Pressure Relief Wells can be installed to offer a preferential groundwater pathway and reduce porewater pressure beneath the base of an excavation or structure.
Pressure Relief Wells
Pressure relief wells are generally used to depressurise and reduce porewater pressures in a confined aquifer beneath an excavation. They are located within the footprint area of the excavation or internally within a shaft. They can offer a long-term solution to groundwater pressures beneath a structure such as basements and tunnels.
Typically pressure relief wells are drilled through the base of an excavation or structure and back filled with an appropriately design filter gravel, that maximises the flow pathway, without permitting excessive ingress of fines. Gravel filled pressure relief wells can easily excavated through as the dig progresses.
In some instances, a small (nominal 50mm Ø) well liner maybe installed to offer some control to water seepage. On occasions larger liners are installed into which a borehole pump can be installed to assist in removal of residual groundwater.
In most cases either a drainage blanket or a series of drainage trenches, connecting individual pressure relief wells is places at the based of an excavation. In turn any groundwater up flow seepage is allowed permeate into the drainage blanket and a sump pump arrangement removes this water from the dig area.