A brief overview of drilling and blasting process for tunnel excavation used in Supermadi HEP

1. KATHMANDU UNIVERSITY
DHULIKHEL , KAVRE
DEPARTMENT OF CIVIL ENGINEERING
PRESENTATION OF INTERNSHIP ON:
SUPERMADI HYDROELECTRIC PROJECT [44 MW]
GROUP MEMBERS:
ARUN KATUWAL
KIMILSUNG LIMBU

2. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
Introduction to the site
• Super Madi Hydroelectric Project is located in Kaski District , Gandaki Zone of
Western Development Region of Nepal.
• The Project lies in the Namarjun and Parche Village Development Committees of
Kaski District about 23 km North-East of Pokhara.
• The project is a simple Run-off-river scheme that utilizes the flow in Madi River
which is one of the major tributaries of the Narayani River .
• The proposed project has installed Capacity of 44 MW, design discharge of 18
m3/s and net head of 295 m .

3. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
• A simple boulder riprap diversion weir across the Madi Khola will divert the water
into the side intake .
• A gravel trap settles gravels and takes water to the head pound.
• 2 underground settling basins will be fed with the discharge by two inlet tunnels from
head pound.
• An outlet pond will feed water into the headrace tunnel of length 5.9 km and finish
diameter of 4.2 m.
• Steel penstock of average diameter 2.6 m and length 1.38 km will feed water to 3
vertical axis Pelton turbines installed in semi-surface power house to generate 44 MW
of electricity.

4. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
Salient Features
General
• Name of river : Madi Khola
• Nearest Town : Pokhara , 23 km
• Type of Scheme : Run-of-River
• Type of Scheme : Run-of-River
• Gross Head : 305m
• Installed Capacity : 44000 kW
Hydrology
• Catchment area : 284.1 km2
• Mean annual Discharge : 30.29 m3/s
• Design Discharge : 18m3/s
• Probability of Exceedance : 40.96 %
• Design Flood Discharge : 1288 m3/s (100 Yr. Flood)

5. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
Diversion Weir
• Type of Weir : Free Overflow with Spillway
• Total Length of Weir : 60m
• Height of overflow Weir from River bed : 5m
• Crest elevation : 1362 masl
• Design Flood Level : 1368 masl
Inlet Tunnel
• Shape : Inverted D
• Numbers : 2
• Length : 52m
• Size (W*H) : 3m*3m

6. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
Side Intake
• Type of Intake: Side Intake ( Orifice Type)
• Size of Orifice (W * H) = 2.4m*1.6m , 6 Nos.
• Intake Sill Level: 1360m
Underground Desanding Basin
• No of Chamber: 2
• Size: 172m*7.5m*14.75m (parallel section 160m)
• Particle size to be settled: 0.20mm @ 90 % efficiency

7. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
Headrace Tunnel
• Type: Inverted D Type Tunnel
• Finish Diameter: 4.2m
• Length: 5905m
• Support: Fully concrete Lined ( 800m ) Shotcrete Lined (5105m)
Surge Tank
• Type: Circular, Underground
• Height: 37 m
• Finish Diameter: 9m
Penstock Tunnel
• Type: Inverted- D Type Tunnel
• Finish Diameter: 2.8 circular penstock
• Length: 38m

8. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
Objectives
• To get exposure to engineering duties and responsibilities.
• To develop the proficiency to function in diverse engineering and managerial
settings based on core knowledge, skills, attitudes and aptitudes acquired during
the in-campus semesters.
• To be aware of engineering norms, values and ethical practices.

9. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
Task Performed
Task
Performed
Site Reconnaissance
Drawings Study
Site Supervision
Interactions with diverse Professionals
Daily Observation Log Preparation
Weekly & Monthly Progress Report Preparation

10. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering

11. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering

12. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering

13. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering

14. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
Tunnel Cycle
Due to the abundance of tunnels in our site we had the opportunity to observe a
complete tunneling cycle which consists of the following sequence of processes: -
1. Drilling
2. Loading & Stemming
3. Blasting
4. Ventilation
5. Mucking & Scaling
6. Geological Mapping and Surveying
7. Rock support Installation
8. Shotcreting

15. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
1. Drilling
• This is the first process in the tunnel cycle.
• We observed the drilling process being carried out manually using jack hammer with
pushers’ leg mostly in the Inspection tunnel and Kalbandi Headrace tunnels.
• The length of drill holes varying up to 2 meters (mostly 1.5m and 1.7m) depending
upon the pull required.
• Drilling was also carried out for Rock Bolt installation.
• Drilling was carried out by Boomer in Adit II tunnel.

16. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
• For the drilling process , we found out the average time taken for the jack hammer
and boomer to drill a hole of 1.7 m diameter as shown in the table below :
Equipment Avg. Time taken(s) Rock Class Manpower Required for operation
Jack Hammer 187 III At least 3
Boomer 130 I At least 2

17. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
Fig: Jack Hammer Fig : Boomer
Fig : Drilling by Boomer
Fig: Drilling by Jack Hammer

18. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
2. Loading & Stemming
• Packing or insertion of the explosives into the holes for the purpose of blasting is known
as Loading.
• The Process of sealing drill hole and retaining the explosive gases within it is called
Stemming.
• Loading was carried out manually in the site.
• Emulsions Explosives were mainly used in the site while loading.
• The energy released as a result of explosion is much higher in compared to other
emulsion explosives.

19. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
• The following observations were made in the site during the loading phase of the tunnel
cycle: -
Explosive Type: Emulsion Explosives
Explosive Brand Name: Superpower 90
Explosive Cartridge Size & weight: 32 mm dia., 200 gm
Average Time Taken to load a hole: 57 sec (Including Detonator placement &
stemming, Manually)
Materials used for stemming: Clay and Sand

20. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
Fig : An Emulsion Explosive Cartridge Fig: Loading and Stemming of a Hole manually

21. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
3. Blasting
• The Blasting or detonating procedure was performed with the means of detonator
which charged the emulsion explosives.
• The Blasting procedure was allowed to be carried out by an only authorized personnel
like a Blaster in the site.
• The detonators used for the purpose of blasting was Electrical type Short Period Delay
(SPD)detonators with the variance of milli second detonation delay from one another.
• The major milliseconds delay detonators used in the site varied from 1 millisecond
delay detonator to 10 milliseconds delay detonators.

22. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
Fig: A 10 millisecond delay detonator Fig: A detonator trigger and ohm meter

23. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
Video of blast in the inspection tunnel

24. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
4. Ventilation
• The site was cleared for few minutes for the explosive gases to disperse.
• Since the Kalbandi Headrace Tunnels, Inspection Tunnel and Headrace Tunnel outlet
were in the initial stages of excavation there were no provisions for mechanical
ventilators in those sites.
• The explosives gasses were allowed to disperse through the flow of natural air without
any external means for about 10 - 15 minutes before mucking process commenced.
• Ventilation in the Adit II Tunnels at Bagalethar was carried out by a single fan
ventilator. The ventilation time varying from 20 minutes to 30 minutes.

25. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
Fig: A single Fan Longitudinal Ventilator used in Adit II Tunnel

26. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
5. Mucking & Scaling
• Mucking refers to the process of removing the muck after blasting and throwing outside the
tunnel.
• Mucking was carried out by a loader in our site.
• Major used wheel loaders in our site were XCMG LW 300kN and XCMG ZL 50 GN.
• Scaling refers to the process of removal of the muck that sticks to the tunnel face after the
Mucking process.

27. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
• Scaling was carried out in the site manually by hitting the tunnel face with the pressurized
jet of water and by hitting the tunnel face rocks by loading sticks.
• In average the time taken for mucking and scaling was about 2 hours.

28. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
Fig: A loader used for mucking Fig: A tipper used for muck disposal
Fig: Scaling process carried out Fig: Mucking in tunnel by a loader

29. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
6. Geological Mapping and Surveying
• After the process of scaling the geologists work was to make the geological log sheet of the
rock class type of joints and faults and other aspects relating to the geological mapping of
the tunnel face.
• The Rock Class of the tunnel face is found out after the determination of Rock Tunneling
Quality Index (Q-value).
• The process of geological mapping is simultaneously followed by surveying.
• Along with the alignment fixing of tunnel, surveying was carried out to determine the
chainage and pull from the recent Blast.
• Resection is carried out to fix the tunnel alignment, the steps followed to carry out
Resection is explained in detail in Daily Observation Log.

30. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
Fig: A surveyor conducting alignment
survey of tunnel
Fig: Face mapping by a Geologist

31. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
7. Rock Support Installation
• After the geologists identify the the rock support class than the supports pertaining to
the suitable tunnel face and the rock mass was installed which was either spot bolt ,
Rock Bolt or in worst cases Ribs which was done in accordance with the rock class
determined as per the approved design drawings.
Fig: Rock bolts Fig : Rib Installation

32. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
Short Description on the type of supports used
• Spot Bolt
These are the bolts which are locally installed at sites that appear to be prone to failure
,may be on the roof or floor.
Spot bolts are used at certain spots to prevent failure of individual blocks and wedges.
The observed dimension of the rock bolt used in our site was 2m length and 20mm
diameter.

33. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
• Rock Bolt
 Is generally a long anchor bolt.
Used for stabilizing rock excavations in the tunnels and rock cuts.
It transfers load from the unstable exterior to the confined (and much stronger) interior of the
rock mass.
Dimensions of rock bolt used in the site were 2-2.5m length with 20 mm diameter.

34. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
Fig : Rock Bolt Fig : Installed Rock Bolt

35. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
• Rib Installation
Ribs were installed in the excavation sites of the tunnels specifically, pertaining to the particular
rock classes with low stability.
Ribs of IS standard I – section (IS 808, ISMB 150, 15kg/m) in combination with high strength
concrete were used.
In our site the rib was of arc and post type with two pieces of each component.
The arc and post were attached to each other by plates and nut bolts.
The dimension of the plate was 18cm * 15cm and of the diameter of bolt was 16mm.
There were 4 holes and bolts in the plate with the diameter of holes 2mm greater than of bolts.

36. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
Then the backfilling was performed which was done in the form of boulder packing.
The boulders were then bind with cement mixture of M25 strength.
The backfilling were held by wire mesh with dimension of 2.1m*1.1m and 4.75mm diameter
,usually six number of wire mesh were used per rib.
Tie rod and anchor rod were also used for further support and stabilization of the rib.
The tie rod was 20mm diameter and 1m length whereas the anchor rod had same diameter but
the length was 2m.

37. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
Fig : Rib Installation Fig : Tie Rod Welding

38. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
Fig : Wire Mesh
Fig : Anchor rod
Fig : Boulder Packing

39. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
• Shotcreting:
Shotcrete refers to concrete or mortar conveyed through a hose and pneumatically projected at
high velocity onto a surface, as a construction technique.
In our Internship we only observed dry shotcreting at our site.
The materials used were cement , sand , water and aggregate of nominal max size 10mm.
The design strength of shotcrete was generally M30 .
Steel fiber Crete was used as reinforcement.
For rapid setting of shotcrete accelerating admixture for dry shotcreting was used.
Generally 25 kg admixture was used per batch of shotcreting.

40. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
Fig : Shotcreting Fig : Mixer for mixing of materials

41. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
• Slope Stabilization
This was generally performed in the early stages of the tunnel construction.
The bearing capacity of the natural slope decreases due to tunnel face excavation.
Cement grouting or shotcreting was done for stabilization in accordance with the slope
condition.
Spiling rods were also used to support the tunnel during early stages .
Spiling rod provide a protective canopy, to enable the heading of a tunnel to be advanced
without the risk of falling debris .

42. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
Fig : Grouting of Slope Fig: Spiling Rod

43. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
Rock Class Support Type Pattern Spacing
I 2m long,20mm dia. Spot Bolt with Dry Steel
Fiber Shotcrete 50mm thick
1-1 -
II 2m long,20mm dia. Rock Bolt with Dry
Steel Fiber Shotcrete 75mm thick
5-6 1.6m c/c
III 2m long,20mm dia. Rock Bolt with Dry
Steel Fiber Shotcrete 100mm thick
6-7 1.4 m c/c
IV 2m long,20mm dia. Rock Bolt with Dry
Steel Fiber Shotcrete 125mm thick
7-8 1.2m c/c
V 2.5m long,20mm dia. Rock Bolt with Dry
Steel Fiber Shotcrete 150mm thick
8-9 1m c/c
VI 3m long,20mm dia. Rock Bolt with Dry
Steel Fiber Shotcrete 200mm thick & ISMB
150 beam sets 1m c/c
8-9 1m c/c
ROCK SUPPORT TYPE

44. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
Fig: Steel fiber crete used as reinforcement Fig: A mixer

45. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
Activity Time (min) Specifics [Tunnel 4.2m x 4.2m D-shape]
Drilling 220** Avg. approx. 74 holes per round, Jackhammer on pushers leg
Loading 90 Approx. 73 kg explosives loading per blast
[Gneiss/Quartz]
Blasting 20 -
Ventilation 15 -
Mucking 140 Mechanical [1 Loader, 1 tipper]
Scaling 20 Manual
Surveying and Face Mapping 50 Resection and Q-Value Evaluation
Rock Bolting 170 Tunnel Support Type III Pattern [6/7 @ 1.40m c/c]
Shot Creting 210 (Approx. 125mm – 150mm thick)
Time for one round 935 Approx. 16hours per round, Pull obtain=0.9m-1.7m
=1.3m avg
Weekly Progress 2shifts, 9hrs per shift,
14shift per week
14 shifts/week*9 hrs/week*1.3 m pull
16 hrs
=10.2 m/week
TUNNEL CYCLE TIMES OF A FULLROUND-KALBANDI KHOLSI TUNNEL SITE
** Avg. drill time found to drill a hole of 1.7m length was 3m -4m. Drilling time varies depending upon rock mass
and efficiency of workers.

46. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
Major Problems Encountered In The Worksite
Human Errors
• Not arriving in time for work.
• Lack of skill and diligence in some manpowers.
• No consideration for proper and optimum material usage.
• Mishandling of equipment.
Technical Errors
• Machine wearing due to continuous use.
• No proper maintenance of equipment.
• No availability of advance equipment in all of the sites like boomer.
• Unavailability of electricity for certain time period.
• Less consideration for safety of manpower such as no availability of safety googles etc.

47. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
Geological Problems
• Very strong rock class in Adit II tunnels due to which problems of socket holes and
under break occurred of length 30cm to 80cm due to hard rock.
• Very weak rock class in outlet tunnel due to which continuous rib installation and
also rock over break occurred.
Other Problems
• Unexpected and unscheduled problems such as continuous strikes, Banda etc.
• Untimely payment of salary which lead to strikes from man power.

48. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
A BRIEF OVERVIEW OF OUR FIELD VISIT TO OTHER HYDRO PROJECTS
• As our major observation were based on the works of a tunnel cycle and our selected
project was in initial phase of the construction during our internship period, we asked
our supervisor Mr. Ganga Ram Maharjan for a field visit to other hydro-projects for
observation of major hydro-power related structures in which he agreed to volunteer.
• Field visit was made to Himalayan Hydroelectric project [12 MW] located d/s to our
project.
• Similarly, field visit was made to the Middle Modi Hydro project [15.1 MW] as per
the course of study of our internship period. The report of this field visit is briefly
discussed in the Daily Observation logs of date (15-16)/02/2076.

49. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
Fig: ongoing Anchor block and Saddle Support construction of Himalayan Hydro project
Fig: ongoing construction of powerhouse and saddle supports of Himalayan Hydro Project

50. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
Fig: Headworks of Middle Modi hydro project [MMHP]
Fig: Headrace canal of MMHP Fig: Settling basin of MMHP

51. Internship Project - GROUP 11 Kathmandu University , Department of Civil Engineering
Fig: Headrace Tunnel outlet Fig: Ongoing Powerhouse construction
Picture with supervisor