BENCH STABILITY CONSIDERATIONS

A. Hussain Mines Manager

Stone is a fundamental requirement for human beings, as

it plays a vital role in acquiring shelter. It is quite Common that all

stone mines exist in very near proximity to the populated areas. Kota

has been quite fortunate that it has been blessed with a very large

deposit of dimensional lime stone, commonly known as "Kota Stone", in

Ramganjmandi , Chechat and other nearby areas. It is a cheap elegant

and quick fixing media for floor construction work. No floor stone is

cheaper than Kota Stone. At the same time it has developed a great

architectural trend by inter woven with white marble or other

decorative stones to give pleasing floor patterns. The stone is available

in blue, green, brown or their combinations. There is hardly any

substitute of Kota Stone floors for economical and functional buildings.

Extraction of this stone has not only fulfilled the need of

the local area, state and country but mining and allied operations have

provided (and still continuing) bread and butter to a very large no. of

families. Perhaps lime stone industry is the largest industry in the

region. This industry has also shared in the national development as

government earns large revenue under different heads. In addition Kota

Stone has also established a sizeable export market. which provides a

good foreign exchange to contribute towards our national economy.

The mines under study belong to M/s Goodwill Advance

Stone Company and is situated near Chechat Village in Kota district.

General information's related to the mine are as under :-

Name of Mine : M/s Goodwill Advance Stone Co.

owner : Sh. Pankaj Sethi

Sh. Rohit Seth

Location of Mine : Village - Chechat

The. - Ramganjmandi

District - Kota

Co-ordinates- 24˚ 45'50" N

75˚ 47' 46" E

Area of Mining Lease: 90,000 Sq.Met.

Mineral Worked out: Kota Stone

Mining Lease No.: 59/87

Public Road : Ramganjmando to Rawatbhata state Highway

Railway Station: Morak , 8 Km from Mines Site

Air Port: Kota , 68Km from Mines site

Working Time: Only General Shift Working

8.00 AM to 5.00 PM

Annual Production: Over Burden and Waste - 17.50 Lakh Cu.M.

(Proposed) Lime Stone - 10.- Lakh Sq.M.

GEOGLOY:

Regional : The Kota Stone deposits are located between latitudes 24˚ -

27' - 24˚ - 48' and longitudes 75˚ - 45' - 76˚ - 05'. The area is covered on

toposheets No. 45/O/113. 45/O/114, 54/D/1 and 54/D/2.

Kota Stone geologically speaking is a part of semi series of

lower VINDHYAN group. The local nomenclatures are well understood

and prevailing from the inception of the mining in this area. The

regional stratographic sequence of deposits is given as under:-

A. UPPAR VINDHYAN

1. Bhandar Series

2. Rewa Series

3. Kaimur Series

4. Semi Series

B. LOWER VINDHYAN

1. Suket Series

2. Nibahera Lime Stone

3. Jhalarapatan Sand Stones

The workable lime stone beds are locate at a depth of 25-28

met from surface and dip gently towards east direction at a rate of 1.0

met in every 100.0 met distance. Strike of the depth is North-South.

Lime stone bed is divided in to five sacks, separated from each other by

clay partings. A representative stratographic sequence of the deposit is

given as under:

S.No. Rock Thickness (Met)

1 Top Soil 0.00 -2.50

2 Overburden comprising

mixed calcareous rock

10.00-25.00

3 Top KotaStone sack 3.00 - 5.00

4 Middle Sack 2.50-3.00

5 Third Sack 3.00-4.00

6 Fourth Sack 1.25-2.00

Area comprises of various sedimentary formations distinctly separated

from each other by clay partings. Prominent joints planes traverse from

North-East to South-West direction. Geological structural problems e.g.

intrusion of quartz veins, fissures, crisscrosses and joints etc. have also

been observed at some place.

Exploitation activities may broadly be classified in to two

categories et.c.

* Removal of Overburden

* Extraction of Lime Stone

Removal of Overburden: On the top soil and sub soil exist for a

thickness of 0-2.5m. This top soil is dozed off and is transported by

dumpers, loading them using front end loaders. Thus the hard

overburden strata are exposed.

After moving the soil and subsoil, the exposed overburden

layer needs drilling and blasting. Blasted overburden is removed and

transported using front end loader- dumper/dump truck combination.

105mm diameter holes are drilled by wagon drill, for a depth of 8-9 ml.

The usual drilling pattern is 4.0m x 4.5m with proper hole staggering .

A powder factor of 10MT/Kg is achieved with following charge details in

a 9.0 M/in deep hole .

Bottom Charge : Cap sensitive primary slurry

explosives in 83mm size cartridge. 2.7 Kg.

Coloumn Charge : ANFO 20.0 Kg.

Decking : Practised

Stemming : Drill Cutting/day 2.5-3.0 Kg.

PRODUCTION FIGURES:

S.No. Year Lime Stone

Production SqM.

Overburden

Cu.M

1 2005-2006 Nil 20,000

2 2006-2007 52,786 30,000

3 2007-2008 1,57,550 85,750

4 2008-2009 2,68,650 1,14,300

5 2009-2010 7,84,921 1,60,000

PROPERTIES OF SOIL AND ROCKS

S.No. Parameter Value

1 Colour Green/Black

2 Texture Sandy Loam

3 pH 8.4

4 Bulk Density in gm/ce 1.4

5 Porosity (%) 45

6 Water Holding Capacity 49

B. Weather Parameters

Temperature - Maximum 47˚c Minimum 7˚c

Rain Fall - 50 cm to 80 cm per annum

Humidity - 30 to 70 percentage

C. Hard Rock

The Properties of hard rocks are as under:

S.No. Parameter Value

1 Bulck Density ( MT/ M 3) 1.7

2 Specific Gravity 2.46

3 Compressive

Strength(Kg/Cum2)

2160

4 Tensile Strength (Kg/cm2) 274

5 Shear Strength(Kg/cm2) 25.6

ACCIDENT STATISTICS:

Year Accident Cause

Reportable Fatal

2005-06 Nil Nil …

2006-07 Nil Nil …

2007-08 Nil Nil …

2008-09 Nil Nil …

2009-10 Nil Nil …

SLOPE FAILURE HISTORY:

No case of slope/bank failure has been noticed in enter

"Kota Stone" mining area right from inception. It has also been

observed that at many places vertical benches 35-40mtrs height have

existed for a long period without any movement.

Based upon observations and findings the anthor is of the

firm opinion that the almost vertical benches as practiced in Kota Stone

mining are quite stable and there are no chances of their failure.

However, some precautions becomes necessary to avoid any unforeseen

and underable incidences-

- Retaining walls should be constructed and maintained at the

foot of the working benches.

- To minimize ground vibrations. milli second multiple row blasting

( Axle or Redit) should be practised.

- Before the start of the work, a close and cautions inspection

should be made by the competent officials and dressing should

be carried out at frequent intervals to avoid full of loose stones

etc.

- All loose and hanging cliffs should be removed before the work

commencement.

- Further the angle of repose for dry waste dumps is about 38

degrees and moisture presence may lower if further. External and

internal waste dumps should be planned, designed and

maintained within the repose angle formations. Soils - sub soil

mixing in the waste dumps may bring down the repose angle

drastically and cause dump failure along clay storage planes

during rains. This critical situation need almost attention and

care.

- The Bench top and waste dumps should be properly drained off

so that no hydrostatic presser is built and exerted on the week

planes resifting into failures during rainy season.