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DDC: Client: DGPCL

HRT Upstream 1375 m

Distance from HRT Junction [m] 280.3m (Pull: 2.45m) "Niche Starts" Overburden [m] 85m

Unsupported length [m] Excavation Method Drill & Blasting

Excavation Approach Full Face

Notes:

Lithologies

Legend J2

Random 1

Staining

Joints

J1 Planer + Rough J1

J2 Planer + RoughRandom Joint/J4

Random/J4

J3J1

J4 Random + Planer + Rough

ABIR INFRASTRUCTURE PRIVATE LIMITED

TSIBJALUMCHU DIVERSION SCHEME, Tala, Bhutan

TUNNEL FACE MAPPING SHEET No. 112 Prepared by

contractor:

Amit Sharma

Tunnel Direction: 113

Tunnel Axis : 3.5m ,Tunnel Dimension SPL to SPL : 4.8m

Qty of explosive used : 170 Kg, No. of Charged holes: 70

Date 2013-03-14Location : Tala Dam Top

GENERAL CHARACTERISTICSElevation at the front [msl (m)]

TUNNEL EXCAVATION FACE GEOTECHNICAL DESCRIPTION

Structure, Texture & Mineral Assemblages: -

The rock mass exposed having gneissose structure with

with medium to coarse grained texture.The mineral

assemblages observed are quartz, staurolite, kyanite,

felspar, biotote & muscovite.

Water (flow, dripping, wet, damp, dry)

Geo-lithologic characteristics

Legend

Mica Gneiss

Front Proceeding From

K5

K5

K4

type dip/dir Spacing (m) Persistence (m) Roughness Opening (mm) Alteration Infillings

J1 75/252 0.25 - 0.4 0.25 - 1.5 Rough 0.1 - 1 Unaltered NoneJ2 65/265 _ 1 - 1.25 Rough 0.1 - 1 Unaltered NoneJ3 _ _ _ _ _ _ _

J4 44/135 _ 1 - 1.25 Rough 0.1 - 1 Unaltered None

Instability phenomenons Actual Support SystemFront Roof Ribs Shotcrete Rock Bolt Notes

Wedges instability

Caving

Spalling/Rock bursting

Squeezing

"do" "do" "do"

AIPL Geologist DGPC Geologist/Representative

UCS (in Mpa) : 60 - 80

Note

100 mm Steel Fibre

Reinforced

Shotcrete

25mm , 4 mlong, 8 Nos., all

through the

periphery

Rock Mass Characteristics:

The rock mass observed is composed of thinly foliated, dark grey colored, mica gneiss with presence of quartz bands

parallel to foliation plane. The rock mass is slightly to moderately jointed and characterised with 2+ random joints set and

dry water conditions. No signs of alteration have also been observed in the rock mass. As per the tunnel rock quality index

'Q', the rock mass falls under "Class B'', "Good Rock" Category.

Tunneling Class (NGI) "Q" Value: 32.8

Face Reinforcement

None

Rock mass

Not Required

"do"

Rock Class: Class B - Good Rock

Recommended Support System:

To support the

increased span

of tunnel

because of niche

construction

Not Required

Main discontinuties (ISRM 1981)

"Q" Parameters : RQD = 98.5 Jn = 6 Jr = 1.5 Ja = 0.75 Jw = 1 SRF = 1

Others parameters (tested/esteemed)