The hollow bar, used as both drill rod and grout conduit, is left in the ground as reinforcing steel to transmit compression, tension, and lateral forces. Hollow bars have a larger section modulus than solid bars which increases their bending capacity. With the continuous tremi-grout injection, 100% grout cover and therefore excellent corrosion protection is accomplished, similar to reinforcing steel in concrete. Hollow bar micropiles are gaining increasing acceptance by engineers and the industry. Hollow bar anchors are manufactured from high yield micro alloy steel tubing. Hollow bars are installed using the injection bored method, which involves pumping at pressure a cementious grout while the anchor is drilled into the grout. This method has many geotechnical benefits and it improves a project’s overall efficiency. A hollow bar micropile requires no pre-drilling. As the hollow bar micropile is drilled into place, fine cement grouting is continuously injected until the hollow bar reaches its desired depth. In addition to continuous drilling and grouting, the hollow bar micropile uses casing for additional bearing capacity for lateral loads. The Sinorock hollow bar micropile can drill to any rock depth and is used for any soil type. Different sacrificial drill bits at the tip of the drill accommodate various soil types. The drill bits are designed to easily cut through hard rock, soft rock, or clay soils. Hollow bar micropiles require less equipment than conventional micropiles and allow for easier access into limited space. A rock drill and grout plant is the only equipment necessary for Sinorock hollow bar micropiles. The rock drill is a rotary and percussion drill that is small and easy to use. The grout plant is slightly larger and is a high shear and colloidal mixer, two-stage high pressure pump used to push grout into the drill and hollow bar.
