By Uzoma Oluchukwu Onyegbule
The recent harvests of deaths and destructions in Owerri and its environs has underscored the need for proper soil testing and evaluation before structures are erected on those sites. This simple but all important routine has been flagrantly neglected hence the many stories of building collapse witnessed in recent times in the state.
The clay minerals that dominate the soils in both humid and tropical regions are known to be either the 1:1 type or the 2:1 type of clay minerals.
The 1:1 type of clay minerals are known to exhibit good engineering prowess as their structures are fixed,less plastic and no expansion occurs in between the layers when the soils are wetted
In contrast the 2:1 type of clay minerals have both the expanding and the non expanding type of clay minerals eg the smectites group( known for their interlayer expansion are prominent in Imo state soils).This type of clay minerals are known to expand when the minerals are wetted,the water entering the interlayer spaces and forcing the layers apart.They are also known to be linked by weak oxygen to oxygen atoms hence the near dispersed nature of the minerals.Building or erecting structures on these type of clay will lead to its expansion during the rainy seasons and contractions during the dry seasons.Any structure erected on such soils must surely crack or collapse during this period of swelling and contractions.
Its on record that such clay minerals are prominent on the soils of Owerri and its environs.
The environmental impact assessment conducted at the site for the school of engineering in okigwe during the administration of Chief Ikedi Ohakim warned of the dire consequences of erecting big structures at the proposed faculty of engineering of the Imo state university dominated by the expanding 2:1 type of clay mineral (montmorrilonite),hence the stoppage of work at the site.
Its a fact that more than half of all high buildings(hotels in particular) today have either developed cracks or have undergone reinforcement. Such building's constitute an impending calamity if something drastic is not done.
Soil testing will help reveal the type of clay minerals present at such sites as well as other engineering properties of soils such as the atterbergs limits,bulk density,plasticity index etc.The results will aid in taking decisions before the actual construction sets in.
There should also be a routine checks for cracks in public buildings by goverment and any defaulting structure should be sealed as the owners may be unwilling to engage in the high cost of reinforcements
There should also be a legislation that will make it compulsory for soil testing before the actual construction.Construction at such sites should be approved only when such certifications are submitted to the relevant government agencies, also the practice of every dick and harry parading themselves as contractors should be checkmated. This will go a long way in reducing to the barest minimum the recent harvests of death and destruction of properties as is the case today.
Uzoma Oluchukwu Onyegbule is a Soil physicist and a conservationist