oSIST prEN 1536:2026

• Abstract:

  1.1 This European Standard establishes general principles for the execution of bored piles (see 3.2). ; NOTE 1 This standard covers piles or barrettes which are formed in the ground by excavation and are structural members used to transfer actions and/or limit deformations. ; NOTE 2 This standard covers piles with circular cross-section (see Figures 1 and A.1a)) and barrettes (see 3.3) with rectangular, T or L or any other similar cross-section (see Figure 2) concreted in a single operation. ; NOTE 3 In the standard the term pile is used for circular cross-section structure and the term barrette for other shapes. Both are bored piles.; 1.2 This European Standard applies to bored piles (see Figure 3) with:; - uniform cross-section (straight shaft);; - telescopically changing shaft dimensions; ; - excavated base enlargements; or; - excavated shaft enlargements.; NOTE The shape of a pile base and of an enlargement depends on the tool used for the excavation.; 1.3 This European Standard applies (see Note) to: ; - bored piles with a depth to width ratio  5;; - piles (see Figures 1 and 3) with a shaft diameter 0,3 m  D  3,0 m;; - barrettes (see Figure 2) with the least dimension Wi  0,4 m, a ratio LBiB / Wi between its largest and its least dimensions  6 and a cross-sectional area A  15 m²;; - piles with circular precast elements used as structural member (see Figure 7) with a least dimension DP  0,3 m;; - barrettes with rectangular precast elements used as structural member with a least dimension WP  0,3 m. ; NOTE The standard covers a large range of diameters. For small diameter bored piles less than 450 mm, the general specification can be adapted to cater for the lack of space (e.g. minimum bars number and spacing).; 1.4 This European Standard applies to piles with the following rake (see Figure 4):; - n  4 (  76°);; - n  3 (  72°) for permanently cased piles. ; (...)

• Status: Not Published
• Public Enquiry End Date: 19-Nov-2026
• ICS: 93.020 - Earthworks. Excavations. Foundation construction. Underground works
• Technical Committee: KON - Structures
• Current Stage: 4020 - Public enquire (PE) (Adopted Project)
• Start Date: 05-Oct-2026
• Due Date: 22-Feb-2027
• Ref Project: prEN 1536 - Execution of special geotechnical work - Bored piles

• Revises: SIST EN 1536:2011+A1:2015 - Execution of special geotechnical work - Bored piles
• Effective Date: 09-Jul-2024

oSIST prEN 1536:2026 is a CEN draft European Standard for the execution of special geotechnical work - bored piles. It sets out general principles for how bored piles are specified, executed, supervised and recorded so they can be used as foundations, retaining walls and related underground works. It is aimed at engineers, specialist contractors, supervisors, quality managers and buyers who need a common basis for planning and controlling piling work.

What does oSIST prEN 1536:2026 specify?

oSIST prEN 1536:2026 specifies the execution of bored piles formed by excavation and filled with self-hardening material. The scope covers straight shafts, telescopic shaft changes, excavated base enlargements, excavated shaft enlargements, single piles, pile groups and pile walls, including raking piles within the stated limits.

The document is organized into clauses 1 to 11 covering scope, normative references, terms, the information needed for the work, geotechnical investigation, materials and products, design considerations, execution, supervision and testing, records, and special requirements. It also includes three informative annexes.

Annex	What it covers
A	Watertightness guidance for embedded retaining walls
B	Example inspection and testing plans for bored piles, CFA piles and shaft/base grouting
C	Degree of obligation of the provisions

What are the key requirements of oSIST prEN 1536:2026?

oSIST prEN 1536:2026 links design, site investigation, materials and execution so the bored pile can be built as intended in the ground. The main practical message is that the method of execution, the ground conditions and the tolerances all have to be considered together before work starts.

Information, investigation and planning

Before work starts, the execution specifications shall include all information needed to carry out the piling works. That includes legal restrictions, site layout, adjacent structures and services, environmental constraints, and a quality management system that covers supervision, inspection, testing, monitoring and maintenance.

The geotechnical investigation has to provide the data needed to choose the work method, equipment and tools. It shall be available in time for planning, checked for sufficiency, and supplemented if it is not enough. In practice, this means the contractor and designer need ground data that is useful for execution, not only for design.

Materials, support fluids and concrete

The document requires constituents to comply with the relevant European Standards, the local provisions and the execution specifications. It also requires source documentation for constituents and notification before changes of source.

Support fluids may be bentonite based, polymer based, or a blend of both. They have to support the borehole during excavation and then be displaced by concrete before concreting. Tables 1 and 2 give the expected properties for bentonite and synthetic polymer support fluids, which matters because the fluid has to keep the hole stable without preventing proper concreting.

Concrete, grout, plastic concrete, self-hardening slurry and reinforcement are all covered. The standard requires on-site concrete sampling and testing to follow the execution specifications and EN 13670 where relevant, with full test records kept. For grout and self-hardening slurry, the composition, method and test approach have to suit the application and the ground.

Design features that depend on how the pile is built

oSIST prEN 1536:2026 states that the design of bored piles has to take the execution method and the construction tolerances into account. It also requires consideration of aggressive ground or groundwater, and any lining or temporary casing that affects skin friction or cage detailing.

For pile walls, the design has to follow the wall-related considerations from EN 1538. Secant pile walls are not expected to be watertight in an absolute sense, so the degree of watertightness has to be specified for the structure and the site conditions. Table 3 classifies watertightness for secant pile walls and shows that special measures may be needed for tighter requirements.

Borehole stability is a central requirement. The document calls for stability to be demonstrated by calculations, trial excavations or comparable experience, and it identifies countermeasures where fluid loss, unstable ground or cavities are likely. The same execution logic applies to socketing, enlargements and raking piles, where geometry and ground conditions can make a method feasible or not.

Reinforcement, cover and spacing

The standard gives reinforcement design principles for bored piles, including handling, transport and installation of the cage. It sets minimum longitudinal reinforcement, bar spacing rules, transverse reinforcement spacing and the space needed for tremie pipes and other inserts.

Minimum and nominal cover are tied to EN 1992, but oSIST prEN 1536:2026 adds execution cover rules so the reinforcement is fully embedded and the cover zone is filled. In practice, this is what protects the steel and helps avoid honeycombing or cage damage during concreting.

Execution, supervision and records

Execution has to be planned, approved and carried out by qualified personnel using suitable equipment and methods. The document gives rules for working platforms, templates, starter casings, removal of obstructions, excavation, borehole cleaning, reinforcement installation, concreting, external grouting and trimming.

A key practical point is that concrete placement has to maintain a continuous monolithic pile, with controlled monitoring of concrete level and volume. Submerged concreting requires a tremie pipe, controlled immersion depth and checks on the support fluid. Continuous flight auger pile work has its own controls for drilling, withdrawal and concrete pumping.

Supervision, inspection, monitoring and testing are part of the quality management system. Records become part of the Geotechnical Construction Record (GCR) and have to capture the relevant excavation and concreting information for each element.

What terms does oSIST prEN 1536:2026 define?

• Execution specifications - the set of documents that defines the technical requirements, drawings and other information needed to execute the works.
• Bored pile - a pile formed by continuous or discontinuous excavation, with or without casing, and filled with a self-hardening material.
• Continuous flight auger pile (CFA pile) - a pile made by drilling with a continuous flight auger while concrete is pumped through the hollow stem as the auger is withdrawn.
• Partial replacement pile - a CFA-type pile where the ground is only partially displaced, not completely replaced.
• Support fluid - a bentonite, polymer, or bentonite-polymer fluid used to support the borehole.
• Self-hardening slurry - a suspension that supports the excavation during drilling and then hardens with time.
• Tremie pipe - a concreting pipe with watertight joints for placing concrete under submerged conditions.
• Integrity test - a test on an installed bored pile used to check the soundness of materials and, depending on the method, the pile geometry.

Who uses oSIST prEN 1536:2026?

oSIST prEN 1536:2026 is used by geotechnical designers, piling contractors, site supervisors, client representatives, quality managers and testing personnel involved in foundations, retaining walls, cut-off walls and underground works. They use it to define the execution method, specify materials, control excavation stability, check concreting, plan inspection and testing, and keep the required records.

What changed in oSIST prEN 1536:2026 from the previous edition?

oSIST prEN 1536:2026 will supersede EN 1536:2010+A1:2015. The foreword states that the revision has been substantially restructured and updated in content, and harmonized in particular with prEN 1538:2026.

Which standards are used with oSIST prEN 1536:2026?

• EN 206 - the base reference for concrete specification, performance, production and conformity, used for concrete, plastic concrete, aggregates, water, additions and admixtures.
• EN 13670 - supports execution of concrete structures, including on-site sampling, testing and concreting control.
• EN 1992 - provides concrete design rules used for reinforcement, precast concrete elements and cover.
• EN 1993 - provides steel design rules used for steel tubes and profile elements.
• EN 1994 - provides composite steel-concrete design rules where steel and concrete act together.
• EN 1997 - the geotechnical design framework that this standard complements, including planning, monitoring and maintenance references.
• EN 1538 - used for pile walls and for watertightness-related wall considerations.
• EN 10025-2 - the material standard for non-alloy structural steel used in steel elements.
• EN 10080 - the material standard for weldable reinforcing steel.
• EN 10210 and EN 10219 - the product standards for structural hollow sections used as steel tubes.
• EN 12715 - the reference for grouting when grout is used for injection or external grouting.
• EN 16228 - the safety standard for drilling and foundation equipment.
• EN ISO 10414-1 - the test method reference used for support-fluid properties such as density, viscosity, fluid loss and sand content.

What does the oSIST prEN 1536:2026 document contain?

The document includes figures that show pile types, rake, pile groups, pile walls and construction deviation terms. It also includes tables for support-fluid characteristics, watertightness classes, minimum longitudinal reinforcement and example inspection and testing plans.

Annex A gives practical guidance on watertightness for retaining walls, including design, concrete, joints and post-concreting issues. Annex B gives example inspection and testing plans for bored piles, CFA piles and shaft/base grouting, which helps teams build a site quality plan. The body of the document also sets out procedures for borehole support, cleaning, reinforcement placement, tremie concreting, casing extraction, grouting and trimming.

SLOVENSKI STANDARD
01-november-2026
Izvedba posebnih geotehničnih del - Uvrtani piloti
Execution of special geotechnical work - Bored piles
Ausführung von Arbeiten im Spezialtiefbau - Bohrpfähle
Exécution des travaux géotechniques spéciaux - Pieux forés
Ta slovenski standard je istoveten z: prEN 1536
ICS:
93.020 Zemeljska dela. Izkopavanja. Earthworks. Excavations.
Gradnja temeljev. Dela pod Foundation construction.
zemljo Underground works
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

DRAFT
EUROPEAN STANDARD
NORME EUROPÉENNE
EUROPÄISCHE NORM
September 2026
ICS Will supersede EN 1536:2010+A1:2015
English Version
Execution of special geotechnical work - Bored piles
Exécution des travaux géotechniques spéciaux - Pieux Ausführung von Arbeiten im Spezialtiefbau -
forés Bohrpfähle
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 288.
If this draft becomes a European Standard, 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.

This draft European Standard was established by CEN 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.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2026 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 1536:2026 E
worldwide for CEN national Members.

Contents Page
European foreword . 5
Introduction . 6
1 Scope . 7
Figure 1 — Examples for straight shaft piles and piles with shaft and base enlargement . 9
Figure 2 — Definition of the rake . 9
Figure 3 — Examples of pile groups . 9
Figure 4 — Examples of pile walls . 10
Figure 5 — Examples of bored piles . 11
2 Normative references . 11
3 Terms and definitions . 12
4 Information needed for the execution of the work . 15
4.1 General. 15
4.2 Specific information . 16
5 Geotechnical investigation . 17
6 Materials and products . 18
6.1 Constituents . 18
6.1.1 General. 18
6.1.2 Bentonite. 18
6.1.3 Polymers . 18
6.1.4 Cement . 19
6.1.5 Aggregates . 19
6.1.6 Water . 19
6.1.7 Additions . 19
6.1.8 Admixtures . 19
6.2 Support fluids . 19
Table 1 — Characteristics for bentonite based support fluid . 20
Table 2 — Characteristics for polymer based support fluid, made with synthetic polymer . 21
6.3 Concrete . 21
6.4 Grout . 22
6.5 Plastic concrete. 22
6.6 Self-hardening slurry . 22
6.7 Reinforcement . 23
7 Considerations related to the design . 23
7.1 General. 23
7.2 Piles forming a wall . 24
Table 3 — Classification of watertightness for secant pile walls . 25
7.3 Borehole stability . 25
7.4 Excavation . 27
7.5 Reinforcement for reinforced concrete bored piles . 28
7.5.1 Design principles . 28
7.5.2 Longitudinal reinforcement . 28
Table 4 — Minimum longitudinal reinforcement . 29
7.5.3 Transverse reinforcement . 30
7.6 Minimum and nominal cover . 30
Figure 6 — Concrete cover and reinforcement bar spacing in bored piles where the
reinforcement cage is installed before concrete placement . 31
7.7 Precast concrete elements . 32
7.8 Steel tubes and profile elements . 32
7.9 Recesses . 32
8 Execution . 33
8.1 General . 33
8.2 Installation tolerances . 33
8.2.1 Geometrical tolerances of piles . 33
Figure 7 — Definition of geometrical construction deviation terms . 34
8.2.2 Installation tolerances for reinforcement cages . 35
8.2.3 Tolerances for trimming . 35
8.3 Preliminary Works . 35
8.4 Excavation . 36
8.4.1 General . 36
8.4.2 Methods and tools . 37
8.4.3 Excavation sequence . 37
8.4.4 Unsupported boreholes . 38
8.4.5 Boreholes supported by support fluids . 38
8.4.6 Boreholes supported by casings . 39
8.4.7 Boreholes supported by soil-filled continuous flight augers . 39
8.4.8 Enlargements . 40
8.5 Cleaning the borehole . 40
8.6 Reinforcement . 40
8.6.1 General . 40
8.6.2 Coupling sections of reinforcement . 40
8.6.3 Spacers. 40
8.6.4 Installation of reinforcement or other elements . 41
8.7 Piles forming a wall . 41
8.8 Concreting . 42
8.8.1 General . 42
8.8.2 Concreting in dry conditions . 43
8.8.3 Concreting in submerged conditions . 43
8.8.4 Loss of immersion of tremie pipe or casing . 44
8.8.5 Extraction of temporary casings . 45
8.8.6 Concreting of continuous flight auger piles . 45
8.8.7 Precast concrete elements, steel tubes and profile elements . 46
8.9 External grouting . 46
8.10 Trimming . 47
9 Supervision, inspection, monitoring and testing . 47
10 Records . 48
11 Special Requirements . 49
Annex A (informative) Watertightness . 50
A.1 General . 50
A.2 Design Considerations impacting watertightness of retaining walls . 50
A.2.1 Principles . 50
Figure A.1 — Embedded retaining wall showing potential paths for groundwater ingress. 51
A.2.2 Concrete . 51
A.2.3 Joints . 51
A.2.4 Testing and control of watertightness . 51
A.3 Execution . 52
A.3.1 General. 52
A.3.2 Before Concreting . 52
A.3.3 Concreting Procedure . 52
A.3.4 Post-Concreting Considerations . 52
Annex B (informative) Example inspection and testing plan . 53
Table B.1 — Example inspection and testing plan for bored piles . 53
Table B.2 — Example inspection and testing plan for CFA piles . 58
Table B.3 — Example inspection and testing plan for shaft/base grouting (in addition to
Tables B.1 or B.2) . 59
Annex C (informative) Degree of obligation of the provisions . 61
Bibliography . 62
European foreword
This document (prEN 1536:2026) has been prepared by Technical Committee CEN/TC 288 “Execution of
special geotechnical works”, the secretariat of which is held by AFNOR.
This document is currently submitted to the CEN Enquiry.
This document will supersede EN 1536:2010 + A1:2015.
This document includes the following significant technical changes with respect to EN 1536:2010 +
A1:2015:
— revised substantially in its structure and content;
— harmonized in particular to align with prEN 1538:2026.
This document has been prepared under a standardization request addressed to CEN by the European
Commission. The Standing Committee of the EFTA States subsequently approves these requests for its
Member States.
Introduction
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.
The general scope of TC 288 is the standardization of the execution procedures for geotechnical works,
including considerations to design, provisions on materials, supervision, testing and monitoring, records
of the works executed, and on special requirements including sustainability.
WG25 has been charged to revise EN 1536:2015, with the subject area of bored piles, functioning as
foundations, retaining walls, or cut-off walls, but not “micro piles” of diameter less than 0,3 m. Barrettes,
which had been covered by EN 1536:2015, are now within the scope of prEN 1538:2026.
The design, planning and execution of bored piles call for experience and knowledge in this specialized
field. The execution phase requires skilled and qualified personnel, and the present standard cannot
replace the expertise of specialist contractor.
The document has been prepared to complement EN 1997, Eurocode 7: Geotechnical design. Clause 7
“Considerations related to design” of this document expands on design only where necessary (e.g. the
detailing of reinforcement) but shall provide full coverage of the execution and supervision requirements.
With regards to EN 13670, Execution of concrete structures, EN 1536 contains specific requirements for
bored piles as a concrete structure, such as the detailing of the reinforcement, the concrete placement
and the supervision of concreting process which are complementing the provisions of EN 13670.
Guidelines providing supplementary information, published by the European Federation of Foundation
Contractors and the Deep Foundation Institute, can be found in the bibliography. These are considered
to reflect state-of-the-art experience and contribute to a more elaborate understanding of the subject
matter.
1 Scope
1.1 This document establishes general principles for the execution of bored piles as per the execution
specifications.
NOTE 1 It is expected that the execution specifications define the execution standard to be applied based on
EN 1997 where relevant.
NOTE 2 Piles which deviate from the following clauses in this section can be considered as bored piles provided
the execution principles correspond to this document (see Clause 8).
1.2 This document applies to bored piles (see Figure 1) with:
— uniform cross-section (straight shaft);
— telescopically changing shaft dimensions;
— excavated base enlargements; or
— excavated shaft enlargements.
1.3 This document generally applies to bored piles with:
— a shaft diameter 0,3 m ≤ D ≤ 3,0 m;
— a depth to width ratio ≥ 5, with a depth ≥ 5 m;
NOTE This document can apply to bored piles with a shaft diameter of less than 0,3 m or more than 3,0 m
where the general principles allow the execution in accordance with this document.
1.4 This document applies to permanent or temporary works for:
— piled foundations,
— retaining walls.
NOTE This document can apply to rigid inclusions for ground improvement, and to cut-off walls.
1.5 This document applies to piles with the following rake (see Figure 2):
— n ≥ 4 (Θ ≤ 14°);
— n ≥ 3 (Θ ≤ 18°) for permanently cased piles
— n ≥ 10 (Θ ≤ 6°) for piles where the reinforcement cage is installed after concrete placement.
1.6 This document applies to bored piles with the following dimensions of the shaft or base
enlargements (see Figure 1):
a) base enlargements:
1) in non-cohesive ground: D /D ≤ 2;
B
2) in cohesive ground: D /D ≤ 3;
B
b) shaft enlargements in any ground: D /D ≤ 2;
E
c) slope of the enlargement in non-cohesive ground m ≥ 3;
1) in non-cohesive ground: m ≥ 3;
2) in cohesive ground: m ≥ 1.5.
1.7 This document applies to:
— single bored piles;
— bored pile groups (see Figure 3);
— walls formed by piles (see Figure 4).
1.8 This document applies to bored piles where excavation methods are either continuous or
discontinuous using support methods for stabilizing the excavation walls where required.
NOTE Where a continuous flight auger is used for excavation with partial displacement of soil, the pile is
considered a partial-replacement pile and its execution is covered by this document.
1.9 This document applies only to execution methods that allow the designed cross-sections to be
produced.
1.10 This document applies to bored piles (see Figure 5) constructed with:
— self-hardening slurries;
— unreinforced (plain) concrete incl. plastic concrete;
— reinforced concrete;
— concrete reinforced by structural elements (reinforcing elements);
— precast concrete (including prestressed concrete) elements or steel tubes where the annular gap
between the element or tube and the ground is filled by concrete.
NOTE Concrete can be substituted by grout, where applicable.
Key
DS Shaft diameter
D Shaft diameter for a given section (telescopic pile)
Si
D Base diameter
B
Figure 1 — Examples for straight shaft piles and piles with shaft and base enlargement

Key
D Rake
θ Angle of pile axis to the vertical
Figure 2 — Definition of the rake

Key
D Shaft diameter
ai Centre to centre spacing of the piles
Figure 3 — Examples of pile groups
a < D
a) Secant pile wall
a ≙ D
b) Contiguous pile wall
a > D
c) Spaced pile wall
Key
a Centre to centre spacing of the piles
D Shaft diameter
1 Lagging
p primary piles
s secondary piles
Figure 4 — Examples of pile walls
a) Use of plain b) Use of reinforced c) Use of structural elements,
concrete concrete steel section or tube

d) Use of precast concrete element as main or e) Use of steel tube as main or supplementary
supplementary structural member structural member
Key
1 Precast concrete element
2 Grout, or sanded grout
3 Temporary casing (extracted)
4 Uncased excavation
5 Unreinforced or reinforced concrete or grout, or sanded grout
D Shaft diameter
Figure 5 — Examples of bored piles
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 206 (all parts), Concrete — Specification, performance, production and conformity
EN 1538, Execution of special geotechnical works — Diaphragm walls
EN 1992 (all parts), Eurocode 2: Design of concrete structures
EN 1993 (all parts), Eurocode 3: Design of steel structures
EN 1994 (all parts), Eurocode 4: Design of composite steel and concrete structures
EN 1997 (all parts), Eurocode 7: Geotechnical design
EN 10025-2, Hot rolled products of structural steels - Part 2: Technical delivery conditions for non-alloy
structural steels
EN 10080, Steel for the reinforcement of concrete - Weldable reinforcing steel - General
EN 10210 (all parts), Hot finished structural hollow sections of non-alloy and fine grain steels
EN 10219 (all parts), Cold formed welded structural hollow sections of non-alloy and fine grain steels
EN 12715, Execution of special geotechnical work - Grouting
EN 13670, Execution of concrete structures
EN 16228 (all parts), Drilling and foundation equipment. Safety
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology 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/
Note 1 to entry: Terms not listed below can be defined in referenced standards, same terms can deviate as per
the specific field of application.
3.1
execution specifications
set of documents covering all relevant requirements, technical specifications and construction drawings
necessary for the execution of the works
3.2
bored pile
pile formed, with or without a casing, by continuous or discontinuous excavation methods, and filled with
a self-hardening material
3.3
continuous flight auger pile
CFA pile
pile formed by excavation means of a continuous flight auger through the hollow stem of which concrete
is pumped as the auger is extracted
3.4
partial replacement pile
as CFA where the ground is not completely replaced but partially displaced
3.5
raking pile
pile installed at an inclination related to the vertical (see Figure 2)
3.6
pile diameter
diameter of the pile at a given depth:
— for piles constructed with casings: equal to the nominal external diameter of the casing;
— for piles constructed without a casing: equal to the nominal diameter of the boring tool
3.7
enlarged base
base of a bored pile formed to have an area greater than that of its shaft (see Figure 3)
3.8
base grouting
pressure injection of grout below the base of an installed bored pile base in order to enhance performance
under load
3.9
shaft grouting
injection of grout carried out after concrete of the bored pile has set for the enhancement of skin friction
accomplished by the use of grouting pipes which are installed down the shaft, normally placed with the
bored pile reinforcement
3.10
concreting level
upper level to which concrete is cast in a borehole
3.11
cut-off level
designed level of the pile head
3.12
empty borehole
length of excavation from the working platform level to the cut-off level
3.13
temporary casing
steel tube used to maintain stability of a pile excavation (e.g. in unstable ground) which is withdrawn
during or after concrete placement
3.14
permanent casing
steel tube used to maintain stability of a pile excavation which is not withdrawn
3.15
starter casing
temporary casing of a certain length used to secure the borehole beneath the working platform level
3.16
lining
tubular element, generally made of thin steel, surrounding the pile shaft
3.17
support fluid
fluid consisting of bentonite or polymer or a combination of both used to support the borehole
Note 1 to entry: A support fluid can also convey cuttings, e.g. in direct and reverse circulation operations.
3.18
self-hardening slurry
suspension consisting of binders with or without additions and admixtures which acts as a support fluid
during excavation and hardens with time
3.19
grout
pumpable material (suspension, solution or resins, emulsion or mortar respectively “sanded grout”)
which hardens with time
Note 1 to entry: Grout is typically used for injection but can also be a substitute for concrete.
3.20
plastic concrete
low-strength, low-stiffness and low-permeability concrete with high deformation capacity
3.21
concreting pipe
a section or sections of pipe generally made of steel, surmounted by a hopper or chute for concrete
placement under dry conditions
3.22
tremie pipe
concreting pipe, with watertight joints for concrete placement under submerged conditioins
3.23
integrity test
test carried out on an installed bored pile to verify the soundness of materials and, depending on the
method used, the pile geometry
3.24
obstruction
natural or artificial local anomaly generally requiring special tools or methods for its removal and or
penetration
3.25
spacer
spacer pad
component of plastic or steel material or concrete (pad) fixed to the reinforcement cage to maintain the
predetermined gap width, usually the concrete cover
3.26
filter cake
formation of retained material such as bentonite and excavated soil from a suspension built up on the
face of a permeable medium by water drainage due to a pressure differential
3.27
trimming
removal of excess concrete above the designed cut-off level
3.28
excavation curve
diagram representing the excavation depth versus time
3.29
concreting curve
diagram representing the volume of poured concrete versus depth
4 Information needed for the execution of the work
4.1 General
4.1.1 Prior to the execution of the work, all necessary information shall be provided in the execution
specifications.
NOTE It is expected that the information includes technical requirements resulting from the function of the
piles.
4.1.2 This information should include:
— any legal or statutory restrictions;
— the location of main grid lines for setting out;
— the conditions of structures, roads, services, etc. adjacent to the work, including any necessary
surveys;
— a suitable quality management system, including supervision, inspection, testing, monitoring and
maintenance in accordance with EN 1997-1, Clause 10 and Clause 11.
NOTE Clause 9 of this document refers to supervision, inspection, monitoring and testing during execution.
4.1.3 The information regarding the site conditions shall cover, where relevant:
— the geometry of the site (boundary conditions, topography, access, slopes, headroom restrictions,
etc.);
— the existing underground structures, services, known contaminations, and archaeological
constraints;
— the environmental restrictions, including noise, vibration, pollution;
— the future or ongoing activities such as dewatering, tunnelling, deep excavations.
4.2 Specific information
4.2.1 The execution specifications shall include specific information.
4.2.2 The specific information shall include geotechnical information and data as specified in Clause 5.
NOTE Different from the reason for design of geotechnical structures, for execution the average ground
properties and their distribution are relevant to choose suitable work methods.
4.2.3 The specific information shall cover, where relevant:
— previous use of the site;
— adjacent foundations (types, loads and geometry);
— presence of obstructions in the ground (old masonry, anchors, etc.);
— presence of headroom restrictions;
— presence of archaeological remains;
— presence of natural and/or artificial cavities (mines, etc.);
— presence of contaminated ground, and type, extent and degree of contamination;
— any specific requirements for the piling works, in particular those pertaining to tolerances, quality of
materials, class of watertightness;
— where available, previous experience with bored piling or other foundations or underground works
on or adjacent to the site;
— proposed adjacent enabling or advance works such as underpinning, pre-treatment of ground,
dewatering, that may affect the piling works;
— functional requirements for instrumentation and monitoring of potentially affected structures;
— functional requirements for the material between the piles in the case of spaced bored pile walls.
4.2.4 Necessity, extent, procedure and content for any survey of the conditions of structures, roads,
utlilities, etc. adjacent to the works area, during execution, shall be specified.
4.2.5 Site survey required to determine reference conditions shall be carried out and be available prior
to the commencement of the works.
NOTE The results are useful to define the threshold values for any movement which can affect adjacent
structures.
5 Geotechnical investigation
5.1 The geotechnical investigation shall provide all necessary information for the execution of the
works.
NOTE The scope of the geotechnical investigation can exceed that is required in EN 1997 (series) for the design
of geotechnical structures.
5.2 Relevant experience of the execution of comparable foundation works under similar conditions in
the vicinity of the site should be taken into account.
5.3 The geotechnical investigation report shall be available in time for planning of the execution of the
bored piles (e.g the choice of method of execution).
5.4 The geotechnical investigation shall be checked to see whether it is sufficient for the execution of
the bored piles.
5.5 If the geotechnical investigations are not sufficient, a supplementary investigation shall be
conducted.
5.6 The geotechnical investigation report shall include specific information regarding the following
aspects, where relevant:
— the ground level at any point of investigation or testing relative to the recognized national datum or
to a fixed reference chart datum;
— ground properties necessary to determine work method, equipment and tools, and to estimate
performance as well as wear and tear, e.g. strength, density, abrasivity.
— piezometric levels and expected variation of all water tables and permeability of the ground;
— the presence of artesian conditions,
— presence of coarse, highly permeable ground or cavities (natural or artificial), e.g. to rate the risk for
sudden losses of support fluid;
— high ground-water velocities in underground strata which can cause difficulties during execution;
— presence, strength and deformation characteristics of soft soils, such as very soft clay or peat;
— presence of boulders or obstructions which can cause difficulties during excavation and, an
assessment of their size and frequency, when applicable;
— presence, position, level in both the longitudinal and transverse direction, strength and degree of
weathering and the extent and direction of fissuring of hard rock or other hard materials which can
cause difficulties during excavation and may require the use of special tools;
— presence, extent and thickness of any strata that can be sensitive to water infiltration or to stress
caused by piling tools (e.g. impact, percussion or vibration);
— chemistry of groundwater, soil and rock, and water temperatures if required;
— chemistry of waste materials;
— presence of pretreated ground, which can have an adverse effect during excavation;
— mining beneath the site;
— site stability problems (slope stability for instance).
6 Materials and products
6.1 Constituents
6.1.1 General
6.1.1.1 The constituents shall meet the requirements set in the respective European Standards, the
provisions valid in the place of use and the provisions given in the execution specifications.
6.1.1.2 The sources of supply of constituents shall be documented and shall not be changed without
prior notification.
6.1.2 Bentonite
6.1.2.1 In the absence of a specific European Standard for bentonite for the application in
geotechnical works, a suitable production quality system shall be in place to prove consistency in
production, and each delivery shall come with a conformity certificate.
NOTE Bentonite is a clay containing mainly the mineral montmorillonite and is used in support fluids, either
as a pure bentonite suspension or as an addition to polymer solutions. It is also used as a constituent part of
hardening slurries and of plastic concrete.
6.1.2.2 Bentonite used in bentonite suspensions shall not contain harmful constituents in such
quantities as can be detrimental to reinforcement or concrete.
6.1.2.3 The chemical and mineralogical composition of the bentonite shall be supplied
6.1.2.4 Representative data on characteristic technical parameters shall be supplied, proving
suitability for the field of application, at a minimum:
— moisture content,
— percentage by mass of grain size greater than 0,063 mm and
— Marsh viscosity of a suspension with a given composition, and
— fluid loss of a suspension with a given composition.
NOTE 0,063 mm can be substituted by 0,074 mm where the quality system refers to imperial units
6.1.3 Polymers
6.1.3.1 In the absence of a specific European Standard for polymers for the application in
geotechnical works, a suitable production quality system shall be in place to prove consistency in
production, and each delivery shall come with a conformity certificate.
NOTE Polymers are materials formed of molecules from chained monomeric units and are used in support
fluids as pure polymer solution, or as additives to enhance rheological effectiveness of bentonite suspensions.
6.1.3.2 Polymers used in polymer solutions shall not contain harmful constituents in such quantities
as can be detrimental to reinforcement or concrete.
6.1.3.3 The generic classification of the polymers shall be noted in the product declaration.
NOTE Typically, polymers are classified either natural, synthetic or natural-modified.
6.1.3.4 Representative data on characteristic technical parameters shall be supplied, proving
suitability for the field of application, at a minimum:
— molecular weight,
— Ionicity and charge density,
— type of polymer, and
— Marsh viscosity development curve for 24 h of a solution with a given composition.
6.1.4 Cement
6.1.4.1 Cement for concrete for bored piles shall comply with EN 206-1 and EN 206-3.
6.1.4.2 Cement for self-hardening slurries or grout shall conform to the provisions valid in the place
of use and shall have established suitability for use in the specific application.
NOTE In accordance with EN 206-3, cementitious compounds can be used, or cement can be substituted by
additions.
6.1.5 Aggregates
Aggregates shall comply with EN 206-1 and EN 206-3.
6.1.6 Water
6.1.6.1 Mixing water for concrete shall comply with EN 206-1 and EN 206-3.
6.1.6.2 The suitability of mixing water for support fluid shall be proven by testing or by comparable
experience.
NOTE Testing is usually not necessary for tap / potable water.
6.1.7 Additions
Additions shall comply with EN 206-1 and EN 206-3.
6.1.8 Admixtures
Admixtures shall comply with EN 206-1 and EN 206-3.
6.2 Support fluids
6.2.1 For the design of support fluids the presence of hydraulic binders which may result from
preparatory and/or additional work (e.g. injection, jet-grouting) or from operating modes (e.g.
production of a joint by biting into an existent pile), and possible effects of temperature and chemical
components of the ground and groundwater should be taken into account.
6.2.2 A support fluid shall be prepared with either bentonite, polymers, or a blend of bentonite and
polymers.
NOTE Additives can be necessary to adjust properties of the support fluid.
6.2.3 In certain cases, e.g. when the density of the support fluid has to be increased, suitable inert
materials may be added.
6.2.4 The support fluid, during excavation shall have and maintain properties to support the open
borehole.
6.2.5 Before concreting, the support fluid shall have properties to allow its displacement by the
concrete.
6.2.6 Bentonite based support fluids should comply with requirements as set out in Table 1.
NOTE 1 Other properties can be specified in special circumstances, for example in:
— soils or rock with high permeability or cavities where loss of bentonite can occur;
— high piezometric ground water levels (confined or artesian conditions);
— loose sand or soft soils (typically with q < 300 kPa or C < 15 kPa);
c u
— saltwater conditions.
NOTE 2 Prolonged exposure times can require
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