1. The document provides a method statement for slope stabilization work for an excavated slope at a 10 MW hydroelectric power project site. 2. It describes installing soil nails and rock anchors into the slope, followed by wire mesh and shotcrete layers, to strengthen a cracked irrigation canal embankment and fractured rock slope. 3. Technical details, procedures, equipment, schedules and quantities are provided for installing the soil nails and rock anchors, applying the wire mesh and shotcrete layers, and completing the slope stabilization work over 50 days.

1. AF CONSULT INDIA PRIVATE LIMITED
10 MW, TIGA HYDRO-ELECTRIC PROJECT
METHOD STATEMENT FOR SLOPE STABILIZATION
WORK FOR THE EXCAVATED SLOPE IN POWER
HOUSE AND EXISTING IRRIGATION CHANNEL BUND

2. INTRODUCTION OF WORK
The construction work of Tiga HEP is in progress. During the execution,
the following conditions have been encountered:
1. The aged irrigation Canal Bund existing at site which is facilitating
other Dam in nearby area, has been observed with cracks which
may further develop in future causing seepage/percolation of
channel water towards Power house. This may also cause loss of
water supply to the aforesaid dam. Despite of available slope
protection measures viz. Boulder Pitching/cement pointing, it has
been proposed to provide “additional protection” for the existing
structure for avoiding any untoward situation. It is proposed to
provide Soil Nails in a grid of 2mtr X 2mtr in a staggered way in
the affected area of 20m width X 10mtr height followed by
Wiremesh and Shotcrete.
2. The extremely poor geology with fractured formation of rock has
been encountered which have been weaker than expectation. To
safeguard the slope against failure with the timeline, It is proposed
to provide special protection in terms of cement grouted rock
anchors followed by Reinforced Shotcrete (100X100X4 Wire mesh
within 2 layers of Sprayed Concrete). This treatment will work as
stitching of weathered rock by anchors with a layer of concrete in
the face of rock surface.
TECHNICAL PARAMETERS OF WORK
S.N Description Unit Size
Installation of Soil Nails in Irrigation Canal Embankment
1 Dia. of Tor Steel Bar coated with red oxide mm 32/40
2 Length of Tor Steel Bar coated with red
oxide
mm 3000
3 Spacing among Soil Nails mm 2000 in
staggered way
4 Welded Wire Mesh(100x100x4mm) Sqm 500

3. 5 Shotcrete/Gunniting Sqm 500
Cement grouted Rock Anchor installation in
Rock adjoining CBU and RBU
S.N Description Unit Size
6 Dia. of Tor Steel Bar mm 25
7 Length of Tor Steel Bar mm 3000 to 5000
8 Spacing among Rock Anchors mm 2000
9 Cement Grout with non- shrinkage powder kg 400
10 Face Plate with Hexagonal bolts nos 110
11 Welded Wire mesh(100x100x4mm) sqm 385
DRAWING SHOWING TYPICAL SOIL NAIL/ROCK ANCHOR
DRAWING SHOWING TYPICAL SHOTCRETE/GUNNITE ARRANGEMENT

4. Procedure:
1. Surface Preparation: The surface of the excavated slope will be
cleared with loose rocks to avoid chances for falling rock piece
during course of execution.
2. Drilling of Holes: Drilling of holes shall be carried out upon surface
preparation. The depth of holes will vary from 3m deep to 5mtr
deep. The diameter of the holes shall be 40mm. The holes shall be
drilled at 10o
downward inclined. Jack hammers or, drilling rigs
shall be used for the work based on suitability at field. Since the
height of the area where treatment is to be provided is almost
25m, so, suitable scaffolding shall be required to approach the rock
anchor installation place.
3. Insertion of Rock anchors: Upon successful completion of drilling,
the rock anchors shall immediately be inserted into the holes upto
the desired depth.
4. 1st
Layer of Shotcrete/Gunnite: immediately after completion rock
anchor installation in a patch of 25m X 10m height, Shotcrete will
be applied on the target surface of the slope. The Mix will be of
25mPa strength designed with 10mm down aggregate
ingrediented with accelerator for fast setting of concrete. The
following will be approximate design mix adopted for the work:
DESIGN MIX FOR SHOTCRETE MIX
TYPE CEMENT (KG) WATER(KG) SAND(KG)
10MM
AGG(KG)
ADMIXUTE
(KG)
M30A10 450 220.5 910.4 364.07 7.65
5. Installation of Wire Mesh: After initial setting time of
Shotcrete/Gunnite, 100X100X4mm wiremesh, made of 4mm MS
wire shall be installed on 1st
layer of Shotcrete/Gunnite. The

5. wiremesh shall be supported by nails made of 6mm dia, 150mm
long rod in L shape to hold the wiremesh with the surface. The
Face plate and Hex Nut shall be fixed with Rock anchors keeping
the Wiremesh in between Shotcrete and face plate. Joints in
Wiremesh shall be overlapped by 100mm.
6. 2nd
/Final Layer of Shotcrete: Upon fixing of Wiremesh, Faceplate &
Nut, final layer of Shotcrete/Gunnite shall be carried out to cover
the Wiremesh.
The work shall be carried out in phases of 5 mtr height, completing
the each slope in 5 cycle times.
Key Equipments involved:
1. Jack Hammer or, alternatively Drilling Rig
2. Compressor
3. Gunniting Machine with Hose
4. Concrete Mixer
5. Other Small tools & tackles
Execution Schedule / Duration:
The overall duration of the work shall be 50 days for complete execution
of the work as per the construction schedule below:

7. Quantities involved:
Installation of Soil Nail with Grouting : 400 RM Approx.
Installation of Rock Anchor with grouting : 1700 RM approx
Fixing of Wiremesh : 1500 Sqm
Application of Shotcrete / Gunniting : 1500 Sqm
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