Dynamic Bolts & Products - Dynamic OMEGA-BOLT®
The Dynamic OMEGA-BOLT® is an evolution of the DSI Underground OMEGA-BOLT® a high pressure inflatable friction bolt, used to secure a great variety of ground conditions, subjected to different stress conditions. All OMEGA-BOLT® systems are based on a steel tube, longitudinally formed in its typical omega (Ω) shape and made pressure tight by welded bushings on each end. The Dynamic OMEGA-BOLT® adds an extra steel element that is placed inside the omega shaped profile and welded to the upper and lower bushings. This extra element provides the capacity to absorb a large quantity of elastic energy in case of rock bursts as well as additional loading capacity in static conditions.
Main Applications
The Dynamic OMEGA-BOLT® has been developed to provide safe, effective, and fast rock support in mines or tunnels where high stress in the rock mass can create a sudden release of energy (rock bursts). These micro-seismic events are similar to an explosion, able to crush rock and eject fragments into the excavated drifts, and they represent a great danger to miners and equipment. In these cases, there is a need of a “dynamic” rock reinforcement system, meaning a series of elements able to dampen the explosion-like phenomenon and still able to retain the crushed rock from falling down. The Dynamic OMEGA-BOLT® is a fundamental part of modern dynamic reinforcement; it is able to absorb 35 [kJ] of energy and still retain a residual loading capacity in the range of 70 [kN].
Technical Data
| Dynamic OMEGA-BOLT® Type 35 [kJ] | Unit | Design Parameters/ Minimum Values | Typical Values |
|---|---|---|---|
| Steel: yielding/tensile stress | [MPa] | 350/500 | - |
| Steel elongation (A5) | [%] | 10 | 15 1) |
| Steel sheet thickness (inner/outer profiles) | [mm] | 2 | - |
| Steel cross section, outer profile | [mm²] | 326 | - |
| Steel cross section, inner profile | [mm²] | 154 | - |
| Bolts mass per meter | [kg/m] | 3.75 | - |
| Bolt diameters: installation profile, upper bushing, lower bushing | [mm] | 36/38/41 | - |
| Diameter fully expanded profile | [mm] | 54 | - |
| Recommended drill hole diameter | [mm] | 45 -48 | - |
| Static ultimate tensile load-bearing capacity | [kN] | 163 + 77 = 240 | - |
| Static shear resistance 2) | [% UTS] | - | 85 - 90 |
| Dynamic energy absorption (1 drop) | [kJ] | - | 35 1) |
| Plate displacement (1 drop) 3) | [mm] | - | 350 1) |
2) SINTEF (Norway) laboratory tests, 2014
3) On a 2.4m long bolt
All values are subject to change
The dynamic behavior of the Dynamic OMEGA-BOLT® has been tested by a qualified Canadian public institution. The results prove the bolt’s capacity to absorb 35 [kJ].
This value is higher than the quantity of energy which is normally considered as the reference value for micro-seismicity risk in large, deep underground mines (i.e. 30 [kJ]).