Probable Causes of Cracks on selected Buildings at Akrowa in Afigya Kwabre District, Ghana

George M. Tetteh; Agnes T. Atakora

Abstract

This work evaluated the nature of the foundation soils and cracks on twelve representative buildings at Akrowa, in the Afigya Kwabre District near Kumasi in Ghana. Age, material used whether clay/concrete, dimensions of cracks on the buildings and tests for geotechnical parameters of foundation soils such as moisture content, bulk density, specific gravity, particle size distribution, Atterberg limit and direct shear were carried out on soils from four pits dug at different locations in the area. The soils were classified generally as well-graded gravelly sand containing little silt and clay of low plasticity with ultimate bearing capacity range between 922.60 kN/m2 to 1258.10 kN/m2 as 93.4% >50% of particles retained on No. 200 or 0.75µm sieve, Cu of 10.3 > 6 and mean Cc of 2.6 which falls within the range 1< Cc < 3 (ASTM 2487-98), The net safe (allowable) bearing capacity ranges between 296.74 kN/m2 to 409.75 kN/m2 and pH ranges from 5.24 to 7.63. Low plasticity index of soils in the area indicates stiff and permeable soils underlying buildings on rocks of the basin granitoid. The waterways or streams in the District and its environs joining the River Offin strike mainly to NE or SW in a dendritic pattern. Cracks on the buildings strike mainly north-west while veins in rocks generally strike to north-north east as streams in the area which possibly follow early fractures. The disparity in these orientations may also be due to reflection of deep weak zones in the rocks as they approach the surface. Though rock quarrying near neighboring communities could generate weak ground vibrations that could cause liquefaction and densification processes to affect buildings, these require further study

Abstract

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