EN 12889:2022

SLOVENSKI STANDARD
01-januar-2023
Nadomešča:
SIST EN 12889:2000
Izvedba in preskušanje kanalov in drenaž brez izkopa
Trenchless construction and testing of drains and sewers
Grabenlose Verlegung und Prüfung von Abwasserleitungen und -kanälen
Mise en oeuvre sans tranchée et essais des branchements et collecteurs
d'assainissement
Ta slovenski standard je istoveten z: EN 12889:2022
ICS:
91.140.80 Drenažni sistemi Drainage systems
93.030 Zunanji sistemi za odpadno External sewage systems
vodo
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN 12889
EUROPEAN STANDARD
NORME EUROPÉENNE
October 2022
EUROPÄISCHE NORM
ICS 93.030; 23.040.05 Supersedes EN 12889:2000
English Version
Trenchless construction and testing of drains and sewers
Mise en oeuvre sans tranchée et essais des Grabenlose Verlegung und Prüfung von
branchements et collecteurs d'assainissement Abwasserleitungen und -kanälen
This European Standard was approved by CEN on 5 September 2022.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2022 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 12889:2022 E
worldwide for CEN national Members.

Contents Page
European foreword . 4
1 Scope . 5
2 Normative references . 5
3 Terms and definitions . 5
4 General . 7
4.1 Technical principles . 7
4.2 Safeguarding design decisions . 7
5 Construction components and materials . 8
5.1 General . 8
5.2 Pipes and joints . 8
5.3 Manholes and inspection chambers . 8
5.4 Delivery, handling and transportation on site . 8
5.5 Storage . 8
5.6 Other materials . 9
6 Techniques . 9
6.1 Classification . 9
6.2 Unmanned techniques . 11
6.2.1 General . 11
6.2.2 Non-steerable techniques . 11
6.2.3 Steerable techniques. 18
6.3 Manned techniques . 23
6.3.1 General . 23
6.3.2 Non-steerable techniques . 24
6.3.3 Steerable techniques. 24
6.3.4 Other manned techniques . 28
7 Requirements of planning and construction . 29
7.1 General . 29
7.2 Basic evaluation, design and construction planning . 29
7.2.1 General . 29
7.2.2 Survey of existing structures and systems . 30
7.2.3 Ground and groundwater . 31
7.2.4 Minimum clear dimensions . 33
7.2.5 Subsidence, heaves, cover . 33
7.2.6 Layout of the line . 33
7.2.7 Tolerances . 33
7.2.8 Starting, intermediate and target pits . 33
7.2.9 Working face support . 34
7.2.10 Additional measures in water bearing ground . 34
7.2.11 Obstacles . 34
7.2.12 Soil conditioning . 34
7.2.13 Structural calculation . 35
7.2.14 Construction site arrangement . 35
7.3 Work preparation and construction . 35
7.3.1 General . 35
7.3.2 Starting, intermediate and target pits . 36
7.3.3 Exit and entry processes . 36
7.3.4 Static calculation of launch and reception shafts . 36
7.3.5 Overcut . 36
7.3.6 Recording and logging of jacking parameters . 36
7.3.7 Support of the working face . 37
7.3.8 Lubricant and supporting medium . 37
7.4 Avoidance of damage . 37
8 Inspection and testing of pipelines after installation . 38
8.1 General . 38
8.2 Visual inspection . 38
8.3 Leaktightness . 38
9 Qualifications . 38
Annex A (informative) Additional information about the different systems. 39
Annex B (informative) Guide to typical ranges of application regarding diameters and
lengths in suitable soil . 49
Annex C (informative) Guide to typical ranges of application for selected trenchless
techniques regarding diameters and lengths in suitable soils . 51
Annex D (informative) Trenchless insertion using a pipe plough system . 52
Bibliography . 53

European foreword
This document (EN 12889:2022) has been prepared by Technical Committee CEN/TC 165 “Waste water
engineering”, the secretariat of which is held by DIN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by April 2023, and conflicting national standards shall be
withdrawn at the latest by April 2023.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN shall not be held responsible for identifying any or all such patent rights.
This document supersedes EN 12889:2000.
In comparison with the previous edition, the following changes have been made:
a) editorial and technical revision of the complete document;
b) modification of terms and definitions;
c) adaptation of the description of all methods of trenchless techniques and installation of pipelines;
d) Clause 7 “Requirements of planning and construction” was added.
Any feedback and questions on this document should be directed to the users’ national standards body.
A complete listing of these bodies can be found on the CEN website.
According to the CEN-CENELEC Internal Regulations, the national standards organisations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia,
Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland,
Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Republic of North
Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and the United
Kingdom.
1 Scope
This document is applicable to the trenchless construction, trenchless replacement techniques and
testing of new drains and new sewers in the ground and usually operating as gravity or pressure
pipelines, formed using prefabricated pipes and their joints.
Renovation techniques for existing pressure and non-pressure systems are not covered by this document.
Methods of trenchless construction include:
— manned and unmanned techniques;
— steerable and non-steerable techniques.
NOTE 1 Mining or tunnelling techniques for permanent structures (e.g. in situ construction or the use of
prefabricated segments) are not covered by this document although some parts can apply to these methods.
NOTE 2 Trenchless insertion using a pipe plough system is a common method for installing small pipes and
cables. The method does not exactly cope with the scope of this document. Therefore, it is described in the
informative Annex D.
Requirements for associated pipeline installation work other than trenchless construction, e.g. for
manholes and inspection chambers, are not covered by this document and are specified in EN 1610. This
also applies to pipes that are subsequently installed within entry and exit shafts/pits.
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 476, General requirements for components used in drains and sewers
EN 752, Drain and sewer systems outside buildings - Sewer system management
EN 805, Water supply - Requirements for systems and components outside buildings
EN 1295-1, Structural design of buried pipelines under various conditions of loading - Part 1: General
requirements
EN 1610, Construction and testing of drains and sewers
EN 1997-2, Eurocode 7: Geotechnical design - Part 2: Ground investigation and testing
3 Terms and definitions
For the purposes of this document, 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 https://www.electropedia.org/
3.1
cutting head
tool or system of tools on a common support, which excavates at the face of a bore
Note 1 to entry: The term usually applies to mechanical methods of excavation.
3.2
expander
tool which enlarges a bore by displacement of the surrounding ground rather than by excavation
3.3
gravity pipeline
pipeline where flow is caused by the force of gravity and where the pipeline is designed usually to operate
partially full
3.4
overbreak
extent by which the excavated void including accidental ground losses initially exceeds the outside
dimension of the pipe
3.5
overcut
half of the difference of borehole diameter and external pipe diameter (ideally, an even annular space
around the pipeline)
3.6
pipe jacking
system of directly installing pipes behind a cutting head and/or shield, by hydraulic jacking from a drive
shaft, such that the pipes form a string in the ground
3.7
reamer
cutting head attached to the end of a drill string or pilot rod to enlarge the pilot diameter during a pull-
back or pushing operation, to enable a pipe or pipes to be installed
3.8
renovation
work incorporating all or part of the original fabric of the pipeline by means of which its current
performance is improved
[SOURCE: EN 15885:2018, 3.2]
3.9
replacement
construction of a new pipeline, on or off the line of an existing pipeline, where the function of the new
pipeline system incorporates that of the old
[SOURCE: EN 15885:2018, 3.4]
3.10
spoil
material excavated and removed in the course of installation
3.11
trenchless construction technique
technique for constructing pipelines in the ground without opening trenches
3.12
manned technique
technique involving the use of personnel working in the excavated bore during installation
3.13
unmanned technique
technique avoiding the use of personnel working in the excavated bore during installation
4 General
4.1 Technical principles
Pipelines, manholes and inspection chambers are engineering structures in which the combined
performance of construction components, bedding and fill or the surrounding ground constitutes the
basis for stability and safety in operation. The pipes, fittings and components for jointing supplied,
together with the work carried out at site, are all important factors in achieving a structure with adequate
performance over the intended service life.
The network owner and the planner shall coordinate the extent and the requirements of the engineering
services to be rendered each individual case.
The pipeline and any associated structures shall be designed during planning in accordance with
EN 1295-1 and EN 752 as applicable to ensure that they are capable of carrying all foreseeable imposed
and operational loads with a sufficient level of safety.
A procedure shall be established for the resolution of technical questions, agreement and recording of
changes to design decisions made during construction.
Additionally, other local or national regulations can apply, e.g. concerning health and safety, pavement
installation, tolerances for deviation in line and level and requirements for leaktightness testing.
4.2 Safeguarding design decisions
In the execution of the work it shall be ensured that the decisions made in the design are complied with
or adapted to changed conditions.
The design decisions can be affected by a variation of any of the following which should be checked during
installation:
— pipe support;
— ground conditions and soil types;
— construction traffic and assumptions concerning temporary loads;
— ground water level;
— existing infrastructure in the same proximity (e.g. pipelines, cables, structures);
— settlement and heave;
— deflection;
— deviation from line;
— pipe type, strength or class.
NOTE The above list is not exhaustive.
5 Construction components and materials
5.1 General
Construction components and materials shall conform to European Standards. In the absence of these,
the components and materials shall comply with design requirements and EN 476.
All written instructions of the manufacturer shall be complied with.
5.2 Pipes and joints
Installation shall not commence before the following criteria have been agreed between the designer and
installer. These shall be obtained from appropriate product standards or from the pipe manufacturer:
— internal pipe diameter;
— external pipe diameter;
— pipe length;
— tolerances on dimensions;
— permissible jacking load or pulling force;
— type and performance of joints;
— longitudinal flexibility (acceptable bending radius or angular deflection).
5.3 Manholes and inspection chambers
Manholes and inspection chambers shall comply with the design. Prefabricated components shall be
assembled and installed according to the instructions of the manufacturer and the designer.
5.4 Delivery, handling and transportation on site
Construction components and materials shall be inspected on delivery to ensure that they are
appropriately marked and comply with the design requirements.
Any handling or transportation instructions from the manufacturer shall be complied with.
Products shall be examined both on delivery and immediately prior to installation to ensure that they are
free from damage and in accordance with the relevant product standard.
5.5 Storage
Any instructions from the manufacturer and the requirements of the appropriate product standards shall
be complied with.
Construction components and materials shall be stored in such a manner to keep them clean and avoid
contamination or degradation, for example elastomeric jointing components shall be kept clean and be
protected from sources of ozone (e.g. electrical equipment), sunlight and oil, where necessary.
Pipes shall be secured to prevent rolling. Excessive stacking heights shall be avoided so that pipes in the
lower part of the stacks are not overloaded. Stacks of pipes shall not be placed close to open trenches.
Pipes with protective coatings shall be stored where necessary, on supports which keep them clear of the
ground to avoid damage to coatings and joints. All pipes should be stored on supports in very cold
weather to avoid freezing to the ground.
5.6 Other materials
The mechanical and environmental impact of other materials used during the construction process on:
— pipeline;
— surrounding soil;
— surface water and groundwater
shall be considered by the designer.
Consideration shall also be given to the following:
— production/origin;
— treatment and storage;
— leaching;
— cleanliness.
6 Techniques
6.1 Classification
Pre-fabricated pipes are jacked or pulled into the ground between the starting pit and the target pit. The
soil is either displaced and/or excavated at the working face and is mechanically, hydraulically or
pneumatically transported to the starting or target pit or in some techniques can be removed from the
pipe as an earth core after completion. There is a distinction between manned and unmanned processes.
Non-steerable or steerable jacking processes are selected depending on the required accuracy of
installation.
The selection of the process depends on:
— the planned/given jacking pipe;
— the required positional precision; this shall be defined by the client/ planner;
— the proximity to neighbouring utility services and sewers and other structures and systems;
— the external diameter;
— the jacking distance;
— the ground conditions;
— the groundwater conditions;
— the minimum depth of cover and
— the clear dimensions necessary for employing personnel inside the pipe string.
NOTE 1 The above list is not exhaustive.
A schematic classification of trenchless techniques is given in Figure 1, representing techniques available
at the time of publication of this document.
The techniques are described and illustrated in 6.2 and 6.3.
Planning information for the application of different systems are given in Annex A, Table A.1.
NOTE 2 The list presented in Figure 1 is not exhaustive. Other techniques and combinations exist and can be
used.
Figure 1 — Classification of trenchless techniques
6.2 Unmanned techniques
6.2.1 General
Unmanned techniques do not require employment of personnel inside the pipe. Steerable Horizontal
Directional Drilling methods (HDD) as well as methods for trenchless replacement of pipelines on the
same line represent unmanned techniques that are related to pipe jacking. The prerequisite for
temporary employment of personnel inside the pipe string are described in 7.2.4.
6.2.2 Non-steerable techniques
6.2.2.1 General
The accuracy of non-steerable techniques in new construction is influenced by the ground (e.g. soil type),
intrusions and stratifications, the type of pipe joint, the external pipe diameter and the pipe wall thickness
and other things, and decreases overproportionally to the jacking distance. Therefore, the use of these
methods for pipelines that require an exact position is restricted for operational reasons. Damage to
adjacent systems has to be excluded by ensuring sufficient clearance. During new construction suitable
methods should be used to determine the position during jacking.
For use in water-bearing strata, additional measures such as groundwater retention can become
necessary.
Table B.1 contains empirical values for the area of application of the listed unmanned, non-steerable
techniques. The in situ ground conditions and project-specific boundary conditions shall always be taken
into consideration.
6.2.2.2 Soil displacement techniques
6.2.2.2.1 General
All listed techniques require soil that is displaceable.
6.2.2.2.2 Impact moling
Impact moling is a technique, generally considered to be non-steerable, using a pneumatic powered
torpedo shaped device, known as a mole (see Figure 2). This incorporates a reciprocating internal
hammer impacting on the back of a nose cone which in some cases can move independently of the main
body. The friction between the main body and the ground enables the nose cone to move forward at each
hammer blow, whilst the length of the main body keeps the mole on line. There are several designs of
nose cone, which claim to give better penetration, or to be less susceptible to being pushed off line by
lumps of stone.
Because the soil material has to be forced out into the surrounding ground, this technique is confined to
small pipe diameters. The pipe is generally pulled in behind the mole, or can be pulled back as the mole
is reversed out. The pipe installation is either done simultaneously or, in a sufficiently stable soil, by
subsequent pulling or pushing in. A shrinking of the bore diameter of the cavity by 5 % to 15 % has to be
taken into account.
Key
1 air compressor
2 starting pit
3 new (discrete) pipe
4 impact mole
5 planned route
6 target pit
7 typical nose cone
Figure 2 — Example of impact moling
6.2.2.2.3 Pipe ramming with a pipe closed at its leading end
Pipe ramming with a pipe closed at its leading end is a technique of forming a bore by driving a steel
casing with a closed end using a percussive hammer (see Figure 3). The soil is displaced by the leading
closed pipe end.
When dimensioning the pipes for trenchless installation with pipe ramming, additional dynamic loads
have to be taken into account. Product pipes with cement mortar lining and/or cement mortar coating
shall not be directly installed by pipe ramming.

Key
1 starting pit
2 ramming hammer
3 pipe
4 air compressor
5 end cone
6 planned route
7 target pit
Figure 3 — Example of pipe ramming with a pipe closed at its leading end
6.2.2.2.4 Rod pushing with an expander
Pushing a pilot rod displaces the soil. After having arrived in the target pit, the rod is connected to a
conical pushing head or a soil displacement hammer, which is also connected to the host or product pipes.
Afterwards, the entire string is pulled back (see Figure 4).
The upper part of Figure 4 shows the installation of pilot rod and initial displacement of soil. The lower
part shows the installation of the pipe and further displacement of soil.
The expander can be in the form of a displacement cone or a reamer.

Key
1 starting pit 5 target pit
2 ram system 6 rod
3 hydraulic unit 7 expander
4 pilot rod 8 pipe
Figure 4 — Example of the process of rod pushing with an expander
6.2.2.2.5 Pipe bursting
Replacement is done by bursting or splitting the existing pipe, and displacing it into the surrounding
ground, while simultaneously pulling in a new continuous or discrete pipe, of the same or larger diameter.
A bursting head with a cone with or without fixed blades is generally used for brittle pipe materials such
as clay, grey cast iron or fibre cement, whereas a splitting head with cutting blades or discs is generally
used for non-brittle pipe materials such as ductile iron, steel or plastics. Both types of head embody an
expansion cone to displace the existing burst or split pipe into the surrounding ground and form a bore
for the new pipe.
Additional measures can become necessary in water-bearing soils. The new pipe shall be dimensioned in
accordance with the structural calculation.
Methods used are static pipe bursting (see Figure 5) or dynamic pipe bursting (see Figure 6).
NOTE There are other systems known where the expander cone is hydraulically expandable.
Key
1 bursting head
2 expander cone
3 new pipe
4 pulling device
5 hydraulic unit
6 pipe fragments from the original pipe
7 pulling rod
Figure 5 — Example of replacement by static pipe bursting (here installing discrete pipes)

Key
1 bursting head/expander and hammer
2 new pipe
3 cable winch
4 air compressor
5 pipe fragments from the original pipe
6 starting pit
7 target pit
Figure 6 — Example of installation by dynamic pipe bursting (here installing continuous pipes)
6.2.2.2.6 Pipe extraction
Pipe extraction uses a rod puller to pull the old pipe through the ground, removing old pipe sections as
they arrive at the rod puller, while simultaneously pulling in new pipe (see Figure 7). This would typically
be used for pressure pipes, as it allows installation of continuous pipe, and leaves behind no shards of old
pipe.
When the diameter of the new pipe is larger than the old, an expander is used.
Additional measures can become necessary in water-bearing soils.
Due to the high friction forces, only a short length of pipe can be extracted between pits.
Key
1 new pipe
2 starting pit
3 pulling adapter for the new pipe
4 extraction adapter of the original pipe
5 existing pipe; pulling rod inserted
6 target pit
7 pipe splitting/cracking cone
8 hydraulic rod pulling device
9 hydraulic unit
Figure 7 — Example of replacement by pipe extraction
6.2.2.3 Soil removal techniques
6.2.2.3.1 Pipe ramming with an open ended pipe
A steel pipe string that is open at its leading end (sleeve or product pipe) is jacked by means of ramming
energy (see Figure 8). The earth core entering the pipe is usually pushed out, flushed out hydraulically,
or drilled out mechanically after having completed the jacking. Pushing-out by means of compressed air
is only permitted up to an internal pipe diameter of 500 mm subject to taking the necessary safety
measures.
Product pipes with cement mortar lining shall not be installed by pipe ramming.
In strongly swelling, plastic soils the application might not be possible, in rock it is impossible.
In water-bearing soils, additional measure such as lowering of groundwater can become necessary
depending on the groundwater level and soil type.
Key
1 starting pit 6 guide track
2 horizontal ram 7 steel pipe
3 jacking pipe, open 8 cutting ring
4 air compressor 9 planned route
5 target pit
Figure 8 — Example of pipe ramming with an open ended pipe
6.2.2.3.2 Auger boring
A steel pipe string (sleeve or product pipe) is pushed by means of a jacking station. The soil is
simultaneously mechanically excavated at the working face by using a cutting head and mechanically
conveying the spoil by means of augers (see Figure 9). The drive of the cutting head with augers is usually
located in the starting pit.
The selection of the cutting head depends on the ground conditions. A down-the-hole hammer can also
be used as a cut-ting head. In water-bearing soils, additional measures like groundwater lowering can be
necessary.
Key
1 starting pit 5 target pit
2 cutting head with auger 6 casing and auger
3 auger boring machine 7 planned route
4 hydraulic unit 8 cutting head
Figure 9 — Example of (non-steerable) auger boring
6.2.2.3.3 Hammer drilling
Hammer drilling is also known as down-hole hammer drilling. The method uses a pneumatic, percussive
hammer in front of a jacking pipe mainly in rock but also in loose ground. The rock or soil is fragmented
by repeated direct impacts of the hammer.
As the percussive hammer operates a cutting head in the excavated bore, the spoil is removed
mechanically by auger (see Figure 10), by water or compressed air.
NOTE Systems operating without casing are also known.
Key
1 starting pit 6 target pit
2 jacking device 7 planned route
3 new pipe or casing 8 hydraulic unit
4 rod string 9 air compressor
5 hammer with cutting head 10 auger
Figure 10 — Example of hammer drilling
6.2.2.3.4 Pipe eating
An existing pipeline is excavated possibly together with the surrounding soil, and the cutting head is
connected to the existing pipeline by means of a guiding shoe (see Figure 13).
The excavated material is milled and conveyed pneumatically or hydraulically or by means of augers.
In water bearing soils, additional measures can be necessary.
6.2.3 Steerable techniques
6.2.3.1 Microtunnelling
6.2.3.1.1 General
Microtunnelling is a remotely controlled form of pipe jacking originally designed for non-man-entry size
pipes. Technical developments allow using this technique for larger cross-sections (see Figure C.1).
Microtunnelling is a remote, one-stage technique for jacking product or sleeve pipes by using a jacking
machine and simultaneous continuous full-face soil excavation at the working face that is mechanically
supported and/or supported by fluid or earth pressure.
The microtunnelling process is cyclical. After one pipe has been jacked into the bore, the jacks are
retracted and another pipe is lowered into position in the starting pit and the process repeated.
The cutting head shall be adapted to the ground and groundwater conditions as well as the respective
technology. With larger excavation cross-sections, the requirements of supporting the working face and
the annular space is increased.
Excavated material is transported from the cutting head to the starting pit by either an auger or a slurry
system. Where a slurry system is used, separation plants are usually provided on the surface to remove
the spoil from the slurry water which is then recycled.
The alignment control is usually done by means of laser technology or by means of gyroscope and water
level. A hydraulically swivelling steering head changes the direction.
Starting and target shall be excavated and a thrust wall shall be constructed in the starting pit to provide
support for the jacking device and to safely transfer the jacking loads in the ground.
6.2.3.1.2 Microtunnelling with auger spoil removal
Spoil is removed by means of an auger located in a separate auxiliary pipe. The cutting head and the auger
are usually driven from the starting pit (see Figure 11).
It is also possible to drive the cutting head separately. For cohesive soils of firm consistency, the
excavation and removal of the soil can be simplified by adding water at the working face.
Water-bearing soils can require additional measures.

Key
1 target pit 7 conveying bucked
2 bentonite system 8 auger with auxiliary pipe
3 steering unit 9 jacking pipe
4 starting pit 10 steering head
5 lifting device 11 planned route
6 jacking device
Figure 11 — Example of microtunnelling with auger spoil removal
6.2.3.1.3 Slurry shield microtunnelling
The excavated soil is removed hydraulically and a separation unit (e.g. settling container; if required, with
screens, cyclones or other equipment) separates it from the transport medium (see Figure 12).
The type and quality of the transport medium shall be adapted to the ground and groundwater
conditions.
Key
1 target pit 9 starting pit
2 bentonite system 10 lifting device
3 setting basin 11 jacking device
4 separation unit 12 conveyor pump
5 feed pump 13 jacking pipe
6 operation container 14 steering head
7 conveyer pipe 15 planned route
8 feed pipe
Figure 12 — Example of slurry shield microtunnelling
6.2.3.1.4 Slurry shield microtunnelling with compressed air cushion (mixshield)
Basically, the technique is similar to slurry shield microtunnelling. An additional compressed air cushion
minimizes pressure variations at the working face.
6.2.3.1.5 Microtunnelling with earth pressure balance (EPB shield)
The excavated soil is removed from the excavation chamber by an auger and conveyed usually by means
of a muck pump. The use of conditioners broadens the area of application (see 7.2.12). Very soft soils can
be re-treated by means of hydraulic binding agents in order to minimize the costs of material transport
and disposal.
6.2.3.1.6 Microtunnelling spoil removal by other mechanical means
With these techniques, the excavated soil is conveyed by means of techniques other than those mentioned
previously (e.g. air or other mechanical techniques).
The necessity of additional measures in water-bearing soils depends on the technique used.
6.2.3.1.7 Microtunnelling incorporating pipe eating
Pipe eating uses a microtunnelling machine to crush the existing pipe and an auger or slurry system to
extract the pipe fragments together with the surrounding ground if enlargement is required
(see Figure 13). New discrete pipe sections are pushed in behind. The tunnelling machine can have an
extended guide running within the old pipe to keep the machine centred, and can incorporate a seal to
prevent slurry going forward. The pipes and bedding material have to be suitable for the technique.
Traversing on the same invert is possible.
To enable conveying or to improve steering, the existing pipe can previously be filled with suitable
material.
Additional measures in water-bearing soil depend on the technique employed.

Key
1 target pit 7 jacking device
2 cutting head 8 jacking pipe
3 hydraulic unit 9 auxiliary pipe
4 conveying bucket 10 auger
5 starting pit 11 existing old pipe
6 compressor
Figure 13 — Example of replacement by pipe eating
6.2.3.2 Pilot pipe jacking
Pilot pipe jacking is a multi-phase method displacing or excavating the soil (see Figure 14). In the first
phase a steered rigid pilot pipe is accurately installed. The alignment control is usually done by means of
a theodolite with electric camera or by means of a laser. The direction is changed by means of a steering
face (e.g. pilot point) by utilizing the reaction force of the ground.
Afterwards, sleeve or product pipes of the same or of a greater external diameter are driven
simultaneously pushing or pulling the pilot pipes out. Larger external diameters require extension by soil
displacement or excavation in one or more working steps.
In water-bearing soils, additional measures can be necessary.
a) Insertion of pilot pipe
b) Insertion of sleeve pipe
c) Insertion of product pipe
Key
1 pilot pipe head 6 starting pit
2 pilot pipe 7 jacking device
3 hydraulic unit 8 target pit
4 theodolite 9 extension
5 expander 10 product pipe
Figure 14 — Example of the process of pilot pipe jacking
6.2.3.3 Directional drilling (also called HDD – Horizontal directional drilling)
Directional drilling (see Figure 15) is using a machine in which flexible rods are rotated and pushed,
propelling a cutter which is generally slant headed through the ground. Steering is accomplished by the
reaction of the slant head against the ground when pushed without rotation. Supported by a location
device, this enables a pilot hole to be established to a planned line and grade, after which the hole is
enlarged by pulling back a rotating reamer. Simultaneously or in a separate process the product pipe is
pulled into the bore hole.
There are many different types of cutter to enable steering capability to be maintained in difficult ground
conditions such as rock, where a slant head cutter will not work effectively. No steering is done with
reamers.
When drilling, the soil or rock cuttings shall be removed. As drilling proceeds, this is carried out from the
hole by the drilling fluid that is continually pumped down the drilling rods, serving also to cool the
cutter/reamer, and support the hole to prevent it collapsing.

Key
1 HDD rig 9 back reamer for pipe pulling
2 measuring cable 10 swivel
3 bent sub 11 new pipe
4 non-magnetic drill rod 12 pulling head
5 probe/sonde/beacon 13 location device
6 drill head a) first process step
7 drill rod b) second process step
8 back reamer for bore hole expansion c) third process step
Figure 15 — Example of the process of horizontal directional drilling
6.3 Manned techniques
6.3.1 General
Manned pipe jacking techniques are marked by constant employment of personnel in the pipe string
and/or in the jacking machine during jacking.
6.3.2 Non-steerable techniques
In front of the pipeline, a steel jacket is driven in an unsteered way. Under the protection of this steel
jacket, the soil at the working face is excavated and removed. In water-bearing soils, additional measures
become necessary (groundwater lowering, soil stabilization, compressed air, etc.).
6.3.3 Steerable techniques
6.3.3.1 General
In these one-stage techniques, a pipe stri
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