Transportless system of development

The transportless system of development with simple stripping of overburden

TRANSPORTLESS SYSTEM OF DEVELOPMENT (EN: transportless mining system, direct overcasting system; DE: transportloses Abbauverfahren, transportloses System; FR: systeme d`exploitation sans transport; ES: explotacion sin transporte; RU: бестранспортная система разработки) is the method for the conducting of the open pit mining works, during which the overburden rocks are being moved by excavators into the internal dump for the waste rocks. This method is used, as a rule, during the development of the horizontal and slightly inclined (up to 12 degrees) layered (usually with the thickness of up to 30 metres) depositions of the useful minerals. The introduction of the transportless system of development within the USSR has started during the 1942-45 (N. V. Melnikov, A. S. Chernegov, M. M. Sokolovsky, A. M. Sharkov, and others).

They distinguish two varieties of the transportless system of development: the classical (major) one, in case of which the overburden stripping and extractive works are technologically, technically, and organizationally separated, and the "excavator with open pit" one, where these works are united. In case of the classical transportless system of development, the schemes for the stripping of the overburden works are divided into the simple ones and complicated ones. The simple schemes, namely, without the secondary movement of the overburden rocks (without the secondary dump for the waste rocks) are used within the places and deposits with the thickness of the waste rocks at most 15-30 metres, and the complicated schemes, namely, with one or several secondary movements of the part or entire volume of the primary dump for the waste rocks (with the secondary dump for the waste rocks) in case of the thickness of the waste rocks at most 30-40 metres. In case of the greater thickness of the waste rock, they develop according to the transportless system of development only the lower (major) bench, but they develop the upper (advanced) benches with the usage of the transport, transport-dumping, or special systems of development. In case of the complicated schemes, on the account of the secondary movement of the overburden rocks into the secondary dump for the waste rocks, there is cleared across the entire front of the works the stripe of the goaf space, onto which there is being placed the primary dump for the waste rocks from the subsequent overburden stripping stope.

They distinguish the complicated schemes of the overburden stripping works with usual primary dumping of the waste rocks, and with the preliminary dumping of the waste rocks. In the first case, the overburden stripping works and the dumping works are technologically and technically separated, in the second case the overburden stripping works on the lower bench or sub-bench and the primary movement of the waste works are technologically and technically integrated. Within the USSR, there have been developed and are widely used three major complicated schemes for the overburden stripping works with the preliminary dumping of the waste rocks, namely, the Moscow regional, Ukrainian, and Raichikhinsk ones. In case of the Moscow regional scheme, the surface of the preliminary dump is located below the working place of the overburden stripping bench; the height of the preliminary dump is equal to or less than the height of sub-dump of the overburden bench; the surface of the primary dump is of the crest or flat-crest shape. In case of the Ukrainian scheme, the surface of the preliminary dump is also situated below the working place of the overburden stripping bench; the height of the preliminary dump within it is more than the height of the sub-dump of the overburden stripping bench, the surface of the primary dump is usually of the crest shape. In case of the Raichikhinsk scheme, the surfaces of the preliminary dump and of the working place of the overburden stripping bench coincide; the height of the preliminary dump is equal to the height of the sub-dump of the overburden stripping bench, the surface of the primary dump has the flat-crest or flat shape. The variation of this scheme for the overburden stripping works is the Cheremhovsky scheme.

The schemes for the overburden stripping works of the transportless system of development also differ by the type of the used excavators, and by their placement according to the height of the working zone (Figure # 1, and Figure # 2).

The transportless system of development with the usual secondary dump for the waste rock

In case of the simple and complicated schemes with the usual secondary dumping, there are used the power shovels and walking draglines, in case of the complicated schemes with preliminary dumping, there are used only draglines (at the open pits within the USSR, they mainly use the transportless systems of development with walking draglines). In case of the schemes for the overburden stripping works according to the transportless development system, the power shovels are always installed onto the roof of the layer of the useful minerals (Figure # 2b), the draglines are installed onto the lower place, intermediate horizon, and the upper place (Figure # 1, and Figure # 2a) of the bench, which is being developed by them. The excavation of the overburden rocks by two benches is performed by the power shovel and dragline or only by draglines.

The development of the useful minerals in case of the classical transportless development system is performed mainly using single bench by the open pit excavators in combination with the railway, road, and conveyor transport, by the bucket-wheel excavators in combination with the railway and conveyor transport, by the draglines in combination with the conveyor transport, and by the single-bucket loaders. The useful minerals are transported above the soil or the roof of the layer. In case of the "excavator and open pit" transportless development system, the extractive and overburden stripping works are performed alternately by the single dragline. The useful mineral, which has been excavated, is loaded onto the railway or conveyor transport, or is being stored onto the edge of the open pit into the bulk dump, which is later removed with the help of the extractive equipment, or with the help of the means for the hydraulic mechanization. They develop the overburden rocks using the single bench without its division, and with its division into the sub-benches.

They distinguish 4 major variants for the development of the waste rocks by the single-bucket excavators in case of the simple and complicated schemes for the overburden stripping works with the usual secondary dumping: using single bench without its division and with its division into the sub-benches; using two benches without the division and with the division of the lower bench into the sub-benches. In case of the complicated schemes for the overburden stripping works with preliminary dumping, waste rocks are being developed using single bench with its division into the sub-benches, using two benches without the division and with the division of the upper bench into the sub-benches. In case of the transportless development system, the capital trenches are not conducted onto the working overburden stripping horizons. The descent onto them of excavators and drilling rigs, the exit of excavators and drilling rigs onto the surface, the delivery of the materials and spare parts, the passage of the auxiliary equipment, are performed along the temporary ramps, which are being constructed along the working edge of the open pit.

In case of the classical transportless development system, the extractive horizons are unsealed using the external trenches with the central and flanking emplacement from the non-working edge, or in combination with the advanced cutting trench from the working edge, using the sliding ramps from the side of the working or non-working edges, using the external trench together with the sliding ramps. In case of the "excavator and open pit" transportless development system, it is not required the conduct of the capital workings onto the extractive horizon.

The open pit field, which is being developed according to the transportless development system, is divided into the sections, for each of which there is provided the most effective mining and transport equipment. The front of the works of the section according to the classical transportless development system comprises one or two blocks. In the first case the overburden stripping and extractive works within the block are conducted simultaneously, in the second case the works are conducted alternately. The organization of the mining works within the block depends mainly on the emplacement of the capital trenches relative to the boundaries of the block. If these trenches are provided at the both flanks or within the centre of the block, then they divide it into two limbs, which permits us to conduct the overburden stripping and extractive works alternately at each limb. Within each block or limb of the block, the working movement of excavator may be conducted along one or both directions (the one-sided and shuttle organization of the works respectively), and the overburden stripping stope may be excavated during one or two passages of excavators.

The transportless system of development with complicated stripping of overburden

The transportless development systems are the most economical systems in case of the open pit method for the development of the useful minerals. It has got the greatest distribution at the coal deposits. At the open pit mines within the coal industry, the transportless development system in comparison with the transport development system ensures the decrease of the labour requirements for the overburden stripping works by 3.8 times, and the decrease of the expenditures per 1 cubic metre of overburden by 2.5-3 times. Abroad, the transportless development system has got the greatest usage during the development of the coal deposits within the USA, where its share within the overburden stripping works amounts to approximately 75% (1979). The area of the usage for the transportless development system within the USA according to the type of the operated deposits, and according to the greatest thickness of the overburden rocks, is analogous to the corresponding area of the usage for the transportless development system within the USSR. During the overburden stripping works in case of the transportless development system within the USA, up to the 70-ies, there were mainly used the power shovels with the buckets with the volume capacity of up to 153 cubic metres and with the length of the boom of up to 70 metres. The worsening of the conditions for the operation of the deposits has caused the increase of the volumes of usage of the walking draglines with the bucket with the volume capacity of up to 168 cubic metres and with the length of the boom of up to 94 metres. Within the USA, the usage of the transportless development system is considered economically feasible in case of the overburden stripping ratio of up to 25-30 cubic metres per tonne.