Background
Porewater pressure, or the pressure of groundwater held within soil, rock, or gaps between particles, is an important factor in determining the stress state of soil. If the porewater pressure is increased to equal the applied soil effective stress, the soil may lose its strength and stiffness, and act more like a liquid, in a process called liquefaction. Soil liquefaction occurs most often in saturated, loose, sandy soils, which has a tendency to displace under the applied load, which may result in damage to foundations and the structure they are holding. Currently, piles and drilled deep foundation shafts are not embedded in potentially liquefiable soils due to high risk of liquefaction and excessive settlement, and must be placed deeper in the ground to avoid liquefaction.
Description
Researchers at the University of Nevada, Reno have developed a deep foundation porewater pressure dissipater for dissipating generated water pressure generated beneath a pile or drilled shaft during periods of excess pressure generation. Water is able to dissipate to the surface though pipes, allowing piles and shafts to be embedded at optimal depths in the ground without risk of liquefaction during periods of stress, such as earthquakes. The dissipater comprises aggregate, composed of uniform sized particles; a cylindrical receptacle for receiving the aggregate, made from a geosynthetic fabric such as polyester or polypropylene fine enough to selectively allow water to flow through and not soil; and a top and bottom surface plate with varying modifications for sealing the receptacle, coupling the dissipater to a pile/shaft tip, and allowing water flow through access pipes or other outlet surfaces.
Advantages
- Our dissipater prevents excess porewater pressure buildup at the tip of deep foundations
- Our dissipater may prevent liquefaction of the end bearing soil during earthquakes
- Our dissipater allows embedding of piles and shafts to be at more optimal depths
Patent
UNR16-006
