GEOTECHNICAL INVESTIGATION INTO CAUSES OF CRACKS IN BUILDING: CASE STUDY OF DEBA, KUMO AND KALTUNGO LGA GOMBE STATE
By
Salisu Ibrahim
NIGERIAN BUILDING AND ROAD RESEARCH INSTITUTE
ABSTRACT
The aim of this study is to investigate the major causes of cracks observed in majority of the buildings in Deba, Kumo and Kaltungo, Gombe state. To achieve this aim, field observation and geotechnical approach were adopted to study the soil properties. Soil samples were collected around the area of some affected buildings for laboratory study. The properties determined were Particle Size Distribution, Natural Moisture Content, Atterberg limits, Specific gravity, Proctor Compaction, and Triaxial Compression tests respectively. The grain size analysis of the tested soil samples indicated that the soil samples in general comprises predominantly of clay sand which are basically clay, silt and sand except for location 5, which is well graded sand. All the six soil samples have percentages of fines greater than 60 % except location 5 (less than 5%). This indicates that the influence of fine content (clay and silt) is significant on the soil’s engineering properties. Total fine content (Clay and Silt) sizes ranges between 50 – 80 %, Sand component 15 – 30 % and Gravel constitute less than 5 %. The Grain analysis result shows the presence of significant amounts of fine material. The OMC was 14 – 16 % while MDD 1.50 – 1.71 Mg/m3. The ranges conform to the values expected for clay soils. The soils’ cohesion ranges from 10kN/m2 to 20kN/m2 and the angle of internal friction ranges between 15o to 22o which is less than 30.0 This indicates that all the locations contains soil with poor slope stability according to Watkins, R.K and M.G Spangler (1958), on some characteristics of modulus of passive resistance of soil. The values of specific gravity ranges between 2.43 – 2.47 Mg/m3 which are quite low. It is finally concluded that the causes of cracks in the study area are as follow. Poor plasticity in all the locations except L5, low specific gravity, poor angle of internal friction etc.
Keywords: Geotechnical, Cracks, Building, Structural, Non- structural.