SUST Studies, Vol. 12, No. 1, 2010; P:79-84

Inclined Drift Method for Dispersed Rock Handling of

Madhapara Hard Rock Mine, Bangladesh

A.K.M. Badrul Alam1, M Farhad Howladar

2, Choudhury Quamruzzaman

3 and Farid Ahmed

3

1 Department of Mining, Institute of Mining, Mineralogy and Metallurgy (IMMM), BCSIR, Joypurhat 2Dept. of Petroleum and Georesources Engineering, Shahjalal University of Science and Technology,

Sylhet 3114, Bangladesh. 3 Department of Geology and Mining, University of Rajshahi, Bangladesh.

Email: dmfh75@yahoo.com

Abstract

Madhayapara Hard Rock Mine has the annual production target of 1.6 million ton. During the

loading and unloading of hard rock to bring it to the surface, certain amount of rock would be

dispersed and the dispersed rock should be handled for the economical as well as technical

point of view. The inclined drifting ranges between -270m and -334.8m, because -270m is the

production level and the arresting bean is situated in -334.8m level. The required width-height

ration for the inclined drift is 1.18. Considering the ratio, the stability of the inclined drift

method with respect to allowable compressive and tensile stress was examined and found that

the inclined drift would be stable within the stress field. It is found that the width and height

of the drift, height of the arch, side radius of the arch, center radius of the arch, vertical sided

portion of the drift and the finished area of the arch would be 3.5m, 2.96m, 1.16m, 0.96m,

2.42m, 1.18m and 9.48m2 respectively.

1. Introduction

Bangladesh lies between 22°34″and 26°38″N latitudes and 88°01″ and 92°41″E longitudes and as a

consequence falls in the northeastern part of south Asia. The location map of the study area is given in figure

1.1. Every mine has the loading and unloading facilities. The loading and unloading is done with in the skip

shaft shown in figure 1.2. A skip bucket is generally used to bring the rocks to the surface by loading and

unloading the bucket. After loading the skip bucket through the loading arrangement the rocks bring to the

surface through the skip bucket to the surface. During the loading and unloading process certain amount of rock

would be dispersed. The dispersed rock should be handled, in economical as well as technical point of view.

Thus the purpose of the research is to apply the inclined drift method to handle the dispersed rock properly in

the mining industry, Maddhapara Hard Rock Mine, Bangladesh.

80 A.K.M. Badrul Alam1, M Farhad Howladar2, Choudhury Quamruzzaman3 and Farid Ahmed3

Figure 1.1 Location map of the study area (Modified after Rahman, 1987).

Figure 1.2 Longitudinal section of skip shaft (KSSCC, 1996)

2. Width-Height Ration of the Inclined Drift

The amount of dispersed rock would be 1.15t/shift and the single track mine car would be enough to handle the

dispersed rock (Badrul, 2004). For the single track mine car 0.7m foot path and 0.25m in opposite side of the

drift and the railway width would be 2.55m (figure 1.3 ). So 3.5 m (0.7+0.25+2.55) of total width of the inclined

drift would be needed. The height of the rail track is 0.3m and the mine car height is 1.50m (figure 1.3) and the

height of the arch is 1.16m. So the total height would be 2.96m (1.50+0.3+1.16). So the width height ration that

would be needed for the inclined drift is 1.18 (3.5/2.96).

Figure 1.3 Width-height of rail track and mine car.

Inclined Drift for Dispersed Rock Handling for Maddhapara Hard Rock Mine, Bangladesh 81

3. Stability of the Inclined drift against stress field

The required width-height ration of the inclined drift is 1.18. The effect of compressive and tensile stress on the

roof and sidewall of the drift was examined considering different width height ratio. In this purpose the

following equations of Brady and Brown, 1985 were used. The equations are as follows-

δB = Tensile stress = Roof wall pressure = P(K-1+2K/q)……………………......……..(1)

δA = Compressive stress = Side wall pressure = P(1-K+2q) …………………………..(2)

P = vertical stress, K = ratio of horizontal – vertical pressure, q = ratio of width - height

3.1. Total vertical pressure The vertical pressure in the production level and in the level of arresting bean i.e., 334.8m was determined by

using the following equation-

P = Z × γ ……………………………………….......................................................… (3)

Z = Depth from surface, γ = Unit weight

i) The void ratio of the subsurface rock was determined by using the following equation-

ρd = GS × ρw / (1+e) ……………………..............................................................…… (4)

ρd = dry density, GS = specific gravity, e= void ratio, ρw = density of water

ii) The unit weight was determined by using the following equation-

γ = GS (1+W) × γw / (1+e) ………..................................................…………….…….(5)

ρd = dry density, GS = specific gravity, e= void ratio, ρw = density of water

After determination of the void ration and using the value in equation 5 the unit weight of the subsurface rock

was determined. After having the unit weight value the vertical pressure was calculated by using the equation 3.

The data of specific gravity, moister content and dry density are from KSSCC, 2001 for the subsurface

sedimentary rock which is up to 145.69m after this depth the hard rock started at the skip shaft position. So,

vertical pressure up to 145.69 was determined by using the equations 3, 4 and 5. The production level is in -

270m therefore the thickness of hard rock is 124.31m (270-145.69). Similarly the arresting bean is in 334.8m so

the hard rock thickness in -334.80m level is 189.11m (334.80-145.69). The unit weight of the hard rock is 21.26,

Kn/m3 (KSSCC, 1996). Thus the vertical pressure of the hard rock at -270m level is 2642.83 KPa and for -

334.80m level is 4020.47 KPa. The vertical pressure calculation results are shown in Table 1. For understanding

the Table-1, please check the appendix-1. The total vertical pressure for -270m level is 5696.71 KPa

(3053.88+2642.83) and for -334.80 m level is 7074.35 Kpa (3053.88+4020.83).

3.2. Compressive and Tensile stress

After putting the vertical pressure and the horizontal-vertical pressure ration (0.37, KSSCC, 1996) in the

equations 1and 2 the following equations for -270m and for -334.8m level were derived.

270m level Vertical pressure is 5696.71Kpa

δA = Compressive stress = P(1-K+2q)

= 5696.71 (1-0.37+2q) = 5696.71(0.63+2q) …………….(6)

δB = Tensile stress = P(K-1+2K/q)

=5696.71(0.37-1+2×0.37/q) = 5696.71(-0.63+.74/q) ………...(7)

334.80m level

Vertical pressure is 7074.35Kpa

δA = Compressive stress = P(1-K+2q)

= 7074.35 (1-0.37+2q) = 7074.35(0.63+2q) …………….(8)

δB = Tensile stress = P(K-1+2K/q)

= 7074.35(0.37-1+2×0.37/q) = 7074.35(-0.63+.74/q) ………...(9)

Using the equations (6), (7), (8) and (9) and taking different values for q corresponding Compressive and

Tensile Stress were determined. By using these data a graph has been prepare which is shown in figure 1.4.

3.3. Compressive and Tensile Strength

According to the the test result of core samples of KSSCC, 2001 report on geologic survey of borehole the

compressive strength is 92225.7 Kpa and the tensile strength is 9750 Kpa. Design compressive and tensile

strength is 73780.56 Kpa and 7800 Kpa respectively (KSSCC, 2001). The allowable compressive and tensile

stress is 24593.52 Kpa and 2600 Kpa respectively. The calculation is shown as follows-

σ allowable = σ design / FS = 73780.56 / 3 = 24593.52 Kpa

τ allowable = τ design / FS = 7800 / 3 = 2600 Kpa

82 A.K.M. Badrul Alam1, M Farhad Howladar2, Choudhury Quamruzzaman3 and Farid Ahmed3

3.4. Results and discussions By using the different values of compressive and tensile stresses with varying q value using the equations

6,7,8,9 and considering the allowable compressive and tensile stress the following figure has been prepared.

Figure 1.4 Width-height ratio and corresponding compressive and tensile stress.

From the figure 1.4 it is found that the required width height ratio is 1.18 which is within the allowable

compressive and tensile stress. So the width-height ratio 1.18 is applicable for the drift considering the stress

field.

4. Inclined Drift Opening

The following calculations for the inclined drift are done by following the empirical formulas of Juchie, 1998.

The Width of single track of the inclined drift that would be needed is 3.5m

B = m + n + a = 3.5m

B = width of drift; m = footpath = 0.7m; n = area in the left side = 0.25m; a = railway width = 2.76m

As we know that the width-height ratio that would be needed is 1.18 then the height of the drift would be

B/H=1.18; 3.5/H=1.18, H=3.5/1.18= 2.96 m

The essential calculation for the inclined drift following the empirical formulas of Juchie, 1998 is shown as

follows- ƒo =B/3 =3.5/3 =1.16 m

1) The height of the arch: h = H- ƒo = 2.96-1.16 = 1.8 m

2) The height of the vertical sided portion of the drift

3) Side radius of the arch

R= 0.262B= 0.262×3.5= 0.916 m

4) Center radius of the arch

R= 0.692B= 0.692×3.5= 2.422 m

S=3.5(1.8+0.91)= 9.48 m2

5) Finished area of the arch

6) Length of the perimeter of the drift

P = 2H + 2.33B = 2 × 2.96 + 2.33 ×3.5 = 5.92 +8.155 = 14.075 m

Inclined Drift for Dispersed Rock Handling for Maddhapara Hard Rock Mine, Bangladesh 83

Figure 1.5 Arch shaped inclined drift.

5. Conclusion

The inclined drift method can be implemented for dispersed rock handling in the mine. Considering the required

width height ratio 1.18 with respect to the allowable compressive and tensile stress and it is found that the

required width-height ratio 1.18 is applicable for the drift. It also found that the width and height of the drift,

height of the arch, side radius of the arch, center radius of the arch, vertical sided portion of the drift and the

finished area of the arch would be 3.5m, 2.96m, 1.16m, 0.96m, 2.42m, 1.18m and 9.48m2, respectively.

References

[1] Rahman, A., (1987) Geology of Madhayapara area, Dinajpur district, Bangladesh. Rec. Geo. Surv.

Bangladesh, V.5,n.2 P.1-61.

[2] Juche, 1998. Driving and mining, Kimcheck University of Technology, P.

[3] KSSCC (Korea South South Corporation, 2001). Geological Survey report of the Bore Logs, (Unpublished

report).

[4] KSSCC (Korea South South Corporation), (1996). Design Project Report on Development of Madhayapara

Hard Rock Mine in Bangladesh (Unpublished report).

[5] KSSCC (Korea South South Cooperation Corporation), (1998) Design Project Report Madhayapara Hard

Rock Mine in Bangladesh. (Unpublished report).

[6] Badrul Alam A.K.M. Feasibility of Different Methods of Dispersed Rock Handling of Madhayapara Granite

Mining Company, Dinajpur, Bangladesh. (Unpublished 4th year research project, University of Rajshahi,

Bangladesh).

84 A.K.M. Badrul Alam1, M Farhad Howladar2, Choudhury Quamruzzaman3 and Farid Ahmed3

Appendix-1

Table1.The calculated results of vertical pressure.

Submitted: 7th April, 2009; Accepted for Publication: 15th November, 2009

Form

ati

on

Dep

th

(m)

Thic

kn

e

ss

(m)

Sp

ecif

ic

gra

vit

y

Mo

istu

r

e

con

ten

t

Dry

den

sity

(gm

/cc)

Vo

id

rati

o

Un

it

wei

ght

Kn

/m3

Ver

tica

l

pre

ssure

Kp

a

D

U

P

I

T

I

L

A

0 0 0 0 0 0 0 0

9.44 9.44 2.65 26.4 1.65 0.60 20.43 192.94

12 2.56 2.68 26.1 1.61 0.66 19.89 50.93

15.84 3.84 2.63 17.9 1.62 0.62 18.71 71.87

28.34 12.5 2.69 15.2 1.60 0.68 18.06 225.79

39.62 11.28 2.62 14.7 1.91 0.37 21.46 242.17

49.07 9.45 2.62 19.8 1.81 0.44 21.25 200.81

52 2.93 2.62 13.1 2.00 0.30 22.16 64.95

57.3 5.3 2.68 18.7 1.71 0.56 19.89 105.42

61.87 4.57 2.62 18.5 1.67 0.56 19.89 88.62

65.83 3.96 2.63 18.5 2.21 0.19 25.66 101.63

69.79 3.96 2.64 18.5 1.96 0.34 22.76 90.13

73.76 3.97 2.66 16.9 2.03 0.31 23.25 92.32

79.24 5.48 2.63 15.1 2.37 0.10 26.73 146.49

86.25 7.01 2.62 21.2 1.86 0.40 22.09 154.86

93.87 7.62 2.65 13.2 1.89 0.40 20.096 159.76

103.02 9.15 2.62 18.3 1.77 0.48 20.52 187.76

107.89 4.87 2.62 16.8 1.82 0.43 20.83 101.45

114.3 6.41 2.65 26.2 1.89 0.40 23.37 149.83

387.046 2427.73

T

U

R

A

124.05 2.71 2.63 25.38 1.50 0.75 18.41 179.58

126.18 2.13 2.64 20.98 1.27 1.0 15.04 32.05

140.20 14.02 2.67 20.95 1.99 0.34 23.57 330.56

444.066 2969.92

BASE

MENT

142.03 1.83 2.65 23.10 1.34 0.97 16.16 29.58

145.69 3.66 2.66 30.73 1.16 1.29 14.85 54.38

475.076 3053.88