Foundation Problems On Siltstones: A Case Study From Geotechnical Investigation In Southern Part Of Tirana Area

Abstract

This paper shows the results of the geotechnical investigation carried out in southern part of Tirana city, Albania for study a large foundation on which is planned to build the bigger supermarket. Based on duty of the designers a lot of boreholes were drilled, as well as many in situ and laboratory tests were done in construction site. The aim of this study was to make a detail description of lithology, morphology, geodynamics phenomena, hydrogeology, as well as determination of the physical and mechanical properties of soils and rocks in the study area. So, 21 boreholes in the construction site were drilled from 10.0m up to 15.0m deep. Standard Penetration Tests (SPT), soils grain size distribution, bulk density, Atterberg's limits, moisture content, specific density, shear strength, oedometer and uniaxial compressive strength tests were done for the soils and rocks in this area. PH, chloride and sulphate content were determined for soils and ground water samples. From fields and laboratories works ensue the behavior and properties of soils and rocks depend on their compositional characteristics, formation processes and environmental conditions during their geological history. The soils physical-mechanical properties have low to medium values, the underground water table varies from 4.5m to 6.0m below of earth surface. Whereas, in the central part of construction site on rocks basement-siltstones rocks is found a buried groove, which means that siltstones rocks weathering crust process is much developed than other parts of studied area. Since the engineering object has a large foundation was absolutely necessary to improve the geotechnical properties of the basement against differential settlements of engineering object. Therefore, for the improvement of the foundation was excavated a ditch 2.0m deep below of foundation level from east to west for drainage purpose. Also, to avoid the differential settlements of engineering object was used the slab foundation type. In the end of this work we have given conclusions and recommendations for the final constructions design.