MINE EXPLOITATION, SEPARATION, FILLING AND TREATMENT EXPLOITATION METHOD

Abstract

The present invention discloses a mine exploitation, separation, filling and treatment exploitation method, including main sources of gangue on a small-volume gangue exploitation working face and gangue reducing measures; system layout, equipment and separation technology for coal gangue separation; system layout, equipment and production technology for filling synergistic caving type coal efficient stoping; pretreatment and pre-control measures for environmental influence before and after gangue filling; and design principle and design steps of the mine “exploitation, separation, filling and treatment” exploitation method. The method not only solves the problem of long-distance transportation of gangue, reduces the lifting cost of underground gangue and relieves the pressure of mine auxiliary lifting and ground coal washing plants, but also may effectively treat coal mine gangue, reduce the surface stacking area of coal gangue, reduce the damage to the ecological environment of a mine and protect an ecological environment. Furthermore, a gangue filling and coal efficient stope face has high single production efficiency, may meet the requirements of modern mines for production capacity, and application prospects are wide.

Description

FIELD OF THE INVENTION

The present invention relates to a mine exploitation design method, particularly relates to a mine exploitation, separation, filling and treatment exploitation method, and belongs to the technical field of coal mine exploitation.

DESCRIPTION OF RELATED ART

With the large scale of mines and the modernization of coal mine exploitation technologies, especially the widespread application of a top coal exploitation technology and an exploitation technology of a large number of thin coal seams, top and bottom plates of a coal seam of a working face are doped with a large number of gangue, so that the volume of the gangue mixed in raw coal is increased. In the traditional coal mine exploitation, the coal gangue in the exploited raw coal is not separated in an underground space, the exploited raw coal directly enters a coal bin at a bottom of a shaft and is lifted out of the mine by a lifting system, then, the gangue in the raw coal is discharged, and the discharged gangue requires a special stacking site. Because the raw coal is washed and separated after being conveyed from the underground space to the ground, gangue transportation energy is wasted, the separated gangue is prone to spontaneous combustion during stacking, a lot of land is occupied, an ecological environment is seriously polluted, and the mine environment becomes increasingly serious. Furthermore, gangue conveying and lifting systems in an underground coal flow system belong to invalid transportation of the mine, and the invalid transportation volume will greatly reduce the actual production capacity of the mine and increase the equipment cost.

SUMMARY OF THE INVENTION

In order to overcome various defects existing in the prior art, the present invention provides a mine exploitation, separation, filling and treatment exploitation method for relieving the pressure of mine auxiliary lifting and ground coal washing plants, and capable of effectively treating coal mine gangue, reducing the surface stacking area of coal gangue, protecting an ecological environment of a mine and increasing coal exploitation efficiency.

In order to solve the above problems, the mine exploitation, separation, filling and treatment exploitation method of the present invention includes the following steps:

step 1: determining main sources of gangue on a designed stope face according to a geological condition and an occurrence feature of a coal seam;

step 2: selecting a corresponding measure for reducing gangue content in coal exploitation according to the main sources of the gangue on the designed stope face, and arranging a small-volume gangue exploitation working face;

step 3: arranging an underground coal gangue separation system, performing equipment selection on the coal gangue separation system, and performing coal gangue separation on raw coal produced by the small-volume gangue exploitation working face;

step 4: conveying the separated gangue to an underground gangue bin by a gangue conveying belt, then, conveying the separated gangue to a gangue filling and coal efficient stope face from the underground gangue bin by the gangue conveying belt to perform filling treatment, and then, arranging a filling synergistic caving type fully mechanized coal face; and

step 5: according to the volume of the gangue separated by the coal gangue separation system, designing a length of a filling section of the filling synergistic caving type fully mechanized coal face, arranging a filling section stope face, and performing equipment selection and matching; according to a mine production capacity, designing a length of a caving section of the filling synergistic caving type fully mechanized coal face, arranging a caving section stope face, and performing equipment selection and matching; and arranging a transition section of the filling synergistic caving type fully mechanized coal face between the filling section and the caving section, arranging a transition section stope face, and performing equipment selection and matching.

Specifically, the main sources of the gangue in the step 1 include: gangue in a fully mechanized caving mining drawing technology, a dirt band in a coal seam, gangue caved from a working face stope roof, and gangue exploited by a coal face due to change in the geological condition.

Measures taken for reducing gangue content in coal exploitation according to different gangue sources are as follows:

a. for the gangue in the fully mechanized caving mining drawing technology, the gangue content in fully mechanized caving mining is reduced by firstly detecting top coal thickness distribution to grasp top coal thickness change and then changing a drawing interval and a drawing mode according to different top coal thicknesses;

b. for the dirt band in the coal seam, the gangue content of the coal seam with the dirt band is be reduced by a layer mining mode;

c. for the gangue caved from the working face stope roof, the gangue caved from the stope roof is reduced by timely support and increase of support strength;

d. for the gangue cut by a bottom plate of a fully mechanized coal face, the gangue cut by the bottom plate of the fully mechanized coal face is reduced by changing a height of a drum of a coal cutter and applying an anti-dumping measure for the coal cutter; and

e. for the gangue exploited by the coal face due to change in the geological condition, the gangue content is reduced by firstly detecting and analyzing the degree of change in the geological condition and then adopting measures of bypassing, working face moving and coal mining equipment parameter adjusting.

Further, the filling synergistic caving type fully mechanized coal face means that a comprehensive mechanized solid filling coal mining section and a traditional comprehensive mechanized coal mining section are simultaneously arranged on one working face, and a specific technology is as follows:

a. coal mining technology: three different types of supports are arranged on a working face of a gangue filling and coal efficient stope system, where the support arranged on the filling section is a filling coal mining hydraulic support, the support arranged on the transition section is a filling coal mining hydraulic support with a side guard plate, and the support arranged on the caving section is a traditional fully mechanized mining hydraulic support; the three supports are designed to have the same unit advance and share a coal cutter and a scraper conveyer, and coal at an exploitation site is conveyed by a belt conveyer; and

b. filling technology: underground washed gangue is conveyed from the gangue bin to a porous bottom-dump conveyer of the filling section of a mixed mining face through a feeder, a gangue transport rubber belt conveyer and a self-moving type transfer machine sequentially, and discharge holes suspended on the porous bottom-dump scraper conveyer at a rear part of the gangue filling section are opened according to a certain order to enable the gangue to naturally fall to a goaf.

Further, in the step 5, before filling of the filling synergistic caving type fully mechanized coal face, environmental disaster evaluation of the gangue is required, and if the gangue causes pollution to an underground environment, the separated gangue needs to be pretreated to reduce secondary pollution of the gangue. Specific measures include:

a. gangue soaking pretreatment: the separated gangue is soaked in water for pretreatment for several days, so that a reaction of heavy metal ions on a surface of the gangue tends to end; and

b. gangue microorganism modification: heavy metal reaction and migration on the surface of the gangue are inhibited by adopting a microorganism culture mode, thereby preventing secondary pollution to a groundwater environment and soil.

Further, in the step 5, after filling of the filling synergistic caving type fully mechanized coal face, a goaf is monitored in real time, and if heavy metal ions are precipitated, pre-control measures are required, specifically including:

a. paving of an anti-leakage layer on a bottom plate: a dense material is adopted to pave a floor to inhibit leakage of the heavy metal ions; and

b. grouting treatment on the bottom plate: a crack of the bottom plate is subjected to grouting treatment to inhibit infiltration of the heavy metal ions.

Preferably, a coal gangue separation method in the step 3 is an underground movable sieve jigging separation method which is specifically as follows:

underground coal gangue enters a sieving machine, slack coal of which the particle size is less than set particle size is conveyed to a coal bin directly through a slack coal conveying belt, raw coal of which the particle size is greater than the set particle size falls into a coal gangue separation, feeding and conveying belt machine through a raw coal chute, the raw coal with a large particle size is conveyed to a crushing machine by the coal gangue separation, feeding and conveying belt machine through a feeding chute so as to be crushed, and then, the crushed raw coal is conveyed to a movable sieve jigging separation machine to separate gangue from clean coal.

The underground movable sieve jigging separation method has the advantages of large separation size range, a small amount of water used by equipment, and a simple process system.

Further, a length of the transition section of the filling synergistic caving type fully mechanized coal face is generally equal to a length of 4 to 9 hydraulic supports.

In the present invention, the exploitation of the gangue is minimized by arranging the gangue small-scale exploitation system and optimizing process parameters according to different gangue sources, the raw coal exploited by the gangue small-scale exploitation system is separated by the underground coal gangue separation system, and the separated gangue is filled on the site. In order to synchronize the speeds of filling and caving, the filling synergistic caving type coal efficient stope face is arranged, so that the separated gangue may be completely filled; and furthermore, the raw coal exploited by fully mechanized mining is conveyed to the coal gangue separation system for separation, so that the two working faces may be propelled simultaneously. In order to prevent interference between the caving section and the filling section, the transition section is further arranged between the caving section and the filling section. In order to reduce the influence of the gangue on a filling region environment, pretreatment and pre-control measures for reducing the environmental influence are taken before and after the gangue filling step. The method not only solves the problem of long-distance transportation of gangue, reduces the lifting cost of underground gangue and relieves the pressure of mine auxiliary lifting and ground coal washing plants, but also effectively treat coal mine gangue, reduce the surface stacking area of coal gangue, reduce the damage to the ecological environment of the mine and protect the ecological environment. Furthermore, a gangue filling and coal efficient stope face has high single production efficiency, meets the requirements of modern mines for production capacity, and has wide application prospects.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a layout diagram of an underground system of the present invention;

FIG. 2 is a process flow diagram of an underground coal gangue separation movable sieve jigging method;

FIG. 3 is a layout diagram of a gangue filling and coal efficient stope face; and

FIG. 4 is a process flow diagram of a mine “exploitation, separation, filling and treatment” exploitation method.

In the drawings, 1. gangue small-scale exploitation system; 2. coal gangue separation system; 3. gangue filling and coal efficient stope system; 4. filling section; 5. transition section; 6. caving section; 7. filling coal mining hydraulic support; 8. filling coal mining hydraulic support with side guard plate; 9. traditional fully mechanized mining hydraulic support; 10. coal cutter; 11. scraper conveyer; 12. porous bottom-dump scraper conveyer; 13. discharge hole; 14. self-moving type transfer machine; 15. gangue belt conveyer; 16. rail lane; 17. conveying lane; and 18. belt conveyer.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will be described in detail below with reference to the drawings and specific embodiments.

FIG. 1 and FIG. 4 show a mine exploitation, separation, filling and treatment exploitation method. The method requires two systems arranged in an underground space, including a gangue small-scale exploitation system 1, a coal gangue separation system 2 and a gangue filling and coal efficient stope system 3. The working capability of each system should meet the following principle: the design filling capability of the gangue filling and coal efficient stope system>the gangue separation capability of the coal gangue separation system>the gangue discharge capability of the gangue small-scale exploitation system.

The specific steps are as follows:

step 1: determining main sources of gangue on a designed stope face according to a geological condition and an occurrence feature of a coal seam,

where the main sources of the gangue include: gangue in a fully mechanized caving mining drawing technology, a dirt bands in a coal seam, gangue caved from a working face stope roof, and gangue exploited by a coal face due to change in the geological condition;

step 2: selecting corresponding measures for reducing gangue content in coal exploitation according to the main sources of the gangue on the designed stope face, and arranging a small-volume gangue exploitation working face,

where the measures taken for reducing the gangue content in coal exploitation according to different gangue sources are as follows:

a. for the gangue in the fully mechanized caving mining drawing technology, the gangue content in fully mechanized caving mining is reduced by firstly detecting top coal thickness distribution to grasp top coal thickness change and then changing a drawing interval and a drawing mode according to different top coal thicknesses;

b. for the dirt band in the coal seam, the gangue content of the coal seam with the dirt band is reduced by a layer mining mode;

c. for the gangue caved from the working face stope roof, the gangue caved from the stope roof is reduced by timely support and increase of support strength;

d. for the gangue cut by a bottom plate of a fully mechanized coal face, the gangue cut by the bottom plate of the fully mechanized coal face is reduced by changing a height of a drum of a coal cutter and applying anti-dumping measures for the coal cutter; and

e. for the gangue exploited by the coal face due to change in the geological condition, the gangue content is reduced by firstly detecting and analyzing the degree of change in the geological condition and then adopting measures of bypassing, working face moving and coal mining equipment parameter adjusting;

step 3: arranging an underground coal gangue separation system 2, performing equipment selection on the coal gangue separation system, and performing coal gangue separation on raw coal produced by the small-volume gangue exploitation working face,

where as shown in FIG. 2, a coal gangue separation method adopted in the present embodiment is an underground movable sieve jigging separation method, coal gangue separation devices, such as a movable sieve jigging separation machine, a sieving machine and a crushing machine, are arranged near a shaft station of a coal mine or in the centralized transportation direction of the raw coal, and the specific method is as follows:

underground coal gangue enters a sieving machine, slack coal of which the particle size is less than 50 mm is conveyed to a coal bin directly through a slack coal conveying belt, raw coal of which the particle size is greater than 50 mm falls into a coal gangue separation, feeding and conveying belt machine through a raw coal chute, the raw coal with a large particle size is conveyed to a crushing machine by the coal gangue separation, feeding and conveying belt machine through a feeding chute so as to be crushed, and then, the crushed raw coal is conveyed to a movable sieve jigging separation machine to separate gangue from clean coal;

the separated gangue is crushed by a gangue crushing machine, and then, the crushed gangue is conveyed to a gangue bin by a gangue conveyer; the separated clean coal is conveyed to a coal bin by a clean coal conveyer; an overflow hole and a drainage hole are formed in a lower end of the movable sieve jigging separation machine, sewage enters a high-frequency vibrating sieve through the drainage hole, the sieved sewage and the overflowing sewage both enter a settling pond, and clean water obtained by further treatment is circularly supplied to the movable sieve jigging separation machine; the underground movable sieve jigging separation method has the advantages of large separation size range, a small amount of water used by equipment, and a simple process system;

step 4: conveying the separated gangue to an underground gangue bin by a gangue conveying belt, then, conveying the separated gangue to a gangue filling and coal efficient stope face from the underground gangue bin by the gangue conveying belt to perform filling treatment, and then, arranging a filling synergistic caving type fully mechanized coal face; and

step 5 (as shown in FIG. 3): according to the volume of the gangue separated by the coal gangue separation system, designing a length of a filling section 4 of the filling synergistic caving type fully mechanized coal face, arranging a filling section stope face, and performing equipment selection and matching; according to mine production capacity, designing a length of a caving section 6 of the filling synergistic caving type fully mechanized coal face, arranging a caving section stope face, and performing equipment selection and matching; and arranging a transition section 5 of the filling synergistic caving type fully mechanized coal face between the filling section 4 and the caving section 6, arranging a transition section stope face, and performing equipment selection and matching.

The equipment selection and matching of the gangue filling stope face and the coal efficient stope face should follow the principle of meeting the production capacity of the working faces, matching technical parameters of the equipment with structure performance, and realizing filling coal mining of the working faces; and

a specific technology is as follows:

a. coal mining technology: three different types of supports are arranged on a working face of a gangue filling and coal efficient stope system, where the support arranged on the filling section 4 is a filling coal mining hydraulic support 7, the support arranged on the transition section 5 is a filling coal mining hydraulic support 8 with a side guard plate, and the support arranged on the caving section 6 is a traditional fully mechanized mining hydraulic support 9; the three supports are designed to have the same unit advance and share a coal cutter 10 and a scraper conveyer 11, and coal at a exploitation site is conveyed to the coal gangue separation system by a belt conveyer for separation; the belt conveyer 18 is arranged beside a conveying lane 17;

a length of the filling section is mainly determined by the volume of the underground washed gangue; generally, when the length of the filling section is in a range of 80 to 120 m, economic and technical benefits are relatively reasonable; through research and analysis, a transition region influence range under different filling states and different exploitation conditions is about 6 m, so that a length of the transition section is generally determined to be 6 m, and four filling coal mining hydraulic supports with side guard plates are arranged; the length of the caving section is determined according to a total length of the filling synergistic caving type fully mechanized coal face, and the total length is calculated from the design production capacity of the working face; and

b. filling technology: the underground washed gangue is conveyed from the gangue bin to a porous bottom-dump conveyer 12 of the filling section of a mixed mining face through a feeder, a gangue transport rubber belt conveyer 15 and a self-moving type transfer machine 14 sequentially, and discharge holes 13 suspended on the porous bottom-dump scraper conveyer 12 at a rear part of the gangue filling section are opened according to a certain order to enable the gangue to naturally fall to a goaf; and the self-moving type transfer machine 14 and the gangue belt conveyer 15 are arranged beside a rail lane 17.

The filling synergistic caving type mixed exploitation fully exerts double technical advantages of gangue consumption and mine environment protection of solid filling fully mechanized mining and high yield and high efficiency of traditional fully mechanized mining, and the working face has high single production efficiency and meets the requirements of modern mines for production capacity; furthermore, the coal mining and filling efficiency of the working face is effectively adjusted, the filling capability and the coal mining capability are more balanced, and the purposes of efficiently mining coal and filling gangue by the working face are realized; and the filling synergistic caving type mixed exploitation realizes underground gangue on-site filling and creatively increases the productivity need of mining with filling.

Further, in the step 5, before filling of the filling synergistic caving type fully mechanized coal face, environmental disaster evaluation of the gangue is required, and if the gangue causes pollution to an underground environment, the separated gangue needs to be pretreated to reduce secondary pollution of the gangue. Specific measures include:

a. gangue soaking pretreatment: the separated gangue is soaked in water for pretreatment for several days, so that a reaction of heavy metal ions on a surface of the gangue tends to end;

and

b. gangue microorganism modification: heavy metal reaction and migration on the surface of the gangue are inhibited by adopting a microorganism culture mode, thereby preventing secondary pollution to a groundwater environment and soil.

Further, in the step 5, after filling of the filling synergistic caving type fully mechanized coal face, a goaf is monitored in real time, and if heavy metal ions are precipitated, pre-control measures are required, specifically including:

a. paving of an anti-leakage layer on a bottom plate: a dense material is adopted to pave a floor to inhibit leakage of the heavy metal ions; and

b. grouting treatment on the bottom plate: a crack of the bottom plate is subjected to grouting treatment to inhibit infiltration of the heavy metal ions.

Claims

1. A mine exploitation, separation, filling and treatment exploitation method, comprising the following steps:

step 1: determining main sources of gangue on a designed stope face according to a geological condition and an occurrence feature of a coal seam;

step 2: selecting a corresponding measure for reducing a gangue content in a coal exploitation according to the main sources of the gangue on the designed stope face, and arranging a small-volume gangue exploitation working face;

step 3: arranging an underwell coal gangue separation system, performing an equipment selection on the coal gangue separation system, and performing a coal gangue separation on a raw coal produced by the small-volume gangue exploitation working face;

step 4: conveying a separated gangue to an underground gangue bin by a gangue conveying belt, then, conveying the separated gangue to a gangue filling and coal efficient stope face from the underground gangue bin by the gangue conveying belt to perform a filling treatment, and arranging a filling synergistic caving type fully mechanized coal face; and

step 5: according to a volume of the gangue separated by the coal gangue separation system, designing a length of a filling section of the filling synergistic caving type fully mechanized coal face, arranging a filling section stope face, and performing an equipment selection and matching; according to a mine production capacity, designing a length of a caving section of the filling synergistic caving type fully mechanized coal face, arranging a caving section stope face, and performing an equipment selection and matching; and arranging a transition section of the filling synergistic caving type fully mechanized coal face between the filling section and the caving section, arranging a transition section stope face, and performing an equipment selection and matching.

2. The method according to claim 1, wherein the main sources of the gangue in the step 1 comprise: a gangue in a fully mechanized caving mining drawing technology, a dirt band in a coal seam, a gangue caved from a working face stope roof, and a gangue exploited by a coal face due to change in the geological condition; and

measures taken for reducing the gangue content in the coal exploitation according to different gangue sources are as follows:

a. for the gangue in the fully mechanized caving mining drawing technology, the gangue content in a fully mechanized caving mining is reduced by firstly detecting a top coal thickness distribution to grasp top coal thickness change and then changing a drawing interval and a drawing mode according to different top coal thicknesses;

b. for the dirt band in the coal seam, the gangue content of the coal seam with the dirt band is reduced by a layer mining mode;

c. for the gangue caved from the working face stope roof, the gangue caved from the working face stope roof is reduced by a timely support and an increase of support strength;

d. for a gangue cut by a bottom plate of a fully mechanized coal face, the gangue cut by the bottom plate of the fully mechanized coal face is reduced by changing a height of a drum of a coal cutter and applying an anti-dumping measure for the coal cutter; and

e. for the gangue exploited by the coal face due to change in the geological condition, the gangue content is reduced by firstly detecting and analyzing a degree of change in the geological conditions and then adopting measures of bypassing, working face moving and coal mining equipment parameter adjusting.

3. The method according to claim 1, wherein the filling synergistic caving type fully mechanized coal face means that a comprehensive mechanized solid filling coal mining section and a traditional comprehensive mechanized coal mining section are simultaneously arranged on one working face, and a specific technology is as follows:

a. coal mining technology: three different types of supports are arranged on a working face of a gangue filling and coal efficient stope system, wherein the support arranged on the filling section is a filling coal mining hydraulic support, the support arranged on the transition section is a filling coal mining hydraulic support with a side guard plate, and the support arranged on the caving section is a traditional fully mechanized mining hydraulic support; the three supports are designed to have the same unit advance and share a coal cutter and a scraper conveyer, and coal at an exploitation site is conveyed to the coal gangue separation system by a belt conveyer for separation; and

b. filling technology: underground washed gangue is conveyed from the gangue bin to a porous bottom-dump conveyer of the filling section through a feeder, a gangue transport rubber belt conveyer and a self-moving type transfer machine sequentially, and discharge holes suspended on the porous bottom-dump scraper conveyer at a rear part of the gangue filling section are opened according to a certain order to enable the gangue to naturally fall to a goaf.

4. The method according to claim 1, wherein in the step 5, before filling the filling synergistic caving type fully mechanized coal face, environmental disaster evaluation of the gangue is required, and if the gangue causes pollution to an underground environment, the separated gangue needs to be pretreated to reduce a secondary pollution of the gangue, specific measures comprising:

a. gangue soaking pretreatment: the separated gangue is soaked in water for pretreatment for several days, so that a reaction of heavy metal ions on a surface of the gangue tends to end; and

b. gangue microorganism modification: heavy metal reaction and migration on the surface of the gangue are inhibited by adopting a microorganism culture mode, thereby preventing the secondary pollution to a groundwater environment and soil.

5. The method according to claim 1, wherein in the step 5, after filling the filling synergistic caving type fully mechanized coal face, a goaf is monitored in real time, and if heavy metal ions are precipitated, pre-control measures are required, specifically comprising:

a. paving of an anti-leakage layer on a bottom plate: a dense material is adopted to pave a floor to inhibit leakage of the heavy metal ions; and

b. a grouting treatment on the bottom plate: a crack of the bottom plate is subjected to the grouting treatment to inhibit infiltration of the heavy metal ions.

6. The method according to claim 1, wherein a coal gangue separation method in the step 3 is an underground movable sieve jigging separation method which is specifically as follows:

underground coal gangue enters a sieving machine, slack coal of which the particle size is less than a set particle size is conveyed to a coal bin directly through a slack coal conveying belt, raw coal of which the particle size is greater than the set particle size falls into a coal gangue separation, feeding and conveying belt machine through a raw coal chute, the raw coal with a large particle size is conveyed to a crushing machine by the coal gangue separation, feeding and conveying belt machine through a feeding chute so as to be crushed, and then, the crushed raw coal is conveyed to a movable sieve jigging separation machine to separate gangue from clean coal.

7. The method according to any one of claim 1, wherein a length of the transition section of the filling synergistic caving type fully mechanized coal face is generally equal to a length of 4 to 9 hydraulic supports.

8. The method according to any one of claim 2, wherein a length of the transition section of the filling synergistic caving type fully mechanized coal face is generally equal to a length of 4 to 9 hydraulic supports.

9. The method according to any one of claim 3, wherein a length of the transition section of the filling synergistic caving type fully mechanized coal face is generally equal to a length of 4 to 9 hydraulic supports.

10. The method according to any one of claim 4, wherein a length of the transition section of the filling synergistic caving type fully mechanized coal face is generally equal to a length of 4 to 9 hydraulic supports.

11. The method according to any one of claim 5, wherein a length of the transition section of the filling synergistic caving type fully mechanized coal face is generally equal to a length of 4 to 9 hydraulic supports.

12. The method according to any one of claim 6, wherein a length of the transition section of the filling synergistic caving type fully mechanized coal face is generally equal to a length of 4 to 9 hydraulic supports.