Geotechnical Engineering

Transcription

1 Geotechnical Engineering

2 Geotechnical Engineering in COWI COWI is an international market leader in Bridges, Marine and Foundation Engineering, not least because of successful interplay between the various disciplines. For a very wide range of projects and structures the Geotechnical Group provides in-house support in all phases of projects. This ensures state-of-the-art foundation solutions and the capability to perform stand-alone geotechnical services. COWI employ more than 60 geotechnical engineers, ranging from internationally recognised experts to young professionals, in the COWI Group offices in Denmark and at the COWI subsidiaries worldwide. COWI has a total of more than 3300 employees, the main part engineers. COWI operates around the world, and has subsidiaries and project offices in several countries. The turnover amounted to 300 million EURO in Quality Quality is a key issue in all our projects. We operate a Quality Management System which is certified within the requirements of ISO This assures our clients of professional management on all our projects. Quality Management System Certificate and Certification Conditions. The Geotechnical Group mainly provides services in the following subjects Geotechnical investigations Site investigations Laboratory investigations Material prospecting Geological modelling Geotechnical design Underground Engineering Earth retaining structures Groundwater control Shallow and deep foundation Earth structure Soil reinforcement Soil structure interaction Numerical modelling Physical modelling Preparation of tender documents Rehabilitation/maintenance Feasibility studies Geotechnical supervision

3 Data Management 3 Data Managing When working on jobs that involve geological, geotechnical, geoenvironmental or monitoring data, COWI has a range of tools that can be used to manage, query and present such information. These tools are used routinely on all jobs and are an integrated part of our service. Domestic Market To complement COWI s drilling rigs and our general understanding of the regional geology, a large database is maintained with geological, geotechnical, geophysical, environmental and hydrogeological data. The database is maintained using GeoGIS on all projects. The data have been used to establish and maintain a geological model for parts of Zealand. The model and the database are then used by HoleBASE and KeyHOLE to create contour maps, sections, volume calculations etc. HoleBASE and KeyHOLE are software used extensively worldwide. International Market COWI has developed a high expertise for handling large amounts of geotechnical, geoenvironmental and survey data that are to be reviewed quickly to produce an interpretative report with meaningful enclosures and drawings. Such data processing is possible using tools like HoleBASE and KeyHOLE that are based on the internationally recognised data exchange format AGS. COWI has developed expertise with other geotechnical data management systems such as gint and GEODASY, in order to ensure correct application of contractor s data in AGS format. It is therefore a standard procedure that qualified staff works closely together with the contractor in the beginning of a project to ensure the higest possible quality of data.

4 4 Site investigations Offshore investigation in Qatar. It is a well known fact that the client often pays for the investigations not carried out. The expenses just show up later in the building process. COWI strives to show due dilligence in organising and conducting site investigations of the quality and extent to minimise cost and risk for the client. COWI carry out site investigations with our own drilling rigs. COWI operates 7 large drilling rigs and 4 small rigs to perform geotechnical and environmental boreholes. The fieldwork is mainly carried out in Denmark. Two of the large rigs are fitted with CPT equipment. Furthermore we have equipment at our disposal to perform static plate load test, light dynamic plate load test and compaction test using Troxler (for example). In connection with our many projects abroad, our engineers have great experience in planning geotechnical investigations for large projects, preparation of tender documents, negotiations with drilling contractors and subsequent supervision. All investigations are presented in a geotechnical report. The reports are often divided into a factual report and an interpretative report. COWI has both Danish and British programs to perform and present borehole logs. The British program, HoleBASE, is used on all our international projects. Mudcrawler used in Kuwait. Offshore investigation in Qatar.

5 Laboratory Testing 5 COWI carries out all types of laboratory testing using nominated or site specific laboratories. Classification tests may be carried out in the three in-house laboratories in Denmark. The tests are carried out according to the standard required by the client. COWI s geotechnical engineers have experience with a wide range of soil and rock types and programme, supervise and evaluate the test results according to the clients needs. COWI is familiar with and has used a number of dedicated, advanced test facilities around the world ensuring state-of-the-art testing if required for the project. Examples are: stress path triaxial testing on very soft clay, centrifugal testing of dolphins for ship protection, high pressure triaxial testing of limestone including temperature related creep, triaxial testing of highly weathered Granodiorite. The following test are performed in-house Soil and rock description Moisture content Bulk and dry density Sieve analysis Hydrometer test Atterberg limits Compaction test Linear shrinkage Free swell Specific gravity Sand equivalent Capillarity Organic matter Calcium content Sulphate content Consolidation test Unconfined Compression Strength Brazil test Point load test

6 6 Underground Engineering COWI handles all aspects concerning underground engineering and has great experience in the design of building pits. Underground construction works for design and build contracts present technical and logistical challenges. Due to the intrinsic uncertainties of soil and rock behaviour, it is important to consider several alternative construction systems and methods. COWI can provide a flexible design approach in which, by assessment of more alternatives, the optimal solution is obtained. This involves cost, safety, reliability and environmental impact, and if possible optimisation of the Contractor s available equipment. For excavations and tunnelling in urban areas, an essential requirement is to prevent damage to adjacent structures and services. Settlements associated with excavations are generally determined by three factors: excavation and support systems method of construction groundwater control To find the best design for underground structures including temporary support etc., advanced modelling of soil-structure interaction must be performed. COWI has extensive experience gained from the use of modelling on several major infrastructure projects. Advanced FEM-programmes such as PLAXIS, ABAQUS and FLAC are used to provide safe and cost effective solutions. Assessment of geotechnical soil properties and re-use of excavated material are carried out by COWI s geotechnical engineers. By collaboration with our department for Soil and Groundwater Contamination a professional handling of a potential contamination is ensured. These issues are invariably interlinked. For example, an earth retaining structure that secures adjacent buildings from damage due to settlement can also be used to limit groundwater drawdown - if necessary, in combination with injection of grouts and groundwater recharge. Construction pit in Copenhagen, Denmark.

7 Groundwater Control 7 The proper control of groundwater is an important part of excavations, from both the perspective of stability and external environmental effects. COWI has extensive in-house expertise in all aspects of groundwater control, especially in areas where authorities have strict requirements for the protection of existing buildings and water resources. In COWI, groundwater control is integrated in construction plans from the earliest stages of a project in order to provide a sound basis for designing cost-optimal solutions. Monitoring and modelling are used for planning and management of ground water systems. Based on our experience from large infrastructure projects, COWI offers expertise within groundwater monitoring, development and maintenance of databases, flow simulations as well as handling of interfaces between the client, authorities and third parties. Flintholm Station, Copenhagen, Denmark. Construction pit for underground railway in Copenhagen, Denmark.

8 8 Numerical Modelling Contour plots from PLAXIS Contour plot of displacement field for existing block quay wall, as a result of dredging in front of the wall. Contour plot of shear strain (J2 strain invariant) for block quay wall, revealing potential rupture figure. Numerical modelling is a concept for approximating real behaviour. It is a popular means for solving civil engineering problems when exact closed form solutions do not exist. This is often the case in foundation engineering, when problem solving requires the use of continuum mechanics and involves effects of soil-structure interaction, 3-D, plasticity, hydraulic loads, seepage forces, etc. Examples are shown in the following adjacent figures. Foundation Engineering is generally concerned with predicting the behaviour of natural or man-made structures on, or in, the ground. The problem generally is to predict fields of displacements, strains and stresses, both within the ground and the founding structure. Displaced mesh for ultimate horizontal loading (ship impact) on piled bridge pier. Contour plot of shear strain (J2 strain invariant) for double sheet pile wall cofferdam. Limit equilibrium Methods For the purpose of solely investigating the safety of any given structure against any loading, limit equilibrium methods will often suffice. COWI uses several software packages for limit equilibrium analyses, a.o.: Programmes SPOOKS, Qwalls and ReWard, for the design of sheet pile walls and their anchorages Programme Geo Studio 2004 for the stability of soil and rock slopes, dams, breakwaters etc., including possible seepage forces.

9 9 Soil Structure Interaction COWI s geotechnical specialists have extensive experience and knowledge in soil structure interaction. In projects like the Great Belt Link, the Øresund Link and the Metro in Copenhagen COWI made extensive use of advanced computational methods in analysis of foundation bearing capacity and stability as well as for prediction of movements related to deep excavations and tunnelling. All of the mentioned software packages and more (not listed) are regularly used by the Geotechnical Group. The Group has considerable expertise in assessing soil/rock properties from field investigations, lab. tests and monitoring data for real structure behaviour, all of which are essentials for setting up realistic input data for the software packages. For truly 3-D continuum problems and complex material behaviour, the Geotechnical Group also use sophisticated software packages such as the general purpose FE programme ABAQUS. COWI uses a suite of software packages for displacement type analyses Program PLAXIS is a user friendly and dedicated geotechnical FE program, handling soil, water, structures, soilstructure interaction, material elasticity and plasticity, construction stages, etc. PLAXIS is a popular tool for continuum analysis and prediction of the behaviour of any given structure on, or in, any given soil or rock profile COWI has developed an advanced FE programme to handle pile groups. The programme is a module to our well known IBDAS (Integrated Bridge Design Analysis System). It can handle all types of piles, including large diameter drilled shafts. The programme can handle both axial and lateral influence Program SAP2000, a structural finite element program, particularly suited to dynamic analyses, e.g. considering earthquake loads, push-over analyses etc. Program LPILE for the analysis and prediction of the behaviour of a single laterally loaded pile Program GROUP for the analysis of the behaviour of axialy and lateraly loaded pile groups Programme SHAFT for the study of drilled shafts under axial loads Program MPILE for the analysis and prediction of the behaviour of generally loaded pile groups, with several more or less sophisticated options for considering pile-soil-pile interaction (group effects) Program PIGLET for the analysis and prediction of the behaviour of generally loaded pile groups, considering linear elasticity only and group effects

10 10 Shallow and deep foundations In competent soils shallow foundations are often the most economical foundation solution. With proper soil characterisation and derivation of soil design parameters COWI applies state-of-the-art design methods combined with numerical and physical modelling to provide cost effective and safe solutions. Often the project area is not blessed with competent soil condition for shallow foundations, then deep foundations are the solution. COWI s very experienced staff have been involved in all types of deep foundation from traditional driven or bored piles to very innovative foundation solutions for large bridge projects. Many of the challenges met are from a combination of excessive amounts of very soft deposits, extreme water depths, strong current and excessive environmental loading, notably earthquake and ship collision forces. Permanent Ground Anchors for Uplift Construction of deep basements below the ground water level often cause the requirements for permanent ground anchors. COWI has great experience in the design and supervision of ground anchors. In Copenhagen the ground anchors are most often fixed into the Copenhagen Limestone. Elsewhere in Denmark anchors are mainly fixed in glacial sand or clay. Flintholm Station, Copenhagen, Denmark.

11 Earth Structures 11 Dredging and Reclamation COWI has been involved in several large dredging and reclamation projects notably in the Middle East. Our geotechnical specialist has been in charge of planning and supervision of the site investigations. Furthermore, we are involved in the design and preparation of technical specifications for all the dredging and reclamation aspects including edge treatment (costal protection structures). In these projects we are in close cooperation with the large international dredging companies. Soil improvement / reinforcement For a number of very different types of structures COWI has designed soil improvement or reinforcement schemes to reduce settlements, increase strength and to provide robustness for environmental loadings, such as earth quakes. During the construction of the Danish METRO in Copenhagen, grouting was extensively used as a ground water control measure in order to reduce the permeability of Copenhagen limestone. Additional improvement of subgrade and pavement materials projects has been carried out using lime or cement stabilisation. Dams, dikes and slope stability COWI has assisted clients in locating feasible dam sites, performing feasibility studies to determine the most feasible dam heights, performing soil investigations to locate materials and geotechnical and hydro-geological investigations at dam sites. The stability of existing slopes is analysed, when the stability seems insufficient or new loads are added at the top of the slope. Pearl of the Gulf Marina, Qatar. +10 Bunds 0 Quarry Run Sand fill - 10 Stone columns Plastic drains m Kuwait group sand

12 12 Bridge Projects COWI is an international market leader in bridge engineering. COWI is recognised worldwide for our state-of-the-art knowledge. In Denmark and around the world COWI has been in charge of the design and supervision of the world s largest cable stayed and suspension bridges. These projects include all the geotechnical aspects, from preliminary evaluation of the soil condition to site investigations, handling of data, design and supervision. Furthermore we have carried out site investigations and design for a large number of highway bridges in Denmark and abroad. Model of Sheikh Jaber Al Ahmed Al Sabah Causeway, Kuwait. Sutong Bridge, China. Load test of ø800 mm drilled shaft.

13 Tunnel Projects 13 COWI has been involved in tunnel projects all over the world. Our experience covers all types of tunnels, including bored tunnels, immersed tunnels, cut&cover tunnels, rock and NATM tunnels. The success of tunnel projects relies heavily on the understanding and handling of complex soil-structure interaction problems. The in-house cooperation between geotechnical engineers and tunnel specialists ensures that COWI can provide state-of-the-art consultancy in all phases of tunnel projects worldwide. Tunnel projects include many different geotechnical issues. The geological model must be well established for all types of tunnels. Focus on settlements, properties of rock/limestone and design of backfill/locking fill around an immersed tunnel is required. Recently COWI has been responsible for the design of the world s deepest immersed tunnel in South Korea, constructed almost 50 m below sea level on soft (reinforced) clay and an up to 20 m high sub sea embankment. In such projects we benefit from our finite element programmes to evaluate the soil-structure interaction. Model of Busan-Geoje Fixed Link, South Korea. Geoje Jeo Jungjuk Gaduk 120m 80m Daejuk 40m 0m -40m Cross Section of Busan-Geoje Fixed Link, South Korea.

14 14 Metro and Station Projects Photo: Aerodan Flintholm Station, Denmark. Copenhagen Metro, Denmark As part of the multidisciplinary services in large infrastructure projects COWI plans, designs and supervises all aspects of metro and station projects. Metro and station projects involve all kinds of geotechnical issues depending on the project layout. Deep excavated stations often comprise geotechnical challenges similar to tunnel projects. Other projects comprise sheet pile walls, piles, ground anchors, shallow foundation etc. Furthermore, groundwater lowering is often needed during the construction phase. Flintholm Station, Denmark Detailed design and supervision of the third largest railway station in Denmark, constructed in connection with the new Metro. Included detailed design, a large quantity of sheet pile walls, large plate load tests and supervision.

15 15 Photo: Adam Mørk

16 16 Building Projects Photomontage: Lundgaard & Trandberg Arkitekter Model of New Playhouse in Copenhagen harbour. COWI also has a large building construction department. In close cooperation between the construction engineers and geotechnical engineers, COWI ensures the best foundation solutions for smaller and larger buildings. In Denmark, shallow foundations on late glacial or glacial deposits or foundations on driven piles are most common. In addition temporary sheet pile walls or other types of supporting systems are required when building deep basements in urban districts. Again in these projects, we often perform the geotechnical investigations and establish the geotechnical data for the design and are involved in the supervision and the design phase.

17 Harbour and Marine Projects 17 COWI is an international market leader in marine and coastal engineering and offers a comprehensive range of consulting sevices for all aspects of projects related to ports, harbours, coastal and marine structures. When developing integrated design solutions to marine projects, COWI draws upon our in-house expertise in e.g. geotechnical engineering. COWI s marine and geotechnical engineers are integrated in the same department to obtain the best solutions and to have a common understanding for the final design. Rehabilitation of Tuborg Harbour, Copenhagen, Denmark. Detailed design and supervision of a new exclusive harbour in Copenhagen. The project included new sheet pile walls, a bridge, canals, breakwaters, dredging etc. Idku LNG Terminal, Egypt. Elsinore Harbour, Denmark.

18 18 Road and Airport Projects The Geotechnical Engineering Group are often involved in road and airport projects. Our services range from the site investigation, soils and materials investigations, design and supervision. We are involved in all geotechnical aspects for the pavement, earth work, crossing bridges, tunnels, slopes etc. Road project in Ethiopia. Extension of motorway passing a soft spot. Extension of motorway M3 in Denmark. Sofia Airport in Bulgaria.

19 Geotechnical Supervision 19 Harbour in Durres, Albania. Road projects in Tanzania. Among our many geotechnical engineers, we have at our disposal several engineers with comprehensive experience in geotechnical supervision. Our staff have supervised the construction of large scale foundation, briges, roads, railways, harbours and dams including off- and onshore geotechnical investigations. The supervision is undertaken both in Denmark and overseas. Several of our staff in the geotechnical group have long-term overseas supervision experience, always supported by our senior geotechnical engineers providing home office support. Furthermore all our staff are regularly involved in supervision on danish projects ranging from small buildings to major bridges performing the geotechnical control of the excavations or approval of pile driving records.

20 COWI Group Main Office COWI offices. Geotechnical Engineering - more than just a hole in the ground. COWI A/S Parallelvej 2 DK-2800 Kongens Lyngby Denmark Tel.: Fax: cowi@cowi.com Internet: Contact Michael Bindseil Head of Department, Marine & Foundation Engineering mhb@cowi.com Jørgen S. Steenfelt, Prof. Head of Development, Marine & Foundation Engineering jos@cowi.com Torben Bang Section Manager Geotechnical Engineering tba@cowi.dk e-06a Printed in Denmark by Kailow