Modification of four-section cut model for drift blast design in Razi coal mine - North Iran

Transcription

1 Univesity of Wollongong Reseach Online oal Opeatos' onfeence Faculty of Engineeing and Infomation Sciences 00 Modification of fou-section cut model fo dift blast design in Razi coal mine - Noth Ian Mohammad Hossaini Univesity of Tehan, Ian Hadi Pousaeed Univesity of Tehan, Ian Publication Details This confeence pape was oiginally published as Hossaini, M and Pousaeed, H, Modification of fou-section cut model fo dift blast design in Razi coal mine - Noth Ian, in Aziz, N (ed), 0th Undegound oal Opeatos' onfeence, Univesity of Wollongong & the Austalasian Institute of Mining and Metallugy, 00, Reseach Online is the open access institutional epositoy fo the Univesity of Wollongong. Fo futhe infomation contact the UOW Libay: eseach-pubs@uow.edu.au

2 00 Undegound oal Opeatos onfeence The AusIMM Illawaa Banch MODIFIATION OF FOUR-SETION UT MODEL FOR DRIFT BLAST DESIGN IN RAZI OAL MINE - NORTH IRAN Mohammad Hossaini and Hadi Pousaeed ABSTRAT: Fou-section cut, a model simila to Swedish method, is an empiical method fo blasting design in undegound excavations. This method, often, has been used in excavating tunnels with coss section aea of moe than 0m. Using the model fo smalle tunnels needs some modifications to achieve pope quantity of the paametes. In this pape, fou-section cut method has been modified fo designing pattens fo tunnels with coss section aea of less than 0 m. The applicability of the modified vesion has been examined though seveal blasting cycles and the ultimate optimized blasting patten has been obtained. The pevious blasting patten of Razi coal mine, nea Ramian city in Golestan Povience, has been eplaced by the new patten which was poved to be much moe efficient. BLASTING PATTERN ALREDY PRATIED IN RAZI OAL MINE S DRIFT The coss section aea of Razi coal mine s dift is 9. m. Rock popeties at advance face of the tunnel ae as in Table. Table intoduces the specifications of dynamite types used in this excavation. Table points on blasting popeties of the dynamite types. Blasting patten used in the dift is illustated in Figue. Length of stemming in this patten is about m which seems inadequate and has led to long bootlegs and violent ai vibation. Theefoe, to avoid these outcomes the length of stemming had to be inceased to moe than 0. m. Result of conducting the pacticed patten is shown in Table 4. Table - Rock popeties of dift's advance face in Razi coal mine. Shea stength (MPa) Specific weigh Velocity of blasting wave (m/sec) 4000 Uniaxial compess stength (MPa) Specific enegy (Mj/m ) Tensile stength (MPa) Impedance (kg/m.sec) : Rock constant (kg/m ) Type of dynamite a b c Table - Specifications of dynamite catidges Diamete (mm) Length (m) Linea chage concentation Table - Blasting popeties of the dynamite Specific weight Velocity of detonation (m/s) Relative weight stength with espect to ANFO (%) Impedance (kg/m².sec) Specific enegy (Mj/kg) Relative bulk stength with espect to ANFO (%) Table 4 - Results of the pacticed blasting patten SD: Specific dilling (m/m ) 4.75 S: Specific chage (kg/m ).5 AE: Advance Efficiency (%) 80 Length of bootleg (m) School of Mining Engineeing, Univesity college of Engineeing, Univesity of Tehan, Ian 80 Febuay 00

3 00 Undegound oal Opeatos onfeence The AusIMM Illawaa Banch Figue - Blasting patten used in Razi coal mine dift. BLASTING PATTERN BASED ON 4-SETION UT The fou-section cut which is close to Swedish model is based on the paallel hole cut. This model stated with Langefos and Kihlstom (96) and has been futhe developed aftewads. Holmbeg published the complete blast design model in 98 (Holmbeg, 98) and was late updated by Pesson et al (00). The method suggests the expeimental equations listed in Table 5. In this Table, E and X ae dilling eo and length of each quadangle sides espectively. Due to elative easiness and pecision in dilling of diect cutting holes E is taken as zeo. The value of E fo stopping and peimete holes is calculated by Equation (Konya, 995): E H () E H m () Whee; E = dilling eo, H = blast hole depth (equal to m), = angula deviation (equal to 0.0 m/m) and = collaing eo (0.0 m). In this model, the holes in the face ae divided into sepaate sections as cutting holes, stopping holes, peimete (oof, floo and wall) holes. Fou-section cut method includes an empty hole in the cente as shown in Figue. If the numbe of empty holes is moe than one, equivalent diamete is calculated by Equation (Konya, 995): e N e () Whee; e =empty hole diamete and e = Equivalent diamete of empty holes. Febuay 00 8

4 00 Undegound oal Opeatos onfeence The AusIMM Illawaa Banch Table 5 - Equations fo blasting patten design Sections Buden (B) Spacing (S,X) emming () Fis squae cut B. 5 e X B B Second squae B B X B.5 thid squae B B.5 X B.5 ( B B ) Fouth squae B 4 B.5 X 4 B ( ( B B ) B ) opping B c E S.B S 0.5B Roof Wall Floo B c E S.B 0.B B c E S.B w B B c E S.B B f B Figue - location of holes in 4-section cut (Pesson et al 00). This model suggests that the diamete of empty hole to be moe than 75 mm. To achieve this diamete thee empty holes with 45 mm diamete is dilled. The equivalent diamete of empty holes is calculated using Equation as follows (Konya, 995): N mm (4) e e The type of dynamites that must be chaged into cut holes is detemined by Equation 5 (Jimno et al, 995): q 55 h B e B PRPANFO e 0.4 (5) Whee: q = Lineal chage concentation (kg/m), h = dilling diamete (m), e = equal diamete of empty holes, B = Maximum distance between empty hole and holes in the fist cutting quadangle (m), = Rock constant, PRP ANFO = Relative weight stength of explosive with espect to ANFO. Fequently, the possible values of lineal chage concentation ae quite limited as thee is not an ample vaiety of catidge explosives (Jimno et al, 995). 8 Febuay 00

5 00 Undegound oal Opeatos onfeence The AusIMM Illawaa Banch It s obvious that quantity of q fo stopping holes is less than that of cut holes and quantity of q fo oof and wall holes is less than that of stopping holes. Also, the quantity of q fo floo holes is moe than those of the oof and wall holes. Fo holes of m length and type of dynamites chosen fom Table 6 the values of paametes calculated by Equations in Table5 ae listed in Table 7. Table 6 - Type of dynamites chaged in diffeent holes Dynamite type a b c Sections utting opping and floo Roof and wall Table 7 - alculated blasting patten paametes. Sections Buden (m) Spacing (m) emming (m) Fis squae B 0. 7 X Second squae B X Thid squae B 0. 5 X Fouth squae B X opping B 0. 6 S 0. 7 S 0. Roof B 0. 6 S Wall B 0. 6 S 0. 7 w 0. 6 Floo B 0. 6 S f DEFIIENIES OF THE 4-SETION UT METHOD FOR SMALL ROSS SETION TUNNELS Fou-section cut is often applied to lage tunnels with coss section aea of lage than 0m. In ode to apply this method to tunnels with aea of less than 0m some modifications to the equations was found to be inevitable. Applying the taditional model would lead to some miss estimation of the paamete values some of which was found to be as follows: B in fist cutting squae is vey small. is vey small. The esults of peviously pefomed blasting patten in Razi oal Mine s difts show that the length of must be lage than 0. m. Fom the othe hand value must be moe than B (Ostva, 999). Quantity of B appeas to be small. ompaing the values of B and B 4 with smalle dimension of the tunnel coss section eveals that the thid and fouth cutting quadangles ae to be eliminated. Spacing is estimated fom S=.B. This amount is not appopiate fo tunnels whee contol blasting is equied. In such pattens S<B would be moe acceptable. The length of stemming fo holes of wall and floo with length of m seems to have been ove estimated. Results obtained fom pevious blasting patten show that stemming length of floo holes is smalle than equied. MODIFIED MODEL FOR SMALL ROSS SETION AREA TUNNELS Taking the above mentioned points into account the taditional model needs to be modified fo tunnels with aea of less than 0 m. Table 8 shows the equations suggested fo this pupose. In this Table, stemming lengths of, w, f and peimete holes spacing have been taken fom Swedish method. The hole depths ae m and the type of dynamites ae as indicated in Table 6. The paametes calculated fom equations in Table 8 ae as appea in Table 9. Febuay 00 8

6 00 Undegound oal Opeatos onfeence The AusIMM Illawaa Banch Figue illustates the patten designed based on paametes shown in Table 9. Due to estiction of tunnel dimensions, in pactice, buden of stopping and peimete holes should be educed to less than those obtained in Table 9. Such a patten, can be applied fo tunnels with aea of 8-0 m in ocks having density of about.7 kg/m. Blasting esults of this patten ae shown in Table 0. Table 8 - Modified equations fo small coss section tunnels Sections Buden (B) Spacing (S,X) emming () Fist squae B. 7 e X B 0 h B X Second squae B X B.5 0 h opping B c E S.B S 0.5B Roof Wall Floo B c B B E c c E E S 0.8B 0.5B S 0.8B 0.5B S 0.8B f 0.5B Table 9 - alculated paametes based on equations in Table 8 w Sections Buden (m) Spacing (m) emming (m) No & type of dynamite pe hole Fis squae B 0. X (a) Second squae B 0. 9 X (a) opping B 0. 6 S 0. 7 S 0. (b) Roof B 0. 6 S (c) Wall B 0. 6 S 0. 5 w 0..5(c) Floo B 0. 6 S (b) f Figue - Blasting patten based on the modified method 84 Febuay 00

7 00 Undegound oal Opeatos onfeence The AusIMM Illawaa Banch Table 0 - Blasting esults of the patten based on equations in Table 8 SD: Specific dilling (m/m ) 4.4 S: Specific chage (kg/m ).47 AE: Advance Efficiency (%) 90 Length of bootleg (m) 0.0 FINAL BLASTING PATTERN ompaison of Tables 0 and 4 implies that application of the patten shown in Figue leads to much bette esults in compae to the patten peviously pacticed. Although the model of Figue looks satisfactoy, seach fo getting lowe amounts of specific chage and specific dilling continued by gentle pactical modifications. Theefoe, the model was impoved step by step in consecutive blasting uns. Afte seveal blasting cycles, ultimate optimized blasting patten was obtained (Figue 4). As shown in Figue 4, in ultimate optimized blasting patten, fist cutting squae of Figue has been eliminated. As estimation of paametes of second cutting squae is done by using the paametes of fist squae, the late is theefoe, detemined although not made in pactice. Results of ultimate optimized and peviously pacticed blasting pattens ae shown in Table. As shown in this table, geat impovement has been achieved by the modified model. Figue 4 Final optimized blasting patten TABLE - OMPARISON OF FINAL AND PREVIOUS BLASTING PATTERNS Paamete pevious ultimate Impovement,% Specific dilling (m/m ) Specific chage (kg/m ) Advance Efficiency (%) Length of bootleg (m) Aveage: 50 Febuay 00 85

8 00 Undegound oal Opeatos onfeence The AusIMM Illawaa Banch ONLUSIONS Applying the taditional fou-section model to small coss section tunnels would lead to some miss-estimations of the patten paametes. A modification to the model is inevitable in such tunnels paticulaly fo estimation of stemming, cutting holes buden and peimete holes spacing. In fou-section model the pope value of unchaged cental hole fo tunnels with coss section aea of 8-0 m is mm. In case of small coss section tunnels the thid quadangle of fou-section cut is not equied. Although the specifications of the fist quadangle of the cut ae detemined, the holes of this quadangle cones ae not dilled. The modified model esults in geat impovement of blasting efficiency and cost saving. REFERENES Holmbeg, R, 98. hage calculations fo tunnelling", Undegound Mining Methods Handbook, SME, New Yok. Jimeno, L, Jimeno, E L and acedo, F J A, 995. Dilling and Blasting of Rocks, Balkema, Rottedam. Konya, J, 995. Blast Design, Inte ontinental Development opoation, Montvillo. Ohio, U S A. Langefos, U. and Kihlstom, B, 978. The moden technique of ock blasting, d Ed., Almqvist&Wiksell Folag AB, ockholm. Osteva, R, 999, Blasting in mines, vol., Jahad Daneshgahi of Technical Univesity of Ami Kabi, Ian. Pesson, P A, Holmbeg, R. and Lee, J, 00."Rock Blasting and Explosives Engineeing", 6 th pinting, R Pess, USA. 86 Febuay 00