MT/T 5015-1996Code for quality inspection of engineering supported by bolting and shotcrete (English PDF)

2.1 General provisions

2.1.1 This chapter is applicable to concrete strength detection using shotcrete support in coal mine tunnel engineering.

2.1.2 The strength testing of shotcrete should adopt the point load test method or the pull-out test method, and the sprayed plate cutting method or chisel cutting method can also be used.

Do not use the test block method.

2.1.3 When using the point load test method or the pull-out test method to measure the strength of shotcrete, the layout of the test points should meet the following requirements.

a) The concrete surface around the measuring point should be flat and avoid honeycombs and holes;

b) There should be no reinforced or embedded iron in the concrete within 60mm around the measuring point;

c) The distance between two adjacent measuring points should not be less than 250mm, and the distance from the edge of the concrete should not be less than 150mm;

d) The thickness of the concrete at the test site should not be less than 50mm.

2.2 Point load test method

2.2.1 The point load test method is to use a concrete drill to drill a cylindrical core sample from the concrete spray body and use a point load meter to test its point load.

Load strength, and then determine the concrete strength detection method based on the point load strength.

2.2.2 The point load test method consists of two parts. sampling and point load test. The sampling section includes sampling rigs and diamond thin-wall drill bits, and with water cooling system. The point load test device includes a manual oil pump, a hollow oil cylinder, a loading cone, a pressure measuring device and an oil pipeline. Commonly used for equipment, see Appendix A of this regulation.

2.2.3 The point load test method for detecting the strength of shotcrete should meet the following requirements.

a) Sampling.

1) The machine should be placed smoothly during sampling to avoid impact and vibration;

2) The core sample should be complete, the diameter of the core sample should be greater than 1.5 times the diameter of the coarse aggregate of sprayed concrete, and the length of the core sample should not be less than 1.1 times.

b) Point load test.

1) The loading point should be located in the middle part of the core sample length, and the distance from either end should not be less than the core sample radius.The line connecting the two loading points should pass through the section circle.

Heart, that is, it must be loaded radially;

2) The location of the loading point should be the smooth and complete surface of the core sample, and avoid the re-spraying surface, rupture surface and air holes;

3) The core sample should be pressurized slowly and uniformly, and the loading speed should be less than 0.2MPa/s.

2.2.4 The point load test data obtained by one of the following situations must be discarded.

a) The core sample is damaged along the multiple spray surface or the interface between the spray layer and the surrounding rock;

b) the core-like fracture surface does not pass two loading points, or passes only one loading point;

c) the angle between the core-like rupture surface and its axis is less than 45 °;

d) There is a significant difference between the test data and the appearance characteristics of the core sample.Under normal circumstances, the appearance characteristics of the shot concrete core sample are related to the test data See Appendix B of this Regulation.

2.2.5 Load strength I of shotcrete core sample point, calculated according to formula (2.2.5).

(2.2.5)

Where L

P --- failure load (N);

Af --- area of core-like failure surface (mm2);

I --- point load strength (MPa);

2.2.6 The compressive strength of shotcrete shall be calculated based on the point load strength of shotcrete according to formula (2.2.6).

f'cu, i = ab · Ii (2.2.6) where.

f'cu, i --- the compressive strength value (MPa) of the sprayed concrete core sample at the i-th measuring point, accurate to 0.05MPa;

Ii --- point load strength of sprayed concrete at the i-th measuring point (MPa);

a --- constant term;

b --- regression coefficient.

Formula (2.2.6) is a general formula for calculation, and the specific strength calculation formula can be established according to the method described in Appendix C of this regulation.

2.2.7 The point load method for testing the strength of shotcrete can be recorded in accordance with the requirements of Appendix D of this code.

2.3 Pull-out test method

2.3.1 The pull-out test method refers to drilling, grooving and installing a reamer in a concrete spray body to perform a pull-out test, and the spray is determined according to the limit pull-out force.

Compressive strength of shot concrete (see Figure 2.3.1).

Figure 2.3.1 Schematic diagram of the pull-out test method

2.3.2 The pull-out test device should include drilling, grooving, and pulling out three parts of the machine. For common implements, see Appendix A of this code.

2.3.3 The pull-out test shall meet the following requirements.

a) When drilling, the drill bit should be kept perpendicular to the concrete surface at all times.

mm hole wall must be smooth;

b) If the surface of the sprayed concrete is not flat, the surface treatment around the hole location should be flat before drilling;

c) Cut a circular groove at a distance of 25 mm from the hole in the borehole (the distance from the plane of the groove adjacent to the hole to the hole).

d) The pressure for pulling out should be slow and uniform, and the loading speed should be less than 0.2MPa/s;

e) The pull-out test should be carried out until the concrete has just started to break, and the oil pressure gauge reading no longer increases.

2.3.4 After the pull-out test, the damage of the concrete at the test points should be checked. Under normal circumstances, the concrete failure surface should be a basically regular conical surface.

2.3.5 Test data obtained from one of the following situations must be discarded;

a) no damage occurred;

b) only a small part of the concrete in the bearing ring or bearing point is damaged;

c) the ring groove is irregular, or the distance between the groove and the concrete surface is less than;

d) After pulling out the damage, the damage surface is a very irregular conical surface;

e) The meter reading is obviously abnormal.

2.3.6 According to the pull-out force Fi of the sprayed concrete at the measurement point, the compressive strength value of sprayed concrete f'cu, i can be calculated according to formula (2.3.6).

f'cu, i = ab · Fi (2.3.6) where.

f'cu, i --- the compressive strength (MPa) of shot concrete at the i-th measuring point, accurate to 0.05MPa;

Fi --- pullout strength of sprayed concrete at the i-th measuring point (kN);

a --- constant term;

b --- regression coefficient.

Equation (2.3.6) is the general formula for calculating the compressive strength of shotcrete. The specific calculation formula can be established according to the method described in Appendix C of this procedure.

2.3.7 The strength of shotcrete measured by the pull-out method can be recorded in accordance with the requirements of Appendix E of this code.

2.4 Test procedures

2.4.1 According to the type of project and the size of the project, determine the number of sprayed concrete strength check points according to Table 2.4.1.

2.4.2 The random sampling method is used to determine the location of the checkpoint. For details, see Appendix F of this Regulation.

Table 2.4.1 Number of checkpoints

Number of project types Quantity check points 1 not less than 1 every 20 ~ 30m

2 Not less than 1 every 30 ~ 50m in inclined wells, flat concrete and roadways 3 1000m3 or more but not less than 5 500 ~ 1000m3 not less than 3 500m3 or more

4.1 General provisions

4.1.1 This chapter applies to the installation quality of anchor brackets, which are supported by bolts, the distance between bolts, the row spacing, the depth of the bolt holes, and the angle Quality inspection of anchor rod exposed length.

4.1.2 The main indicators and requirements of this chapter are based on the "Technical Specifications for Bolt Shotcrete Support", Fan "and" Quality Inspection and Evaluation Standards for Coal Mine Tunnel Engineering ".

4.1.3 The number of checkpoints for each test item described in this chapter is determined in accordance with Table 4.1.3, but the number of checkpoints at each time should not be less than 3.

Table 4.1.3 Anchor rod installation quality check point spacing

Project type. vertical shaft, inclined shaft, flat shaft, roadway, chamber Checkpoint distance (m) >15 >20

4.1.4 The quality assessment of each test item described in this chapter shall be in accordance with the relevant provisions of the current "Quality Inspection and Evaluation Standards for Coal Mine Lane Engineering" carried out.

4.1.5 Anchor installation quality inspection may be recorded in accordance with the requirements of Appendix H.

4.2 Anchor pallet installation quality inspection

4.2.1 Anchor pallet installation quality inspection, for unsprayed concrete, pull on the spot, observe and verify; for sprayed concrete Process, spot check construction inspection records at checkpoints.

4.2.2 The installation quality of the anchor plate is checked by the team and row by row, and records are made; during the middle or completion acceptance, according to the type of project, according to this table the provisions of 4.1.3 determine the number of checkpoints.

4.2.3 At each inspection point, inspect the installation quality of the previous row of anchor brackets.

4.2.4 Anchor pallet is firmly installed and basically adheres to the wall surface, which is judged to be qualified if it is not loose; Anchor pallet is firmly installed, adheres to the wall surface, and has no contact Wedges were judged as excellent.

4.3 Anchor Rod Distance and Row Distance Detection

4.3.1 The allowable deviation of the bolt spacing and row spacing is ± 10mm.

4.3.2 Before the anchor is not covered with shotcrete, it can be directly detected; after the anchor is covered with shotcrete, metal anchors should be detected with anchors the instrument detects and calibrates its position.

4.3.3 The bolt detector used shall meet the following requirements.

a) The maximum detection depth is not less than.200mm;

b) The positioning accuracy is ± 10mm.

4.3.4 In the bolt and shotcrete support project laid with a metal mesh, an anchor detector capable of distinguishing the metal mesh and the bolt shall be used to detect the distance between Row spacing.

4.3.5 According to the type of project, determine the number of check points for bolt spacing and row spacing according to the regulations in Table 4.1.3 of this code.

4.3.6 Detect the four adjacent anchors arranged in a quadrangle at each checkpoint, and measure their spacing and row spacing.

4.3.7 The spacing and row spacing of the four adjacent anchors at the checkpoint are in accordance with the provisions of Article 4.3.1 of this code, and the checkpoint is qualified.

4.4 Anchor hole depth and angle detection

4.4.1 The allowable deviation of the depth of the anchor hole is 0 ~ 50mm; the allowable deviation of the direction of the anchor and the contour line of the shaft or the stratification of the rock stratum is <=15 °.

4.4.2 During the construction process, the team and team will conduct row-by-row inspections and make records; during the middle or completion acceptance, it shall be determined in accordance with the provisions of Table 4.1.3 of this Code.

Number of checkpoints and spot check of construction inspection records.

4.5 Anchor Bar Exposed Length Detection

4.5.1 The exposed length at the end of the anchor rod shall meet the requirements in Table 4.5.1.

Table 4.5.1 Allowable external lightning bolt length (mm)

Category Allowed Exposed Length with pallet exposed pallet<=50 no pallet <=50 Explosive materials storeroom, anchor shotcrete roadway0

4.5.2 According to the type of project, determine the number of inspection points in accordance with the provisions of Table 4.1.3 of this code.

4.5.3 The maximum exposed length of the row of anchor rods in front of the ruler.

5.1 Detection methods

5.1.1 Anchor pull test is used to detect the pull-out resistance of the anchor, and the quality of the pull-out resistance and the firmness of the installation is evaluated based on the test results.

5.1.2 Anchor tension meter shall meet the following requirements.

a) The maximum working load is not less than 70kN;

b) working stroke is not less than 10mm;

c) The force-measuring device should use a standard precision pr...