University of Engineering & Technology, UET, Lahore.

Kalabagh Salt Mine

Stress assessment and pillar support design

Worked By;
Muhammad Haseeb Aamir (2017-Min-34)
Muhammad Faizan (2017-Min-01)

3RD year Student at Mining Engineering Department UET, Lahore.

 A project report submitted to Dr. Zaka Emaad, Faculty of Mining Engineering
Department of UET, Lahore, in fulfilment of partial requirements for the degree of BSc Mining
Engineering.
(Mining Engineering)
Date: 11-July, 2020

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Statement of Originality:
This report is clearly prepared by us and we didn’t copy any text from other link or article.
Some documents, properties, material and concepts were understood or taken as example to
prepare the report from other organizations, web links, research papers or any other mean, but
their references are mentions in the report. Please do not copy without permission and it is
properly work done by us.

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Preface & Acknowledgments:
The work presented in this report was carried out as a Complex Engineering problem at Mining
Engineering Department, Faculty of Earth Sciences, UET, and Lahore. The support of this
complex engineering problem was provided by the Dr. Zaka Emaad, Assistant Professor at
Mining Engineering Department of UET, Lahore.
Firstly, we would thanks to Allah Almighty for protection and ability to do work. We owe a
tremendous debt of gratitude to our instructor and guider, who guided us about the research
before who encouraged and direct me. His challenges brought this work towards a completion.
It is his supervision that this work came into existence. For any fault we take full responsibility.
We are also deeply thankful to our informants. Their names cannot be disclosed, but we want
to acknowledge and appreciate their help and transparency during my research. Their
information has helped me complete this report.
We are also thankful to our friends and fellow whose challenges and positive critics, provided
me new ideas to the work.

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Abstract:

Room and pillar mining are a method of underground mining which is mostly used in salt mines
where a long wall of salt is mined in a single slice. The salt mine under study is following the
longwall mining method to mined out the salt. In this report, we will discuss about the mine in-
situ properties and assessment of field stresses. On the basis of field situations, the mine
opening will be design and the mine pillars for the room and pillar mining method will be
designed. Intact properties of rock salt were determined from literature. Rock mass properties
was calculated by using Roclab software. In situ stresses were calculated by using
mathematical relations according to given conditions. On the basis of stresses arch shape of an
incline was selected and the pillar dimensions were chosen on the basis of in situ stresses.
Support system was designed on the basis of RMR values. The safety factor will be computed
and the support for disturbed roof will be subjected for safety. The verification of selected
design was done by using phase 2D software. This report contains knowledge about the design
of underground mine opening and pillar as well as stresses assessment. At last, the mine hazards
related to flood and the pillar failure will be discussed and the engineering solutions will be
represented.

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Table of Contents
1. Introduction: ....................................................................................................................... 1
1.1 Location and Coordinates: .......................................................................................... 1
1.1.1. Satellite Imagery: ................................................................................................. 1
1.2 History of Kalabagh: ................................................................................................... 2
1.3 Kalabagh Dam: ............................................................................................................ 2
1.3.1 Planning and Objections: ..................................................................................... 3
1.4 Mineral Deposits: ........................................................................................................ 3
1.4.1 Building Material: ................................................................................................ 3
1.4.2 Chalk: ................................................................................................................... 3
1.4.3 China Clay: .......................................................................................................... 4
1.4.4 Coal: ..................................................................................................................... 4
1.4.5 Dolomite: ............................................................................................................. 4
1.4.6 Gypsum: ............................................................................................................... 4
1.4.7 Iron Ore: ............................................................................................................... 4
1.4.8 Rock Salt: ............................................................................................................. 5
1.4.9 Silica Sand ........................................................................................................... 5
1.5 Kalabagh Salt Mine: .................................................................................................... 5
1.6 Geology: ...................................................................................................................... 6
1.7 Structural Geology & Stratigraphy: ............................................................................ 7
1.7.1 Structural Analysis: .............................................................................................. 8
1.7.2 Stratigraphic Column: .......................................................................................... 8
2. Rock Mass Properties: ....................................................................................................... 9
2.1 Intact rock slat properties: ......................................................................................... 10
2.2 Massive salt properties: ............................................................................................. 11
3 In Situ Stresses: ................................................................................................................ 12
3. Opening Designs: ............................................................................................................. 13
4.1 Shape of Adit:............................................................................................................ 13
4.2 Size of Opening: ........................................................................................................ 13
4.2.1 Dimension: ......................................................................................................... 14
4.2.2 AutoCAD Design: .............................................................................................. 14
4.3 Stresses around openings: ......................................................................................... 14
4.3.1 Radial, Tangential and Shear stress at the boundary: ........................................ 15
4.3.2 Wall Stress: ........................................................................................................ 15
4.3.3 Crown Stress: ..................................................................................................... 15

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 4.4 Safety Factor: ............................................................................................................ 16
4.5 Rock Support:............................................................................................................ 17
4.5.1 Bolt Strength: ..................................................................................................... 17
4.5.2 Bolt Length: ....................................................................................................... 17
4.5.3 Spacing of Bolt: ................................................................................................. 18
4.6 Finite Elemental Model by Phase 2D:....................................................................... 18
5 Pillar designs: ................................................................................................................... 18
5.1 Recovery Rate: .......................................................................................................... 19
6 Ground Control: ............................................................................................................... 20
6.1 Flooding Hazards: ..................................................................................................... 20
3.1.1 Flooding from ground water: ............................................................................. 20
3.1.2 Hazards: ............................................................................................................. 20
3.1 Pillar Failure: ............................................................................................................. 21
3.1.1 Pillar Squeeze: ................................................................................................... 21
3.1.2 Massive Collapses:............................................................................................. 21
3.1.3 Characteristics of pillar failure: ......................................................................... 21
3.2 Engineering Solutions of Pillar failing: ..................................................................... 22
3.2.1 In Shear: ............................................................................................................. 22
3.2.2 In concave: ......................................................................................................... 22
3.2.3 In Convex: .......................................................................................................... 22
4 Results:............................................................................................................................. 22
4.1 CAD View: ................................................................................................................ 23
5 Discussion & Comments: ................................................................................................ 24
6 Conclusion: ...................................................................................................................... 24
7 Video Abstract Link:........................................................................................................ 25
8 References: ....................................................................................................................... 26
9 Web References: .............................................................................................................. 27
10 Appendix: ......................................................................................................................... 28

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List Tables:
Table 1: The table shows intact rock properties ...................................................................... 10
Table 2 The table shows massive properties of rock salt......................................................... 11

List of Figures:
Figure 1: Position of Kalabagh on the Geographic Map ........................................................... 1
Figure 2: Satellite image of Kalabagh ....................................................................................... 1
Figure 3; Location of Kalabagh Dam on map ........................................................................... 2
Figure 4: Satellite imagery of Kalabagh Salt mine .................................................................... 6
Figure 5: Geological map between Western salt range and Kalabagh hills showing its tectonic
features in the region .................................................................................................................. 7
Figure 6: Tectonic map of north-west Pakistan MKT=Main Karakoram Thrust, MMT=Main
Mantle Thrust, MBT=Main Boundary thrust, MFT=Main Frontal thrust, SF=Surghar Fault
and TIRT=Trans Indus Ranges Thrust ...................................................................................... 7
Figure 7: Geological map of Kalabagh Hills, Mianwali District, Punjab, Pakistan. ................. 8
Figure 8: Stratigraphic column of Kalabagh Hills ..................................................................... 9
Figure 9: The figure is showing major and minor principle stresses Figure 10: The
picture shows massive properties............................................................................................. 11
Figure 11: The normal and shear stresses ................................................................................ 11
Figure 12: CAD design of opening .......................................................................................... 14
Figure 13: The chart for rock bolt length ................................................................................. 17
Figure 14: The Finite elemental model of opening .................................................................. 18
Figure 15: The mine layout revealing pillar recovery dimensions .......................................... 20
Figure 16: The mine opening design ....................................................................................... 23
Figure 17: The CAD design of mine layout............................................................................. 24
Figure 18: The Rock mass rating table .................................................................................... 28

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1. Introduction:
Kalabagh is a town of Mianwali District and situated in Punjab province of Pakistan It is the
Seat of the Nawab of Kalabagh. Whose state before the Sikh invasion stretched from the
Modern-day districts of Bannu, Dera Ismail Khan, Bhakkar and Mianwali to some parts of
chakwal district. The Modern-day city of Kalabagh gradually sprang up around the Fort and
Citadel of The Nawab of Kalabagh. The Fort locally known as the Qila Nawab Sahib, is still
the residence of the Present Nawab of Kalabagh. It is famous for its red hills of the salt range
and the scenic view of the Indus River traversing through the hills. It also produces handicrafts,
especially footwear and Makhadi Halwa. This area is also very debatable in the government of
Pakistan as well as most construction and mining companies because of the Planning of Dam
and mineral reserves at there.
1.1 Location and Coordinates:
It is exactly located on the western bank of the Indus river and the part of Isakhel tehsil. Its
coordinates are 32.966ºN to 71.553E.

Figure 1: Position of Kalabagh on the Geographic Map

1.1.1. Satellite Imagery:

Figure 2: Satellite image of Kalabagh

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1.2 History of Kalabagh:
Kalabagh was the city ruled by Nawabs for 900 years, since the time of Sultan Mahmood of
Ghazni. During the British Raj kalabagh was not made a princely state by the British. It was a
jagir that ruled by Nawabs since 1100, while most of the other states were mere inventions of
the British. The was taken by his ancestors who were Awam of Arabs origin. He had proud of
his Awam origin. He always maintained that he was descended from an individual named was
Qutb Shah, a ruler of Herat and a general in the army of Mahmood of Ghazni. Kalabagh was
settled by its Nawabs when Nawab Malik Surkhuroo Khan made it his summer capital while
unmoving keeping his ancestral seat of the Great fort of Dhan Kot. Later the Nawabs built a
citadel, which is still the seat of the present Nawab of Kalabagh, who is also the recognised
chief or Sardar of the Awan Tribe, around which the city later sprang up. Kalabagh remained
a famous Awan stronghold in the district and Nawab Malik Atta Muhammad Khan (father of
Nawab Malik Amir Mohammad Khan) was declared "Khan Bahadur" during the British
colonial period just like his father before him. Nawab Malik Amir Mohammad Khan became
governor of West Pakistan later on. Majority of residents of Kala Bagh are Bangi Khel
Khattak, Niazi or Awan.
1.3 Kalabagh Dam:
The Kalabagh Dam site is located about 194 km d/s of Tarbela dam and 16 km u/s of Kalabagh
town. The dam site is linked by a railway line and road which are passing near a distance of
approximately 13km with the site. Catchment area of River Indus at the Kalabagh dam site is
286, 194 sq. km. The average annual flow of River Indus is 138.69 MAF at the Kalabagh dam
site. In kharif season, 83.6% of the discharge occurs and 16.4% occurs at the Rabi season. Site
exploration and soil investigation started in 1953 by the mutual cooperation of World Bank.
Later the construction of KBD project was expected to be started in 1987 and should be
completed in 1993. But unfortunately, it was not constructed because of many reasons. And
one of the main reasons is the political criticism. Finally, in 1980, a team of World Bank finally
confirmed that site C is best for constructing the dam from both economic and technical point
of view but the site A and B were rejected. Because main construction material required at Site
A was concrete as the sandstone would not make an adequate aggregate when crushed. Due to
this reason, the dam was estimated to be much expensive and Site B was having a fault line
and hence rejected by the other experts. The Kalabagh Dam site is shown in the figure below
on Pakistan map.

Figure 3; Location of Kalabagh Dam on map

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1.3.1 Planning and Objections:
Kalabagh Dam project was planned in 1984 with the collaboration of World Bank’s UNDP for
the client, WAPDA of Pakistan. But some of the objections were made by KPK and Sindh
provinces. KPK criticises because due to its construction, Nowshehra will get flooded, Swabi,
Mardan and Pibi scarp will be water logged and many people of KPK will be displaced. Sindh
criticises because it will convert Sindh to desert and land of lower Sindh will be affected by
the intrusion of salt from sea.
1.4 Mineral Deposits:
The area of Kalabagh is enrich by some mineral reserves that are beneficial in extraction some
are in less ratio but some of them are still in exploitation and beneficial. These mineral deposits
are explained as below;

1.4.1 Building Material:

Building materials have been classified into the following three categories:

• Igneous and metamorphic rocks

• Sedimentary rocks
• Gravels and sand

In Punjab only igneous rocks and sedimentary rocks are available which can be used as building
stone. The formation is pre-dominantly composed of grey slate, red and grey quartzite with
minor amounts of conglomerate. These metasedimentary rocks are interlayered with Andisite.
Rhyolite and Tuff beds. The sequence of intruded by basic igneous rocks of dibasic
composition. The basic dykes contain gold and silver in minor amounts. The rocks of kirana
group can be placed in the late Pre-Cambrian age. Great members of small to large crushing
plants have been installed in the area producing crush which is used in building and roads
Limestone is abundantly found in Punjab. Besides its industrial uses (cement manufacturing,
lime making, soda ash manufacturing, etc) it is also being used at vast scale as building material
in crushed from. Margallah crush limestone market is well known. Also, limestone, in raw and
crushed from, in Districts of Attock, Rawalpindi, Jhelum, Chakwal, Khushab, Mianwali, and
D.G.Khan is being used as building stone
Purple sandstone, magnesian sandstone and other sedimentary rocks exposed in the Salt Range,
particularly in its eastern half, are quite suitable for use as building stone. The magnesian sand
tone is quarried near jutana and at Chammal. There are other places in the Salt Range where
different types of rocks have been quarried for use as road blast aggregate stone, etc.
1.4.2 Chalk:
Chalk is soft, earthy, fine-grained white to grayish limestone of marine origin, composed
almost entirely of biochemically derived calcite that is formed mainly by shallow-water
accumulations of minute plants and animals, in particular, coccoliths and foraminifers,
globigerina and textalaria. A variety of limestone formed from pelagic or floating organisms is
very fine grained, porous and friable. It consists almost entirely of calcite. The rock is made up
of calcite shoals of micro-organisms partially cemented by amorphous calcite. Chalk is used
for cements, powders (as soft abrasive and polishers) crayons and fertilizers Chalk deposits are
mainly formed in the limestone accumulation, which can be found in Khushab, Mianwali, D.G.
Khan and Rajanpur Districts.

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1.4.3 China Clay:
China Clay is composed of kaolin, halloysite and other similar clay that have been processed
for the manufacturing of chinaware. It is a mineral of clay family. The kaolin clays are formed
as hydrothermal alteration products of feldspars, feldspathoidal rocks as residual weathering
deposit and as sedimentary deposits of ice melt water. China clay is found in Punjab in Districts
of Chakwal, Khushab, Mianwali, Attock and D.G. Khan.
1.4.4 Coal:
Coal is the general name for the naturally occurring commonly stratified rocklike brown to
black derivative of forest vegetation that accumulated initially in sedimentary rocks. In Punjab
Province huge coal deposits are found in the Salt Range. The main coal deposits are found in
Districts of Attock, Jhelum, Chakwal, Khushab and Mianwali. Thickness of coal seams, in
Punjab, generally ranges from a few centimeters to 1.5 meters. The coal found in Punjab is of
sub-bituminous quality. Most coal deposits and associated carbonaceous shales are found in
the Salt Range and Trans Indus Range (Surghar Range) within the Patala Formation and Hungu
Formation of Paleocene age. Limited occurance is available in Tobra Formation of Permian
age.
1.4.5 Dolomite:
Dolomite, when pure, has equal parts of calcium carbonate and magnesium carbonate Dolomite
occurs in various colures ranging from nearly white to nearly black; also, in various shades of
brown, red and yellow. Dolomite is used for building statuary monumental and ornamental
purposes as a source of magnesia and as refractory material.
The main deposits include Barbara deposits of Kuch near Kalabagh in District Mianwali. The
Dolomite deposits are also found near Datta Nala (about 11 km North East of Makerwal).
Doya-Lunda, Normia and Punnu (Near coal mines of Mulla Khel) and near Burikhel in District
Mianwali. The thickness of the deposit’s ranges from 200 to 300 ft. The dolomite deposits of
District Mianwali are mainly found in Kingriali Formation of Triassic age. The deposits of
dolomite are found near Wagh and Nila Wahn in Districts of Chakwal & Khushab which are
found in the Salt Range Formation of Pre-Cambrian age and Jutana Formation of Cambrian
age. Dolomite deposits are also available in Kala Chitta Range of Kingriali Formation in
District Attock.

1.4.6 Gypsum:
Gypsum is a hydrated Sulphate of calcium. Gypsum occurs as tabular or prismatic crystals:
commonly in cleavable. Columnar, granular, fibrous, foliated or earth masses, its hardness is
two, and specific gravity, 2.2 to 2.4. It is often mixed with clay, sand, organic matter. The
deposits of gypsum also occur in the Salt Range in District of Jhelum, Chakwal, Khushab and
Mianwali.
1.4.7 Iron Ore:
Although iron is found in a number of minerals including sulphides, oxides, hydroxides,
carbonates and silicate, the ores of iron are restricted to hematite, magnetite and siderite.

The Kalabagh iron ore deposits are the largest known deposits in Pakistan of low-grade iron
ore that deposits are located in the Surgher Range in Trans Indus (Across River Indus) from
Kalabagh to Makarwal over a stretch length of 75 KM in District Mianwali. These deposits are
sedimentary in origin and associated with Chichali Formation of Cretaceous age. The Chichali
Formation is overlain by the Lumshival Formation and above Lumshiwal Formation coal

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bearing Hangu Formation of Paleocene age lies in Makarwal area. Outcrops of the deposits are
exposed at various places throughout stretch length from Kalabagh to Makarwal.

Much work has been done on Kalabagh iron ore deposit in the past, by M/S Pakistan Mineral
Development Corporation. The Kalabagh iron ore can be classified into two broad types on the
basis of mineralogy. These are the Kuch type (chomosite-siderite) and the Chichali type
(glauconite-siderite). A transitional type of ore is also present and is represented by the ore of
Chuglan and Tolamangli.

1.4.8 Rock Salt:

It is one of the most important members of the evaporate series of minerals. It crystallizes in
the cubic system; Crystals are generally cubing or in combination with the octahedrons; also,
skeletal or hopper shaped.
It occurs in association with gypsum, anhydrite, dolomite, and red marl. The rock salt is
occurring in whole of the Salt Range. However, at present it is being mined extensively at
various places such as Khewra, Nurpur, Jutana, Warchha, Batmach, Chuki Wahn, Dodha
Wahnm, Goliwali and Kalabagh in District of Jhelum, Chakwal, Khushab and Mianwali. The
salt mining is being done by M/S Pakistan Mineral Development Corptration, M/S Punjab
Mineral Development Corporation and some private parties. Besides rock salt of Salt Range,
lake salt is also being recovered under the process of solar evaporation from various salt lakes
in District Rahim Yar Khan.

1.4.9 Silica Sand

The chief constitution of silica sand as the name suggests is silica (SiO2) (over 93%). Iron and
alumina are also present as impurities.
The main type of silica sand deposits is stream or fluvial, marine and lake, glacial and residual.
Windblown deposits are of relatively minor importance. Also, silica sand deposits vary greatly
in composition, thickness, aerial extent and shape.
In Punjab good quality silica sand deposits occur in the western Salt Range and Trance Indus
Range i.e, Surgher Range and Khisore Range in the District Mianwali Geologically the deposits
are associated with the Datta Formation of Jurassic age. These deposits especially found in
Surgher Range are believed to be extensive and suitable for the manufacturing of all types
glass. Silica Sand deposits are found at some location from Moza Bazar to Kala Bagh (District
Mianwali) in the western Salt Range. These deposits are however of low economic value as
same are less friable and contain impurities.
1.5 Kalabagh Salt Mine:
The Salt Range is a hill system in the Punjab province of Pakistan, deriving its name from its
extensive deposits of rock salt. The range extends from the Jhelum River to the Indus, across
the northern portion of the Punjab province. The Salt Range contains the great mines
of Mayo, Khewra, Warcha and Kalabagh, which yield vast supplies of salt. Coal of a medium
quality is also found.
Kalabagh salt mines are located in district Mianwali, near right bank of Luni Wahan nullah.
The seams are irregular and twisted and production from these mines is small. Salt is excavated
by Room and Pillar method. Some of the chambers are more than 80 meters deep where the
salt is still mined manually. There are 13 different kinds of salt seams with different shades of
colour. Actual old mines are located near the village known as Wanda Kukranwala.

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Location: 296km from Islamabad or 50km from Mianwali
Leased Area (Two): 3,837.81 acres
Geological Horizon: Pre-Cambrian
Purity of salt Average: 96%
Shades of salt: White and Pink
Total Resources: 28,503 tons Production (1999-2000) 200,213 tons
Production: 165,337.500 tons (2018-19)
Sales: 165,337.500 tons (2018-19)

Figure 4: Satellite imagery of Kalabagh Salt mine

1.6 Geology:
The Kalabagh hills represents the Trans-Indus extension of Western Salt Range, lying north of
thee Kalabagh City Mianwali District. These hills occupy important structural transect between
the Western Salt Range and Surghar Range, and can serve to the structural relationship between
these two important tectonic orogens of northern Pakistan. These is a deformation associated
with the Kalabagh Fault Zone that extends 120 Km from the southwestern corner of the Salt
Range near Khushab to the Southern Kohat Plateau, bordering the northern flank of Kalabagh
hills. This fault zone terminates the west-southwest trending Salt Range Thrust front on the
west, extending up to north of the Surghar Range into the southern margin of the Kohat Plateau.
Kalabagh Faults is present in the map of the active faults of Pakistan. According to McDougal
& Khan (1990) the Kalabagh Fault Zone is formed by transpressive right lateral strike-slip
movement along the Wastern Salt Range allochthon in northern Pakistan. Lateral ramping from
a decollement thrust along an Eocambrian evaporite layer produced north-north west to north
west trending folds and north east to north dipping thrust faults in a topographically emergent
zone up to 10Km wide. Along the Kalabagh Fault 12-14 Km right lateral offset has been
interpreted.

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 Figure 5: Geological map between Western salt range and Kalabagh hills showing its tectonic features in the region

1.7 Structural Geology & Stratigraphy:

The India-Eurasia collisional event of South Asia begun in middle to late Eocene producing
the world spectacular Himalayan ranges. The northward under thrusting of the Indian Plate
underneath the Eurasion Plate have resulted in the formation of a south-directed thrust system
that constitutes the major tectonic fabric of Pakistan. The Salt range Thrust along with the
Trans-Indus Ranges Thrust is the southern most of the Himalayan thrust system of the north
Pakistan and places Paloezoic to Eocene platform sequence over the underformed alluvium
covered Punjab Foreland in the south.

Figure 6: Tectonic map of north-west Pakistan MKT=Main Karakoram Thrust, MMT=Main Mantle Thrust, MBT=Main
Boundary thrust, MFT=Main Frontal thrust, SF=Surghar Fault and TIRT=Trans Indus Ranges Thrust

The oldest rock units outcropping in the Kalabagh hills belongs to the Precambrain salt Range
Formation and appear in fault contact with the younger platform and molasses sediments shown
in figure 5.

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1.7.1 Structural Analysis:
The distribution of structural geometries within the Kalabagh hills. A north-northwest trend
with slight deviation at places characterizes the outcropping rocks within the Kalabagh hills.
On the map Kalabagh hills appears as a fault bounded block with normal sense of slip as
indicated by the stratigraphic relationship observed along these faults. Two faults designated
as Kalabagh Fault and Indus Fault mark the eastern flank of the Kalabagh hills is oriented
north-northwest and follows the trace of Chisel Algad. The stratigraphic relationship along the
Kalabagh Fault is well exposed immediately north of the Indus River bank and juxtaposes the
Precambrian Salt Range Formation against the eastward dipping Siwalik Group of Pliocene
age. With the map tracing of Kalabagh Fault the Precambrian Salt Range Formation disappears
northward and the fault runs within the Siwaliks on both sides of the fault. Indus Fault appears
as a splay of the Kalabagh Fault and along this fault the western flank of the Kalabagh hills is
downthrown to the west. West of Indus Fault the Kalabagh Conglomerates form the skyline of
the Kalabagh hills. Underneath the Kalabagh Conglomerated the rocks as old as Permian crop
out in the core of a regional anticlinal structure that comprises several shallow anticlinal and
synclinal folds. The major structure is named as kalabagh Anticlinorium. The Kalabagh
Anticlinorium along with its associated folds is characterized by north-northwest trend and is
detached at the level of Permian rocks. The western flank of the Kalabagh Anticlinorium is
faulted out along a steepy dipping fault named as Kuch fault that brings the Permain-Eocene
strata against the Quaternary Kalabagh Conglomerate in the west. Stratigraphic relationship
along this fault suggests that its eastern side is down thrown towards east. Further west of the
Chighlan Fault, Kuch Tendar Fault appears as the western most bounding fault of the Kalabagh
hills. It is north-northwest oriented and brings Jurassic rocks in faulted contact with Salt Range
Formation. Chighaln, Kuch Tendar and Kuch fault merge to form a single fault zone north of
Kalabagh Town.

Figure 7: Geological map of Kalabagh Hills, Mianwali District, Punjab, Pakistan.

1.7.2 Stratigraphic Column:

The stratigraphic column of the Kalabagh hills is shown below that shows the age of rocks and
their formation existence according to the structure of geology. The stratigraphic succession of

8
the area falls under Zaluch Group at the base overlain by Mainwali, Tredian and Kingriali
formations of Triassic age shown in figure 6.

Figure 8: Stratigraphic column of Kalabagh Hills

2. Rock Mass Properties:

Rock mass property is governed by the properties of intact rock materials and of the
discontinuities in the rock. The behavior if rock mass is also influenced by the conditions the
rock mass is subjected to, primarily the in-situ stress and groundwater. The quality of a rock
mass quality can be quantified by means of rock mass classifications.
Rock mass is a matrix consisting of rock material and rock discontinuities. As discussed early,
rock discontinuity that distributed extensively in a rock mass is predominantly joints. Faults,
bedding planes and dyke intrusions are localized features and therefore are dealt individually.
Properties of rock mass therefore are governed by the parameters of rock joints and rock
material, as well as boundary conditions. The behavior of rock changes from continuous elastic
of intact rock materials to discontinues running of highly fractured rock masses. The existence
of rock joints and other discontinuities plays important role in governing the behavior and
properties of the rock mass.
According to above paragraphs we can find out these properties by testing method at the site
for calculations and by the reports that contains all these rock mass properties done by students
and teacher for the sake of projects and reports on the area. But the company that hired us
wanted all the rock mass properties by a method that is free of cost, so we choose the later
method for our property’s calculations.

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It is quite difficult to find out the all the properties from a single report on the area so we use
different reports data (done in the same area or in the same formation of rock body), one type
was the research work on the rock body of that area by the teachers which is very beneficial
and the other was the students project reports who were assigned the task to calculate the data
of the salt formation, like formation geology and behaviours of the rock which need testing that
is done by the students in the respective institute labourites.
Rock properties are essential to compute in-situ stresses. These include uniaxial compressive
strength, unit weight, Poison ratio, GSI, cohesion, friction and MOD of the rocks. All these
properties acquired by the literature whose references are given and the data that was not available
calculated with the help of equations and software like RocLab.
Some of the site conditions are to be assumed on some literature basis because these are not
available at any online source or any research work. The UCS, RQD has been assessed from a
research paper, the displacement rate corresponds to spacing which is 0.01mm/s and the rock is
soft gauge assumed on the basis of rock salt conditions because it is soft rock that has 0.01mm/s
displacement. It led the maximum discontinuity spacing. The strata are dipping at 25ºC with strike
line perpendicular to the axis. So; the essential parameter ratings are;
• The UCS is 6.4MPa = 2
• The RQD is 75.31% = 20
• The spacing of discontinuity rating = 20
• Condition of discontinuity based on soft rock = 0
• Ground water is wet because of salt rock = 7
• The dipping of drive is 25ºC = -2 (favorable)
RMR = 2 + 20 + 20 + 0 + 7 -2 = 47
GSI = RMR -5 = 42
For details, you can check the Appendix.

2.1 Intact rock slat properties:

The rock salt properties obtained by some researchers in lab testing;
Table 1: The table shows intact rock properties

Rock Properties Values

Unit weight 21.3 KN/m3
Poison ratio 0.336
UCS 6.40 MPa
RQD 75.3 %
Elastic Modulus 7212 MPa
GSI 42
RMR 47
Friction angle 40°
Cohesion 4.8 MPa
Tensile Strength 0.3 MPa
Porosity 2.27– 4%
Friction angle 40º

10
 2.2 Massive salt properties:
The rock salt properties of the site condition, these were able to know by using a software
Roclab.

Figure 9: The figure is showing major and minor principle stresses Figure 10: The picture shows massive properties

Figure 11: The normal and shear stresses

Table 2 The table shows massive properties of rock salt

Rock Properties Values

Tensile strength -0.007 MPa
Friction angle 30.63°
Global Strength 1.023 MPa
MOD 13.1951 MPa
Cohesion 0.275 MPa
Tangential Stress 1.069 MPa
Shear Stress 1.264 MPa
Major Principle Stress 3.293 MPa
Minor Principle Stress 0.7084 MPa

11
3 In Situ Stresses:
The stresses possessed by the rock when none of the activity is performed. In field we have to
deal with the in-situ stresses because there is not any intact rock and rock has stresses. When
we do any engineering activity then the in-situ stresses are converted into two sets these are
new stresses produced by the activity or disturbance on the rock.
Types of Stresses:
There are two types of stresses produced are;
• Vertical Stresses σv (it is the stress produced due to the load of overburden)
• Horizontal Stresses σh (it is the stress due to side rock loads (lateral))
The magnitude and direction of these stresses shows a vital role in planning and designing and
tunnels.
Vertical Stresses:
Vertical stress is the stress produced due to the load of overburden lying on the rock. It is shown
by σv. It can be calculated by following formula;

σv = ɣh
where ɣ is the unit weight of the rock and h is the depth.
Horizontal Stresses:
Horizontal stress is the stress due to the presence of side rocks applying lateral load to the
rock. It is denoted by σh. It can be calculated by following formula;
𝜇
σh = kσv K=
1− 𝜇
where K is the constant, and μ is the poison’s ratio.
Calculation of in-situ stresses:
For determining the in-situ stresses, we are given with the overburden of rock mass over the
rock salt ore body i.e. 500ft corresponds to 152.4m. It is a higher depth of rock but for mining
purposes it is not exceptional because we built mine just for the time or mineral extraction and
after it, we close the area, so the safety is providing just according to the mining period.
According to the given condition;
Vertical stress:
ɣ = density × gravity = 2170 kg/m3 × 9.81 m/s2 = 21.3 KN/m3

h = 152.4 m, ɣ = 0.0213 MN/m3

σv = (0.0213) (152.4)
σv = 3.24612 MPa

12
Horizontal stress:
0.336
K= = 0.506
1−0.336
σh = (0.506) (3.24612)
σh = 1.6426 MPa

3. Opening Designs:
The entrance of the underground mine has a shape of it. The shape of adit is selected on some
basis which lead the equipment and workers to enter the horizontal or nearly horizontal
pathway of the mine.

4.1 Shape of Adit:

The adit is the only pathway used for multi purposes such as, providing ventilation, material
haulage, equipment and workers. While designing the opening, the shape of opening is most
significant contemplations of all. There are many shapes of opening such as; Circular,
Elliptical, Horseshoe and Semi-circular etc. Among all these states of opening, the shape to be
selected should be steady as far as stresses. The cross-section shape of the mine opening must
be appropriate to incorporate the predominant land conditions and overburden pressure on it.
The better load-bearing capacity of the rock mass which is to be excavated, the more stability
in design can be assumed with less ground pressure and wall rocks.
The shape is generally depending upon the ore deposit and stresses from external and internal
rocks which should be to uniform around the openings that can make the opening stable and if
not, the support should be provided in the form of rock bolting or anything else for the sake of
stability of opening. Keeping all these situations in mind, the shape selected is ARCH-shape,
a kind of circular opening, which has circular perimeter. The circular perimeter helps to
destress the stress concentration zone and move them away to stable the stress zones, mostly
in the massive tabular deposit when the situation is very stressed as we have assessed from the
in-situ stresses. Both vertical and horizontal stresses are there to disturb the excavation, that’s
why the arch shape is selected. For the depths of about 500ft as we are discussing about same
case, these shapes are mostly usable due to their stability.

4.2 Size of Opening:

The size of opening is mainly designed on the basis of equipment and mining necessaries to be
entered and the zone of influence. The equipment is very necessary to incorporate because if
size is not enough to enter the equipment we are using, the opening design will be the waste so
the appropriate design keeping all dimensions of the mining equipment, opening should be
design. Even opening should not be very large than the equipment size, because in this case,
more excavation will be needed which is not economical and zone of influence will play its
part to disturb the higher span of the opening. In this case, we would need the more support
which lead to uneconomical design. So, these things should be kept in mind designing the
opening.
The complete size of opening comprises of some features which are to be assessed such as;
Side-manway, Equipment rails (shuttle car, haulage truck etc.) Ventilation clearance from top
and side clearance.

13
As, different sizes of underground mining equipment are analysed which can be used in
Kalabagh salt mine such as; Continues minor used for coal seam and soft minerals has 1.8-by-
3.6m size maximum, Haulage trucks have normally 4m width and 2m height, Bolter minor
mostly are 1.8 to 2m are used and shuttle cars are 2.12m in height and 3m in width maximum
that can use here. The Haulage trucks are unable to use in this mine as shuttle car is very
appropriate to use which has less width and height so we will design the opening size with
respect to equipment that can be used. By analysing these parameters opening size is designed.
4.2.1 Dimension:
Base Width = 4m
Out of 4m, 2.5m width is specified for the equipment or machinery which would be passed by
and 0.75m clearance for safety of equipment from walls as well as manway is kept.
Radius = 2.41m
The radius is selected to be normal with respect to the site conditions and passing accessories,
about 3.75m of centre height has been left in it, out of which the maximum 2.75m can be used
by machinery and rest of the distance is fixed for ventilation purpose and clearance from top
and when these features are rounded in the circular form, the radius of 2.41m was appeared
beneficial.
𝜃
Area = S = (𝑟)2 − (𝑟 − ℎ)√ℎ(2𝑟 − ℎ) = 15.23 m2
2
ℎ
Central angle = θ = cos-1 (1 - ) = 4.32º
𝑟
Circular Arc = L = r θ = 10.41 m
4.2.2 AutoCAD Design:

Figure 12: CAD design of opening

4.3 Stresses around openings:

Stresses around openings is necessary to find for the stability of opening. If the stresses are not
in stabilizing condition, the opening would have to be changed or another approach is to
compensate the change with the introduction of a support system.

14
4.3.1 Radial, Tangential and Shear stress at the boundary:
Radial, tangential and shear stresses were calculated from Kirsch’s equations at the boundary
of the excavation. Given below are the calculations:
𝑎2 𝑎2 𝑎4
Radial Stress: σrr = 𝑃2[(1 + 𝑘) (1 − 𝑟2
) − (1 − 𝑘)(1 − 4 𝑟 2 + 3 𝑟 4 )𝑐𝑜𝑠2𝜃]
𝑎2 𝑎4
Tangential Stress: σθθ = 𝑃2[(1 + 𝑘) (1 + 𝑟2
) + (1 − 𝑘)(1 + 3 𝑟 4 )𝑐𝑜𝑠2𝜃]
𝑎2 𝑎4
Shear Stress: σrθ = 𝑃2[(1 − 𝑘) (1 + 2 𝑟 2 − 3 𝑟 4 ) 𝑐𝑜𝑠2𝜃]
4.3.2 Wall Stress:
The stress at the wall are measured by taking θ = 0º, as the stresses are calculated at boundary,
the a/r ratio is equal to 1;
At θ = 0º
σh 3.24612
K= = = 0.506
σv 1.6246
a = 2.28m, r = 2.28m, a/r = 1

σrr
=
3.24612 2.282 2.282 2.284
2[(1 + 0.506) (1 −
2.282
) − (1 − 0.506)(1 − 4 2.282 + 3 2.284)𝑐𝑜𝑠2(0)]

Radial Stress: σrr = 0

2.282 2.284
σθθ = 3.24612
2[(1 + 0.506) (1 +
2.282
) − (1 − 0.506)(1 + 3 2.284 )𝑐𝑜𝑠2(0)]

Tangential Stress: σθθ = 1.6815 MPa

2.282 2.284
σrθ = 3.246122[(1 − 0.506)(1 + 2 2.282 − 3 2.284 )𝑐𝑜𝑠2(0)]
Shear Stress: σrθ = 0
4.3.3 Crown Stress:
The stress at the roof are measured by taking θ = 90º, as the stresses are calculated at boundary,
v
the a/r ratio is equal to 1;
At θ = 90º
σh 3.24612
K = σv = = 0.506
1.6246

a = 2.28m, r = 2.28m, a/r = 1

15
σrr
=
3.24612 2.282 2.282 2.284
2[(1 + 0.506) (1 −
2.282
) − (1 − 0.506)(1 − 4 2.282 + 3 2.284 )𝑐𝑜𝑠2(90)]

Radial Stress: σrr = 0

2.282 2.284
σθθ = 3.24612
2[(1 + 0.506) (1 +
2.282
) − (1 − 0.506)(1 + 3 2.284 )𝑐𝑜𝑠2(90)]

Tangential Stress: σθθ = 8.096 MPa

2.282 2.284
σrθ = 3.246122[(1 − 0.506)(1 + 2 2.282 − 3 2.284 )𝑐𝑜𝑠2(90)]
Shear Stress: σrθ = 0
4.4 Safety Factor:
It is important to check the strength ofvopening. For this reason, we have to compute wellbeing
factor, which gives us a thought that the opening configuration can withstand under the
anxieties. Safety factor calculation is essential to know if the opening is going to sustain the
overburden pressure or not.
If it is less than 1 then it means that the design not safe. If it is greater than 1, it means that it’ll
sustain the respective stress conditions. We use following relation for the calculation of safety
factor:
UCS
Safety factor =
Hoop Stress

Where; UCS= Uniaxial compressive strength Hoop stress= 3σh – σv

UCS = 6.40 MPa
Hoop Stress = 3(1.6426) – (3.24612) = 1.68168 MPa
6.40
Safety Factor = = 3.8
1.68168

The overall safety factor is greater than 1, the adit is stable with respect to in-situ stresses. But
we need to check the safety of opening by its wall and crown stresses.
Uniaxial Compressive strength 6.40
Safety factor in Wall = = = 3.81
Tangential Stress 8.096

Uniaxial Compressive strength 6.40

Safety factor in Roof = = = 0.8
Tangential Stress 1.6815

As, the safety factor has been calculated and it shows that in the roof of the opening, tangential
stress is more than its strength and it will collapse if no support is subject. So, we need to apply
rock bolts in roof in order to stabilize the walls. The wall strength is highly stable, there is no
need to apply support but the walls.

16
4.5 Rock Support:
The rock bolts should be applied that can increase the strength by almost 2MPa according to
the tangential stresses on walls. So, the spacing and length of bolts should be accomplished in
accordance with the conditions. Rock salt is a soft rock, so the bolt will be selected according
to the situation.
The Grouted Rock bolt is suitable for the apparent situation, because untensioned bolt, it is
permanent reinforced system and can be stable in water run-off conditions, it does not affect
the installation. There are some factors on the basis of which rock bolt is selected;
• Bolt length
• Bolt Type
• Spacing of bolt
4.5.1 Bolt Strength:
For the Arch shaped opening, we will design the bolt perpendicular to the joint line by using
formula;
σh (sinαcosα−cos2 αtanɸ)
σp =
tanɸ

α = Angle b/w normal and fracture plane = 90 – 59.73º

σh = horizontal stress = 1.6426 MPa
ɸ = friction angle = 30.63º
σp = Bolt Tension Strength = 0.7898 MPa
4.5.2 Bolt Length:
The bolt length is very necessary to designed that how much long bolt should be reinforced
into the rock that can properly hold its strength. The rock bolt length can be assessed by using
this chart.

Figure 13: The chart for rock bolt length

According to the span of opening, it is about 2.41m radius and central width is equal to 4.82m
corresponds to 15.8 ft. Using this concept, the bolt length obtained from the chart is about =
7.25 ft = 2.21m

17
4.5.3 Spacing of Bolt:
The bolt spacing can be calculated by using this formula;
2L
B=
3
B = bolt spacing
L = Bolt length
B = 1.47m
By this bolt design, it can be estimated that we need to apply 3 bolts in a horizontal raw
throughout the roof span. Then the roof will be stable and it would obtain the maximum
desire strength to resist the tangential stress of roof.

4.6 Finite Elemental Model by Phase 2D:

Furthermore, the stability assessment will be conducted by FEM code in Phase 2D, the wall
and roof stability will be shown that how much support it needs. The main advantage of FEM
code is a possibility of representing stability of heterogeneous rocks with respect to their
assigned materials having different finite properties.
In this finite elemental model, the opening stability has been assessed, according to the
calculations, phase2D revealed a little failure possibility that has been stabled by rock bolts as
we have discussed above. The figure below shows the Phase2D model;

Figure 14: The Finite elemental model of opening

5 Pillar designs:
In room and pillar mining, pillars are necessary to stable enough to support the entire
overburden of strata of the surface. Local stability in the form of stable pillar rib and roof make
a safe environment for working. Pillar stability is one of the most prerequisites for safe working

18
condition. In case of unstable pillars, roof span fails the pillar and lead to the collapse of roof
if more pillar fails than one.
Pillar design is generally carried out by configuring the pillar strength and stress, and then size
of the pillars so that an adequate margin exists between the expected pillar strength and stress.
The pillar width and height of the pillar should be selected while keeping the fact that it has to
bear the overlying burden of strata with respect to its strength and also gives maximum
recovery. The safety is calculated in case of pillar stability by average strength of pillar (UCS)
to applied pillar stress σp on them.
USC
Factor of Safety =
Average pillar Stress σp

When designing a mine pillars, the safety factor is critical to stability, because it should must
compensate for the inconsistency and ambiguity related to pillar strength and stress and
variable dimensions of rooms and pillars. The selection of an appropriate safety factor may be
based on a subjective assessment of pillar performance.
In this case we are arranging the mine layout with square pillars, as roof has some high stress
than the rock salt strength in such case, the square pillar has more span area to bear the
respective roof stresses. In order to calculate the factor of safety, we need to calculate the
average pillar stress by using different pillar dimensions to make it confirm that which one is
stable with respect to the rock strength.
UCS = 6.40 MPa
Opening width = 4m
Pillar Width = 12m
The pillar width has been selected by hit and trial method to safe the pillar. The best width
range was taken from some papers.
𝑤𝑜+𝑤𝑝
σp = pzz [ ]2
𝑤𝑝
4+12 2
σp = 3.24612[ ]
12

𝛔𝐩 = 𝟓. 𝟕 𝐌𝐏𝐚
6.40
Safety Factor =
5.7
v
Safety Factor= 1.12
5.1 Recovery Rate:
In the mining phases, it is necessary
v to estimate the percentage recovery of extraction
of mineral ore. Mathematically, it is defined as the ratio of mineral extracted to the total
mineable reserve in the deposit.
Total Reserves−Mined mineral
Formula: Recovery Ratio = × 100
Total Reserves

19
 Figure 15: The mine layout revealing pillar recovery dimensions

Area of Pillar = 12 × 12 = 144m2

Total Area around pillar and crosscuts = (12 + 2 + 2) × (12 + 2 + 2) = 256m2
256−144
= × 100
256

Recovery Rate = 43.75%

6 Ground Control:
There are some risk factors with respect to ground control that can lead to flooding and pillar
failing in mine. In this section, we will discuss about hazards of flooding in level and pillar
failing and their solutions;

6.1 Flooding Hazards:

Flooding in level are hazardous which can fill the water in working areas, sumps, and all other
mining areas, the major source of flood is the ground water.
3.1.1 Flooding from ground water:
The geology of an area will have a major impact on potential flooding from groundwater.
Nearly all rocks in the upper part of the earth’s crust contain pores or voids. How water moves
through the rock will depend on:
• Porosity – rocks with a relatively large proportion of void space are porous.
• Permeability - how interconnected are the voids which allows water to flow through
the rock.
• Groundwater flooding occurs when water levels in the ground rise above surface
elevations due to increases in rainfall or reductions in the amount of water taken from
any of the rock aquifers. This is most likely to occur in low-lying areas underlain by
permeable rocks.
3.1.2 Hazards:
• Rise of typically high groundwater levels to extreme levels in response to extreme
rainfall.

20
 • Rising groundwater levels in response to reduced groundwater abstraction in a mining
area (termed mine water rebound).
• Enter to the working side and harm the ore quality to be extracted.
• In the rock salt mine, the ground water can become a flood and cause to induce acidic
behaviour of rock salt as chemically combined with water.
• Subsidence of the ground surface below the current groundwater level.
• Rise of groundwater level in aquifers in hydraulic continuity with high in-bank river
levels or extreme tidal conditions.
• Faulty borehole headwork or casings causing upward leakage of groundwater through
confining layers driven by artesian heads.
• Rise of groundwater levels due to leaking sewers, drains and water supply mains.
• Increases in groundwater levels and changed flow paths due to artificial obstructions or
pathways, and loss of natural storage and drainage paths.
• Inundation of trenches intercepting high groundwater levels.

3.1 Pillar Failure:

In room and pillar mining, roof and floor converge by two components, the vertical
deformation of the pillars because of the weight of the overlying strata; and the local sag or
heave of the immediate strata. There are some factors that affect the convergence of salt in
room and pillar mining;
• Time
• Depth below surface
• Extraction ratio
• Pillar height
• Geological structure of salt
• Temperature & Humidity
Proper Pillar design is a vital approach to mine stability. There are two main types of pillar
failing but have their own situations
3.1.1 Pillar Squeeze:
Pillars squeeze out when they are small to carry a heavy load, the load gradually transferred
and they turn fail. It can lead to the closure of entries; a small failure can occur in hours and
days and can move up to closure of entire panel and a heavy loss can occur.
3.1.2 Massive Collapses:
A rapid pillar failure and involves large areas termed as massive collapses. It has powerful
effect and can be a disparaging air blast. Data collected at the failure sites of massive collapse
in 1980’s incident occurred in West Virginia, which indicate that the pillar width-to-height
(w/h) ratio was 3.0 or less, and the ARMPS SF was less than 1.5. Such situations occur most
often in worked out areas where pillars have been split.
3.1.3 Characteristics of pillar failure:
Cascading pillar failure generally exhibits the following characteristics;
➢ Extraction ratio are usually more than 60%. High extraction ratio will move the pillar
stress to peak value and provides sufficient enlargement room for pillar failure.

21
 ➢ For non-metal mine failures width-height ratio of pillars should always be less than 2.
Low width height ratio will cause the failed pillar to extend into abreast openings and
they will have little residual load bearing capability.
➢ The number of pillars should be at least 5 or more than 10 which means pillars are
capable to reach their branch area load.

3.2 Engineering Solutions of Pillar failing:

Pillar failing is one of the serious problems mostly in room and pillar mining as we are
discussing about Kalabagh salt mine which is containing room and pillar method of mining, it
is necessary to take some solution to avoid and prevent these failures and losses. Pillar failure
has been there in each condition, as in shear, in concave and also in convex shape pillar
conditions.
3.2.1 In Shear:
In the inclined orebody deposit, the pillars are loaded with compression and shear, with unequal
stress distribution on pillars. Mostly pillars become weaken when the strata inclined at more
than 15º. There are few techniques which can solve this issue are given below;
➢ In this case, extraction ratio of the pillar should be 0.5 or 1 and maximum can lead to
1.5 which can bear the stress distribution. The increase in extraction ratio can reduce
the strength of pillars in more inclination than 15º and increasing ratio can bear up to
40º inclination.
➢ The roof bolting is also applicable in this situation, because the lower side of strata have
more load on pillar where the roof bolting can be used if load is more than pillar
strength.
3.2.2 In concave:
When the overburden is above the 330m then the load on the roof increases results in the form
of two types of pillar failure;
One is concave which occurs due to rock destruction from the sides of the pillar which cause
the pillar to be thinner from the centre and finally results in the low roof support that would
made the room collapse.
➢ We can control concave pillaring by doing the strapping method. The method of
strapping pillars using mesh and cabling seems useful for stabilizing individual pillars
in areas where most of the other pillars are stable and the total mining spans are small.
3.2.3 In Convex:
In convex, the phenomenon is same but if the width to height ratio of pillar is good but the
overburden stress is higher than the pillar start expanding from the sides of the pillar also results
in lowering the support of the roof.
➢ The convex pillaring can be controlled by the strapping method and also by the bolting
in the pillar but the strapping method is better in the enhancement the of the pillar
strength.

4 Results:
For the room and pillar salt mining operation, the field conditions were assessed, on the basis
of which in-situ stresses were determined;

22
Vertical Stress = 3.24612 MPa
Horizontal = 1.6426 MPa
On the basis of equipment and zone of influence the opening was designed whose dimensions
are presented in the figure below;

Figure 16: The mine opening design

The tangential stresses were calculated on roof and wall.

Roof = 8.096 MPa
Wall = 1.6815 MPa
The safety factor for both roof and wall were calculated and the roof was slightly unstable;
Safety factor of wall = 3.8
Safety factor of roof = 0.8
The support was needed to fit in the roof and the rock bolt was designed for this, the grouted
anchor bolt was needed with 2.21m length and 1.47m spacing. The number of 3 bolts were
needed to fit in the row throughout the roof for stability. Then this stability was assessed by the
Phase2D software which interpreted that in the stable mine opening.
Then the mine pillar was designed for the safety factor 1.12 and their dimensions were 12-by-
12m square which was stable. The recovery ratio was calculated which was 43.75% and that is
a better recovery ratio. The complete mine layout has been shown below.

4.1 CAD View:

The mine layout showing pillars and rooms using AutoCAD is drawn;

23
 Figure 17: The CAD design of mine layout

5 Discussion & Comments:

➢ The field conditions were given with strata dipping at 25º. When the stresses were
calculated, the roof was unstable with safety factor 0.8 but due to the dipping of strata
at a particular dip, the un-stability was not highly effected, it was revealed by Phase2D
model.
➢ In case of dipping strata, the rock bolt is designed in this report but in the FEM model,
the little support is needed only due to the stress concentration outside the mine. That’s
why, only 3 bolt patterns are selected for this particular case.
➢ The square pillar is more stable in soft rock mines because they distribute the load
equally. The safety factor of the pillar should be high enough that it does not fail the
roof when the roof is un-stable in the mine. But in the case of dipping of strata and the
high friction angle, then the roof has some time to be in the stable zone, so we can apply
support in the particular time if needed.
➢ The recovery ratio of the mine is depending on the pillar sizes. If the pillar sizes are
large for the sake of stability, the recovery will be less, so we should leave the optimum
size of pillar and some manual support should be installed in case of failure issue, but
do not leave much higher pillar size in case of only failure doubts because if there is
stable conditions, it will reduce the recovery.

6 Conclusion:
In this report we concluded that, the arch shape opening is more stable than straight wall shapes
because it transforms the stress concentrations and make the opening stable. We found the in-
situ stresses to understand the stress condition in that area, on the basis of this we design the
shape of opening and pillar for mining. The opening designed and the roof was slightly unstable
but due to circular shape less impact showed by Phase2D model and only a short bolt support
was needed for its stability. The field stresses were high on the soft rock but the opening shape
determines the stability and transport facility of equipment and manway. In the roof case
because strata were dipped at an angle so the little un-stability was there that was supported by
Grouted Anchor bolt which is suitable for permanent reinforcement.
In the room and pillar mining, pillar is designed but keeping in mind the roof stresses that the
pillar can bear and because stable for the long-time of mining. The safety factor of 1.12 was
24
selected for square pillar because square pillar equally distributes the load on it. Using this
phenomenon, the pillars are designed and a good recovery rate was reached for square pillars
in mine. The room and pillar method help us to reduce the stress in high stress scenario, but it
gives us the less recovery. In case of pillar failure, such as shear, concave and convex, some
solutions are presented i.e. by keeping extraction ratio from 0.5 to 1.0, roof bolting inclined to
joint, pillar bolting and strapping by meshing and wires.

7 Video Abstract Link:

https://youtu.be/309E7YmaAkw

25
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Mines,” Proc. 25th Int. Conf. Gr. Control Mining. Morgantown, WV West Virginia
Univ., pp. 354–361, 2006.
[9] C. Mark, F. Chase, and D. Pappas, “REDUCING THE RISK OF GROUND FALLS
DURING PILLAR RECOVERY C. Mark F. Chase D. Pappas,” Prevention, pp. 1–9,
2002.
[10] G. S. Esterhuizen, D. R. Dolinar, and J. L. Ellenberger, “Pillar and roof Span Design in
Stone Mines,” Dep. Heal. Hum. Serv. NIOSH, p. 75, 2011.
[11] E. Esterhuizen, C. Mark, and M. M. Murphy, “The ground response curve, pillar
loading and pillar failure in coal mines,” Proc. - 29th Int. Conf. Gr. Control Mining,
ICGCM, pp. 19–27, 2010.
[12] J. Mgumbwa, F. T. Suorineni, and P. K. Kaiser, “Failure mechanisms of orebodies
under shear loading,” no. October, p. 8, 2011.
[13] “TOWARD PILLAR DESIGN TO PREVENT COLLAPSE OF ROOM-AND-
PILLAR MINES R . Karl Zipf , Jr . Chief , Catastrophic Failure Detection and
Prevention Branch,” 2001.
[14] A. Singh, C. Kumar, L. G. Kannan, K. S. Rao, and R. Ayothiraman, “PT NU SC,”
Eng. Geol., p. #pagerange#, 2018, doi: 10.1016/j.enggeo.2018.07.008.
[15] “No Title,” vol. 5, no. 5, pp. 213–216, 1993.

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9 Web References:
• Wikipedia the free Encyclopeida. (n.d.). Retrieved from
https://en.wikipedia.org/wiki/Kalabagh
• http://www.kotfatehkhan.pk/kalabagh.html
• http://punjabmineralcompany.pk/kalabagh/
• https://www.punjab.gov.pk/mnm_dimop
• http://www.rocksaltproducts.com/himalayan-salt-mines.html
• http://pmdc.gov.pk/?p=KalabaghSaltMines
• https://www.google.com/maps/@31.5968086,74.3470166,15z
• https://www.rocktechnology.sandvik/en/products/underground-loaders-and-
trucks/underground-
trucks?msclkid=4646dde9d2d21e12fa688314fa94782d&utm_source=bing&utm_med
ium=cpc&utm_campaign=Load%20and%20Haul&utm_term=%2BTruck%20%2BUn
derground&utm_content=Underground%20Trucks
• keisan.casio.com/exec/system/14407397055469#!
• Stability Analysis of Khewra Salt Mine, Pakistan, by Project Advisor: Muhammad
Akram, Members; Rashid Latif and Yasir Afzal, University of Engineering and
Technology, Lahore, 2010.
• Lecture Notes, Dr. Zaka Emad, Assistant Professor Mining Engineering Department,
University of Engineering anf Technology, Lahore.
• http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S2225-
62532017000600006

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10 Appendix:

Figure 18: The Rock mass rating table

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