1.The supporting principles of advance ductile.
① Advance ductile is a very effective auxiliary method for excavating working face steadily. In weak and broken conditions, advance ductile has reinforcement effect, and after grouting, the stability of stratum is increased, which is beneficial to the stability of stratum during the primary support, avoiding collapse.
② Advance ductile is suitable in weak arch parts of tunnel, loose and non-binder soil layers, poor stability sandy gravels and broken stratum.
③ It can change the condition of stratum and stability after advance ductile grouting. After seriflux injecting into cracks, it can make surrounding rocks compact and coagulated. Seriflux can take up positions of water and air in the cracks by the forms of filling and splitting. It combines loose soil grains with glues and then forms a new structure with great strength and good waterproofness, which improves the break and loose conditions largely.
2. The construction method of traditional floral tube.
① Using electric drill to drill holes. The diameter of hole is 10-20 millimeters bigger than that of ductile. The depth of hole depends on the length of ductile.
② If it is difficult to insert ductile, pneumatic drill with jacking method is always used.
③ Using blowpipe to blow out the sundries in the hole.
④ Cotton yarn is wrapped the end of ductile, which makes the distance compact between ductile and drilling hole.
⑤ Sprayed concrete is used to seal surrounding spaces after installing ductile. The depth of spraying is about 5-8 centimeters.
3. The application of self drilling anchor bolt.
Self drilling anchor bolt is a kind of hollow anchor bolt, thread is over its surface, coupling can lengthen anchor bolt and disposable drill bit is installed at its front.
Because of special structure, self drilling anchor bolt has several advantages:
① High efficiency during construction: self drilling anchor bolt combines drilling, grouting and anchoring together, which decreases the working procedure and improves working efficiency.
② Extensive application: self drilling anchor bolt is suitable for stratum which is difficult to drill holes, such as weak and broken surrounding rocks, it is difficult to insert anchor bolt or cable and easy to collapse. After drilling, anchor bar stays in hole and don’t need to be pulled out, which saves time, decreases difficulties and avoids collapse.
③ Strong adaptability: thread is over the surface of anchor bolt, it can be cut at any position according to different construction conditions.
④ High anchorage force: the thread of self drilling anchor bolt includes R-type and T-type, which combines with grouting materials and then has good adhesiveness, high anchorage force.
⑤ Good anchoring effect: seriflux is grouted from down to up, which is sufficient and dense, so the quality of anchoring is quite good.
⑥ Simple and convenient construction: compared with common anchor bolts, self drilling anchor bolt has decreased the procedures of installing anchor bar, inserting injection pipe, which is simple and convenient for workers to operate.
Ductile grouting is an advanced method for supporting construction projects, it has overcome several challenges, so self drilling anchor bolt can apply to this kind of projects.