Ground Anchors

Ground Anchor or also called the tiebacks is a pre stress grouted, an element installed in soil or rock that is used to transmit an applied tensile load to the ground. Ground anchors with grout are installed in grout filled holes. The three basic components of a tiebacks is the anchorage, free stressing (un bonded) length and the bond length. The anchorage is the combined system of anchor head, bearing plate, and trumpet that is capable of transmitting the pre stressing force from the pre stressing

Straight shaft gravity-grouted ground anchors are typically installed in rock and very stiff to hard

cohesive soil deposits using either rotary drilling or hollow-stem auger methods. Tremie (gravity

displacement) methods are used to grout the anchor in a straight shaft borehole. The borehole may

be cased or uncased depending on the stability of the borehole. Anchor resistance to pullout of the

grouted anchor depends on the shear resistance that is mobilized at the grout/ground interface.

• Post-grouted ground anchors use delayed multiple grout injections to enlarge the grout body of

  straight shafted gravity grouted ground anchors. Each injection is separated by one or two days.

  Post grouting is accomplished through a sealed grout tube installed with the tendon. The tube is

  equipped with check valves in the bond zone. The check valves allow additional grout to be injected under high pressure into the initial grout which has set. The high pressure grout fractures the initial grout and wedges it outward into the soil enlarging the grout body. Two fundamental types of post grouted anchors are used. One system uses a packer to isolate each valve. The other system pumps the grout down the post-grout tube without controlling which valves are opened.

1. • Underreamed anchors consist of tremie grouted boreholes that include a series of enlargement bells

     or underreams. This type of anchor may be used in firm to hard cohesive deposits. In addition to

     resistance through side shear, as is the principal load transfer mechanism for other anchors, resistance may also be mobilized through end bearing. Care must be taken to form and clean the under reams.

Soil Nails are commonly used on retaining walls, for slope stabilization, to uplift slabs and even for concrete dam stabilization.  They can also applied Ground Anchor techniques on the following:

• Foundations

• Erosion Control

• Bridges

• Landfill Capacity

• Pipelines

• Rock retention

• Gabion support

• Sheet piling

Advantages

1. Execute excavations neatly to create large construction plan without using props in order to make mechanized excavation.

2. Keep excavation walls sustainable, make very deep excavations without depending on the basement structure.

3. Anchors combine with soft retaining walls to redistribute the intemal forces of wall structure, so this can reduce the size, depth of steel bars in retaining walls.

Disadvantages

1. It is necessary to use specifed equipment, exprienced professional engineers.

2. It is difficult to apply anchors in weak soil and to implement anchors with great depth.

3. Anchor execution would affect the land of surrounding construction works, which must be accepted by their owners.

Some of the disadvantages of soil nails are:

• Soil nails are not applicable for large amount of groundwater seeps on excavation.

• Permanent long term applications are not recommended.

• Sand and gravels are not compatible on this process.

• Not practical to use on areas with a high water table.

Contact the specialists at Geo Grout Ground Modification Specialist Inc. of Western United States for your chemical grouting project needs. Call us at (650) 241-2400 for complete information on our Ground Anchors services or email us at inquiries@gggms.com to discuss your Ground Anchors needs today.