SIST EN 14679:2026
(Main)Execution of special geotechnical works - In-Situ Soil Mixing
- Abstract
This document specifies general principles for the execution, supervision, inspection, testing, monitoring and maintenance of in situ soil mixing works (Deep Mixing) carried out by two different methods: dry mixing and wet mixing.
Soil mixing considered in this document is limited to methods which involve:
- mixing by rotating mechanical mixing tools, including jetting and/or compressed air assistance, where the lateral support provided by the surrounding ground is not removed;
- different shapes and configurations of soilmix elements, either columns, panels, walls or any combination of more than one single element, with or without overlapping;
- treatment of soils and fills, including brownfields, sludges, etc., with possible limited penetration into the rock;
- mass mixing;
- environmental mixing, involving installation of containment and permeable reactive barriers and solidification/stabilization of contaminated soils and sludges.
This document does not apply to shallow soil stabilization, which consists of granulating the surface soil and mixing it with binder using stabilizing machines to improve performance. Shallow soil stabilization is in the scope of EN 16907-4.
- Status
- Not Published
- Public Enquiry End Date
- 24-Jul-2025
- Technical Committee
- KON - Structures
- Current Stage
- 5020 - Formal vote (FV) (Adopted Project)
- Start Date
- 24-Jun-2026
- Due Date
- 12-Aug-2026
- Completion Date
- 03-Nov-2026
SIST EN 14679:2026 sets the general principles for executing in situ soil mixing (Deep Mixing) works by dry mixing or wet mixing. It covers how the work is planned, supervised, inspected, tested, monitored and reported, including applications such as columns, panels, walls, mass mixing and environmental mixing.
The standard is for geotechnical projects where soil is mixed in place with binder to improve strength, stiffness, hydraulic conductivity or containment performance. It is aimed at the people who design, specify, carry out and verify specialist ground improvement and remediation works.
What does SIST EN 14679:2026 specify?
SIST EN 14679:2026 specifies the execution framework for in situ soil mixing works and the information, trials, controls and records needed to carry them out. The document is organized from project information and ground investigation through materials, planning, execution, quality control and reporting.
The scope covers rotating mechanical mixing tools, including jetting and/or compressed air assistance, while the surrounding ground continues to provide lateral support. It also covers different element shapes and configurations, treatment of soils and fills including brownfields and sludges, possible limited penetration into rock, mass mixing, and environmental mixing for containment and permeable reactive barriers.
The standard does not apply to shallow soil stabilization. That separate activity, which uses stabilizing machines to granulate surface soil and mix it with binder, is in the scope of EN 16907-4.
| Annex | What it covers |
|---|---|
| Annex A (informative) | Sample quality classes for soilmix samples and the sample quality expected from different sampling methods |
The main clauses cover:
- Clause 4 - information needed before execution
- Clause 5 - geotechnical investigation
- Clause 6 - materials and products
- Clause 7 - execution planning
- Clause 8 - execution
- Clause 9 - supervision, inspection, testing and monitoring
- Clause 10 - reporting
What are the key requirements of SIST EN 14679:2026?
SIST EN 14679:2026 focuses on getting the ground information, mix design, execution method and quality control aligned before work starts, then keeping them aligned during production. In practice, the standard links design assumptions to site data, trial work, field parameters and records so that the treated ground can be checked against the project requirements.
Pre-execution information and ground investigation
Clause 4 requires all relevant information to be provided before execution, including site constraints, nearby structures and utilities, environmental restrictions, storage and spoil arrangements, unexploded ordnance risk and the working platform. This matters because the mixing method, access, monitoring and spoil handling all depend on the actual site conditions.
Clause 5 requires a geotechnical investigation sufficient to determine the ground conditions in accordance with EN 1997-2. The Ground Investigation Report must include details such as fill, roots, cobbles, boulders, rock, swelling soils, organic soils, sensitive soils, cavities, groundwater conditions and, where relevant, soil classification, density, grain size distribution, mineralogy, organic content, strength, stiffness, hydraulic conductivity and contamination.
Materials and products
Clause 6 requires constituents to meet the relevant European Standards and the project specification, and their sources to be documented. For the binder, cement shall comply with EN 197-1, EN 197-5 or EN 197-6, while selection should generally follow EN 206 with suitability testing or comparable experience.
Water shall comply with EN 1008 unless a specific standard applies. Bentonite and polymer must not contain harmful constituents that could damage the soilmix element or reinforcement, and additions and admixtures shall comply with EN 206. Calcium aluminate cement shall not be used.
Planning the mix and proving it works
Clause 7 requires the soilmix design and the mixing process design to be based on comparable experience with the equipment and the ground conditions. The standard also requires planning the installation sequence and rate to avoid localized soil failure or unacceptable ground movement, especially near existing structures.
Where comparable experience is not available, a suitability study shall be carried out before work starts. That study may include laboratory and/or field trials, should cover each relevant geotechnical unit, and must establish at least the binder type and content and the water to binder ratio appropriate to the process. If field trials are used, the blade rotation number or mixing factor should be determined.
Clause 7 also requires a method statement before work starts. It should set out the work scope, ground description, element geometry and pattern, mixing tool, process parameters, site areas, plant, spoil return management, reinforcement, guides and how interruptions will be handled.
Execution and tolerances
Clause 8 requires the site to be prepared to suit the design and local conditions, with access, working platform stability, storage space and spoil handling in place. Materials delivered to site must be checked against the specification and protected so their performance is not harmed.
The equipment must be capable of carrying out the method statement and meeting the tolerances. For production control, the standard requires recording the key operating parameters for the relevant method, such as treatment time, depth, advance or withdrawal speed, rotation speed, slurry or binder feed, pressure and consumption.
Clause 8 also requires the position of each element to be identified before installation, with process control used to achieve the required soilmix properties. It sets tolerances for location, verticality, top and bottom level and overlap, and it treats mass mixing separately from element-based work. If unexpected obstructions remain in place, the affected area must be marked and the adjacent design adjusted.
Supervision, testing, monitoring and reporting
Clause 9 requires a Quality Control Plan (QCP) before work starts. The QCP must define the tests, inspection methods, frequencies, acceptance conditions and response to nonconformity, and it must be based on the design’s supervision, inspection and monitoring plans.
Testing may include strength, deformation, density, hydraulic conductivity and, for environmental applications, contaminant leaching. Sampling method and sample quality matter: Annex A classifies samples from A to D, and only quality classes A and B should be used to verify soilmix material properties.
Clause 10 requires a Geotechnical Construction Record (GCR) in accordance with EN 1997-1. The record should capture the execution parameters, site conditions, materials, tolerances, reinforcement details, deviations and problems so the work can be checked and reviewed later.
What terms does SIST EN 14679:2026 define?
- Binder - a chemically reactive material, including cement or similar products, with or without additions and admixtures, used to form the soilmix material.
- Blade rotation number (BRN) - an indicator of mixing energy for paddle-type tools, expressed as the total number of blade rotations per metre of tool movement.
- Mixing factor - an energy indicator similar to BRN, used for mixing tools other than paddle-type vertical axis tools.
- Quality Control Plan (QCP) - the project-specific document that sets out quality control, quality assurance, inspections, testing, monitoring and corrective action.
- Soilmix material - the treated soil produced by mixing in situ soil with binder, with improved properties compared with the original soil.
- Soilmix element - the treated volume produced in situ during one installation sequence using a mixing tool.
- Suitability study - laboratory and/or field trials used to confirm the soilmix design and/or process design.
- Wet mixing - mechanical disaggregation of the soil in situ and mixing it with slurry.
Who uses SIST EN 14679:2026?
SIST EN 14679:2026 is used by geotechnical engineers, specialist soil mixing contractors, project designers, site supervisors, quality managers and inspection teams. It is also relevant to buyers and clients who need to specify and verify deep mixing work.
Typical uses include foundation support, ground improvement, retaining and cut-off walls, treatment of contaminated soils and sludges, containment barriers and permeable reactive barriers. The document is also relevant where working near existing structures, utilities, excavations or sensitive ground conditions requires defined control of execution and monitoring.
What changed in SIST EN 14679:2026 from the previous edition?
SIST EN 14679:2026 supersedes EN 14679:2005.
Which standards are used with SIST EN 14679:2026?
SIST EN 14679:2026 relies on several European Standards for materials, design and testing:
- EN 197-1, EN 197-5 and EN 197-6 - define acceptable cements for soil mixing.
- EN 206 (all parts) - supports selection of binder, additions and admixtures and their conformity.
- EN 1997-1 - provides the geotechnical design basis and the framework for the GCR and supervision plans.
- EN 1997-2 - sets the basis for ground investigation.
- EN 1997-3:2025 - supports properties of soilmix material and the control/testing framework.
- EN 1008 - defines the suitability of mixing water.
- EN ISO 14688 (all parts) - supports soil identification and classification used in the ground investigation.
The foreword says the document is prepared to stand alongside EN 1997-1:2024, EN 1997-2:2024 and EN 1997-3:2025.
What does the SIST EN 14679:2026 document contain?
The document includes a design-and-execution flow chart, a table of minimum production parameters to record during soil mixing, and a reporting table for the Geotechnical Construction Record. It also includes a sampling appendix that classifies sample quality and links sample quality to the sampling methods used.
It provides the practical framework for laboratory trials, field trials, execution control, inspection and acceptance checks rather than reproducing the design itself. Annex A is used when judging whether a sample is good enough to support property verification, especially for strength and other performance testing.
The document also gives formulas and indicators for process control, including BRN and mixing factor, so the contractor can quantify mixing energy and compare it with the target process. That is important when the work specification depends on repeatable mixing quality rather than on a single visual check.
Relations
- Effective Date
- 01-Dec-2026
- Effective Date
- 01-Dec-2026
- Effective Date
- 30-Sep-2026
- Effective Date
- 30-Sep-2026
- Effective Date
- 30-Sep-2026
- Effective Date
- 30-Sep-2026
- Effective Date
- 30-Sep-2026
- Effective Date
- 30-Sep-2026
- Effective Date
- 30-Sep-2026
- Effective Date
- 30-Sep-2026
- Effective Date
- 23-Sep-2026
- Effective Date
- 23-Sep-2026
- Effective Date
- 02-Sep-2026
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Frequently Asked Questions
SIST EN 14679:2026 is a draft published by the Slovenian Institute for Standardization (SIST). Its full title is "Execution of special geotechnical works - In-Situ Soil Mixing". This standard covers: This document specifies general principles for the execution, supervision, inspection, testing, monitoring and maintenance of in situ soil mixing works (Deep Mixing) carried out by two different methods: dry mixing and wet mixing. Soil mixing considered in this document is limited to methods which involve: - mixing by rotating mechanical mixing tools, including jetting and/or compressed air assistance, where the lateral support provided by the surrounding ground is not removed; - different shapes and configurations of soilmix elements, either columns, panels, walls or any combination of more than one single element, with or without overlapping; - treatment of soils and fills, including brownfields, sludges, etc., with possible limited penetration into the rock; - mass mixing; - environmental mixing, involving installation of containment and permeable reactive barriers and solidification/stabilization of contaminated soils and sludges. This document does not apply to shallow soil stabilization, which consists of granulating the surface soil and mixing it with binder using stabilizing machines to improve performance. Shallow soil stabilization is in the scope of EN 16907-4.
This document specifies general principles for the execution, supervision, inspection, testing, monitoring and maintenance of in situ soil mixing works (Deep Mixing) carried out by two different methods: dry mixing and wet mixing. Soil mixing considered in this document is limited to methods which involve: - mixing by rotating mechanical mixing tools, including jetting and/or compressed air assistance, where the lateral support provided by the surrounding ground is not removed; - different shapes and configurations of soilmix elements, either columns, panels, walls or any combination of more than one single element, with or without overlapping; - treatment of soils and fills, including brownfields, sludges, etc., with possible limited penetration into the rock; - mass mixing; - environmental mixing, involving installation of containment and permeable reactive barriers and solidification/stabilization of contaminated soils and sludges. This document does not apply to shallow soil stabilization, which consists of granulating the surface soil and mixing it with binder using stabilizing machines to improve performance. Shallow soil stabilization is in the scope of EN 16907-4.
SIST EN 14679:2026 is classified under the following ICS (International Classification for Standards) categories: 93.020 - Earthworks. Excavations. Foundation construction. Underground works. The ICS classification helps identify the subject area and facilitates finding related standards.
SIST EN 14679:2026 has the following relationships with other standards: It is inter standard links to SIST EN 14679:2005, SIST EN 14679:2005/AC:2007, kSIST FprEN 1997-1:2024, SIST EN 16228-5:2014+A1:2022, SIST EN 16228-4:2014+A1:2022, SIST EN 16228-7:2014+A1:2022, SIST EN 16228-3:2014+A1:2022, SIST EN 16228-2:2014+A1:2022, SIST EN 16228-6:2014+A1:2022, SIST EN 16228-1:2014+A1:2022, SIST EN 206-2:2026, SIST EN 206-1:2026, SIST EN 1008:2003. Understanding these relationships helps ensure you are using the most current and applicable version of the standard.
SIST EN 14679:2026 is available in PDF format for immediate download after purchase. The document can be added to your cart and obtained through the secure checkout process. Digital delivery ensures instant access to the complete standard document.
Standards Content (Sample)
SLOVENSKI STANDARD
oSIST prEN 14679:2025
01-julij-2025
Izvedba posebnih geotehničnih del - Mešanje zemljin na mestu
Execution of special geotechnical works - In-Situ Soil Mixing
Ausführung von besonderen geotechnischen Arbeiten (Spezialtiefbau) - Tiefreichende
Bodenstabilisierung
Exécution des travaux géotechniques spéciaux — Malaxage des sols en place
Ta slovenski standard je istoveten z: prEN 14679
ICS:
93.020 Zemeljska dela. Izkopavanja. Earthworks. Excavations.
Gradnja temeljev. Dela pod Foundation construction.
zemljo Underground works
oSIST prEN 14679:2025 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
oSIST prEN 14679:2025
oSIST prEN 14679:2025
DRAFT
EUROPEAN STANDARD
prEN 14679
NORME EUROPÉENNE
EUROPÄISCHE NORM
May 2025
ICS 93.020 Will supersede EN 14679:2005
English Version
Execution of special geotechnical works - In-Situ Soil
Mixing
Exécution des travaux géotechniques spéciaux - Ausführung von besonderen geotechnischen Arbeiten
Colonnes de sol traité (Spezialtiefbau) - Tiefreichende Bodenstabilisierung
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
© 2025 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 14679:2025 E
worldwide for CEN national Members.
oSIST prEN 14679:2025
prEN 14679:2025 (E)
Contents Page
European Foreword . 3
1 Scope . 4
2 Normative references . 4
3 Terms and definitions . 4
4 Information needed for the execution of the work . 9
4.1 General. 9
4.2 Specific information . 9
5 Geotechnical investigation . 10
5.1 General. 10
5.2 Specific information . 10
6 Materials and products . 11
6.1 General. 11
6.2 Binder. 11
6.3 Water . 12
6.4 Bentonite and Polymer . 12
6.5 Additions . 12
6.6 Admixtures . 12
6.7 Reinforcement . 12
6.8 Geosynthetics . 12
7 Execution planning . 12
7.1 General. 12
7.2 Soilmix design and mixing process design . 14
7.3 Suitability study. 14
7.4 Laboratory trials . 14
7.5 Field trials . 14
7.6 Method statement . 15
8 Execution . 16
8.1 Site preparation and material inspection . 16
8.2 Equipment . 16
8.3 Soil mixing . 17
8.4 Placing the reinforcement . 18
8.5 Tolerances . 19
9 Supervision, inspection, testing and monitoring . 20
9.1 General. 20
9.2 Supervision . 20
9.3 Inspection . 20
9.4 Testing . 21
9.5 Monitoring . 23
10 Reporting . 23
Annex A (informative) Sample Quality . 25
Bibliography . 28
oSIST prEN 14679:2025
prEN 14679:2025 (E)
European Foreword
This document (prEN 14679:2025) 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 CEN Enquiry.
This document will supersede EN 14679:2005.
The document has been prepared to stand alongside EN 1997-1:2024, EN 1997-2:2024 and
EN 1997-3:2025. This document provides full coverage of the construction and supervision
requirements.
oSIST prEN 14679:2025
prEN 14679:2025 (E)
1 Scope
This document specifies general principles for the execution, supervision, inspection, testing and
monitoring of in situ soil mixing works (Deep Mixing) carried out by two different methods: dry mixing
and wet mixing.
Soil mixing considered in this document is limited to methods which involve:
— mixing by rotating mechanical mixing tools, including jetting and/or compressed air assistance,
where the lateral support provided by the surrounding ground is not removed;
— different shapes and configurations of soil mixing elements, either columns, panels, walls or any
combination of more than one single element, with or without overlapping;
— treatment of soils and fills, including brownfields, sludges, etc., with possible limited penetration into
the rock;
— mass mixing;
— environmental mixing, involving installation of containment and permeable reactive barriers and
solidification/stabilization of contaminated soils and sludges.
This standard does not apply to shallow soil stabilization, which consists of granulating the surface soil
and mixing it with binder using soil stabilizing machines to improve soil performance as an alternative
to soil replacement, typically in road works.
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 197-1, Cement – Part 1: Composition, specification and conformity criteria for common cements
EN 197-5, Cement – Part 5: Cement Portland-composite cement CEM II/C-M and Composite cement CEM VI
EN 197-6, Cement — Part 6: Cement with recycled building materials
EN 206 (all parts), Concrete – Specification, performance, production and conformity
EN 1997-1, Eurocode 7: Geotechnical design – Part 1: General rules
EN 1997-2, Eurocode 7: Geotechnical design – Part 2: Ground properties
EN 1997-3:2025, Eurocode 7: Geotechnical design – Part 3: Geotechnical structures
EN 1008, Mixing water for concrete - Specification for sampling, testing and assessing the suitability of
water, including water recovered from processes in the concrete industry, as mixing water for concrete
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:
oSIST prEN 14679:2025
prEN 14679:2025 (E)
— ISO Online browsing platform: available at https://www.iso.org/obp/
— IEC Electropedia: available at https://www.electropedia.org/
3.1
admixture
constituent added during the mixing process in small quantities related to binder mass to modify soilmix
or binder properties
3.2
addition
additive
fine-grained and inorganic constituent used to improve certain properties of soilmix or to achieve special
properties or to partially replace cement, e.g. filler aggregates, fly ash, granulated blast furnace slag
3.3
binder
chemically reactive material, including cement or similar products, with or without additions and
admixtures
Note 1 to entry: For environmental applications other materials with binder-like properties can be used
to meet the intended purpose
3.4
binder content [kg/m ]
ratio of mass of dry binder to volume of soil to be treated
Note 1 to entry: Binder quantity can also be defined as ratio of mass of dry binder to mass of dry soil, expressed in
percentage.
3.5
binder content in-place [kg/m ]
ratio of mass of dry binder to volume of mixture, which is the volume of the soil to be treated plus the
volume of the slurry for the wet method or the volume of the dry binder for the dry method
3.6
blade rotation number
BRN
indicator for mixing energy, applicable to paddle-type mixing tools, showing the total number of mixing
blade rotations per metre of tool movement
Note 1 to entry: Examples of BRN evaluation include the following formulas:
— for single-stroke wet mixing and slurry injection below the blades
R
R
p
w
BRN = Σ M +
VV
p w
— for single-stroke dry mixing and binder injection above the blades
R
w
BRN = Σ M
V
w
oSIST prEN 14679:2025
prEN 14679:2025 (E)
where:
BRN blade rotation number (rev./m),
ΣM total number of mixing blades (a full-diameter blade is counted as two blades, i.e. M = 2)
R rotational speed of the mixing tool during penetration (rev./min),
p
Vp penetration speed (m/min),
R rotational speed of the mixing tool during withdrawal (rev./min),
w
Vw withdrawal speed (m/min),
In the case of multiple restrokes along the entire treatment depth, the resulting blade rotation number is the sum
of the BRN values calculated for each stroke of the mixing tool. Other formulae can also be used to suit a particular
mixing tool configuration and process.
3.7
dry mixing
process of mechanical disaggregation of the soil in situ and its mixing with dry binder
3.8
hybrid mixing
wet mixing with the inclusion of a secondary process to assist or extend the mixing, e.g. using jetting
and/or compressed air
3.9
mass mixing
in situ treatment of the entire soil block, divided into working cells, using dry or wet mixing, carried out
repeatedly in vertical and horizontal directions through the soil mass using various mixing tools
Note 1 to entry: Usual practice is to treat in one sequence a cell of soil within the operational range of the machine.
Treatment depth is typically limited to about 8 m in favourable ground conditions.
3.10
mixing equipment
equipment with different mixing tools rotating around a vertical or horizontal axis, vertical trenching
tools, jet-assisted tools, cutters or drums, in single or multiple arrangements
Note 1 to entry: For tubular mixing, the mixing tools are arranged inside a casing.
3.11
mixing factor
indicator for mixing energy, similar to blade rotation number, but applicable to any soil mixing tool
(horizontal axis rotation, trencher, or other) except paddle-type vertical axis rotation tools
Note 1 to entry: The corresponding formula can be specified by the specialist contractor, along with a specification
of the minimum target mixing factor to be applied.
3.12
mixing process
mechanical disaggregation of the soil structure and dispersion of binder in the soil with or without the
use of added water, jetting or compressed air
3.13
mixing tool
tool used to disaggregate the soil and distribute and mix binder with the soil in situ
oSIST prEN 14679:2025
prEN 14679:2025 (E)
3.14
penetration
phase of mixing process cycle in which the mixing tool is delivered to the appropriate depth
3.15
penetration speed [m/min]
vertical movement per unit time of the mixing tool during penetration
Note 1 to entry: Can also be expressed as vertical movement per tool revolution, e.g. mm/rev.
3.16
process design
selection of an appropriate mixing method and mixing tool, and specification of the mixing process
parameters and binder or slurry feeding rates to meet the design requirements of the project
3.17
quality control plan
QCP
document containing the project-specific quality control and quality assurance programme to meet the
design requirements, including supervision, inspection, testing, monitoring and corrective action in case
of nonconformity
3.18
retrieval or withdrawal
phase of mixing process cycle in which the mixing tool is moved from bottom depth to the ground surface
3.19
rotation speed [rev./min]
number of revolutions of the mixing tool per unit time
3.20
sample quality class
classification of the samples extracted from the soil mix element according to their surface, structure,
amount of irregularities and composure
3.21
slurry
colloidal mixture of water and binder that assists in loosening the soil for effective mixing and improving
the characteristics of the in-situ soil upon setting
3.22
soil mixing
in situ ground treatment in which soil is blended with binder
3.23
soilmix design
ratios of soil, binder and water required to meet the design requirements of the treated soil
3.24
soilmix material
product of soil mixing, consisting of a mixture of the in-situ soil and binder, providing a material with
improved strength, hydraulic conductivity, and/or stiffness upon setting compared to the original soil
(also referred to as treated soil)
oSIST prEN 14679:2025
prEN 14679:2025 (E)
Note 1 to entry: For environmental applications it can be necessary to consider chemical properties.
3.25
soilmix element
volume of treated soil that is produced in situ during a single installation sequence using a mixing tool
Note 1 to entry: The geometry of the mixing tool and the mixing process determine the shape and size of the cross
section of an element (not applicable to mass mixing).
3.26
spoil return
surplus mixture of disaggregated soil or weak rock and dispersed binder, arising from the mixing process
3.27
stroke
one complete cycle (penetration and withdrawal) of the mixing process along the entire depth of
treatment (not applicable to mass mixing)
3.28
suitability study
laboratory and/or field trials to confirm soilmix design and/or process design
3.29
water to binder ratio
weight of water added to the dry binder divided by the weight of the dry binder
Note 1 to entry: For wet mixing, the total water to binder ratio of the soilmix material is the weight of slurry water
plus the weight of soil water divided by the weight of dry binder.
3.30
wet mixing
process of mechanical disaggregation of the soil in situ and its mixing with slurry
3.31
withdrawal speed [m/min]
vertical movement per unit time of the mixing tool during retrieval
Note 1 to entry: Can also be expressed as vertical movement per tool revolution, e.g. mm/rev.
oSIST prEN 14679:2025
prEN 14679:2025 (E)
4 Information needed for the execution of the work
4.1 General
4.1.1 Prior to the execution of the work, all relevant information shall be provided.
4.1.2 This information should include:
— any legal or statutory restrictions;
— the location of main grid lines for setting out element positions;
— the location and conditions of buildings, roads, utilities, etc., adjacent to the work area, including any
necessary surveys;
— a suitable quality management system, including supervision, inspection, testing and monitoring;
— the geometry of the site (boundary conditions, topography, access, slopes, etc.);
— available space for storage, treatment and/or disposal of spoil;
— archaeological constraints;
— potential presence of unexploded ordnance and its location;
— the environmental restrictions, including noise, vibration, pollution;
— future or ongoing construction activities, such as dewatering, tunnelling, deep excavations;
— the preparation and construction details of any working platform required for soil mixing in
accordance with the EFFC/DFI Guide.
4.2 Specific information
4.2.1 The specific information shall cover, where relevant:
— execution specifications;
— required properties of soilmix material;
— previous use of the site;
— adjacent structures and their foundations (types, state, loads and geometry);
— geotechnical information and data as specified in Clause 5;
— presence of any obstructions in the ground (old masonry, anchors, concrete, blocks and boulders,
etc.);
— certificate or written confirmation of removal of all unexploded ordnance;
— presence of headroom restrictions;
— presence of natural and/or man-made cavities (e.g. mines);
oSIST prEN 14679:2025
prEN 14679:2025 (E)
— presence of contaminated ground and type, extent and degree of contamination;
— any specific requirements for the soil mixing work, in particular those pertaining to tolerances,
quality of materials and methods of testing;
— where available, previous comparable experience with soil mixing works pertinent or relevant to the
site;
— proposed adjacent enabling or advance works such as underpinning, pre-treatment of soil,
dewatering;
— the extent and type of instrumentation required to monitor potentially affected structures, including
baseline measurements to establish reference conditions.
NOTE For underwater soil mixing operations, further specific information is needed to assess working
conditions and limit uncontrolled spread of spoil.
5 Geotechnical investigation
5.1 General
5.1.1 The investigations shall be sufficient to allow the determination of the ground conditions in
accordance with the requirements of EN 1997-2.
5.2 Specific information
5.2.1 In addition to EN 1997-2, the Ground Investigation Report shall contain the following information
relevant for the execution of soil mixing:
— the composition, lateral extent, thickness and firmness of the surface stratum, tree roots, fill, etc.;
— presence of cobbles or boulders, cemented layers or underlying rock that can cause difficulties for
the execution or could require special methods or tools;
— presence of swelling soil (e.g. montmorillonite);
— overconsolidated stiff clays;
— organic soils (e.g. peat);
— sensitive soils;
— water content of soils;
— cavities, voids or fissures;
— piezometric levels and/or flow of groundwater, its variation and possible artesian pressure.
5.2.2 Where relevant, the following additional information should be provided:
5.2.2.1 Physical and state characteristics of soils to be treated:
— classification in accordance with EN ISO 14688 (all parts);
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— consistency limits;
— density;
— grain size distribution;
— mineralogy;
— organic content.
5.2.2.2 Properties of soils to be treated:
— stiffness and degree of consolidation;
— strength;
— hydraulic conductivity.
5.2.2.3 Environmental, chemical and biological characteristics:
— ground and groundwater quality, e.g. contamination, aggressiveness, chemistry, pH- value, type and
concentration of ions and metals.
6 Materials and products
6.1 General
6.1.1 The constituents shall meet the requirements of the respective European Standards and those
given in the project specification.
NOTE For more information, see also local regulations.
6.1.2 The sources of supply for constituents shall be documented and shall not be changed without
prior notification.
6.2 Binder
6.2.1 Cement for soil mixing shall comply with EN 197-1, EN 197-5 or EN 197-6.
6.2.2 The selection of binder in relation to the exposure classes should in general be in accordance with
EN 206 (all parts). Given the differences between concrete and soilmix material, suitability testing or
comparable experience should be used to assist in this selection.
6.2.3 Additions (as defined in EN 206 (all parts)) may be used as cement replacement where the
required performance is proven by suitability testing or comparable experience.
NOTE Other binders can cause adverse reactions with the ground.
6.2.4 Calcium aluminate cement shall not be used.
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6.3 Water
6.3.1 In absence of specific standard, mixing water shall comply with EN 1008.
6.3.2 Saline water may be used providing there are no detrimental effects to embedded steel.
NOTE The salinity can also influence the choice of binder.
6.4 Bentonite and Polymer
6.4.1 Bentonite or polymer used shall not contain harmful constituents in such quantities that could be
detrimental to soil mixing elements or their reinforcement.
6.4.2 The chemical and mineralogical composition of the bentonite shall be considered.
6.4.3 The chemical composition of polymer shall be considered.
6.5 Additions
6.5.1 Additions used shall comply with EN 206 (all parts).
6.6 Admixtures
6.6.1 Admixtures used shall comply with EN 206 (all parts).
6.7 Reinforcement
6.7.1 Where reinforcement is used, the material shall comply with the relevant European standard.
6.8 Geosynthetics
6.8.1 Where geosynthetics are required within soilmix elements, they shall comply with the relevant
European standards.
NOTE Interlocking geomembranes can be used to achieve very low permeability.
7 Execution planning
7.1 General
7.1.1 Generalized flow chart of soil mixing projects as shown in Figure 1 should be used prior to and
for execution planning.
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Figure 1 — Design and execution flow chart of soil mixing projects
7.1.2 The determination of the properties of the soilmix material shall be in accordance with
EN 1997-3:2025, Clause 12.
7.1.3 The sequence and rate of installation of the soilmix elements shall be planned to avoid localized
soil failure or unacceptable ground movement, taking into account the setting and curing time of the
soilmix material.
NOTE Soilmix elements installed in close proximity to existing structures and foundations can affect their
stability or serviceability.
7.1.4 The execution of other foundation works at a distance of less than 5 m and within a week after
the installation of the soilmix element, that could affect its condition, should be avoided.
NOTE The risk is increased if foundation works (e.g. piling, excavation, compaction, etc.) is carried out during
and immediately after the installation of the soilmix element due to the limited strength at young ages of the soilmix
material.
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7.1.5 Where the soilmix element is designed for end-bearing capacity, the mixing tool and process shall
be prescribed to ensure a proper treatment at the base of the element.
7.1.6 In critical ground conditions with unpredictable interactions between the binder and soil,
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