CN107843496B - Method for measuring firmness coefficient of structural soft coal - Google Patents

Abstract

The invention discloses a method for determining the firmness coefficient of structural soft coal. First, structural soft coal is selected, its burial depth is recorded, and its burial depth is recorded, and its The firmness coefficient f ₁ , according to the different pressures of the buried depth of the coal seam, the structural soft coal is pressed into briquette, the pressure holding time is t, and then the uniaxial compressive strength of the briquette is measured, and the firmness coefficient f ₂ of the briquette is calculated based on this , if f ₁ =f ₂ , then the pressure holding time is t ₀ , if f ₁ ≠f ₂ , increase or decrease the pressure holding time t, repeat the above steps until f ₁ =f ₂ , then the pressure holding time is The time is t ₀ . Finally, when the firmness coefficient of the coal body at other buried depths in the same mining area is measured, the structural soft coal is pressed into briquette, and the pressure is calculated according to its burial depth. The pressure holding time is t ₀ . According to the relationship between the firmness coefficient and the uniaxial compressive strength, the firmness coefficient of the soft coal of this structure is calculated. The method is simple and convenient, and the measurement results conform to the actual situation.

Description

A kind of determination method of structural soft coal firmness coefficient

technical field

The invention relates to a method for measuring the firmness coefficient of coal, in particular to a method for measuring the firmness coefficient of structural soft coal, which belongs to the field of mining engineering.

Background technique

In order to study the geological conditions of coal seams in order to better serve the mining operation, it is necessary to measure the mechanical parameters of the coal body. At present, coal's firmness coefficient (also known as Platts coefficient) f is used to evaluate the ability of coal to resist external damage. The f value is generally determined by the drop weight method. The falling hammer method believes that the work consumed by coal crushing is proportional to the increased surface area of the crushed material, and the constant related to the strength or firmness of the object is related to the crushing ratio, and the crushing ratio can be used to represent the firmness of the object; When testing the firmness coefficient of coal, a variety of instruments and equipment such as smashing barrels, measuring cylinders, sample sieves, small hammers, etc. are required. By making the heavy hammer free at a certain height Drop and impact the sample, and then calculate the f value with the formula f=20n/l according to the number of impacts n and the measurement height l of the pulverized coal after impacting the sample; at the same time, the former Soviet scholar Prof. The point of view put forward in practice is that the value of the firmness coefficient f of coal or rock is 1/10 of the uniaxial compressive strength (unit: MPa) of rock or soil; It has engineering guiding significance, is convenient and accurate, and has been widely used in the field of geotechnical engineering.

In field practice, in the study of coal seam occurrence state and coal mass properties, it is often necessary to sample multiple times in different mining areas of the same mining area to determine the coal firmness coefficient f:

If the drop weight method is used, it is difficult to meet the convenience requirements due to the large number of samples, the large amount of repetitive labor, the many test steps, the long test time, and the cumbersome process;

However, when the firmness coefficient of coal is calculated by measuring its uniaxial compressive strength, the coal structure is damaged to varying degrees due to the strain generated by the coal seam under the action of tectonic stress and formation pressure, and the strength of coal is low. Soft coal is a kind of loose and fragmented coal body with a high degree of tectonic stress damage to the coal body structure, and its strength is extremely low. It is difficult to test its uniaxial compressive strength, so it is impossible to directly establish the relationship between the uniaxial compressive strength of structural soft coal and the firmness coefficient of soft coal.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method for determining the firmness coefficient of structural soft coal, which can calculate the firmness coefficient of structural soft coal by measuring the uniaxial compressive strength of briquette, which can simplify the measurement steps and facilitate engineering analogy promotion.

In order to achieve the above-mentioned purpose, the technical scheme adopted in the present invention is: a method for measuring the firmness coefficient of structural soft coal, comprising the following steps:

(1) Selection of structural soft coal: select a structural soft coal sample at one point in the coal seam, and record the burial depth H of the coal taking place;

(2) Determination of coal sample firmness coefficient f ₁ : the coal sample obtained in step (1) is measured for its firmness coefficient f ₁ according to the national standard "Method for Determination of Coal Firmness Coefficient (GB/T23561.12-2010)";

(3) Production of structural soft coal briquette:

a. Use the forming pressure formula to calculate the forming pressure of the corresponding standard cylinder size sample, the standard cylinder sample size D×h=50mm×100mm, the forming pressure formula is: P=πr ² ·γH, where D is the standard cylinder size diameter , h is the height of the standard cylinder size, r is the radius of the standard cylinder size, γ is the bulk density of the overlying rock layer of the coal seam, and H is the burial depth of the coal sample;

b. Press the crushed coal sample obtained in step (1) into a briquette with the size of a standard cylindrical specimen with the forming pressure P calculated in the above steps, and the pressure holding time is t;

c. Dry the briquette;

( ₄ ) Determination of briquette firmness coefficient f2: The test is based on the uniaxial compressive strength P ₀ of the briquette specimen produced in step (3), and is calculated according to the relationship between the uniaxial compressive strength and firmness coefficient The firmness coefficient f2 of the briquette;

(5) Compare the coal sample firmness coefficient f ₁ and the briquette firmness coefficient f ₂ to determine the pressure holding time t ₀ :

If f ₁ =f ₂ , it proves that the pressure holding time t of the briquette production in the above step (3) is appropriate, the parameters are accurate, and the firmness of the briquette can reflect the firmness of the structural soft coal;

If f ₁ >f ₂ , repeat step (3) and increase the dwell time t, and then repeat steps (4) to (5) until the measurement result f ₁ =f ₂ , the firmness of the briquette specimen reflects the structural softness Coal firmness, at this time, the pressure-holding time t adjusted in the above step (3) is t ₀ ;

If f ₁ <f ₂ , repeat step (3) and reduce the dwell time t, and then repeat steps (4) to (5) until the calculation result f ₁ =f ₂ , the firmness of the briquette specimen reflects the structural softness Coal firmness, at this time, the pressure holding time t adjusted in the above step (3) is t ₀ ;

(6) Determination of the firmness coefficient of other deeply buried coal bodies in the same mining area: when measuring the firmness coefficients of other deeply buried coal bodies in the same mining area, repeat steps (1), (3) and (4) in turn, where in step (3) The pressure holding time t is the pressure holding time t ₀ determined in step (5), and the firmness coefficient f ₂ of the finally obtained briquette is the firmness coefficient of the buried deep coal body.

Preferably, the selection and adjustment range of the holding pressure time t in the step (3) is 15 min to 30 min.

In order to prevent the structure of the briquette from changing, preferably, in the step (3), the drying method for the briquette is low-temperature drying.

Preferably, the temperature used in the low-temperature drying is 25°C to 50°C, and the time is 12h to 36h.

In order to make the obtained mechanical test value of the structural soft coal sample closer to the actual situation, preferably, the coal seam in the step (1) is a newly exposed coal seam.

When measuring the firmness coefficient of a plurality of test pieces, the present invention only needs to use the drop weight method once, and the steps and processes are simpler and more convenient; meanwhile, the firmness coefficient is measured relative to the direct measurement of the uniaxial compressive strength of the standard test piece. In terms of the method, it avoids the process of making standard specimens with complete coal samples, reduces the difficulty of testing, and facilitates the promotion of engineering analogies; because the briquette made from structural soft coal has strong moldability, low volatility, simple process, The advantages of easy measurement of mechanical properties, etc., can indirectly reflect the firmness of structural soft coal, so the firmness coefficient of coal body measured according to the present invention is closer to the real value.

Description of drawings

FIG. 1 is a flow chart of a method for determining the firmness coefficient of structural soft coal according to the present invention.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings.

As shown in Figure 1, a method for determining the firmness coefficient of structural soft coal includes the following steps:

(1) Selection of structural soft coal: select a structural soft coal sample at one point in the coal seam, and record the burial depth H of the coal taking place;

(2) Determination of coal sample firmness coefficient f ₁ : The firmness of the coal sample with complete blockness obtained in step (1) is measured according to the national standard "Method for Determination of Coal Firmness Coefficient (GB/T23561.12-2010)" coefficient f ₁ ;

(3) Production of structural soft coal briquette:

a. Use the forming pressure formula to calculate the forming pressure of the corresponding standard cylinder size sample, the standard cylinder sample size D×h=50mm×100mm, the forming pressure formula is: P=πr ² ·γH, where D is the standard cylinder size diameter , h is the height of the standard cylinder size, r is the radius of the standard cylinder size, γ is the bulk density of the overlying rock layer of the coal seam, and H is the burial depth of the coal sample;

b. Press the crushed coal sample obtained in step (1) into a briquette with the size of a standard cylindrical specimen with the forming pressure P calculated in the above steps, and the pressure holding time is t;

c. Dry the briquette;

( ₄ ) Determination of briquette firmness coefficient f2: The test is based on the uniaxial compressive strength P ₀ of the briquette specimen produced in step (3), and is calculated according to the relationship between the uniaxial compressive strength and firmness coefficient The firmness coefficient f ₂ of the briquette;

(5) Compare the coal sample firmness coefficient f ₁ and the briquette firmness coefficient f ₂ to determine the pressure holding time t ₀ :

If f ₁ =f ₂ , it proves that the pressure holding time t ₀ in the above step (3) is suitable for making briquette, the parameters are accurate, and the firmness of the briquette can reflect the firmness of the structural soft coal. At this time, the pressure holding time in the above step (3) t is t ₀ ;

If f ₁ >f ₂ , repeat step (3) and increase the dwell time t, and then repeat steps (4) to (5) until the measurement result f ₁ =f ₂ , the firmness of the briquette specimen reflects the structural softness Coal firmness, at this time, the pressure holding time t in the above step (3) is t ₀ ;

If f ₁ <f ₂ , repeat step (3) and reduce the dwell time t, and then repeat steps (4) to (5) until the calculation result f ₁ =f ₂ , the firmness of the briquette specimen reflects the structural softness Coal firmness, at this time, the pressure holding time t in the above step (3) is t ₀ ;

(6) Determination of the firmness coefficient of other deeply buried coal bodies in the same mining area: when measuring the firmness coefficients of other deeply buried coal bodies in the same mining area, repeat steps (1), (3) and (4) in turn, where in step (3) The pressure holding time t is the pressure holding time t ₀ determined in step (5), and the firmness coefficient f ₂ of the finally obtained briquette is the firmness coefficient of the buried deep coal body.

In practice, it is found that the pressure holding time t in step (3) is short, the pressed briquette is too soft and brittle, and cannot meet the experimental requirements, and after the pressure holding time t exceeds 30min, the pressed briquette strength There is no significant increase, and the holding pressure time t is in the range of 15min to 30min, and the final measured firmness coefficient result can meet the requirements. Therefore, the selection and adjustment range of the holding pressure time t is 15min to 30min, which is more appropriate.

When drying the briquette, the high temperature will cause the moisture in the briquette to evaporate rapidly, and the interior of the briquette is susceptible to thermal expansion, which eventually leads to a change in the structure of the briquette, which deviates from the real situation. Therefore, preferably, step (3) In the process, the briquette is dried by low-temperature drying.

When drying briquette, the drying time is longer at lower temperature, and the briquette is easily damaged at high temperature; short drying time will lead to incomplete drying, and too long time will easily make the briquette too dry. According to the experiment , the drying temperature used is between 25 ℃ and 50 ℃, and the time is between 12h and 36h, and the briquette effect is better.

After the coal seam is exposed, it will produce a slow oxidation reaction when it comes into contact with the air, and its chemical structure will change. The mechanical test value of the soft coal sample is closer to the actual situation, so when selecting the coal sample, it should be selected from the newly exposed coal seam, that is, the coal seam in step (1) is the newly exposed coal seam. The contact time is shorter and the change is smaller, so it is closer to the state when the coal seam is not exposed.

When measuring multiple test pieces, the present invention only needs to use the drop weight method once, which avoids a lot of repetitive labor, and the steps and processes are simpler and more convenient. To calculate the firmness coefficient, it is necessary to collect a complete coal sample on site, and then process it into a standard test piece by grinding or cutting methods. However, it is difficult to take out a complete coal sample with a structural soft medium. Therefore, this method is used to measure the firmness coefficient of structural soft coal. , which avoids the process of making standard specimens from complete coal samples, reduces the difficulty of testing, and facilitates the promotion of engineering analogies; because the briquette made from structural soft coal has strong moldability, small fluctuation, simple process, and easy determination of mechanical properties It can indirectly reflect the firmness of structural soft coal, so the firmness coefficient of coal body measured according to the present invention is closer to the real value.

The following are examples according to the above-described embodiments:

Example 1:

(1) Selection of structural soft coal: Take Coal Mine A as the research object, the coal seam of this mine is structural soft coal, and in the mining area with a burial depth of 800m, select the structural soft coal sample in the newly exposed coal seam; record the burial depth H=800m;

(2) Determination of coal sample firmness coefficient f ₁ : Select the coal sample with relatively complete lumps obtained in step (1), and measure its firmness according to the national standard "Method for Determination of Coal Firmness Coefficient (GB/T23561.12-2010)" Sex coefficient f ₁ =0.4;

(3) Production of structural soft coal briquette:

a. Use the forming pressure formula to calculate the forming pressure of the corresponding standard cylindrical size sample. The forming pressure formula is: P=πr ² ·γH, where the measured value of γ is 25kN/m ³ , then P=39.25kN;

b. The crushed coal sample obtained in step (1) is pressed into briquette with standard cylindrical specimen size (D×h=50mm×100mm), the pressure used is 39.25kN, and the pressure holding time is 20min;

c. Dry the briquette for 36h at a temperature of 25°C;

(4) Determination of briquette firmness coefficient f2: _The measured uniaxial compressive strength of briquette is 4MPa. According to the formula f=R/ ₁₀ , where R is the uniaxial compressive strength, the firmness coefficient f2 of briquette is calculated. = 0.4;

(5) Comparing the coal sample firmness coefficient f ₁ and the briquette firmness coefficient f ₂ , it is found that f ₁ =f ₂ , and thus the pressure holding time t ₀ =20min can be determined;

(6) Measure the firmness coefficient of coal at different burial depths in the mining area: sample the coal seam with a burial depth of 600m, repeat step (3), wherein the pressure of the pressed briquette is 29.4kN, and the pressure holding time is still 20min , and other parameters remain unchanged. After pressing the briquette, repeat step (4), and the final result is that the burial depth of the coal seam is 600m, and the firmness coefficient f'=0.32.

In order to verify the accuracy of the method for determining the firmness coefficient of structural soft coal proposed by the present invention, the coal seam sample with a buried depth of 600m in the mine in step (6) was tested in accordance with the national standard "Method for Determination of Firmness Coefficient of Coal". (GB/T23561.12-2010)" again to measure its coal seam firmness coefficient f ₁ '=0.30≈f', and the result proves that the measured result of the present invention is close to the real value.

Example 2:

(1) Selection of structural soft coal: Take B Coal Mine as the research object, the coal seam of this mine is structural soft coal, and in the mining area with a burial depth of 600m, select structural soft coal samples in the newly exposed coal seam; record the burial depth H=600m;

(2) Determination of coal sample firmness coefficient f ₁ : Select the coal sample with relatively complete lumps obtained in step (1), and measure its firmness according to the national standard "Method for Determination of Coal Firmness Coefficient (GB/T23561.12-2010)" Sex coefficient f ₁ =0.2;

(3) Production of structural soft coal briquette:

a. Use the forming pressure formula to calculate the forming pressure of the corresponding standard cylindrical size sample. The forming pressure formula is: P=πr ² ·γH, where the measured value of γ is 25kN/m ³ , then P=29.4kN;

b. Press the broken coal sample obtained in step (1) into briquette with standard cylindrical specimen size (D×h=50mm×100mm), the pressure used is 29.4kN, and the pressure holding time is 20min;

c. Dry the briquette for 12h at a temperature of 50°C;

(4) Determination of briquette firmness coefficient f2: _The measured uniaxial compressive strength of briquette is 1.5MPa. According to the formula f=R/10, where R is the uniaxial compressive strength, the firmness coefficient f of briquette is calculated. ₂ = 0.15;

(5) Compare the coal sample firmness coefficient f ₁ and the briquette firmness coefficient f ₂ , and find that f ₁ >f ₂ , then repeat steps (4) to (5), wherein the pressure holding time is increased to 25min, and the result is measured Obtained f ₂ =0.2=f ₁ , thus confirming that the pressure holding time for making briquette in this coal mine is 25min;

(6) Measure the firmness coefficient of coal bodies with different burial depths in this mining area: sample the coal seam with a burial depth of 1000m, repeat step (3), wherein the pressure of pressing the briquette is 49kN, and the pressure holding time is still 25min, All other parameters remain unchanged. After pressing the briquette coal, repeat step (4), and the final result is that the coal seam solidity coefficient f'=0.5 with a buried depth of 1000m is 0.5.

In order to verify the accuracy of the method for determining the firmness coefficient of structural soft coal proposed by the present invention, the coal seam sample with a burial depth of 1000m in the step (6) was tested according to the national standard "Determination of firmness coefficient of coal". Method (GB/T23561.12-2010)" to measure the coal seam firmness coefficient f ₁ '=0.53≈f' again, and the result proves that the result measured by the present invention is close to the real value.

When measuring the coal body firmness coefficient of different buried depths of other coal mines, the measurement can be performed according to the above steps. The method is simple, convenient, easy to implement, easy to popularize, and the measurement results conform to the actual situation.

Claims (5)

1. a method for measuring the firmness coefficient of structural soft coal, is characterized in that: comprise the following steps: (1) Selection of structural soft coal: select a structural soft coal sample at one point in the coal seam, and record the burial depth H of the coal taking place; (2) Determination of firmness coefficient f1 _of coal sample: measure the firmness coefficient f1 of the coal sample obtained in step ( ₁ ) according to the national standard "Method for Determination of Firmness Coefficient of Coal (GB/T23561.12-2010)"; (3) Production of structural soft coal briquette: a. Use the forming pressure formula to calculate the forming pressure of the corresponding standard cylindrical sample. The size of the standard cylindrical sample is D×h=50mm×100mm, and the forming pressure formula is: P=πr ² ·γH, where D is the standard cylindrical size and diameter, h is the height of the standard cylinder size, r is the radius of the standard cylinder size, γ is the bulk density of the overlying rock layer of the coal seam, and H is the burial depth of the coal sample; b. Press the crushed coal sample obtained in step (1) into a briquette with the size of a standard cylindrical specimen with the forming pressure P calculated in the above steps, and the pressure holding time is t; c. Dry the briquette; ( ₄ ) Determination of briquette firmness coefficient f2: The test is based on the uniaxial compressive strength P ₀ of the briquette specimen produced in step (3), and is calculated according to the relationship between the uniaxial compressive strength and firmness coefficient The firmness coefficient f ₂ of the briquette; (5) Compare the coal sample firmness coefficient f ₁ and the briquette firmness coefficient f ₂ to determine the pressure holding time t ₀ : If f ₁ =f ₂ , it proves that the pressure holding time t in the above step (3) is suitable for making briquette, the parameters are accurate, and the firmness of the briquette can reflect the firmness of the structural soft coal. At this time, the pressure holding time t in the above step (3) is t ₀ ; If f ₁ >f ₂ , repeat step (3) and increase the dwell time t, and then repeat steps (4) to (5) until the measurement result f ₁ =f ₂ , the firmness of the briquette specimen reflects the structural softness Coal firmness, at this time, the pressure holding time t adjusted in the above step (3) is t ₀ ; If f ₁ <f ₂ , repeat step (3) and reduce the dwell time t, and then repeat steps (4) to (5) until the calculation result f ₁ =f ₂ , the firmness of the briquette specimen reflects the structural softness Coal firmness, at this time, the pressure holding time t adjusted in the above step (3) is t ₀ ; (6) Determination of the firmness coefficient of other deeply buried coal bodies in the same mining area: when measuring the firmness coefficients of other deeply buried coal bodies in the same mining area, repeat steps (1), (3) and (4) in turn, where in step (3) The pressure holding time t is the pressure holding time t ₀ determined in step (5), and the firmness coefficient f ₂ of the finally obtained briquette is the firmness coefficient of the buried deep coal body. 2 . The method for determining the firmness coefficient of structural soft coal according to claim 1 , wherein the selection and adjustment range of the holding pressure time t in the step (3) is 15 min to 30 min. 3 . 3 . The method for measuring the firmness coefficient of structural soft coal according to claim 1 , wherein: in the step (3), the method of drying the briquette is low-temperature drying. 4 . 4 . The method for measuring the firmness coefficient of structural soft coal according to claim 3 , wherein the temperature used in the low-temperature drying is 25° C. to 50° C. and the time is 12 h to 36 h. 5 . 5 . The method for determining the firmness coefficient of structural soft coal according to any one of claims 1 to 4 , wherein the coal seam in the step (1) is a newly exposed coal seam. 6 .

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