ISO 23872:2021

FINAL
INTERNATIONAL ISO/FDIS
DRAFT
STANDARD 23872
ISO/TC 82
Mining structures — Underground
Secretariat: DIN
structures
Voting begins on:
2021­09­08
Voting terminates on:
2021­11­03
RECIPIENTS OF THIS DRAFT ARE INVITED TO
SUBMIT, WITH THEIR COMMENTS, NOTIFICATION
OF ANY RELEVANT PATENT RIGHTS OF WHICH
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ISO/FDIS 23872:2021(E)
LOGICAL, COMMERCIAL AND USER PURPOSES,
DRAFT INTERNATIONAL STANDARDS MAY ON
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©
NATIONAL REGULATIONS. ISO 2021

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ISO/FDIS 23872:2021(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2021
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
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ISO/FDIS 23872:2021(E)

Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Symbols . 4
5 Materials . 5
5.1 Underground storage . 5
5.2 Concrete . 6
5.2.1 General. 6
5.2.2 Target strength . 6
5.2.3 Plums . 6
5.2.4 Special recommendations for underground application . 6
5.2.5 Water quality . 6
5.2.6 Durability . 6
5.3 Steel . 6
5.3.1 General. 6
5.3.2 Special requirements for underground application . 7
5.3.3 Durability . 7
5.3.4 Timber . 7
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 . 8
6.1.5 Loads on box fronts . 9
6.1.6 Loads on high­pressure 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 .11
6.2.2 Long­term ground displacement .11
6.2.3 Sudden ground displacement .12
6.3 Seismic loads.12
6.4 Emergency loads .12
6.4.1 General.12
6.4.2 Explosion loads .12
6.4.3 Air blast loads .12
6.4.4 Mud­rush loads .13
6.4.5 Vehicle impact loads .13
6.4.6 Ground or rock impact loads .13
6.4.7 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 high­pressure bulkheads .14
7.5.1 Types of high-pressure bulkheads .14
7.5.2 Strength requirements.15
7.5.3 Watertightness requirements .16
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ISO/FDIS 23872:2021(E)

7.6 Design of underground head frames . .16
8 Construction requirements .16
8.1 Transport and storage .16
8.2 Anchoring into ground .16
8.2.1 Chemical grouted anchors .16
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 .17
8.3 Bearing against ground.17
8.3.1 Intact ground .17
8.3.2 Fractured ground . .17
8.4 Excavation tolerances .18
8.5 Construction of high­pressure bulkheads .18
Annex A (informative) Transportation, handling and storage .19
Annex B (informative) Use of concrete underground .20
Annex C (informative) Design and construction of parallel sided high-pressure bulkheads
by mortar intrusion .28
Bibliography .43
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ISO/FDIS 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 non­governmental, 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 of 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 www .iso .org/
iso/ foreword .html.
This document was prepared by Technical Committee ISO/TC 82, Mining.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
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ISO/FDIS 23872:2021(E)

Introduction
Many mining companies, and many of the engineering companies that provide designs for mines,
operate globally, therefore this document 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 document will facilitate improved safety and operational
reliability.
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. While
this document is not meant to provide comments or recommendations regarding the advantages and
disadvantages of using any type of structure underground, it covers specific design aspects that need
be considered when using structures in underground mines. It 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.
The majority of the material in this document deals 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 cost­effective structures. This document 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.
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FINAL DRAFT INTERNATIONAL STANDARD ISO/FDIS 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. It 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.
Typical underground structures covered by this document 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;
— underground head frames;
— ventilation control doors and other ventilation structures;
— walls and floors for safety bays, refuge stations and sub-stations;
— water control doors;
— water retaining structures.
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.
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ISO/FDIS 23872:2021(E)

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 10721­1, 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 19426­1, Structures for mine shafts — Part 1: Vocabulary
ISO 19426­2, Structures for mine shafts — Part 2: Headframe structures
ISO 19426­5, Structures for mine shafts — Part 5: Shaft system structures
ISO 22111, Bases for design of structures — General requirements
EN 1997­1, Eurocode 7: Geotechnical design – Part 1: General rules
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO 19426-1 and the following
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 https:// 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
Note 1 to entry: See emergency arresting dropset in ISO 19426-1.
3.2
bagcrete
required dry ingredients 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
3.3 Bulkheads
3.3.1
high-pressure bulkhead
liquid-retaining structure 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
structure at the bottom of an underground silo that contains the weight of material in the silo
3.4
development
tunnel excavated through ground (3.7) to gain access and provide a ventilation airway to the orebody
and infrastructure required to mine the orebody
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ISO/FDIS 23872:2021(E)

3.5
dump structure
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
ground (3.7) across the bottom of an underground excavation
3.7
ground
surrounding rock
natural material (hard or soft) surrounding an excavation or underground workings in a mine
3.8
initial relaxation
strain in the ground (3.7) 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 ground­mortar contact area or into
fractured or fissured ground (3.7)
3.9.1
injection grout
mixture of cement and water, that can include chemicals, injected into the ground-bulkhead contact
area and the surrounding ground (3.7) under pressure to meet the designed hydraulic gradient
requirements around the bulkhead
Note 1 to entry: In the context of this document, this refers to bulkhead constructions.
3.10
intrusion
process of introducing intrusion mortar (3.10.1) 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
the placed aggregate
3.10.1
intrusion mortar
mix of fine aggregate, cement and water, that can include chemicals, intruded into the entire volume
of the high-pressure bulkhead (3.3.1) once placement of the plums (3.11) and coarse aggregate has been
completed
Note 1 to entry: In the context of this document, this refers to bulkhead constructions.
3.10.2
intrusion pipes
small bore pipes in the high-pressure bulkhead (3.3.1) structure, placed to facilitate an even placement
of intrusion mortar (3.10.1) within previously placed aggregate and plums (3.11)
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 (3.4), used to exhaust the air from the working areas of the mine
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ISO/FDIS 23872:2021(E)

3.13
roof
hanging wall
back
ground (3.7) across the top of an underground excavation
3.14
deflector plate
shedder plate
plate placed over equipment and inclined in such manner as to deflect any spillage away from the
equipment
3.15
side wall
ground (3.7) at the side of an underground excavation
3.16
slick line
pipe 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
operation of suspending equipment or materials below a conveyance for transport in the mine shaft
3.18
tightening
high­pressure injection (3.9) of grout around the perimeter of the mortar intrusion (3.10) high-pressure
bulkhead (3.3.1) in order to seal the interface between the bulkhead and the surrounding ground (3.7)
and render the bulkhead watertight
3.18.1
tightening pipe
pipe of a suitable diameter in the high-pressure bulkhead (3.3.1) structure to allow re­drilling in the
bulkhead structure to enable the sealing [tightening (3.18)] of the mortar­ground interface and
surrounding ground (3.7) fractures
4 Symbols
2
a seismic acceleration (m/s )
n
2
A area of bearing between the high­pressure bulkhead and the surrounding ground (m )
B
2
A surface area of the high­pressure bulkhead (m )
H
2
b bearing strength of the surrounding ground (N/m )
l
B bearing resistance of the interface between the high­pressure bulkhead and the surrounding
l
2
ground (N/m )
d deformation of the relevant structural component (m)
i
F design load, or load effect (N, Nm)
F additional permanent load due to water head (N)
H
F factored parallel sided high­pressure bulkhead design strength (N)
R
F ultimate parallel sided high­pressure bulkhead design load (N)
U
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ISO/FDIS 23872:2021(E)

2
g acceleration due to gravity (m/s )
G permanent load or effect (N, Nm)
h design height of the rock pass (m)
b
h height through which the rock falls; to be taken as the depth of the rock pass (m)
d
H maximum height of liquid above the centre of the high-pressure bulkhead (m)
i hydraulic gradient
L length of the high­pressure bulkhead (m)
m mass of the largest rock (kg)
r
p reference pressure (Pa)
h
q water pressure (Pa)
q additional hydraulic pressure due to seismic action (Pa)
n
R relative density of the liquid
D
R single rock impact load on the box front (N)
i
2
v shear strength of the surrounding ground (N/m )
I
V shear resistance of the interface between the high­pressure bulkhead and the surrounding ground
I
(N)
Z impact energy of the falling rock (J)
i
α proportion of potential energy transferred into impact energy on the box front
i
3
γ unit weight of water (N/m )
3
ρ density of the liquid (kg/m )
L
3
ρ density of the rock pass contents (kg/m )
φ load factor for the additional permanent water head load
H
ϕ resistance factor for the shear resistance between the high­pressure bulkhead and the surround­
H
ing ground
5 Materials
5.1 Underground storage
The owner of the mine shall specify the storage location and conditions for underground storage of
construction materials, bearing in mind the adverse environment, the length of time for storage and
possible rough handling.
Specific requirements for storage are made in 5.2 and 5.3, and further recommendations for
underground storage are made in Annexes A, B and C.
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ISO/FDIS 23872:2021(E)

5.2 Concrete
5.2.1 Gener
...