Site investigation is an indispensable activity prior to any construction. This essay discusses the need for site investigation for a proposed development project involving construction of a two-storey building at Canbury Park, Kingston Upon Thames. The essay discusses the implications of not carrying out site investigation, the various types of information that a structural or a geotechnical designer gets from site investigation, the kind of information a constructor gets from site investigation, the range of information to be recorded in a borehole log upon completion of site investigation, and the potential geotechnical risks associated with the area that the project site lies.
Implications for not carrying out SI
Site investigation (SI) is simply the process of collecting information about a particular area in which a construction project is to be done. It plays a very important role in understanding the ground conditions on which the project is to be built. In this case, SI would inform the designer and the constructor of vital information, which would otherwise have cost implications. Generally, although the cost of SI is small, there are many implications for not carrying it out. Firstly, it is hazardous to construct a building, whether storey or not, on a ground that has not been investigated. Lack of SI means that the professionals are not aware of the soil conditions, the underlying strata and permeability levels. This could lead to future sinking of the building. In other terms, lack of SI could lead to unstable storey building. Secondly, failure to carry out Si is illegal. This is because if the building collapses in future, the designers and constructors could be sued for not having conducted SI. Not carrying out SI is not only illegal, but also unethical and unprofessional. Lastly, failure to carry out SI could lead to a lot of expenses for contingencies.
Type of information that a structural or geotechnical designer gets from SI
For the designer, SI provides valuable information with regard to the environment. The designer is also able to identify the potential obstructions for the storey, which the designer understands the aerial conditions. The designer is also able to understand information regarding stress, strain, geotectonics, hydrology, weathering and geomorphology. According to INA, SI provides information that helps in slope design, foundation design, safety requirements, and legal provisions. Over and above these pieces of information, the designer gets topographical information, the actual location, site history, plan profile, drainage information, groundwater information, slope design, and existing information on foundations. Other useful information include geological maps, slope instability such as bent trees and displaced fences, design parameters and accessibility.
Type of information that a constructor gets from SI
Through SI, the constructor is able to understand the rock conditions, presence or absence of boulders and cobbles, soft ground conditions and mixed-face conditions. Specifically, the constructor is able to know the moisture content, unit weight, plasticity index, compressibility, shear strength, and consistency in places where there are cohesive soils, such as silt and clay. Through Si, the constructor is also able to know other soft ground conditions such as hydraulic conductivity, density, a unit weight, and grain distribution size distribution for cohesion less soils. With regard to rock conditions, the constructor gets the following information: cutability, rock type, strength, hardness, depth and extent of rock, mineralogy, abrasiveness, poissonâ€™s ratio and modulus of elasticity. Through SI, the constructor is able to decide on the properties and quantities of materials to be used for the construction of the house.
Type of information for borehole log
For borehole construction, SI collects variety of information. However, this information is usually aligned with the type of soil or material. For granular soils, site investigators collect information on mass permeability. For soils and rocks, the type of collected information has to do with dredge ability. In order to collect most information for borehole construction for most soils, but cobbles, boulders and weak rocks, SI entails indicative shear strength of cohesive soils, relative density of granular soils and indicative strength of weak rock. Before boreholes are constructed in sites with sands and gravels, the following information is collected: qualitative evaluation of subsoil stratification and qualitative evaluation of relative density or compactness. For boreholes to be built on clay silts and soft to firm clays, SI collects information on remoulded shear strength and undrained shear strength.
Potential geotechnical risks for the project site
A geotechnical risk is the danger that is posed to a building by ground conditions of the site. These conditions should be identified during SI. Geotechnical risks are technical, contractual or managerial. Technical risks are either geological, analytical or based on properties. Geological risks are unforeseen conditions while analytical risks occur when wrong models are chosen. If unreasonable design values are chosen, the risk is purely of properties nature. If the SI and the geo-engineering processes are poorly managed, the geotechnical risks are either contractual or project management risks.
For the Canbury construction project, geotechnical risk could also emanate from the project staff. Indeed, people are a major source of geotechnical risks. This means that the Canbury project shall require good risk management techniques. Although, humanâ€™ error is a major source of errors.Â The lack of SI could lead to the most serious geotechnical risks. Canbury Park is not immune from unforeseen future underground movements, which could lead to collapse of the house. One of the most important things to consider is the possible sources of geotechnical risks at Canbury Park. It is important to consider the ground water of River Thames as a â€˜theoryâ€™ that would inform the design and construction of the two storey house.
This essay was meant to justify the need for site investigation for the construction of a two storey building. To effectively achieve that the essay is focused on the implications of not carrying out site investigation, the various types of information that a structural or a geotechnical designers get from site investigation. The kind of information a constructor gets from site investigation, the range of information to be recorded in a borehole log upon completion of site investigation, and the potential geotechnical risks associated with the area that the project site lies. It was shown that SI is in indispensable activity for any sound construction to be achieved. If Si is not carried out, the project would suffer from some cost and technical risks. SI accords designers and constructors with the most vital information for their work. For the borehole component, myriad information would be required depending on the soil type at the Canbury site. Finally, a major geotechnical risk could emanate from the ground water of Thames River.