RU2160837C2 - Method of mine working bolting - Google Patents

Abstract

FIELD: mining; applicable in supporting of mine workings undergoing effect of dynamic loads. SUBSTANCE: method includes drilling of holes over supported contour of driven working to depth behind boundary of contour of region of rock inelastic deformations round working under effect of dynamic and static loads; securing of bolts with cementing material over entire length of holes behind the boundary of region of rock inelastic deformations with force counterbalancing the dynamic loads in region of rock inelastic and elastic deformations and static loads. Bolts are located over working supported contour at angle of 40 to 70 deg to it, and length of securing of bolts behind the contour of inelastic deformations of rocks is determined by formula given in the invention description. EFFECT: reduced expenditures for supporting of working undergoing effect of dynamic loads, and higher stability of supported workings. 3 cl

Description

 The invention relates to mining, and in particular to methods of fastening mine workings with anchor support, which are exposed to dynamic loads.

 The main sources of dynamic loads on the workings and supports are mass explosions during the extraction of minerals (iron and lead ores, other minerals), rock blows, sudden emissions of minerals containing rocks and gases enclosed in them, and others.

 Under the action of dynamic loads, the partial or complete destruction of the known frame, monolithic concrete, continuous precast reinforced concrete and anchor supports usually occurs. The accumulated experience shows that in ore and coal mines, in conditions of mass industrial explosions of explosives, during rock blows, sudden emissions and other dynamic phenomena in rock masses, tens of kilometers of mine workings fixed by well-known traditional supports are completely or partially violated. The recovery time of disturbed workings is sometimes up to 10-14 months, the material costs of restoration work are very high.

 Known methods for increasing the stability of the ore mass as.with. USSR N 1211119814, class E 21 D 20/00, N 1617149, cl. E 21 D 20/00, N 1739044, CL E 21 D 20/00, the essence of which is to drill from the worked out space into the ore mass of wells, install anchors in them, excavate previously anchored ore strata with tapes and horizontal layers in an ascending order under the protection of installed anchors. In these methods, the issues of securing the workings with anchor supports under the influence of significant dynamic loads are not resolved. They provide the mining of ore deposits in ascending order, and not the fastening of workings with complex geodynamic impacts during the sinking and operation.

 There is a method of leading anchor when sinking workings on a. with. USSR N1765441 A1, cl. E 21 D 20/00, according to which, when driving openings, inclined leading holes are drilled in the direction of the development, at the end of the inclined part of each hole, a curved section is drilled and then a section perpendicular to the longitudinal axis of the development. The inclined part of each borehole is drilled inside the excavation circuit to a depth equal to the length of the drill, while a number of additional perpendicularly directed sections are drilled from the inclined part with an interval along its length, and the free part is used after the installation of anchors for explosive breaking of the rock.

 The disadvantage of this method is the lack of a solution for the formation with the help of anchors of the rock mass around the mine, capable of absorbing dynamic loads without manifesting dangerous deformations and loss of stability arising from the development of a mineral. In addition, the method is very time-consuming due to the need to drill holes for mounting anchors in an arcuate manner, moreover, from the inclined part of the holes, the vertical part of the holes, into which flexible anchors (cable, wire) are installed and, if necessary, are monolified with a hardening mixture. Monolithic anchors in holes can be made only after the excavation of the rock of the next entry.

 Known methods for predicting and combating the dynamic manifestations of rock pressure in the preparatory and treatment workings with rock bursts, sudden emissions of rocks and gases in mines and coal mines as USSR N 752040, class E 21 D 20/00, N 987114, cl. E 21 D 20/00, N 1408085, class E 21 D 20/00, N 1523682, cl. E 21 D 20/00, N 1546663, cl. E 21 D 20/00, N 1546645, cl. E 21 D 20/00, N 1719656, CL E 21 D 20/00, N 2000440, cl. E 21 D 20/00. They consider technical solutions for unloading the array: by arranging unloading slots along the output and transfer circuit with their help increased stresses into the interior of the array beyond the reference pressure zone; by destroying the contour rocks by the blasting method and forming a zone of plastic deformations around the workings; by accelerating the process of reducing stresses in the surrounding rocks by vibration action on them (A.S. N 2000440). By a. with. N 1408085 stress reduction in shock hazardous massifs of rocks is achieved by the installation of compensation cavities with filling material, and compensation cavities form the length of the zone of maximum supporting loads.

 In all these methods, the issues of securing mine workings under the influence of dynamic loads have not been resolved.

где l_n - длина узла податливости анкера, м;
r₀ - половина ширины выработки, м;
r₁ - расстояние от оси выработки до границы зоны неупругих деформаций пород, м;
|U_n|- предельное удлинение анкерного стержня, мм;
U₀ - смещение контура выработки с учетом отпора анкера, мм;
φ- угол внутреннего трения массива горных пород, град.;
β- параметр, характеризующий степень увеличения максимального главного напряжения с увеличением минимального главного напряжения.A known method of installing a malleable anchor according to A.S. USSR N 1472687 A1, cl. E 21 D 20/00, namely, that they drill a well (hole) and fix the anchor in it with the main lock at the bottom of the well and additionally rigidly fix it in the well with a lock at a distance from the output circuit equal to the length of the compliance node, while the latter is determined by the formula

where l _n is the length of the compliance node of the anchor, m;
r ₀ - half the width of the output, m;
r ₁ is the distance from the axis of the excavation to the boundary of the zone of inelastic deformation of the rocks, m;
| U _n | - ultimate elongation of the anchor rod, mm;
U ₀ - displacement of the output circuit, taking into account the resistance of the anchor, mm;
φ is the angle of internal friction of the rock mass, deg .;
β is a parameter characterizing the degree of increase in the maximum principal stress with an increase in the minimum principal stress.

 The disadvantage of this method is that it is intended for fastening the workings with anchor support, in which the displacements of the surrounding rocks and the formation of the load on the anchors occur in a static mode, and not dynamic, as in mass explosions, rock blows and other geodynamic processes that have almost instantaneous force effects on host rocks and lining. Under the action of dynamic loads, the zone of inelastic deformation of the rocks around the workings in its size and condition is very significantly different from the zone of inelastic deformation of the host rocks under the influence of static loads on them. The disadvantage of this method is the need to secure the anchor in the well with an additional lock at a distance from the output circuit equal to the length of the ductility unit, and the ductility unit of a rather complex structure, including a cup, the inner space of which is filled with a viscous fluid. In addition, to determine the length of the compliance node, it is necessary to know 6 significantly different parameters - the rock mass, the lining itself, the excavation and the mechanical processes occurring in the host rocks (the displacement of the excavation contour, taking into account the anchor resistance, etc.). The presence of the compliance node and the need to determine 6 parameters to determine its length determine the increased complexity of installing anchors in the excavation.

 The closest technical solution to the claimed invention is a method of attaching mine workings with reinforced concrete anchor support (Shirokov A.P. Theory and practice of using anchor support. - M .: Nedra, 1981, pp. 44-50 and P. 221-226). The essence of the method lies in the fact that as mining is carried out in the fixed roof and sides of the mine, wells are drilled, anchors are installed in the wells and fixed with cementing material along the entire length of the wells.

 The disadvantage of this method is that it is intended for fastening workings in which the formation of the load on the anchors occurs in a static mode or static with some dynamic forces caused by the workings using a drilling and blasting method while simultaneously blasting a small amount of explosives, and not in a dynamic mode, as during mass industrial explosions, rock strikes, sudden emissions and other geodynamic processes that have almost instantaneous force effects on the VM surrounding rock and lining. Under conditions of increased dynamic loads, the zone of dangerous inelastic deformations of the rocks around the workings in its size and condition differs very significantly from the zone of dangerous inelastic deformations of the enclosing rocks under the conditions of action of only static loads on them.

 In openings in ore mines that are not affected by dynamic loads, the area of inelastic deformations, delamination and separation of the roof rocks of the overlying strata usually does not exceed 1-1.5 m and they are fixed mainly with reinforced concrete and other anchors 1.5-1.8 m.

 In this way, the anchoring cannot be ensured stability of mine workings experiencing the effects of dynamic loads.

 The objective of the invention is to reduce the cost of fastening and maintaining workings experiencing the effects of dynamic loads, and increase their stability.

где l_y - длина закрепления анкера за контуром области неупругих деформаций пород, м;
P_{дин.неупр} - динамические нагрузки, действующие на анкера в области неупругих деформаций пород вокруг выработки, кН;
P_{дин.упр} - динамические нагрузки, действующие на анкера в области упругих деформаций пород вокруг выработки, кН;
P_ст - статические нагрузки на анкер в области неупругих деформаций пород вокруг выработки, кН;
d_скв - диаметр скважины под анкер, м;
C - сцепление цементирующего материала со стенками скважины, кПа.The solution to the problem is achieved by the fact that in the proposed method, including drilling wells, installing anchors in them, fixing them with cementing material along the entire length of the wells, the anchors are fixed outside the boundary of the region of inelastic deformation of the rocks with a force that balances the dynamic loads in the field of elastic and inelastic deformations and static loads, while the anchoring length of the anchors for the inelastic deformation of the rocks is determined by the formula

where l _y is the anchor fixing length over the contour of the inelastic rock deformation region, m;
P _din.neupr - dynamic loads acting on the anchor in the field of inelastic deformation of the rocks around the mine, kN;
P _din . _Elastic - dynamic loads acting on the anchor in the field of elastic deformation of the rocks around the mine, kN;
P _article - static load on the anchor in the field of inelastic deformation of the rocks around the mine, kN;
d _SLE - well diameter under the anchor, m;
C is the adhesion of the cementing material to the walls of the well, kPa.

Anchors are placed at an angle of 40 - 70 ^o to the fixed output circuit.

 The proposed method provides, in comparison with the prototype, the joint work of rocks in the field of inelastic and elastic deformations of rocks around the production in a single mode of balancing dynamic loads in the field of elastic deformations and dynamic and static loads in the field of inelastic deformations arising and acting in these areas, without the manifestation of dangerous deformations and the destruction of the rocks of the region of inelastic deformations around the mine and the loss of its stability.

 In the claimed method, in comparison with the prototype, the movement of destructive dynamic and static loads from the region of dangerous inelastic deformations of the rocks around the mine to the depth of the array to the region of its elastic deformations is achieved, i.e. clearly safe, by the amount at which the distributed and acting loads (forces) in both areas of the massif do not cause dangerous deformation of the rocks and violations of the support and stability of the mine.

 The proposed method provides control of dynamic loads on the rocks around the workings arising from mining and construction operations, in which they do not cause dangerous deformation of the rocks and lining and provide a stable state of the workings.

An essential distinguishing feature of the proposed method from the prototype is also the placement of anchors along the fixed working contour at an angle of 40 - 70 ^o to it, at which, as shown by special laboratory studies on models of equivalent materials, they perceive dynamic tensile and shear loads not exceeding the strength of the rocks in the field of inelastic deformations. This order of placement of anchors along the fixed working contour provides reflection, dispersion and perception by the anchors of longitudinal and transverse waves, which usually cause the most severe deformations of rocks in the near-edge area of the mine. According to laboratory tests, the installation of anchors at angles of 40 - 70 ^o to the fixed output circuit provides an increase in their perception of the dynamic load by 1.4 - 1.6 times compared with anchors installed along the normal to the circuit, i.e. at an angle of 90 ^o .

 The analysis of the prior art by the applicant, including a search by patent and scientific and technical sources of information, and the identification of sources containing information about analogues of the claimed invention, allowed to establish that the applicant did not find a source characterized by features that are identical (identical) to all the essential features of the claimed invention.

 Therefore, the claimed invention meets the condition of "novelty."

 In FIG. 1 shows a cross-section of a mine secured with a deep anchor support; in FIG. 2 - node A of FIG. 1; in FIG. 3 is a diagram of the loading of anchors with static and dynamic load components.

 The method is as follows.

As the mine 1 is being drilled, boreholes (holes) 2 for anchors 3 are drawn in a fan pattern along the mine circuit at an angle of 40-70 ^° to the fixed mine circuit. Wells are drilled with their deepening into the region of 4 elastic deformations of rocks under the influence of dynamic loads arising in the host rocks during mining and treatment works for the mine working life. The depth (l _y ) of the wells 5 and anchors in the region of elastic deformation of the rocks beyond the contour 6 of the region of inelastic deformation of the rocks 7 under the influence of dynamic and static loads in it is determined by the above formula (1). Anchors 3 are installed in the drilled wells 2 as they are being drilled and fixed in the buried part of the wells 5 in the region 4 of elastic deformations of the rocks with a force (strength) P _z.a. balancing dynamic and static loads arising and acting in the rocks around the mine during its service life, i.e. fasten them with durability
P _z.a. ≥ P _dyn. + P _dyn . _Inoperative + P _st , (2)
where P _z.a. - the strength of the anchor in the field of elastic deformation of the rocks, kN;
P _din. and P _din . _inel - dynamic loads acting on the anchor in the region of respectively elastic and inelastic deformations of rocks, kN;
P _Art - static loads on the anchor in the field of inelastic deformation of rocks, kN.

 After fixing the anchor in the buried part of the well with cementing material, for example, quick-hardening cement mortar, the well is filled along the entire length with the same material 8. On the production circuit, the anchors are connected together by metal ties 9 in the transverse and longitudinal directions of the production to increase the efficiency of their joint operation.

The length of the anchor l _a is determined by the formula
l _a = l _{failure Y} + l + l _{in the} (3)
where l _failure - the value (power) of the region of inelastic deformations of rocks formed under the action of dynamic and static loads, m;
l _y - the depth of the anchor in the region of elastic deformation beyond the contour of the region of inelastic deformation of the rocks, m;
l _in - the length of the protruding part of the anchor protruding inward, m

 The dynamic forces (loads) arising in the rocks around the mine workings during mass industrial explosions, rock blows, sudden surges and other dynamic phenomena are determined by known methods for calculating dynamic stresses in rock masses. Known calculation methods determine the static load on the anchor support of underground mining.

 Dynamic and static loads on the anchor support can also be determined directly in the mine workings during their operation using well-known force measuring devices, for example, mechanical, electrical, hydraulic and other dynamometers with recording readings directly at the installation site or remotely.

 The dimensions of the region 7 of inelastic deformations of the rocks, the boundary 6 between region 7 of inelastic deformations and the region of 4 elastic deformations of the rocks around the mine is determined previously when developing adjacent reserves, pillars with almost the same conditions, by known methods, for example, using depth benchmarks laid in boreholes drilled to various depths from the output contour, or using geophysical (mainly acoustic) logging. Elastic and inelastic deformation parameters of the fixed rocks in the dynamic loading mode, i.e. under the influence of dynamic forces, can be determined by known methods directly in the array (for example, by unloading the array, by pressing punches into the walls of the wells) or by laboratory testing of samples taken from wells drilled from a well in surrounding rocks before and after dynamic impact on them loads specific to specific conditions.

 An example of the method with the determination by calculation of the length of the anchors, fixing the contour of a mine working exposed to dynamic loads.

 Initial data.

The cross-sectional area of the mine in the sinking is 16 m ² , the width of the mine is 5.5 m; compressive strength of host rocks σ _sr = 40 MPa (400 kgf / cm ² ); rock strength coefficient on the prof. M.M. Protodyakonova f = 4, bulk density of rocks γ = 0.025 MN / m ³ (2500 kgf / m ³ ); the coefficient of structural-textural weakening of rocks k _c = 0.5 (the distance between the surfaces of weakening of rocks 0.5-0.6 m); steel anchors with a diameter of 22 mm, the elastic modulus of the steel from which the anchors E _a = 2 • 10 ⁵ MPa are made; borehole diameter for anchors d _ck = 43 mm; the distance between the anchors in the row a = 1 m, the distance between the rows of anchors along the length of the excavation l = 1 m; anchors in the wells (the length of their part l _у fixed to the contour of the region of inelastic deformation of the rocks) is fixed with a cementing material (for example, concrete) with a specific resistance to their shift relative to the walls of the well C = 1 MPa (10 kgf / cm ² = 10 • 10 ⁴ kgf / m ² = 1000 kPa).

According to a number of tests for concrete C = 1 - 1.2 MPa:
1. Determine the load on the anchor from the side of the roof during the operation of the lining in the static load mode from the expression
P _k = Sh γ = 1 • 1.4 • 2500 = 3500 kgf = 35 kN, (1)
where S = al = 1 • 1 = 1 m ² is the area supported by the anchor; γ = 2500 kgf / m ³ - volumetric weight of the rocks; h - the height of dangerous deformations and possible collapse of the roof rocks, m

где b = 5,5 м - ширина выработки в проходке; f = 4 - коэффициент крепости пород; k_c = 0,5 - коэффициент структурно-текстурного ослабления пород.According to the theory of M.M. Protodyakonov, taking into account the coefficient of structural and textural weakening of rocks k _c = 0,5 height h is determined by the formula

where b = 5.5 m - the width of the excavation in the sinking; f = 4 - rock strength coefficient; k _c = 0.5 is the coefficient of structural and textural attenuation of rocks.

2. Determine the length of the anchor during the operation of the lining in a static load mode
l _a = l _z + h + l _s = 0.4 + 1.4 + 0.2 = 2 m, (3)
where l _z = 0.4 m is the length of the castle part of the anchor, deepened beyond the contour of a possible collapse h (according to many years of practice, l _z = 0.3-0.4 m); l _s = 0.2 m - the length of the part of the anchor protruding into the mine (connecting anchors to each other with a grab).

(4)
(динамическую нагрузку определяют из выражения

где C₀ - жесткость анкерного стержня (рекомендуется определять экспериментально). По данным выполненных лабораторных испытаний для анкеров длиной более 3-3,5 м с учетом неоднородности материала рекомендуется принимать C₀ = 500 кгс/м = 5 кН/м; V_неупр. - скорость продольной волны в опасно деформированной неупругой области, по результатам лабораторных и шахтных испытаний ряда авторов V_неупр. = 200 - 300 м/с в зависимости от степени ослабления и разрушения пород, принимаем V_неупр. = 300 м/с; f_а - частота колебаний анкерного стержня, с^-1

где T - период сейсмических колебаний пород (длительность действия максимальных нагрузок на крепь). По данным инженерно-сейсмической службы T = 0,03-02 с^-1. Принимаем T = 0,05 с^-1.3. According to the theory of mechanical vibrational movements, the maximum load on the anchor P ₀ , due to the action of a static load P _st and dynamic load in the field of inelastic deformations of the roof rocks P _dyn . _Inel , is determined by the formula

(4)
(dynamic load is determined from the expression

where C ₀ is the stiffness of the anchor rod (it is recommended to determine experimentally). According to laboratory tests for anchors longer than 3-3.5 m, taking into account the heterogeneity of the material, it is recommended to take C ₀ = 500 kgf / m = 5 kN / m; V _fault - the longitudinal wave velocity in a dangerously deformed inelastic region, according to the results of laboratory and mine tests of a number of authors V _inel. = 200 - 300 m / s, depending on the degree of weakening and destruction of the rocks, we accept V _failure. = 300 m / s; f _a - vibration frequency of the anchor rod, s ^-1

where T is the period of seismic vibrations of the rocks (the duration of the maximum loads on the lining). According to the engineering-seismic service, T = 0.03-02 s ^-1 . We take T = 0.05 s ^-1 .

(динамическая нагрузка на анкер в области упругих деформаций пород
определена из выражения

В формуле (6) C₀ = 500 кгс/м - жесткость анкерного стержня; V_y - скорость распространения продольной волны в области упругих деформаций пород. В породах с коэффициентом структурно-текстурного ослабления пород k_c = 0,5 по данным значительного объема шахтных исследований V_у = 2300-2600 м/с. Принимаем V_y = 2500 м/с; f_n - частота собственных колебаний заанкерованной кровли, с^-1; по данным шахтных наблюдений и замеров f_n = (2,5 - 3)f_а. Принимаем f_n = 2,5 f_a = 2,5•20 = 50 с^-1.4. The maximum load on the anchor, taking into account the static load P _st , dynamic load P _dyn . _Inel in the field of inelastic deformation and dynamic load P _dyn. in the field of elastic deformations of rocks is determined by the formula

(dynamic load on the anchor in the field of elastic deformation of rocks
defined from expression

In the formula (6) C ₀ = 500 kgf / m is the rigidity of the anchor rod; V _y is the propagation velocity of a longitudinal wave in the region of elastic deformations of rocks. In rocks with a coefficient of structural-textural weakening of rocks k _c = 0.5 according to a significant amount of mine research V _y = 2300-2600 m / s. We accept V _y = 2500 m / s; f _n is the frequency of natural vibrations of the anchored roof, s ^-1 ; according to mine observations and measurements f _n = (2.5 - 3) f _a . We take f _n = 2.5 f _a = 2.5 • 20 = 50 s ^-1 .

Reliable fixing of the anchor in the field of inelastic deformation of rocks is provided provided
P _for > P _st + P _dyn . _Inop + P _dyn. , (7)
those. with P _for > 3500 + 3750 + 4595.6 = 11845.6 kgf or P _for > 118.456 kN.

The length of the anchor for attaching workings exposed to dynamic loads l _a is determined from the expression
l _a = l _{failure Y} + l + l _in = h _v + h _din.neupr + l + l _{y a,} (8)
where l _failure = h _st + h _{dyn. inel} - the value (power) of the region of inelastic deformations under the action of a static load P _st (h _st ) and dynamic load P _dyn . _inel (h _{dyn. inel} ), m; l _y - the depth of the anchor in the region of elastic deformation beyond the contour of the region of inelastic deformation of the rocks, m; l _in - the length of the protruding part of the anchor protruding inward, m

The value of h _article = 1.4 [from the expression (2)].

The value of h _din.indust is determined by the formula
P _dyn . _Iner = S γ h _{dyn. Iner} , (9)
where P _dyn . _inop = 3750 kgf [from the formula (4)], S = al = 1 • 1 = 1 m ² - the area supported by one anchor (from the passport of the mine working); γ = 2500 kgf / m ³ - volumetric weight of the fixed rocks (the initial indicator of the conditions for fixing the mine).

Величину l_у определяют по формуле

Необходимая длина анкера для крепления выработки по формуле (8)
l_a = h_ст + h_{дин.неупр} + l_у + l_в = 1,4 + 1,5 + 0,88 + 0,2 = 3,98 м ≈ 4 м.From formula (9) we find

The value of l _y is determined by the formula

The required length of the anchor for fixing the workings according to the formula (8)
l _a = h _st + h _{dyn. inoperative} + l _у + l _в = 1.4 + 1.5 + 0.88 + 0.2 = 3.98 m ≈ 4 m.

 The advantage of the proposed method for securing mine workings under dynamic loads is that it ensures the joint work of the rocks of the elastic strain region, i.e. areas that under the influence of dynamic loads do not undergo any dangerous deformations, and areas of inelastic, usually dangerous deformations in a single balanced power mode without manifesting dangerous deformations of the rocks around the mine and maintaining it in a stable normal operational condition. This method allows you to drastically increase stability and reduce the cost of securing and maintaining underground mine workings subject to dynamic loads.

Claims (1)

A method of securing mine workings, including drilling wells, installing flexible anchors in them, fixing them with cementing material along the entire length of the wells, characterized in that the anchors fix the boundary of the region of inelastic rock deformations with a force that balances the dynamic loads in the field of elastic and inelastic deformations and static loads, while the anchoring length of the anchors for the inelastic deformation of the rocks is determined by the formula
l _y = (P _{din. fault.} + P _{din. control} + P _st ) / π • d _well • C,
where l _y is the anchor fixing length over the contour of the inelastic rock deformation region, m;
R _{din. faulty} - dynamic loads acting on anchors in the field of inelastic deformations of rocks around a mine, kN;
R _{din. control} - dynamic loads acting on the anchors in the field of elastic deformation of the rocks around the mine, kN;
P _article - static load on the anchor in the field of inelastic deformation of the rocks around the mine, kN;
d _SLE - well diameter under the anchor, m;
C - adhesion of the cementing material with the walls of the well, kPa,
moreover, the anchors are placed at an angle of 40 - 70 ^o to the fixed output circuit.

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