How to detect whether there are anchors in the initial support of the tunnel

The non-destructive testing of the initial support can be achieved by using geological radar or acoustic detection, but only the number and length of the anchor can be detected, and the construction quality of the anchor cannot be detected. The construction quality of the bolt is mentioned in the specification to detect the pull-out force, but generally a bolt can meet the requirements of pull-out resistance as long as there is 50-100cm anchoring agent on the head, so the compactness of the anchorage is very important.

The bolts are generally in a group of 3, each about 30cm, according to the size of your tensile machine. The test items are: diameter, wall thickness, yield force, ultimate tensile strength, yield strength (calculation), ultimate tensile strength (calculation).

Bolt: bolt, English "bolt"; "bolting"; "anchor" is the most basic component of roadway support in modern coal mines, he reinforces the surrounding rock of the roadway, so that the surrounding rock supports itself. Now bolts are not only used in mines, but also in engineering technology, to strengthen slopes, tunnels, dams.

As one of the main forms of support for underground engineering and rock slope, bolts play an important role in the maintenance of the stability of civil engineering, especially in the jointed fractured rock mass, the reinforcement effect of the bolt on the rock mass is very obvious.

Now it is all acoustic detection, large-area detection is not yet mature, and the inspection is generally carried out one by one, which can check the length and fullness of the anchor. Generally, it is a random inspection, and it is really necessary to check it more seriously, and it is estimated that there are few qualified.

It is very dangerous for the landlord to say this kind of thing, but generally no one dares to say this, which will betray a lot of managers! Generally, it is to check the pulling force of the bolt, if it really comes to the extent of inspection, it is estimated that it will have to chisel shotcrete!

The principle of acoustic detection method: emit a sound wave pulse at the outer end of the bolt rod, which propagates in the form of pipeline waves along the rod body leakage steel bar, and reflects after reaching the low end of the steel bar. Kiss for you to find out, what does it mean to break the tunnel bolt, and the end can receive this reflected wave.

If the outer part of the steel bar is densely and fully held by the cement mortar, and the mortar is bonded with the surrounding rock mass, the sound wave continuously diffuses from the steel bar to the rock mass through the cement sand town in the propagation process, and the energy loss is very large, and the amplitude of the reflected wave measured at the outer end of the rod body is very small or even undetectable; If there is no mortar grip and only an empty rod, the sound wave only propagates in the steel bar, the energy loss is not large, and the amplitude of the reflected wave received is larger; If the grip mortar is not dense and there are cavities or missing in the middle, the amplitude of the reflected wave is between the first two. Therefore, the fullness of cement mortar can be judged according to the amplitude of the reflected wave, and the length of the anchor rod can be determined according to the time difference between the reflected wave and the incident wave. The above is all my reply, I hope it can help you, and I wish you a happy life

1. The anchoring force of the anchor rod can be measured with the bolt tension meter. Generally, it is enough to measure the design anchorage force, not to do the damage test.

2. The "pull-out force" you are talking about is generally called "pull-out force". Generally, it refers to the force that pulls the bolt out from the anchorage. In order to measure the pull-out force, it is necessary to do a failure test, and the measured value is MPa, which can be converted to kn.

3. Anchoring force refers to the maximum value of the anchoring agent cementing the anchor rod and the surface of the coal and rock. Generally, only the design anchorage force is discussed. The maximum anchorage force is the ultimate pull-out force measured by the failure test, that is, the force used to pull the bolt off from the anchor with a bolt tension gauge.

For the concept of anchoring force and pull-out force, you can check the design specifications for bolt support. The concepts in the specification are more accurate.

From a rational point of view, the force generated by cementing the anchor and the roadway wall together with an anchoring agent is called the anchoring force, and the size of the anchoring force can only be obtained by the failure test. The pull-out force is the maximum force that is used to measure the bolt from the anchor with a bolt tension gauge. Therefore, for the same anchored anchor, the size of the anchoring force and the pull-out force are the same, but it only refers to the fixed force, and the unit is kn; One finger pulls down the force in mpa.

1. Anchor material.

1) Tensile strength.

The sample is intercepted from the raw material or the finished anchor, stretched on a tensile testing machine, and the mechanical properties of the material are tested to determine whether it meets the engineering requirements and the mold is destroyed late.

2) Ductility and elasticity.

During the inspection, on-site bending or hammering can be used to observe its plastic deformation.

2. Specifications of the rod body.

The diameter of the bolt body must match the design and can be measured with a caliper or ruler.

3. Processing quality.

When inspecting, the size of each part should be measured firstly, and then the welding quality of the welded parts should be checked; For the wire part, the quality of the silk should be checked to observe whether there is eccentricity.

M-7 bolt detector is used to detect the filling degree of mortar bolt mortar

According to the design parameters and the type of surrounding rock, 3-4 groups of standard anchors are set, with 1-2 bolts in each group;

Determination of the amplitude of the reflected wave on these standard bolts for different mortar fullness (as a standard for detecting other bolts);

These standard values are stored in the detector prior to other bolt tests;

Detect the compactness of the sand fiber and slurry bolt, and the code instrument will automatically display the length of the measured bolt and the mortar compactness grade.

The number of meters of tunnel extension refers to the amount of physical work that occurs along the center line of the tunnel for every 1 meter advanced.

Generally speaking, most of the tunnels are designed in sections according to the condition of the surrounding rock, and then converted into linear meters.

For example, in the tunnel section of the surrounding rock of a tunnel IV, the design length of the initial supporting arch bolts, in a total of 100 meters, a total of 1208 supporting bolts are designed. In this way, the equivalent of every linear meter is the root.

Moreover, the bolt design of the tunnel is not simply the system bolt (construction according to the designed fixed position), but also the design of a part of the local bolt, that is, the corresponding bolt construction is carried out on site according to the special conditions of the surrounding rock. Local anchors are calculated according to the sectional design and measurement method.

The specific bolt layout also needs to refer to the design drawings, and cannot be calculated according to the engineering quantity.

Drilling difficulty: due to the narrow operating space, the construction completes a 4m deep bolt drilling, and it is necessary to replace the drill bit 3 times or carry out 3 cycles, that is, first use the 2m length of the drill hole to drill 2m and then change to the 3m length of the drill pipe, and finally use the 4m length of the drill pipe final hole, not only the work efficiency is low, but also the problem of slag drop in the hole can not be overcome.

Difficulty in filling the early strength cement anchorage roll: due to the broken surrounding rock of the tunnel and the rough hole wall, the strength of the early strength cement anchorage roll is reduced after water absorption, coupled with the problem of slag falling in the hole, it is difficult to fill in place, and the anchor roll is easy to break and break.

Difficulty in installation of bolts: due to the fragmentation of the surrounding rock of the tunnel, coupled with the collision when filling the early strength cement anchor roll, it is easy to drop slag and block in the bolt borehole, so that the bolt installation is not in place or cannot be installed.

Difficulty in installing the backing plate: because the side wall anchor rod body is mostly made of threaded steel bars with a diameter of 22mm, the tail end can not be directly installed with the backing plate, and the tail end of the specially processed threaded buckle needs to be welded, and the quality is difficult to guarantee.

Before the installation of tunnel bolts, the contents of the inspection should be carefully concealed.

1) The model, specification and variety of bolt materials should meet the design requirements, and the accessories should be matched.

2) The hole position, hole diameter, hole depth and layout of the anchor wide chain rod should meet the design requirements.

3) There should be no stagnant water in the hole, and the rock powder should be blown clean.

4) The bolt rod body should be straightened, rust removed, and oil stains removed.

5) The standard and bright thread at the outer end of the anchor rod should be effective, check one by one and test assemble with the standard nut.