Thrust anchors are usually used when what condition exists?

• A. Soil has been disturbed such that a concrete block will not work
• B. Time and cost need to be reduced
• C. Horizontal bend in pipe
• D. Vertical bend in pipe

Answer: (A)

Thrust anchors are used when the pipe must be restrained but the soil cannot reliably bear a traditional thrust block. A thrust block transfers the thrust from a change in direction or a valve into the surrounding soil, so if the soil has been disturbed or is weak or unstable, a concrete block won’t develop the necessary resistance. In those cases, mechanical anchors are installed—anchored to solid material such as rock or a stable foundation—to provide the required restraint without depending on soil bearing. Time or cost savings or merely the pipe’s orientation aren’t the primary condition; the key issue is the soil’s inability to support a thrust block.