JPS6117115Y2 - - Google Patents

Description

[Detailed explanation of the idea]

The present invention relates to a lock bolt in which a coating agent is applied to the outer periphery of a deformed steel bar having an optimum knot pitch in the lock bolt construction method. Lock bolts are now frequently used in tunnel construction methods. Conventionally, it has been assumed that the fixing force of this lock bolt is achieved by integrating it with the rock by the adhesive force of the filler, and a high-strength resin type is used as the filler. However, according to the results of the pullout test, as shown in the table, cement mortar was used as the filling material and the material was in an unconsolidated state (στ = 5 to 10 kg
/cm ² ), but if the knot pitch of the lock bolt is optimal, it will have the pull-out resistance to cut at an embedded depth of 30 cm.

[Table] From these results, it is clear that the fixing force of the lock bolt is due to the wedge effect produced by the joints of the lock bolt, rather than the adhesive force. Further, as shown in Fig. 1, a deformed steel bar 3 is embedded in a soft rock 1 using a resin-based filler 2, and when pulled out in the direction of the arrow, a high-strength filler 2 forms around the deformed steel bar 3 in the shape of an ice cream. In this state, it will easily come out with the shear force of soft rock 1 or less resistance. This shows that using a high-strength resin-based filler for the soft rock 1 is rather harmful. Therefore, the present invention uses a deformed steel bar 3 having an optimal knot pitch, and a lock bolt 4 with a coating 5 of a coating agent that prevents cement-based filler 6 from adhering to the outer periphery of the deformed steel bar 3. As shown in the figure, when a cement-based filler 6 is used to embed the rock bolt 4 and the rock bolt 4 is pulled out, when a relative change occurs between the soft rock 1 and the rock bolt 4, a change occurs between the cement-based filler 6 and the rock bolt 4. Sliding easily occurs, and the cement-based filler 6 is pressed against the soft rock 1 by the wedge effect of the nodes 7. As a result, the frictional force increases, resulting in a pull-out resistance several times greater than the shear force resistance of the soft rock 1. As mentioned above, when a rock bolt coated with the coating agent of the present invention is used, when a relative displacement occurs between the soft rock and the rock bolt, since the rock bolt and the filler material are not attached, slipping easily occurs and wedges occur. The effect is maximized and a great fixing force is produced.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing the pulled-out state when a conventional resin-based filler is used, and Fig. 2 is a cross-sectional view showing the pulled-out state when the lock bolt of the present invention and cement-based filler are used. . 1... Soft rock, 2, 6... Filler, 3... Deformed steel bar, 4... Rock bolt, 5... Coating agent, 7... Section.

Claims (1)

[Scope of utility model registration request] In the rock bolt construction method, in which a hole of a required length is drilled in the rock and the steel material inserted into the hole is integrated with the rock by solidification of the filler, the filler is not attached to the outer periphery of the deformed steel bar having knots. A lock bolt coated with a coating agent.