3. DESCRIPTION OF THE INVENTION
Coal/minerals are being extracted since inception of man himself - initially by quarrying of near surface limited mineral reserves (low depth say 15 m or so) followed by underground mining for total extraction. In case of u/g mining, galleries were driven for obtaining minerals and pillars left for natural support (gradually timber props were introduced as artificial support as substitute for pillars). Till adequate size pillars were left for support, natural equilibrium of strata could be maintained and there was no collapse or crushing of extracted area and hence no impact on surface. However, as demand of minerals started increasing, efforts were made to reduce size of pillars or to partially extract them for obtaining more minerals. This process caused reduction in support provided by pillars and extracted area started collapsing or caving. This was termed as CAVING EXTRACTION which damaged overlying rock layers and surface over workings subsided causing damage to surface buildings, roads, other structures as well as inundation of workings by water on surface or in overlying waterlogged workings.
In 1885, coal extraction was going on in an American Coal Mine with caving below an old Church which was revered by people of the area. Colliery Management feared collapse of the Church and requested Pope to vacate and shift it. Pope and local people got worried and started praying to God to save the Church. Pope constantly prayed and finally God appeared in his dream and advised Pope to approach management and ask them to fill the void created by coal extraction and the Church would be saved. Pope described his dream to colliery management and they agreed to obey to the order of the God. The extraction area was filled with the ash available near the mine hydraulically and the Church got saved. THIS GAVE BIRTH TO GOD GIFTED STOWING TECHNOLOGY for complete extraction of coal/minerals below surface buildings and structures, rivers, rails, waterlogged workings etc with no impact of mining on surface i.e. total safety of surface structures. Since 1885, this method of extraction with stowing - STOWING EXTRACTION - in place of caving extraction - became very popular for protection of surface buildings, towns, etc, prevention of fires, highest percentage of extraction with maximum safety.
Coal based Thermal Power Plants have been meeting power requirement all over the world (except oil & gas rich countries). In India, coal has strategic importance due to heavy imports of petroleum products since long. Coal has mainly carbon (also hydrocarbons) that burns and produces heat while good percentage of coal has inert material - mineral matter that does not burn and is left as ash as coal burns. Indian coal being used by power plants has high ash - 35/40% - meaning thereby that

each tonne of coal produces about 0.4 tonne ash (70% is carried by air currents in form of fly ash and balance - bottom ash in form of clinker, is again crushed and powdered to nearly same size as fly ash and mixed with it such that total ash comes within the definition of fly ash). Disposal of ash on surface poses numerous problems to environment and its disposal into underground voids created by coal extraction - place of its origin - has been found most effective and environment friendly.
India has specific geomining conditions having strong hard massive sandstone roof that does not cave easily and hence stowing extraction is essential for coal extraction. River sand has been used for stowing since 1912 in India and phenomenon of disposal of fly ash in underground voids by stowing is of recent origin and hence efforts are being made to develop technology for fly ash stowing since mid eighties (first trial made at Lodna Colliery of Bharat Coking Coal Ltd in about 1987) followed by Singareini Collieries Co. Ltd (SCCL) in Andhra Pradesh since mid nineties. However, all trials failed and its use was discontinued till the Inventor (only Ph.D. in Hydraulic Stowing in India and second in the world) was asked to establish the technology of fly ash stowing including its total plant design in 2001 and plant construction started in Feb, 2002 at Jarangdih Colliery, Kathara Area, Central Coalfields Ltd (Ranchi) in the state of Jharkhand. The Inventor studied the trials made earlier and based on his experience, devised new method of slurry formation by dumping fly ash in open ground bunker and washing the same by directing water jets created by pump through a nozzle mounted on a portable Hydromonitor. The water jet from hydromonitor formed fly ash slurry in the bunker itself which had sloping floor such that slurry gravitated down from all points of bunker into a Mixing Trough connected to underground pipeline through borehole. Additional water was added to the slurry in Mixing Trough to control required concentration. The slurry flowed through stowing pipeline into the void to be stowed. The other reason of failure of earlier trials was conventional bamboo matting barricade supported by timber props that had no capacity to withstand side thrust exerted by fluid slurry on barricade. This barricade proved adequate for sand stowing wherein water gets released quickly (within 15 mts) and hence no fluid pressure is exerted on barricade while water release is very slow in case of fly ash slurry such that stowed mass remains fluid exerting . Thus, bamboo matting barricade burst when total stowed fly ash massflowed into lower galleries and finally into sump creating unsafe conditions in the mine. Major problem of conventional bamboo matting and timber props barricades is its being pushed back on account of side thrust due to slurry pressure as props are simply tightened against roof and floor and are bound to be pushed back.

Considering these difficulties and also that slurry pressure is very high in case of fly ash slurry, the Inventor designed steel barricade supported by sliding angle props in two parts to be bolted together after being keyed into roof and floor holes. In case of fly ash stowing, slurry remains fluid for much longer time due to slow release of water. It was decided by inventor that sliding steel angle props be rounded at the top and bottom (top of upper member and bottom of lower member) such that they can enter into drill holes in roof and floor (drilled with coal drill) and having holes both in outer and inner members in central part (held by clamps together) so that both members can be bolted once the members are tightened in roof and floor holes. This way, there is absolutely no possibility of steel props being pushed back due to side thrust of fly ash slurry which happened in case of stowing of fly ash with conventional timber props and bamboo matting which has been the main reason of failure of earlier trials.
While this design provided supporting structure of the barricade, quickest filtering of pure water with no fly ash coming out of barricade was equally important so that total fly ash is retained inside the void. The life of the barricade was also important as barricading material rots quickly whereby barricade will collapse, stowed fly ash would massflow in dip galleries and choke the sump disturbing pumping. Thus, Plastic Hessian - one being used for packaging of cement - was considered best as it would not rot for years, the material being plastic.
For total filtering of fine materials in Chemical Industries, blankets are used to make path of movement of solids through filtering media circuitous. Considering this fact, compressed woven coir was laid over plastic hessian and stitched to it to make it suitable for total filtering of fly ash. However, for supporting of plastic hessian, only vertical angle props could not prove adequate as hessian would bulge out and may finally shear causing collapse of barricade. Thus, for avoiding bulging, 100 mm x 100 mm square steel wire net (4 mm wires) was tied to vertical sliding angle props first and then plastic hessian with compressed coir was tied to wire nets. Though this could prove adequate for filtering, leakage from sides, roof and floor could cause catastrophe for which sealing of plastic hessian to sides, roof and floor was essential. This was achieved by folding the wire net and plastic hessian towards roof, floor and both sides to the extent of 0.6 m and special padding of compressed coir was tied at the back of hessian. Holes with coal drill (0.3 m) were drilled into roof, floor and sides and threaded and split bolts were grouted inside holes, leaving 100 mm threaded portion outside as well as plastic hessian was pressed against roof/sides/floor with the help of 150 mm x 150 mm x 3 mm plates with hole in centre. After pressing hessian against roof/floor and sides by plates, the grouted bolts were tightened by bolts over plates

(in similar way as roof bolting). Before drilling holes into roof, floor and sides, the coal or stone surfaces were chipped to remove uneven pieces so that smooth surface could be available for proper sealing of hessian against roof/sides/floor.
With careful sealing of sides, roof and floor, there would be no leakage of fly ash at all from barricade and clear water would flow out. No fly ash was visible in drainage galleries of return stowing water.
While considering stowing of fly ash, it may be noted that all industrial, municipal and chemical wastes can be powdered and mixed with fly ash for stowing. All other powdered waste materials mixed with fly ash behave similarly ash fly and as far as stowing is concerned. Though paste stowing of such mixture is common in developed countries for stowing of caved goaf, in India, conventional stowing considered adequate and have proved successful. Following Figures illustrate the Invention described above:
(I) Design of Fly Ash Stowing Bunker
(II) Design of Portable Hydromonitor
(III) Design of Mixing Trough
(IV) Design of Angle Prop for Barricade Structure
(V) Design of Compressed Woven Coir Mat over Plastic Hessian
(VI) Design of Sealing of Plastic Hessian to Roof, Floor and Sides.
4.1. FIELD OF THE INVENTION
The Invention is related to the Field of Coal/Mineral Extraction (Mining Engg.) and Optimum Disposal of All Wastes (Pollution Control & Environment Management).
Stowing (also known as Minefilling) is an important aspect of Coal/Mineral Extraction as it prevents
DAMAGES CAUSED BY UNDERGROUND MINING - subsidence causing
settlement/disturbance of foundations leading to damage of building, roads, railways, rivers and other waterbodies, other surface structures; control, quenching and prevention of mine fires; ensuring stability of workings including stabilization of unstable workings; damageless highest percentage recovery of coal/minerals, much higher standard of safety in mines due to provision of optimum permanent support ensuring least possible strata movement in present workings or overlying surface and mineral or rock layers.
There are lacs of examples that valuable coal and minerals below towns, villages, rivers, railways, other surface structures that could be damaged by caving extraction due to settlement of foundation

have been extracted successfully, without any impact on surface and surface structures, by EXTRACTION WITH STOWING (MINEFILLING).
4.2. BACKGROUND OF INVENTION
4.2.1. OBJECTIVE AND HISTORY OF MINING
Mining, in simple language, can be said to be excavation of useful earth, clays, stones, coal, gold, silver, iron ores, limestone and other minerals for use directly by man or indirectly through metals obtained from minerals in industries. Mining can be said to be as old and Man himself. He has been digging earth for house construction, has been living in caves which are natural underground mines. Kings have been constructing palaces using stones mined out from quarries , bricks from mined out earth, using copper, iron ore, coal etc for making weapons. Copper is first metal and brass is first metal alloy that man used. Copper and brass coins, utensil, weapons, decorative idols, castings have been found in ancient archeological excavations.
All these useful stones, clays, minerals were obviously obtained initially by open excavations of pondlike shape named as quarries - also known as Opencast Mines which are now mechanically excavated and are of much larger size.
Charcoal was the obvious fuel earlier which could serve the purpose of melting low melting point metals like copper, tin. zinc etc that could be used for casting decorative pieces - idols of Gods, utensils, coins, weapons etc. However, copper, brass were weak and soft; hence not suitable for war and hunting weapons. Iron was found suitable for such purposes but charcoal fire did not prove adequate for the purpose. Stony coal was visible in river banks and it could raise temp to much higher level that proved suitable for making iron by melting iron ore with limestone in blacksmith hearth. This opened large field of hunting and war weapons.
Man has been extracting coal/minerals from the bowel of the Mother Earth since his inception -initially from Quarries (opencast mines) for coal/minerals near surface followed by underground extraction when depth increased (15 m or so). Man saw and studied caves from the beginning. Caves had passages for movement and pillars for support.
4.2.2. UNDERGROUND MINING WITH CAVING
Initial underground mining was on same pattern of caves - extracting minerals from passages -galleries or roadways - leaving pillars for support. This was known by various names - Bord & Pillar, Pillar & Stall, Room and Pillar, Kamara Method etc and many other names depending on

place to place. This method was found safe and easy as pillars provided effective natural support which could be fully relied upon and hence little chance of accidents by roof or side falls. However, pillars blocked major part of mineral reserves and as demand for minerals started rising, efforts were made to extract pillars also but pillar extraction reduced the roof support provided by them and the roof started lowering/sagging and finally collapsing - caving.
Since roof could cave anytime without any warning, fatal accidents were very common due to roof and side falls. It was often the case that workings caved while area was only half extracted. After caving, workings had to be abandoned and hence hardly 30-40% mineral could be extracted leaving balance underground. This caused huge loss of valuable natural resource - CONSERVATION -suffered maximum.
4.2.3. DAMAGES BY CAVING EXTRACTION - COAL MINE FIRES & SUBSIDENCE
As workings caved, coal remained inside and fire was near certainty as air could enter workings through cracks in overlying strata. Fires once initiated continued for decades due to air circulation established by hot fire gases coming up through cracks and air entering into workings through other cracks. Thus fires continued for decades and burnt millions of tonnes of coal in Raniganj and Jharia Coalfields.
4.2.4. MINE FHIES IN COALFIELDS OF RANIGANJ, JHARIA IN INDIA, CHINA AND
INDONESIA
As earlier method of mining was with caving till God Gifted Stowing Technology got introduced in 1885, mine fires were common in coal mines. This threatened very existence of collieries and there was no effective method to control them till stowing and other fire fighting technologies (stowing, drowning, gas injection) got developed.
Mine fires have been best controlled by stowing and stowing extraction has helped preventing , occurrence of fires in coal mines. Though more than hundred countries are extracting coal by underground methods, only three countries are facing fire problems which clearly reveals that they have not taken care of containing fires since beginning.
4.2.5. DAMAGES/DEFERRED COSTS OF MINERAL EXTRACTION WITH CAVING
& FHtE CONTROL AND PREVENTION BY STOWING EXTRACTION
It is established fact that mineral is extracted with creation of more and more void which is allowed to collapse - caving extraction, the whole set of mineral beds gets disturbed due to haphazard

movement of overlying rocks and movement finally reaches surface - subsidence - damaging land and surface structures. Such damages may not be visible immediately but do appear after decades. Fires have invariably occurred in past in such caved workings as can be experienced in oldest Raniganj (1774) and Jharia Coalfields (1894). Deferred costs on protective works to salvage minerals, land, damage of surface structures by such mining damages are colossal compared to nominal cost of stowing extraction which works out to 12-15% of production cost. In case of Jharia and Raniganj coalfields, hardly 30-40% coal has been extracted by caving extraction of developed seams leaving most coal underground which has been burning for decades in many mines. Mine fires threatened the very existence of mines in Jharia Coalfields in 1930 when Govt, constituted a Committee to examine whole matter. The Committee recommended fire control by hydraulic stowing and coal extraction with stowing for prevention of occurrence of fires. Since fires require four elements to sustain - fuel, air, temp and space, filling the space by sand or inert material covers fuel coal thereby cutting its contact with air, water of hydraulic stowing cools the temp and once space filled, air can not enter. Thus stowing eliminates all the elements for existence of fire. This proved very successful and stowing cess was levied on total coal production to subsidize extraction with stowing for prevention of fires, higher recovery of coal due to practically near total extraction of pillars with little strata movement and hence much less accidents i.e. high standard of safety. Indian experience shows that fire may also occur in early stage of extraction itself when workings have to be sealed off when very little coal could be extracted. Even without fire, premature collapse of workings, which is very common in caving extraction, leads to sealing off of the workings causing loss of remaining coal. Caving extraction has caused huge loss of minerals partly left in supporting pillars and partly due to premature fires and collapse leading to sealing off of the workings.
It has been observed that subsidence in case of caving extraction is 60% of the thickness of mineral bed extracted while in case of stowing extraction, it may be zero if properly packed or maximum 5% of the mineral bed extracted in practice which is not perceived on surface.
THUS, CAVING EXTRACTION IS DESTINED TO CAUSE SUCH COLOSSAL DAMAGES, LOSS OF MINERAL RESERVES, EVEN AT MUCH LATER DATE, WHOSE COST ON RECOVERY OF MINE AND AREA MAY BE BEYOND IMAGNIATION. HOWEVER STOWING EXTRACTION CAN SOLVE ALL THESE PROBLEMS OF MINE DAMAGES.

4.2.6. WASTE DISPOSAL & STOWING
Metal mines have been producing huge quantities of waste rock underground since thousand of years. Disposal of such waste rocks has always posed problems. Manual packing of stone underground (earlier labour was very cheap) which served double purpose of waste disposal as well as packing helped in better strata control. Pillars could be reduced further as packwalls provided support to roof. Manual packing can be considered most primitive form of stowing with waste disposal. Ores produced from metal mines had much less percentage of metals (1-3%) and had to be concentrated before smelting to extract metal. This process of concentration produced huge quantities of rejects - Mill Tailings - whose disposal was again a major problem. Again here, stowing was adopted for double purpose of permanent support of roof with the result that higher percentage of reserves could be extracted ensuring higher standard of safety as well as solving problem of mill tailings disposal.
4.2.7. STATUS OF WASTE DISPOSAL IN INDIA
Metroes, other cities and towns all over the world (including India where problem is more acute due to large population compared to other countries) are facing acute problem of municipal, medical, industrial and chemical wastes disposal as they are being disposed off on surface which is proving great nuisance to the population living around such waste dumps. Availability of space for such dumps in cities is again a major problem. Medical wastes have caught our attention recently but it has assumed serious dimension now.
Industrial and chemical wastes are not being taken seriously in India as our Pollution Control Laws are not being fully implemented. In developed countries, dumping of incinerated municipal ash, industrial and chemical wastes are not being allowed to be dumped on surface. This has forced industries to get their wastes disposed off in underground mines through the process of stowing. However, India can not afford to be permanently negligent on this account. This must be started as early as possible.
4.2.8. PROBLEMS OF FLY ASH DISPOSAL
Coal is basic source of energy in India as we are deficient in petroleum and major part of our requirement is imported. About 70% of power is generated in coal based thermal power plants which are producing huge quantities of fly ash. We are producing about 100 million tonnes of fly ash and we have been making serious efforts to utilize fly ash for various purposes but hardly 3-4% is being consumed in brick manufacture, cement manufacture, land filling, soil conditioning etc. Thus, about

90% of fly ash generation is being dumped on surface in ash ponds and availability of land for fly ash disposal is posing serious problems as most of power plants are old and township has come up over land around it. Bokaro Thermal Power Station (BTPS of DVC near Bokaro Steel Plant in Bokaro District, Jharkhand) has been dumping fly ash into closed opencast mines of Central Coalfields Ltd transporting over distance of 20 kms or more. BTPS has been dumping fly ash into bunkers of stowing mines of Kathara Area for stowing free of cost as distance involved is less than that of opencast mines. Even availability of opencast mines for fly ash dumping is proving difficult as overburden has to be filled into them.
4.2.9. DISPOSAL OF FLY ASH MIXED WITH OTHER TOTAL WASTES INTO
UNDERGROUND VOD3S THROUGH PROCESS OF STOWING
Extraction of coal/minerals from u/g mines creates voids which are kept supported by temporary supports till extraction continues but once extraction is completed and supports withdrawn, voids collapse and surface and overlying rock layers sag, fracture and surface subsides causing damage to surface structures - buildings, roads, railways, and other structures.
In case voids are filled (stowed) with external inert materials which compact and form artificial bed as substitute for original coal/mineral bed extracted providing permanent support to roof and sides, original equilibrium of strata in mine remains restored and there is no impact of underground extraction on overlying rocks or surface.
Stowing serves this purpose of providing permanent support to workings and hence strata movement gets minimized ensuring high standard of safety in mines. In addition to providing support, waste material gets consumed in stowing which is great advantage. Waste generating agencies will provide financial support towards cost of stowing equivalent to what they are spending on disposal. It was under this circumstance that BTPS approached Kathara Area of CCL to develop stowing technology for stowing of fly ash and it offered free delivery of fly ash into stowing bunker of nearby collieries.
4.2.10. OTPIMUM SOLUTION FOR FLY ASH DISPOSAL THROUGH STOWING
Efforts are being made by collieries for development of fly ash stowing technology for last ten years
with little success as the whole effort lacks seriousness since it is the interest of power plants and not
collieries.
DVC has its own colliery and it is would be desirable that Bermo Colliery of DVC uses stowing
technology described and well established at Jarangdih Colliery near it. It would be further desirable

that NTPC owns it own coal mines and extracts coal by underground method with fly ash stowing so that problem of fly ash disposal gets permanently solved.
4.3. RESULTS OF STOWING TECHNOLOGY DEVELOPMENT DURING TRIAL AT JARANGDIH COLLY (CCL)
On request by BTPS, Kathara Area under Central Coalfields Ltd, conducted trial with applicant as Consultant which proved very successful. The slurry formation system of ground bunker and hydromonitor as explained earlier could stow @ of 74 m3 per hour with 37% concentration by weight. During 15 days in Dec 2004, 2200 m3 fly ash could be stowed on one shift basis. The rate of stowing in case of stowing of river sand was only 18 m3 per hour and concentration only 7%. Thus, while three shift stowing was required with sand for production of 100 tpd, only one shift stowing could prove adequate in case of fly ash. Following are the RESULTS OF TRIAL.
(I) The barricade was erected in May 2004 and trial started in May itself. The barricade has been
standing intact even after 16 months. There was no rupture or burst of barricade which amply
proved that the design is foolproof. There was no leakage from barricade. Clear water flowed out
of barricade. There was no bulging or bending of props indicating that total barricade was strong
enough to withstand fluid pressure oyer barricade.
(II) The flurry formation in bunker was perfect and slurry flowed into mixing trough smoothly
with no deposition in bunker. Hydromonitor could throw water jet to even farthest point of the
bunker so that total fly ash in bunker could be washed by water jet and slurry formed. There was
no pipe jam at all during trial over more than 30 days. Pipe jam was quite common in case of
sand stowing due to pebbles in sand. DGMS had permitted trial of only 3000 m3 but total of
4700 m3 fly ash could be stowed without difficulty.
(III) Normally, rising pipes were not allowed in case of sand stowing at Jarangdih Colliery due to fear of pipe jam. Rising pipes were laid in case of fly ash stowing to prove that flow was smooth and better in case of fly ash as size of material was absolutely uniform. It could be established that that there was no leakage or burst of stowing pipes in case of fly ash stowing while it was quite common in case of sand stowing.
(IV) Study of pipe wear revealed that fly ash caused pipe wear to the extent of 65% only as compared to sand. This was obviously due to the fact that sand particles are much harder than steel while fly ash particles are very fine so that energy of impact by particles over pipe walls is much less in case of fly ash than in case of sand.

(V) Fly ash slurry could flow much longer distance in galleries and voids without deposition
of solids. In case of sand stowing, sand forms heap near the point of discharge and hence packing
may not be tight up to the roof in the whole void unless gradient is steep. This requires stowing of
void in parts by cutting pipes at regular interval. A 30 m long void requiring about 10 pipes of 3 m
size may require cutting pipes 4-5 times. Disconnection and reconnection of stowing pipes requires
stoppage of stowing. Pipes have to be cleaned requiring flushing with water. While restarting
stowing after reconnection, again flushing has to be done. This leads to idle feed of water as well as
loss of stowing time.
In case of fly ash stowing, discharge point was kept at the topmost point of the gallery/void to be stowed and slurry could easily flow from top to bottom of void without the requirement of pipe disconnection and reconnection. Thus, fly ash stowing could continue for hours continuously without any interruption. This is the reason that one shift fly ash stowing could prove adequate instead of three shift sand stowing for production of 100 tpd of coal at Jarangdih Colliery.
(VI) It was established during trial that old workings could be best stabilized by fly ash stowing as
fly ash slurry could flow much longer distance and will start filling the void from dipmost point
without entering into the void which is not possible in case of sand stowing as sand forms heap near
discharge point. Thus stabilization of old, unstable workings through boreholes can be better done
with fly ash stowing than sand stowing as sand from vertical borebore forms heap near the bottom of
borehole so that there is no possibility of tight packing up to roof in whole area. This also requires
much larger number of boreholes for stabilization while in case of fly ash stowing, one or two
boreholes may prove adequate as fly ash slurry would flow into every nook and corner of the void
thereby ensuring much higher packing efficiency of stowing.
Followings are the Recommendations of the Trial by Colliery:
(a) There was no problem faced in mixing of fly ash in the surface bunker and transportation of fly ash slurry to underground workings in pipes.
(b) Higher rate of stowing could be achieved with fly ash as compared to sand.
(c) Less water is required for stowing and chance of jamming of pipes is also less.
(d) Construction of barricade (compressed woven filtering media) is time taking slow and costly as compared to normal barricade used during the course of normal stowing.
(e) Performance of specially constructed barricade namely compressed woven filtering media is satisfactory and it stowed well.

CONCLUSION BY COLLIERY
Fly Ash stowing may prove to be the best for stabilization of old workings and discontinued and
abandoned opencast working.
IT IS, THUS, ESTABLISHED THAT INVENTED METHOD PROVIDES COMPLETE &
SATISFACTORY TECHNOLOGY FOR FLY ASH STOWING USING TOTAL WASTES
HAVING NEARLY SAME SIZE AS FLY ASH. THIS WILL SERVE DOUBLE PYRPOSE OF
STOWING AS WELL AS TOTAL WASTE DISPOSAL AS OPTIMUM SOLUTION FOR
TOTAL WASTE DISPOSAL IN UNDERGROUND VOIDS.

ICIaim
1. Invention of Method of Hydraulic Stowing of fly ask mixed with incinerated municipal, medical wastes, hazardous chemical wastes, industrial wastes encompassing total wastes in underground coal mines with double purpose of prevention of fires, subsidences, damages by underground coal mining as well as safe disposal of total wastes into underground voids in coal mines wherefrom coal originates, wherein the method comprises the components of (i} sizing total wastes to size of fly ash (ii) mixing all the wastes to be stowed uniformly (iiij preparation of slurry of mixed wastes by dumping the material in open ground bunker and flushing with water under pressure generated by a pump through Hydromonitor, (iv) transporting the slurry through pipeline from surface at a higher level to underground void at lower level utilizing potential energy of the material at high level by gravity flow (vj filtering water of the slurry by specially constructed barricades comprising of steel angle props, followed by steel wire net and finally covered by perforated plastic Hessian used in cement packaging which has a cover of compressed coir matting for total filtration of water with near total retention of solids in void, the plastic Hessian sealed to roof, floor and sides for total sealing as well as ideal coal extraction method with hydraulic stowing of total wastes.
2. That extraction with stowing is safest and ideal method of coal extraction doing away with damaging impacts of caving extraction-fires, subsidences, lower percentage of extraction, excessive strata movement leading to roof/ side falls resulting in unsafe conditions in the mine and accidents-damaging impact on overlying/ underlying coal seams and rock layers as well as surface buildings, roads, railways and other structures, as well as geomining conditions in India- hard, massive sandstone roof that does not cave easily causing long span of overhang that throws excessive load and stresses on face hydraulic supports to crush/ collapse beyond repair require essentially extraction with stowing.
3. That Fry ash is processed material having uniform, size with no pebbles and hence flows freely and smoothly without fear of pipe jam. Fly ash proves better stowing material than sand now and hence will help in better and quick stowing of voids ensuring higher coal production and less chance of fire and subsidences. Fry ash can be mixed with other wastes powdered to same size and stowed together thereby providing ideal solution to total waste disposal in to underground mmes.

4. That I have invented a Hydromonitor having nozzle fed by water under pressure generated by a pump for flushing fly ash mixed with other wastes such that it flushes and forms slurry with water from all points of bunker throwing water up to 15m or more as required as well as designed a bunker with sloping floor such that the slurry formed by Hydromoninor flows automatically in mixing trough connected to underground pipeline.
5. That I have invented a Barridcade for retention of fly ash with total wastes in underground voids comprising of Sliding Steel Angle Props keyed into drilled holes in roof and floor and bolted in middle to provide strong supporting structure to withstand fluid pressure of fly as ash slurry, followed by steel wire net to prevent bulging of the filtering media of perforated plastic hessian used in cement packaging that may cause its rupture and mass flows of retained material, the filtering plastic Hessian again covered by compressed coir to prevent solids escaping through perforated plastic Hessian again covered by compressed coir mat to prevent escape of slurry that has been found to flow out profusely through conventional timber prop- bamboo matting barricades used earlier in fly ash stowing which caused failure of fly ash stowing using conventional barricades used in sand stowing.
6. That my invention has already been tried at Jarangdih Colliery of Kathara Area of Central Coalfields Ltd and based on successful trial, another Project for stowing of 42000 m3 of fly ash for stabilization of Sawang Colliery, Kathara Area, Central Coalfields Ltd had been approved,
7. That I have developed a method of stowing substantially as herein described alongwith accompanying drawings.
8. That I have invented a barricade for filtering media substantially as herein described alongwith accompanying drawings.