DALAVOI ADANAKURICHI LIMESTONE MINE
OWNER- The India Cements Ltd.
The Adanakurichi limestone mine of ICL is situated in the revenue village of Adanakurichi of Sendurai taluk in Perambalur district of Tamilnadu. The site is located about 40 km by northeast of Ariyalur town. The mine could be approached by road from Ariyalur by traveling ahout 39 km via sendurai and mathur. The area is covered under survey of India toposheet no. S 58M/3 and M/7 between latitudes 11°20′ north and longitudes 79°20′-79°40′.
The nearest railway station is mathur. It is located on the way from Trichy to Villupuram metre gauge section of Southern railway.
The terrain is more or less flat with a gentle slope from east to west. The area is drained by seasonal river courses flowing across it, of which the Anavari odai flowing in the northwest part of the prospect is prominent.
CLIMATE AND RAINFALL
The max. temp. recorded is around 45° C during summer. The min. temp. is 21° C. The average rainfall is about 650mm.
The area belongs to the Niniyur stage of the crustaceous system, of Trichy area. The Niniyur formation was traced over a strike length of 12 km from south of Anandavadi to near Mathur where it is overlapped by sandstone belonging to cuddalore formation, further northeast, after a gap of about 5 km it was traced over a strike length of about 5.7 km in the Tamaraipoondi area. Thus the cumulative strike length works out to 17.7km.
Limestone with marl and clay
Limestone with marl and clay
Greenish clay and sandstone
PROPERTIES OF LIMESTONE
The Limestone is generally brownish yellow in colour, fine to medium grained and at some places richly fossiliferous. Marl and Clay intercalation in different proportions are not uncommon.
|Compressive Strength||31.4 Mpa|
|Tensile Strength||31.4 Mpa|
|Bulk Density||2.34 t/m3|
|Hardness on Mohr’s Scale||2.7|
The sedimentary limestone deposits of Trichy, Ariyalur, and perambalur districts belonging to cretaceous age of Indian Stratigraphy cover an area of 400 sq km between Coleroon in the south and Vellore in the north. The entire sedimentary deposits rests over a basement of granitic geneiss and charnokites. The cretaceous sedimentary formations of Trichy are broadly divided into 3 stages-Uttathur, Ariyalur and Niniyur stages.
Out of various combinations of straight and curvilinear cuts, mining method can be classified into 3 types. They are-
- Wide face method
- Block mining method
- Stepped cut method
WIDE FACE METHOD
Mining is done by layer by layer, in slices, adjacent to each other.
BLOCK MINING METHOD
The deposits are worked by block one below the other. This method can be worked where water seepage problem is present.
STEPPED CUT METHOD
The stepped cuts are slightly staggered in order to ensure sufficient bank stability. Mining of slices is done as per the ascending order of numbering. The individual cuts should ideally be situated directed next to each other and have the same milling depths in order to achieve a level surface for the supporting transport system and the auxiliary units.
MINING AT DALAVOI
Turn back layout and block mining method is followed at dalavoi project. The mining area is 1000mX800m.The entire deposits has been divided into 6 strips of 200m width namely A, B, C, D, E and F running north south. Each 200m strip is to be worked from south to north in 2m wide cuts. The width of each block is 50m and its thickness is 5m. The direction of surface miner will be along the strike and width of each will be 2m.Thickness of each slice may vary between 15 to 20 cm. The vertical section of each strip is divided into 5m thick blocks which are numbered 1,2,3 and so on and the sequences of mining has been in such a manner that at any time, the line joining the operation blocks would be parallel to the dip, so that any makeup of water will be accumulated in the dip most side wherefrom it is pumped out.
PLAN OF MINE BENCHES
The section of mine benches for stripping first 5m of the deposit, excavator is deployed that is worked by the surface miner is given below:
- Height of the bench=5m
- Width of the bench=5m
- Slope of the bench=60 degrees
CSM loads the material onto the trucks. The trucks transport the material to a hopper that is fitted to an overland conveyor, which is located at the mine mouth. The conveyor feeds the material directly to the secondary crusher after that, the material is taken to the plant for further processing.
Mining operations in Adanakurichi Limestone mine are mostly performed by surface miner 2100.Surface miner while mining makes straight cuts or curvilinear cuts. Various types of mining layouts and mining methods that are possible with SM2100-
There are 3 types of mining layouts. They are-
- Empty travel back layout
- Turn back layout
- Continuous mining layout
i) EMPTY TRUCK LAYOUT
In this layout the machines start to cutting from one end of the pit to other end of the pit when it reaches the other end the milling drum is raised and turned.
ii) TURN BACK LAYOUT
In this layout SM is made to cut in the direction perpendicular to the strike first the SM cuts from the one end to other end cutting the slices of specified thickness and alter that when it reaches the end of one pit.
iii) CONTINUOUS MINING LAYOUT
In this layout the excavation process is done by means of the continuous method. This process eliminates turning time and empty turn back. In this method the utilization of machine increases and due to that production increases. But the maintenance hours or SM is increased. Indian studies show that the curvilinear cuts increase the productivity by 10-15%. This method is further divided into 2 types based on the operation-
Initially the SM cuts the paths continuously where a large curve radius is available. Then the central portion of the deposit is mined by straight cuts.
To begin with the paths I, II, III cuts for path no.I there will be straight cut and afterwards it proceed in cut of larger curve radius and then the cuts are possible with the help of SM. Then the third cut went on straight wards and then made a turn. In this way straight and curvilinear of larger radius cuts are done under one single cut.
PLANNING OF MINE BENCH
The physics setting of the deposit makes the choice of open pit mining obvious. Mining is carried out in sub blocks of uniform height and width 5m X 200m X 800 to 1100m long sub blocks. A part is used for the plant along with better grade limestone and partly divided for stock, which is located on the western side of the mining block.
a) Pit slope:
The limestone band dips at an angle of 5 to 7° towards SE. The pit slope is at 60°.
b) Ultimate pit limit:
The planning has been limited to 25 years of operation in the west block, which corresponds to the limestone bottom of the reduced level (50m from ground level).
c) Height of benches:
The 5m vertical height is being cut in slices of O.125m (40 slices) and the machine having a width of 2m makes 100 cuts to the planned width of 200m block. The system of mining according to the block nos. are assigned in such a manner that operating benefits maintains slope of 1 to 20.The difference in the floor levels of adjoining blocks is within the operating limits of the surface mines only.