Classification of rocks by Prof. M

The strength of a rock is its resistance to general destruction. Strength coefficient f is a dimensionless quantity that shows how many times one rock is stronger than another, taken as a standard. For the standard prof. MM. Protodyakonov accepted dense dry clay with a uniaxial compressive strength R compress = 100 kgf/cm 2(those. f rock having Rcom =100 kg/cm 2 equals 1). Therefore, the strength coefficient f according to the Protodyakonov scale M.M. will be:

f = R compress /100,

Where R compress– temporary resistance of the sample of the studied rock to compression, kg/cm 2 ;

100 – temporary resistance of the rock, taken as the standard, to compression.

If the compressive strength of the reference rock is expressed in MPa, then the compression resistance of the reference rock will be equal to 10 MPa, and the expression for calculating the strength coefficient on the Protodyakonov scale will be written as

f = R compress /10.

In laboratory conditions, the rock strength coefficient is determined by the crushing method developed at the IGD named after. Skochinsky. This method is more accurate compared to the method of Prof. MM. Protodyakonov. Rock crushing is carried out in a POG device, which is a metal cylinder 0.7 m long, which is placed on a metal cup. A sample (50-70 g) of crushed rock with an edge size of 10-15 mm is poured into a glass. A total of five such samples are accepted. Each sample is crushed in turn by dropping a load weighing 2.4 kg from a height of 0.6 m. The number of drops is taken from 5 to 15 depending on the expected strength of the rock.

All five portions of each portion of crushed material are poured onto a sieve with 0.5 mm holes, sifted, and the under-sieve product is poured into a metal volumetric cup. Then a rod with divisions is inserted into this glass, according to the readings of which the height of the column of crushed rock is determined h, see

Strength coefficient f calculated using the empirical formula:

f = 20n/h,

Wheren – number of load drops per hitch;

Protodyamkonov scale - rock strength coefficient scale.

Developed in the beginning 20th century It is one of the first breed classifications. It is based on measuring the labor intensity of their destruction during extraction.

Strength coefficient f on the prof. scale.

Table 1. Strength coefficient f on the prof. scale. Note. Characteristics of breeds from categories VIIa to X are omitted.

Protodyakonov intended to use such a classification as the basis for assessing the labor of a worker in the mining of coal and ores, and for rationing labor. He believed that with any method of rock destruction and method of its extraction, it is possible to evaluate the rock by the average extraction coefficient. If one of the two types of rocks is more labor-intensive to destroy, for example, by explosion energy, then the rock will be stronger during any process of its destruction, for example, by the teeth of a combine, a pick, the blade of a drill head during drilling, etc.

When developing such a scale, he introduced the concept of rock strength. In contrast to the accepted concept of the strength of a material, assessed by one of the types of its stress state, for example, temporary resistance to compression, tension, torsion, etc., the strength parameter allows you to compare rocks in terms of the complexity of destruction and extraction. He believed that with the help of this parameter it is possible to evaluate the totality of stresses of different natures acting during the destruction of a rock, as is the case, for example, during destruction by an explosion.

developed a rock strength coefficient scale. One of the methods for determining this coefficient was to test a rock sample for its compressive strength in kg/cm2, and the value of the coefficient was determined as one hundredth of the tensile compressive strength.

This method correlates quite well with the strength scale proposed for rocks of various strengths of the coal formation, rocks of medium strength, but is of little use when determining the strength coefficient of very strong rocks using this method. The strength scale is limited by a factor of 20, i.e., rocks with a temporary compressive strength of 200 kg/cm2, and for drain basalt, for example, this parameter is 300 kg/cm2. However, in the Soviet Union, the strength scale was widely used in assessing the complexity of rock destruction and is still used to this day. It is convenient for a relative assessment of the strength of a rock when it is destroyed using.

The method of relative assessment of rock by strength and labor intensity during its destruction, as noted by many, has disadvantages; it is not used abroad, but they cannot do without it in the Soviet Union and Russia.

The rock strength coefficient in the SI system is calculated using the formula:

where yc is the uniaxial compressive strength [MPa].

In contact with

Classmates

In my work, I often come across mining and geological forecast passports, where the most valuable information for me is the characteristics of rocks. Someone looks at disturbances, water inflow, profile, but for the calculation I need the power and compressive strength of the rocks. So, the idea for this entry arose when, instead of rock strength, I received the strength coefficient according to M.M. Protodyakonov. Here I want to tell you what the strength coefficient is, how it is calculated and how to obtain the compressive strength of rocks from it.

Rock strength- characteristics of the resistance of rocks to their extraction - technological destruction.

This concept of fortress was introduced by prof. MM. Protodyakonov, who proposed a strength coefficient to quantify it f, to a first approximation, proportional to the ultimate compressive strength of the rock. He developed a scale of rocks by strength, according to which all rocks are divided into 10 categories.

In the simplest case, the strength of rocks can be calculated using the formula:

$$f=\sigma_(szh) \times 10^(-7)$$

Where: σ compress- rock compressive strength, Pa

More precisely, the connection between σ compress And f in the area of ​​large values σ compress can be expressed by the empirical formula:

$$f=0.33 \times 10^(-7) \sigma_(sg) + 0.58 \times 10^(-3) \sqrt( \sigma_(sg))$$

There are other formulas for the relationship between the strength coefficient of rocks and their strength parameters. For example, the formula of L.I. Barona:

$$f=\frac(\sigma_(szh))(30) + \sqrt( \frac( \sigma_(szh))(3))$$

Here σ compress is measured in MPa, which is somewhat more convenient, because in practice geologists give characteristics of rocks where the strength is presented in these units.

Formula L.I. Barona is taken from a 1972 book, σ compress it was expressed in kgf/cm2, but with the transition to the SI system, the use of these units is not recommended, so the formula has undergone minor changes.

Now it's time to return to the question with which this entry began. How to obtain the compressive strength of rock from the strength coefficient? σ compress.

If you need to find out the approximate tensile strength, then everything is simple, multiply f by 10, we get σ compress in MPa.

But if we want to use empirical formulas f, difficulties may arise here, because It is not possible to simply substitute the value of the strength coefficient and obtain a strength characteristic from it.

In the work of A.S. Tanaino presents formulas for three intervals within 1 ≤ f≤ 20 from which you can calculate σ compress:

To be honest, I didn't bother using these formulas. Of course I checked them. When substituting boundary values ​​of intervals f we get σ compress, which differs by only 0.4 MPa in intervals 1 and 2, 2 and 3.

As a result, to find σ compress I used the MS Excel function - Selection of parameters. From my point of view, this is the most obvious and correct option for determining the compressive strength of rock through hardness f.

GOST 21153.1-75

Group A09

STATE STANDARD OF THE USSR UNION

MOUNTAIN ROCKS

Method for determining the strength coefficient
according to Protodyakonov

Rocks. Method for the determination
of strength factor according to Protodyakonov

Date of introduction 1976-07-01

ENTERED INTO EFFECT by Resolution of the State Committee of Standards of the Council of Ministers of the USSR dated September 25, 1975 N 2491

INSTEAD GOST 15490-70 regarding section. III

Verified in 1981. Validity period extended until 07/01/1986*

________________
* The validity period was removed by Decree of the USSR State Standard dated April 24, 1991 N 565 (IUS N 7, 1991). - Database manufacturer's note.


REISSUE November 1981 with Amendment No. 1, approved in July 1981 (IUS No. 9 - 1981)

This standard applies to hard rocks and establishes a method for determining their strength coefficient according to Protodyakonov for classifying rocks according to this indicator and using it in technical documentation when calculating and designing mining operations, mining equipment, as well as during research work.

The essence of the method is to determine the strength coefficient, which is proportional to the ratio of the work expended on rock crushing to the surface newly formed during crushing, estimated by the total volume of particles less than 0.5 mm in size.

1. SAMPLING

1. SAMPLING

1.1. Sampling - according to GOST 21153.0-75.

2. EQUIPMENT AND MATERIALS

2.1. To determine the strength of rocks, use:

a device for determining the strength of the POC (see drawing), consisting of a glass 1, a tubular impact driver 2 inserted into it, inside which a weight 3 weighing 2.4 ± 0.01 kg with a handle 4 tied to the weight with a cord is freely placed. The tubular pile driver has holes in the upper part into which pins 5 are inserted, limiting the lifting of the weight. The device includes a volume meter consisting of a glass 6 and a plunger 7 with a measurement scale with a reading range from 0 to 150 mm along its longitudinal axis;

sieve with mesh N 05 in accordance with GOST 6613-73 for sifting rock after crushing.

Drawing

3. PREPARATION FOR THE TEST

3.1. The selected rock sample is split with a hammer on a solid base to obtain pieces measuring 20-40 mm. Twenty samples weighing 40-60 g each are taken from the crushed material.

3.2. The number of drops of weights on each sample is set when crushing the first five samples.

3.3. Each sample is crushed separately in a glass with a weight falling from a height of 60 cm. The number of drops of the weight is taken depending on the expected strength of the rock, usually from 5 to 15 drops for each sample.

Notes:

1. For very soft rocks, the number of drops can be reduced to 1, and for very hard rocks - increased to 30.

2. When crushing, a glass with a tubular impact driver inserted into it must be placed on a rigid, massive base: reinforced concrete or asphalt floor, steel plate (weighing at least 20 kg, about 10 cm thick).


(Changed edition, Amendment No. 1).

3.4. The correctness of the selected test mode is monitored after sifting the first five crushed samples on a sieve until the release of the under-sieve product stops and its volume is measured in a volume meter. When a column of fines is obtained with a height of 20-100 mm on the plunger scale, the number of drops for each sample is saved for the remaining fifteen samples. With a smaller or larger height of the fines column in the volume meter, the number of drops is adjusted upward or downward, respectively.

4. CONDUCT OF THE TEST

4.1. The remaining fifteen samples are crushed in the device sequentially in the established test mode: with a constant number of weight drops and the lifting height of the weight is 60 cm.

4.2. After crushing every five samples, they are sifted on a sieve, the under-sieve product of the sieve is poured into a volume meter, the height of the column of fines is measured with a plunger and recorded.

(Changed edition, Amendment No. 1).

5. PROCESSING RESULTS

5.1. The rock strength coefficient () is calculated using the formula

where 20 is an empirical numerical coefficient that provides generally accepted values ​​of the strength coefficient and takes into account the work expended on crushing;

- the number of weight drops when testing one hitch;

- height of the fine fraction column in the volume meter after testing five samples, mm.

5.2. The arithmetic mean of the results of four determinations is taken as the final test result.

(Changed edition, Amendment No. 1).



The text of the document is verified according to:
official publication
Mountain rocks. Methods of physical tests: Sat. GOST. -
M.: Standards Publishing House, 1982

Protodyakonov intended to use such a classification as the basis for assessing the labor of a worker in the mining of coal and ores, and for rationing labor. He believed that with any method of rock destruction and method of its extraction, it is possible to evaluate the rock by the average extraction coefficient. If one of the two types of rocks is more labor-intensive to destroy, for example, by explosion energy, then the rock will be stronger during any process of its destruction, for example, by a combine tooth, pick, blade of a drill head during drilling, etc.

When developing such a scale, M.M. Protodyakonov introduced the concept fortress rock. Unlike the accepted concept strength of a material assessed by one of the types of its stress state, for example, temporary resistance to compression, tension, torsion, etc., the strength parameter allows you to compare rocks in terms of the complexity of destruction and extraction. He believed that with the help of this parameter it is possible to evaluate the totality of stresses of different natures acting during the destruction of a rock, as is the case, for example, during destruction by an explosion. M.M. Protodyakonov developed a scale for the rock strength coefficient. One of the methods for determining this coefficient was to test a rock sample for its compressive strength in kg/cm2, and the value of the coefficient was determined as one hundredth of the tensile compressive strength.

This method correlates quite well with the strength scale proposed by M.M. Protodyakonov for rocks of various strengths of the coal formation, rocks of medium strength, but is of little use when determining the strength coefficient of very strong rocks using this method. The strength scale is limited by a factor of 20, i.e. rocks with a temporary compressive strength of 2000 kg/cm2, and for drain basalt, for example, this parameter is 3000 kg/cm2. However, in the Soviet Union the strength scale M.M. Protodkonov was widely used in assessing the complexity of rock destruction and is still used to this day. It is convenient for the relative assessment of the strength of a rock during its destruction using drilling and blasting. The method of relative assessment of a rock by strength and labor intensity during its destruction has, as many have noted, disadvantages; it is not used abroad, but technical literature cannot do without it Soviet Union and Russia. The rock strength coefficient according to M.M. Protodyakonov in the SI system is calculated by the formula: fcr = 0.01 constr, where con is the uniaxial compressive strength [MPa].

Drilling- the process of constructing a cylindrical mining opening - a well, a hole or a mine shaft - by destroying rocks at the face; drilling is carried out, as a rule, in the earth's crust, less often in artificial materials (concrete, asphalt, etc.). In some cases, the drilling process includes fastening the walls of wells (usually deep ones) with casing pipes and pumping cement mortar into the annular gap between the pipes and the walls of the wells.

Well: a mine working of circular cross-section, drilled from the surface of the earth or from an underground working without human access to the face at any angle to the horizon, the diameter of which is much less than its depth. Wells are drilled using special drilling equipment. According to their purpose, wells are divided into: exploration, production, injection, auxiliary, special, blasting, support, parametric, and prospecting. Hole: an artificial cylindrical depression in a solid medium (rock) with a diameter of up to 75 mm and a depth of up to 5 m. They are created and used for placing charges during blasting operations, for installing anchor support, injecting water or cement into the surrounding rock mass, etc.

Classification of drilling methods. According to the nature of rock destruction, the drilling methods used are divided into: mechanical - the drilling tool directly affects the rock, destroying it, and non-mechanical - destruction occurs without direct contact with the rock from the source of impact on it (thermal, explosive, etc.).

Mechanical drilling methods are divided into rotational and impact (as well as rotary-impact and impact-rotary). During rotary drilling, the rock is destroyed due to the rotation of the tool pressed to the bottom. Depending on the strength of the rock, a cutting-type rock-cutting drilling tool is used during rotary drilling; diamond drilling tool; shot bits that destroy rock using shot. Impact drilling methods are divided into: impact drilling or impact-rotary drilling (drilling with rotary hammers, including submersible drills, percussion-rope, rod, etc., in which the rotation of the tool is carried out at the moment between impacts of the tool on the face); impact-rotational (with down-the-hole pneumatic and hydraulic hammers, as well as drilling with rotary hammers with independent rotation, etc.), in which blows are applied to a continuously rotating tool; rotational-impact, in which the rock-cutting drilling tool is under high axial pressure in constant contact with the rock and destroys it due to rotational movement along the face and periodically applied blows to it. Destruction of rocks at the bottom of a well is carried out over its entire area (solid bottom drilling) or along the annular space with core extraction (core drilling). Removal of destruction products can be periodic with the help of a bailer and continuous with augers, twisted rods or by supplying gas, liquid or solution to the face. Sometimes drilling is divided according to the type of drilling tool (auger, rod, diamond, roller, etc.); by type of drilling machine (perforating, pneumatic percussion, turbine, etc.), by method of drilling wells (inclined, cluster, etc.). Drilling equipment consists mainly of drilling machines (drilling rigs) and rock cutting tools. Among non-mechanical methods, thermal drilling has become widespread for drilling blast holes in quartz-containing rocks, and work is underway to introduce blast drilling.