Large building and infrastructure projects often have many intermediate phases which also need engineering design and geotechnical solutions if they are to be executed safely, efficiently and economically in a limited space. Phase plans for temporary redirection of traffic or measures for loading and transport of spoil from deep, constricted construction pits may require extensive geotechnical planning and engineering design and may be expensive to implement. Lime cement piles for stabilising capping layers or site roads or lightweight material such as foam plastic as temporary infill for accommodating height differences in weak soils are examples of temporary measures for enhancing construction site productivity in the early phases.
The application of infill or covering of land fill and contaminated soil requires monitoring and inspection of soils, layer thicknesses and compression. This applies to work both on land and under water. NGI has long experience of preparing technical descriptions, drawing up inspection plans and monitoring geotechnical engineering works such as sheet piling, column piling, bracing, compression, excavation and sorting of contaminated soil in complicated phases of the construction work and ensuring that the work is documented in accordance with the contract.
When infilling at sea, the surroundings areas may be protected with silt curtains and turbidity monitoring. Large construction pits may have a draining effect on neighbouring areas, which in turn will cause subsidence. As a countermeasure, pore pressure gauges and infiltration wells can be installed, and the measurements taken and monitored online. This allows for a rapid response with mitigation measures, a welcome reassurance for construction pit neighbours.
NGI's specialist expertise
- Engineering design of construction pit protection and robust temporary measures for implementation of the construction phase
- Instrumentation and monitoring of deformations, pore pressure and loads, thus ensuring rapid response, good documentation and opportunities for recalculating and improving the engineering design basis
- Understanding of execution and requirements for equipment, materials and space requirements
Research and development
- Together with a working group of many different contractors, consultants and clients, NGI has carried out extensive research into geotechnical construction problems such as drainage and subsidence round construction pits and into low-impact drilling methods for braces and piles in the "BegrensSkade" project. (link)
- Research effort is also directed to instrumentation and test loading of piles, bracing load gauges and deformation in sheet piling, dynamic pile analyses (PDA), pore pressure development in the case of pile and infill work and modelling of the spread of contamination along trench lines and other types of
- layers of open materials applied to the ground.