Application of self-drilling hollow rod and solid rod in different formations

Hollow rods and solid reinforced rods are two different forms of anchoring, therefore, the installation issue is related to ground conditions and the stability of the drilled hole, rather than space constraints.

In loose or collapsed formations, the self-drilling hollow rod body is the best solution, since this solution solves the problem of casing usage, it can be quickly installed and grouted at one time. In water-bearing gravel layers, casing can easily become stuck, so self-drilling hollow-rod systems are the most practical solution.

Although the variety of drill bits broadens the application range of the rod body, it does not mean that the self-drilling hollow rod body is suitable for all geological conditions. Bit selection ranges from mud bits for soil to spheroidal alloy bits for rock formations, and other types of bits.

In tight rock formations, the use of DTH drilling method is more efficient, so solid threaded steel bars are generally preferred, and the drill bits used for self-drilling hollow rod bodies are disposable bits, so they have lower alloy content and rougher bits compared to standard bits, cost-effective. Suitable for rock holes up to 5m deep, not suitable for deeper drilling.

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Under wet clay strata, solid threaded steel bars are preferred due to problems with self-drilling hollow rods. Under the wet clay layer, the drill cuttings are easy to get stuck in the hole, causing the hole to be blocked and the flushing to be blocked. Usually choose to drill with auger and then follow the scheme of solid rod body.

Self-drilling hollow rods can be used in wet clay soil if the drill has a nozzle on it. The system uses high pressure flushing, including a higher water-cement ratio (w/c 0.9 or similar) flushing fluid to create a jet at the bit that liquefies the clay and flushes it out of the borehole. In addition, the borehole diameter is significantly enlarged. The system requires a special high-pressure grouting pump that can handle larger volumes of flushing fluid (containing suspended clay particles) at the borehole.

Although self-drilling hollow bolts have obvious advantages in loose or collapsed formations, self-drilling hollow bolts cannot provide an effective drilling solution in wet clay or tight rock formations, where solid bolts are more effective. to be valid.

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