Underpinning in Waterford

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This project was completed for a major insurance company in a karst region near Dungarvan, Co. Waterford. Cracking was noted by the insured when a neighbour notified them of a sunken patio during the increased rainfall event of 2015/2016.

This sudden movement resulting in Category 2 damage (cracking up to 5mm) was typical of the damage caused to come properties in Cork City during the same period. Such an event can be exasperated in karst areas which may have sinkholes, caves, etc.

Substruck was required to install an underpinning scheme designed by the consulting engineer representing the insurance. The scope was simply a series of micropile supported reinforced concrete cantilever beams needled into the rising walls along the areas of distress and associated building works including drainage.

Considering the hazards associated with karst features, any end bearing pile could not be relied upon due to the risk of punching failure. In order to achieve the loads, a rock socket was required but there would always be the concern of grout loss.

Simultaneous drill and grout systems cannot progress with maintaining a head of grout. During the formation of rock sockets in all 20 nr micropiles, drilling was slow as significant grout loss was encountered. When the head was lost, filling from the collar was completed until a head was achieved once again and grouting re-commenced. Some rock sockets took about 50 times the theoretical volume of the borehole!!!!!

On completion of the underpinning, the affected areas were reinstated.