. Saturated weight (kN/m3) 17.16 24.5 21.42 20.95

3. Void ratio 0.52 0.10 0.37 0.32

4. Cohesion (kN/m2) 36.44 29.34 18.81 28.1

5. ANGLE OF INTERNAL FRICTION (O) 31.44 43.86 44.33 45.53

Fig. 1 3-D model of a failed slope on Mandi-Pathankot highway

Fig. 2 Mesh generation and assigning of properties



IV. RESULTS

Fig. 3 Displacement during dry period

Fig. 4 Deformation during dry period

Fig. 5 Displacement during rainy period

Fig. 6 Deformation during rainy period



On performing slope stability analysis in MIDAS GTS NX, the displacement and deformations for dry and rainy period

were obtained. Comparison between the factor of safety for the dry and rainy period is shown below.

Fig. 7 Comparison of Factor of Safety during Dry and Rainy period

V. CONCLUSION

Through this study, it is concluded that the failed slope on Mandi-Pathankot highway is highly unstable and prone to

failure during rainy periods having factor of safety 1.05 and suitable remedial measures must be adopted as soon as

possible for preventing major landslide. Moreover MIDAS GTS NX is a user friendly finite element modelling tool which

can perform slope stability analysis in relatively less time with more accuracy.

REFERENCES

[1] Hamdham Indra Noer “Slope Stability Analysis With the Finite Element Method” Department of Civil

Engineering, National Institute of Technology, Bandung,Indonesia

[2] Saha, S. “Detailed Stability Analysis of Slopes by Finite Element Method” Indian Geotechnical Conference – 2010,

GEOtrendz December, 2010, IGS Mumbai Chapter & IIT Bombay (2010)

[3] Griffth, D. V. and Lane, P. A. “ Slope Stability Analysis by Finite Elements” Geotechnique 49, no. 3, 387-403

(2001)

[4] Hammah Reginald, Yacoub Thamer, Corkum Brent, Curran John “A Comparison of Finite Element Slope Stability

Analysis with Conventional Limit-Equilibrium Investigation” Rocscience Inc., Toronto, Canada (2005)

[5] Hammah, R. E., Yacoub, T. E., Corkum, B. C., Curran, J.H. “The Shear Strength Reduction Method for the

Generalized Hoek-Brown Criterion” American Rock Mechanics Association ARMA/ USRMS 05-810 (2005)

[6] Tao Xiang “The Application and Analysis of MIDAS GTS in Landslide Control” International Journal of

Engineering Research Vol- 4, Issue No. 8, pp: 409-411 August 2015 (2015)

[7] Sakia Rupam, Dey Ashim Kanti “Slope Stability Analysis of Slides at Sonapur using Strength Reduction Method”

Indian Geotechnical Conference IGC2016, December 2016, IIT Madras, Chennai, India (2016)

[8] Goel Tarun, Sonthwal K. Vinod “A Review on Slope Stability Analysis by Strength Reduction Method using

MIDAS GTS” International Journal of Innovative Research in Science, Engineering and Technology Vol. 6, Issue 8,

August 2017 (2017)

[9] Goel Tarun, Sonthwal K. Vinod “ Slope Stability Analysis of a 15m Slope in Morni Region of Shivalik Himalaya”

International Journal for Scientific Research & Development, Vol. 5, Issue 06,2017, pp: 2112-2114, 2017

1.23

1.05

0.95

1

1.05

1.1

1.15

1.2

1.25

Dry Period Rainy Period

Fact

or

of

Safe

ty

assessment of a failed slope on mandi-pathankot … fileanalysing complex slopes. midas gts nx is...

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