Damage to buildings on expansice soils in Kibaha, Tanzania

Abstract

Many buildings have been constructed with little knowledge of the presence and effect of swell-shrink soils in Kibaha, Tanzania. This study points out the presence of potentially expansive soils in the area. It provides a brief summary of field observations of damaged buildings on expansive soils in the case area. It brings together the details of site topography, geology, geotechnical parameters, climatic conditions, ground investigations and laboratory test results. Soils with significantly expansive properties have been identified in the case study. Principally, the geologic setting of the area indicates the presence of expansive clay minerals. The cyclic wetting and drying weathering of the area is significantly linked to the structural damage plaguing buildings on these expansive soils. Subsequently, the laboratory tests show that the soils have liquid limits greater than 50%, plastic limits between 15% and 30% and shrinkage limits less than 17%. The free swells are greater than 100% while the swell pressures of 50kPa are made known in the oedometer tests. X-ray diffraction tests show that the smectite-group minerals of about 50% are present in the soils. Furthermore, the extents and causes of damages on existing buildings are diagnosed in correlation with the swelling potential. Finally, a number of recommendations to address the problems are put forward.Journal of Building and Land Development Vol. 13 (2) 2006: pp. 32-40