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Downloaded from the Online Library of the International Society for Soil Mechanics and Geotechnical Engineering (ISSMGE) INTERNATIONAL SOCIETY FOR SOIL MECHANICS AND GEOTECHNICAL ENGINEERING This paper was downloaded from the Online Library of the International Society for Soil Mechanics and Geotechnical Engineering (ISSMGE). The library is available here: https://www.issmge.org/publications/online-library This is an open-access database that archives thousands of papers published under the Auspices of the ISSMGE and maintained by the Innovation and Development Committee of ISSMGE. Large in-situ tests to investigate the performance of compacted clay Des essais in situ en oedomètre à grande échelle sur l'argile compacte non saturée pour étudier sa performance Yasser El-Mossallamy Department of Civil Engineering, Ain Shams University, Egypt & Arcadis, [email protected] Gerhard Schulz & Otto Heeres Arcadis, www.arcadis.com Salih Aksoy GEOMED, Geoteknik Müş. Etüt, Den. ve Tic. A.Ş., Turkey ABSTRACT: Istanbul New Airport will be located at 40km north of Istanbul, direct at the Black Sea coast. The area is a former open-cast coal mining area. The total area of the project location is about 75.94km2 (7594ha). With a capacity of up to 150mln passengers annually it will be one of the largest airports in the world. The Earthwork is divided into cut and fill areas. In the fill area, the embankments reach heights up to 70m. Especially in the northern part of the project area, there are large areas filled with mining spoil (remolded) material due to former mining activities. The spoil material is inhomogeneous and it was deposited without any compaction. The available material for embankment construction is mainly the Danişmen Formation, which consists of low to high plastic clay. Large scale shear box tests are conducted to investigate the mechanical performance of the compacted clay. Large scale oedometer in-situ tests are carried out on the unsaturated compacted clay to study its deformation performance. The chosen constitutive laws and design parameters are adopted according to the test results. Verification was carried out via the implementation surface monitoring of constructed embankments. RÉSUMÉ : Istanbul New Airport sera situé à 40 km au nord d'Istanbul, directement sur la côte de la mer Noire. La région est une ancienne zone de mines à charbon à ciel ouvert. La superficie totale de l'emplacement du projet est d'environ 75,94 km2 (7594 ha). Avec une capacité jusqu'à 150 millions de passagers par an, ce sera l'un des plus grands aéroports du monde. Le travail de terrassement est divisé en zone de coupe et de remplissage. Dans la zone de remplissage, les talus atteignent des hauteurs jusqu'à 70 m. Surtout dans la partie nord de la zone du projet, il y a de grandes surfaces remplies de déchets miniers (remoulés) en raison des anciennes activités minières. Le matériau de dégradation est inhomogène et il a été déposé sans aucun compactage. Le matériau disponible pour la construction de remblais est principalement la formation Danişmen, qui se compose d'argile plastique. Des essais de caisse de cisaillement à grande échelle sont effectués pour étudier les performances mécaniques de l'argile compacte. Des essais in situ en oedomètre à grande échelle sont effectués sur l'argile compacte non saturée pour étudier sa performance. Les lois constitutives choisies et les paramètres de conception sont adoptés en fonction des résultats du test. La vérification a été effectuée par le biais de la surveillance de la mise en œuvre de la surface des digues construites. KEYWORDS: Istanbul New Airport, Danişmen Formation, unsaturated, in situ testing, settlement performance, stability performance 1 INTRODUCTION The challenges for the earthworks are summarized as follows: Great amount of cut in the south and fill in the north Istanbul New Airport will be located at 40km north of Istanbul, direct at Thick existing heterogeneous spoil with poor mechanical properties the Black Sea coast. The total area of the project location is about due to previous open-mining activities. 2 75.94km (7594ha). Since 2013, Phase 1 is under construction, see The presence of landslides at the project area High seismicity of the area Stringent requirements regarding reliability, availability, serviceability and safety with tight time schedule for construction The available material for embankment construction is mainly the Danişmen Formation that is excavated in the southern part, which consists of partially saturated low to high plastic clay (approximately 70% is CL, 30% is CH). According to the AASHTO classification Figure 1. Phase 1 consists of Runway A, Runway B, the terminal and system, this material can be classified as clayey soil (group A-6). Therefore, a testing program was developed for using these materials apron areas and Runway C. to construct the embankment: in-situ compaction trials, large scale oedeometer tests and large scale shear tests. As verification, compaction control tests are performed to check the reached relative compaction during construction. 2 SITE CONDITIONS Due to the previous mining activities, the area of Istanbul New Airport is very heterogeneous. The site topography is strongly affected by the Figure 1 Left: project location. Right: situation in 2013. Blue line: activities of the open-mining. The project area has variable elevations total project, white line: Phase 1. ranging from 150 meters in the South to fewer meters above the sea level in the North. There are stream valleys with alluvial deposits. The The area is a former open-cast coal mining. Due to the topography, the northern and north-eastern part of the site is bounded by the Black Sea site is divided into cut and fill areas. In the fill area, especially in the shoreline. Elevations along the site vary from approximately El. ± 0.0 to northern part of the project area, there are large areas filled with mining +150 meters Several artificial lakes of various sizes and depths have spoil (remolded) material due to former mining activities. The spoil been formed in the spoil area. material is inhomogeneous and it was deposited without any compaction. The embankment height reaches up to a height of 70m. - 583 - Proceedings of the 19th International Conference on Soil Mechanics and Geotechnical Engineering, Seoul 2017 3 GEOLOGY, HYDROLOGY AND SEISMICITY The main geological units at the project site are the Ceylan, Danişmen, Belgrad Formations and mining spoil. The Ceylan formation is composed of sandy-limestone, marl, silty limestone, clayey-limestone, and limestone alternation. The Danişman formation is a dominant unit of the project area and is widely exposed all around the site and located over the Ceylan formation. It is composed of claystone, marl, sandstone alternation with 1-5m thick lignite layers, and sandstone-gravelstone Figure 3 Basic design concept with embankment fill, buffer fill lenses. The units are dipping about 5-10° to the north. and landscaping fill The Belgrad formation locally overlays the Danişman formation and With this combination of sealing and drainage, water infiltration into consists of sandstones, sands and gravels. The spoil consists of a the embankment body is completely avoided. The evaluation of heterogeneous mixture of clays, sands, marls and lignite of Danişmen geotechnical parameters regarding embankment performance is carried formation. out considering this design principle. 5 SETTLEMENT PERFORMANCE CRITERIA Serviceability requirements are given in ICAO Appendix 14. Differential settlements as well as longitudinal and transverse slopes govern the serviceability requirements of different areas (runways, taxiways and aprons). Figure 4 shows the runway roughness criteria to guarantee surface evenness and to avoid water pools on the surface for bump lengths between 0m and 60m. Figure 2 Geology and 3d model Based on the available data, a 3D geotechnical model was created that served as a basis for the earthwork design, see Figure 2. The 3D model contains CPT’s and boreholes data, the lithology, the geological map of the site, groundwater data, the topology before mining operations started, the topology before airport construction started and the 3D masterplan of the airport. Groundwater measurements were performed in 318 open boreholes. Figure 4 ICAO Settlement performance criteria Based on these measurements it is assumed that the groundwater can be found at ground level, or even above (artesian levels). For the Due to the high serviceability requirements, the residual settlements earthworks design and also groundwater modeling an estimation of need to be limited. maximum groundwater levels has been calculated to design an adequate drainage system between the native soil and the embankment. 6 TESTING PROGRAM ON DANIŞMEN CLAY According to the Turkish Ministry of Public Works and Settlement, the The requirements to the Danişmen fill material are beyond the usual due project site is located within the 3rd degree zone corresponding to PGA to huge cut and fill volumes, embankment heights up to about 70m, the levels of 0.2g. A seismic study of the site was performed based on a water sensitivity of Danişmen and due to the seismic conditions. seismic hazard analyses of the site. After estimation of the magnitude of Therefore a testing program was developed as follows: the design earthquake, the design earthquake characteristics at the rock 1. Suitability testing in which grains size distribution, Atterberg limits, outcrops were determined. Next, the epicenter distances for the design Proctor curves, moisture content, volumetric weight and earthquake source
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