Third International Conference on Geotechnique, Construction Materials and Environment, Nagoya, Japan, Nov. 13-15, 2013, ISBN: 978-4-9905958-2-1 C3051 1 CATEGORISING GEOTECHNICAL PROPERTIES OF SUBSOIL IN SURFERS PARADISE USING GEOGRAPHIC INFORMATION SYSTEM (GIS) Haider Al-Ani 1 , Leila Eslami-Andargoli 2 , Erwin Oh 1 , and Gary Chai 3 1 School of Engineering, Griffith University, Australia 2 School of Environment, Griffith University, Australia 3 Centre for Infrastructure and Engineering Management, Griffith University, Australia ABSTRACT Peat is a highly organic and compressible soil. Surfers Paradise (as a study area) has problematic peat layer which has different thickness at different locations between R.L. -10 to -19.6 m below the ground surface. Buildings in Surfers Paradise are using piled foundations to avoid the high compressibility and low shear strength peat layer. In this paper, geotechnical borelogs are compiled from 51 sites in the study area. These borelogs data are then imported into ArcGIS10 as digital layers and converted into assessable formats by Geographic Information System (GIS). This technique has been utilised to produce digital zonation maps for the study area. The application of interpolation techniques allows the production of zonation maps and bring together years of geotechnical data. Standard Penetration Test (SPT) N values have been selected to determine the soil stiffness in the study area. These SPT-N values are then categorised to produce different zonation maps. The occurrence of peat layers can be located using these zonation maps. These GIS-based zonation maps will provide a better overview of subsurface geology, bed rock elevations, and geotechnical properties of the various soil types found in the study area. Keywords: Peat, Geographic Information System, Standard Penetration Test, Spatial Analyst. INTRODUCTION GIS has the capability to manage, store, and referencing geotechnical data to its geographic locations. It has been used to integrate existing data such as soil investigations aided by geographic coordinates with specific project data to identify potential geotechnical challenges. For instance, a case study has been presented by [1] where a geotechnical investigation data has been managed by using GIS for design purposes in transportation projects. The outcome of this study was an early identification of the geotechnical problems which require an additional budget and time consuming design’s substantial changes. It is generally accepted that the organic matter presence in soils causes a detriment of their geotechnical and engineering qualities [2]. Peats and organic clays cause typical geotechnical problems as a result of their characteristics such as compressibility, lightness, creep ability, weatherability, and low strength and stiffness [3]. GIS Application in Geotechnical data GIS has been used in many geotechnical applications ubiquitously over the world. For example, in Brazil, GIS used for geotechnical and environmental risk management of Brazilian oil pipeline in 2010 [4]. In addition, in Greece, GIS has been used to produce a thematic map for the geotechnical, geological, seismological, and geomorphological data of Athens [5]. In Turkey, reference [6] has used GIS to produce zonation maps and to estimate if a further precaution is required for a safer area. Cross sections which include SPT-N blow count with depth have been performed to determine the soil strength. Further, GIS-based geotechnical information systems have been established in the USA, Singapore, Brazil, and Japan in 2003, 2005, 2003, and 2010 respectively. The purpose of this is a web-based easy access to the geotechnical data of any area of interest to have an idea about geotechnical conditions of this area. In addition, four case studies of small scale geotechnical projects have been studied by [7] to verify the benefits of using GIS in geotechnical engineering in The United Kingdom. The outcome of this study indicated that GIS output improved the analytical and technical range of these projects in comparison with traditional techniques and the high quality produced maps are comprehensible and popular with engineers. This paper shows the identification of peat layer occurrence in Surfers Paradise as a case study in Australia. The occurrence of peat has been identified by producing the interpolated SPT-N value zonation maps by using the Spatial Analyst extension and interpolation