SU1689637A1 - Method for constructing mining working - Google Patents

Abstract

The invention relates to underground construction and allows to increase the efficiency of work in weak rocks when tensile stresses develop in the roof. To do this, use a preliminary force on the rock mass, redistribute the natural field of stresses and create an area of increased compressive stresses ahead of the bottom. The compressive strength and bulk density of rocks are determined. From the bottomline along the longitudinal axis of the excavation on its vertical axis of symmetry, a slot with a height of more than 0.27 and less than 0.54 of the radius of generation is arranged. Its lower end is located below the design contour of the arch at a distance of not less than 0.13 of the radius of generation. The gap is sealed and the pressure of the hardening solution is created in it, which is determined from the analytical expression. After the redistribution of stresses, the output section is opened in front of the slab. The strain modulus and Poisson's ratio of the rocks are determined and a hardening solution is used with similar deformation characteristics. 1 h. item f-ly, 2 ill. cl

Description

The invention relates to underground construction, in particular, to methods of penetrating and securing mine workings in weak rocks under the conditions of prevailing vertical pressure and formation in the roof of the mine working after opening its cross section of tensile stresses causing ejection.

The purpose of the invention is to increase the efficiency of work.

FIG. 1 shows the production, cross-section; in fig. 2 - the same, longitudinal section.

With the prevailing vertical pressure, i.e., with a lateral pressure ratio of less than 1/3, which is most characteristic of shallow laying, when opening the cross sections of the latter in their arch, a zone of tensile stresses is formed. The dimensions of this zone depend on the magnitude of the lateral pressure ratio, and as it decreases, the zone increases. The action of tensile stresses in the roof of the excavation, passed in weak rocks, leads to the destruction of the latter and subsequent development, since the limit of their tensile strength is extremely insignificant and, as a rule, is equal to zero.

In this situation, it is advisable to arrange an advance gap ahead ahead of opening the production section and, by creating a certain pressure P in it, create an increased field of compressive stresses in the rock mass. This leads to the fact that after the opening of the production section as a result of the overlapping fields

about

00

yoo o

Gj vj

opposite in sign stresses around the working, a field of compressive stresses is established, which prevents the formation of a strain.

The most dangerous are tangential tensile stresses, whose distribution zone and magnitude exceed similar characteristics of radial stresses. They are the ones responsible for the collapse of the roof rocks. The boundary of the zone of tensile stresses in the roof of the mine is determined from the expression

6H -) - L) so5 20

- (1 + / l) -V (1+ z-iZcosZe l (1- / Ja) cos20f where r, 0 - polar coordinates;

A is the lateral pressure ratio;

I - Poisson's ratio; R is the radius of development in the penetration. The angle of the semi-coverage zone of tensile stresses

& 11 + A

  2GSS052 (1-A).

Then the lower boundary of the tensile stresses zone is from the shelesh of the production contour at a distance determined from the expression

And R (1 - cos 0).

The most unfavorable from the point of view of increasing the size of the stretching zones in the roof of the production case occurs when the lateral pressure coefficient A 0, i.e., in the absence of lateral load.

In this case, the height of the stretch zone along the vertical axis of symmetry of generation

Ј max 0.73-K;

, 13-r.

The expression for determining the concentration of stresses around the slit (4) has the form

g + h2 / 4) 2-h2 / 4l3 eLx-bVx2 + h2 / 42-h2 / 4 iJ

7,

where P is the pressure created in the gap;

h - the height of the slit.

To ensure sustainability, there is no need to compensate for the entire tensile stress zone. It is enough to eliminate their negative influence in the immediate vicinity of the production contour.

The compressive stresses arising around the gap during the creation of pressure in it reach the highest value at the level of its midpoint. In this connection, it is advisable to locate the center of the gap in the most dangerous direction, i.e. at the level of the roof slag. At the same time, to guarantee compensation of tensile stresses under this line, the lower end of the slit

should be located below the boundary of the tensile stresses on the production contour. Based on these two considerations, it is possible to establish the smallest slot height, which is equal to twice the distance from the contour of the mine to the lower end of the slot, i.e. h 0.27-R.

In the process of numerical simulation on a computer with a correlation coefficient / 3

0.9999, the dependence of the required pressure in the advance slit on the height of the latter, under which it is guaranteed that there is no tensile stresses at the level of the roof of the arch within the limits of development and in close proximity

from its contour after opening the production section. It was also found that when the gap height is in the range of values of h (0.54-0.73), the required pressure does not exceed -H. Thus, in order to reduce the laboriousness of the work associated with the slit device, its maximum size should be h 0.54-R. However, at extremely small values of the gap height, the required pressure can reach significant values and exceed the compressive strength of rocks, which leads to their destruction, which cannot be allowed. Thus, the gap length and the pressure developed in it must be interconnected.

Bearing in mind that any inclusion in the rock mass is an additional stress concentrator, to smooth this non-volatile

It is advisable to use solutions to create pressure solutions that, after hardening, have deformation characteristics close to the corresponding properties of the rocks.

The method is implemented as follows. In the construction of the excavation 1 under the conditions of excavation, which takes place as a result of the action of tensile stresses 2 in its arch, a preliminary

force impact on the rock mass to redistribute the natural field stress and create 3 areas of increased compressive stress in front of the wall.

Tunneling work is carried out in separate entries. At the beginning of each entry, work on the opening of the section of production 1 is temporarily suspended and ahead of the hole is determined

compression and their volumetric weight. Then from the bottom 3 along the longitudinal axis of the excavation 1 arrange a vertical slit 4, which is placed on the axis of symmetry. For this purpose, split wells can be used, hydraulic fracturing or washing out, bar cutting, etc.

Preliminary from the set range

0,, 54R, where R is the radius of development, m. Choose the height h of the slit 4 and according to the expression

Р 0,297 - у H (h / R) 94h / R, where у is the bulk density of rocks, MN / m3;

H is the depth of the laying of the excavation, m, the necessary pressure P is determined, which must be created in it to compensate for tensile stresses 2 arising in the roof of the excavation 1 nqp / i. If the pressure determined in such a way is greater than the compressive strength of the rocks, the height of the slot 4 should be increased and the calculations to determine the required pressure should be repeated. The slot 4 has its lower end positioned below the design contour of the production arch at a distance of at least D 0.13 -R. The center of the slit 4, it is advisable to have on the project contour output 1.

If output 1 is not circular, then the calculation uses the notion of equivalent radius, which is determined from the expression R 0.63VS, where S is the area of the output section in the penetration, m2.

After the device of the slit 4, work is done to seal its mouth and create a predetermined pressure in it. The force effect on the rock mass can be created either by forcing 4 hardening solutions 5 under high pressure into the advancing gap, or by filling it with solutions 5, which expand during hardening.

It is also advisable, during the establishment of the physicomechanical properties of the rocks, to additionally determine their strain modulus and the Poisson's ratio and to use hardening solutions 5 with deformation characteristics that closely approximate the corresponding properties of the rocks.

When conducting work in unstable rocks, it is advisable to erect a safety jumper (not shown) in the bottom hole 3 before the device of the slit 4. After hardening the solution 5 and redistributing the natural stress field around the leading gap 4, work on opening the production section 1 is resumed.

This approach is based on the principle of advanced roof stabilization. Compliance with the parameters of the method makes it possible to ensure the stability of the excavation, to exclude the use of temporary lining during its penetration, to facilitate the construction of permanent lining, and in certain cases to refuse it.

Claims (2)

1. A method of constructing a mine working, including determining the physicomechanical properties of rocks ahead of the mine, arranging a roof in the roof of its excavation on the vertical axis of symmetry of the leading slot with the lower end of the latter under the design output circuit, sealing the gap and creating a pressure of hardening mortar in it, opening production sections, characterized by the fact that, in order to increase the efficiency of work, they additionally determine the compressive strength of rocks, and arrange the slit with height 0, 0.54-R, at the same time, its lower end is located under the design contour of the excavation at a distance of not less than , 13-r, and the pressure in the gap is created not less than the value determined from the expression P 0,297-yH (h / Ry11 94h / R and not more than the compressive strength of rocks, where h is the gap height, m; А- distance from the design contour of the excavation to the lower end of the slot, m; P is the pressure created in the gap, MPa; R is the radius of development, m; y is the volume weight of rocks, MN / m; H - the depth of the laying of production, m 2. A method according to claim 1, characterized in that the deformation properties of the rocks are additionally determined and a hardening solution with deformation characteristics close to the rocks is used.  . G. ....  .. -. - - -. - C F (AG. 2 Editor O. Golovach Compiled by L. Berezkina Tehred M.MorgentalKorrektor T.Paly