SDA bolt is a kind of hollow bar with continuous thread, one end connects to drill machine and another one connects to one-off drill bit. When drilling, slurry can be injected through hole of bolt, which realizes integrated construction of drilling, grouting and anchoring. After grouting, it can ensure cement mortar and cement paste wrapping overall length of SDA bolt, contacting with surrounding soil body and then forming a combination. When grouting, slurry is from bottom of hole, stop-grouting plug is installed to realize pressure grouting, which can fill gaps in sandy gravel stratum, enlarge diffusion radius and anchoring range. So, SDA bolt has good anchoring effect in loose stratum.

A lot of experience have shown that SDA bolt in loose stratum has safe, reliable and convenient characteristics and can be widely used in urban engineering construction.

Except meeting mechanical supporting condition, specific install direction of self drilling anchor system has a connection with location of anchoring stratum, retaining structure and construction condition. Inclination of self drilling anchor system should avoid the range of -10°~+10° with horizontal plane, because after grouting, slurry’s sediment and bleeding phenomenon will influence self drilling anchor system’s carrying capacity.

Self drilling anchor system’s carrying capacity is relative to limit friction resistance of soil body. Generally, soil texture at super stratum is poor than sub stratum, at the same anchorage length, the smaller inclination, the shorter anchorage body in good soil texture.

So, before formal construction, fundamental test of self drilling anchor system should be done to get relation between inclination and length and then provide design research decision.