RU2818646C1 - Mine rock ground support reinforcement method - Google Patents

Abstract

FIELD: mining industry.

SUBSTANCE: invention relates to methods of reinforcing rock massifs and can be used in reinforcing the surface of elements of buildings and structures. Method includes placement of steel anchor elements with heads in rock. At least two rod steel anchor elements are arranged perpendicular to direction of crack opening on both sides of it. Anchor elements are tightened by rigidly elastic ties, thus forming a cellular structure with an arbitrary shape of cells. One end of each of the ties is hinged to the head, and the other end is coupled end-to-end by a tie nut-coupling with the neighboring tie. On the free ends of the ties there are threaded sections provided on one tie with a left thread, and on the opposite tie—right-hand thread. Nut-coupling is made at one end with left-hand thread, and at the other end—with right-hand thread.

EFFECT: termination of intensive growth of fracture due to reduction of potential energy of its opening and increase of modulus of elasticity of rock surface near fracture.

1 cl, 3 dwg, 1 tbl

Description

The invention relates to the field of mining, in particular to methods for strengthening rock masses, and can be used to reinforce the surface of elements of buildings and structures.

There is a known method of reinforcing massifs (soils, foundations of structures) with unconnected rod elements located in the body of the massif (Korobova O.A. Strengthening foundations and reconstruction of foundations. - Novosibirsk State Architecture. - Construction University. Novosibirsk: NGASU (Sibstrin), 2008. 332 pp.).

The disadvantage is the impossibility of preventing the destruction of rock along cracks on the surface of the massif, for example, on the roof of a mine opening, due to the inability to localize the intensive growth of the rock mass with the indicated structures near a single crack. In addition, the arrangement of these structures on the roof of a mine opening is difficult and costly.

There is a known method of strengthening the end parts of reinforced concrete sleepers by additional reinforcement with frames, which includes placing a structure of fixedly interconnected rods (frames) before the sleeper molding process, inside the sleeper array (RF patent No. 2716373, IPC E01B 3/32).

The disadvantage of this method is the impossibility of preventing the destruction of rock through cracks that appear randomly in the rock, due to the inability to determine in advance the location of the crack. In addition, the construction of structures with a frame recessed into the body of the rock mass on the roof of the mine opening is expensive.

The closest analogue to the claimed one is the method described in the device for cable protection of a slope, including a rocky slope, using splints, containing tie-down cables stretched on the surface of a mountain range, located at the intersection to form a mesh and units for fixing the ends of the cables to the surface of the slope, consisting, among other things, of rod elements (RF patent No. 186994, IPC E02D 17/20).

The disadvantage is that its use does not make it possible to prevent the destruction of a fractured rock mass due to the unhindered, intensive development of cracks due to the lack of rigid fixation of the crack in the rock due to the lack of rigidity of the device’s structural elements (cables, cable loops, splices). In addition, the placement of the specified device on the roof of the mine opening is associated with the tension of the cables and, for this reason, is difficult to implement and costly.

The technical problem solved by the claimed method is to prevent the destruction of fractured rock by ensuring the proper level of critical potential energy of the surface of the rock mass.

The technical result consists in applying measures to ensure the cessation of intensive crack growth by reducing the potential energy of its opening and increasing the elastic modulus of the rock surface near the crack by placing rigid-elastic ties on the side of the protruding parts of the rod anchor elements that are not part of the rock.

The problem is solved by the fact that the method of strengthening rock with mine support, including placing steel anchor elements with heads in the rock, according to the change, at least two rod steel anchor elements are placed perpendicularly on both sides of the crack, tightened with rigid-elastic ties, forming in this case, a cellular structure with an arbitrary shape of cells, and one end of each of the ties is hinged in the head, and the other end is made with a threaded section to ensure a rigid connection with the tie of the adjacent anchor element.

The essence of the design that ensures the implementation of the method is illustrated by drawings.

In fig. 1 schematically shows the location of a crack in the rock and rod steel anchor elements with rigid-elastic ties on the roof of the mine opening, where 1 - crack, 2 - rod steel anchor elements, 3 - rigid-elastic ties with an elongated coupling nut 4 , 5 - roof of the mine workings; 6 - rock.

In fig. 2 schematically shows the layout of the mine support along the mine arch, where 1 - crack, 2 - rod steel anchor elements, 3 - rigid-elastic couplers with an elongated coupling nut 4, 5 - mine arch; 6 - rock, 7 - mine workings.

In fig. Figure 3 shows a structural element of the proposed mine support, where 2 is a rod steel anchor element, 3 is rigid-elastic ties, 8 is a head, 9 is threaded sections of rigid-elastic ties, 10 is loop-shaped sections of rigid-elastic ties.

The proposed method of strengthening rock with mine support is intended to prevent intensive propagation of crack 1 (Fig. 1, 2). The structural element of the mine support consists of a rod steel anchor element 2 (Fig. 1-3), on the end of which is not included in the rock, a perforated steel disk-shaped head 8 is mounted (Fig. 3), in which from 4 to 6 through holes are made along the perimeter for hinged fastening to it of rigid-elastic couplers 3 (Fig. 1-3) with their loop-shaped sections 10 (Fig. 3). The method of strengthening rock with mine support can also be useful for fastening the latter to the arch 5 (Fig. 1, 2) of the mine working 7 (Fig. 1).

The method of strengthening rock with mine support is carried out as follows.

Upon visual detection of a crack 1 (Fig. 1, 2) on the roof 5 (Fig. 1, 2) of the mine workings 7 (Fig. 2), as well as previously in potentially dangerous places in the rock 6 (Fig. 1, 2), the drillers holes - holes with a length of h = 2050 mm (Fig. 1). Their number and location are selected depending on various criteria: the nature of the crack, its size, rock properties, etc. The holes are made in pairs so that they are on both sides and perpendicular to the location of the crack 1 and the possible direction of its opening at a distance t (Fig. 1) equal to 1000 mm from each other. Rod steel anchor elements 2 (Fig. 1-3), made, for example, of steel grade St3, are installed in the holes until they stop in the perforated heads 8 (Fig. 3). Next, each rigidly elastic tie 3 (Fig. 1-3) of the structural element (Fig. 3), hingedly attached to the head 8 (Fig. 3) of the rod steel anchor element 2 (Fig. 1-3), is articulated end to end at using an elongated coupling nut (hereinafter referred to as coupling nut) 4 (Fig. 1-2) with an adjacent rigid-elastic coupler 3 located on the other side of the crack.

The rigid connection of the opposing rigid-elastic couplers 3 is carried out using a coupling nut 4 (Fig. 1, 2). To do this, at the free ends of the rigid-elastic couplers 3 there are threaded sections 9 (Fig. 3), equipped on one coupler with a left-hand thread, and on the opposite coupler with a right-hand thread. The coupling nut 4 (Fig. 1, 2) is also made from one end with a left-hand thread, and from the other end - with a right-hand thread. As a result, the coupling nut 4, when simultaneously screwed onto both opposing rigidly elastic ties 3, reduces the distance between the rod anchor elements 2 (Fig. 1-3), tightening them at the same time.

In a particular case, if it is necessary to prevent the appearance of new cracks 1 (Fig. 1, 2) with their unpredictable direction, a larger number of structural elements are used (Fig. 3) to form a mesh structure of the mine support, formed by several rod steel anchor elements 2 and a number of rigid - elastic ties 3 (Fig. 1-3). In this case, it is possible to obtain a mesh structure of mine support with a triangular and diamond-shaped mesh cell.

The suppression of crack opening is explained by the following.

The opening of crack 1 (Fig. 1, 2) is determined by stresses acting in the direction perpendicular to its length, and is restrained by rigidly elastic couplers 3 (Fig. 1-3), the deformation of which occurs according to Hooke's law. Since the deformation of the rock mass 6 (Fig. 1, 2) will not exceed the deformation of the mesh structure of the proposed mine support, consisting of rigid-elastic ties 3 and rod steel anchor elements 2, the possibility of crack development 1 is reduced.

The potential energy of crack opening 1 in fractured rock 6 is calculated using the Griffiths formula (see, for example, Kochetov V.T. Strength of materials. - Rostov University Publishing House, 1987, p. 330, file 19.3.10):

Where - rock stress in a crack on the roof of a mine opening, MPa;

true specific surface energy of rock, DYN;

modulus of elasticity of rock, MPa;

maximum design crack length, mm.

Therefore, the completed mine support increases the potential energy of crack opening by n times.

Where - stress in a rigid-elastic screed, MPa;

- rock stress, MPa;

- modulus of elasticity of steel, MPa;

- modulus of elasticity of rock, MPa.

With a rock of medium strength selected as a model, having a deformation modulus, on average, (for example, dolomites, I.V. Baklashov, B.A. Kartozia “Mechanics of underground structures and support structures.” Moscow. “Nedra.” 1984, p. 17, table 22) level of potential energy required to open a crack , will increase according to formula (2), which will prevent the destruction of the arch 5 (Fig. 1, 2) of the mine workings 7 (Fig. 2) of the fractured rock 6 (Fig. 1, 2).

An example of a method for strengthening rock with mine support.

The proposed method of strengthening rock with mine support was used to prevent the opening of cracks 1 (Fig. 1, 2) on the arch 5 (Fig. 1, 2) of mine workings 7 (Fig. 2) in the conditions of the Sibay underground mine.

On the roof 5 (Fig. 1, 2) of the mine working 7 (Fig. 2) near the visually detected crack 1 (Fig. 1, 2) holes were drilled - holes with a diameter of 43 mm and a length equal to 2050 mm (Fig. 1, 2) of industrial installation of Boomer 282 . The holes were drilled perpendicular to the location of crack 1, placed in pairs on both sides of it and at a distance of 1000 mm from each other (Fig. 1, 2), taking into account the direction of its opening. The drill holes were placed in the corners of an imaginary grid with a square cell with a side size of 1000 mm. Using Boomer 282, rod steel anchor elements 2 made of steel grade St 3 were installed into the holes until they stop in the perforated heads 8 (Fig. 3), made in the form of a disk-shaped plate with a diameter of 200 mm and a thickness of 10 mm (Fig. 1-3) with a cross-sectional diameter of 46 mm and a length of 2000 mm. In this case, the heads 8 were perforated with six holes with a diameter of 15 mm. The latter are made along the perimeter of the head 8 with a distance from the edge of the disk-shaped plate to the center of the hole - 27.5 mm.

Loop-shaped ends 10 (Fig. 3) of rigid-elastic couplers 3, which were closed into a loop by welding, are inserted into the holes of the heads 8. In this case, the length and cross-sectional diameter of the rigid-elastic couplers 3 (Figs. 1-3) are equal to 500 mm and 12 mm, respectively.

Then the opposing rigid-elastic ties 3 (Fig. 1-3), hingedly fixed in the holes of the heads 8 (Fig. 3), were pulled in the direction of nearby steel rod anchor elements 2 (Fig. 1-3). Each rigid-elastic tie 3 (Fig. 1-3) was connected end to end with a rigid-elastic tie 3 located on the other side of the crack 1 (Fig. 1, 2) of another structural element of the mine support. The connection of the above rigid-elastic couplers is carried out by means of a coupling nut 4 (Fig. 1, 2) 100-120 mm long, which, by selection, is installed in the space between the ends of the threaded sections 9 (Fig. 3) of the rigid-elastic couplers 3, and then - winds up.

In this case, the threaded sections 9 of the articulated rigid-elastic couplers 3 and the coupling nut 4 are made with left and right threads. When the coupling nut 4 is simultaneously screwed onto the threaded sections 9 of the articulated rigid-elastic ties 3, the latter are tightened.

To prevent the appearance of new cracks 1 (Fig. 1, 2), the mesh design of the proposed mine support with a triangular and diamond-shaped mesh cell was also used. In this case, structural elements were used with disk-shaped steel heads 8 (Fig. 3), perforated with six holes, to which six rigid-elastic couplers 3 were hingedly attached by loop-shaped sections 10 (Fig. 3).

To determine the effect of using the features of the proposed method, comparative tests were carried out.

Tests of the proposed anchor-mesh reinforcement were carried out in the conditions of the Sibay underground mine. Mine support was installed in four areas with an area of 50, 100, 150, 200 sq. m. Sections of a similar area without reinforcement alternated with reinforced sections, which ensured comparability of test results. The duration of the tests was 90 days. The results of comparative tests are presented in Table 1.

As can be seen from the table, the number of rock cracks that appeared on the roof of the mine opening in the area without reinforcement and in the reinforced area was the same. However, the reduction in the number of fractures of fractured mine rock depending on the area of the experimental site decreased significantly (see table).

Thus, the inventive method of rock using mine support makes it possible to strengthen fractured rock, preventing its destruction, including the arch, by preventing intensive (brittle) crack opening.

Table 1 Comparative test results of mine support Area of experimental plots, sq. m Quantity
detected cracks Number of collapses and rock separations along cracks On a site without reinforcement On a site reinforced with mine support on a site without reinforcement on a reinforced area 50 3 3 2 not found 100 5 5 5 1 150 7 7 6 2 200 10 10 7 2

Claims (1)

A method of strengthening rock with mine support, including placing steel anchor elements with heads in the rock, characterized in that at least two rod steel anchor elements are placed perpendicular to the direction of crack opening on both sides of it, the anchor elements are tightened with rigid-elastic ties, thus forming a cellular structure with an arbitrary shape of cells, and one end of each of the ties is hinged in the head, and the other end is connected end to end with a coupling nut-coupling with an adjacent tie, while at the free ends of the ties there are threaded sections equipped on one the tie with a left-hand thread, and on the opposite tie with a right-hand thread, and the coupling nut is made from one end with a left-hand thread, and from the other end - with a right-hand thread.