Open-pit coal mine burnt rock hole protection slurry, preparation method and application thereof

Abstract

The present application relates to the technical field of geological exploration, and specifically discloses a kind of open coal mine burnt metamorphic rock blast hole hole protection slurry and its preparation method and application, to drilling wall protection bentonite B as bentonite raw material is prepared into the slurry with the concentration of 120-140kg / m 3 The stirring speed is 900rpm-1100rpm, and the stirring time is 14-15min, then the fibrous material is added in the slurry, the amount is 1-3kg / m 3 , obtain hole protection slurry. The hole protection slurry prepared by the present application has good hole protection effect on open coal mine burnt metamorphic rock blast hole.

Description

Technical Field

[0001] This invention relates to the field of geological exploration technology, specifically to a hole protection grout for burnt rock blast holes in open-pit coal mines, its preparation method, and its application. Background Technology

[0002] Drilling in special formations often encounters borehole collapse, rockfall, and various degrees of obstruction, stuck drill bit, buried drill bit accidents, and borehole diameter reduction or over-diameter issues. Special formations are those where borehole collapse and obstruction occur to varying degrees during the drilling process. We collectively refer to these special formations as special formations. Therefore, in practice, employing various types of drilling mud is the primary means of solving drilling problems in complex formations.

[0003] Among the many types of drilling mud, whether for well drilling, geological exploration drilling, or borehole blasting, bentonite is used extensively as the main raw material in drilling mud preparation. This is used to protect the borehole wall, carry back cuttings, and cool the drill bit. Bentonite is a basic material for drilling mud, with an annual global consumption of approximately 1.5 million tons, and my country's consumption being 150,000 to 200,000 tons. Currently, the domestic and international production of high-grade bentonite for drilling fluids far exceeds the demand. Bentonite is the most commonly used borehole protection material, and its production process is relatively simple and economical.

[0004] Compared to geological boreholes, open-pit coal mine burnt rock blast holes have smaller diameters and different geological conditions, increasing the difficulty of borehole protection for these small-diameter holes. Spontaneous combustion of the coal seam causes the overlying and surrounding rocks to burn and bake, making the originally plastic rock brittle and easily broken, resulting in a fragmented rock mass with structures in the form of plates, plates, fragments, wedges, and rhomboids. The closer to the roof of the burning coal seam, the more molten the rock appears, characterized by locally developed micropores. Due to the fragmented and unstable rock mass in the burned area, the borehole wall collapses as the drill rod is lifted, making it impossible to form normal blast holes for charging and blasting, resulting in a low borehole formation rate and poor blasting effect. This low borehole formation rate leads to large areas of blasting without boreholes, making charging and blasting impossible, resulting in large areas of "hardened walls" and "umbrella-like" structures after blasting.

[0005] Bentonite provides the basic properties of drilling mud; therefore, the quality of bentonite directly affects the performance and consumption of other chemical treatment agents, and even influences borehole collapse and drilling speed. In actual borehole protection, when the protection slurry is injected into the borehole, drill cuttings inevitably mix into it, altering the slurry's properties and affecting its effectiveness. However, most existing borehole protection slurry preparations do not consider the impact of drill cuttings on the protection effect. Summary of the Invention

[0006] To address the problem of hole protection for blast holes in sintered rock in open-pit coal mines, this invention provides a hole protection slurry for sintered rock blast holes in open-pit coal mines, its preparation method, and its application. The hole protection slurry prepared by this invention has a good hole protection effect on blast holes in sintered rock in open-pit coal mines.

[0007] This invention provides a drilling slurry for sealing boreholes in sintered rock in open-pit coal mines, its preparation method, and its application. The slurry uses bentonite B (for borehole wall protection) as the bentonite raw material, which is mixed with water and stirred to prepare a slurry with a concentration of 120-140 kg / m³. 3 The slurry is stirred at a speed of 900 rpm-1100 rpm for 14-15 minutes. Then, fibrous material is added to the slurry at a rate of 1-3 kg / m³. 3 To obtain the pore protection slurry.

[0008] Furthermore, the concentration of the slurry is 140 kg / m³. 3 .

[0009] Furthermore, the stirring time is 15 minutes.

[0010] Furthermore, the amount of fibrous material added is 3 kg / m³. 3 .

[0011] Furthermore, the fibrous material is short glass fiber filaments.

[0012] Furthermore, the short glass fiber filaments have a diameter d = 0.85 mm to 2.85 mm and a length L = 20-30 mm.

[0013] The present invention also provides a pore-protecting slurry prepared by the above preparation method.

[0014] Furthermore, the pore-protecting slurry has a viscosity of 27.82s, a relative density of 1.57, a pH value of 9.0, a sand content of 0.50%, and a colloid content of 99%.

[0015] The present invention also provides the application of the aforementioned hole-protecting slurry in hole protection of sintered rock blast holes in open-pit coal mines.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] 1. The hole-protecting slurry prepared by this invention has a good hole-protecting effect on blast holes in sintered rock in open-pit coal mines. The optimal stirring time for the hole-protecting slurry is 15 min, the viscosity is 27.82 s, the relative density is 1.57, the pH value is 9.0, the sand content is 0.50%, and the colloid content is 99%. The viscosity, colloid content, and other indicators of the slurry prepared under the conditions of stirring speed of 900 rpm-1100 rpm and stirring time of 15 min are significantly better than other parameters.

[0018] 2. The concentration obtained in this application is 140 kg / m³. 3 Adding glass fiber filaments to the slurry significantly improves its borehole protection effect. It minimizes the impact of drill cuttings on the slurry during borehole protection. The initial mud cake formed by the fiber-infused slurry can adhere to larger rock fragments, and from the initial state to the formation of the dry mud cake, the rock fragments do not slide or fall off. The detached dry mud cake has densely and evenly distributed fiber filaments, making it difficult to tear into fragments. The borehole protection effect after adding glass fiber filaments is very significant. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is an external view of the drilling wall bentonite used in this invention.

[0021] Figure 2 The effect of fine rock powder of different particle sizes on the colloidal content of the hole protection grout;

[0022] Figure A shows the effect of <200 mesh rock powder on the colloidal content of the hole protection grout.

[0023] Figure B shows the effect of <100 mesh rock powder on the colloidal content of the hole protection grout.

[0024] Figure C shows the effect of rock powder <60 mesh on the colloidal content of the hole protection grout.

[0025] Figure 3 This is a schematic diagram illustrating the principles of different stages of hole protection.

[0026] Figure 4 The actual hole protection effect of hole protection slurry with different concentrations;

[0027] Figure A represents a concentration of 120 kg / m³. 3 The actual hole protection effect of the hole protection slurry;

[0028] Figure B shows a concentration of 140 kg / m³. 3 The actual hole protection effect of the hole protection slurry.

[0029] Figure 5 This is an appearance diagram of the short glass fiber filaments used in this invention.

[0030] Figure 6 This invention relates to the effect of short glass fiber filaments on the hole protection effect;

[0031] Figure A shows the effect of not adding short glass fiber filaments on hole protection;

[0032] Figure B shows the effect of adding short glass fiber filaments on hole protection. Detailed Implementation

[0033] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention. Unless otherwise specified, the materials, reagents, and methods used in the embodiments of the present invention are all conventionally available and commercially available.

[0034] The test methods involved in the following embodiments are as follows:

[0035] 1. Sand content test of hole protection grout

[0036] Sand content refers to the percentage of sand in the borehole slurry that cannot pass through a 200-mesh sieve by volume. The sand content of the borehole slurry is commonly determined using a NA-1 type mud sand content meter.

[0037] The specific experimental steps are as follows:

[0038] a. Fill the hole protection slurry to the mark marked "mud" on the measuring tube, add water to the mark marked "water", block the tube opening and shake it;

[0039] b. Pour the mixture into the filter cartridge, discard the liquid that has passed through the filter screen, add clean water into the test tube, shake, and then pour it back into the filter cartridge. Repeat this process until the test tube is clean.

[0040] c. Rinse the sand obtained from the screen with clean water to remove any residual mud;

[0041] d. Fit the funnel into the filter cylinder, then slowly invert it and insert the funnel into the measuring tube. Use clean water to flush all the sand attached to the screen into the tube;

[0042] e. After the sand settles, read the percentage content of the sand.

[0043] 2. Test of colloid content in the grout for hole protection

[0044] Colloidal ratio is a rough measure of the dispersion and hydration of clay particles in the grout and their suspension.

[0045] Test method: Wash and dry a 1000ml glass graduated cylinder, and place it on a flat surface. Add 1000ml of the prepared test sample (slurry) to the glass graduated cylinder. After standing for 24 hours, the slurry in the glass graduated cylinder will separate into two layers: the upper layer is clear water, and the lower layer is slurry. Read the scale reading at the interface between the lower slurry and the upper water, and express it as a percentage. This is the colloidal content of the slurry sample.

[0046] Precautions: A sample label should be affixed to the measuring cylinder to prevent confusion in numbering; when pouring the slurry into the measuring cylinder, avoid the slurry sticking to the cylinder wall, which will affect the reading; during the settling process, avoid moving, shaking, or vibrating the cylinder.

[0047] 3. Determining the stirring conditions

[0048] (1) Viscosity test of hole protection slurry

[0049] Viscosity is a property of a liquid that hinders its relative flow; it is the result of friction between liquid molecules and solid particles within the liquid, and is measured in seconds (s). The viscosity of the pore-protecting slurry was determined using a 1006 funnel viscometer.

[0050] ①The specific operation method is as follows:

[0051] a. Rinse the viscometer funnel, sieve, and 500 / 700ml measuring cup thoroughly with water, both inside and out, and then wipe them dry with a dry cloth. Place the 500ml measuring cup below the outlet tube of the funnel;

[0052] b. Attach a sieve to the top of the funnel and use a 1L measuring cup to take 700ml of well-mixed mud;

[0053] c. Block the outlet tube with your left index finger, pour 700ml of mud into the viscometer funnel with your right hand, pick up the stopwatch, reset the stopwatch to zero, release your left finger and start the stopwatch, stop timing when the 500ml measuring cup is filled, and record the test time T seconds.

[0054] d. Calculate the mud viscosity η

[0055] η = K·T

[0056] Where: η—mud viscosity, seconds (s);

[0057] T—Mud viscosity test value, seconds (s);

[0058] K—Instrument calibration coefficient.

[0059] e. Determine the instrument calibration coefficient K. Viscometers require frequent calibration before and during use to determine the calibration coefficient K. The standard filtration time for a viscometer is 15 seconds, i.e., K = 1. The calibration method is to pour 700 ml of clean water into a funnel and allow 500 ml to flow out, following the same procedure as testing mud. If the filtration time exceeds 15 seconds, the outlet tube should be checked and cleaned with a cloth. A filtration time of 15 ± 1.0 seconds is acceptable for the viscometer; beyond this range, the instrument is unusable.

[0060] The formula for calculating the correction factor K is as follows:

[0061]

[0062] Where: K—instrument calibration coefficient

[0063] E—Standard viscosity of water

[0064] T—Measured viscosity of water

[0065] ② Experimental equipment

[0066] The experimental equipment required for testing the viscosity of the grout mainly includes: a 1006 funnel viscometer; 500 / 700ml measuring cups; 1000ml measuring cups; a stopwatch; and a pH test pen.

[0067] (2) Pore protectant density test

[0068] Density refers to the mass of a unit volume of pore-protecting fluid, measured in g / m³. 3 The density of the drilling slurry was measured using an NB-1 type mud hydrometer.

[0069] ① Before testing the density of the hole-protecting slurry, the weighing meter must be calibrated. The calibration method is as follows:

[0070] a. Clean the mud hydrometer and place it on a flat surface;

[0071] b. Fill the mud cup of the hydrometer with deaerated distilled water (clean water can be used on site), tighten the lid, and let the excess water overflow from the center hole of the lid. Then wipe the surface of the instrument clean.

[0072] c. Gently place the main blade of the hydrometer onto the main blade pad on the base;

[0073] d. Move the rider on the lever to the 1.0 mark on the scale. At this point, the bubble level on the instrument lever should be centered. Otherwise, the instrument is out of alignment and needs to be readjusted.

[0074] e. Adjustment method: Add or remove the metal particles inside the balance cylinder at the end of the lever scale to make the horizontal bubble in the middle position.

[0075] ② The density of the borehole protection slurry was tested using an NB-1 type mud hydrometer, as follows:

[0076] a. Calibrate the mud hydrometer;

[0077] b. Fill the mud cup with the slurry to be tested, cover the cup with the lid, and let the excess slurry drain out from the center hole of the lid;

[0078] c. Press the center hole of the cup lid with your finger, clean the mud off the surface of the instrument, and wipe the surface dry.

[0079] d. Gently place the main blade of the hydrometer on the main blade pad of the base;

[0080] e. Move the rider on the scale of the lever. When the horizontal bubble is in a horizontal position, read the scale value on the right side of the rider, which is the density of the slurry for the hole protection.

[0081] ③ Experimental equipment

[0082] Experimental equipment required for testing the density of the grout.

[0083] Example 1

[0084] A hole-protecting grout for burnt rock blast holes in open-pit coal mines, its preparation method, and its application.

[0085] This embodiment is a protective hole for drilling through the rock steps in the sintered rock area of ​​Dananhu No. 2 Mine, with a hole diameter of 200mm and a hole depth of 10.5m.

[0086] I. Selection of borehole protection materials in sintered rock areas

[0087] 1. Selection of Bentonite for Drilling Wall Protection

[0088] The properties of the drilling wall bentonite were tested, and the results are shown in Table 1. The appearance of this wall-supporting bentonite is as follows: Figure 1 As shown;

[0089] The drilling wall bentonite was produced by Haixin Bentonite Co., Ltd. of Hoboksar Mongolian Autonomous County.

[0090] Table 1. Test results of the properties of the bentonite selected for drilling wall protection in this invention.

[0091]

[0092] This invention uses drilling wall protection bentonite produced by Haixin Bentonite Co., Ltd., which has low sand content and high colloid content (over 99%), as the test material for borehole protection at Dananhu No. 2 Mine.

[0093] II. Preparation of Hole Protection Slurry

[0094] 1. Determination of technical parameters in the preparation process of the grout for hole protection

[0095] The viscosity of the pore-protecting fluid is related to the stirring speed, slurry concentration, sand content, pH, and stirring time.

[0096] (1) Determination of minimum stirring speed

[0097] The effect of different stirring speeds on the viscosity of the hole-protecting slurry is shown in Table 2.

[0098] Table 2. Effect of different stirring speeds on the viscosity of the grout.

[0099]

[0100]

[0101] As shown in Table 2, for the same concentration of borehole protection slurry, the viscosity increases with increasing stirring speed, and this increase is related to the slurry concentration. As the slurry concentration increases, the stirring speed required for the viscosity to stabilize decreases. Once the mixer speed reaches 1100 rpm, the slurry viscosity no longer increases with further increases in stirring speed. When the concentration is greater than 100 kg / m³... 3 When the stirring speed reaches 900 rpm or higher, the viscosity of the grout is close to its maximum viscosity. Considering that the actual stirring speed is constrained by various factors during field application, and the high concentration of the grout on site, the minimum stirring speed should be no less than 900 rpm. Simultaneously, a variable frequency motor is used to gradually increase the stirring speed to avoid damage to the motor from high-speed start-up of the high-concentration grout.

[0102] (2) Determination of minimum stirring time

[0103] The effects of different concentrations and different stirring times on the viscosity of the grout (viscosity values ​​are the average of three experimental results) are shown in Tables 3-14.

[0104] Table 3 Concentration 60 kg / m³ 3 Effect of different stirring times on the viscosity of the hole protection slurry

[0105] Stirring time 4min 5min 6min 7min 8min 9min Time (s) 15.42 15.67 16.10 15.75 15.88 15.87 Viscosity (s) 15.31 15.56 15.99 15.64 15.77 15.76

[0106] Note: pH = 8.8, water temperature 20℃, water transit time is 15.1 sk = 0.993.

[0107] Table 4 Concentration 65 kg / m³ 3 Effect of different stirring times on the viscosity of the hole protection slurry

[0108] Stirring time 4min 5min 6min 7min 8min 9min Time (s) 15.88 16.00 16.10 16.13 16.16 16.15 Viscosity (s) 15.77 15.89 15.99 16.02 16.05 16.04

[0109] Note: pH = 8.8, water temperature 20℃, water transit time is 15.1 sk = 0.993.

[0110] Table 5 Concentration 70 kg / m³3 Effect of different stirring times on the viscosity of the hole protection slurry

[0111] Stirring time 6min 7min 8min 9min 10min Time (s) 16.00 15.78 16.16 16.26 16.26 Viscosity (s) 15.88 15.67 16.05 16.15 16.15

[0112] Note: pH = 8.8, water temperature 20℃, water transit time is 15.1 sk = 0.993.

[0113] Table 6 Concentration 75 kg / m³ 3 Effect of different stirring times on the viscosity of the slurry

[0114] Stirring time 6min 7min 8min 9min 10min Time (s) 16.21 16.73 16.77 17.13 17.13 Viscosity (s) 16.10 16.61 16.65 17.01 17.01

[0115] Note: pH = 8.8, water temperature 20℃, water transit time is 15.1 sk = 0.993.

[0116] Table 7 Concentration 80kg / m³ 3 Effect of different stirring times on the viscosity of the hole protection slurry

[0117] Stirring time 7min 8min 9min 10min 11min Time (s) 16.89 17.08 17.25 17.37 17.38 Viscosity (s) 16.77 16.96 17.13 17.25 17.25

[0118] Note: pH = 8.8, water temperature 20℃, water transit time is 15.1 sk = 0.993.

[0119] Table 8 Concentration 85 kg / m³ 3 Effect of different stirring times on the viscosity of the hole protection slurry

[0120] Stirring time 8min 9min 10min 11min 12min Time (s) 16.94 17.14 17.42 17.51 17.50 Viscosity (s) 16.82 17.02 17.30 17.38 17.38

[0121] Note: pH = 8.8, water temperature 20℃, water transit time is 15.1 sk = 0.993.

[0122] Table 9 Concentration 90kg / m³ 3 Effect of different stirring times on the viscosity of the hole protection slurry

[0123] Stirring time 8min 9min 10min 11min 12min 13min Time (s) 16.90 17.14 17.41 17.52 17.66 17.66 Viscosity (s) 16.78 17.02 17.29 17.40 17.54 17.54

[0124] Note: pH = 8.8, water temperature 20℃, water transit time is 15.1 sk = 0.993.

[0125] Table 10 Concentration 100kg / m³ 3 Effect of different stirring times on the viscosity of the hole protection slurry

[0126] Stirring time 8min 9min 10min 11min 12min 13min Time (s) 17.40 18.05 18.49 18.89 19.25 19.25 Viscosity (s) 17.28 17.92 18.39 18.74 19.12 19.12

[0127] Note: pH = 8.8, water temperature 20℃, water transit time is 15.1 sk = 0.993.

[0128] Table 11 Concentration 110 kg / m³3 Effect of different stirring times on the viscosity of the hole protection slurry

[0129] Stirring time 9min 10min 11min 12min 13min 14min Time (s) 18.31 18.55 19.02 19.54 20.40 20.40 Viscosity (s) 18.18 18.42 18.89 19.40 20.26 20.26

[0130] Note: pH = 8.8, water temperature 20℃, water transit time is 15.1 sk = 0.993.

[0131] Table 12 Concentration 120kg / m³ 3 Effect of different stirring times on the viscosity of the hole protection slurry

[0132] Stirring time 10min 11min 12min 13min 14min 15min Time (s) 18.80 19.16 20.58 21.42 23.30 3.30 Viscosity (s) 18.67 19.03 20.44 21.27 23.14 23.14

[0133] Note: pH = 8.8, water temperature 20℃, water transit time is 15.1 sk = 0.993.

[0134] Table 13 Concentration 130 kg / m³ 3 Effect of different stirring times on the viscosity of the hole protection slurry

[0135] Stirring time 10min 11min 12min 13min 14min 15min Time (s) 20.72 22.13 23.26 24.43 25.52 25.52 Viscosity (s) 20.57 21.98 23.10 24.26 25.34 25.34

[0136] Note: pH = 8.8, water temperature 20℃, water transit time is 15.1 sk = 0.993.

[0137] Table 14 Concentration 140 kg / m³ 3 Effect of different stirring times on the viscosity of the hole protection slurry

[0138] Stirring time 11min 12min 13min 14min 15min 16min Time (s) 23.03 24.33 25.39 26.63 28.02 28.02 Viscosity (s) 22.87 24.16 25.21 26.44 27.82 27.82

[0139] Note: pH = 8.8, water temperature 20℃, water transit time is 15.1 sk = 0.993.

[0140] As shown in Tables 3-14, the viscosity of the borehole protection slurry is not only related to the slurry concentration, but also affected by the stirring time. Under the same conditions, the viscosity of the borehole protection slurry of the same concentration increases with the increase of stirring time. When the stirring time reaches a certain value, the slurry viscosity tends to stabilize.

[0141] The minimum stirring time for different concentrations of pore-protecting solutions is shown in Table 15.

[0142] Table 15 Minimum stirring time for borehole protection slurry at different concentrations

[0143]

[0144] (3) Performance test of the grout under reasonable stirring speed and minimum stirring time.

[0145] The general performance indicators of drilling mud are shown in Table 16. Based on the borehole collapse situation in the sintered rock area and referring to the properties of the "collapsed and spalled" strata, the required viscosity of the borehole protection mud is 23–25 s.

[0146] Table 16 General performance indicators of the borehole protection grout

[0147]

[0148]

[0149] Table 17 Properties of the grout at different concentrations and optimal stirring times.

[0150]

[0151] As shown in Table 17, to achieve the "collapse and rockfall" performance index, the mud (drilling slurry) concentration needs to reach 120-140 kg / m³. 3 The stirring time is 14-15 minutes.

[0152] The viscosity of the grout is closely related to the stirring speed, grout concentration, sand content, pH, and stirring time. The grout concentration affects the viscosity of the grout, thus directly affecting the grout protection effect. If the concentration is too low, the viscosity will be low and the grout protection effect will not be achieved. As the grout concentration increases, the speed required to reach a stable viscosity decreases. When the mixer speed reaches 1100 rpm, the grout viscosity no longer increases with the increase of the mixer speed. Too high a speed will increase the risk factor and reduce the service life of the mixer. Based on the site conditions, the speed is determined to be 900 rpm-1100 rpm.

[0153] Stirring time also affects viscosity. Too low a stirring time results in too low a viscosity, failing to achieve the desired borehole protection effect. Too high a stirring time reduces slurry preparation efficiency. Therefore, selecting an appropriate stirring time can improve both borehole protection effect and work efficiency. For the same concentration of borehole protection slurry, viscosity increases with increasing stirring time. When the stirring time reaches a certain value, the slurry viscosity tends to stabilize. Considering the properties of the borehole protection slurry in different formations, the required viscosity was determined to be 23-25 ​​s. Therefore, the final concentration of the borehole protection slurry was determined to be 120-140 kg / m³. 3 The corresponding minimum stirring time is 14-15 minutes.

[0154] Example 2

[0155] The test results in Example 1 are the parameters of the borehole protection slurry required when the borehole wall is undisturbed. In reality, borehole collapse mostly occurs during the drilling process. At the same time, a large amount of drill cuttings are mixed into the borehole protection slurry under the disturbance of the drilling rig, which reduces the viscosity and colloidal content of the slurry and increases the sand content, which is not conducive to the protection of the borehole by the slurry.

[0156] Therefore, based on the above experimental results, this invention further studies the hole protection effect of the hole protection slurry under the influence of drill cuttings.

[0157] I. Experimental Study on the Borehole Protection Effect of Bentonite Mixed with Drill Cuttings

[0158] During the borehole protection process, the borehole protection grout is injected into the borehole, and the drill cuttings will inevitably mix into the grout, affecting the borehole protection effect. Therefore, it is necessary to test the property changes of the borehole protection grout after the rock powder is added.

[0159] Table 18. Size Distribution of Drill Cuttings

[0160] Sieve aperture specifications 60 mesh 100 mesh 200 mesh % of sieve residue 65.06 8.26 9.32 Cumulative screening amount % 65.06 73.32 82.64

[0161] According to sand classification, particles smaller than 0.25 mm are classified as extra-fine sand, particles between 0.25 and 0.35 mm as fine sand, particles between 0.35 and 0.5 mm as medium sand, and particles larger than 0.5 mm as coarse sand. Studies suggest that extra-fine rock fragments smaller than 0.25 mm affect the colloidal content and viscosity of the borehole protection grout, while rock fragments larger than 0.25 mm act as aggregate for the grout, reinforcing the borehole wall. Therefore, this study primarily investigates the impact of rock fragments smaller than 0.25 mm on the properties of the borehole protection grout.

[0162] Referring to the fine rock powder produced by drilling in the field, the rock samples taken from the burned area were crushed, and rock powder with particle sizes of less than 200 mesh, 100-200 mesh, and 60-100 μm were taken respectively. They were then mixed with a certain amount of bentonite to prepare hole protection slurry, and experimental studies were conducted to test parameters such as colloidal content.

[0163] The experiment mainly tested the colloidal content of the borehole protection grout after incorporating rock cuttings. The experiment tested the concentration at 120 kg / m³. 3 The colloidal content of the slurry (60mg rock powder + 60mg bentonite) is shown in the experimental procedure below. Figure 2 .

[0164] The results are as follows Figure 2 As shown, the colloid content of the mixed mud prepared by mixing fine rock powder into bentonite will not meet the colloid content required for borehole protection.

[0165] II. Verification of the actual well protection effect of well protection slurry with different concentrations

[0166] 1. Hole protection principle

[0167] In practical applications, the borehole protection process of the borehole grout mainly manifests in two ways: First, the grout provides borehole protection upon contact with the borehole wall during injection. Second, during the thorough mixing process with the drill bit, the grout forms a high-concentration "mud" with the rock powder. This "mud" is then applied and reinforced to the borehole wall during the drill bit's impact motion, thus providing borehole protection. With further injection of the grout, the reinforced borehole wall is further protected. The borehole protection principle is as follows: Figure 3 As shown.

[0168] On-site verification experiments were conducted to confirm the laboratory study results of Example 1, at a concentration of 120 kg / m³. 3 With 140kg / m 3 The hole-protecting effect of the hole-protecting slurry is shown in the figure. Figure 4 .

[0169] The results are as follows Figure 4 As shown, when the grout concentration is 120 kg / m 3 At that time, the "mud" formed is in a loose state and cannot play a good role in protecting the hole. Figure 4 (Figure A) When the grout concentration is 140 kg / m 3 At that time, the existing "mud" forms a solid hole wall under the action of the drill bit and drill rod, which plays a very good role in protecting the hole. Figure 4 Figure B).

[0170] Therefore, the grout concentration is 140 kg / m. 3 It can play a good role in protecting the pores. The corresponding stirring time and other properties are shown in Table 19.

[0171] Table 19 Properties and parameters of the pore-protecting slurry with the best pore-protecting effect prepared in this invention

[0172]

[0173]

[0174] 2. Research on measures to improve the performance of hole-protecting grout

[0175] The stirring speed and the concentration of the borehole protection slurry have a significant impact on the borehole protection effect. Meanwhile, since the rock cuttings generated during drilling affect the viscosity of the borehole protection slurry, in order to further improve the borehole protection effect, this study proposes to add fibrous materials to the borehole protection slurry to increase the bonding strength between the slurry and the drill cuttings, thereby enhancing the borehole protection effect.

[0176] The experimental study used short glass fibers added to the grout for hole protection. The fiber diameter d = 0.85 mm to 2.85 mm and the length L = 20-30 mm. (See...) Figure 5 .

[0177] The laboratory used 5cm×5cm cross-section burnt rock blocks (rock samples from the burnt area of ​​Dananhu No. 2 Mine) as borehole walls. By adding different masses of glass fiber to a borehole protection slurry prepared from bentonite and rock cuttings, it was ultimately determined that adding 3g of glass fiber to 1L of slurry significantly improved the borehole protection effect. For experimental process comparisons, see [link to experimental procedure]. Figure 6 .

[0178] Figure 6 Figure A shows the effect of mud cake formed by 120g of drill cuttings (fine sand) + 120g of bentonite, and Figure B shows the effect of mud cake formed by 120g of drill cuttings (fine sand) + 120g of bentonite + 3g of glass fiber.

[0179] like Figure 6 As shown, the colloid content and viscosity of the borehole protection slurry made from a mixture of bentonite and rock fragments are significantly reduced, resulting in a thinner "mud skin" on the borehole wall. Without added glass fibers, the protective layer peels off and detaches as moisture is lost, initially failing to adhere to larger rocks, eventually forming fragmented dry mud skin. The protective slurry with added fibers forms an initial mud skin layer capable of adhering to larger rock fragments (maximum 4.6cm × 2.2cm × 2.1cm), and from its initial state to the formation of dry mud skin, the rock fragments do not slide or detach. The detached dry mud skin has densely and evenly distributed fibers, making it difficult to tear into fragments.

[0180] In summary, considering the impact of drill cuttings on the viscosity and colloidal content of the borehole protection slurry, adding short glass fibers (3 kg / m²) to the slurry is recommended. 3 This can further enhance the hole protection effect.

[0181] Therefore, it was ultimately determined that drilling wall bentonite B would be used as the raw material to prepare a solution with a concentration of 140 kg / m³. 3 To reduce the impact of drill cuttings on the viscosity, colloid content, and other properties of the borehole protection grout, glass fiber filaments (fiber diameter d = 0.85mm~2.85mm, length L = 20-30mm) are added to enhance the adhesion strength between the grout and the drill cuttings, thereby increasing the borehole protection effect. The amount of glass fiber filaments added is 3kg / m. 3 .

[0182] Adding 3g of glass fiber to 1L of pore-protecting solution significantly improves pore protection.

[0183] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention.

[0184] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing a grout for sealing boreholes in sintered rock in open-pit coal mines, characterized in that, Using bentonite for drilling wall protection as the raw material, it is mixed with water and stirred to prepare a slurry with a concentration of 120-140 kg / m³. The stirring speed is 900 rpm-1100 rpm, and the stirring time is 14-15 min. Then, fibrous material is added to the slurry at a rate of 1-3 kg / m³. 3 To obtain the hole-protecting slurry; The fibrous material is short glass fiber filaments.

2. The method for preparing the hole-protecting grout for burnt rock blast holes in open-pit coal mines according to claim 1, characterized in that, Using bentonite for drilling wall protection as the raw material, it is mixed with water and stirred to prepare a slurry with a concentration of 140 kg / m³.

3. The method for preparing the hole-protecting grout for burnt rock blast holes in open-pit coal mines according to claim 1, characterized in that, The stirring time is 15 minutes.

4. The method for preparing the hole-protecting grout for burnt rock blast holes in open-pit coal mines according to claim 1, characterized in that, The amount of fibrous material added is 3 kg / m³. 3 .

5. The method for preparing the hole-protecting grout for burnt rock blast holes in open-pit coal mines according to claim 4, characterized in that, The short glass fiber filaments have a diameter d = 0.85 mm to 2.85 mm and a length L = 20-30 mm.

6. A pore-protecting slurry prepared by the preparation method according to any one of claims 1-5.

7. The hole-protecting slurry according to claim 6, characterized in that, The grout has a viscosity of 27.82s, a relative density of 1.57, a pH of 9.0, a sand content of 0.50%, and a colloid content of 99%.

8. The application of the hole-protecting slurry according to claim 6 in hole protection of sintered rock blast holes in open-pit coal mines.

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