Every high-rise building and road you see in the world rests on the hard work of a geotechnical engineer. Like Structural and Transportation Engineering, it is a branch of Civil Engineering.
Every construction project needs to know if the soil on which it will sit can support the structure that is to be built. A reliable Geotech engineer can foretell potential issues and recommend methods to mitigate them.
Subsurface Investigations
Often the most challenging aspect of a project for a Geotech Engineer is simply finding out what’s underneath a site. Having conducted numerous subsurface investigations, the geotechnical engineers can recommend allowances such as allowable bearing capacity and estimates of settlement for structure foundations, earthworks, retaining walls and slopes. This is often crucial to avoiding costly delays and cost overruns whilst construction is underway.
During the initial stages of investigation a geotechnical engineer will conduct a desk study, assess maps and carry out trial pitting to determine the soil characteristics in order to create a geotechnical model of the ground conditions at a project site. They will then direct boreholes and test pits to collect samples of the ground and will send these off for laboratory testing. This helps in assessing the strength, compressibility, reactivity and permeability of the ground which can be used to inform the design process. The geotechnical engineer can then use this data to predict what will happen when a structure is loaded in the field.
Design of Structural Foundations
Foundations are responsible for supporting and transferring loads from the building structure to the ground. They are critical to ensuring the stability of a building and the safety of its occupants. This requires a thorough soil investigation to determine the site conditions and design a foundation that can withstand the loads placed on it.
These engineers analyze the subsurface materials such as sand, rock, clay, silt, and water to ensure they are safe for construction. They also evaluate the slope stability of the building site, assessing the potential for landslides and earthquake hazards.
Foundations are designed to meet specific dimensions for floor load bearing. These values are determined based on the safe bearing capacity of the soil at different depths, taking into account the engineering properties of the foundation soil. They are also designed to distribute the loads evenly, avoiding uneven settlement of the building. This is achieved by determining the moment, which is multiplied by a factor to calculate the axial load, and the lateral soil pressure.
Geogrids
The use of geogrids increases the strength and performance of a foundation or platform to help it resist loads. It can also allow a thinner platform construction to be used saving cost and increasing sustainability.
Geogrids are part of a larger group of plastic polymer products known as geosynthetics which can improve engineering projects through a number of functions including drainage, filtration and reinforcement. These materials are used in a wide range of civil engineering projects including roads, buildings and retaining walls.
Uniaxial, biaxial and triaxial geogrids have a variety of mechanical properties depending on their geometry. Creep testing a key mechanical test on geogrids can determine the maximum load-bearing capacity of the material by measuring a time-dependent increase in accumulated strain characterized by sample elongation. This is often correlated to ultimate tensile stress (UTS). More work needs to be done on testing standards for creep testing of geogrids. The coating of the geogrid can also impact its behavior. A conductive coating such as PVC polymer with filler of carbon black (PVC/CB) has shown to be able to increase the sensitivity of the geogrid.
Environmental Impact Assessments
Like other engineering branches, such as structural, hydro and transportation engineering, geotechnical engineering carries with it a responsibility to minimize the negative impact of human activities on the environment. As such, environmental issues form a significant part of the geotechnical engineer’s work and play an important role in site characterizations and analytical studies.
Many countries that are considered environmentally progressive now require that new development projects carry out an Environmental Impact Assessment before they are approved for implementation. This enables any problems that may be caused by the project to be foreseen and prevented.
The EIA process can be complicated and requires a great deal of research, data collection and expert advice. This includes an examination of the physical aspects of existing geology, chemical changes to water and air, biological effects on fauna and flora, social and cultural impacts on people living in the area, plus short, medium and long term effects of the proposed project.
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