Mining structures -- Underground structures

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ISO/DIS 23872 - Mining structures -- Underground structures
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DRAFT INTERNATIONAL STANDARD
ISO/DIS 23872
ISO/TC 82 Secretariat: DIN
Voting begins on: Voting terminates on:
2021-01-06 2021-03-31
Mining structures — Underground structures
ICS: 73.020
IMPORTANT — Please use this updated version dated 2020-11-17, and
THIS DOCUMENT IS A DRAFT CIRCULATED
discard any previous version of this DIS. Note that we removed the
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
reference to a consultation with ISO/TC 127.
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
This document is circulated as received from the committee secretariat.
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STANDARDS MAY ON OCCASION HAVE TO
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
Reference number
NATIONAL REGULATIONS.
ISO/DIS 23872:2021(E)
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
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PROVIDE SUPPORTING DOCUMENTATION. ISO 2021
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ISO/DIS 23872:2021(E)
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© ISO 2021

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ii © ISO 2021 – All rights reserved
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ISO/DIS 23872:2021(E)
Contents Page

Foreword ..........................................................................................................................................................................................................................................v

Introduction ................................................................................................................................................................................................................................vi

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 2

3 Terms and definitions ..................................................................................................................................................................................... 2

4 Symbols .......................................................................................................................................................................................................................... 5

5 Materials ....................................................................................................................................................................................................................... 6

5.1 Underground storage ........................................................................................................................................................................ 6

5.2 Concrete ........................................................................................................................................................................................................ 6

5.2.1 Standards................................................................................................................................................................................ 6

5.2.2 Target strength .................................................................................................................................................................. 6

5.2.3 Plums ......................................................................................................................................................................................... 6

5.2.4 Special requirements for underground application .......................................................................... 6

5.2.5 Water quality ....................................................................................................................................................................... 6

5.2.6 Durability ............................................................................................................................................................................... 7

5.3 Steel .................................................................................................................................................................................................................. 7

5.3.1 Standards................................................................................................................................................................................ 7

5.3.2 Special requirements for underground application .......................................................................... 7

5.3.3 Durability ............................................................................................................................................................................... 7

5.3.4 Timber ...................................................................................................................................................................................... 8

6 Nominal loads .......................................................................................................................................................................................................... 8

6.1 Operating loads ...................................................................................................................................................................................... 8

6.1.1 General loads ....................................................................................................................................................................... 8

6.1.2 Spillage loads ...................................................................................................................................................................... 8

6.1.3 Air pressure loads ........................................................................................................................................................... 8

6.1.4 Thermal loads ..................................................................................................................................................................... 9

6.1.5 Loads on box fronts ....................................................................................................................................................... 9

6.1.6 Loads on high pressure bulkheads ................................................................................................................10

6.1.7 Liquid pressure ..............................................................................................................................................................11

6.1.8 Loads on pipe supports ...........................................................................................................................................11

6.2 Ground displacement loads ......................................................................................................................................................11

6.2.1 Initial relaxation ............................................................................................................................................................12

6.2.2 Long-term ground displacement ....................................................................................................................12

6.2.3 Sudden ground displacement ............................................................................................................................12

6.3 Seismic loads..........................................................................................................................................................................................12

6.4 Emergency loads ................................................................................................................................................................................12

6.4.1 Explosion loads ..............................................................................................................................................................12

6.4.2 Air blast loads ..................................................................................................................................................................13

6.4.3 Mud-rush loads ..............................................................................................................................................................13

6.4.4 Vehicle impact loads ..................................................................................................................................................13

6.4.5 Ground or rock impact loads ..............................................................................................................................13

6.4.6 Emergency load on pipe supports .................................................................................................................13

7 Design procedure ..............................................................................................................................................................................................13

7.1 Risk assessment ..................................................................................................................................................................................13

7.2 Design procedure ...............................................................................................................................................................................14

7.3 Partial safety factors ........................................................................................................................................................................14

7.4 Provision for excavation variations ....................................................................................................................................14

7.5 Design of high pressure bulkheads ....................................................................................................................................15

7.5.1 Types of high pressure bulkheads .................................................................................................................15

7.5.2 Strength requirements.............................................................................................................................................15

7.5.3 Watertightness requirements ............................................................................................................................16

7.6 Design of underground head frames ......... ........................................................................................................................16

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ISO/DIS 23872:2021(E)

8 Construction requirements ....................................................................................................................................................................16

8.1 Transport and storage ...................................................................................................................................................................16

8.2 Anchoring into ground ..................................................................................................................................................................17

8.2.1 Chemical grouted anchors ....................................................................................................................................17

8.2.2 Cementitious grouted anchors .........................................................................................................................17

8.2.3 Mechanical anchors ....................................................................................................................................................17

8.2.4 Shear loads on rock anchors ...............................................................................................................................17

8.2.5 Intact ground ....................................................................................................................................................................17

8.2.6 Fractured ground ...................................................................... ....................................................................................17

8.2.7 Anchor tests ......................................................................................................................................................................17

8.2.8 Lifting or pulling from rock anchors ............................................................................................................18

8.3 Bearing against ground.................................................................................................................................................................18

8.3.1 Intact ground ....................................................................................................................................................................18

8.3.2 Fractured ground ...................................................................... ....................................................................................18

8.4 Excavation tolerances ....................................................................................................................................................................18

8.5 Construction of high pressure bulkheads .....................................................................................................................18

Annex A (informative) Bibliography ..................................................................................................................................................................19

Annex B (informative) Transportation, handling and storage ...............................................................................................20

Annex C (informative) Use of concrete underground.......................................................................................................................21

Annex D (informative) The design and construction of parallel sided high pressure

bulkheads by mortar intrusion ..........................................................................................................................................................29

iv © ISO 2021 – All rights reserved
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ISO/DIS 23872:2021(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards

bodies (ISO member bodies). The work of preparing International Standards is normally carried out

through ISO technical committees. Each member body interested in a subject for which a technical

committee has been established has the right to be represented on that committee. International

organizations, governmental and non-governmental, in liaison with ISO, also take part in the work.

ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of

electrotechnical standardization.

The procedures used to develop this document and those intended for its further maintenance are

described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the

different types of ISO documents should be noted. This document was drafted in accordance with the

editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of

any patent rights identified during the development of the document will be in the Introduction and/or

on the ISO list of patent declarations received (see www .iso .org/ patents).

Any trade name used in this document is information given for the convenience of users and does not

constitute an endorsement.

For an explanation on the voluntary nature of standards, the meaning of ISO specific terms and

expressions related to conformity assessment, as well as information about ISO's adherence to the

World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following

URL: www .iso .org/ iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 82, Mining.
© ISO 2021 – All rights reserved v
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ISO/DIS 23872:2021(E)
Introduction

Many mining companies, and many of the engineering companies which provide designs for mines,

operate globally, therefore this standard was developed in response to a desire for a unified global

approach to the design of safe and reliable structures used in underground mines. The characteristics

of ore bodies, such as their depth and shape, and the geotechnical parameters, vary in different areas so

different design approaches have been developed and proven with use over time in different countries.

Bringing these approaches together in this standard will facilitate improved safety and operational

reliability.

The majority of the material in this standard deal with the loads to be applied in the design of structures

used in underground mines. Many of the loads and design considerations for underground structures

are identical to the loads and design considerations for similar structures on surface. However, the

underground context introduces some specific differences and challenges that must be addressed in

order to achieve safe and cost-effective structures. This standard deals with those issues and concepts

that are specific to structures used in underground mines.

Some principles for structural design are given, but for the most part it is assumed that local standards

will be used for the structural design.
vi © ISO 2021 – All rights reserved
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DRAFT INTERNATIONAL STANDARD ISO/DIS 23872:2021(E)
Mining structures — Underground structures
1 Scope

This document specifies the design loads and the design procedures for the design of structures used in

underground mines. This standard covers all steel and concrete structures used in underground mines,

irrespective of the depth of the mine or the product being mined.
This document adopts a limit states design philosophy.

There are many reasons, based on mining processes, mining equipment, technical, timing, and cost

factors why certain structures can be constructed underground for a particular application rather than

on surface, and these are carefully assessed at feasibility stage of any mining project. This standard does

not set out to provide comments or recommendations regarding the advantages and disadvantages of

using any type of structure underground, but it covers specific design aspects considered when using

structures in underground mines. This standard is thus primarily intended to provide the technical

information necessary to ensure good engineering of structures where their construction and use

underground is the chosen solution.

Typical underground structures covered by this standard include, but are not limited to:

• Box front structures at the bottom of rock passes
• Conveyor gantry and transfer structures
• Chairlift support structures
• Crusher support structures
• Fan support structures
• Fixed or retractable arresting structures for ramps (see ISO 19426-5)
• Foundations for pumps, fans, winches and underground winders
• High pressure bulkheads
• Monorails

• Overhead crane gantries for workshops, pump stations and sub shaft winder chambers

• Settler structures
• Silo bulkhead structures
• Silo structures
• Structures supporting loose rock
• Tip structures, including dump structures
• Ventilation control doors and other ventilation structures
• Walls and floors for safety bays, refuge stations and sub-stations
• Water control doors
• Water retaining structures
© ISO 2021 – All rights reserved 1
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ISO/DIS 23872:2021(E)
• Underground head frames

This document does not cover matters of operational safety or layout of the underground structures.

2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements of this document. For dated references, only the edition cited applies. For

undated references, the latest edition of the referenced document (including any amendments) applies.

EN 1997-1, Eurocode 7: Geotechnical design – Part 1: General rules
ISO 2394, General principles on reliability for structures
ISO 3010, Bases for design of structures — Seismic actions on structures
ISO 4354, Wind actions on structures
ISO 10721-1, Steel structures — Part 1: Materials and design
ISO 12122, Timber structures — Determination of characteristic values

ISO 19338, Performance and assessment requirements for design standards on structural concrete

ISO 19426-1, Structures for mine shafts — Part 1: Vocabulary
ISO 19426-2, Structures for mine shafts — Part 2: Headframe structures
ISO 19426-5, Structures for mine shafts — Part 5: Shaft system structures
ISO 22111, Bases for design of structures — General requirements
ISO 31010, Risk management – Risk assessment techniques

ISO 22477-5, Geotechnical investigation and testing — Testing of geotechnical structures — Part 5: Testing

of grouted anchors
3 Terms and definitions

For the purposes of this document, the terms and definitions of ISO 19426-1 and the following terms

and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org
3.1
arresting structure

structure installed in a ramp or inclined roadway to arrest the motion of a runaway vehicle, or installed

in a roadway approaching a vertical or decline shaft to prevent vehicles inadvertently entering the shaft

(see emergency arresting dropset in ISO 19426-1).
3.2
bagcrete

The required dry ingredients to be used to prepare a specified strength of concrete put into a bag with

the cement in a smaller waterproof bag inside the larger bag and sealed.
2 © ISO 2021 – All rights reserved
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ISO/DIS 23872:2021(E)
3.3 bulkhead
3.3.1
high pressure bulkhead

a liquid retaining structure that is constructed in underground excavations, primarily designed to

prevent water or other liquid from entering a working area of a mine or to prevent compressed air from

escaping, and where the pressure exceeds 70 m head of water.
3.3.2
silo bulkhead

a structure at the bottom of an underground silo that contains the weight of material in the silo.

3.4
development

a tunnel excavated through ground to gain access and provide a ventilation airway to the orebody and

infrastructure required to mine the orebody.
3.5
dump structure

a structure, installed at the top of a rock pass to receive rock into the rock pass.

Note 1 to entry: A dump structure is often constructed of concrete lined with steel plates, and can be equipped

with a rock sizing mechanism.
3.6
floor
the ground across the bottom of an underground excavation.
3.7
ground
(surrounding rock)

any natural material (hard or soft) surrounding an excavation or underground workings in a mine.

3.8
initial relaxation

the strain in the ground that occurs when an underground excavation is made due to reduction, or

redistribution of the ground stress at the excavation from some higher value to zero.

3.9
injection

process of introducing injection grout (3.9.1) at pressure into the ground-mortar contact area or into

fractured or fissured ground.
3.9.1
injection grout

a mixture of cement and water, which can include chemicals, that is injected into the ground-bulkhead

contact area and the surrounding ground under pressure to meet the designed hydraulic gradient

requirements around the bulkhead.

Note 1 to entry: In the context of this standard, this refers to bulkhead construction.

3.10
intrusion

process of introducing intrusion mortar (3.9.1) into previously placed aggregate such that the pressure

at the mortar outlet pipe is no more than is just required to introduce the mortar over the full area of

placed aggregate.
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ISO/DIS 23872:2021(E)
3.10.1
intrusion mortar

a mix of fine aggregate, cement and water, which can include chemicals, that is intruded into the entire

volume of the high pressure bulkhead once placement of the plums and coarse aggregate has been

completed.

Note 1 to entry: In the context of this standard, this refers to bulkhead construction.

3.10.2
intrusion piping

small bore piping in the high pressure bulkhead structure, placed to facilitate an even placement of

intrusion mortar within previously placed aggregate and plums.
3.11
plum
(cobble)

piece of rock larger than standard aggregate, that can be added to concrete in specified circumstances.

3.12
return airway

tunnel, or development, used to exhaust the air from the working areas of the mine.

3.13
roof
(hanging wall, back)
the ground across the top of an underground excavation.
3.14
shedder plates
(deflector plates)

plates placed over equipment and inclined in such manner as to deflect any spillage away from the

equipment.
3.15
side wall
the ground at the side of an underground excavation.
3.16
slick lines

pipes installed in a shaft or a borehole (normally during sinking) to convey wet concrete from the batch

plant to the point of use.
3.17
slinging

the operation of suspending equipment or materials below a conveyance for transport in the mine shaft.

3.18
tightening

high pressure injection of grout around the perimeter of the mortar intrusion high pressure bulkhead in

order to seal the interface between the bulkhead and the surrounding ground and render the bulkhead

watertight.
3.18.1
tightening pipes

pipes of a suitable diameter in the high-pressure bulkhead structure to allow re-drilling in the bulkhead

structure to enable the sealing (tightening) of the mortar-ground interface and surrounding ground

fractures.
4 © ISO 2021 – All rights reserved
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ISO/DIS 23872:2021(E)
4 Symbols
For the purposes of this document, the following symbols apply.
a seismic acceleration (m/s )

A area of bearing between the high pressure bulkhead and the surrounding ground (m )

A surface area of the high pressure bulkhead (m )
b bearing strength of the surrounding ground (N/m )

B bearing resistance of the interface between the high pressure bulkhead and the surrounding

ground (N)
d deformation of the relevant structural component, expressed in metres (m)
F design load, or load effect (N, Nm)
F additional permanent load due to water head (N)
F factored parallel sided high pressure bulkhead design strength (N)
F ultimate parallel sided high pressure bulkhead design load (N)
g acceleration due to gravity (m/s )
G permanent load or effect (N, Nm)
h design height of the rock pass, expressed in metres (m)

h height through which the rock falls; to be taken as the depth of the rock pass, expressed in metres (m)

H maximum height of liquid above the centre of the high pressure bulkhead (m)
i hydraulic gradient
L length of the high pressure bulkhead (m)
m mass of the largest rock, expressed in kilograms (kg)
p reference pressure (Pa)
q water pressure (Pa)
q additional hydraulic pressure due to seismic action (Pa)
RD relative density of the liquid
R single rock impact load on the box front, expressed in newtons (N)
v shear strength of the surrounding ground (N/m )

V shear resistance of the interface between the high pressure bulkhead and the surrounding ground (N)

Z impact energy of the falling rock, expressed in joules (J)

αi proportion of potential energy transferred into impact energy on the box front

γ unit weight of water (N/m )
ρ density of the liquid (kg/m )
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ISO/DIS 23872:2021(E)

ρ density of the rock pass contents, expressed in kilograms per cubic metre (kg/m )

φ load factor for the additional permanent water head load

ϕ resistance factor for the shear resistance between the high pressure bulkhead and the sur-

rounding ground
5 Materials
5.1 Underground storage
The owner of the mine sh
...

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