A grouted pile, also called a screw injection pile or micropile, is a foundation pile formed in the ground by injecting grout (cement mortar) under pressure around a steel tube or bar. Because the grout mixes with the soil and is pressed outward, a pile is created with a rough shaft and a good bond to the ground.
How it works
To form a grouted pile, a hollow rod or tube is screwed or drilled into the ground. During installation or withdrawal, grout is injected through the tip, which partly displaces and strengthens the surrounding soil. The steel core remains in the pile and takes up the tensile and compressive forces.
Applications
Grouted piles are often chosen where ordinary driven piles are difficult:
- Underpinning — strengthening existing foundations, even inside buildings with limited headroom
- Vibration-sensitive surroundings — a low-vibration alternative to driven piles in built-up areas
- Tension piles — for example against uplift of basements and tank structures
- Small plant — installable with compact equipment in hard-to-reach locations
The grouted pile combines the installation of a load-bearing core with grout injection for ground improvement and bond. Because the grout makes the shaft rough and wide, high shaft friction develops, which is especially favourable for tension loading.
Related terms
Want to learn more about construction terms? Visit our knowledge base at fredsdiyplans.com.