Bnc

Multiply variable actions yq Yg 1.11 by ratio Yq Yg 3. Perform soil structure interaction analysis 4. Check ratio of restoring yg x YRe 1.35 to overturning moment Mr Mo Yg x YRe 5. Apply partial factor to action effects tPartial factors from Set A2 for geotechnical actions First, variable actions are 'pre-factored' by the ratio yq yG > 1 so that subsequent parts of the calculation can treat them as permanent actions. Second, soil strengths are factored down by ym 1. The resulting design...

Actions and design situations Design situations

Design situations have a key role to play in the selection of actions to include in design calculations and in the choice of partial factors to apply to both actions and material properties. Design situations are sets of physical conditions representing the real conditions occurring during a certain time interval for which the design will demonstrate that relevant limit states are not exceeded. The table below summarizes the design situations defined in EN 1990. The table below summarizes the...

Rat

Basement subject to uplift forces In this example, the resistance from friction on the basement walls is significant. Since it is a stabilizing action, this resistance should be an 'inferior' value, which may, counter-intuitively, come from 'superior' values of soil strength. The example also considers the use of tension piles to increase the stabilizing forces. The design of the individual piles should follow the methods described in Chapter 13. O Although a variable component of...

Basis of design

Serviceability limit states are defined as States that correspond to conditions beyond which specified service requirements for a structure or structural member are no longer met Verification of serviceability involves checking that design effects of actions (e.g. settlements) do not exceed their corresponding design limiting values (i.e. limiting settlements). Verification of serviceability is expressed in Eurocode 7 by the inequality Ed < Cd EN 1990 exp (6.13) & EN 1997-1 exp (2.10) in...

Ddv

Scope of EN 14475 Execution of special geotechnical works reinforced fill construction of earth retaining structures and reinforced slopes construction of reinforced embankments Supervision, testing, and monitoring (records during construction records at the completion of the works j- receipt and quality control of materials handling and storage j earth retaining structures and preparation of the W reinforced slopes site and foundation embankments with drainage of earth retaining structures...

Case studies selecting characteristic values

This section of the book presents a series of case studies that investigate the process of selecting a characteristic value (or values) from field and laboratory tests. The first study (see Section 5.4.1) considers two stiff over-consolidated clays found in London the second (Section 5.4.2) looks at the soft marine clay found in Singapore and the third (Section 5.4.3) considers dense, well-graded gravels at Gravesend in Kent. 5.4.1 London and Lambeth clays at Holborn Figure 5.10 shows the...

Construction Products Directive CE

In December 1988, the Commission of the European Community issued Council Directive 89 106 EEC (aka the 'Construction Products Directive'), which sets out essential requirements for all construction works ' products must be suitable for construction works which are fit for their intended use and satisfy the following essential requirements for an economically reasonable working life 1. Mechanical resistance and stability 3. Hygiene, health and the environment The Commission directed the...

De

Taylor & Francis Croup LONDON AND NEW YORK First published 2008 by Taylor & Francis 2 Park Square, Milton Park, Abingdon, Oxon OX14 4RN Simultaneously published in the USA and Canada by Taylor & Francis 270 Madison Avenue, New York, NY 10016, USA Taylor & Francis is an imprint of the Taylor & Francis Group, an informa business This edition published in the Taylor & Francis e-Library, 2008. To purchase your own copy of this or any of Taylor & Francis or Routledge's...

Design of embedded walls

The design of embedded retaining walls is covered by Section 9 of Eurocode 7 Part 1, 'Retaining structures', whose contents are as follows 9.1 General (6 paragraphs) 9.2 Limit states (4) 9.3 Actions, geometrical data and design situations (26) 9.4 Design and construction considerations (10) 9.5 Determination of earth pressures (23) 9.7 Ultimate limit state design (26) 9.8 Serviceability limit state design (14) An embedded wall is a relatively thin structure whose bending capacity plays a...

Design of slopes and embankments

The design of slopes and embankments is covered by Sections 11 ('Overall stability') and 12 ('Embankments') of Eurocode 7 Part 1, whose contents are as follows x.1 General (2 paragraphs in 11.1 and 2 paragraphs in 12.1) x.2 Limit states (2 and 2) x.3 Actions and design situations (6 and 8) x.4 Design and construction considerations (11 and 13) x.5 Ultimate limit state design (26 and 7) x.6 Serviceability limit state design (3 and 4) 11.7 Monitoring (2) and 12.7 Supervision and monitoring (5)...

Design requirements

3.2.1 Commitment to limit state design Perhaps the most significant requirement of Eurocode 7 is the following commitment to limit state design For each geotechnical design situation it shall be verified that no relevant limit state is exceeded. en 1997-1 2.1(1)P For many geotechnical engineers across Europe, this represents a major change in design philosophy, away from the traditional allowable (a.k.a. permissible) stress design involving a single, lumped factor of safety. Traditional...

Design situations and limit states

Limit states for slopes and embankments typically involve loss of overall stability of the ground and associated structures, excessive movement, loss of serviceability, or disruption of drains in an embankment dam. Section 12 includes an extensive list of additional limit states for embankments, including internal erosion surface erosion or scour deformations leading to loss of serviceability damage to adjacent structures problems with transition zones effects of freezing and thawing...

Qfk

Here the subscripts 'd' denote design values (i.e. after partial factors have been applied). When MEd MRd, so AGEO MRd MEd 1 and this term can therefore be eliminated from the bottom of the equation. This equation can be re-written in terms of characteristic parameters as The values of the partial factor grouping in this equation are given on page 269 for each of Eurocode 7's Design Approaches. Design Approach 1 applies partial factors to actions in Combination 1 and to unfavourable variable...

Ed Rd

Figure 13.6 shows a single pile subject to an imposed vertical action T, which attempts to pull the pile out of the ground. The uplift force is countered somewhat by the pile's self-weight W and the total vertical tensile action that results is Ft. The characteristic value of Ft is given by permanent and variable components of T, respectively the symbol WGk represents the pile's characteristic self-weight (a favourable permanent action) and is the combination factor applicable to the ith...

Effects of actions

In structural engineering, effects of actions are a function of the actions applied to a structure and that structure's dimensions, but not of material strength, i.e. where the notation E denotes that the design effect Ed depends solely on design actions Fdi and design dimensions adj. This holds true for linear elastic analysis of structures, but not for plastic analysis. An example may help to illustrate the ideas behind this equation. Figure 2.13 shows a simply-supported concrete beam subject...

Execution of geotechnical works

'The remit of CEN TC 288 is the standardization of the execution procedures for geotechnical works (including testing and control methods) and of the required material properties these documents have been prepared to stand alongside Eurocode 7 they provide full coverage of the construction and supervision requirements.'1 The 'execution standards' comprise a suite of twelve European standards, published over the period 1999 to 2007, which provide detailed guidance about construction and...

Footings subject to horizontal actions

For a spread foundation subject to horizontal actions, Eurocode 7 requires the design horizontal action Hd acting on the foundation to be less than or equal to the sum of the design resistance Rd from the ground beneath the footing and any design passive thrust Rpd on the side of the foundation Hd - Rd + Rpd EN 1997-1 exp (6.21) which is merely a re-statement of the inequality discussed at length in Chapter 6. Rather than work in terms of forces, engineers prefer to use shear stresses, so we...

Footings subject to vertical actions

For a spread foundation subject to vertical actions, Eurocode 7 requires the design vertical action Vd acting on the foundation to be less than or equal to the design bearing resistance Rd of the ground beneath it Vd < Rd EN 1997-1 exp (6.1) Vd should include the self-weight of the foundation and any backfill on it. This equation is merely a re-statement of the inequality discussed at length in Chapter 6. Rather than work in terms of forces, engineers more commonly consider pressures and...

Further information

We have established a website to support the book at Here you will find further worked examples, discussion of topics that wouldn't fit within these pages, and corrections of any errors in the manuscript that we become aware of. For ongoing news and views about the Structural Eurocodes, you can also visit Andrew Bond's blog, which he has been writing since May 2006, at

Future developments

As noted in the sub-sections in this chapter, the execution standards are subject to systematic review every five years (as are all European standards). Any confusion caused by conflicts between the execution standards and the provisions of Eurocode 7 and its associated geotechnical testing standards (discussed in Chapter 4) may therefore be remedied within a relatively short time scale, leading to a more coherent and consistent suite of geotechnical standards. In the UK, de facto standards...

Geotechnical Design Report

The contents of the Geotechnical Design Report are specified (as a Principle) in EN 1997-1 The assumptions, data, methods of calculations and results of the verification of safety and serviceability shall be recorded in the Geotechnical Design Report. EN 1997-1 2.8(1)P GDR Assumptions + Data + Methods + Verification The contents of the GDR are illustrated in Figure 16.6 and discussed below. The level of detail included in the GDR depends on the type of design -simple designs may only require a...

Geotechnical investigation and testing reports Drilling and sampling reports

Sampling methods and groundwater measurements are covered by EN ISO 22475, details of which are given in Chapter 4. EN ISO 22475-1 sets out the requirements for reporting the results of drilling, sampling, and groundwater measurements. Figure 16.2 summarizes the common features of these reports. Figure 16.2. Contents of a drilling and sampling report Figure 16.2. Contents of a drilling and sampling report These reports are similar to those defined in Section 7 of BS 59302 and represent typical...

Ground investigation for anchorages

Annex B.3 of Eurocode 7 Part 2 provides outline guidance on the depth of investigation points for the principal types of geotechnical structure, but does not give direct guidance on the spacing or depth of investigation points for anchorages. Since anchorages are used in conjunction with other structures, e.g. slopes, retaining walls, holding down basements, etc., the scope of investigation is governed by the structure that the anchorages help to stabilize. The properties of the ground should...

Ground investigation for embedded walls

Annex B.3 of Eurocode 7 Part 2 provides outline guidance on the depth of investigation points for retaining structures, as illustrated in Figure 12.1. (See Chapter 4 for guidance on the spacing of investigation points.) The recommended minimum depth of investigation, za, for excavations where the groundwater table is below formation level is the greater of and, where the groundwater is above formation level, the greater of za > (H + 2m) and za > (t + 2m) If H is small and t under-estimated,...

Ground investigation for footings

Annex B.3 of Eurocode 7 Part 2 provides outline guidance on the depth of investigation points for spread foundations, as illustrated in Figure 10.1. (See Chapter 4 for guidance on the spacing of investigation points.) The recommended minimum depth of investigation, za, for spread foundations supporting high-rise structures and civil engineering projects is the greater of za > 3bF and za > 6m where bF is the breadth of the foundation. For raft foundations za > 1.5bB The depth za may be...

Ground investigation for gravity walls

Annex B.3 of Eurocode 7 Part 2 provides outline guidance on the depth of investigation points for retaining structures, as illustrated in Figure 11.1. (See Chapter 4 for guidance on the spacing of investigation points.) The recommended minimum depth of investigation, za, for excavations where the groundwater table is below formation level is the greater of za > 0.4h and za > (t + 2m) Where the groundwater is above formation, za is the greater of za > (H + 2m) and za > (t + 2m) If all...

Xjb

The cross that appears against Aa indicates that tolerances are not normally applied to nominal dimensions. Second, partial factors are applied to ground strengths and variable actions, while non-variable actions and resistances are left unfactored. This is achieved by employing partial factors from Sets A2, M2, and R1 in what is termed 'Combination 2', as illustrated in Figure 6.10. Once again, the crosses on the diagram indicate that the partial factors in Sets A2...

Identification and classification of rock

Identification and classification of rock is covered by International Standard EN ISO 14689, which is divided into two parts covering description and classification (Part 1) and data transfer (Part 2).8 EN ISO 14689 is referenced extensively in EN 1997-2. Rock description according to EN ISO 14689-1 is based on the terms published by the International Society of Rock Mechanics (ISRM),9 in preference to those in BS 5930. Two stages are identified in the description of rocks rock material and...

Index

Accidental 21, 37, 41, 51, 82 characteristic 42-3, 60, 179-180, 204 combination of 41-2, 53 design 36, 39, 40-1, 43, 52-3, 80, 175, 179, 204 effect of 32, 34-5, 590 favourable 50, 80-1, 210, 269-270, 276, 278, 317, 320-1, 358, 361-2, 367-8, 413-421 geotechnical 79, 176, 184, 191-4, 269, 318, 420, 462 ground movements 75, 78, 264, 278, 450, 454 horizontal 57-58, 306, 315-6, 135, 179, 256, 309, 316, 322 structural 184-5, 191, 194, 329, 413 variable 39-41, 51, 179, 183, 187-8, 191, 193, 205,...

Info

Examples spread, raft, and pile foundations walls and other structures retaining or supporting soil or water excavations bridge piers and abutments embankments and earthworks ground anchors and other tie-back systems tunnels in hard, non-fractured rock, not subject to special water-tightness or other requirements 3 Structures or parts of Include alternative provisions and rules to those in structures not covered Eurocode 7 above Examples very large or unusual structures structures involving...

International Standardization Organization ISO

The International Organization for Standardization (known as ISO, after the Greek word 'isos' meaning 'equal') was founded in 1947 to 'facilitate the international coordination and unification of industrial standards'.13 ISO is a network of national standards bodies from 158 countries (comprising 103 member bodies, 46 correspondent members, and 9 subscriber members). Figure 1.5 illustrates the current membership of ISO. Based in Geneva, ISO has almost 200 technical committees (TCs) which are...

Introducing reliability into the design

Reliability is introduced into design against loss of serviceability by selecting suitable limiting values of displacement, as illustrated in Figure 8.3. Partial factors for serviceability limit states are normally taken as 1.0. Hence the equation for verification of serviceability (see Section 8.1) becomes Ed E F X, a < Cd d rep > , > nom J d and no partial factors are introduced in the flow diagram of Figure 8.3. The combination factors shown on Figure 8.3 are applied to accompanying...

Key features of the book

A distinctive feature of Decoding Eurocode 7 is its extensive use of flow diagrams (e.g. Figure 0.1), which help explain how reliability is introduced into the design process, and mind maps (e.g. Figure 0.2), which bring together a mixture of information into a coherent framework. The book is enhanced by a colour section between its middle pages. Figure 0.2. Key features of Decoding Eurocode 7 Figure 0.2. Key features of Decoding Eurocode 7 The book deliberately presents Principles and...

L

Single pile subject to downdrag Consider a pile installed through a superficial layer as shown in Figure 13.4. Consolidation of the layer (owing, for example, to fill being placed upon it) will occur after the pile has been installed, resulting in additional loading being applied to the pile. Soil-structure interaction analysis allows the 'neutral' depth (where the settlement of the consolidating matches that of the pile under load) to be determined, albeit approximately. In many...

Limit state STR

Limit state STR, dealing with rupture or excessive deformation, is defined as Internal failure or excessive deformation of the structure where the strength of construction materials governs. en 1990 6.4.1(1)P(b) To prevent limit state STR from occurring, design effects of actions Ed must be less than or equal to the corresponding design resistance Rd, i.e. Design effecl 7 VSfifV X. Design of actions - < _ > < - resistance Figure 2.8. Verification of limit state STR Returning to the...

Links between the Eurocodes

Figure 1.2 and Plate 3 (in the colour section) show the connections between the main parts of the Structural Eurocodes (in the style of the London Underground tube map). Only the main parts (not the sub-parts) of the Eurocodes are shown. Along the 'Central Line' (in red on Plate 3) are the ten parts (Parts 1) giving general rules and rules for buildings. For example, EN 1992-1 provides general rules for concrete structures. Around the 'Circle Line' (in yellow on Plate 3) are the six parts...

Looking ahead

Errors and ambiguities in the text of EN 1997 have already been discovered and are being reviewed by a 'Maintenance Group' for future correction. In the first instance, this will lead to publication of a corrigendum, dealing with essential changes to Eurocode 7, followed by a more considered amendment or revision some time after 2010. As our understanding of the nature of soils and rocks and the complex issues of soil-structure interaction improves, so Eurocode 7 will need further development....

Notes and references

Institution of Structural Engineers (2004), National Strategy for Implementation of the Structural Eurocodes, Institution of Structural Engineers. Quotation taken from p. 9. The report can be downloaded from www.istructe.org.uk technical files eurocodes.pdf. 2. The text of the Construction Products Directive is published on the European Commission's website (http ec.europa.eu). Follow the links to Enterprise > Industry Sectors > Construction > Directive 89 106 CE or go directly to the...

Outline of the book

Chapter 1 introduces the various Structural Eurocodes, the links between them, and their timetable for publication. This chapter places the Eurocodes into the wider landscape of standards development not only by the European Committee for Standardization (CEN), but also by the International Standards Organization (ISO) and various national standards bodies, such as the British Standards Institution (BSI) and its German counterpart, Deutsches Institut f r Normung (DIN). Chapter 2 discusses the...

Role of Eurocode in UK practice

A significant challenge facing each national standards body over the coming years is how to accommodate the Structural Eurocodes into its existing national standards. Figure 1.8 illustrates how Eurocode 7 interacts with various documents commonly used in UK geotechnical practice. These include so-called 'residual standards', i.e. existing British Standards that do not conflict with Eurocode 7 de facto standards such as Highways Agency and CIRIA documents and 'Published Documents' (PDs), which...

Scope of Eurocode Part

Eurocode 7 - Geotechnical design, Part 1 - general rules2 is divided into twelve sections and nine annexes, as shown in Figure 3.1 and Plate 5 of this book's Figure 3.1. Contents of Eurocode 7 Part 1. See Plate 5 for colour version. Figure 3.1. Contents of Eurocode 7 Part 1. See Plate 5 for colour version. colour section. In this diagram, the size of each segment of the pie is proportional to the number of paragraphs in the relevant section. Part 1 provides a general framework for geotechnical...

Scope of the book

Decoding Eurocode 7 provides a detailed examination of Eurocode 7 Parts 1 and 2 (ENs 1997-1 and -2), together with an overview of more than a hundred associated European and International standards that this major new geotechnical standard depends upon. The associated documents include another fifty-six standards in the Structural Eurocodes suite (ENs 1990 to 1999) sixty-one geotechnical investigation and testing standards (EN ISOs 14688, 14689, 17892, 22282, 22475, 22476, and 22477) and eleven...

Simplified verification of serviceability

In traditional geotechnical practice, serviceability limit states have been avoided by a variety of means, such as for foundations, limiting the bearing pressures underneath the foundation to 'allowable' (conservative) values for piles, by applying large safety factors to base and shaft capacities and for embedded retaining walls, using 'mobilization factors' to reduce the passive earth pressure assumed to achieve moment equilibrium. All these methods are fundamentally the same. They attempt to...

Stability of an infinitely long slope

Consider the classical problem of determining the stability of an infinitely long slope, as illustrated in Figure 9.3. If the slope is underlain by a permeable stratum, as shown in the top half of Figure 9.3, any water in the slope flows vertically downwards into the underlying stratum and, as a result, pore water pressures do not build up in the soil. The stability of this slope is identical to that of a dry slope with the same gradient p. Figure 9.3. Confined soil slopes overlying (top)...

Statistical methods for ground characterization

' Use of statistics demands a high order of statistical technique, available from very few designers who have committed their time to training and experience in geotechnical engineering.'24 The characteristic value of a material property Xk is defined in Chapter 2 as follows where mX is the mean of X, sX its standard deviation, and kn a statistical coefficient that depends on the number of samples n. This definition may be stated more simply as Characteristic value mean value + epistemic x...

Structural design

EN 1997-1 provides a short section on the structural design of spread foundations. It provides no guidance on the procedures for assessing the required amount or detailing of reinforcement in the concrete - this is dealt with by Eurocode 2.22 For stiff footings, Eurocode 7 recommends a linear distribution of ground stresses may be used to calculate bending moments and shear stresses in the foundation. For flexible rafts and strip foundations, an analysis based on a deforming continuum or an...

Summary of key points

'structural design is an iterative process of applying engineering mechanics and past experience to create a functional, economic, and, most importantly, safe structure for the public to enjoy'10 The Eurocodes - and in particular, EN 1990 - provide a comprehensive and cohesive framework for ensuring the safety of structures. The engineering concepts that are embodied in them have been used in engineering practice for decades and will be familiar to most structural engineers. The impact of the...

Supervision monitoring and maintenance

Slopes must be monitored when the occurrence of limit states cannot be proven sufficiently unlikely by calculation or prescriptive measures, or when the assumptions made in calculations are not based on reliable data. Monitoring should provide ground-water levels or pore-water pressures for effective stress analysis, lateral and vertical ground movements, the depth and shape of any existing slide for remedial work, and rates of movement. For embankments, Eurocode 7 Part 1 lists additional...

Traditional design

Traditional design based on geotechnical calculations is often verified by static pile load tests. Wherever possible preliminary pile load tests are carried out to failure, thereby establishing with some certainty the ultimate capacity of the piles in the particular ground conditions at the site. 'A factor of safety of 2.0 is often deemed sufficient when test piles have been loaded to failure. However 2.5 is recommended where only proof loads are applied to working piles.'10 When no pile tests...

Y

Integration of these equations allows the active effective earth and water thrusts (P'a and Ua on Figure 11.6) to be calculated P' j< adz and Ua j udz 0 0 where H is the height of the virtual plane above the base of the wall. Both of these actions are unfavourable for bearing, sliding, and toppling of the wall. Section 6 of Eurocode 7 Part 1 requires the design vertical action Vd acting on the wall's foundation to be less than or equal to the design bearing resistance Rd of the ground beneath...

Verification of stability

'Give me a lever long enough and a fulcrum on which to place it, and I shall move the world' - Archimedes (c. 287-212 BC) Verification of stability involves checking that destabilizing effects of actions do not exceed the corresponding stabilizing effects, plus any resistance that enhances those stabilizing effects. Verification of stability is expressed in Eurocode 7 by the inequality in which Ed,dst the design effect of destabilizing actions, Edstb the design effect of stabilizing actions,...

Verification of strength

'It is not possible to fight beyond your strength, even if you strive' - Homer (800-700 BC)1 Verification of strength to Eurocode 7 involves checking that design effects of actions do not exceed their corresponding design resistances. Verification of strength is expressed in Eurocode 7 by the inequality Ed < Rd EN 1990 exp (6.8) & EN 1997-1 exp (2.5) in which Ed the design effects of actions and Rd the corresponding design resistance. This requirement applies to ultimate limit state GEO,...

Walls and steep slopes

As Figure 15.1 shows, there are four published execution standards and one draft that are concerned with the execution of walls and steep slopes, as discussed in the following sub-sections. Figure 15.6 summarizes the scope of EN 12063,6 which deals with the execution of sheet pile walls including tubes and sheet piles, U-box and U-sheet piles, Z-box and Z-sheet piles, H-beams, and timber piles. No design methods are provided for establishing the length or modulus requirements for sheet piles...

Worked examples

The worked examples in this chapter illustrate the way in which statistics may be used to determine the characteristic values of various geotechnical parameters the standard penetration blow count in Thames Gravel (Example 5.1) the undrained strength of London Clay (Example 5.2) and the angle of shearing resistance of Leighton Buzzard Sand (Example 5.3). Specific parts of the calculations are marked O, , , etc., where the numbers refer to the notes that accompany each example. 5.7.1 Standard...

Yif

In Design Approach 2, partial factors are applied as late as possible in the calculation process, to action effects and resistances. This is a particular form of load and resistance factor design discussed in Section 6.4.3. The philosophy of Eurocode 7's Design Approach 3 is to check the foundation's reliability by applying partial factors to structural actions and to material properties simultaneously, while geotechnical actions and resistance are left mainly unfactored. (See below for...

Zi mz

The line labelled 'best fit' on Figure 5.18 gives values of cu which have a 50 probability of being exceeded by the local value of cu at the same depth. This line is readily calculated by spreadsheet programs using linear regression. The curve labelled 'lower characteristic' gives values of cu which have a 95 probability of being exceeded by the average value of cu over the depths considered. This is a 95 confident mean value and is the value most often needed in geotechnical designs which...

YBNY qult cN qN

Where Nc*, Nq*, and NY* are (modified) bearing capacity factors, c' is the soil's effective cohesion, q the overburden pressure at the base of the embankment, Y the weight density of the foundation soil, and B the width of the embankment. In Design Approach 1, Combination 1, partial factors on actions Yg 1.35 and yq 1.5 and on material properties y9 Yc 1.0 and Ycu 1.0. For B H 15 2 7.5, Nc* 8.1 , and q 0 Rd 16 x 8.1 129.6 kPa Ed 3.5 x 18 x 1.35 + 10 x 1.5 100.1 kPa Rd > Ed therefore OK,...

Za d and za m

The depth za may be reduced to 2m if the embankment or cutting is built on competent strata1 with 'distinct' (i.e. known) geology. With 'indistinct' fi.e. weaker strata are unlikely to occur at depth, structural weaknesses such as faults are absent, and solution features and other voids are not expected. geology, at least one borehole should go to at least 5m. If bedrock is encountered, it becomes the reference level for za. en 1997-2 B.3(4) Figure 9.1. Recommended depth of investigation for...

Za t m

If the wall is designed to cut off water flow into the excavation (see right-hand side of Figure 12.1), then the investigation should extend at least 2m into the impermeable stratum. The depth za may be reduced to 2m if the wall is built on competent strata1 with 'distinct' (i.e. known) geology. With 'indistinct' geology, at least one borehole should go to at least 5m. If bedrock is encountered, it becomes the reference level for za. en 1997-2 B.3(4) fi.e. weaker strata are unlikely to occur at...

Reinforced concrete walls

Earth Reinforced Concrete Wall

Figure 11.6 shows the pressures that act on a T-shaped gravity wall, assuming that a surcharge q exists at ground surface and the water table is located above formation level. The assumption is made that the wall's heel is wide enough for a Rankine zone to form within the backfill that sits on top of the wall's heel (see Section 11.4.4 for further discussion of this point). Figure 11.6 shows the pressures that act on a T-shaped gravity wall, assuming that a surcharge q exists at ground surface...

Piles subject to transverse actions

Eurocode Examples

Figure 13.7 shows a pile subject to transverse loading. This may be due to horizontal loads and moments applied at the head of the pile or due to lateral ground movements. The characteristic horizontal action is where HGk and HQk are characteristic permanent and variable components of H and is the combination factor applicable to the ith variable action (see Chapter 2). Whether the horizontal resistance is Figure 13.7. Single pile subject to governed by the lateral resistance of the transverse...

Ground investigation

Annex B.3 of Eurocode 7 Part 2 provides outline guidance on the depth of investigation points for pile foundations, as illustrated in Figure 13.1. (See Chapter 4 for guidance on the spacing of investigation points.) The recommended minimum depth of investigation below the base of the deepest pile, za, is the Figure 13.1. Recommended depth of investigation for pile foundations Figure 13.1. Recommended depth of investigation for pile foundations where bg is the smaller width of the pile group on...

Emirates Stadium Pile Tests

13.14.3 Static load tests for the Emirates Stadium in London Example 13.3 looks at the design of bored piles for the Emirates Stadium in London, the new home of Arsenal Football Club.18 Seven preliminary pile tests were carried out on piles of the same diameter, but with slightly different depths of penetration. Six of the piles (P1-3 and P5-7) were of similar length, between 23.5m and 26.3m, and one pile (P4) was significantly shorter, at 16.9m. All the piles were of bored construction. Ground...

Stability of a finite slope based on method of slices

Bromhead5 defines the factor of safety used in limit equilibrium methods as the ratio of the mobilized shear strength to the actual shear strength available. This is akin to applying a partial factor to material strength and hence those Design Approaches that apply partial factors to material properties are highly suited to the solution of slope stability problems. Methods for the limit equilibrium analysis of slopes range from simple translational sliding along a flat plane (as discussed in...

En En En En En En En En En

Piling Foundations Schematic

Assessment and retrofitting of buildings Plate 3. Connections between the main parts of the Structural Eurocodes (in the style of the London Underground tube map Transport for London) Plate 4. Connections between Eurocode 7 and associated European and International standards (based on the National Rail schematic map, Association of Train Operating Companies) Plate 4. Connections between Eurocode 7 and associated European and International standards (based on the National Rail schematic map,...

Earth pressure coefficients

EN 1997-1 Annex C provides a numerical procedure for determining active and passive earth pressure coefficients for use in retaining wall design, which is discussed in Chapter 12. The charts that follow show the variation in KaY and KpY (denoted Ka and Kp on these charts) with angle of shearing resistance 9, for different values of interface friction 5 (0 , 5 , 10 , 15 , 20 , 25 , and 30 ), for vertical walls (0 0 ). Each figure gives curves for different slope gradients tan p (flat, 1 10, 1 5,...

Design for serviceability

Design values of earth pressures for the verification of serviceability limit states must be derived using characteristic soil parameters, taking account of the initial stress, stiffness, and strength of the ground the stiffness of structural elements and the allowable deformation of the structure. These earth pressures may not reach limiting (i.e. fully active or passive) values. EN 1997-1 9.8.1(2)P, (4), and (5) Limiting values for the allowable wall and ground displacements must take into...

Verification by the partial factor method Partial factors on actions

Weak And Partial Structural Models

Representative actions (Frep) are converted into design values (Fd) by multiplying by an appropriate partial factor (yf) where yf takes account of uncertainties in the magnitude of the action, model uncertainties, and dimensional variations. For unfavourable actions, yf 1, whereas for favourable actions yf 1 and the previous equation is qualified as follows (see Figure 2.18) Values of yf and YF,fav for persistent and transient design situations are given in EN 1990 and vary between 0.9 and 1.5,...

Obtaining the characteristic value

EN 1990 defines a characteristic material property as follows where a low value is unfavourable, the characteristic value should be defined as the 5 fractile value where a high value is unfavourable, as the 95 fractile value en 1990 4.2(3) This definition works well for man-made materials, such as steel and concrete, but - as discussed below - fails to account for the remarkable variability of geomaterials and for the practical difficulty in obtaining measurements of relevant material...

Ground Investigation Report

Ground Investigation Eurocode Ppt

The requirement for a Ground Investigation Report GIR appears in EN 1997-2 The results of a geotechnical investigation shall be compiled in a Ground Investigation Report which shall form part of the Geotechnical Design Report. EN 1997-2 6.1 1 P The contents of the GIR are specified both in EN 1997-1 as an Application Rule and in EN 1997-2 as a Principle The Ground Investigation Report should normally consist of shall consist of, if appropriate a presentation of all available geotechnical...

Limiting equilibrium methods

Point Fixity

Limiting equilibrium methods are commonly used to assess the required penetration of embedded retaining walls, associated shear forces and bending moments in their cross-sections, and the forces in any props or anchors used to support them. Limiting equilibrium methods assume that the full strength of the ground is mobilized uniformly around the wall, so that the wall is at the point of collapse or 'limiting equilibrium' . Cantilever walls and walls propped near their top are statically...

Design of anchorages

The design of anchorages is covered by Section 8 of Eurocode 7 Part 1, 'Anchorages', whose contents are as follows 8.1 General 12 paragraphs 8.2 Limit states 1 8.3 Design situations and actions 2 8.4 Design and construction considerations 15 8.5 Ultimate limit state design 10 8.6 Serviceability limit state design 6 8.7 Suitability tests 4 8.8 Acceptance tests 3 8.9 Supervision and monitoring 1 Section 8 of EN 1997-1 applies to prestressed and non-prestressed anchorages both temporary and...

Slope Stability Da3 Eurocode

TChoice made in Eurocode 7 Designers' Guide3 It is unclear whether this should be Yes or No tChoice made in Eurocode 7 Designers' Guide3 It is unclear whether this should be Yes or No 6.3.4 Choice of design approach by different European countries Eurocode 7 Part 1 allows each country to specify in its National Annex which design approach must be used within its jurisdiction. The choices made by the countries within CEN4 are summarized in Figure 6.18 for slopes and Figure 6.19 for other...

The Structural Eurocode programme

The Structural Eurocodes are a suite of ten standards for the design of buildings and civil engineering works, as illustrated in Figure 1.1 and Plate 2 in the book's colour section . These standards are divided into fifty-eight parts and are accompanied by National Annexes issued by the various European countries that have introduced the Eurocodes into their design practice. Figure 1.1. Standards within the Structural Eurocodes programme. See Plate 2 for colour version. Figure 1.1. Standards...

Slope stability design charts

This appendix provides charts for designing infinitely long slopes and slopes subject to circular slips according to Design Approach 1. The charts for infinitely long slopes Figure A1.1 to Figure A1.3 are based on the equation for the 'characteristic' stability number Nk that is developed in Chapter 9,with partial factors yg, Yc Y9, and YRe from Design Approach 1. Each chart represents a different ru value 0, 0.3, or 0.5 and the numbers on the curves 1 1, 1 1.5, etc. represent the gradient of...

Comparison with existing practice

Standard Penetration Test

The following sub-sections compare the Ground Investigation and Geotechnical Design Reports with traditional reports on these subjects. Current UK practice is specified in Section 7 of BS 5930,5 which defines the series of reports illustrated in Figure 16.7. Field reports cover all the information that needs to be obtained while working on site, e.g. the recording of in situ tests such as the standard penetration test, cone penetration test, pressuremeter, etc. and production of drillers' logs....

Active Earth Pressure

What Earth Pressure

Curve 1 on each graph shows the results obtained for a serviceability limit state calculation, with all partial factors set to 1.0 - i.e. with all parameters at their characteristic values. The depths of embedment needed to ensure stability for this situation are 9.63m and 7.00m respectively for the two walls. Curve 2 shows the results obtained when passive earth pressures are treated as an unfavourable action, as allowed by the Single-Source Principle discussed in Chapter 3. A single partial...

M

Design is unacceptable if degree of utilization is gt 100 It is assumed that the uplift on the base of the wall can be represented by a simple triangular distribution, reducing from a maximum pressure at the heel to zero at the toe. For sliding resistance, vertical actions on the wall heel are favourable and so variable actions are ignored. However, the uplift due to the water pressure is unfavourable and results in a lower effective vertical force for DA1-1 compared with DA1-2. This results in...

Reaction to the Eurocodes

The Eurocode Scream Jack Offord

Unfortunately, many engineers' initial reaction to Eurocode 7 is a cross between The Eurocode Scream see Figure 17.1 and the natural instinct of an ostrich, which , when frightened, buries its head in the sand. However, when the shock of the new is overcome, views change as the benefits of the Eurocodes become apparent. The views of many engineers are based on limited knowledge of the Eurocodes and even less experience of using them in practice. Figure 17.2 summarizes some of the opinions that...

Mass gravity walls

Figure 11.9 shows the pressures that act on a mass gravity wall, assuming that a surcharge exists at ground surface and the water table is located above formation level. Because the back face of the wall is inclined at an angle 0 to the vertical, the effective earth pressures acting on the wall are inclined. The simplification made for reinforced concrete walls, of a Rankine zone behind the wall see Section 11.4.4 , is not valid for this situation. Figure 11.9. Earth pressures acting on a mass...

European Committee for Standardization CEN

The European Committee for Standardization known as CEN, after its French name Committ Europ en de Normalisation was founded in 1961 by the national standards bodies in the European Economic Community EEC and the European Free Trade Association EFTA .16 Based in Brussels, CEN currently comprises thirty national members, seven associates for example, the European Construction Industry Federation, FIEC , and two counsellors representing the EEC and EFTA four affiliates mainly central and eastern...

Ground characterization

Ground Characterization

'In dealing with real world problems, uncertainties are unavoidable'1 5.1 From test results to design Ground characterization is the process of deducing suitable values for geotechnical parameters from the results of field or laboratory tests. Ultimately, these values will be used in design calculations, after the application of appropriate partial factors to cater for uncertainties in the available data. There are three distinct steps in this process, as shown in Figure 5.1. Put simply,...

Eurocode Retaining Wall Stem Design Example

Retaining Wall Design Example

The worked examples in this chapter consider the design of a T-shaped gravity wall retaining dry fill under undrained conditions Example 11.1 the same wall under drained conditions Example 11.2 the same wall again, retaining wet fill under drained conditions Example 11.3 and a mass concrete wall retaining granular fill Example 11.4 . Specific parts of the calculations are marked O, , , etc., where the numbers refer to the notes that accompany each example. 11.11.1 T-shaped gravity wall...

Soilstructure interaction analysis

Eurocode 7 notes that, for anchored or strutted flexible walls, the magnitude and distribution of earth pressures, internal structural forces, and bending moments depend to a great extent on the stiffness of the structure, the stiffness and strength of the ground, and the state of stress in the ground. If structural stiffness is significant, soil-structure interaction analysis should be performed to determine the distribution of actions. The stress-strain relationships used in such analyses...

Who writes what

A number of organizations are likely to be involved in the preparation of geotechnical reports design consultant structural or geotechnical site investigation contractor design-and-build contractor. Although this list may not include all parties that might be involved in a construction project, we will use it to illustrate the potential changes that Eurocode 7 will have on the production of geotechnical reports. The client is unlikely to be involved in the preparation of either the Ground...

QEk A A

Footings With Biaxial Moments

Where Vrep is a representative vertical action VGk, VQk, and WGk are as defined above A' is the footing's effective area defined in Section 10.4.2 and is the combination factor applicable to the ith variable action see Chapter 2 . If we assume that only one variable action is applied to the footing, this equation simplifies to since 1.0 for the leading variable action i 1 . The design bearing pressure qEd beneath the footing is then where yg and yq are partial factors on permanent and variable...

Eurocode 7 Worked Examples

Eccentrically Loaded Footings

The worked examples in this chapter consider the design of a pad footing on dry sand Example 10.1 the same footing but eccentrically loaded Example 10.2 a strip footing on clay Example 10.3 and, for the same footing, verification of the serviceability limit state Example 10.4 . Specific parts of the calculations are marked O, , , etc., where the numbers refer to the notes that accompany each example. Example 10.1 considers the design of a simple rectangular spread footing on dry sand, as shown...

Identification and classification of soil

Columns Eurocodes

Identification and classification of soil is covered by International Standard EN ISO 14688, which is divided into three parts covering description Part 1 , classification Part 2 , and data transfer Part 3 .6 EN ISO 14688 is referenced extensively in EN 1997-2. Figure 4.6 illustrates the logic for identifying soils according to EN ISO 14688-1. The main soil types are divided into made ground, organic soil, volcanic soil, and very coarse, coarse, and fine soils. Very coarse soils are sub-divided...

Principles of limit state design

The Structural Eurocodes are based on limit state principles, in which a distinction is made between ultimate and serviceability limit states. Ultimate limit states are concerned with the safety of people and the structure. Examples of ultimate limit states include loss of equilibrium, excessive deformation, rupture, loss of stability, transformation of the structure into a mechanism, and fatigue. Serviceability limit states are concerned with the functioning of the structure under normal use,...

UkM rw h d yw d j

Magnel Diagram

D,dst Yg,dstYw y dj Yg,dstYw 1 d and, since this is a permanent destabilizing action, its design value is The characteristic vertical total stress acting on the same plane is and, since this is a permanent stabilizing action, its design value is Substituting these expressions into ud dst lt od stb and simplifying produces -1 hnL _ I j 0.33 - hnL 1.5 I 3 I 3.0 1. For this situation, we conclude that the partial factors specified for limit state HYD are equivalent to a global factor of 3.0 on the...

Utilization Factor Structural Design

Sheet Pile Basal Heave

The design is unacceptable if the degree of utilization is gt 100 Traditional factor of safety against piping The soil's critical hydraulic gradient is i crit - 1 Factor of safety on hydraulic gradient is F - 3.38 w 0 The degree of utilization using expression 2.9 a is close to 100 , whereas using 2.9 b it is less than 50 . Eurocode 7 does not explicitly state where the partial factors should be applied, which leads to the discrepancy between these expressions, which was not anticipated by the...

Anchorage tests

Proof Load Yield

Eurocode 7 discusses three types of anchorage test investigation, suitability, and acceptance. An investigation test is a 'load test to establish the ultimate resistance of an anchor at the grout ground interface and to determine the characteristics of the anchorage in the working load range'. This definition is identical to the one given in EN 1537. EN 1997-1 8.1.2.5 Investigation tests are performed, before working anchorages are installed, to establish the anchorage's ultimate pull-out...

Material properties and resistance Resistance

Concrete Stress Block Eurocode

The resistance of a structural member is defined as the capacity of a member or component, or cross-section of a member or component of a structure, to withstand actions without mechanical failure In structural engineering, resistance is a function of the structure's material strengths and its dimensions, but not of the magnitude of any actions applied to the structure, i.e. where the notation R denotes that the design resistance Rd depends solely on design material strengths Xdi and design...

Limit state EQU

Limit state EQU, dealing with static equilibrium, is defined as Loss of static equilibrium of the structure considered as a rigid body, where minor variations in the actions or their distribution are significant, and the strengths of materials are generally not governing. Limit state EQU does not occur when the destabilizing design effects of actions Ed,dst are less than or equal to the stabilizing design effects Ed,stb Ed, dst Ed,stb EN 1990 x 67 Ed, dst Ed,stb EN 1990 x 67 Figure 2.6....

Actions combinations and effects

The use of the word action to describe loads and other entities that act like loads reminds us of Newton's Third Law of Motion 'To every action there is always opposed an equal reaction.'6 In Eurocode terms, the 'reaction' is known as an effect. That is action cause The following sub-sections explain the way in which the Structural Eurocodes define actions, combinations of actions, and the effects that arise from them.

Combinations of actions

Favourable Permanent Action

Representative actions Frep are obtained by assembling suitable combinations of characteristic values Fk , following the rules given in ENs 1990 and 1991. The representative value of a single generic action is given by where is a combination factor, less than or equal to 1.0. The combination factor is omitted for permanent actions, i.e. a representative permanent action G,j is equal to its characteristic value Gkj . The total design permanent action Gd is then obtained from the sum of the...

Pile Negative Friction Eurocode

Retaining Wall Design Example Eurocode

Eurocode 7 requires consideration of both short- and long-term design situations, to reflect the sometimes vastly different resistances obtained from drained and undrained soils. At first sight, the requirements of EN 1997-1 appear to cut across those of EN 1990. However, it is not difficult to combine these ideas to cater for common geotechnical problems Persistent Normal Long Buildings and bridges founded on coarse soils and fully-drained fine soils Short Partially-drained slope in fine soils...

Deriving geotechnical parameters Overview

Eurocode Clay Shear Strength

The derived value of a geotechnical parameter is defined in Eurocode 7 as the value obtained by theory, correlation or empiricism from test results EN 1997-1 1.5.2.5 amp EN 1997-2 1.6 3 As the flow-chart of Figure 5.2 illustrates, test results may be converted into derived values X by use of correlations such as that between cone penetration resistance and angle of shearing resistance in sand , theoretical considerations such as conversion of triaxial compression into plane strain strengths for...

Standards for geotechnical investigation and testing Eurocode Part

Geotechnical Investigation

Eurocode 7 - Geotechnical design, Part 2 - ground investigation and testing2 is divided into six sections and twenty-four annexes, as illustrated in Figure 4.1 and Plate 6 in the book's colour section . 2 Planning of ground 1 General Investigations 3 Soil and rock Figure 4.1. Contents of Eurocode 7 Part 2. See Plate 6 for a colour version. 2 Planning of ground 1 General Investigations 3 Soil and rock Figure 4.1. Contents of Eurocode 7 Part 2. See Plate 6 for a colour version. EN 1997-2 provides...