A Model of Equilibrium Conditions of Roof Rock Mass Giving Consideration to the Yielding Capacity of Powered Supports

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Abstract

The work presents the model of interactions between the powered roof support units and the rock mass, while giving consideration to the yielding capacity of the supports - a value used for the analysis of equilibrium conditions of roof rock mass strata in geological and mining conditions of a given longwall. In the model, the roof rock mass is kept in equilibrium by: support units, the seam, goafs, and caving rocks (Fig. 1). In the assumed model of external load on the powered roof support units it is a new development - in relation to the model applied in selection of supports based on the allowable deflection of roof theory - that the load bearing capacity is dependent on the increment of the inclination of the roof rock mass and on the properties of the working medium, while giving consideration to the air pockets in the hydraulic systems, the load of the caving rocks on the caving shield, introducing the RA support value of the roof rock mass by the coal seam as a closed-form expression and while giving consideration to the additional support provided by the rocks of the goaf as a horizontal component R01H of the goaf reaction. To determine the roof maintenance conditions it is necessary to know the characteristics linking the yielding capacity of the support units with the heading convergence, which may be measured as the inclination angle of the roof rock mass. In worldwide mining, Ground Reaction Curves are used, which allow to determine the required yielding capacity of support units based on the relation between the load exerted on the unit and the convergence of the heading ensuring the equilibrium of the roof rock mass. (Figs. 4 and 8). The equilibrium of the roof rock mass in given conditions is determined at the displacement of the rock mass by the α angle, which impacts the following values: yielding capacity of units FN, vertical component of goaf reaction R01V and the horizontal component of goaf reaction R01H. In the model of load on the support units giving consideration to the load of the caving shield, a model of support unit was used that allows for unequivocal determination of the yielding capacity of the support with consideration given to the height of the unit in use and the change in the inclination of the canopy resulting from the displacement of the roof of the longwall. The yielding capacity of the support unit and its point of application on the canopy was determined using the method of units which allows for the internal forces to be manifested. The weight of the rock mass depends on the geological and mining conditions, for which the shape and dimensions of the rock mass affecting the support unit are determined. The resultant force of the pressure of gob on the gob shield was calculated by assuming that the load may be understood as a pressure of ground on a wall. This required the specification of the volume of the fallen rocks that affect the unit of powered roof supports (Fig. 2). To determine the support of the roof rock mass by the coal seam, experience of the Australian mining industry was used. Experiments regarding the strength properties of coal have exhibited that vertical deformation, at which the highest seam reaction occurs while supporting the roof rock mass, amounts to 0.5% of the longwall’s height. The measure of the width of the contact area between the rock mass and the seam is the width of the additional uncovering of the face roof due to spalling of seam topcorners da (Fig. 2). With the above parameters and the value of the modulus of elasticity of coal in mind, the value of the seam’s reaction may be estimated using the dependence (2). The vertical component of the goafs’ reaction may be determined based on the strength characteristics of the fallen roof, the contact area of the rock mass with the fallen roof and the mean strain of the fallen roof at the area of contact. In the work by Pawlikowski (2014), a research procedure was proposed which encompasses model tests and exploitation tests of the loads exerted on the support units, aimed at the determination of the vertical component of the goaf reaction (Fig. 5). Based on duty cycles of powered roof support units, a mean value of the indicator of contact stiffness between the roof rock mass and the rocks constituting the caving is determined, assuming the linear dependence between the horizontal reaction and the heading convergence. The parameter allows for the determination of the horizontal component of the goafs’ reaction in the external loading model of support units and allows for the determination of the required yielding capacity of supports, required to ensure the equilibrium of the roof rock mass. The experimentally verified model of the external loading of the units was used to conduct simulations of interactions between the KOPEX-095/17-POz support unit and the rock mass in a face characterized by the height of 1.6 m. Based on the data obtained in experiment, the variability of the yielding capacity of the support units was analyzed. A yielding capacity inclination angle of the units was determined for the registered curves (Figs. 6 and 7). At the same time, the presentation of the lines corresponding to the required yielding capacity of units and characterizing the deformability of the support units, allows for the prediction of the yielding capacity of the powered supports and the convergence of the heading in the conditions of a given face (Fig. 9).

References

  • Barczak T.M., 1993. Design and Operation of Powered Supports for Longwall Mining. Engineering and Mining Journal 28-32.

  • Barczak T.M., Tadolini P.C., 2008. Longwall shield and standing gateroad support designs - is bigger better? Coal Age. 1-26.

  • Biliński A., 2005. Metody doboru obudowy ścianowych wyrobisk wybierkowych i chodnikowych do warunków pola eksploatacyjnego. Prace naukowe - Monografie CMG KOMAG. Gliwice.

  • Biliński A.,1980. Empiryczna metoda doboru obudowy dla ścian zawałowych. Archiwum Górnictwa PAN 3, 321-344.

  • Biliński A., 1976. Dobór obudowy wyrobisk ściany zawałowej. Bezpieczeństwo Pracy w Górnictwie 2(31), 1-7.

  • Biliński A., 1975. Kryteria utrzymania wyrobiska w ścianach zawałowych. Bezpieczeństwo Pracy w Górnictwie 1(26), 1-6.

  • Biliński A., Kostyk T., Prusek St., 1997. Zasady doboru obudowy zmechanizowanej dla wyrobisk ścianowych. Bezpieczeństwo Pracy i Ochrony Środowiska w Górnictwie, Miesięcznik WUG, Katowice 3(31), 14-23.

  • Cheluszka P., Gawlik J., 2015. Computer modelling of roadheader’s body vibration generated by the working process. Vibration in Physical Systems, Vol. XXVII, 67-74.

  • Dolipski M., Remiorz E., Sobota P., 2014. Dynamics of Non-Uniformity Loads of AFC Drivep. Arch. Min. Sci. 59, 1, 155-168, Kraków.

  • Jaszczuk M., 2007: Ścianowe systemy mechanizacyjne. Wydawnictwo Naukowe Śląsk. Katowice.

  • Jaszczuk M., Pawlikowski A., 2008. Wpływ cech konstrukcyjnych stojaka na charakterystykę podatnościową sekcji obudowy zmechanizowanej. Maszyny Górnicze 1, 7-11.

  • Jaszczuk M., Pawlikowski A., 2006a. Charakterystyki podpornościowe sekcji obudowy zmechanizowanej. Zeszyty Naukowe Politechniki Śląskiej, Seria: Górnictwo 274, 211-221.

  • Jaszczuk M., Pawlikowski A., 2006b. Oszacowanie wartości nacisku skał tworzących zawał na osłonę odzawałową sekcji obudowy zmechanizowanej. Zeszyty Naukowe Politechniki Śląskiej. Seria: Górnictwo 274, 223-231.

  • Jaszczuk M., Markowicz J., Pawlikowski A., 2004a. Wyznaczanie przebiegów czasowych składowych wektora obciążenia dynamicznego sekcji obudowy zmechanizowanej. KOMTECH 2004. Ustroń, 15-17 listopad. 113-120.

  • Jaszczuk M., Markowicz J., Pawlikowski A., 2004b. Modelowanie dynamicznego oddziaływania górotworu na sekcję obudowy zmechanizowanej z wykorzystaniem zasady kinetostatyki. Zeszyty Naukowe Politechniki Śląskiej, Seria: Górnictwo 260, 403-412.

  • Kidybiński A., 1982. Podstawy geotechniki kopalnianej. Wydawnictwo „Śląsk”. Katowice.

  • Kostyk T., 2001. Dobór ścianowej obudowy zmechanizowanej a bezpieczeństwo i efektywność produkcji. Maszyny Górnicze 85, 40-43.

  • Markowicz J., 2010. Analysis of Impact of Welded Joint Dameges and Corrosion in Powered Roof Support Components on Their Operational Safety. Arch. Min. Sci. 55, 4, 799-826, Kraków.

  • Markowicz J., Ober G., Szweda St., 2004. Ocena dokładności wyznaczania obciążenia stropnicy i osłony sekcji obudowy zmechanizowanej na podstawie wyników pomiarów dołowych. Zeszyty Naukowe Politechniki Śląskiej, Seria: Górnictwo 260, 439-449.

  • Medhurst T.P., 2005a. Embracing the future. World Coal.

  • Medhurst T.P., 2005b. Practical Considerations in Longwall Support Behaviour and Ground Reaction. Coal Operators Conference, University of Wollongong & the Australasian Institute of Mining and Metallurgy. 49-57.

  • Medhurst T.P., Brown E.T., 1998. A study of the mechanical behavior of coal for pillar design. Int. J. Rock Mech. Min. Sci. and Geomech. 1087-1105.

  • Pawlikowski A., 2014. Ocena wpływu czynników konstrukcyjnych i eksploatacyjnych na podporność sekcji obudowy zmechanizowanej. Rozprawa doktorska, Politechnika Śląska, Gliwice.

  • Rajwa P., 2004. Wpływ konstrukcji stojaka hydraulicznego w ścianowej obudowie zmechanizowanej na utrzymanie stopu. Rozprawa doktorska. Główny Instytut Górnictwa. Katowice.

  • Sobota P., 2013. Determination of the friction work of a link chain interworking with sprocket drum. Arch. Min. Sci. 58, 3, 805-822, Kraków.

  • Stoiński K., 2000: Obudowy górnicze w warunkach zagrożenia wstrząsami górotworu. Główny Instytut Górnictwa, Katowice.

  • Szweda St., 2004. Identyfikacja parametrów charakteryzujących obciążenie sekcji obudowy zmechanizowanej spowodowane dynamicznym oddziaływaniem górotworu. Zeszyty Naukowe Politechniki Śląskiej, Seria: Górnictwo 259, Gliwice.

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