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Fig.5. Field photographs showing: (a) Gully erosion, (b) Weathered top soil, (c) Failed dump slope, (d) Tension cracks.

Figure 5 Field photographs showing: (a) Gully erosion, (b) Weathered top soil, (c) Failed dump slope, (d) Tension cracks.

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numerical simulation (Fig.3). Bhubanes-wari OCP has both internal dump as well as external dump. Maximum height of the internal dum dumping material consist main been hig gully erosion on the dump surfaces ( cracks are also identified on top of the ndicate t he initiations of failure of (Fig.5c). Tension cracks are developed portion o varies fro m 0.5 to 1.0 m. Development indicate t he vulnerability of dump fai p is about 70 meters and externa dump is 50 meters. The average slope angle of different site varies from 35° to 41°. Most of the dump y of friable rock material with varied ithology and mineralogical composition. The major rock ypes of the dump materials are sandstone, shale and carbonaceous shale. The major soil type which comprise he dump are sandy soil and loose dump base is extremely weathered (Fig.5b) and face has hly affected by rain water which has created ateritic soil. The Figs. 5a). Tension dump slope which the dump masses within the crown f internal dumps (Figs. 5c and 5d) and its width of tension cracks ure influenced by external forces (ground vibration during blasting, heavy earth moving machine etc). The internal dumps are very close to the coal exploration area and any failure of dump masses
numerical simulation (Fig.3). Bhubanes-wari OCP has both internal dump as well as external dump. Maximum height of the internal dum dumping material consist main been hig gully erosion on the dump surfaces ( cracks are also identified on top of the ndicate t he initiations of failure of (Fig.5c). Tension cracks are developed portion o varies fro m 0.5 to 1.0 m. Development indicate t he vulnerability of dump fai p is about 70 meters and externa dump is 50 meters. The average slope angle of different site varies from 35° to 41°. Most of the dump y of friable rock material with varied ithology and mineralogical composition. The major rock ypes of the dump materials are sandstone, shale and carbonaceous shale. The major soil type which comprise he dump are sandy soil and loose dump base is extremely weathered (Fig.5b) and face has hly affected by rain water which has created ateritic soil. The Figs. 5a). Tension dump slope which the dump masses within the crown f internal dumps (Figs. 5c and 5d) and its width of tension cracks ure influenced by external forces (ground vibration during blasting, heavy earth moving machine etc). The internal dumps are very close to the coal exploration area and any failure of dump masses
Fig.3. Outline of the Bhubaneswari OCP.
Fig.3. Outline of the Bhubaneswari OCP.
and geomechanical analysis of the dump materials provides useful information for better and safer designs of the dump slope. The mineralogical composition and internal structure of slope forming material were determined using XRD analysis and scanning electron microscope (SEM). Results show sandstone containing quartz, muscovite whereas shale sample contain small quantity of quartz, with chlorite and kaolinite are dominant. Soil samples analysis reveals that major minerals are quartz, magnetite, and potassium magnesium silicate (Fig.6-9). The presence of clay minerals result in the rapid decrease in cohesion during rainfall, as may cause extensive damage to lives and mine properties. Representative samples were collected from different strategic locations of the dump slope to determine the geo- mechanical characteristics of soil and rock units.
and geomechanical analysis of the dump materials provides useful information for better and safer designs of the dump slope. The mineralogical composition and internal structure of slope forming material were determined using XRD analysis and scanning electron microscope (SEM). Results show sandstone containing quartz, muscovite whereas shale sample contain small quantity of quartz, with chlorite and kaolinite are dominant. Soil samples analysis reveals that major minerals are quartz, magnetite, and potassium magnesium silicate (Fig.6-9). The presence of clay minerals result in the rapid decrease in cohesion during rainfall, as may cause extensive damage to lives and mine properties. Representative samples were collected from different strategic locations of the dump slope to determine the geo- mechanical characteristics of soil and rock units.
Fig.4. Production of Coal and OB at BOCP.
Fig.4. Production of Coal and OB at BOCP.
Fig.6. SEM photomicrograph of sandstone
Fig.6. SEM photomicrograph of sandstone
Fig.7. SEM photomicrograph of Shale
Fig.7. SEM photomicrograph of Shale
loss of surface frictional contact between the grains due to high absorption of water. The SEM/EDEX analysis shows the surface morphology and elemental composition of the sandstone and shale. The presence of high percentage of oxygen intensify the chemical weathering process accompanied with rain water which significantly reduce the shear strength of the materials of a dump.
loss of surface frictional contact between the grains due to high absorption of water. The SEM/EDEX analysis shows the surface morphology and elemental composition of the sandstone and shale. The presence of high percentage of oxygen intensify the chemical weathering process accompanied with rain water which significantly reduce the shear strength of the materials of a dump.
Fig.10. The Plasticity chart The number of factors which cause the dump failure are well explained by Singh et al. (1992); Singh et al. (1994); Singh et al. (2006); Kainthola et al. (2011); Singh et al. (2013). The factors which cause the failure are geometry, strength of dump material, hydrological and rain water condition of the dumping site, bearing strength of dumping ground and external load (Singh et al. 1992; Singh et al. 1994; Singh et al. 2006). The presence of structural disturbances like fault, joints and cracks are also responsible 1994; Singh et al. 2006). The presence of structural
Fig.10. The Plasticity chart The number of factors which cause the dump failure are well explained by Singh et al. (1992); Singh et al. (1994); Singh et al. (2006); Kainthola et al. (2011); Singh et al. (2013). The factors which cause the failure are geometry, strength of dump material, hydrological and rain water condition of the dumping site, bearing strength of dumping ground and external load (Singh et al. 1992; Singh et al. 1994; Singh et al. 2006). The presence of structural disturbances like fault, joints and cracks are also responsible 1994; Singh et al. 2006). The presence of structural
Table 1. Plasticity Index and moisture content of soil Table 2. Geomechanical properties of rock
Table 1. Plasticity Index and moisture content of soil Table 2. Geomechanical properties of rock
for dump failure. Groundwater flow condition plays a critical role on the stability of dump slope. Heavy monsoonal rainfall resulting raise in groundwater table is often believed to be the cause of dump slope instability (Yellishetty et al. 2010). Rainfall percolating through the weathered soil has triggered slope failures in circular shape due to loss of cohesion. The surface water flow also affect the dump stability as it increase the seepage force during prolonged rainfall. In Bhubaneswari OCP mines, gully erosion are due to surficial flow which play a significant role in dump face modification as well as inititate and migrate the tension cracks in the upper part of unconsolidated dumps. One of the most important triggering factor in situations of heavy to moderate rainfall is infiltration of water into slope forming material which consequently increases the pore pressure within the sediment and ultimately reduces the factor of safety of the slope forming material and possibly causing failure. The average rainfall in Talcher area is nearly 700mm which affect the different slope inside the mining area (Fig. 11). In the year 2014, the maximum rainfall precipitated in July and resulted in the major slope failure in the area under investigation.
for dump failure. Groundwater flow condition plays a critical role on the stability of dump slope. Heavy monsoonal rainfall resulting raise in groundwater table is often believed to be the cause of dump slope instability (Yellishetty et al. 2010). Rainfall percolating through the weathered soil has triggered slope failures in circular shape due to loss of cohesion. The surface water flow also affect the dump stability as it increase the seepage force during prolonged rainfall. In Bhubaneswari OCP mines, gully erosion are due to surficial flow which play a significant role in dump face modification as well as inititate and migrate the tension cracks in the upper part of unconsolidated dumps. One of the most important triggering factor in situations of heavy to moderate rainfall is infiltration of water into slope forming material which consequently increases the pore pressure within the sediment and ultimately reduces the factor of safety of the slope forming material and possibly causing failure. The average rainfall in Talcher area is nearly 700mm which affect the different slope inside the mining area (Fig. 11). In the year 2014, the maximum rainfall precipitated in July and resulted in the major slope failure in the area under investigation.
Fig.11. Rainfall variation in Talcher area. (Source: http:// www.odisha.gov.in/disaster/src/RAINFALL/RAINFALL1/ RAINFALL.html) and Generalised Limit Equilibrium (GLE) method. Among these methods Bishop simplified method, Janbu method, GLE and Morgenstern-Price method are popular because factor of safety value can be quickly calculated for most of the slip surfaces (Abramson et al. 2002).
Fig.11. Rainfall variation in Talcher area. (Source: http:// www.odisha.gov.in/disaster/src/RAINFALL/RAINFALL1/ RAINFALL.html) and Generalised Limit Equilibrium (GLE) method. Among these methods Bishop simplified method, Janbu method, GLE and Morgenstern-Price method are popular because factor of safety value can be quickly calculated for most of the slip surfaces (Abramson et al. 2002).
Table 3. Geomechanical properties used as input parameters respectively. Analysis exhibits that the slope is critically stable. Dump location 3: This is a part of external dump slope
Table 3. Geomechanical properties used as input parameters respectively. Analysis exhibits that the slope is critically stable. Dump location 3: This is a part of external dump slope
shear stress along the slip surface vary with the progressive failure. Here in both the LE method, dump | shows the highest shear stress values with smooth parabolic trend owing to large amount of overburden with loose material. Fig. 17. Geometry of the model for Location 2
shear stress along the slip surface vary with the progressive failure. Here in both the LE method, dump | shows the highest shear stress values with smooth parabolic trend owing to large amount of overburden with loose material. Fig. 17. Geometry of the model for Location 2
the varying slope angle and it has most sharp decrement in FoS at steeper slope angle. The trend observed by both the methods is more likely similar with a difference of 0.09 %.
the varying slope angle and it has most sharp decrement in FoS at steeper slope angle. The trend observed by both the methods is more likely similar with a difference of 0.09 %.
Fig.22. Geometry of the model for Location 3. reduce the pore-water pressure, which will further improve the FoS. The height and slope angle of the dump slope has to be managed to reduce the slope failure. The proper dump management is require for suitable site selection and must
Fig.22. Geometry of the model for Location 3. reduce the pore-water pressure, which will further improve the FoS. The height and slope angle of the dump slope has to be managed to reduce the slope failure. The proper dump management is require for suitable site selection and must
management is require for suitable site selection and must
management is require for suitable site selection and must
ensure that there is no disturbance below the slope. The grass and tree reduce the stress concentration near the surface compare to barren slope (Chaulya et al. 2000), and implementation of bioengineering can also be used to stabilize the mine waste dump (Jian-long et al. 2005).
ensure that there is no disturbance below the slope. The grass and tree reduce the stress concentration near the surface compare to barren slope (Chaulya et al. 2000), and implementation of bioengineering can also be used to stabilize the mine waste dump (Jian-long et al. 2005).
Fig.29. FoS vs. slope height of different dump slopes
Fig.29. FoS vs. slope height of different dump slopes
Fig.28. FoS vs. slope angles of different dump slopes
Fig.28. FoS vs. slope angles of different dump slopes
Related topics:
Mining EngineeringGeologyGeotechnical EngineeringCoal Mine
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