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1. Introduction
General centre-holed grouting rock bolt is a new supportive medium for tunnel crowned arch、sidewall、upward arch、side slope、side wall of deep foundational hole installing. The rock bolts make effect together with shot-Crete ，and come into being a part of bearing the weight of annulus、soil nailed wall、minitype pegs、rock anchor、bearing capacity、acting on tunnel、side slope and deep foundational hole. Furthermore, the rock bolt can be also used in digging face as a temporary supportive way .The bolt is widely used in supporting the railway, road, deep foundation and tunnel, which can meet the pull requirements of 100~250kn .It can be constructed together with drill set.
2. Component of products
General centre-holed grouting rock bolt is composed of alloyed rod body、splint、screw cap、vent-pipe、grouting-stop stopper and rubber hammer. （See Fig.）
The alloyed rod body is the full screw thread rod body which is made of raw and proceeds material.
Splint and screw cap ：They are pre-stressed exterior and locked fastening pieces .There are air-bleed holes attached to the guide pins.
vent-pipe：It is fixed on trailing bar by the air-bleed hole of the splint， with one end inserted into the bore, and the other outside. It can be used collaborated with the centre-holed grouting rock bolt, according to the way of installation.
Grouting-stop stopper and rubber hammer: They are the subsidiary materials made of robber, which play a great part. Not only can they enhance the effectiveness of grouting, but also prevent the dust going into the body while the bolt being inserted into the bore, which may cause weak effect and the grout or jam pour out of the bore.
3. The specification and technical parameters
|
Specification
（General centre-holed grouting rock bolt）
|
Mechanics Index |
|
Utmost tension resistance |
Nominal external
diameter |
Diameter for drilling |
Screwing spiral direction |
Standard length |
Type-
depth max |
|
180KN |
mm |
mm |
|
m |
m |
|
D25a |
180 |
25 |
42 |
Left |
2.5/3/3.5/4/4.5/
5/5.5/6/8/10 |
– |
|
D25b |
150 |
25 |
42 |
|
D25c |
120 |
25 |
42 |
|
D27a |
240 |
27 |
42 |
|
D27b |
200 |
27 |
42 |
|
D27c |
180 |
27 |
42 |
|
D29a |
290 |
29 |
46 |
|
D29b |
210 |
29 |
46 |
|
D32a |
290 |
32 |
50 |
|
D32b |
250 |
32 |
50 |
|
D38a |
440 |
38 |
75 |
|
D38b |
420 |
38 |
75 |
|
D50a |
640 |
50 |
110 |
|
D50b |
580 |
50 |
110 |
|
*The date of the table can be changed for meeting the clients’ requirement |
4. Technical code for construction
（1）. General centre-holed grouting rock bolt is mainly composed of centre-holed rock bolt body, grouting-stop stopper, splint, vent-pipe and nut，they can be used for rock support project，especially，used for anchor project of supporting the top of the underground work by middle and long.
（2）.The depth and diameter of drilling should meet the requirement of design，when drilling the hole.
（3）.Before installing the rock bolt, check the middle bore and find whether it is smooth. Please clean up in time if the extraneous matters exist.
（4）. After the bolt reaching the depth，clean the bore by water and air.
Then install the grouting-stop stopper, splint and nut for temporary fastness until the water and air return to orifice.
（5）.Grout should use neat cement paste and cement paste（Ratio：1：1）.Advised to increase the ratio of water and cement for 0.4-0.5, the diameter of gravel should not be larger than 0.1mm, when using cement mortar.
（6）.Grouting from the middle bore，fastening the nut when the intensity up to 5.0 Map
（7）. The method of the installing the General centre-holed grouting rock bolt should conform the process flow ：Drilling——Cleaning——Installing rock bolt for grouting and re-grouting——Fastening and end processing.
5. Advantages of the products：
1. It had carried out the function of grouting tubule by centre-holed designing.
2. The press grouting can be carrying out when grouting is full.
3. The character of centering is good.
4. Easy for installing |
