Investigating structural cracks for infrastructure: Case study of anonymous hospital, in Zimbabwe

Abstract

The main objective of the research was to investigate the structural cracks for infrastructure at the anonymous Hospital in the place under study, in Zimbabwe and recommend the appropriate engineering solutions to the structural problems. The specific objectives involved conducting desk studies, geotechnical and materials investigations, investigating the structural designs for the existing infrastructure and producing the construction schedule. A reconnaissance survey was also conducted together with key informant interviews. Geotechnical tests included sieve analysis, shear strength tests, direct cone penetrometer test, chemical dispersive test and California bearing ratio test. Structural analysis and designs were also conducted to model the relevant solutions. Most of the crack widths exceeded the design limits so these are structural cracks. The soil in the vicinity of the site is classified as Clay of Intermediate Plasticity and Clay of Low Plasticity. The soil has adequate bearing capacity and the minimum foundation depth is 1.5 m for a bearing capacity of more than 100 kPa. It is concluded that the first cause of the cracks on some of the buildings were the use of weak construction material such as farm brick which would easily deform under a small load and the depth of the foundation was less than the minimum of 700 mm, which was also on weak soils. The mortar thickness was extensively huge resulting in hyaline horizontal cracks and the bearing capacity and factor of safety were inadequate resulting in foundation failure. The dispersive test also proved that the soils are sodic in nature. The bearing capacity of the soil in some areas is not adequate to carry the imposed loads. It is recommended to use reinforced strip foundations and deep foundations when constructing infrastructure at the site. Heavy duty concrete foundation underpinning is recommended for the existing buildings. The total cost for repairing the damaged infrastructure is valued at US$456 800.