INTERNATIONAL JOURNAL OF LATEST TECHNOLOGY IN ENGINEERING,

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ISSN 2278-2540 | DOI: 10.51583/IJLTEMAS | Volume XIV, Issue III, March 2025

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Analysis of Road-Cut Slope in Calcareous Rocks and Stabilisation

by Shotcreting and Rock Bolting, Dehradun-Mussoorie Road,

Uttarakhand

Virat Singh Chauhan, Md. Rehan Sadique, Mohd. Masroor Alam

Aligarh Muslim University

DOI : https://doi.org/10.51583/IJLTEMAS.2025.140300033

Received: 01 April 2025; Accepted: 05 April 2025; Published: 14 April 2025

Abstract – In this study, analysis and stabilisation of four road-cut slopes in the lesser Himalayan region near Mussoorie, along

Dehradun- Mussoorie Road, are investigated using the shotcreting and rock bolting technique. The rocks studied are calcareous in

nature with varying rock mass properties. The exposure is along the road cuts with slope varying from 70

to 90

, showing

toppling to wedge failure. The stability analysis is performed through the Finite Element Analysis (FEA) and Factor of Safety

(FOS) is evaluated using the Shear Strength Reduction Technique. The evaluation considers various conditions, including

unreinforced slopes and slopes reinforced with rock bolts and shotcrete, to thoroughly assess the effectiveness of rock bolting in

enhancing stability. The results indicate that rock bolting combined with shotcreting improves slope stability by approximately

10–40% across the different slopes analyzed.

Keywords: Dehradun-Mussoorie Road, Limestone, Road-Cut Slope, FOS, Rock Bolting.

I. Introduction

Rock Bolts are one of the widely used methods of stabilisation in case of rocky slopes, tunnels, underground structure, mining

etc. The technique works by transferring load from the unstable slope surface to the interior stable slope with the help of high

yield strength deformed bars in combination with shotcreting (Hoek & Bray, 1981). This combination results in the increment in

the shear strength and overall stability of the rock mass (Hoek et al., 2000). Rock bolts are particularly effective in fractured or

jointed rock masses where they act by tying and reinforcing the jointed rock mass, thus reducing displacement, and preventing

failure (Singh and Goel 2011). The effectiveness of rock bolting largely depends on several factors such as the length, spacing,

orientation, and anchorage methods of the bolts, as well as the geological conditions of the slope (Singh and Goel 2011). The

geological condition of slope is governed by strength of rock and overall character of rock mass. The analysis of rock bolting can

be done by using Numerical Modelling techniques, such as the Finite Element Method (FEM) combined with the Shear Strength

Reduction (SSR) technique (Jing & Hudson, 2002) to evaluate the factor of safety of the slope.

The current study focuses on the stability analysis of four road-cut slopes along NH-707A near Mussoorie along Dehradun-

Mussoorie Road, Uttarakhand (Fig. 1a). The rocks are largely calcareous and include largely limestone with some dolomite

intercalations (Jiang et al.). The rock sequence stratigraphically belongs to Krol Formation, encircling the Mussoorie Syncline

(Fig. 1b). The rocks are moderately strong with less than 40 MPa of compressive strength. The rocks show loss of strength due to

random cracking at microscopic scale as well as due to weathering when dolomitised and comes down to 30 MPa. The roadside

view of the four locations is shown in Fig. 2.

(a)

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(b)

Fig. 1: (a) Map showing the distribution of the various synclines within the Krol Belt which contains Tal Group (modified

after Jiang et al., 2002); (b) Geological Map showing Mussoorie location of the section examined (modified after Khan et al.,

2016).

The studied slopes are found to have slope varying from 70

to 90

(> 45

). The rock mass comprises three discontinuity sets with

varying spacing, forming rectangular to cuboid-shaped with volumes ranging from 0.08 to 0.2 m³ at locations L1, L3, and L4.

Location L2 experiences wedge failure along three sets of conjugate joints, resulting in the formation of large prismatic wedges

with volumes ranging from 2 to 8 m³. While toppling failure is observed at locations L1, L3, and L4.

Fig. 2: Roadside view of the four road-cut slope locations.

The rocks are Micritic Limestones, moderately to highly weathered due to their presence in the humid tropical conditions. The

rocks show micro-fractures which are sealed with Calcite-Quartz veins (Fig. 3), suggestive of intense compressive tectonics

involved along the convergent plate margin, characteristic of Himalayan Tectonics.

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Fig. 3: Photomicrograph of Krol Limestone with Micro-Crystalline Calcite interspersed with micro veined cracks of calcite and

quartz. (a) Under Non-Polarised and (b) Under Polarized Light (60 X Magnification).

The analysis is performed on Rocscience RS2 software. The analysis is carried out in two stages: first, without reinforcement, and

then with reinforcement applied using shotcrete and rock bolting. The stability assessment is done to comprehensively evaluate

the effectiveness of rock bolting in enhancing the stability of the slope.

II. Method of Analysis

To carry out stability analysis in Rocscience RS2 software, the material parameters are collected from the field surveys and

laboratory studies for Slope Height, Slope Inclination, Geological Strength Index (GSI), rock mass characterization and

Unconfined Compressive Strength (UCS) of the rock material. The slope is modelled using six-node triangular elements. The

boundary condition is kept fixed at the bottom, while one side is restrained in one direction(Griffiths and Lane, 1999). The

geometry of the model with and without reinforcement is illustrated in Fig. 4. The material model is selected as Generalised

Hoek-Brown model due to the non -linear nature of the rock mass. The stability assessment is done using shear strength reduction

technique (Dawson et al., 1999). The material parameters utilised for slope stability analysis are shown in Table 1.

Table 1. Slope and Rock Mass Parameters used for performing Finite Element Analysis

Parameters

Height (m)

Inclination (°)

Unit weight (kN/m

)

UCS (MPa)

GSI

(MPa)

2606

1834

837

1080

Bolt Length (m)

Fig. 4: (a) Geometry of the model for Location L1 without any reinforcement (b) Total Displacement profile for L1 (c) Geometry

with Shotcrete (d) Total Displacement with Shotcrete (e) Geometry with Shotcrete and Bolts (f) Total Displacement with

Shotcrete and bolts.

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III. Results and Discussion

The study focuses on the stability analysis of four road-cut slopes using Rocscience RS2 along Dehradun-Mussoorie Road. For

analyzing the slopes, Generalised Hoek Brown model is taken as material model. The stability analysis is performed using the

Shear Strength Reduction (SSR). The analysis is carried out in three stages, first without any reinforcement and second with

reinforcement as shotcrete and thirdly combination of shotcreting and rock bolts.

In the first stage, when no reinforcement is applied, the calculated FOS values for the four slopes were found to be 1.14, 1.05, and

0.72, 0.83 respectively. These low FOS values indicate marginal to unstable conditions of the slopes, which are caused due to

adverse orientation of discontinuities and slope, low Uniaxial Compressive Strength (UCS) of weathered limestone, Geological

Strength Index (GSI), steep slope angles and tectonic activity in this region.

In the second stage, shotcreting with a thickness of 20 cm is applied to the slope surfaces. The shotcreting resulted in a marginal

increase in FOS by 10-15%. While location L1 and L2 became stable with shotcreting, locations L3 and L4 remained in the

unstable category. In the subsequent stage, shotcreting is combined with rock bolts, with the bolts installed at a length equal to

40% of the slope height, diameter of 32mm, spacing 1.5m c/c and oriented at an inclination of 15° clockwise to the horizontal

plane. The inclusion of rock bolts significantly improves the stability of the slopes, with FOS values increasing by approximately

20–40% as illustrated in Fig. 5. This improvement highlights the effectiveness of rock bolts in conjunction with shotcreting in

enhancing the slope stability by providing additional shear resistance and restricting potential failure mechanisms.

Fig. 5: Graph Showing Variation of Factor of Safety values for unreinforced and reinforced Slopes.

IV. Conclusions

This research employed Rocscience RS2 software through the Generalized Hoek-Brown model to determine stability aspects of

four road-cut slopes along NH-707A in Mussoorie, Dehradun, Uttarakhand India. Three different conditions were evaluated using

the Shear Strength Reduction method for determining the Factor of Safety (FOS): initially without reinforcement, with

shotcreting and with shotcreting combined with rock bolt installation. The analysis performed without rock bolts produced

stability results of 1.14, 1.05, and 0.72, 0.83 which indicated partial stable to unstable behaviour due to very unfavourable

discontinuity orientation, low UCS, GSI values along with steep slopes in a active tectonic setup.

The application of 20 cm thick shotcreting marginally improves FOS by 10–15%, stabilizing locations L1 and L2 but leaving L3

and L4 in the unstable category. However, the combined application of rock bolts and shotcreting significantly enhances slope

stability. Rock bolts with lengths measuring 40% of slope height became more effective when installed at 15° inclination thus

raising the FOS by 20–40%. The performance of rock bolts becomes apparent because they provide shear strength enhancement

which controls potential failure conditions. The study concludes that rock bolting is a practical stabilization technique for road-cut

slopes in challenging geo-tectonic conditions, such as in Himalayan states.

References

1. Hoek, E., & Bray, J. W. (1981). Rock Slope Engineering (3rd ed.). The Institution of Mining and Metallurgy, London.

2. Hoek, E., Carranza-Torres, C., & Corkum, B. (2000). Rock mass properties for underground mines. In Proceedings of

the North American Rock Mechanics Symposium.

3. Singh, B., & Goel, R. K. (2011). Engineering Rock Mass Classification: Tunnelling, Foundations and Landslides.

Elsevier.

0.6

0.7

0.8

0.9

1.1

1.2

1.3

1.4

1.5

1.6

1 2 3 4

Factor of Safety (FOS)

Locations (L1-L4)

No Reinforcement

Shotcrete

Shotcrete with Rock

Bolts

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ISSN 2278-2540 | DOI: 10.51583/IJLTEMAS | Volume XIV, Issue III, March 2025

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4. Jing, L., & Hudson, J. A. (2002). Numerical methods in rock mechanics. International Journal of Rock Mechanics and

Mining Sciences, 39(4), 409–427.

5. Griffiths, D. V., & Lane, P. A. (1999). Slope stability analysis by finite elements. Géotechnique, 49(3), 387–403.

6. Dawson, E. M., Roth, W. H., & Drescher, A. (1999). Slope stability analysis by strength reduction. Géotechnique, 49(6),

835–840.

7. Khan, K. F. and Israeli, S. H. (2005) Geochemistry and depositional environment of Mussoorie phosphorite deposits,

district Dehradun, Uttaranchal, India., J. Appl. Geochem., 7 (2) (2005), pp. 227-247.

8. Jiang, G., Christie-Blick, N., Kaufman, A.J., Banerjee, D. M. and Rai, V. (2002). Sequence Stratigraphy of the

Neoproterozoic Infra Krol Formation and Krol Group, Lesser Himalaya, India., J. Sediment. Res., 72 (2002), pp. 524-

542.

9. Khan, S. A., Dar, S. A., Khan K. F. and Karim, Y. (2022). Geochemical Characteristics of Early Cambrian Phosphate

Bearing Sedimentary Rocks from the Mussoorie Syncline, India: Implications for Paleo-Redox Conditions. Geosystems

and Geoenvironments, V 1 Issue 3., https://doi.org/10.1016/j.geogeo.2022.100046.