JPS6039797Y2 - Lock bolt for axial force measurement - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a lock bolt for measuring axial force, which is mainly used for remote measurement of axial force.

Rock bolts are commonly used along with shotcrete as a reinforcement method to prevent rock collapse during rock excavation for tunnels, underground power plants, underground oil tanks, etc., but their importance has increased with the spread of the Natume method. It's only going to increase.

By the way, especially in cases where the stability of the storage tank is secured with rock bolts, shotcrete, etc. without lining it with concrete later, such as in underground petroleum storage tanks, it is necessary to confirm the supporting effect of the rock bolts.

Due to these requirements, the stability of storage tanks, etc. is confirmed by determining the axial force distribution in the length direction of rock bolts and comparing it with the stability analysis results of storage tanks, etc. When the cross-section of a large cavity is large, it is necessary to construct a scaffold for measurement, and when there are many measurement points, it takes time to measure, and furthermore, it is not possible to measure the oil after it has been stored, so the need for remote measurement tends to increase. It is in.

In view of the above points, lock bolts shown in FIGS. 1 to 7 have been put into practical use as lock bolts for measuring axial force.

That is, the lock bolt for axial force measurement shown in FIGS. 1 to 3 has shallow grooves 2a in the longitudinal direction on both sides of the bolt body 1a.
A strain gauge S is attached to the bottom of the groove 2a, the lead wires 3 are wired in the groove 2a, and a caulking material 5 with excellent adhesive strength is filled.

In this rock bolt for measuring axial force, the width W of i2a cannot be made too small due to the size of the strain gauge S (at least about 1-1), and if this is made larger, the diameter of the bolt body 1a will increase. At most 22~35mmφ
Therefore, the surface shape of the bolt body 1a changes, there are many defects, and the section modulus becomes extremely small.

Therefore, in view of the strength and accuracy of the bolt body 1a, the depth d of the groove 2a must be limited to about 5 to 8rrrII4, but if the groove 2a is made shallow in this way, when a large number of strain gauges S are used, Since the lead wire 3 protrudes from the groove 2a of the bolt body 1a, it is not possible to increase the number of strain gauges S used to increase measurement accuracy, and the hole 4 into which the bolt body 1a is inserted is Due to the fact that the hole is drilled with as small a clearance as possible from the bolt body 1a, the caulking material 5 applied in the groove 2a of the bolt body may peel off or the lead wire There are many problems during construction, such as wire breakage.

In addition, deformed steel rods are generally used, but because the surface shape changes, the adhesion of the adhesive material (mortar, etc.) between the rock and the rock bolt is poor.

The rock bolts for measuring axial force shown in FIGS. 4 and 5 are made by cutting a bolt body 1b into two, digging a groove 2b inside, pasting a strain gauge S thereon, and then gluing them together.

This rock bolt for measuring axial force not only has the same problems as the rock bolt for measuring axial force shown in FIGS. 1 to 3, but also has the disadvantage that its strength is reduced by adhesion.

In addition, the ones in Figures 6 and 7 have a strain gauge S pasted on the inner surface of the hollow bolt body 1c, but unlike a normal bolt body, this has low strength and the strain gauge S
There are many problems, such as having to provide a joint part 6 every time a paper is pasted.

Therefore, efforts have been made to make the strain gauge S as small as possible and to make the lead wire 3 thinner, but these efforts have not yet solved the above-mentioned problems.

This idea is based on the conventional method described above, in which a split groove is formed in the bolt body along the length direction from the outer surface to the center, and strain gauges are affixed to the mutually opposing inner surfaces of the split groove. This problem has been solved, and there is no need to worry about the strength of the bolt body, and many strain gauges can be attached to it.Moreover, there are no problems during construction, and highly accurate measurement data can be obtained. The purpose of the present invention is to provide a lock bolt for measuring axial force that is inexpensive to manufacture.

This invention will be explained in detail below with reference to the drawings.

Figures 8 and 9 show an embodiment of this invention, in which a bolt body 11 made of a deformed steel rod (drawn as a round bar in the drawing) has a split groove 12 at the tip of the bolt body 11. It is perforated along the length, leaving the section 14 and the head 15.

The slot 12 is formed radially from the outer surface of the bolt body 11 and ends approximately near the center of the bolt body 11.

The strain gauge S has a lead wire 13 connected to the strain gauge S inserted into the groove 12 and attached to the inner surface of the groove 12 facing each other.

The width W of the split groove 12 is determined based on the above requirements, but if it is made too large, the section modulus of the bolt body 11 will be greatly reduced as described above, so a strain gauge S is installed on the opposing inner surface of the split groove 12. The width is set to the minimum width that allows the lead wire 13 to be attached and fit into the measured groove 12 without any trouble.

According to experiments, the width W of the split groove 12 was about 5 mm, and when the bolt body 11 with a diameter of 3 oHn was tested with a depth d=15 mm, the section modulus decreased by about 14%.

On the other hand, a hole 16 for taking out the lead wire 13 is bored in the head 15 of the bolt body 11 so as to communicate with the split groove 12 .

The lead wire 13 housed in the split groove 12 is taken out from the take-out hole 16 and directly connected to the multicore cable 18 of the strain measuring instrument 17.

The tip 14 of the bolt body 11 is appropriately sharpened, and the outer peripheral surface of the head 15 is threaded.

19 is a caulking material filled in the groove 12.

The rock bolt for measuring axial force of this invention is constructed as described above, and is inserted into a hole drilled in a rock and brought into close contact with the rock to measure the axial force, as in the conventional method.

However, in the lock bolt for measuring axial force of this invention, a split groove 12 is formed in the bolt body 11 from the outer surface toward the center along the length direction of the bolt body 11, and the opposing inner surface of the split groove 12 is formed with a split groove 12. Since the gauge S is attached, the width W of the split groove 12 can be made as narrow as possible to prevent the section modulus of the bolt body 11 from decreasing.

Therefore, there is no need to worry about the strength of the bolt body, and the bolt body remains almost unchanged from its original shape, so it has good adhesion resistance to the rock (especially when using steel bars of different diameters), and it is also possible to use a long bolt body.

In addition, since the split groove can be made deep and the strain gauge S can be attached deep inside, the lead wire 13 will not break or the caulking material 19 will peel off during construction, and moreover, the strain gauge S can be attached to the deep part of the groove. Not only can the corner gauge S be attached, but also the strain gauge S can be attached near the center of the bolt body 11 to obtain highly reliable data.

Furthermore, since the strain gauge S can be attached by heat baking, it is possible to obtain a rock bolt for measuring axial force that is highly durable and inexpensive to manufacture.

[Brief explanation of the drawing]

Figure 1 is a front view of a conventional lock bolt for measuring axial force, Figure 2
The figure is an enlarged sectional view taken along the line ■-■ in Figure 1, Figure 3 is a sectional view taken along the line ■-■ in Figure 1 of another lock bolt for axial force measurement, and Figure 4 is an enlarged sectional view taken along the line ■-■ in Figure 1. A front view of the lock bolt for axial force measurement, Fig. 5 is an enlarged sectional view taken along the line V-V in Fig.
The figure is a front view of another conventional lock bolt for axial force measurement.
The figure is an enlarged sectional view taken along the line ■-■ in Fig. 6, Fig. 8 is a front view showing an example of the lock bolt for axial force measurement according to this invention, and Fig. 9 is an enlarged sectional view taken along the line IX-IX in Fig. 8. FIG. S...Strain gauge, 11...Bolt body, 12...Split groove, 13...Lead wire.

Claims (1)

[Scope of utility model registration request] A split groove running from the outer surface of the bolt body toward the center is formed along the length of the bolt body, and a strain gauge connected to a lead wire is attached to the opposite inner surface of the split groove by inserting the lead wire into the split groove. A lock bolt for measuring axial force, characterized by the following: