Water Inflows in Deep Excavations in Karstified Rock
A Spotlight on Qatar
Since the dawn of mankind, underground structures, either natural or manmade, were part of life. From the Eupalinian Aqueduct built in the sixth century BC to the deep excavations for the high-rise buildings of Manhattan skyline, to the Doha Metro, the geotechnical sector has become a very specialised industry.
To achieve a smooth design-construction synergy, it is essential to appoint experienced designers to achieve the correct results. In this field, as in others, nature provides many challenges and we must draw lessons from failures, improve techniques and use all our resources of creativity to succeed.
What Are the Key Factors Impacting Deep Excavations?
Deep excavations are required to accommodate buildings, shafts or other local underground structures related to urban expansion. From a geotechnical perspective, the geology, the stratigraphy, the groundwater regime and the surrounding geometrical and loading restraints must be considered.
Although all factors are important, any potential stability problem can be accommodated with a more robust retaining system. The presence of underground water, if not properly considered and managed, can produce significant delays in construction and increase the cost.
The full understanding of which remains unknown until the works are out of the ground and reaching skywards. As such, these projects typically face many uncertainties and significant risk such as:
- unreliable predictions of ground conditions;
- complex technological challenges; and
- the need for intensive investigations before and during construction.
These factors, coupled with the different interests of those either directly or indirectly involved, almost always leads to disputes, either between the Contractors with the Designer for not properly assessing the prevailing conditions or between the Contractors and the Clients for unforeseeable conditions.