ENGINEERING TERM OF THE MONTH Ground Anchors
Ground anchors are used systems used to provide temporary and permanent stabilization for walls and slopes , and to provide tiedown for structures such as buildings , towers and dams . Ground anchors are typically cement grouted , prestressed tendons installed into soil or rock .
In the U . S ., the first use of ground anchors was for temporary support of excavation systems . The U . S . Bureau of Reclamation began using anchors to stabilize appurtenant structures at dams in the late 1960s . In the late 1970s , permanent ground anchors became common in the U . S . for public sector projects .
Ground anchors consist of pre-stressed , grouted structural elements installed in soil or rock that are used to transmit an applied tensile load to the ground . The ground anchors are typically installed using rotary , percussion , rotary / percussive , or auger drilling . The capacity of a single ground anchor is a function of the bond stress of the element with the surrounding soil or rock , and is based on soil properties , drilling method , bonded length , hole diameter , and grout pressure . Permanent ground anchors are designed with corrosion protection to meet the design life of the project .
In addition to determining of capacity of a single anchor , the ground anchor system has to consider various other design elements , including internal and external stability , basal stability , wall or ground movements , overall rock mass stability , and other considerations .
After installation , each ground anchor is load tested prior to being put into service to verify the anchor load capacity and load-deformation behavior .
Reference : Geotechnical Engineering Circular No . 4 , Ground Anchors and Anchored Systems ; U . S . Department of Transportation Federal Highway Administration
Sources : � Geotechnical Engineering Circular No . 4 , Ground Anchors and Anchored Systems ; U . S .
Department of Transportation Federal Highway Administration � Rock Anchors for North American Dams : The Development of the National Recommendations
( 1974-2004 ); Donald Bruce , John Wolfhope � Recommendations for Prestressed Rock and Soil Anchors , Post-Tensioning Institute , 1996
5