Contents
Members of the Working Group for Excavations
Preface
Notes for the User
1 Introduction
1.1 Engineering prerequisites for applying the Recommendations (R l)
1.2 Governing regulations (R 76)
1.3 Safety factor approach (R 77)
1.4 Limit states (R 78)
1.5 Support of retaining walls (R 67)
1.6 Planning and examination of excavations (R 106)
2 Analysis principles
2.1 Actions (R 24)
2.2 Determination of soil properties (R 2)
2.3 Earth pressure angle (R 89)
2.4 Partial safety factors (R 79)
2.5 General requirements for adopting live loads (R 3)
2.6 Live loads from road and rail traffic (R 55).
2.7 Live loads from site traffic and site operations (R 56).
2.8 Live loads from excavators and lifting equipment (R 57)
3 Magnitude and distribution of earth pressure
3.1 Magnitude of earth pressure as a function of the selected construction method (R 8).
3.2 Magnitude of total active earth pressure lead without surcharge loads (R 4)
3.3 Distribution of active earth pressure without surcharges (R 5) .
3.4 Magnitude of total active earth pressure lead from live loads (R 6)
3.5 Distribution of active earth pressure from live loads (R 7)
3.6 Superimposing earth pressure components with surcharges (R 71)
3.7 Determination of at-rest earth pressure (R 18)
3.8 Earth pressure in retreating states (R 68)
4 General stipulations for analysis
4.1 Stability analysis (R 81)
4.2 General information on analysis methods (R 11)
4.3 Determination and analysis of embedment depth (R 80).
4.4 Determination of action effects (R 82).
4.5 Modulus of subgrade reaction method (R 102).
4.6 Finite-element method (R 103)
4.7 Analysis of the vertical component of the mobilised passive earth pressure (R 9)
4.8 Analysis of the transfer of vertical forces into the subsurface (R 84)
4.9 Stability analyses for braced excavations in special cases (R 10)
4.10 Serviceability analysis (R 83)
4.11 Allowable simplifications in limit states GEO 2 or STR (R 104).
5 Analysis approaches for soldier pile walls
5.1 Determination of load models for soldier pile walls (R 12)
5.2 Pressure diagrams for supported soldier pile walls (R 69).
5.3 Soil reactions and passive earth pressure for soldier pile walls with free earth supports (R 14)
5.4 Fixed earth support for soldier pile walls (R 25).
5.5 Equilibrium of horizontal forces for soldier pile walls (R 15)
6 Analysis approaches for sheet pile wallsand in-situ concrete walls
6.1 Determination of load models for sheet pile walls and in-situ concrete walls (R 16).
6.2 Pressure diagrams for supported sheet pile walls and in-situ concrete walls (R 70).
6.3 Ground reactions and passive earth pressure for sheet pile walls and in-situ concrete walls with free earth support (R 19).
6.4 Fixed earth support for sheet pile walls and in-situ concrete walls (R 26)
7 Anchored retaining walls
7.1 Magnitude and distribution of earth pressure for anchored retaining walls (R 42)
7.2 Analysis of force transfer from anchors to the ground (R 43)
7.3 Verification of stability at the lower failure plane (R 44).
7.4 Analysis of overall stability (R 45)
7.5 Measures to counteract deflections in anchored retaining walls (R 46)
8 Excavations with special ground plans.
8.1 Excavations with circular plan (R 73)
8.2 Excavations with oval plan (R 74)
8.3 Excavations with rectangular plan (R 75)
9 Excavations adjacent to structures
9.1 Engineering measures for excavations adjacent to structures (R 20)
9.2 Analysis of retaining walls with active earth pressure for excavations adjacent to structures (R 21)
9.3 Active earth pressure for large distances to structures (R 28)
9.4 Active earth pressure for small distances to structures (R 29)
9.5 Analysis of retaining walls with increased active earth pressure (R 22)
9.6 Analysis of retaining walls with at-rest earth pressure (R 23)
9.7 Mutual influence of opposing retaining walls for excavations adjacent to structures (R 30)
10 Excavations in water
10.1 General remarks on excavations in water (R 58).
10.2 Flow forces (R 59)
10.3 Dewatered excavations (R 60)
10.4 Analysis of hydraulic heave safety (R 61)
10.5 Analysis of buoyancy safety (R 62)
10.6 Stability analysis of retaining walls in water (R 63)
10.7 Design and construction of excavations in water (R 64)
10.8 Water management (R 65)
10.9 Monitoring excavations in water (R 66).
11 Excavations in unstable rock mass
11.1 General recommendations for excavation in unstable rock mass (R 38)
11.2 Magnitude of rock mass pressure (R 39).
11.3 Distribution of rock pressure (R 40)
11.4 Bearing capacity of rock mass for support forces at the embedment depth (R 41)
12: Excavations in soft soils
12.1 Scope of Recommendations R 91 to R 101 (R 90)
12.2 Slopes in soft soils (R 91)
12.3 Wall types in soft soils (R 92)
12.4 Construction procedure in soft soils (R 93)
12.5 Shear strength of soft soils (R 94)
12.6 Earth pressure on retaining walls in soft soils (R 95)
12.7 Ground reactions for retaining walls in soft soils (R 96)
12.8 Water pressure in soft soils (R 97)
12.9 Determination of embedment depths and action effects for excavations in soft soils (R 98)
12.10 Additional stability analyses for excavations in soft soils (R 99)
12.11 Water management for excavations in soft soils (R 100).
12.12 Serviceability of excavation structures in soft soils (R 101)
13 Analysis of the bearing capacity of structural elements
13.1 Material parameters and partial safety factors for structural element resistances (R 88).
13.2 Bearing capacity of soldier pile infilling (R 47)
13.3 Bearing capacity of soldier piles (R 48).
13.4 Bearing capacity of sheet piles (R 49)
13.5 Bearing capacity of in-situ concrete walls (R 50).
13.6 Bearing capacity of waling (R 51)
13.7 Bearing capacity of struts (R 52).
13.8 Bearing capacity of trench lining (R 53).
13.9 Bearing capacity of provisional bridges and excavation covers (R 54)
13.10 External bearing capacity of soldier piles, sheet pile walls and in-situ concrete walls (R 85).
13.11 Bearing capacity of tension piles and ground anchors (R 86)
14 Measurements and monitoring on excavation structures
14.1 Purpose of measurements and monitoring (R 31).
14.2 Measurands and measuring methods (R 32)
14.3 Measurement planning (R 33)
14.4 Location of measuring points (R 34)
14.5 Carrying out measurements and forwarding measurement results (R 35)
14.6 Evaluation and documentation of measurement results (R 36)
Annex
A 1: Relative density of cohesionless soils
A 2: Consistency of cohesive soils
A 3: Soil properties of cohesionless soils.
A 4: Soil properties of cohesive soils
A 5: Geotechnical categories of excavations
A 6: Partial safety factors for geotechnical variables
A 7: Material properties and partial safety factors for concrete and reinforced concrete structural elements.
A 8: Material properties and partial safety factors for steel structural elements
A 9: Material properties and partial safety factors for wooden structural elements.
A 10: Empirical values for skin friction and base resistance of sheet pile walls
Bibliography
Terms and notation
Recommendations in numerical order
AK 2.4 “Excavations” Working Group of the
Deutsche Gesellschaft für Geotechnik e.V. (German Geotechnical Society)
Chairman: Univ.-Prof. Dr.-Ing. habil. Achim Hettler
Geotechnical Engineering Chair
Technical University of Dortmund
August-Schmidt-Straße 8
44227 Dortmund
Germany
Translated by Geotr@ns, Alan Johnson
Cover: Excavation of the Desy XFEL Injectorcomplex executed by Züblin Spezieltiefbau GmbH (2009–2010). Source: Züblin Spezieltiefbau GmbH, Foto: Meyerfoto
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Members of the Working Group for Excavations
At the time of publication of these Recommendations the Working Group for Excavations consisted of the following members:
Univ.-Prof. Dr.-Ing. habil. A. Hettler, Dortmund (Chairman)
Dipl.-Ing. U. Barth, Mannheim
Prof. Dr.-Ing. K.-M. Borchert, Berlin
Dipl.-Ing. Th. Brand, Berlin
Dipl.-Ing. P. Gollub, Essen
Dipl.-Ing. W. Hackenbroch, Duisburg
Dipl.-Ing. R. Haussmann, Schrobenhausen
Dr.-Ing. M. Herten, Karlsruhe
Dipl.-Ing. H.-U. Kalle, Hagen
Univ.-Prof. (em.) Dr.-Ing. H. G. Kempfert, Hamburg
Dr.-Ing. St. Kinzler, Hamburg
Dr.-Ing. F. Könemann, Dortmund
Univ.-Prof. Dr.-Ing. habil. Ch. Moormann, Stuttgart
Dipl.-Ing. Ch. Sänger, Stuttgart
Dipl.-Ing. W. Vogel, Munich
Further members of the Working Group were:
o. Prof. em. Dr.-Ing. H. Breth, Darmstadt
Dipl.-Ing. R. Briske (), Horrem
Dipl.-Ing. H. Bülow, Berlin
Dipl.-Ing. G. Ehl, Essen
Dipl.-Ing. E. Erler (), Essen
Dipl.-Ing. I. Feddersen, Karlsruhe
Dipl.-Ing. H. Friesecke, Hamburg
Dipl.-Ing. F. Gantke, Dortmund
Dipl.-Ing. E. Hanke, Eckental
Dipl.-Ing. Th. Jahnke (), Cologne
o. Prof. Dr.-Ing. H. L. Jessberger (), Bochum
Dipl.-Ing. K. Kast (), Munich
Dr.-Ing. H. Krimmer, Frankfurt
o. Prof. em. Dr.-Ing. E. h. E. Lackner (), Bremen
Dr.-Ing. K. Langhagen, Dietzenbach
Dipl.-Ing. K. Martinek, Munich
Dipl.-Ing. H. Ch. Müller-Haude (), Frankfurt/Main
o. Prof. Dr.-Ing. H. Nendza (), Essen
Prof. Dr.-Ing. E. h. M. Nußbaumer, Stuttgart
Dipl.-Ing. E. Pirlet (), Cologne
Dr.-Ing. H. Schmidt-Schleicher, Bochum
Prof. Dr.-Ing. H. Schulz, Karlsruhe
Dipl.-Ing. E. Schultz, Bad Vilbel
o. Prof. Dr.-Ing. H. Simons (), Braunschweig
Dipl.-Ing. H. H. Sonder, Berlin
Dr.-Ing. J. Spang (), Munich
Dr.-Ing. D. Stroh, Essen
Prof. Dr.-Ing. K. R. Ulrichs (), Essen
Dipl.-Ing. U. Timm, Mannheim
Univ.-Prof. Dr.-Ing. B. Walz (), Wuppertal
Dipl.-Ing. K. Wedekind, Stuttgart
Prof. Dipl.-Ing. H. Wind (), Frankfurt/Main
Univ.-Prof. Dr.-Ing. habil. Dr.-Ing. E. h. A. Weißenbach, Norderstedt (Chairman until 2006)
Preface
In response to a recognisably overwhelming requirement, the Deutsche Gesellschaft für Erd- und Grundbau e.V. (German Society for Geotechnical and Ground Engineering) – now the Deutsche Gesellschaft für Geotechnik (German Geotechnical Society) – called the Working Group for Tunnel Engineering into life in 1965 and awarded chairmanship to the highly respected and now sadly missed Prof. J. Schmidbauer. The wide-ranging tasks of the Working Group were divided into three subgroups “General”, “Open Cut Methods” and “Trenchless Technology”. The “Open Cut Methods” Working Group, under the chairmanship of Prof. Dr.-Ing. habil. Dr.-Ing. E. h. Anton Weißenbach, at first busied itself only with the urgent questions of analysis, design and construction of excavation enclosures. The German Society for Geotechnical and Ground Engineering published the preliminary results of the Working Group as the “Recommendations for Calculation of Braced or Anchored Soldier Pile Walls with Free Earth Support for Excavation Structures, March 1968 Draft”.
During the course of work involving questions concerning the analysis, design and construction of excavation enclosures, it was recognised that these matters were so comprehensive that the Deutsche Gesellschaft für Erd- und Grundbau e.V. decided to remove this area from the “Tunnel Engineering” Working Group and transfer it to a separate Working Group, that of “Excavations”; the personnel involved were almost completely identical with those of the previous “Open Cut Methods” Group. The new Working Group’s first publication, with the title “Recommendations of the Working Group for Excavations”, appeared in the journal “Die Bautechnik” (Construction Technology) in 1970. It was based on a thorough revision, restructuring and enhancement of the proposals published in 1968 and consisted of 24 numbered Recommendations, primarily dealing with the basic principles of the analysis of excavation enclosures, soldier pile walls, sheet pile and in-situ concrete walls for excavations, and with the influence of buildings located adjacent to excavations.
In the years following this, the Working Group for Excavations published new and revised Recommendations at two-year intervals. As a stage was reached at which no further revisions were envisaged, the Deutsche Gesellschaft für Erdund Grundbau e.V. decided to summarise the 57 Recommendations strewn throughout the “Die Bautechnik” journal, Volumes 1970, 1972, 1974, 1976, 1978 and 1980, and to present them to the profession in a single volume.
In the 2nd edition, published in 1988, the Recommendations were partly revised and, in addition, supplemented by nine further Recommendations dealing with “Excavations in Water”, published in draft form in the 1984 volume of Bautechnik, and by two further Recommendations for “Pressure Diagrams for Braced Retaining Walls”, published in Bautechnik in 1987. Four further Recommendations resulted from partial restructuring and endeavours to make the Recommendations more clearly understandable. The revisions and supplements are described in an article in the 1989 volume of Bautechnik.
In the 3rd edition, published in 1994, a number of the Recommendations were revised and three new Recommendations on “Excavations with Special Ground Plans” added. The revisions to the existing Recommendations are described in the 1995 volume of Bautechnik. In the same issue, the three new Recommendations were also presented to the professional public in draft form. In addition, the 3rd edition includes an appendix, containing the principal from building control standard regulations, where they are relevant to stability analysis.
At the same time that the 3rd edition of the EAB was being compiled, the Working Group for Excavations was deeply occupied with the implementation of the new partial safety factor approach in geotechnical and ground engineering. This was because, on the one hand, several members of the Working Group for Excavations were also represented in the “Safety in Geotechnical and Ground Engineering” Committee, which was compiling DIN V 1054–100. On the other hand, it became increasingly obvious that excavation structures were affected by the new regulations to a far greater degree than other ground engineering structures. In particular the specification in the new draft European regulations EN 1997-1 – applying partial safety factors to the shear strength on the one hand and to the actions on the other – was unacceptable. Compared to previously tried and tested practice it led to results that, in places, suggested considerably greater dimensions, but also to results that were not conservative enough. In contrast to this stood the draft DIN 1054 counter-model, in which the partial safety factors identified using the classical shear strength method were applied in the same manner to the external actions, earth pressure and soil resistances. In EAB-100, published in 1996 at the same time as the ENV 1997-1 and DIN 1054-100, the practical applications of both concepts were introduced and the differences illuminated. This was intended to make the decision in favour of the German proposals, which was still open, more straightforward for the profession.
Two important decisions were subsequently made: on the one hand, EN 1997-1 was published in a format that included the proposals of the new DIN 1054 as one of three allowable alternatives. On the other hand DIN 1054-100 was modified such that the originally envisaged superpositioning of earth pressure and passive earth pressure design values was no longer permissible, because this route could not be reconciled with the principle of strict separation of actions and resistances. In addition, one now has characteristic action effects and characteristic deformations when adopting characteristic actions for the given system, with the result that generally only one analysis is required for verification of both bearing capacity and serviceability. The 4th (German) edition of the EAB, published in 2009, rested entirely upon these points, but also expanded them by supplementary regulations, just as it has in the past. Moreover, all the Recommendations of the 3rd edition have been thoroughly revised. Recommendations on the use of the modulus of subgrade reaction method and the finite element method (FEM), as well as a new chapter on excavations in soft soils, have been added. These had previously been presented to the profession for comments in the 2002 and 2003 volumes of the Bautechnik journal, based on the global safety factor approach. Much correspondence, some very extensive, has been taken into consideration in the 4th edition.
Once the 4th edition was complete in 2006, Anton Weißenbach stepped down from his position as chairman after more than 40 years and retired from the working group along with a number of other long-term members.
Following this, one of the main emphases of the Working Group on Excavations – now under the Chairmanship of the undersigned – was Recommendation R 102 “Modulus of subgrade reaction method”, presented in draft to the professional community, completely revised, in 2011 in the journal Bautechnik. In line with the imminent introduction of the Eurocodes as binding building regulations it became necessary to adapt the 4th edition of the Recommendations to the provisions of DIN EN 1997-1:2009, in conjunction with National Annex DIN 1997-1/NA:2010-12 and the supplementary regulations of DIN 1054:2010-12. All Recommendations were thoroughly examined, revised where necessary and adapted to accommodate recent developments. The experienced user will note that the revisions to this 5th edition are relatively minor. It was possible to retain the majority of the tried and tested regulations, because the safety philosophy has not altered in principle compared to the 4th edition.
Section 10, “Excavations in water”, on the other hand, has been substantially revised. In future, the planner must examine risks arising from erosion processes, anisotropic permeability and hydraulic failure more extensively than was previously required. As a result of sophisticated developments in monitoring technology and increased demands, Section 14, “Measurements on excavations”, has been completely reformulated.
By revising existing Recommendations and publishing new ones, the Working Group for Excavations aims to:
a) Simplify the analysis of excavation enclosures;
b) Unify load approaches and analysis methods;
c) Guarantee the stability of the excavation structure and its individual components and;
d) Improve the economic efficiency of excavation structures.
The Working Group for Excavations would like to express thanks to all who have supported the work of the Working Group in the past, in correspondence or by other means, and requests your further support for the future.
A. Hettler
Notes for the User
1. The Recommendations of the Working Group for Excavations represent technical regulations. They are the result of voluntary efforts within the technical-scientific community, are based on valid and current professional principles, and have been tried and tested as general best practice.
2. The Recommendations of the Working Group for Excavations may be freely applied by anyone. They represent a yardstick for flawless technical performance; this yardstick is also of legal relevance. A duty to apply the Recommendations may result from legislative or administrative provisions, contractual obligations or other legal requirements.
3. Generally speaking, the Recommendations of the Working Group for Excavations are an important source of information for professional conduct in normal design cases. They cannot reproduce all possible special cases in which more advanced or more restrictive measures may be required. Note also that they can only reflect best practice at the time of publication of the respective edition.
4. Deviations from the suggested analysis approaches may prove necessary in individual cases, if founded on appropriate analyses, measurements or empirical values.
5. Use of the Recommendations of the Working Group for Excavations does not release anybody from their own professional responsibility. In this respect, everybody works at their own risk.
1
Introduction
1.1 Engineering prerequisites for applying the Recommendations (R l)
If no other stipulations are explicitly made in the individual Recommendations, they shall apply under the following engineering preconditions:
1. The complete height of the retaining wall is lined.
2. The soldier piles of soldier pile walls are installed such that intimate contact with the ground is ensured. The lining or infilling can consist of wood, concrete, steel, hardened cement-bentonite suspension or stabilised soil. It shall be installed such that the contact with the soil is as uniform as possible. Soil excavation should not advance considerably faster than plank installation. Also see DIN 4124.
3. Sheet pile walls and trench sheet piles are installed such that intimate contact with the ground is ensured. Toe reinforcement is permitted.
4. In-situ concrete walls are executed as diaphragm walls or as bored pile walls. Accidental or planned spacing between the piles is generally lined according to Paragraph 2.
5. In the horizontal projection, struts or anchors are arranged perpendicular to the retaining wall. They are wedged or prestressed such that contact by traction with the retaining wall is guaranteed.
6. Braced excavations are lined in the same manner on both sides with vertical soldier pile walls, sheet pile walls or in-situ concrete walls. The struts are arranged horizontally. The ground on both sides of the braced excavation displays approximately the same height, similar surface features and similar subsurface properties.
If these preconditions are not fulfilled, or those in the individual Recommendations, and no Recommendations are available for such special cases, this does not exclude application of the remaining Recommendations. However, the consequences of any deviations shall be investigated and taken into consideration.
1.2 Governing regulations (R 76)
1. Following its introduction, geotechnical analysis and design in Germany are controlled by DIN EN 1997-1: Eurocode 7: Geotechnical Design – Part 1: General Rules (Eurocode 7), in conjunction with the corresponding National Annex:
– DIN EN 1997-1/NA: National Annex – Nationally Determined Parameters – Eurocode 7: Geotechnical design – Part 1: General rules and
– DIN 1054: Subsoil – Verification of the Safety of Earthworks and Foundations – Supplementary Rules to DIN EN 1997-1.
These three coordinated standards are summarised in the ‘Handbuch Eurocode 7, Band 1’.
The National Annex represents a formal link between the Eurocode EC 7-1 and national standards. It states which of the possible analysis methods and partial safety factors are applicable in the respective national domains. Remarks, clarifications or supplements to Eurocode EC 7-1 are not permitted. However, the applicable, complementary national codes may be given. The complementary national codes may not contradict Eurocode EC 7-1. Moreover, the National Annex may not repeat information already given in Eurocode EC 7-1.
2. In addition, the following Eurocode programme standards govern excavation structures:
EN 1990 Eurocode 0:Basis of structural designEN 1991 Eurocode 1:Actions on structuresEN 1992 Eurocode 2:Design of concrete structuresEN 1993 Eurocode 3:Design of steel structuresEN 1995 Eurocode 5:Design of timber structuresEN 1998 Eurocode 8:Design of structures for earthquake resistance
3. The Eurocode 7 Handbook, Volume 1 contains general rules for geotechnical engineering. It is supplemented by the analysis standards which, where necessary, have been adapted to the partial safety factor approach. The following codes in particular also represent the governing standards for excavation structures:
DIN 4084:Global stability analysesDIN 4085:Subsoil – Calculation of earth pressureDIN 4126:Cast-in-situ concrete diaphragm walls; design and constructionDIN 4093:Design of ground improvement – Jet grouting, deep mixing or grouting
4. The standards covering ground exploration, investigation and description are not affected by the adaptation to partial safety factors and therefore remain valid in their respective latest editions, or are superseded by Eurocode 7 and EN ISO standards:
EN 1997-2, Eurocode 7: Geotechnical design – Part 2: Ground investigation and testing
EN 1997-2/NA: National Annex – Nationally Determined Parameters – Eurocode 7, Part 2: Ground investigation and testing
DIN 4020: Geotechnical investigations for civil engineering purposes – Supplementary rules to DIN EN 1997-2
DIN 4023: Geotechnical investigation and testing – Graphical presentation of logs of boreholes, trial pits, shafts and adits
EN ISO 22475-1: Geotechnical investigation and testing – Sampling by drilling and excavation and groundwater measurements – Part 1: Technical principles for execution, supersedes DIN 4021 and DIN 4022
EN ISO 14688-1: Geotechnical Investigation and testing – Identification and classification of soil – Part 1: Identification and description, superseded by DIN 4022-1
EN ISO 14688-2: Geotechnical Investigation and testing – Identification and classification of soil – Part 2: Principles for classification, superseded by DIN 4022-1
EN ISO 14689-1: Geotechnical Investigation and testing – Identification and classification of rock – Part 1: Identification and description, superseded by DIN 4022-1
EN ISO 22476-2: Dynamic probing
EN ISO 22476-3: Standard Penetration Test
DIN 4094-2: Subsoil – Field testing – Part 2: Borehole dynamic probing
DIN 18121 to DIN 18137: Investigation of soil samples
DIN 18196: Soil classification for civil engineering purposes
DIN 1055-2: Soil properties
5. The Eurocode 7 Handbook, Volume 1, only replaces the analysis section of the previous standards DIN 4014 “Bored piles”, DIN 4026 “Driven piles”, DIN 4125 “Ground anchorages – Design, construction and testing” and DIN 4128 “Grouted piles (in-situ concrete and composite piles) with small diameter”. The new European standards from the “Execution of special geotechnical works” series now take the place of the execution sections of these standards:
EN 1536:Bored pilesEN 1537:Grouted anchorsEN 1538:Diaphragm wallsEN 12063:Sheet pile wallsEN 12699:Displacement pilesEN 12715:GroutingEN 12716:Jet groutingEN 12794:Precast concrete – foundation pilesEN 14199:Micropiles
6. The following execution standards are not affected by the adaptation to European standards and therefore continue to govern excavation structures:
DIN 4095:Drainage systems protecting structuresDIN 4123:Excavations, foundations and underpinnings in the area of existing buildingsDIN 4124:Excavations and trenches
1.3 Safety factor approach (R 77)
1. In contrast to the original probabilistic safety factor approach, this safety factor approach, upon which both the new European standards generation and the new national standards generation are based, no longer rests on probability theory investigations, e.g. the beta-method, but on a pragmatic splitting of the previously utilised global safety factors into partial safety factors for actions or effects and partial safety factors for resistances.
2. The foundation for stability analyses is represented by the characteristic or representative values for actions and resistances. The characteristic value is a value with an assumed probability which is not exceeded or fallen short of during the reference period, taking the lifetime or the corresponding design situation of the civil engineering structure into consideration; it is characterised by the index “k”. Characteristic values are generally specified based on testing, measurements, analyses or empiricism.
Variable actions can also be given as representative values, thus taking into consideration that not all variable, unfavourable actions occur simultaneously at their maximum values.
3. If the bearing capacity in a given cross-section of the retaining wall or in an interface between the retaining wall and the subsoil needs to be analysed, the effects in these sections are required:
– as action effects, e.g. axial force, shear force, bending moment;
– as stresses, e.g. compression, tension, bending stress, shear stress or equivalent stress.
In addition, further effects of actions may occur:
– as oscillation effects or vibrations;
– as changes to the structural element, e.g. strain, deformation or crack width;
– as changes in the position of the retaining wall, e.g. displacement, settlement, rotation.
4. Two types of ground resistances are differentiated:
a) The characteristic shear strength of the soil is the decisive basic resistance parameter. For consolidated soils or soils drained for testing these are the shear parameters and and for unconsolidated soils or soils not drained for testing the shear parameters and . These variables are defined as cautious estimates of the mean values, because the shear strength at a single point of the slip surface is not the decisive value but the average shear strength in the slip surface.
b) The soil resistances are derived from the shear strength, directly:
– the sliding resistance;
– the bearing capacity;
– the passive earth pressure;
and indirectly via load tests or empirical values:
– the toe resistance of soldier piles, sheet pile walls and in-situ concrete walls;
– the skin resistance of soldier piles, sheet piles walls, in-situ concrete walls, and of ground anchors and soil and rock nails.
The term “resistance” is only used for the failure state of the soil. As long as the failure state of the soil is not achieved by effects, the term “soil reaction” is used.
5. The cross-section and internal resistance of the material are the decisive factors in the design of individual components. The detailed specification standards continue to be the governing standards here.
6. The characteristic values of the effects are multiplied by partial safety factors, those of the resistances are divided. Where necessary, representative values should be adopted by applying combination factors. The variables acquired in this way are known as the design values of effects or resistances respectively and are characterised by the index d. Five limit states are differentiated for stability analyses, in line with R 78 (Section 1.4).
7. In terms of the GEO 2 and STR limit state safety analyses according to R 78, Paragraph 4 (Section 1.4), Eurocode EC 7-1 provides three options. DIN 1054 is based on design approach 2 inasmuch as the partial safety factors are applied to the effects and to the resistances. To differentiate between this and the other permitted scenario, in which the partial safety factors are not applied to the effects but to the actions, this procedure is designated as design approach 2* in the Commentary to Eurocode EC 7-1 [134].
8. In addition to the actions, the design situation shall be taken into consideration in the analyses. To this end the existing load cases LC 1, LC 2 and LC 3, adopted for use in analyses to DIN 1054:2005-01, have been superseded by the design situations for use in analyses to the Eurocode 7 Handbook, Volume 1, and DIN EN 1990 as follows:
DS-P (persistent situation);
DS-T (transient situation) and;
DS-A (accidental situation).
The former LC 2/3 corresponds to design situation DS-T/A. In addition, there is the seismic design situation, DS-E. More detailed information can be found in the Eurocode 7 Handbook, Volume 1.
1.4 Limit states (R 78)
1. The term “limit state” is used with two different meanings:
a) In soil mechanics, the state of the soil in which the displacement of the individual soil particles against each other is so great that the mobilisable shear strength achieves its greatest values in either the entire soil mass, or at least in the region of a failure plane, is known as the limit state of plastic flow. It cannot become greater even if more movement occurs, but may become smaller. The limit state of plastic flow characterises the active earth pressure, passive earth pressure, bearing capacity, slope stability and overall stability.
b) A limit state in the sense of the new safety factor approach is a state of the load-bearing structure where, if exceeded, the design requirements are no longer fulfilled.
2. The following limit states are differentiated in conjunction with the partial safety factor approach:
a) The ultimate limit state is a condition of the structure which, if exceeded, immediately leads to a mathematical collapse or other form of failure. In the Eurocode 7 Handbook, Volume 1, it is referred to as ULS (ultimate limit state). Five cases of ULS are differentiated, see Paragraphs 3, 4 and 5.
b) The serviceability limit state (SLS) is a condition of the structure which, if exceeded, no longer fulfils the conditions specified for its use. In the Eurocode 7 Handbook, Volume 1, it is referred to as SLS (serviceability limit state).
3. Eurocode 7 defines the following limit states:
a) EQU: loss of equilibrium of the structure, regarded as rigid, without the influence of soil resistances.
b) STR: inner failure or very large deformation of the structure or its components, whereby the strength of the materials is decisive for resistance.
c) GEO: failure or very large deformation of the subsoil, whereby the strength of the soil or rock is decisive for resistance.
d) UPL: loss of equilibrium of the structure or ground due to uplift or water pressure.
e) HYD: hydraulic failure, inner erosion or piping in the ground, caused by a hydraulic gradient.
4. In order to transfer it to the provisions of DIN 1054 the GEO limit state shall be divided into GEO 2 and GEO 3 limit states:
a) GEO 2: failure or very large deformation of the subsoil in conjunction with identification of the action effects and dimensions; i.e. when utilising the shear strength for passive earth pressure, sliding resistance and bearing resistance and when analysing lower failure plane.
b) GEO 3: failure or very large deformation of the ground in conjunction with analysis of overall stability, i.e. when utilising the shear strength for analysis of the safety against slope failure and global failure and, generally, when analysing the stability of engineered slope stabilisation measures.
5. The previous limit states are replaced as follows:
a) The previous limit state GZ 1A now corresponds without restrictions to the EQU, UPL and HYD limit states.
b) The previous limit state GZ 1B corresponds without restrictions to the STR limit state. In addition, the GEO 2 limit state applies in conjunction with external design, i.e. when utilising the shear strength for passive earth pressure, sliding resistance and bearing capacity and when analysing lower failure plane.
c) The previous GZ 1C limit state corresponds to the GEO 3 limit state, in conjunction with analysis of overall stability, i.e. when utilising the shear strength for analysis of safety against slope failure and overall stability.
Analysis of the stability of engineered slope stabilisation measures is always allocated to the GEO limit state. Depending on the specific design and function they may be dealt with:
– either in the sense of the previous limit state GZ 1B adopting the provisions of the GEO B limit state;
– or in the sense of the previous limit state GZ 1C adopting the provisions of the GEO C limit state.
6. The EQU, UPL and HYD limit states describe the loss of static equilibrium:
– analysis of safety against overturning EQU;
– analysis of safety against uplift UPL;
– analysis of hydraulic heave safety HYD.
Only actions are associated with these limit states, no resistances. The governing limit state condition is:
i.e. the destabilising action Fk, multiplied by the partial safety factor , may only be as large as the stabilising action Gk, multiplied by the partial safety factor .
7. The STR and GEO 2 limit states describe the failure of structures and structural elements or the failure of the ground. They include:
– analysis of the bearing capacity of structures and structural elements subjected to soil loads or supported by the soil;
– verification that the bearing capacity of the soil is not exceeded, e.g. by passive earth pressure, bearing capacity or sliding resistance.
Verification that the bearing capacity of the ground is not exceeded is performed exactly as for any other construction material. The limit state condition is always the governing condition:
i.e. the characteristic action effect Ek, multiplied by the partial safety factor γF for actions or γE for effects, may only become as large as the characteristic resistance Rk, divided by the partial safety factor γR.
8. The GEO 3 limit state is peculiar to geotechnical and ground engineering. It describes the loss of overall stability. They include:
– analysis of safety against slope failure;
– analysis of safety against global failure of retaining structures.
The limit state condition is always the governing condition:
i.e. the design value Ed of the effects may only become as large as the design value of the resistances Rd. The geotechnical actions and resistances are determined using the design values for shear strength:
i.e. the tangent of the angle of internal friction and the cohesion c are reduced by applying the partial safety factors and .
9. The serviceability limit state describes the state of a structure at which the conditions specified for its use are no longer fulfilled, without a loss of bearing capacity. It is based on verification that the anticipated displacements and deformations are compatible with the purpose of the structure. For excavations, the SLS includes the serviceability of neighbouring buildings or structures.
1.5 Support of retaining walls (R 67)
1. Retaining walls are called unsupported if they are neither braced nor anchored and their stability is based solely on their restraint in the ground.
2. Retaining walls are called yieldingly supported if the wall support points can yield with increasing load, e.g. in cases where the supports are heavily inclined toward the excavation base and when using non-prestressed or only slightly prestressed anchors.
3. Retaining wall supports are called slightly yielding in the following cases:
a) Struts are at least tightly connected by frictional contact (e.g. by wedges).
b) Grouted anchors are prestressed and locked off to at least 80 % of the computed characteristic effect required for the next construction stage, see Section 7.
c) A tight connection via frictional contact is established with piles, which verifiably display only a small head deflection under load.
4. Retaining wall supports are known as nearly inflexible if designed according to R 22, Paragraph 1 (Section 9.5), utilising increased active earth pressure, and the struts and anchors are prestressed and locked off according to R 22, Paragraph 10.
5. Retaining wall supports are defined as inflexible only if they are designed either for reduced or for the full at-rest earth pressure according to R 23 (Section 9.6) and the supports are prestressed accordingly. Furthermore, the anchors of anchored retaining walls shall be socketed in non-yielding rock strata or be designed substantially longer than required by calculations.
If the requirements of Paragraphs 4 or 5 are fulfilled and, in addition:
– a rigid retaining wall is installed and;
– excessive toe deflections are avoided;
an excavation structure may be regarded as a low-deflection and low-deformation structure.
1.6 Planning and examination of excavations (R 106)
1. If the planner is not in possession of sufficient expertise and experience, a suitable planner shall be contracted for the geotechnical design of the excavation in line with the Eurocode 7 Handbook, Volume 1, Paragraph 1.3, A 3.
2. The term “geotechnical expert” used in the Recommendations is understood as it is used in the Eurocode 7 Handbook, Volume 2, Paragraph A 2.2.2.
3. Excavations are classified as Geotechnical Category GC 1, GC 2 or GC 3. Annex A5 lists criteria for classifying excavations based on the Eurocode 7 Handbook, Volume 1, Paragraph A 2.1.2.
4. A Geotechnical Design Report in line with the Eurocode 7 Handbook, Volume 1, Paragraph 2.8 shall be compiled for excavations.
With regard to Geotechnical Categories GC 2 and GC 3, the Geotechnical Design Report for the excavation should contain the following points:
– Description of the plot and its environs, in particular adjacent buildings;
– Description of ground conditions with reference to the Geotechnical Report in accordance with the Eurocode Handbook, Volume 2, Paragraph A 7;
– Description of the proposed excavation structure;
– Description of the actions from adjacent structures;
– Description of the impacts on adjacent areas and structures;
– Characteristic values of soil and rock properties, and of water levels and flows;
– Proposal for excavation structure and identification os possible risks;
– Design situation and partial factors;
– Where necessary, an explanation of the necessity, suitability and sufficiency of the observational method;
– Analyses, including information on the analysis method and plans;
– Specifications for manufacturing controls, e.g. load tests;
– Specifications for measurements and monitoring.
5. Where excavations are classified as Geotechnical Category GC 3 a geotechnical expert shall be consulted.
6. When executing excavations classified as Geotechnical Category GC 2 or GC 3, it is recommended to employ a suitable site supervisor in possession of the appropriate experience and excavation knowledge. For excavations classified as Geotechnical Category GC 3 it is recommended to also employ the geotechnical expert discussed in Section 5 to check the detailed design and to assess the results of measurements and monitoring.
2
Analysis principles
2.1 Actions (R 24)
1. DIN EN 1990, including DIN EN 1990/NA and DIN 1054, differentiates between permanent and variable actions. In excavation structures the permanent actions include:
– self-weight of the excavation structure, if necessary taking provisional bridges and excavation covers into consideration;
– earth pressure as a result of the self-weight of the soil, if necessary taking cohesion into consideration;
– earth pressure as a result of the self-weight of adjacent structures;
– horizontal shear forces created by vaults, and shear forces from retaining walls and frame-like structures;
– water pressure as a result of the contractually agreed upon reference water level of groundwater or open water.
The Eurocode 7 Handbook, Volume 1, Section 9.5.1, A(10), states that, in simplification, the earth pressure resulting from a variable, unbounded distributed load is adopted as a permanent action. Also see Paragraph 2.
2. According to Recommendations R 55 to R 57 (Sections 2.6 to 2.8), the variable actions are differentiated into a component adopted as an unbounded distributed load and a component adopted either as a distributed load qk in excess of this or as a strip load, line load or point load on a small contact area. While the unbounded distributed load according to Paragraph 1 is treated as a permanent load, the other variable actions are differentiated for the cases described below as a function of the duration and frequency of the action based on DIN 1054.
3. Beside the permanent actions it is generally sufficient to base the stability analysis on the following, regularly occurring variable actions:
– live loads acting directly on provisional bridges and excavation covers according to R 3, Paragraph 1 (Section 2.5);
– earth pressure from live loads according to R 3, Paragraph 1 (Section 2.5);
– earth pressure from live loads in conjunction with structures adjacent to the excavation.
4. In special cases it may be necessary to consider the following actions, beside the typical case loads:
– centrifugal, brake and nosing forces, e.g. for excavations adjacent to or below railway or tram lines;
– exceptional loads and improbable or rarely occurring combinations of loads or points of application of loads;
– water pressure resulting from water levels that may exceed the agreed design water levels, e.g. water levels that will flood the excavation if they occur or at which the excavation shall be intentionally flooded;
– the impact of temperature on struts.
The impact of temperature changes on the remaining excavation structure need not be investigated for flexible walls.
5. In unusual cases it may be necessary to consider exceptional loads, beside the loads of the typical case, e.g.:
– impact of construction machinery against the supports of provisional bridges or excavation covers or against the intermediate supports of buckling protection devices;
– loads caused by the failure of operating or stabilising installations, if the effects cannot be countered by appropriate measures;
– loads caused by the failure of particularly susceptible bearing members, e.g. struts or anchors;
– loads resulting from scour in front of the retaining wall.
Short-term exceptional loads, e.g. such as those occurring when testing, overstressing, or loosening anchors or struts, may be treated as exceptional loads.
6. The actions specified in Paragraphs 3 to 5 are allocated to design situations corresponding to the different safety requirements. Also see R 79 (Section 2.4).
7. When determining representative values the following combination factors may be adopted to determine loads:
– For excavations adjacent to old buildings is adopted for the foundation loads. For new builds the representative values given in the structural engineer’s analysis are adopted.
– If the vertical loads resulting from road and rail traffic corresponding to R 55, Section 2.6 are adopted, combination factors are applied. However, it is also possible to adopt different values if the analyses are based on regulations issued by the respective transport authorities.
– In general, when using simplified load assumptions in accordance with R 56, Section 2.7 for live loads from site traffic and site operations, and in accordance with R 57, Section 2.8 for live loads from excavators and lifting equipment, the combination factors are adopted at .
2.2 Determination of soil properties (R 2)
1. In principle, the soil properties required for stability analyses are specified as the immediate result of geotechnical investigations based on DIN EN 1997-2, including DIN EN 1997-2/NA and DIN 4020 “Geotechnical Investigations for Civil Engineering Purposes”. To take the heterogeneity of the subsurface and the inaccuracy of sampling and testing into due consideration, surcharges and allowances shall be applied to the values identified during testing before they are adopted as characteristic values in an analysis. This applies particularly to shear strength. Also see Paragraph 3.
2. Two cases are differentiated when specifying characteristic values for the unit weight:
a) For stability analyses in the GEO 2, STR and GEO 3 limit states, i.e. in particular when analysing the embedment depth, when determining the action effects and when analysing the safety against global failure, the mean value may be adopted as the characteristic value.
b) When analysing safety against uplift UPL, safety against hydraulic failure HYD and safety against heave EQU, the lower characteristic values are the governing values.
3. Characteristic values for shear strength should be selected as conservative estimates of the statistical mean value. Minor deviations from the mean value may be acceptable if the available samples are sufficiently representative of the soil in the region of the excavation structure being analysed. A larger deviation shall be assumed for a small data pool and heterogeneous subsoil.
4. The capillary cohesion of cohesionless soil, in particular of sand, may be taken into consideration if it cannot be lost by drying or flooding or due to rising groundwater or water ingress from above during construction work.
5. The cohesion of a cohesive soil may only be considered if the soil does not become pulpy when kneaded and if it is certain that the soil state will not change unfavourably compared to its original condition, e.g. when thawing following a period of frost.
6. The following restrictions shall be considered when transferring the shear strength determined by testing laboratory samples to the behaviour of the in-situ ground:
a) The shear strength of cohesive and rock-like soils can be greatly reduced by hair cracks, slickensides and cracks or intercalations of slightly cohesive or cohesionless soils.
b) Certain slip surfaces may be predetermined by faulting and inclined bedding planes. For example, Opalinus Clay (Opalinuston, a Middle-Jurassic (Dogger alpha, Aalenium) clay (Al (1) Clay)), Nodular Marl (Knollenmergel, a marly claystone containing carbonate nodules; Upper Triassic, Carvian) and Tarras (a type of Puzzolan) are all considered especially prone to sliding.
c) In fine-grained soils, e.g. kaolin clay, and in soils with a governing proportion of montmorillonite, the residual shear strength may be the governing factor.
7. If the results of appropriate soil mechanics laboratory tests are not available, the characteristic soil properties may be specified as follows:
a) As far as it is sufficiently known from local experience that similar subsurface conditions are prevalent, the soil properties identified from previous investigations carried out in the immediate vicinity may be adopted. This requires expertise and experience in the geotechnical field.
b) If the type and quality of in-situ soils can be assigned to the soil groups specified in DIN 18196 based on drilling or soundings, and further laboratory and manual testing, analysis may be based on the soil properties given in Appendices A 3 and A 4, taking the respective restrictions into consideration.
8. The empirical values for cohesionless soils given in:
– Table 3.1 for the unit weight based on Appendix A 3 or;
– Table 3.2 for the shear strength based on Appendix A 3;
may be adopted, if the following requirements are met:
a) It shall be possible to allocate the soils to the tables in terms of grain size distribution, uniformity coefficient and relative density. See Appendix A 1 for classification of soils in terms of relative density.
b) The given empirical values apply to both natural ground and made, cohesionless soils. The density of the soil may be improved in both cases by compaction.
The table values may not be applied to soils with porous grains, such as pumice gravel and tuff sand.
9. The empirical values for cohesive soils given in:
– Table 4.1 for the unit weight based on Appendix A 4 or;
– Table 4.2 for the shear strength based on Appendix A 4;
may be adopted if the soils can be allocated to the soil groups according to DIN 18 196 in terms of their plasticity and can be differentiated in terms of their consistency. See Appendix A 2 for classification in terms of consistency.
The table values may not be adopted in any of the following cases:
a) They may not be adopted for mixed-grain soils where the type of fines on the one hand and the proportion of grain > 0.4 mm on the other do not allow the degree of plasticity to be reliably described, e.g. for sandy boulder clay.
b) They may not be adopted for the soils described in Paragraph 6.
c) They may not be adopted if a sudden collapse of the grain skeleton is possible, e.g. in loess (aeolian silt deposit).
2.3 Earth pressure angle (R 89)
1. The angles and between the direction of acting of the earth pressure or the passive earth pressure and the normal on the rear face of the wall depend on:
– the characteristic wall friction angle
– the relative movement between wall and soil;
– the selection of slip surface type;
– the degree of mobilisation.
2. The characteristic wall friction angle is a measure of the largest possible physical friction between the wall and the ground. It is primarily dependent on the:
– shear strength of the soil and;
– surface roughness of the wall.
3. The following cases are differentiated in terms of the roughness of the wall:
a) A rear wall face is known as “toothed” if, due to its shape, it displays such a convolute surface that the wall friction acting immediately between the wall and the ground is not decisive, but instead the friction in a planar failure surface in the ground, which only partly contacts the wall. This is always the case in pile walls. Even cut-off walls manufactured using a hardening cement-bentonite slurry with inserted sheet pile walls or soldier piles may be classified as toothed [123]. This also applies approximately for driven, vibrated or pressed sheet pile walls.
b) The untreated surfaces of steel, concrete and wood can generally be considered as “rough”, in particular the surfaces of soldier piles and infill walls.
c) The surface of a diaphragm wall may be classified as “slightly rough” if filter cake development is low, e.g. for diaphragm walls in cohesive soils. Empiricism indicates that this is also the case for diaphragm walls in cohesionless soils. However, if the formation of a filter cake during diaphragm wall construction can be avoided using suitable measures, or a heavily uneven wall surface is achieved, a higher absolute earth pressure angle than may be adopted [148, 149]. d) All rear wall faces should be classified as “smooth” if the ground displays “smeary” properties due to its clay content and consistency.
4. Only if:
– earth pressure or passive earth pressure calculations are based on a curved or a non-circular slip surface and;
– it can be demonstrated according to R 9, Paragraph 1 (Section 4.8) that the sum of the characteristic actions directed downwards is at least as large as the upwards directed vertical component of the characteristic support force
may the physically possible wall friction be considered according to Paragraph 5 a).
If approximately planar slip surfaces are used, the earth pressure angle according to Paragraph 5 b) shall be reduced to compensate for the error occurring due to overestimation of the passive earth pressure coefficient or underestimation of the earth pressure coefficient
5. The following wall friction angles and maximum earth pressure angles shall be adopted as a function of the friction angle
Wall textureCurved slip surfacesPlanar slip surfacesToothed wallRough wallSlightly rough wallSmooth wall
a) The values in the middle column are wall friction angles, which may be adopted for curved or non-circular slip surfaces as the maximum angle of inclination for the active and the passive earth pressure.
b) The figures in the right column serve to compensate for the modelling error when planar slip surfaces are used. Planar slip surfaces may be adopted for active earth pressure regardless of the friction angle for passive earth pressure only for
c) If, during analysis of the vertical component of the mobilised passive earth pressure, correction of the earth pressure angle to R 9, Paragraph 2 d) (Section 4.7) is dispensed with, determination of passive earth pressure may only be based on curved slip surfaces.
6. The sign of the earth pressure angle is dependent on the relative displacement between the wall and the ground:
a) For active earth pressure the earth pressure angle is positive if the earth wedge moves downwards more than the wall as shown in Figure R 89-1 a).
Figure R 89-1. Angle for active earth pressure
b) For active earth pressure the earth pressure angle is negative if the wall moves downwards more than the ground as shown in Figure R 89-1 b).
The same applies in principle for determination of the passive earth pressure. Also see Figure R 19-1 (Section 6.3).
2.4 Partial safety factors (R 79)
1. In principle, the value of the partial safety factor depends on the design situations, as specified in DIN EN 1990, including DIN EN 1990/NA and DIN 1054. Excavation structures are included in design situation DS-T (transient situation), in conjunction with the loads for the accidental situation in the design situation DS-A. Based on this the actions in accordance with R 24 (Section 2.1) are allocated as follows:
a) The standard case according to R 24, Paragraph 3 corresponds to the design situation DS-T.
b) The special case according to R 24, Paragraph 4 corresponds to the design situation DS-T/A.
a) The exceptional case according to R 24, Paragraph 5 corresponds to the design situation DS-A.
2. The partial safety factors for actions for design situations DS-T and DS-A are based on DIN 1054. The partial safety factors for actions for the intermediate design situations DS-T/A are interpolated. This provides the partial safety factors for actions according to Table 6.1 in Appendix A 6.
3. Favourable variable actions may not be adopted for either of the limit states ULS or SLS.
4. In the serviceability limit state (SLS) the partial safety factors for permanent actions and for variable actions are adopted. See R 83 for further details (Section 4.11).
5. The partial safety factors according to DIN 1054 for geotechnical resistances are summarised in Appendix A 6:
– in Table 6.2 for resistances in the GEO 2 limit states;
– in Table 6.3 for resistances in the GEO 3 limit state.
The partial safety factors for the design situations DS-T/A are interpolated between those of design situations DS-T and DS-A, similar to those of the actions.
6. The numerical values for design situation DS-P in Appendix A 6 have been adopted as orientation values, but are placed in brackets because they generally do not govern excavation structures. Exceptions include:
– analysis of deep-seated stability according to R 44, Paragraph 10 (Section 7.3), in excavations adjacent to structures;
– analysis of global stability according to R 45, Paragraph 7 (Section 7.4), in excavations adjacent to structures;
– design of struts according to R 52, Paragraph 14 (Section 13.7);
– design of anchorages for walls in the fully excavated state.
2.5 General requirements for adopting live loads (R 3)
1. The following variable actions are described as live loads:
– loads from road and rail traffic according to R 55 (Section 2.6);
– loads from site traffic and site operations according to R 56 (Section 2.7);
– loads from excavators and lifting equipment according to R 57 (Section 2.8).
See R 24 (Section 2.1) for classification of these loads into standard and exceptional loads.
