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Geotechnical Engineering And Eurocode 7 Construction Essay | bluecrewsportsgrill
HomeArticlesGeotechnical Engineering And Eurocode 7 Construction Essay
Driscoll and Simpson ( 2001 ) province: ‘Geotechnical technology has long stood out from the other professional subjects within civil and structural engineering- non least for their attack to plan ‘ . Geotechnical design is an technology design associating all elements affecting the land, including foundations of undertakings. EN 1997 Eurocode 7 is the British Standard for this design, Geotechnical Design, which replaced the old criterion DD ENV 1997-1, DD ENV 1997-2, DD ENV 1997-3 and partly the BS 5930:1999 and BS 1377-9 ( Eurocode 7-part1, 2004 ) . It is divided into two parts ; BS EN 1997:1 2004 Part 1General Rules and BS EN 1997:2 2007 Part 2 Ground probe and testing ( Eurocode 7-part1, 2004 ) . The first portion was published on 22 December 2004 and the second on 2007 under the authorization of the criterions Policy and Strategy Committee and it was corrected in February 2009. From April 2010 it is compulsory for the all the public plants.
Eurocode 7 is really different from the old codifications for geotechnical design as it is a comprehensive bound province. It contains some cardinal design demands that must be satisfied by all the constructions. It besides uses characteristic values and partial factors with three design attacks. It can be defined as a utile tool which provides counsel for geotechnical design offering the necessary demands for stableness, strength, lastingness, serviceableness and safety for the constructions ( Orr, 2002 ) . A system of three geotechnical classs was introduced in this codification which helps to sort hazards in design. This chapter focuses on these alterations from Eurocode 7 to Geotechnical Design.
In 1976 the European Commission decided to back up the development of European codifications for edifices constructions ( Beal, 2010 ) . In 1980 the European Commission requested the International Society of Foundation Engineering and Soil Mechanics to reexamine the bing codifications about geotechnical design and bill of exchange a codification called Eurocode 7 ( Driscoll and Simpson, 2001 ) . The Society, after many international meetings and audiences, presented the first bill of exchange theoretical account of this codification in 1987. After three old ages work on the codification, in1990, the codification was transferred to European Committee for Standardization ( CEN ) for more development, issue and care. In 1994 the portion 1 of the Eurocode was published as prestandard ENV ( EuroNorm Vornorm ) and after one twelvemonth was published by British Standards Institution ( BSI ) . The codification was further developed into a EuroNorm ( EN ) criterion in 1997. In 1998, a commentary was published in UK to assist applied scientists to understand better the usage of Eurocode and give some illustrations of its application. In 1999 more accounts about Eurocode were published ( Driscoll, 1997 ) . On 22 December 2004 the European criterion EN 1997-1 Eurocode 7: Geotechnical Design, Part 1: General Rules and in 2007 the European criterion EN 1997-2 Eurocode 7: Geotechnical Design, Part 2: General Rules were published under the authorization of the criterions Policy and Strategy Committee. The Eurocode was written in three linguistic communications ; the official EU languages English, German and Gallic. In 2006 the national Annex ( NA ) was written. Eurocode was corrected in February 2009. From April 2010 its usage is compulsory for the all the public plants ( Eurocode 7-part1, 2004 ) .
Eurocode 7 is developed for the undermentioned grounds:
To set up the demands and rules for serviceableness and safety, explain the footing of design and besides of confirmation and give guidelines for structural dependability when used in concurrence with EN 1990.
To be applied in geotechnical characteristics of the design of civil technology plants and edifices
To supply the necessary demands for stableness, strength, lastingness, safety and serviceableness for the constructions.
To give the appropriate regulations for the computation of actions imposed by the land like Earth force per unit areas.
To handle affairs of craft and executing ( Eurocode 7-part1, 2004 )
Eurocode 7 is used in concurrence with the National Annex, EN 1997. This standard provides alternate values and processs which gives notes where national picks are made.
BS EN 1997- 2: 2007 Eurocode 7: Geotechnical Design- Part 2: Land probe and proving
EN 1997-1 provides design counsel and actions for the geotechnical design of civil technology plants and edifices ( Eurocode 7-part1, 2004 ) . The of import points of this portion are that it gives accent on the serviceableness necessity for geotechnical design and on the importance of geotechnical probes ( Driscoll, 1997 ) . It gives the definitions of land parametric quantities, information about characteristic and design values and some premises about the executing processs. It is a utile tool for interior decorators, clients, public governments and contractors ( Eurocode 7-part1, 2004 ) . It gives small information or aid in interior decorator analysis, these are obtained in other texts for more information. Driscoll ( 1997 ) points out that the codification is besides used in concurrence with other CEN paperss and Eurocodes.
In general EN 1997-1 screens the undermentioned subjects:
Footing of geotechnical design
Geotechnical informations
Supervision of building, monitoring and care
Fill, dewatering, land betterment and support
EN 1997- 2 is used in concurrence with EN 1997-1. It provides counsel for planning and coverage of land probes, for reading and rating of trial consequences, gives demands for field and research lab trials, and derives values of geotechnical coefficients and parametric quantities. It is used by interior decorators, clients, field proving research labs, public governments and geotechnical research labs. Furthermore, illustrations of field and laboratory trial consequences are given. It does non supply counsel for environmental land probes ( Eurocode 7-part2, 2007 ) .
EN 1997- 2 covers the followerss subjects:
Planning of land probe
Dirt and stone sampling and groundwater measurings
Field trials in dirt and stone
Lab trials on dirt and stone
The execution of Eurocode 7 changes the geotechnical design procedure from the old criterions. Harmonizing to Kavvada ( 2007 ) these alterations were required for the undermentioned grounds:
Eurocode 7 offers a unvarying design method of structural and geotechnical plants.
It offers a unvarying design method of plants in European Union.
It provides professional applied scientist ‘s ‘cover ‘ ( designed by EC 7-1 )
It provides more rational direction of safety issues
The alterations in the Eurocode 7 to Geotechnical design are as follows.
Eurocode 7 contains cardinal demands that must be satisfied by all constructions in the geotechnical design. For these demands there are no options unless justified in specific state of affairss. They contribute to the structural safety, serviceableness and lastingness. Some of these demands as referred in Eurocode 7-part ( 2004 ) follow:
It shall be checked that no relevant bound province ( as defined in EN 1990 ) is exceeded in each geotechnical design.
The undermentioned factors should be taken into history when specifying the design state of affairss and bound provinces:
Size and nature of constructions: simple, light, on good house land structures or big, sensitive constructions on soft land or deep diggings near to old edifices. It should be used simplified design processs for visible radiation and simple geotechnical constructions and computations with more extended probes for more complex constructions.
Conditionss with respects to the milieus: these are of import because of the effects that neighboring constructions can hold on the new construction or the effects that the new construction can hold on the neighbouring constructions.
Land H2O conditions: the pore H2O force per unit areas should be investigated in order to avoid geotechnical failures, such as base heaving in piping and diggings, and landslides due to high pore force per unit areas.
Influence of the environment: factors such as surface H2O, hydrology, alterations on temperature, etc.
Limit provinces should be checked by one or more of the followers: usage of computations, burden trials and experimental theoretical accounts, observation method and execution of normative steps.
Three Geotechnical Categories ( 1, 2, and 3 ) should be introduced to set up geotechnical design demands. The Geotechnical Category should be defined prior the geotechnical probes and it should be checked and changed at each phase of design and building, if it is necessary.
4.4.2. Geotechnical Classs
Eurocode 7 introduced a system of three geotechnical classs ( class 1, 2, 3 ) . The choice of a class for a construction is based on the degree of complexness of a design. The Highways Agency ( 2008 ) points that the classs based on the grade and complexness of geotechnical hazard in geotechnical design. Geotechnical jeopardies and the exposure of the construction to specific jeopardies are the two factors of the geotechnical hazard map. Geotechnical jeopardies are related with the land conditions, groundwater, environment and seismicity factors, and exposure with the construction and surroundings factors. Table 4.1 presents the different degrees of complexness for these factors in the different classs and the related geotechnical hazards.
Geotechnical Classs
Geotechnical jeopardies
Known from comparable experience to be straightforward. Not affecting soft, loose or compressible dirt, loose fill or inclining land.
Land conditions and belongingss can be determined from everyday probes and trials.
Unusual or exceptionally hard land conditions necessitating not everyday probe and trials.
Groundwater state of affairs
No diggings below H2O tabular array, except where experience indicates this will non do jobs.
No hazard of harm without anterior warning to constructions due to groundwater take downing or drainage. No exceeding H2O stringency demands
High groundwater force per unit areas and exceeding groundwater conditions, e.g. multilayered strata with variable permeableness
Areas with no or really low temblor jeopardy
Moderate temblor jeopardy where seismal design codification ( EC8 ) may be used
Areas of high temblor jeopardy
Negligible hazard of jobs due to come up H2O, remission, risky chemicals, etc.
Environmental factors covered by everyday design methods
Complex or hard environment factors necessitating particular design methods.
Nature and size of the construction and its elements
Small and comparatively simple constructions or building. Insensitive constructions in seismal countries.
Conventional types of constructions with no unnatural hazards
Very big or unusual constructions and constructions affecting unnatural hazard. Very sensitive constructions in seismal countries
Negligible hazard of harm to or from neighboring constructions or services and negligible hazard for life
Possible hazard of harm to neighboring constructions or services due, for illustration, to diggings or stacking
High hazard of harm to neighboring constructions or services
Beginning: Orr and Farrell ( 1999 )
Table 4.1 Geotechnical Categories related to geotechnical jeopardy and exposure degrees
Some of the chief characteristics of each class are summarized below.
Class 1 contains merely little and simple constructions. The cardinal demands of EC7 may be satisfied merely on the qualitative and experience geotechnical probes. There is a negligible hazard for life and belongings. The design of constructions of this class requires individual with appropriate comparable experience. Some illustrations of constructions of class 1 are constructions with maximal design column burden 250 kN and maximal design wall burden of 100 kN, retaining walls and digging which does non transcend the 2 m and little diggings for pipes and drainage ( Orr and Farrell, 1999 ) .
Class 2 contains foundations and types of constructions with no unnatural hazard or loading conditions, or unusual hard land. The cardinal demands are satisfied utilizing quantitative geotechnical informations and analysis. The design of constructions of this class requires a qualified individual with appropriate geotechnical experience and cognition, usually a civil applied scientist. Category 2 utilizations everyday processs for research lab and field trials, for design and building. Examples of constructions for this class are considered the heap and spread foundations, the walls, the retaining constructions, the embankments and earthworks, the tunnels, the land ground tackles, etc ( Orr and Farrell, 1999 ) .
Class 3 contains constructions that are non included in classs 1 and 2. These constructions can be really big and unusual constructions, exceptionally or remarkably hard constructions or land conditions in extremely seismal country. The design of constructions of this class requires an experient geotechnical specializer like a geotechnical applied scientist. Some illustrations of this class are really big edifices, big Bridgess, tunnels in extremely or soft permeable land, embankments on soft land and deep diggings ( Orr and Farrell, 1999 ) .
4.4.3. Limit State design doctrine
Eurocode 7 is based on the bound province design doctrine. In this bound province design the public presentation of the whole or portion of the construction is described and it is referenced to a set of bound provinces. Beyond these bound states the construction fails to run into its design demands of being sufficiently lasting, holding an undistinguished hazard of fall ining, deforming and jeopardizing life because of some defects ( Orr, 2000 ) .
The bound provinces are divided into two: ultimate and serviceability bound provinces
Ultimate Limit States ( ULS )
Ultimate bound provinces are state of affairss that involve safety such as the danger of people, the prostration of the construction, the economic loss or any other type of failure ( Orr, 2000 ) . The design state of affairs in a ULS computation with low hazard of failure is achieved by utilizing a set of partial safety factors to increase the tonss effects for the ULS design action consequence, Ed, and another one set to diminish the land strength parametric quantities or opposition for the ULS design opposition, Rd. The undermentioned status must be satisfied in order to corroborate that the happening of a ULS is improbable: Ed ? Rd
The chance of happening of ultimate bound provinces is low for good designed constructions ( Orr and Farrell, 1999 )
Serviceability Limit States ( SLS )
Serviceability bound provinces are state of affairss where the construction may non be able to run into its specified demands. The design state of affairs in SLS computation is achieved by utilizing design values of the tonss and dirt distortion belongingss which are equal to the characteristic values. The land distortion belongingss and partial factors on the tonss are equal to 1. Some illustrations of serviceableness bound provinces state of affairss are the distortions, quivers, local harm and colonies of the construction in its normal usage. The chance of happening of serviceableness bound provinces is higher than ultimate bound provinces. The undermentioned status must be satisfied in order to corroborate that the happening of a SLS is improbable: Ed ? Cd
Where Ed is the design value of the action consequence and Cd is the restricting value of the distortion of the construction in a serviceableness bound province ( Orr and Farrell, 1999 ) .
The bound province design doctrine adopted in Eurocode 7 is of import to geotechnical design because it refers in all possible types of failure and it verifies that no relevant bound province is exceeded for each design state of affairs. Harmonizing to Eurocode 1, the state of affairss in which a construction fulfills its maps are the design state of affairss. These state of affairss may be transeunt, relentless or inadvertent. The transeunt state of affairss happen in a period shorter than the life of construction and their chance of happening is high. The relentless state of affairss happen during the working life of the construction and are state of affairss of normal usage. Last, the inadvertent state of affairss are exceeding instances such as fire, detonation, etc ( Orr and Farrell, 1999 ) .
The above two cheques are used to guarantee that the hazard of failure by serviceableness or ultimate bound province is adequately low for each type of design state of affairs.
4.4.4. Four ways of transporting out geotechnical design
Eurocode 7 adopts four design attacks as follows:
Use of computations
This attack is the most common in geotechnical design. Eurocode 7 requires that this method shall explicate the behaviour of the land for the bound province. This is the ground why different and separate computations should be used in the cheque of ultimate and serviceability bound provinces. The ultimate bound provinces computations involve analysis of a mechanism utilizing land strength belongingss and the serviceableness bound provinces computations involve analysis of distortion, land stiffness and squeezability belongingss. Design utilizing computations shall be used in concurrence with partial factors to do certain that the hazard of failure, either for ultimate bound province or for serviceableness bound province, is low. Imposed tonss, supplantings, belongingss of dirt, stone or other stuffs, geometrical informations, partial factors or other safety elements, computations theoretical accounts, values of distortions, quivers, cleft breadths are the basic constituents of a geotechnical design computation ( Eurocode 7-pat1, 2004 ) .
Adoption of normative steps
This design attack involves conventional and more general conservative regulations. It besides gives attending to workmanship, care and protection processs, and control and specification of stuffs. Adoption of normative steps in design is used when the design by computations is non necessary, or to guarantee lastingness against biological or chemical onslaught and hoar action ( Eurocode 7-part1, 2004 ) .
Use of experimental theoretical accounts and burden trials
In this attack the undermentioned characteristics must be allowed for and considered: The differences between the existent building and trial in the land conditions, the clip effects and the scale effects. Sometimes the trials are carried out on a full or smaller graduated table theoretical accounts, or on a sample of existent building ( Eurocode 7-part1, 2004 ) .
Use of an experimental method
The experimental method is used when the geotechnical behaviour is hard to foretell. In this attack the design is reviewed throughout the building. Before the building is started the acceptable bounds of behaviour must be established, the possible behaviours must be assessed, and a program of monitoring must be prepared to look into if the existent behaviour is within the acceptable bounds ( Eurocode 7-part1, 2004 ) .
The attacks are selected based on the experience. Sometimes merely one attack is used in a design, but in other instances these attacks can be used in a combination. One simple illustration is the design of heap ; the heap opposition can be determined from burden trials and the design of pile foundations can utilize computations with the value of pile opposition. It is recommended to utilize more than one attack and experience, particularly in local conditions and similar designs ( Orr and Farrell, 1999 ) .
4.4.5 Characteristic Valuess and Partial Factors
Before the initiation of Eurocode 7, geotechnical design used the traditional methods based on overall safety factors and non on the bound provinces ( Orr, 2000 ) .
As mentioned above, Eurocode 7 is based on bound provinces which require the usage of characteristic values of land belongingss and partial factors to land belongingss and tonss and sometimes to the geometry of design to accomplish the needed safety. Kavvadas, 2007, said: ‘The characteristic values consist of ‘preservative assessments ‘ which normally do non differ from the recent ‘understandable assessments ‘ . Orr ( 2000 ) said: ‘The characteristic values of a land belongings are a cautious estimation of the value impacting the happening of the bound province ‘ .
The characteristic values of actions must be calculated harmonizing to the EN 1990: 2002 and EN 1991.The characteristic values of lasting actions ( Gk ) are calculated from the nominal unit weight of stuffs including H2O force per unit areas. The characteristic Earth force per unit areas use characteristic land belongingss, surface burden and characteristic H2O force per unit areas. The characteristic values of variable actions ( Qk ) are specified values or values taken from meteoric records ( Eurocode 7-part1, 2004 ) .
The characteristic value of a land belongings is defined as an estimation of the value that affects the happening of bound province ( average value over the relevant volume of land ) . The characteristic values of geotechnical parametric quantities are calculated from the derived values and the consequences of field trials and research lab. Derived values are values of land parametric quantities obtained by empiricist philosophy or correlativity from measured consequences and theory ( Orr and Farrell, 1999 ) . Measured consequences are values obtained by trials. Eurocode 1-part 1 ( 2004 ) requires that these values should take into history the followers:
The geological information and other background informations from old undertakings
The variableness of the mensural belongings values
The research lab and field probe
The figure and type of samples
The ability of the construction to reassign tonss from weak zones to strong zones in the land ( Eurocode 7-part1, 2004 )
The characteristic values and partial factors are used to the bound province method to cipher the design values of stuff belongingss, geometrical informations and tonss ( Orr, 2000 ) . Design values are values that are used in design computations ( Orr and Farrell, 1999 ) . The design value of burden ( Fd ) is calculated utilizing the characteristic value ( Fk ) and the partial burden factor ( ? ) with the equation: Fd= ? Fk. The design value for stuff belongingss ( Xd ) is calculated utilizing the characteristic value ( Xk ) and the partial burden factor ( ? ) with the equation: Xd= Xk / ? ( Eurocode 7-part 1, 2004 ) .
4.4.6. Three different attacks to restrict province design
Eurocode 7 introduced three design instances ( Cases A, B and C ) in geotechnical design to guarantee that the hazard of failure in the construction and land is low for different combinations of land belongingss and tonss. Eurocode 7 requires that the designs shall fulfill all the three instances. The three design instances are described below:
It deals with uncertainnesss in favourable lasting actions and unfavourable variable actions in instances where the strengths of the land and construction are undistinguished. The purpose of this instance is to protect the geotechnical size and structural design from the jobs, particularly from the gross supplanting like hydraulic failure, overturning of constructions, perkiness, etc. It is besides related with state of affairss in which the equilibrium depends foremost on the weight and so on the dirt strength and in which the chief tonss are frequently hydraulic forces ( Orr and Farrell, 1999 ) .
It deals with uncertainnesss in actions. The partial factors on actions are greater than 1 as the land belongingss are non factored. The purpose of this instance is to protect the geotechnical size and structural design from the characteristic values of the unfavourable divergences of the actions. These values are equal to the land belongingss. Case B besides deals with the structural design of foundations and retaining walls but it does non cover with the structural strength of an component like incline design ( Orr and Farrell, 1999 ) .
It deals with uncertainnesss in stuff belongingss. The partial factors on land belongingss are greater than 1. The purpose of this instance is to protect the geotechnical size and structural design from the characteristic values of unfavourable divergences of the oppositions or land belongingss. In this instance the characteristic values are equal to the lasting actions. The variable actions are increased but they are smaller than characteristic values in instance B. This instance besides deals with the finding of size of land ‘s elements like the size of foundations, the deepness of retaining walls, etc. Furthermore it is related to state of affairss where the strength of land is involved like incline stableness jobs ( Orr and Farrell, 1999 ) .
Eurocode 7 requires the presentation of a Geotechnical Design Report ( GDR ) after the design. This study presents the design computations, the design consequences, the informations used, the premises made and the consequences of the confirmation of serviceableness and safety ( Eurocode 7-part1, 2004 ) . The degree of inside informations of the GDR depends from the type and the complexness of the design. It normally contains the undermentioned descriptions of:
The site and milieus
The tonss and the modification motions
The statements on the criterions and codifications applied
The statements on the acceptable degree of hazard
The geotechnical design drawings and computations
The points that must be checked throughout the building of a construction, the care or the monitoring of the construction ( Orr and Farrell, 1999 ) .
4.4.8. Geotechnical probes and geotechnical informations
Section 3 of Eurocode 7 gives the general demands for puting up geotechnical probes and roll uping geotechnical informations necessary for design. These demands provide a dependable appraisal of the characteristic values of the land parametric quantities and an appropriate description of the land belongingss. All the information collected from the geotechnical probe, including the parametric quantity values from the research lab trials and field, and groundwater and geological conditions, are presented in a Ground Investigation Report ( GIR ) . 6
Eurocode 7 requires that geotechnical probes shall give all the necessary informations. It shall give all the informations about the groundwater conditions and land at and around the building site ( Orr and Farrell, 1999 ) . These informations aid to a dependable appraisal of the characteristic values of the land parametric quantities and to an appropriate description of the land belongingss. It besides requires that geotechnical information shall include the history, morphology, hydrology, geology and seismicity of the site and shall be collected and recorded really carefully. Furthermore this codification requires the consideration of the variableness of the land. The public presentation and building demands of the construction are compulsory in the geotechnical probes. It besides requires that the geotechnical probes shall be reviewed when there is new information as the geotechnical class is possible to alter. 6
Harmonizing to Eurocode 7, geotechnical probes should be carried out in three stages ; preliminary, design and control probes. Preliminary probes include walkover studies, desk survey of land conditions, boreholes, investigations and spots to acquire sufficient information. They are carried out in the planning phase. Design probes include laboratory and field trials supplying all the necessary information about the design of lasting and impermanent plants and placing troubles during the building. Finally, the control probes are carried out during the building phase and required to look into the existent land conditions, proctor and maintain.6
When be aftering field trials Eurocode 7 include demands for the equipment, transporting out the trials, coverage and construing the consequences and obtaining the derived values. .6
To place and sort dirts, Eurocode 7 requires that the samples shall be taken from every separate bed that influences the behaviour of the construction and for organic dirts from at least every 1 m in one drilling ( Orr and Farrell, 1999 ) . 6
When be aftering research lab trials Eurocode 7 include demands for the manner the specimens ( parts of stone or dirt samples used in research lab trials ) are prepared, the proving equipment, the coverage of the consequences, the rating of the consequences, the testing processs, the research lab proving programme and the obtaining of derived values. When the research lab proving programme is carried out, codification requires that the stratigraphy, the dirt type, the geotechnical facets and the type of construction shall be taken into history. It besides requires that all dirt samples should be checked before any research lab test.6
Harmonizing to Eurocode the consequences of the geotechnical probes shall be recorded in a Ground Investigation Report ( GIR ) . All the geotechnical information, the derived values and the rating of the information shall recorded in the GIR. This study besides underlies the Geotechnical Design Report ( GDR ) , contains all the field and research lab plants and all the trial methods used. 6
4.5. Deduction of Eurocode 7 for pattern in UK
The execution of Eurocode 7 in UK faces some jobs. The design computations contain many beginnings of uncertainness in actions, stuffs strengths, opposition of structural subdivisions, derivation of action effects, etc ( Driscoll and Simpson, 2001 ) . A error in computations can be unanticipated in ulterior phases.
4.6. Drumhead
The chief aim of this chapter is to explicate the alterations that Eurocode 7 causes to Geotechnical Design. It refers to the cardinal design demands that must be satisfied by all the constructions, to the bound province design doctrine, to the usage of characteristic values and partial factors, to the usage of three design attacks and three geotechnical classs. It besides explains the four ways of transporting out the geotechnical design and the necessity of geotechnical design study. Furthermore it briefly refers in the history of Eurocode 7, in its range and construction.
Mr Ian pls ignore these mentions. It is non the concluding construction.