Ground Investigation Report
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...
Info Cbe
The volume of backfill on top of the foundation is Vf Ab x d - Vc 379.8 m3 Thus, the characteristic self-weight of the foundation concrete plus backfill is then backfill WGkf ykf x Vf 6836 kN total WGk WGk c WGk f 14217 kN The characteristic uplift force from groundwater pressure acting on the underside of the base is UGk yw x D x B x B 6622 kN Effects of actions Partial factors on destabilizing permanent and variable actions are yG dst 1.1 and yq dst 1.5 and on stabilizing permanent actions...
Info Vde
Design is unacceptable if the degree of utilization is gt 100 Design is unacceptable if the degree of utilization is gt 100 The correlation factors given in the UK NA to BS EN 1997-1 are higher because existing UK practice suggests the correlation factors in EN 1997-1 may lead to unsafe designs. The resulting characteristic resistance is significantly reduced compared with the EN 1997-1 calculation. In addition, the R4 resistance factor is higher than that given in Annex A of EN 1997-1, leading...
Limiting equilibrium methods
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...
B Lmw
Divide clay layer into N 5 sub-layers of thickness At - - 0.6 m For each layer i 1 N, the depth below base to the centre of each layer is At given by zi At x i and the normalized foundation half breadth by B mi -. The influence factor Iq Iq mi can be found from Fadum's chart. The change in vertical stress in each layer is A av 4Iq Aqd and the settlement in each layer pc m Actv At.O Substituting values into the previous expressions gives settlement in each layer pc m Actv At.O Substituting...
Design for serviceability 1
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 Calculations of wall movement are not necessarily required to verify the avoidance of...
Info Jdc
where cu ov' nc has been assumed to be 0.23. This relationship assumes the removal of overburden pressure due to geological processes for the line labelled 'minimum', 5m of overburden is removed and, for the one labelled 'maximum', 70m. There are seven results in London Clay solid squares and five results in Lambeth Clay open squares that are below the minimum these may be considered physically impossible values for the in situ clay. There are also four results in London Clay that are above the...
H Kby
Figure 7.5 illustrates the consequences of the above for a dam retaining various depths of soil, assuming ys 20kN m3, yc 24kN m3, yw 10kN m3, 9 25 hence Ka 0.406 , and 5 35 . The lines labelled 'Traditional' are based on Fs 1.5 for sliding and Fo 2.0 for overturning. As Figure 7.5 shows, overturning governs the minimum width of the dam for all heights of retained soil. Of course, had we assumed a smaller value of interface friction 5 then sliding might have governed the dam's width. An...
R Yxn
Design is unacceptable if degree of utilization is gt 100 Characteristic total action same as Design Approach 1 Partial factors from set A1 yq 1-35 and yq 1-5 Design total action per pile is Fcd Yg Fsk Yq Fq 1110 kN Characteristic resistance Characteristic resistance is same as Design Approach 1 Design resistance Partial factors from set R2 Yt 1-1 Design resistance is Rcd - 1000 kN Verification of compression resistance Design values Fcd 1110 kN and Rcd 1000 kN Design is unacceptable if degree...
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...
Info Lkz
Note that the results obtained from a Design Approach 2 analysis depend critically on how the partial factors are applied. Neither of the two methods described in and above is commensurate with traditional practice, which is to search for a required material factor of safety of 1.3. Owing to these uncertainties, Design Approach 2 is not recommended for slope stability assessments. The approach for Design Approach 3 DA3 is identical to that for DA1-1, except that the imposed surcharge is treated...
Info Wlh
This approach has been used in Denmark since the early 1960s and was first codified in the 1965 Danish Code of practice for foundation engineering.8 It has since been widely adopted in European practice, for example in BS 8002.9 6.4.3 Load and resistance factor design LRFD In northern America, an alternative approach to geotechnical design based on limit state principles has become popular, recently being incorporated into AASHTO's bridge design specifications,10 the American Petroleum...
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...
Medium dense gravelly SAND grSa
Figure 13.18. Concrete pile driven into clay and sand The design in this example compares the three Design Approaches discussed in Chapter 6, using the partial factors specified in Annex A of EN 1997-1. Eurocode 7 emphasises design of piles via testing and gives little guidance to design by calculation. This example uses standard UK calculation procedures and highlights some areas where there is debate how Eurocode 7 should be applied. O Unlike other geotechnical structures, for DA1 the partial...
Notes and references Jdg
1. From the foreword to EN 1537. The forewords to the other execution standards carry similar wording. 2. Five of the thirteen execution standards all of 1999-2001 vintage use the singular word 'work' instead of 'works' in their titles. Why the title of this suite includes the word 'special' is a mystery. 3. BS EN 1536 2000, Execution of special geotechnical work - Bored piles, British Standards Institution. 4. BS EN 12699 2001, Execution of special geotechnical work -Displacement piles,...
Comparison with existing practice
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
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 Bhn
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
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...
Reinforced fill structures
'Eurocode 7 does not cover the detailed design of reinforced fill structures. The values of the partial factors given in EN 1997-1 have not been calibrated for reinforced fill structures.'6 The design of reinforced fill structures is currently carried out according to national standards, such as British Standard BS 8006.7 Although national standards share many common features, differences in working practices, geology, and climate, etc. have delayed the development of a single design method...
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...
O Uyt
The dam retains a mixture of water to a height hw and soil to height hs . The soil is considerably weaker than the underlying rock. The total horizontal thrust P on the back of the dam is given by where yw and Ys are the weight densities of water and the soil and Ka is the soil's active earth pressure coefficient, which is assumed here for simplicity to be given by 1 - sin with 9 the soil's angle of shearing resistance. The destabilizing i.e. overturning moment that the earth and water...
Notes and references Rft
1. Driscoll, R.M.C., Powell, J.J.M., and Scott, P.D. 2008 EC7 - implications for UK practice, CIRIA RP701. 2. BS EN 1997-2 2007, Eurocode 7 - Geotechnical design, Part 2 - Ground investigation and testing, British Standards Institution, London, 999pp. 3. BS EN ISO 17892, Geotechnical investigation and testing Laboratory testing of soil, British Standards Institution. Part 1 Determination of water content. Part 2 Determination of density of fine grained soil. Part 3 Determination of density of...
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,...
About the authors
Andrew Bond MA MSc PhD DIC MICE CEng is a UK delegate on the Eurocode 7 committee, a former member of the UK's National Strategy Committee, and co-author of BSI's Extracts from the Structural Eurocodes for students of structural design. He is a former editor of Geotechnical Engineering. Andrew gained first class honours from Cambridge University in 1981, before working for WS Atkins and Partners on a variety of civil, structural, and geotechnical engineering projects. He obtained his MSc from...
Ground improvement
As Figure 15.1 shows, there are five execution standards concerned with the execution of ground improvement, as discussed in the following subsections. Figure 15.10 summarizes the scope of EN 12715,17 which deals with the execution of grouting including non-displacement and displacement grouting but excluding jet grouting, which is covered by EN 12716 see Section 15.4.2 . The standard identifies three types of grout solution, suspension, and mortar and outlines their characteristics and...
Notes and references Ijz
1. See, for example, Fleming, W. G. K., Weltman, A. J., Randolph, M. F., and Elson, W. K. 1992 Piling Engineering 2nd edition , Glasgow Blackie amp Son Ltd., 390pp. 2. Institution of Civil Engineers 2007 ICE specification for piling and embedded retaining walls known as SPERW . 3. ISSMFE Subcommittee on Field and Laboratory Testing 1985 , 'Axial Pile Loading Test, Suggested Method', ASTM Journal, pp. 79-90. 4. BS EN ISO 22477, Geotechnical investigation and testing Testing of geotechnical...
Eurocode Retaining Wall Stem 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...
H Ipe
dw for H lt 4m and dw 1m for H gt 4m which is less onerous than Eurocode 7's requirements.1 It is rare for the water table to rise to ground surface and thus Eurocode 7's requirement could be regarded as too conservative. When the natural water Consideration is being given to changing Eurocode 7's requirements from a Principle 'shall' to an Application Rule 'should' in a future revision. table can be demonstrated to come below formation level, it is advisable to assume less onerous water levels...
Notes and references Uxi
1. See Tables 1-3 of BS 8004 1986, Code of practice for foundations, British Standards Institution. 2. See, for example, Tomlinson, M. J. 2000 Foundation design and construction 7th edition , Prentice Hall or Bowles, J. E. 1997 Foundation analysis and design 5th edition , McGraw-Hill. 3. Meyerhof, G. G. 1963 'Some recent research on the bearing capacity of foundations', Can. Geotech. J., 1 1 , pp. 16-26. 4. Buisman, A. S. K. 1940 Grondmechanica, Delft, The Netherlands Waltman Terzaghi, K. 1943...
Info Rcw
Angle of shearing resistance, cp degrees Figure 10.6. Bearing capacity factors Nq, Nc, and Nr 10.4.4 Non-dimensional factors applied to the triple-N formula Various modifications to the triple-N equation have been proposed, usually involving the introduction of factors to cater for the effects of the foundation's shape, depth, and, base inclination inclination of the applied load and inclination of the ground surface. The 'complete' expression for qult is quit cN cScdcicgcbc q'Nfydqiqgqbq where...
qEk A A
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
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
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...
Notes and references Jio
1. BS EN 1537 2000 Execution of special geotechnical work Ground anchors, British Standards Institution. 2. BS EN 1997-2 2007 Eurocode 7 Geotechnical design Part 2 Ground investigation and testing, British Standards Institution. 4. BS EN ISO 22477-5, Geotechnical investigation and testing Testing of geotechnical structures, Part 5 Testing of anchorages, British Standards Institution. 5. Devon Mothersille pers. comm., 2008 . 6. BS 8081 1989, Code of practice for ground anchorages, British...
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,...
Basis of design Qpk
Eurocode 7 requires embedded walls to be designed with sufficient embedment to prevent rotational and vertical failure. The wall's cross-section and any supports it relies upon must be verified against structural failure see Section 12.7 . Furthermore, embedded walls must not fail due to overall instability of the ground in which they are installed. EN 1997-1 9.7.2 1 P, 9.7.4 1 P, 9.7.5 1 P, and 9.7.6 1 P Regrettably, Eurocode 7 gives little detailed guidance on the design of embedded retaining...
ukM rw h d yw d j
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...
Hyd 1
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
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...
Supervision monitoring and maintenance Avc
Apart from two paragraphs on the preparation of the ground, 6 of EN 1997-1 provides no additional rules regarding supervision, monitoring, and maintenance to those given in 4. 4 of EN 1997-1 requires the construction processes and workmanship to be supervised, the structure's performance to be monitored both during and after construction, and the structure to be maintained. As discussed in Chapter 16, these requirements must be stated in the Geotechnical Design Report GDR so that...
Info Hhc
Epistemic uncertainty is highly relevant to geotechnical engineers, who rarely have sufficient test data with which to justify a statistical approach to parameter selection. In 1991, the Ground Board of the UK's Institution of Civil Engineers published a report10 on site investigation, which recommended 'National guidelines on the extent, intensity and quality of ground investigation should be produced for the benefit of clients, planners and engineers. These guidelines should follow the...
Material properties and resistance Resistance
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.