CN107843496A - A kind of assay method of tectonic soft coal solid coefficient - Google Patents

Abstract

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

Description

A method for measuring firmness coefficient of structural soft coal

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 structurally soft coal, which belongs to the field of mining engineering.

Background technique

In order to study the geological conditions of the coal seam so as to better serve the mining, it is necessary to measure the mechanical parameters of the coal body. At present, my country uses the firmness coefficient (also known as Platts coefficient) f of coal to evaluate the ability of coal to resist external damage. The f value is generally determined by the falling weight method. The drop hammer method believes that the work consumed by the crushing of coal 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. The crushing ratio can be used to express the firmness of the object; Determination method of property coefficient (GB/T23561.12-2010) "When testing the solidity coefficient of coal, various instruments and equipment such as crushing bucket, measuring cylinder, sample sieve, and small hammer are needed. By making the weight 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 metering height l of pulverized coal after impacting the sample; at the same time, Professor Protodyakonov, a former Soviet scholar, 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; Engineering guidance, and convenient and accurate, has been widely used in the field of geotechnical engineering.

In field practice, in the study of coal seam occurrence state and coal body properties, it is often necessary to take multiple samples in different mining areas of the same mining area to measure the firmness coefficient f of coal respectively:

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

However, when calculating the firmness coefficient of coal by measuring its uniaxial compressive strength, due to the strain generated by the coal seam under the action of structural stress and formation pressure, the coal body structure will be damaged to varying degrees, and the strength of the coal is low. Soft coal is a kind of loose and broken coal body whose coal body structure suffers from high degree of tectonic stress damage. Its strength is extremely low, and the finished product has obtained the standard sample size (Φ×H=50mm×100mm) stipulated by the International Society of Rock Mechanics. Therefore, it is difficult to directly establish the relationship between the uniaxial compressive strength of structural soft coal and the firmness coefficient of soft coal.

Contents of the invention

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

In order to achieve the above object, the technical solution 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 coal sample of structural soft coal in a coal seam, and record the buried depth H of the coal extraction site simultaneously;

(2) Coal sample firmness factor f ₁ is measured: the coal sample that step (1) is obtained, according to national standard "coal's firmness factor test method (GB/T23561.12-2010) " measure its firmness factor f ₁ ;

(3) Production of structural soft coal briquettes:

a. Use the forming pressure formula to calculate the forming pressure of the corresponding standard cylindrical size sample. The size of the standard cylindrical sample is D×h=50mm×100mm. The forming pressure formula is: P=πr ² ·γH, where D is the diameter of the standard cylindrical size , 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 strata above the coal seam, and H is the buried depth of the coal sample;

B, with the forming pressure P calculated by the above steps, the broken coal sample obtained in step (1) is compressed into a briquette with a standard cylindrical test piece size, and the holding time is t;

c. Dry the briquettes;

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

(5) Comparing the solidity coefficient f ₁ of the coal sample and the solidity coefficient f ₂ of the molded coal, determine the holding time t ₀ :

If f ₁ =f ₂ , it proves that the pressure-holding time t of the above-mentioned step (3) is suitable for making molded coal, the parameters are accurate, and the solidity of molded coal can reflect the firmness of structural soft coal;

If f ₁ >f ₂ , repeat step (3) and increase the holding time t, then repeat steps (4) to (5) until the calculation result is f ₁ =f ₂ , the firmness of the briquette test piece reflects the softness of the structure. Coal firmness, now the pressure holding time t after adjustment in the above-mentioned steps (3) is t ₀ ;

If f ₁ < f ₂ , repeat step (3) and reduce the holding time t, then repeat step (4) to step (5) until the calculation result f ₁ = f ₂ , the firmness of the briquette test piece reflects the softness of the structure Coal firmness, now the pressure holding time t adjusted in the above-mentioned steps (3) is t ₀ ;

(6) Determination of the firmness coefficients of other deeply buried coal bodies in the same mining area: when measuring the firmness coefficients of other buried deep coal bodies in the same mining area, repeat steps (1), (3) and (4) in sequence, wherein 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 coal body at this depth.

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

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

Preferably, the temperature used for the low-temperature drying is 25°C-50°C, and the time is 12h-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 coefficients of multiple test pieces, the present invention only needs to use the drop weight method once, and the steps and processes are simpler and more convenient; at the same time, compared with the direct measurement of the uniaxial compressive strength of standard test pieces, the firmness coefficient is calculated In terms of the method, it avoids the process of making standard test pieces with complete coal samples, reduces the difficulty of testing, and facilitates the promotion of engineering analogy; because the molded coal made of structural soft coal has strong plasticity, small fluctuation, simple process, The advantages of easy measurement of mechanical properties 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 measuring the firmness coefficient of structural soft coal in the present invention.

Detailed ways

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

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

(1) Selection of structural soft coal: select a coal sample of structural soft coal in a coal seam, and record the buried depth H of the coal extraction site simultaneously;

(2) Determination of coal sample firmness coefficient f1 _: measure the solidity of the coal sample obtained in step (1) according to the national standard "Measurement Method for Coal Firmness Coefficient (GB/T23561.12-2010)" coefficient f ₁ ;

(3) Production of structural soft coal briquettes:

a. Use the forming pressure formula to calculate the forming pressure of the corresponding standard cylindrical size sample. The size of the standard cylindrical sample is D×h=50mm×100mm. The forming pressure formula is: P=πr ² ·γH, where D is the diameter of the standard cylindrical size , 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 strata on the coal seam, and H is the buried depth of the coal sample;

B, with the forming pressure P calculated by the above steps, the broken coal sample obtained in step (1) is compressed into a briquette with a standard cylindrical test piece size, and the holding time is t;

c. Dry the briquettes;

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

(5) Comparing the solidity coefficient f ₁ of the coal sample and the solidity coefficient f ₂ of the molded coal, determine the holding time t ₀ :

If f ₁ = f ₂ , it proves that the pressure-holding time t ₀ of the above-mentioned step (3) is appropriate, the parameters are accurate, and the solidity of the coal-shaped coal can reflect the solidity of the structural soft coal. At this time, the pressure-holding time in the above-mentioned step (3) t is t ₀ ;

If f ₁ >f ₂ , repeat step (3) and increase the holding time t, then repeat steps (4) to (5) until the calculation result is f ₁ =f ₂ , the firmness of the briquette test piece reflects the softness of the structure. Coal firmness, now the holding time t in the above-mentioned steps (3) is t ₀ ;

If f ₁ < f ₂ , repeat step (3) and reduce the holding time t, then repeat step (4) to step (5) until the calculation result f ₁ = f ₂ , the firmness of the briquette test piece reflects the softness of the structure Coal firmness, now the holding time t in the above-mentioned steps (3) is t ₀ ;

(6) Determination of the firmness coefficients of other deeply buried coal bodies in the same mining area: when measuring the firmness coefficients of other buried deep coal bodies in the same mining area, repeat steps (1), (3) and (4) in sequence, wherein in step (3) The pressure-holding time t is the pressure-holding time t ₀ determined in step ( ₅ ), and the firmness coefficient f2 of the finally obtained briquette is the firmness coefficient of the buried coal body at this depth.

It is found in practice that the holding time t in step (3) is relatively short, and the pressed briquettes are too soft and brittle to meet the experimental requirements. However, when the holding time t exceeds 30 minutes, the pressed briquettes will lose their strength. There is no obvious increase, and the holding time t is within the range of 15min to 30min, and the final measured firmness coefficient results can meet the requirements, so the selection and adjustment range of the holding time t is 15min to 30min, which is more appropriate.

When drying the molded coal, because the high temperature will cause the moisture in the molded coal to evaporate quickly, and the inside of the molded coal is susceptible to thermal expansion, which will eventually cause the structure of the molded coal to change and deviate from the real situation, so preferably, step (3) In the process, the briquettes are dried by low-temperature drying.

When drying briquettes, the drying time is longer when the temperature is low, and the briquettes are easily damaged if the temperature is high; the drying time is short, which will lead to incomplete drying, and if the drying time is too long, it will easily make the briquettes too dry. , the drying temperature used is between 25°C and 50°C, and the drying time is between 12h and 36h, and the effect of the briquette produced is better.

After the coal seam is exposed, it will produce a slow oxidation reaction in contact with the air, and its chemical structure will change. At the same time, its internal physical structure will continue to change after contact with the air and moisture in the air; 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, because the newly exposed coal seam and the air The contact time is shorter and the change is smaller, so it is closer to the state when the coal seam is not exposed.

The present invention only needs to use the drop weight method once when measuring multiple test pieces, avoiding a lot of repetitive labor, and the steps and processes are simpler and more convenient; and if the uniaxial compressive strength of the standard test piece is directly used to measure To measure 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. However, it is difficult to take out a complete coal sample with soft structural media. Therefore, this method is used to measure the firmness coefficient of structural soft coal. , which avoids the process of making standard test pieces with complete coal samples, reduces the difficulty of testing, and facilitates the promotion of engineering analogy; because the briquettes made of structural soft coal have strong plasticity, small volatility, simple process, and easy measurement of mechanical properties etc., can indirectly reflect the firmness of structural soft coal, so the coal firmness coefficient measured according to the present invention is closer to the real value.

Below is the embodiment according to above-mentioned embodiment:

Example 1:

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

( ₂ ) Determination of coal sample solidity coefficient f1: select the coal sample with relatively complete lumpiness obtained in step (1), and measure its firmness according to the national standard "Measurement Method for Coal Firmness Coefficient (GB/T23561.12-2010)" Sex coefficient f ₁ =0.4;

(3) Production of structural soft coal briquettes:

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 compressed into a briquette with a standard cylindrical test piece size (D * h = 50mm * 100mm), the pressure used is 39.25kN, and the holding time is 20min;

c. Dry the briquettes for 36 hours at a temperature of 25°C;

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

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

(6) Measure the solidity coefficient of the coal body at different buried depths in this mining area: sample the coal seam with a buried depth of 600m, repeat step (3), wherein the pressure of pressing the briquettes is 29.4kN, and the holding time is still 20min , other parameters are kept constant, after pressing the formed coal, repeat the step (4), the final measured result is 600m coal seam firmness coefficient f'=0.32.

For verification by the accuracy of the assay method of a kind of structure soft coal firmness coefficient that the present invention proposes, to the coal seam sample of this mine burial depth 600m in the step (6), by according to national standard " firmness coefficient assay method of coal (GB/T23561.12-2010)>The coal seam firmness coefficient f ₁ '=0.30≈f' was measured again, and the result proves that the result measured by the present invention is close to the real value.

Example 2:

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

( ₂ ) Determination of coal sample solidity coefficient f1: select the coal sample with relatively complete lumpiness obtained in step (1), and measure its firmness according to the national standard "Measurement Method for Coal Firmness Coefficient (GB/T23561.12-2010)" Sex coefficient f ₁ =0.2;

(3) Production of structural soft coal briquettes:

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

B, the broken coal sample that obtains in step (1) is compressed into the briquette that has standard cylinder test piece size (D * h=50mm * 100mm), the pressure that adopts is 29.4kN, and the holding time is 20min;

c. Dry the briquettes for 12 hours at a temperature of 50°C;

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

(5) Compare the solidity coefficient f ₁ of the coal sample and the solidity coefficient f ₂ of the molded coal, and find that f ₁ >f ₂ , then repeat steps (4) to (5), in which the holding time is increased to 25 minutes, and the result is measured Obtain f ₂ =0.2=f ₁ , so it is determined that the pressure holding time for making briquettes in this coal mine is 25 minutes;

(6) measure the solidity coefficient of the coal body of different burial depths in this mining area: the coal seam that burial depth is 1000m is sampled, repeats step (3), wherein the pressure of pressing briquette is 49kN, and the holding time is still 25min, Other parameters are all the same, after pressing the formed coal, repeat step (4), the final measured result is that the coal seam firmness coefficient f'=0.5 at the depth of 1000m, that is, the firmness coefficient of the coal seam at the depth of 1000m is 0.5.

For verifying once again the accuracy of the assay method of a kind of structural soft coal firmness coefficient that the present invention proposes, to the coal seam sample of this mine burial depth 1000m in step (6), by according to national standard " firmness coefficient of coal is measured Method (GB/T23561.12-2010)> measured 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 solidity coefficient of coal seams with different buried depths in other coal mines, the measurement can be carried out according to the above steps. This method is simple, convenient, easy to implement, easy to promote, and the measurement results conform to the actual situation.

Claims (5)

1. A kind of 1. assay method of tectonic soft coal solid coefficient, it is characterised in that：Comprise the following steps：

   (1) selection of tectonic soft coal：In coal seam one at choose tectonic soft coal coal sample, while record the buried depth for taking coal place H；

   (2) coal sample solid coefficient f₁Measure：The coal sample that step (1) is obtained, according to national standard《The solid coefficient measure side of coal Method (GB/T23561.12-2010)》Determine its solid coefficient f₁；

   (3) making of tectonic soft coal moulded coal：

   A, the briquetting pressure of corresponding standard cylinder sample, standard cylinder specimen size D × h=are calculated using briquetting pressure formula 50mm × 100mm, briquetting pressure formula are：P=π r²γ H, wherein D are standard round column dimension diameter, and h is standard cylinder chi Very little height, r are standard round column dimension radius, and γ is Strata Overlying The Seam unit weight, and H is the coal sample buried depth；

   B, the briquetting pressure P calculated with above-mentioned steps, the broken coal sample obtained in step (1) is pressed into standard The moulded coal of cylindrical specimen size, dwell time t；

   C, moulded coal is dried；

   (4) moulded coal solid coefficient f₂Measure：Test the uniaxial compressive strength P according to the moulded coal test specimen made in step (3)₀, and The solid coefficient f of moulded coal is calculated according to the relation between uniaxial compressive strength and solid coefficient₂；

   (5) coal sample solid coefficient f is contrasted₁And moulded coal solid coefficient f₂, determine dwell time t₀：

   If f₁=f₂, it was demonstrated that above-mentioned steps (3) moulded coal making dwell time t is suitable, and parameter is accurate, and moulded coal robustness can reflect Tectonic soft coal robustness, now the dwell time t in above-mentioned steps (3) is t₀；

   If f₁>f₂, then repeat step (3) and dwell time t is increased, then repeat step (4) to step (5), until results of measuring f₁=f₂, moulded coal test specimen robustness reflection tectonic soft coal robustness, the dwell time t after now adjusting in above-mentioned steps (3) is t₀；

   If f₁<f₂, then repeat step (3) and dwell time t is reduced, then repeat step (4) to step (5), until results of measuring f₁=f₂, moulded coal test specimen robustness reflection tectonic soft coal robustness, the dwell time t after now adjusting in above-mentioned steps (3) is t₀；

   (6) determination of other buried depth coal body solid coefficients of same mining area：Measure the other buried depth coal body robustness systems in same mining area During number, step (1), (3) and (4) is repeated in, when the wherein dwell time t in step (3) is the pressurize determined in step (5) Between t₀, finally give the solid coefficient f of moulded coal₂The as solid coefficient of the buried depth coal body.
2. A kind of 2. assay method of tectonic soft coal solid coefficient according to claim 1, it is characterised in that：The step (3) selection of the dwell time t in and adjusting range are 15min~30min.
3. A kind of 3. assay method of tectonic soft coal solid coefficient according to claim 1, it is characterised in that：The step (3) in, the mode to moulded coal drying is low temperature drying.
4. A kind of 4. assay method of tectonic soft coal solid coefficient according to claim 3, it is characterised in that：The low temperature The temperature used is dried as 25 DEG C~50 DEG C, the time is 12h~36h.
5. 5. a kind of assay method of tectonic soft coal solid coefficient according to Claims 1-4 any one claim, It is characterized in that：Coal seam in the step (1) is newly exposed coal seam.