The Design and Application of Rock Bolting in Coal Mine

The Design and Application of Rock Bolting in Coal Mine

Available online at www.sciencedirect.com Available online at www.sciencedirect.com Energy Procedia Energy Procedia (2011)14 000–000 Energy 00 Proce...

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Energy Procedia

Energy Procedia (2011)14 000–000 Energy 00 Procedia (2012) 280 – 284 www.elsevier.com/locate/procedia

Conference Title

The Design and Application of Rock Bolting in Coal Mine Qian kuna, Xin Xiao-dongb,Che Yu-longca* a

b

Faculty of Resources & Safety Engineering, China University of Mining & Technology, Beijing, 100083, China; School of Chemical & Environment Engineering, China University of Mining & Technology, Beijing, 100083, China; c School of Mechanics & Civil Engineering, China University of Mining & Technology, Beijing, 100083, China

Abstract In order to provide scientific and rational support plan, this paper through combining theoretical calculation and field application, designed the support means of suiting this coal in different geological conditions, the scheme must change with the actual changes to achieve the purpose of safety supporting. This scheme has important reference meaning to the support work of the follow-up new roadways. The innovation point of this paper is comparing the theoretical design with the practical support plan, to proof that the theoretical calculation is scientific and practical. Keywords: coal mine; rock bolting; theory design; application

1. Introduction In recent years, with the coal mining to the depth and the breadth development, appeared many unprecedented complex roadway in our country, Including loose broken wall rock roadway, deep high stress roadway, extra huge section of roadway and the roadway by strong mining influence, etc. To solve such problems, our country had developed high prestress and powerful anchor rod and the anchor rope support technology, the application of new bolt support technology had greatly reduced the deformation and damage of the surrounding rock. High strength, high rigidity, high reliability and low density of supporting "three tall one low" modern bolt support design concept had signally improved the roadway driftage speed and efficiency. The mine strata is a basin shape structure, the buried deep of coal seam is in the same level, so it need to face the different working conditions when mining again, and put forward different requirements to the new dig roadways support. One of the field, the thickness of the coal seam, dip angle, the lithology and thickness of roof and floor, and so on, possess different degree of change. So in view the different geological characteristics, taking different supporting the methods could guarantee the stability and security of roadway, and provided a powerful guarantee for the follow-up mining.

* Che yu-long.. E-mail address: [email protected]

1876-6102 © 2011 Published by Elsevier Ltd. Selection and/or peer-review under responsibility of the organizing committee of 2nd International Conference on Advances in Energy Engineering (ICAEE). doi:10.1016/j.egypro.2011.12.930

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2. Supporting theory 2.1. Suspension Theory Suspension theory, the effect of bolt supporting is suspended the underground chamber roof in soft rock strata to the upper part of a stable parts, in order to enhance the stability of soft rock. Which mainly used in layered rock, and close to the roof rock has steady strata, otherwise, if stability is too deep, the bolt length calculated is too long, and will not install. 2.2. Composite beam theory Composite beam theory, during the excavation of a laneway in layered rock mass, the anchor suspension effect play a second fiddle, when the roof did not possess hard and stable rock within a certain range. If there are a number of layered rock roof, the effect of roof bolting, on one hand, relying on the rock bolting to increase the friction among the strata, which is in order to prevent sliding of rock along the level and avoiding the ionospheres phenomena among the strata; on the other hand, the anchor rod can increase the shear strength between the rock and prevent the horizontal offset between the layers, so the tunnel roof anchor can locking range of several thin strata of rock to form a thick rock stratum (composite beam). Under the effect of overlying strata load, the maximum bending strain and stress of this composite beam are greatly reduced and its deflection will reduce, also. The thicker beams, the maximum stress, strain of this beam and its deflection are smaller. 2.3. The theory of caving arch The theory of caving arch think that the roadway is uniform broken, mainly used in the calculation of the roadway that the surrounding rock joints(bedding) is not particularly obvious, for example the coal roadway cut eye calculations, etc. 2.4. The of Protodyakonov’s compression arch theory The calculations of the breaking depth of roadside coal and the loose height of roof rock are ditto. The deformation and failure of the roof, floor, and sides of roadway surrounding rock has obvious synergy sex and relevance. The determination of supporting parameter must have a systematic consideration to the strengthening optimization of roadway. 3. Rock bolting design 3.1. anchor rod design Bolt support design is determining the range value (the roadside failure depth C, the roof failure height b), load value (the roof load collection degree Qr, the roadside load collection degree Qs) and the concrete parameter of bolting of failure zone. (1) The roadside failure depth C:

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⎛ ⎞ ⎜ 1000σ cc ⎟⎛ ⎜ kσ − ⎟⎜1.5 hc 2 + l 2 − l ⎞⎟ a 2⎠ ⎜ γH cos ⎟⎟⎝ ⎜ ⎝ 2 ⎠ c= u φ⎞ ⎛ kσ + ctg ⎜ 45° − ⎟ − 1 1− u ⎝ 2⎠

3

(1)

⎛ ⎞ ⎜ ⎟ MPa × 1000 10 ⎜ 2.967 − ⎟⎛⎜1.5 3.2 2 + 4.5 2 − 4.5 ⎞⎟ 5° 2 ⎠ ⎜ 25 × 340m × cos ⎟⎟⎝ ⎜ 2 ⎠ =⎝ = 1.616 0.45 45° ⎞ 2⎛ ctg ⎜ 45° − 2.967 + ⎟ −1 1 − 0.45 2 ⎠ ⎝

(2) The roof failure height b:

⎛λ + k σ / 10 ⎞ 10 (a + c ) cos a ⎜ y cr ⎟ ⎜ 1+ k σ k σ / 10 ⎟⎟ ⎜ y cr y cr ⎝ ⎠ 10 (2 . 25 + 1 . 616 ) cos 5 ° ⎛ 0 . 818 + 0 . 497 × 96 / 10 ⎞ = ⎜ ⎟ = 0 . 782 0 . 497 × 96 Mpa 1 + 0 . 497 × 96 / 10 ⎝ ⎠ (3) The roof load collection degree Qr : b =

a⎛ λγ H = Qr 2γ abK a cos ⎜1 + ⎜ 2 ⎝ 1000 K yσ cr

(4) The roadside load collection degree Qs :

⎛ k γH Qs = c⎜⎜1 + a ⎝ 1000σ cc

⎞ ⎟⎟ =129.90 ⎠

⎞⎧ ∂ 90 − ϕ ⎫ 2 ⎟⎟⎨λhc sin ∂ + γb cos tg ⎬ b − 4ac = 72.1kn / m 2 2 ⎭ ⎠⎩

(5) The parameter designs of top anchor rod: z The length of anchor rod Lbr: Lbr=b+△=0.0.782+1.15=1.932m In the actual construction process the length is 2.4m; z

The diameter of anchor rod: d = 35.52

Q

σt

= 21.75mm

(2)

(3)

(4) (5) (6)

In the actual construction process the diameter is 22mm; z The array pitch of anchor rod:

= Dr

=

105 2 × 3 × 97.417

Pr 2KQ r

⎡ KQ ⎤ ⎢1 + 1 + 8 (a − 0.2 ) r ⎥ Pr ⎥⎦ ⎢⎣

⎡ 3 × 97.417 ⎤ ⎢1 + 1 + 8 ( 2 − 0.2 ) ⎥ =1.095m 105 ⎢⎣ ⎥⎦

In the actual construction process the array pitch is 1m;

(7)

z

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The number of each row:

N= In the actual

KQr Dr 3.0 × 129.90 × 1.0 = = 4.33 Pr 90

(8)

N S =5

(6) The parameter designs of roadside anchor rod :

z

The length of anchor rod :

Lbs = C +△=1.616+0.7=2.316m

(9)

In the actual construction process the length is 2.4m; z The number of each row:

NS = In the actual

KQS Dr 4 × 72.1 × 1.0 = = 3.2 90 Pr

(10)

N S =4;

3.2. The strong support design of anchor rope z z

The array pitch of anchor rope:

Lb = 2T / (K1 × Q ) = 2 × 400 / (2 × 58.7 ) = 2.5m ;In the actual Lb=2m

(11)

The length of anchor cable anchorage

Lc = K 2T/π dP1 =2×400000/(π×18.9×10)=1348mm

In the actual Lc =1400mm; z The length of anchor rope:

L=b+Lc+L=4+1.4+0.3=5.7 m; In the actual L=6.3m

(12)

(13)

3.3. Based on the engineering characteristics and the convenience of the construction, initially proposed a support scheme: Haulage roadway: roof bolt adopted rebar anchor (φ22×2200mm), the distance between rows is 700mm×700mm, adopted anchor rope (φ15.24×7000); layout metal nets; injected concrete mortar of 50mm to close bare rock. Return airway: roof bolt adopted rebar anchor (φ22×2200mm), the distance between rows is 800mm×800mm; layout metal nets; injected concrete mortar of 50mm to close bare rock. 4. Conclusions z According to the bolt support theory, the theoretical calculation result were consistent with the actual construction plan, but in the particular geological conditions, it need to consider the actual conditions to set up a reasonable support scheme; z Rock bolting construction technology was relatively simple, convenient operation, and greatly improved the level of drifting; z In the composite conditions of soft coal seam, adapted the anchor cable supporting reinforcement measures, and cooperated with rock bolting, could effectively support for the surrounding rock.

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Pierced the feet

Fig.1 haulage roadway support scheme

Fig.2 return airway support scheme

References [1] Ma Qi-hua, Xu En-hu, Zhu Shan-de. Development of Bolting Technique in China's Coal Mines. China Mining Magazine. vol.6, No.5, 1997, p.47-48. [2] Zhang Ga. Coal Mine Bolt Support Technology .Coal Technology. Vol.27, No.8, 2008. [3] Hou Qin. Study on Cable Bolt Support and Its Application in Large Span Coal Entry of Daning [J]; 2005. [4] Zhang Dao-bing.Study of Structural Reliability on Anchoring Support of Coal Roadway [J]; 2007. [5] Yang Feng. Deformation and Failure Mechanism and Bolting Techniques Study on Dynamic Roadway of Composite Roof [J]. 2003. [6] Li Da-wang. Study of The Bolting Technique About Entry of Deep Shaft's Fracture Zones [J]; 2007.

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