1. Selecting a shape and calculating sizes cross section production

When carrying out workings, two types of mining operations are distinguished: main and auxiliary.

The main mining operations are those that are performed in the face of the workings and relate directly to the excavation and securing of the workings.

Auxiliary operations are those that provide normal conditions for performing the main tunneling operations.

The cross-sectional area of ​​the excavation depends on the purpose and dimensions of the equipment located in it. There are cross-sectional areas of horizontal workings in the open, rough and after excavation. The clear area is determined by the dimensions of the excavation up to the support, minus the areas occupied by the ballast layer and ladder in the excavation cross-section. The rough area is the designed area in the excavation. When determining this area, the area occupied by the support, ballast layer, ladder and tie (with frame supports installed staggered) is added to the clear area. The actual area that is obtained as a result of excavation is usually 3-5% or more greater than the designed area.

The cross-sectional dimensions (width and height) of haulage workings depend on overall dimensions haulage cars and electric locomotives, from the rail tracks, the method of movement of workers in the workings and the amount of air supplied for ventilation.

If there are rail tracks in the excavation for the movement of people, a path (passage) with a width of at least 700 mm is provided, which must be maintained at a height of 1800 mm from the level of the ladder (ballast layer).

Based on specific conditions: f =16; stability - average; service life of the excavation is 16 years, we choose a vaulted excavation shape, sprayed with concrete fastening

1. Calculate the cross-section of the excavation height.

a. Height of the rail track structure h 0, mm

h 0 = h b + h w + h p + h p, mm;

Where: h 0 - the height of the upper structure of the excavation path, is selected according to the standards stipulating ESP, mm;

h b - height of the ballast layer, mm;

h p - height of the lining under the rail, mm;

h r - height of the rail track, mm;

h 0 = 100 + 420 + 20 + 135 = 375 (mm).

2. Height of rolling stock h, mm

3. Height of the straight-walled section of the excavation.

h 1 = 1800 (mm).

4. Clear height of excavation.

h 2 = h 1 +h b +1/3h w, mm;

h 2 =1800+135+20+1/3*120=1995 (mm).

Where: h 1 - height of the straight-walled excavation section, mm;

h b - height of the ballast layer, selected according to the standards stipulating ESP, mm;

h w - height of the sleeper beam, mm;

5. The height of the workings in the blacker.

h 3 = h 0 + h 1, mm;

h 3 =375+1800=2175 (mm).

6. Clear height of the vaulted ceiling.

h h =1/3*V, mm;

h h =1/3*2250=750 (mm).

7. The height of the vaulted ceiling in the basement.

h 5 = h h + T cr. , mm;

h 5 =750+50=800 (mm).

8. The clear width of the excavation is calculated.

B= n+A+m, mm;

H=200+1350+700=2250 (mm).

Where: B is the clear width of the excavation, mm;

n is the gap between the support and the rolling stock, mm;

A is the width of the rolling stock, mm;

m - free passage for people, mm;

9. Width of working in the black.

B 1 =B+2* T cr. , mm;

B 1 =2250+100=2350 (mm).

10. Clear cross-sectional area.

S St. = V*(h 2 +0.26*V)

S St. = 2250*(2745+0.26*2250) =7.4 m2

11. Cross-sectional area in black.

S black = V 1 *(h 3 +0.26* V 1)

S black = 2350*(2960+0.26*2350) =8.3 m2

12. Air flow speed.

V = Q air / S c in, m/s;

V = 18/7.4 =2.4 m/s;

Where: V is the speed of movement of the ventilation stream through the excavation, regulated by safety rules, m/s;

Q air - the amount of air passing through the workings, m 3 /s;

S c in - cross-sectional area of ​​the excavation in the open, m 2 ;

Since V = 2.4 m/s, then 0.25? V? 8.0 satisfies the requirements of the HPB, therefore, this section was calculated correctly.

13. Section in the penetration.

S pr =1.03* S black, m

S pr =1.03* 8.3 =8.7 (m)

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For horizontal mining exploration workings Two forms of cross sections are established: trapezoidal (T), rectangular-vaulted with a box vault (PS).

There are cross-sectional areas of horizontal workings in the open, in the tunnel and in the rough. The clear area (5 SV) is the area enclosed between the excavation support and its soil, minus the cross-sectional area that is occupied by the ballast layer poured onto the excavation soil.

The area in the excavation (5 P|)) is the area of ​​the excavation, which is obtained during the process before the construction of support, laying of the rail track and installation of the ballast layer, laying of utilities (cables, air, water pipes, etc.). Rough area (5 8H) - the excavation area that is obtained during the calculation (design area).

Since 5 HF = 5 SV + 5 cr, then the calculation of the cross-sectional area of ​​the excavation begins with a calculation in the open, where 5 cr is the cross-section of the excavation occupied by the support; Кп„ - coefficient of cross-section search (coefficient of excess cross-section - KIS).

The dimensions of the cross-sectional area of ​​horizontal workings in the clear are determined based on the placement conditions transport equipment and other devices, taking into account the necessary clearances regulated by the Safety Rules.

In this case, it is necessary to consider the following possible cases of excavation and cross-section calculation:

1. Development is carried out with fastening and loading machine works in a fixed working area. In this case, the calculation is carried out based on the largest dimensions of the rolling stock or loading machine.

2. The excavation is traversed with support, but the support lags behind the face by more than 3 m. In this case, the loading machine operates in the unsupported part of the excavation.

When calculating the dimensions of the cross-sectional area based on the largest dimensions of the rolling stock, it is necessary to make a verification calculation (Fig. 11):

t + B + p">2nd + 2*2+ T+ In the village+ P; N r + th 3 > Az +<* + And-

A breakdown of the data is given below.

3. The working is carried out without fastening. Then size it up! cross sections calculated
are based on the largest dimensions of tunneling equipment or mobile
composition.

The main dimensions of underground vehicles are standardized with the aim of typifying the sections of workings, the design of support and tunneling equipment.

For trapezoidal-shaped workings, standard sections have been developed using solid support, staggered support, with only the roof tightened, and with the roof and sides tightened.

Typical sections of rectangular-vaulted workings are provided without support, with anchor, shotcrete and combined support

Rock pressure

Creating safe operating conditions for underground structures is one of the main tasks of ensuring the sustainability of mine workings. The technogenic impact of mining on the geological environment leads to its new state. (The geological environment here refers to the real physical (geological) space within the earth’s crust, which is characterized by a certain set of geological conditions - a set of certain properties and processes).

Quantitatively and qualitatively new force fields arise around the geological object as part of the geological environment, which manifest themselves at the boundary between the mine workings and the rock mass, i.e. within small limits of the rock mass surrounding the mine.

The forces arising in the massif surrounding the mine opening are called rock pressure. The rock pressure around the workings is associated with the redistribution of stresses during their construction. It manifests itself in the form;

1) elastic or elastic-viscous displacement of rocks without their destruction;

2) landslide formation (local or regular) in weak, fractured and

finely layered rocks;

3) destruction and displacement of rocks (in particular, rock formation) under the influence of extreme stresses in the massif along the entire perimeter of the excavation section or in its individual sections;

4) extrusion of rocks into the excavation due to plastic flow, in particular from the soil (rock heaving).

The following types of rock pressure are distinguished:

1. Vertical - acts vertically on the support, backfill mass and is a consequence of the pressure of the mass of overlying rocks.

1. Lateral pressure is part of the vertical pressure and depends on the thickness of the rocks lying above the excavation or the seam being developed, and the engineering and geological characteristics of the rocks.

3. Dynamic - occurs at high rates of application of loads: explosion, rock burst, sudden collapse of roof rocks, etc.

4. Primary - rock pressure at the time of excavation.

5. Steady - the pressure of rocks after the excavation has passed after some time and does not change for a long period of its operation.

6. Unsteady - pressure that changes over time due to mining operations, rock creep and stress relaxation.

7. Static - rock pressure in which inertial forces are absent or very small.

The increasing complexity of the conditions in which mining (underground construction) is carried out (great depths of development, permafrost, high seismicity, neotectonic phenomena, acceleration and increase in the volume of technogenic impact, etc.), and the level of development of science have made it possible to create modern ones that are closer to real ones. methods for calculating rock pressure.

A new scientific direction has emerged - the mechanics of underground structures. This is a book about the principles and methods of calculating underground structures for strength, rigidity and stability under static (rock pressure, groundwater pressure, temperature changes, etc.) and dynamic (blasting, earthquakes) influences. She develops methods for calculating support structures.

The mechanics of underground structures arose as a result of the development of rock mechanics - a science that studies the properties and patterns of changes in the stress-strain state of rocks in the vicinity of a working, as well as the patterns of interaction of rocks with the support of mine workings to create appropriate methods for controlling rock pressure. The mechanics of underground structures operates with mechanical models of the interaction of the support with the rock mass, taking into account the geological state of the rocks surrounding the excavation, and design diagrams of the support.

Analysis of mechanical models and calculation schemes is carried out using methods of the theory of elasticity, plasticity and creep, fracture theory, hydrodynamics, structural mechanics, strength of materials, theoretical mechanics.

For horizontal mining and exploration workings, two cross-sectional shapes have been established: trapezoidal (T) and rectangular-vaulted with a box vault (PS). In Fig. 9-10 show typical sections of mine workings of various shapes.

There are cross-sectional areas of horizontal workings in the open, in the tunnel and in the rough. Clear area (S CB) - this is the area enclosed between the excavation support and its soil, minus the cross-sectional area that is occupied by the ballast layer poured on the excavation soil (if any).

The area in the excavation (5 pr) is the area of ​​the excavation, which is obtained during the process before the construction of support, laying of the rail track, installation of the ballast layer and laying of utilities (cables, air, water pipelines, etc.). Rough area (S BH) - excavation area, which is obtained during the calculation (design area).

The permissible excess of the area in the excavation over the design (draft) is given in table. 2.

table 2

Rice. 9.1. Typical section of trapezoidal workings with wooden support: a - scraper delivery of rock; b - conveyor delivery of rock; c - manual removal of rock; g - locomotive haulage of rock; d - two-track working with locomotive haulage of rock

Rice. 10. Typical cross-section of workings with monolithic concrete support with locomotive haulage of rock: a - single-track; b - two-way

Rice. 9.2. A typical cross-section of rectangular-vaulted workings without fastening or with anchor (sprayed concrete) fastening: a - scraper delivery of rock; b - conveyor delivery of rock; c - manual removal of rock; G - locomotive haulage of rock; d - two-track development with locomotive

rock removal

Thus, the cross-sectional area of ​​the excavation in the tunnel

or, on the other hand,

Because S B4 = S CB + S Kр, then the calculation of the cross-sectional area of ​​the excavation begins with calculation in the open, where S Kp- section of the excavation occupied by the support; K p- coefficient of cross-section enumeration (coefficient of excess section - CIS).

The dimensions of the cross-sectional area of ​​horizontal openings in the clear are determined based on the conditions for placing transport equipment and other devices, taking into account the necessary clearances regulated by the Safety Rules.

In this case, it is necessary to consider the following possible cases of excavations and cross-section calculations:

• 1. The excavation is traversed with support, and the loading machine operates in the secured excavation. In this case, the calculation is carried out based on the largest dimensions of the rolling stock or loading machine.
• 2. The excavation is traversed with support, but the support lags behind the face by more than 3 m. In this case, the loading machine operates in the unsupported part of the excavation.

When calculating the dimensions of the cross-sectional area based on the largest dimensions of the rolling stock, it is necessary to make a verification calculation (Fig. 11):

A breakdown of the data is given below (Table 5).

3. The working is carried out without fastening. Then the cross-sectional dimensions are calculated based on the largest dimensions of the tunneling equipment or rolling stock.

The main dimensions of underground vehicles are standardized in order to typify the sections of workings, the design of support and tunneling equipment.

For trapezoidal-shaped workings, standard sections have been developed using solid support, staggered support, with only the roof tightened, and with the roof and sides tightened.

Typical cross-sections of rectangular-vaulted workings are provided without support, with anchor, shot-concrete and combined support.

The main dimensions of typical sections of workings of type T and PS are given in Table. 3 and 4.

Table 3

Main cross-sectional dimensions of trapezoidal workings (T)

Designation	Section dimensions, mm				Designation	Section dimensions, mm
				Clear cross-sectional area, m2					Clear cross-sectional area, m2

Table 4

Main cross-sectional dimensions of rectangular-vaulted workings

forms (PS)

Designation	Section dimensions, mm					Clear cross-sectional area, m2

Rice. 11. Schemes of the operating conditions of the loading machine at the face: a - in an unsecured bottom-hole space; b - in a fixed bottom-hole space

Calculation formulas for determining the cross-sectional dimensions of workings of types T and PS are given in Table. 5, 6.

Table 5

Trapezoidal workings

		Designation	Calculation formulas
	Transport equipment		Selected from catalogs
	Free passage
	From soil to rail head		h =hi + h p + 1/3 /g sh
	Ballast layer (ladder)
	Workings from the rail head		Selected
	to the top		in accordance with PB
	Productions in the world:
	without track
	during scraper removal of rock
	during conveyor delivery of rock		h 4 = h + hi
	if there is a rail track:
	without ballast layer		h4 = h + hi
	with ballast layer		h4 = h+ L3-L2
	Rough workings:
	without ballast layer		hs = h 4 + d + ti
	with ballast layer		hs = h 4 + hi + d + ti
	Transport equipment		From equipment catalogs
	Free passage at height h		Selected in accordance with the safety regulations
	Passage at the level of transport equipment
	In light at the level of transport equipment:
	during scraper cleaning		b = b + 2t
	single-track		b = B + t + n
	double track		b = 2B + c + t-p
	Workings in the open along the upper gorge: without a rail track		b = b-2(h-H) ctga
	if there is a rail track		B=b- 2(hi - H) ctga
	On the sole:
	without track		bi = b + 2H ctga
	in the presence of a rail track without ballast layer		Z>2 = 6 + 2(#+/ji)ctga
	with ballast layer		Z>2 = 6 + 2(#+/ji)ctga

		Designation	Calculation formulas
	Rough workings:
	upper base		b3 = b+2 (d+ t 2) sina
	lower base with ballast layer	Ba	Ba = b3 +2 hs ctga
	without ballast layer		Ba = b 2 + 2 (d + t 2) sina
	Between transport equipment		Selected according to PB
	eat and the wall of the excavation		(T> 250 mm, With> 200 mm)
	Between rolling stock
	Racks, top made of round timber
			Estimated
Distance, mm	From the axis of the track (conveyor) to the axis of the excavation: single-track		k = (u + S2 )-Y2
	double track		k = S2 -(u+s2 )
	Cross section: clear		R= b+ 62 + 2Л4/sin a
			Pi = bz+ bа + 2/r5/sin a
	Cross section: clear		S CB = /24(61 + b 2 )l2
			S m = /25(63 + 6 4)/2

Table 6

Rectangular-vaulted workings

		Designation	Calculation formulas
	for shot concrete, rod and combined support		ho = bl4
	with concrete support		ho = b/2
	Productions in the world:
	without track:
	during scraper removal of rock		h 4= h + ho
	with a conveyor		h 4 =h + /?2 + ho
	with a rail track: without ballast layer		h 4 = h+ /?2 + ho
	with ballast layer		h 4= h + ho
	Rough workings		hs= h+ hi + ho +1
	Rough working walls:
	during scraper removal of rock
	with ballast layer (ladder)		he = h+ hi
	Transport equipment		Selected from catalogs
	Productions in the world:
	single-track		b=B+ m+n
	double track		b = 2B + c + m + n
	Rough workings		bo = b + 2t
	Axial arc of the arch:
	at ho = N4		R = 0.%5b
	at ho= Y 3		R= 0,6926
	Lateral arch:
	at ho = YA		r = 0,1736
	at ho = ЪЪ		r = 0.262b
Perimeter transverse production,
	at ho = YA: without ballast layer		P = 2he+ 1,219
	with ballast layer at ho = b/3: without ballast layer		P = 2h+ 1,219 P = 2he + 1,33 b
	with ballast layer		P = 2h+ 1,33 b

		Designation	Calculation formulas
Perimeter transverse production,	Roughly: at ho = Н4 at ho = ы 3		/>1=2*6+1,19*0 />! = 2*6+1,33 bo
Cross-sectional area of ​​the excavation, m 2
	at ho = YA at ho = Y 3		S CB = b(h + 0.15b) S CB = b(h + 0.2b)
	without support or rod support		SB4= b(h 6 +0,n5b)
	with shot-concrete and combined lining with concrete lining of a rectangular part of the excavation		SB4= bo(h 6 +0.15b)S B h = S CB + S+ S 2 +S3 S= 2A 6 /[
	vaulted part of the excavation		S 2 = 0.157(1 + Ao/6)(6i 2 -6 2)
	subsoil support	S3	Si = 2/27/ + hg(t)-t)
Dimensions of the subsoil part of the support			Selected depending on the properties of the rocks and width
	Cutting height		production

All horizontal excavations along which cargo is transported must have gaps in straight sections between the support or equipment located in the excavation, pipelines and the most protruding edge of the rolling stock gauge of at least 0.7 m (n> 0.7) (free passage for people), and on the other side - at least 0.25 m (t> 0.25) for wooden, metal and frame structures, reinforced concrete and concrete support and 0.2 m - for monolithic concrete, stone and reinforced concrete support.

The width of the free passage must be maintained at a working height of at least 1.8 m (h = 1,8).

In mines with conveyor delivery, the width of the free passage must be at least 0.7 m; on the other side - 0.4 m.

The distance from the upper plane of the conveyor belt to the top or roof of the excavation is at least 0.5 m, and for tension and drive heads - at least 0.6 m.

Gap With between oncoming electric locomotives (trolleys) along the most protruding edge - at least 0.2 m (With> 0.2 m).

In places where trolleys are coupled and uncoupled, the distance from the support or equipment and pipelines placed in the excavations to the most protruding edge of the rolling stock gauge must be at least 0.7 m on both sides of the excavation.

When rolling by contact electric locomotives, the height of the contact wire suspension must be at least 1.8 m from the rail head. At landing and loading and unloading areas, at the intersections of excavations with excavations, where there is a contact wire and along which people move - at least 2 m.

In the near-shaft yard - in places where people move to the landing site - the height of the suspension is at least 2.2 m, in other near-shaft workings - at least 2 m from the rail head.

In near-shaft yards, in main haulage workings, in inclined shafts and slopes, when using trolleys with a capacity of up to 2.2 m 3, R-24 type rails should be used.

Mine rail tracks during locomotive haulage, with the exception of workings with heaving soil and with a service life of less than 2 years, must be laid on crushed stone or gravel ballast made of strong rocks with a layer thickness under the sleepers of at least 90 mm.

For adits and other underground mine workings, the following concepts are distinguished: “rough” cross-sectional area - without fastening; “in the light” - fixed development; “in the tunnel” - taking into account the inaccuracies in breaking the contours of the mine workings, approximately 10% larger than the “rough” section. When driving, adhere to standard sizes workings in its cross section, which is given either a trapezoidal shape when wooden support is used or vaulted-rectangular when using concrete support

The “rough” cross-sectional area is calculated taking into account the diameter of the support elements and the width of the gaps between the support and the walls of the excavation. The cross section is also selected based on the use of support, the height of the excavation, the gaps between the support and the side rocks, the height and width of the haulage equipment, the width of the free passage, and the height of the ballast layer. To calculate the width of the excavation along the roof and base and the cross-sectional area, the permissible gaps between the walls, the roof of the excavation and the haulage equipment are taken into account, which are established on the basis of safety requirements and are given in the reference literature.

All horizontal mine workings are driven with some elevation (0.002-0.008) to remove water from the workings by gravity.

A drift is a horizontal excavation that does not have direct access to the earth’s surface, passing along the strike of mineral bodies when they are inclined, and when the body is horizontal, in any direction along the length of the deposit.

A crosscut is a horizontal excavation that does not have direct access to the earth's surface, passing through the host rocks or along the body of a mineral at an angle to their strike, most often across the strike.

Ort goes through the power of the mineral and does not go beyond its limits.

The cut is made from another excavation at any angle to the mineral body, and may extend beyond its limits. The length is usually small and does not exceed 20-30m.

Vertical workings.

A pit is a vertical excavation with a square, rectangular or round cross-section (round-section pits are called dudok), which has direct access to the earth’s surface. The pits often lead to horizontal workings: cuttings, crosscuts, drifts.

Has standard dimensions in light and most often rectangular shape cross section (Fig. 5, 6; Table 2). The cross-sectional area of ​​a pit generally depends on its depth. Shafts with a cross-section of 0.8 and 0.9 m2 are drilled to a depth of up to 20 m, pits with a cross-section of 1.3 m2 are drilled to a depth of up to 30 m, 3.2 m2 are designed to be drilled to a depth of up to 40 m. The cross-sectional area and dimensions of the pit are roughly determined in depending on the thickness of the support. The actual cross-sectional area in the penetration is somewhat larger. An increase in area by 1.04-1.12 times is allowed.

The tunneling unit, as a rule, consists of three people: two on the surface, one in the hole; with a cross-sectional area of ​​more than 2 m2, two tunnelers can work at the face.

The mine shaft has a larger cross-section than the pits and greater depth. The cross-sectional shape is usually square, ranging in size from 4-6 to 10-16 m2 (depending on the depth, volume of work and deadlines). Has access to the day surface; In some cases, the mine shaft is driven from horizontal underground workings, such as adits, and are called “blind”.

Gesenk, unlike a mine shaft, does not have direct access to the surface and is used to lower loads and people from the upper to the lower horizons.

Inclined workings.

The slope follows the dip of the mineral deposit. When extracting minerals, it is usually used to lift loads from the lower horizon to the upper one.

Bremsberg also goes along the fall of the mineral deposit, but unlike the slope, it is used to lower loads and people from the lower to the upper horizon.

An uprising excavation is a working that does not have access to the day surface and runs from bottom to top at any angle.

2. Methods and means of conducting tunneling work

2.1. Mining characteristics and classifications of rocks

The physical and mechanical properties of rocks are the main factors determining the choice of equipment and mining technology. The most significant of these properties include strength and stability.

Strength is a complex characteristic of rocks, characterizing their resistance to destruction and depending on properties such as hardness, viscosity, fracturing, and the presence of interlayers and inclusions. The concept of fortress was introduced by prof. M. M. Protodyakonov, who proposed using the strength coefficient f to quantify it. To a first approximation, the value of f is inversely proportional to the ultimate compressive strength of the rock. Since the strength coefficient is related to the strength of rocks, it can be calculated in the simplest case using the formula

where is the compressive strength of rocks, Pa, for many rocks it ranges from 5 to 200 MPa.

Based on their resistance to destruction from external forces, rocks are classified according to relative strength, specific work of destruction, drillability and explosiveness.

The classification of rocks by strength was developed by M. M. Protodyakonov in 1926. According to this classification, all rocks are divided into 10 categories. The first category includes rocks of the highest strength (f = 20), the tenth category includes the weakest floating rocks (f = 0.3),

The choice of method for explosive removal of rocks from a massif is influenced by explosiveness, which is understood as the resistance of the rock to destruction by explosion. Explosibility is determined by the amount of standard explosive required to destroy rock with a volume of 1 m3 (an indicator of specific explosive consumption). To determine the specific consumption of explosives (kg/m3) in relation to specific rocks, use various classifications rocks by explosiveness, for example, the Unified classification of rocks by drillability and explosiveness of prof. A. F. Sukhanova.

The drillability of a rock characterizes its ability to resist the penetration of a drilling tool into it and the intensity of the formation of a hole or hole in the rock under the influence of forces arising during drilling. The drillability of the rock is characterized by the drilling speed (mm/min), less often - by the duration of drilling 1 m of hole (min/m).

A unified classification of rocks by drillability was developed by the Central Bureau of Industrial Labor Standards to regulate mining exploration work. Drillability is the resistance of rock to the destructive action of a tool during the drilling process.

The main criterion for assigning rocks to one or another category in terms of drillability is the machine time for drilling a 1 m hole under standard conditions. In this classification, rocks are divided into 20 categories, and according to drillability they are classified only within categories IV-XX. Breeds I-III categories It is intended to be developed using jackhammers.

Other classifications have been developed to calculate standards and various consumption indicators in relation to individual production processes(for example, the Unified classification of rocks according to drillability and explosiveness, which is based on drilling speed and specific consumption explosives).

The stability of rocks is their ability to maintain balance when exposed. The stability of rocks depends on their structure and physical and mechanical properties, the magnitude of stresses arising in the rock mass. Rock stability is one of the main criteria for selecting underground mining systems, determining its parameters and methods of securing mine workings.

Based on their stability, rocks are conventionally divided into five groups.

Very unstable rocks that do not allow exposure of the roof and sides of the mine. These include floating, loose and loose rocks.

Unstable rocks that allow some exposure of the sides of the excavation, but require the construction of support after the excavation. Such rocks include wet sands, weakly cemented gravel, waterlogged or heavily destroyed rocks of medium strength.

Rocks of average stability, allowing exposure of the roof over a relatively large area, but requiring the installation of support during prolonged exposure. These are fairly compacted soft rocks of medium strength, less often strong and fissured.

Stable rocks allow the roof and sides to be exposed over a large area; maintenance is required only in selected areas. These are soft, medium strength and strong breeds.

Very stable ones allow exposure over a large area and for a long time (tens of years) without maintaining them. There is no need to secure excavations in such rocks.

Table 3

Unified classification of rocks according to drillability with drill hammers and electric drills for standardization of mining work

Name of breeds:

I 0.1 Clay is dry, loose in dumps. Loess is loose and wet. Sand. Sandy loam is loose. Peat and plant layer without roots.

II 0.3 Gravel. The loam is light, loess-like. Peat and plant layer with roots or with a small admixture of small pebbles and crushed stone.

III 0.5 Pebbles ranging in size from 10 to 40 mm. The clay is soft and oily. Sandy-clayey soils. Dresva. Ice. The loam is heavy. Crushed stone of various sizes.

IV 0.8-1.0 Pebbles ranging in size from 41 to 100 mm. The clay is schistose, moraine. Pebble-crushed stone soils bound by clay. Sandy-clayey soils bound by clay. Sandy-clayey soils with the inclusion of pebbles, crushed stone and boulders. Salts are fine- and medium-grained. Heavy loams with an admixture of crushed stone. The coals are very soft.

V 1.2 Clayey siltstones, weakly cemented. The mudstones are weak. Conglomerates of sedimentary rocks. Manganese oxide ores. Clay marl. Frozen rocks of categories I-II. Sandstones, weakly cemented with sandy-clayey cement. The coals are soft. Small nodules of phosphorite.

VI 1.6 Gypsum is porous. Dolomites affected by weathering. Iron ore is blue. Talvanized limestones. Permafrost categories III-V. Cretaceous rocks are soft. Marl is unchanged. The ores are ocher-clay with the inclusion of brown iron ore nodules up to 50%. Pumice. Shales are carbonaceous. Thrill. Coals of medium strength with clearly defined bedding planes

The cross-sectional area in light is the area limited by the internal. The contour of the support and on top of the ballast layer of the rail track (without taking into account the thickness of the support)

Rough sectional area - the area along the outer contour of the support, including the tightening and the soil of the excavation.

The area limited by its design contour is determined by adding the clearance dimensions in the light with the thickness of the support, taking into account the thickness of the tightening and backfilling.

The cross-sectional area of ​​the excavation in the tunnel is the area limited by the contour of the excavation in the face (it is taken to be 3-5% larger than the rough area).

15. Stability of rocks (loose, cohesive, rocky).

Based on the nature of the connection between solid particles, soils are divided into granular, cohesive and rocky.

Loose, non-cohesive soils are characterized by a lack of cohesion between particles, significant water permeability, low compressibility, high internal friction forces and rapid deformation under load.

Cohesive soils have low water permeability;

The presence of water in them determines the molecular forces of adhesion. Therefore, cohesive soils are characterized by significant cohesion between particles, large deformations under load and duration of deformations.

In rocky soils, their particles are rigidly bound together by a cementing substance, and this bond is not restored if it is broken.

The properties of soils have a significant impact on the nature of their development and the performance of machines. In this regard, when choosing the type of machine for excavation work, it is necessary to take into account the characteristic properties and condition of the soil being excavated. From this point of view, the most important properties of soils - resistance to development and their stability as a base on which the machine is installed - are determined mainly by the granulometric composition and physical and mechanical properties of the soil.

work, it is necessary to take into account the characteristic properties and condition of the soil being developed.

From this point of view, the most important properties of soils - resistance to development and their stability as a base on which the machine is installed - are determined mainly by the granulometric composition and physical and mechanical properties of the soil.

The granulometric composition of soil is characterized by the percentage content by weight of particles of various sizes. The size of individual particles of non-rocky soils is: pebbles 40 mm; gravel 2-40 mm; sand 0.25-5 mm;