SIST EN 14731:2006

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Execution of special geotechnical works - Ground treatment by deep vibrationLMRExécution de travaux géotechniques spéciaux - Amélioration des massifs de sol par vibrationAusfürung von besonderen geotechnischen Arbeiten (Spezialtiefbau) - Baugrundverbesserung durch Tiefenrüttelverfahren93.020Zemeljska dela. Izkopavanja. Gradnja temeljev. Dela pod zemljoEarthworks. Excavations. Foundation construction. Underground worksICS:SIST EN 14731:2006enTa slovenski standard je istoveten z:EN 14731:200501-februar-2006SIST EN 14731:2006SLOVENSKI
STANDARD







EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN 14731September 2005ICS 93.020 English VersionExecution of special geotechnical works - Ground treatment bydeep vibrationExécution de travaux géotechniques spéciaux -Amélioration des massifs de sol par vibrationAusfürung von besonderen geotechnischen Arbeiten(Spezialtiefbau) - Baugrundverbesserung durchTiefenrüttelverfahrenThis European Standard was approved by CEN on 8 August 2005.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the Central Secretariat or to any CEN member.This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the responsibility of a CEN member into its own language and notified to the Central Secretariat has the same status as the officialversions.CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia,Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre: rue de Stassart, 36
B-1050 Brussels© 2005 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 14731:2005: E



EN 14731:2005 (E) 2 Contents page Foreword.4 1 Scope.5 2 Normative references.5 3 Terms and definitions.6 4 Information needed for the execution of the work.7 4.1 General.7 4.2 Special features for ground treatment by deep vibration.7 5 Geotechnical investigation.8 5.1 General.8 5.2 Specific aspects for deep vibratory compaction.8 5.3 Specific aspects for vibrated stone columns.9 6 Materials and products.9 6.1 General.9 6.2 Materials for deep vibratory compaction.9 6.3 Materials for vibrated stone columns.9 7 Considerations related to design.10 7.1 General.10 7.2 Selection of treatment method.10 7.3 Design verification.11 7.4 Extent and layout of treatment.11 7.5 Sequence of treatment.11 8 Execution.12 8.1 General.12 8.2 Site preparation.12 8.3 Setting out.12 8.4 Treatment.12 9 Supervision, testing and monitoring.13 9.1 Supervision and monitoring.13 9.2 Testing.14 10 Records.15 10.1 Records in connection with the execution of the ground treatment.15 10.2 Records at completion of the ground treatment.16 11 Special requirements.16 11.1 General.16



EN 14731:2005 (E) 3 11.2 Safety.16 11.3 Environmental protection.16 11.4 Impact on adjacent structures.17 Annex A (informative)
Deep vibratory compaction.18 Annex B (informative)
Installation of vibrated stone columns.20 B.1 General.20 B.2 Dry top-feed process.20 B.3 Wet process.21 B.4 Dry bottom-feed process.22 Bibliography.24



EN 14731:2005 (E) 4 Foreword This European Standard (EN 14731:2005) has been prepared by Technical Committee CEN/TC 288 “Execution of special geotechnical works”, the secretariat of which is held by AFNOR. 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 March 2006, and conflicting national standards shall be withdrawn at the latest by March 2006. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.



EN 14731:2005 (E) 5 1 Scope This European Standard is applicable to the planning, execution, testing and monitoring of ground treatment by deep vibration achieved by depth vibrators and compaction probes. The following types of treatment are covered by this European Standard:  deep vibratory compaction to densify the existing ground;  vibrated stone columns to form a stiffened composite ground structure by the insertion of granular material which itself shall be densified. Generally, stone columns have a diameter greater than 0,6 m and lower than 1,2 m. The following treatment methods are covered by this European Standard:  methods in which depth vibrators, containing oscillating weights which cause horizontal vibrations, are inserted into the ground;  methods in which compaction probes are inserted into the ground using a vibrator which remains at the ground surface and which in most cases oscillates in a vertical mode. Treatment methods are outlined in Annexes A and B. The following treatment methods, among others, are not included in this European Standard:  methods in which sand or stone columns are installed by means of impact or top vibratory driven casing;  methods in which very stiff columns are formed either by the addition of cement to granular material or by the use of concrete or any other binder;  dynamic compaction and other methods in which some form of treatment is applied to the ground surface;  explosive compaction. 2 Normative references The following referenced documents are indispensable for the application of this European Standard. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN 791, Drill rigs – Safety EN 996, Piling equipment – Safety requirements EN 1990, Eurocode: Basis of structural design EN 1997-1:2004, Eurocode 7: Geotechnical design – Part 1: General rules prEN 1997-2, Eurocode 7: Geotechnical design – Part 2: Ground investigation and testing



EN 14731:2005 (E) 6 3 Terms and definitions For the purposes of this European Standard, the following terms and definitions apply. Additional descriptions of some of the ground treatment methods are given in Annexes A and B. 3.1 deep vibratory compaction type of ground treatment by deep vibration in which the main purpose is to densify the soil. The treatment is applicable to many granular soils and normally results in increased strength and stiffness, reduced permeability and reduced susceptibility to liquefaction 3.2 vibrated stone columns1) type of ground treatment by deep vibration in which a depth vibrator is used to form continuous stone columns from the maximum depth of penetration up to the ground surface, and hence to form a stone column/soil structure which should have an increased strength and stiffness compared with the ground in an untreated state. The treatment is applicable to a wide range of soils and in granular soils some densification may also be achieved. Three installation processes, the dry top-feed process, the wet process and the dry bottom-feed process are described in Annex B 3.3 vibrating tool item of equipment which is inserted into the ground to cause vibration at depth; commonly a depth vibrator containing oscillating weights or a compaction probe inserted into the ground using a top vibrator which remains at the ground surface 3.4 depth vibrator basic component of ground treatment equipment used in the installation of vibrated stone columns and in vibro compaction, which vibrates horizontally by means of an eccentric weight rotating about its longitudinal axis, and penetrates into the ground. The penetration in the ground can be made easier by air or water flushing 3.5 top vibrator vibrator which remains above the ground surface 3.6 compaction probe tool for deep vibratory compaction which is inserted into the ground to transmit vibrations from a top vibrator which remains at the ground surface; wings, drainage or water flushing can be provided to facilitate the compaction process 3.7 deep vibro compaction technique in which a depth vibrator is used to compact granular soil with or without the formation of stone columns 3.8 dry top-feed process method of installing vibrated stone columns in which the hole formed by the depth vibrator remains open and specified granular material is fed directly into the top of the hole and compacted by the vibrator in stages (the process is described in Annex B)
1) Commonly termed vibro stone columns.



EN 14731:2005 (E) 7 3.9 wet process method of installing vibrated stone columns in which flushing water removes soft material, stabilises the hole and allows specified granular material to reach the tip of the depth vibrator where it is compacted (the process is described in Annex B) 3.10 dry bottom-feed process method of installing vibrated stone columns in which specified granular material is delivered directly to the tip of the vibrator via a feed pipe attached to the vibrator, with the vibrator remaining in the ground during the construction of the column to maintain the stability of the hole (the process is described in Annex B) 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 4.1.2 The information should include: a) any legal or statutory restrictions; b) location of main grid lines or reference points for setting out; c) condition of structures, roads and services adjacent to the work; d) suitable quality management system, including supervision, monitoring and testing. 4.1.3 The information regarding the site conditions shall cover, where relevant: a) geometry of the site including boundary conditions, topography, access, slopes and headroom restrictions; b) existing underground structures, services, known contaminants and archaeological constraints; c) environmental restrictions including noise, vibration, displacements, pollution and effects of seasonal variations in weather including frozen surface layers; d) future or ongoing activities such as dewatering, tunnelling, deep excavations and raising of site levels. 4.1.4 Other information which will be required is described in Clauses 5, 6, 7 and 8. 4.2 Special features for ground treatment by deep vibration The information required in relation to the practical aspects of the execution of ground treatment shall include:  specific project design objectives which the execution of the ground treatment is intended to fulfil;  water supply and slurry disposal requirements for the wet process of installing vibrated stone columns.



EN 14731:2005 (E) 8 5 Geotechnical investigation 5.1 General 5.1.1 All site investigation shall be undertaken in accordance with EN 1997-1 and prEN 1997-2, and the design of the project. 5.1.2 The extent and depth of the site investigation shall be sufficient to determine the characteristic ground conditions and topography of the site and to identify and locate all ground formations, layers, other geological features and ground water levels affecting the execution of the works. 5.1.3 All information from site investigations shall be made available in accordance with the requirements of Clause 4. 5.1.4 Some fills may be heterogeneous and examination in trial pits may be required for a representative geotechnical description. 5.1.5 Obstructions, hard layers and cobbles and boulders within the ground which would influence or prevent the insertion of the vibrating tool should be identified. 5.1.6 The presence of ground conditions which will affect the performance of treatment shall be identified including:  hard layers;  soils sensitive to disturbance;  soils with potential for collapse settlement on wetting;  soils with liquefaction potential;  fills currently settling under self-weight. 5.1.7 Any contaminants and pollutants in the soil or the groundwater should be identified. 5.2 Specific aspects for deep vibratory compaction 5.2.1 Special consideration shall be given to the extent of the treatable granular soils and the location and extent of any layers which restrict or reduce the efficiency of the treatment process including clay, silt and organic layers and layers preventing drainage. 5.2.2 Where clay, silt or organic soils are present, some or all the properties mentioned in 5.3 may be needed. 5.2.3 The following geotechnical properties of the granular soil may be relevant to the design and execution of ground treatment by deep vibratory compaction:  particle size distribution and fines content;  in situ density index (relative density);  permeability;  crushability of particles;  inter-particle bonding caused by cementation, suction or cohesion.



EN 14731:2005 (E) 9 5.3 Specific aspects for vibrated stone columns 5.3.1 Particular attention should be given to the determination of physical and geotechnical properties required for the design and execution of the ground treatment by vibrated stone columns, for example:  compressibility;  consistency limits;  undrained shear strength;  sensitivity. 5.3.2 Certain ground conditions need particular consideration, including:  location and extent of peat and organic soil;  presence of biodegradable fill including domestic waste. 6 Materials and products 6.1 General Imported materials may be naturally occurring sands and gravels, crushed rock or recycled materials such as crushed brick or concrete. Quality control testing is described in 9.2.4. 6.2 Materials for deep vibratory compaction 6.2.1 Material may be added during deep vibratory compaction. This may be the natural granular material being compacted at the site or imported material. 6.2.2 Added materials shall be sufficiently hard and chemically inert so as to remain stable during the treatment process and subsequent working life in the anticipated soil and groundwater conditions. 6.3 Materials for vibrated stone columns Material used to form stone columns shall be:  sufficiently hard and chemically inert so as to remain stable during column construction and subsequent working life in the anticipated soil and groundwater conditions;  graded appropriately for compaction to form a dense column fully interlocked with the surrounding ground and in compliance with other requirements such as drainage;  compatible with the plant used and flow freely within bottom-feed and through-feed delivery systems without arching which may block these systems. Gradings typically used with the different processes are given in the following table. Process Grading in mm Dry top-feed process 40 to 75 Wet process 25 to 75 Dry bottom-feed process 8 to 50



EN 14731:2005 (E) 10 7 Considerations related to design 7.1 General 7.1.1 The design of ground treatment by deep vibration shall be in accordance with EN 1990, EN 1997-1and prEN 1997-2. 7.1.2 The information on ground conditions shall be assessed to determine the suitability of the ground for treatment by deep vibration. 7.1.3 The following shall be defined in the design of the ground treatment:  technical objective of the treatment (e.g. increased bearing capacity, reduced settlement; reduced liquefaction potential, reduced potential for collapse settlement on wetting or reduced permeability);  required geotechnical properties of the treated ground (e.g. shear strength, stiffness, or permeability);  criteria on which treatment depth, spacing and extent are decided;  target performance and the way in which treatment is to be assessed in terms of measurable parameters;  where excavation subsequent to treatment takes place, proposals for recompaction if necessary. 7.1.4 Due to the nature of ground, variations are to be expected even after treatment and this should be taken into consideration. 7.1.5 Heave or settlement occurring during treatment should be anticipated and allowed for in the design. Where infill is not added during deep vibratory compaction, significant surface settlement is likely and shall be estimated. 7.1.6 Proposed changes in ground level subsequent to treatment shall be assessed and the effect this may have on the treatment shall be evaluated. 7.1.7 Some deep vibration processes require large quantities of water. The effects, if any, of pumping water into the ground on the treatment volume and the surrounding ground shall be allowed for in the design. 7.1.8 The possibility of adverse effects on existing adjacent foundation systems, buildings and services, earthworks, slopes, retaining structures and buried structures, arising from ground movements, pore pressures or vibrations induced by the ground treatment shall be considered in the design. 7.1.9 In cases where adverse effects on adjacent buildings and infrastructure are of concern, a pre-condition survey should be carried out as described in 11.4. 7.1.10 Where stone columns are required to perform as drains, adequate provision should be made for surface drainage. If the existing surface soil is not adequate a surface drainage blanket should be provided. Attention should be given to the drainage properties of the working platform. 7.1.11 Where deep vibratory compaction is not intended to compact the surface layer, rollers or tampers should be used to compact this layer. Alternatively, compaction can be executed from a level above final foundation level. 7.2 Selection of treatment method 7.2.1 The selected method for executing the ground treatment shall be capable of fulfilling the design requirements. Descriptions of the treatment processes are given in Annexes A and B.



EN 14731:2005 (E) 11 7.2.2 Where previous experience of the treatment method on the type of soils prevailing at the site is limited, preliminary trials are advisable to demonstrate the feasibility of the treatment method or to optimise the design of the treatment. 7.2.3 The dry top-feed process shall only be used where the hole formed by the depth vibrator remains open. In other conditions either a dry bottom-feed process or a wet process shall be used. 7.3 Design verification 7.3.1 It is recommended that it is verified that the objectives of the treatment have been achieved. 7.3.2 Suitable means of verifying that the required treatment objectives have been achieved should be identified prior to commencement of ground treatment, in terms of the results of defined tests. 7.3.3 Appropriate methods of testing are described in 9.2. 7.3.4 The type and frequency of testing which is compatible with the requirements for quality control and performance of the treatment shall be specified. The execution and interpretation of geotechnical laboratory and field tests shall comply with the requirements of prEN 1997-2. 7.3.5 Testing, although necessary, may not be sufficient to verify the adequacy of the treatment; appropriate supervision, monitoring and records are required. An observational approach is often appropriate and design is not normally complete until site experience is gained. 7.4 Extent and layout of treatment 7.4.1 The design layout shall include the extent and location of treatment points, and the upper and lower levels of the treatment. 7.4.2 Each treatment point shall be identified by a reference number and its plan location shall be related to fixed reference points or lines. 7.4.3 Natural and artificial obstructions are commonly found and this possibility shall be considered in the design. 7.4.4 A horizontal deviation of up to 150 mm from the plan location can normally be accepted. 7.4.5 The treatment may need to extend beyond the area of the foundation of a structure to be built on the treated ground. This is the case where, for example, a primary objective of treatment is to reduce the vulnerability to liquefaction in an earthquake. 7.4.6 For foundation support, the depth of treatment shall be determined as follows:  in full-depth treatment the depth vibrator or compaction probe shall penetrate to a competent stratum identified from the site investigation;  in partial-depth treatment the depth of the treatment shall be adequate to improve the depth of ground loaded by the particular foundation system in order to fulfil the requirements for bearing capacity and total and differential settlement criteria. The potential for movement occurring below the depth of treatment shall be assessed. 7.5 Sequence of treatment The sequence in which treatment should be executed at individual treatment points and the general direction of progress across large areas should be considered at design stage with regard to the effectiveness of the treatment and the presence of adjacent, buried or overhead structures and services.



EN 14731:2005 (E) 12 8 Execution 8.1 General Work shall be carried out to written procedures. The method of treatment and equipment employed shall be suitable to achieve the depth of treatment and the design objectives in the prevailing ground conditions. Account shall be taken of concurrent site activities and all equipment movement necessary to properly carry out the ground treatment. Suitably trained and experienced personnel shall be in charge of the execution works. 8.2 Site preparation 8.2.1 The site shall be prepared in such a way that operations can be carried out safely and efficiently. Prior to commencement of ground treatment, services in the ground and overhead shall be identified and clearly marked on site or relocated. 8.2.2 Any near-surface natural or artificial obstructions shall be identified prior to the commencement of ground treatment and broken out with the resulting voids filled with specified granular material, or the layout of the treatment shall be altered to accommodate the obstructions. 8.2.3 Working platforms shall be designed, prepared and maintained in a manner suitable for the safe movement and working of the ground treatment equipment. Material used to provide working platforms shall be suitable for the ground conditions on which it is placed and shall not prevent penetration of the vibrating tool. 8.2.4 Special considerations will apply when working over water. 8.3 Setting out All treatment points shall be set out within the specified tolerances. The levels of the working platform relative to the specified upper and lower treatment levels shall be checked. 8.4 Treatment 8.4.1 General 8.4.1.1 Ground treatment shall be carried out by penetrating the ground with a vibrating tool. The appropriate method of installation shall be determined with due regard to ground and groundwater conditions in accordance with 7.2. 8.4.1.2 Pre-boring or pre-excavation may be necessary in certain circumstances. 8.4.1.3 Where unforeseen obstructions are encountered below ground level, it shall be determined whether the obstruction is to be removed, or whether the treatment points shall be relocated or adapted. Where it is decided to remove the obstruction, the void shall be backfilled with granular material suitable for compaction. 8.4.2 Deep vibratory compaction Deep compaction is achieved by penetrating the ground with a depth vibrator or with a compaction probe. Penetration and removal can be assisted by water or air. The treatment method can be used with or without the addition of granular backfill from the ground surface. Deep vibratory compaction is described in Annex A.



EN 14731:2005 (E) 13 8.4.3 Vibrated stone columns 8.4.3.1 Continuous columns shall be formed from the maximum required depth of penetration up to the upper design level as a minimum. A compacted stone column has to be built up by adding successive discrete charges of specified granular material and compacting each one to a chosen level of power consumption. 8.4.3.2 The most appropriate treatment process should be selected from the three principal methods for installing vibrated stone columns described in Annex B, namely the dry top-feed process, the wet process and the dry bottom-feed process. 8.4.3.3 Where the dry bottom-feed pro
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