Stability of the slopes is a very important factor in the work related to the excavation and hoarding of soil, rocks and excavation materials, as it concerns the issue of human safety (workers), the safety of equipment and the smooth production. This situation is related to being found in various types of work, for example in road construction, dams, canal excavation, excavation for construction, mining and others.
In mining operations this slope stability problem will be found in open-pit mine excavations, dams for working water reserves, tailing disposal and stockyards. If the slopes formed as a result of the pit slope process or which are the supporting means of mining operations (such as dams and roads) are unstable, it will interfere with production activities.
From the above description, it can be understood that the analysis of the stability of the slopes is an important part to prevent disruption to the smooth production and the ons of fatal disasters. In an undisturbed (natural) state, the soil or rocks are generally in a balanced state against the styles arising from the inside. If for example due to a change in balance due to removal, decline, excavation, hoarding, erosion or other activity, then the soil or rocks will strive to achieve a new state naturally. This is usually the process of degradation or load reduction, especially in the form of avalanches or other movements until a new equilibrium is achieved. On the ground or rocks in an undisturbed state (naturally) have worked vertical, horizontal voltages and water pressure from pores. The three above have an important role to play in shaping slope stability.
While the soil or rocks themselves have certain original physical properties, such as angle of internal friction, the cohesion force and weight of the contents are also very instrumental in determining the strength of the soil and which also affect the stability of the slope. Therefore in an effort to conduct a stability analysis of the slopes should be known with certainty the voltage system that works on the soil or rocks as well as its original physical properties. With that knowledge and data can then be done analysis of the behavior of the soil or rocks if excavated or "disturbed". After that, it can be determined the geometry of the allowed slopes or apply other ways that can help the slope become stable and steady.
In determining the stability or stability of the slope is known as safety factor which is a comparison between forces that withstand movement against the forces that move the soil is considered stable, when formulated as follows:
Security factor (F) = restraint force / drive force
Where to
state : • F > 1.0 : slopes in a steady state
• F =
1.0 : slopes in a state of seimbnag, and ready for avalanche • F < 1.0 : unsteady slopes
state : • F > 1.0 : slopes in a steady state
• F =
1.0 : slopes in a state of seimbnag, and ready for avalanche • F < 1.0 : unsteady slopes
So in analyzing the stability of the slope will always be related to the calculation to know the number of safety factors of the slope. There are several factors that affect the
stability of
the slope, among others: • The spread of rocks Spread and diversity of rock types is strongly related to the stability of the slope, this is due to the strength, physical and technical properties of a type of rock in contrast to other rocks. The statement of rock types will result in an error of analysis results. For example: the slope of the slope consisting of sand will certainly be different from the slope consisting of clay or its mixture.
• Geological
structure Geological structure that affects the stability of slopes and it is worth noting in the analysis are regional and local structures. This structure includes sesar, stocky, field coating, sinklin and antiklin, misal alignment, liniasi, etc. This structure greatly affects the strength of the rock because it is generally a weak field of the rock, and is a place of water spilling that speeds up the weathering process.
• Morphology The
morphological state of an area will greatly affect the stability of the slopes in the area. Morphology consisting of the physical state, characteristics and shape of the earth's surface, greatly determines the rate of erosion and precipitation that occurs, determines the direction of the flow of surface water as well as groundwater and the process of weathering rocks.
•
Climate affects the temperature and amount of rain, so it also affects the weathering process. Hot, humid tropics with high rainfall will cause the rock weathering process much faster than sub-tropical areas. Therefore the thickness of the soil in the tropics is thicker and the strength is lower than the fresh rocks.
• Weathering
level Weathering levels affect the original properties of rocks, e.g. cohesion numbers, the size of deep shear angles, fill weights, etc. The higher the weathering rate, the more the strength of the rocks will decrease.
• Human work
stability of
the slope, among others: • The spread of rocks Spread and diversity of rock types is strongly related to the stability of the slope, this is due to the strength, physical and technical properties of a type of rock in contrast to other rocks. The statement of rock types will result in an error of analysis results. For example: the slope of the slope consisting of sand will certainly be different from the slope consisting of clay or its mixture.
• Geological
structure Geological structure that affects the stability of slopes and it is worth noting in the analysis are regional and local structures. This structure includes sesar, stocky, field coating, sinklin and antiklin, misal alignment, liniasi, etc. This structure greatly affects the strength of the rock because it is generally a weak field of the rock, and is a place of water spilling that speeds up the weathering process.
• Morphology The
morphological state of an area will greatly affect the stability of the slopes in the area. Morphology consisting of the physical state, characteristics and shape of the earth's surface, greatly determines the rate of erosion and precipitation that occurs, determines the direction of the flow of surface water as well as groundwater and the process of weathering rocks.
•
Climate affects the temperature and amount of rain, so it also affects the weathering process. Hot, humid tropics with high rainfall will cause the rock weathering process much faster than sub-tropical areas. Therefore the thickness of the soil in the tropics is thicker and the strength is lower than the fresh rocks.
• Weathering
level Weathering levels affect the original properties of rocks, e.g. cohesion numbers, the size of deep shear angles, fill weights, etc. The higher the weathering rate, the more the strength of the rocks will decrease.
• Human work
In addition to natural factors, humans also provide a small amount of support. For example, a slope that was initially steady, because humans felled protective trees, bad soil treatment, bad waterways, excavations/ mines, and others caused the slopes to become usteady, making erosion and avalanches easy.
Basically avalanches will occur for two reasons, namely rising shear stress and decreased shear strenght. The factors that can increase
shear voltage are: • Reduction of lateral buffering, among others due to erosion, earlier avalanches that resulted in new slopes and human activities.
• Voltage increase, in part due to increased load, crushing water pressure, and buildup.
• Dynamic force, caused by earthquakes and other vibrations.
• Regional lifting or decline, caused by the movement of the formation of mountains and changes in the angle of slope slope.
• Removal of buffers, caused by cutting cliffs by rivers, weathering and erosion below the surface, mining activities and tunnels, reduced/destroyed material at the base.
• Lateral voltage, caused by the absence of water in the recess as well as water freezing, inflating of the clay layer and displacement of residual voltage.
shear voltage are: • Reduction of lateral buffering, among others due to erosion, earlier avalanches that resulted in new slopes and human activities.
• Voltage increase, in part due to increased load, crushing water pressure, and buildup.
• Dynamic force, caused by earthquakes and other vibrations.
• Regional lifting or decline, caused by the movement of the formation of mountains and changes in the angle of slope slope.
• Removal of buffers, caused by cutting cliffs by rivers, weathering and erosion below the surface, mining activities and tunnels, reduced/destroyed material at the base.
• Lateral voltage, caused by the absence of water in the recess as well as water freezing, inflating of the clay layer and displacement of residual voltage.
While the factors that reduce
the shear strength are: • The initial state or hue, it has been low from the beginning due to the composition, texture, structure and geometry of the slope.
• Changes due to weathering and physical chemical reactions, which cause the positent clay to become soft, granular rock disinteggration,
decreased cohesion, bubbling of the clay layer, dissolving of rock spraying material • Change in force between granules due to the influence of water content and pore water pressure.
• Structural changes, such as the formation of damage to clay found on cliffs / slopes.
the shear strength are: • The initial state or hue, it has been low from the beginning due to the composition, texture, structure and geometry of the slope.
• Changes due to weathering and physical chemical reactions, which cause the positent clay to become soft, granular rock disinteggration,
decreased cohesion, bubbling of the clay layer, dissolving of rock spraying material • Change in force between granules due to the influence of water content and pore water pressure.
• Structural changes, such as the formation of damage to clay found on cliffs / slopes.
Bench Dimension
Before knowing some opinions about the dimensions of the level, please know the term at the level as seen below. In the determination of gometry level,
several things considered,
among others:
o Daily and
annual production goals o Mechanical tool size used o In accordance with ultimate pit slope o In accordance with slope stability criteria
several things considered,
among others:
o Daily and
annual production goals o Mechanical tool size used o In accordance with ultimate pit slope o In accordance with slope stability criteria
Elemen-elemen suatu jenjang terdiri dari tinggi, lebar dan kemiringan yang penentuan dimensinya dipengaruhi oleh:
(1) alat-alat berat yang dipakai (terutama alat gali dan angkut)
(2) kondisi geologi
(3) sifat fisik batuan
(4) selektifitas pemisahan yang diharapkan antara bijih dan buangan
(5) laju produksi
(6) iklim.
Tinggi jenjang adalah jarak vertikal diantara level horisontal pada pit; lebar jenjang adalah jarak horisontal lantai tempat di mana seluruh aktifitas penggalian, pemuatan dan pengeboran-peledakan dilaksanakan; dan kemiringan jenjang adalah sudut lereng jenjang. Batas ketinggian jenjang diupayakan sesuai dertgan tipe alat muat yang dipakai agar bagian puncaknya terjangkau oleh boom alat muat.
Disamping itu batas ketinggian jenjang pun harus mempertimbangkan aspek kestabilan lereng, yaitu tidak longsor karena getaran peledakan atau akibat hujan. Tinggi pada tambang terbuka dan quarry batu andesit dan granit sekitar 15 m, sedangkan pada tambang uranium hanya sekitar 1,0 m.
Kemiringan dinding jenjang merupakan salah satu faktor yang mempengaruhi ukuran dan bentuk pit serta luas areal pit. Kemiringan lereng jenjang juga akan membantu penentuan jumlah buangan yang harus diangkat untuk mendapatkan bijih. Telah disinggung sebelumnya bahwa lereng jenjang harus stabil selama aktifitas penggailan berlangsung, oleh sebab itu perlu dilakukan analisis kestabilan lereng diseluruh areal tambang (pit). Kekuatan batuan, patahan, retakan-retakan, kandungan air tanah dan informasi geologi lainnya adalah faktor kunci untuk menganalisis lereng tambang. Akibat dari perbedaan karakteristik batuan dan informasi geologi, maka tidak heran apabila di dalam wilayah penambangan akan terjadi kemiringan lereng yang berbeda. Kemiringan dinding permuka kerja (individual slope) pada tambang bijih dan quarry batuan kompak berkisar antara 720 – 850. Penentuan lebar jenjang akan dipengaruhi oleh laju produksi yang diinginkan, dimensi serta jumlah alat angkut dan alat muat, aktifitas pengeboran-peledakan dan kondisi geologi di sekitar pit.
Tidak ada rumus baku untuk menentukan lebar jenjang; namun, beberapa parameter penting di bawah ini harus dipertimbangkan, meliputi:
Ø radius manuver alat angkut saat akan dimuat material oleh alat muat, Rm:
Ø cukup leluasa untuk berpapasan minimal dua alat angkut, 2 Lt +c ;
Ø lebar maksimum tumpukan hasil peledakan (muckpile), Mp ;
Ø lebar areal yang akan dibor, Ld.
Ø radius manuver alat angkut saat akan dimuat material oleh alat muat, Rm:
Ø cukup leluasa untuk berpapasan minimal dua alat angkut, 2 Lt +c ;
Ø lebar maksimum tumpukan hasil peledakan (muckpile), Mp ;
Ø lebar areal yang akan dibor, Ld.
Berdasarkan parameter di atas, maka dapat dibuat rumus empiris lebar jenjang (LB) sebagai berikut:
LB = Rm+(2Lt+c)+Mp+Ld
Parameter Lt adalah lebar sebuah truck maksimum dan c adalah konstanta yang tergantung pada jarak dua truck yang aman ketika berpapasan, yaitu antara 5,0 m sampai 10 m.
Beberapa pihak yang mengeluarkan pendapat mengenai dimensi jenjang, antara lain :
- Head Quarter of US Army (Pit sand Quarry Technical Bulletin No 5-352)
- Lew is (Elements of Mining)
- L. Shevyakov (Mining of Mineral Deposits)
- Melinkov dan Chevnokov (Safety in Open Cast Mining)
- Popov (The Working of Mineral Deposit)
- Young (Elements of Mining)
- E. P. Pfeider (Surface Mining)
- Head Quarter of US Army (Pit sand Quarry Technical Bulletin No 5-352)
- Lew is (Elements of Mining)
- L. Shevyakov (Mining of Mineral Deposits)
- Melinkov dan Chevnokov (Safety in Open Cast Mining)
- Popov (The Working of Mineral Deposit)
- Young (Elements of Mining)
- E. P. Pfeider (Surface Mining)
- Head Quarter of US Army (Pit sand Quarry Technical Bulletin No 5-352)
Wmin = Y +Wt + Ls + G + Wb
dimana :
W min : Lebar jenjang minimum (m)
Y : Lebar yang disediakan untuk pengeboran (m)
Wt : Lebar yang disediakan untuk alat -alat (m)
Ls : Panjang power shovel tanpa boom (m)
G : Radius lantai kerja yang terpotong oleh shovel (m)
Wb : Lebar untuk broken material (m)
W min : Lebar jenjang minimum (m)
Y : Lebar yang disediakan untuk pengeboran (m)
Wt : Lebar yang disediakan untuk alat -alat (m)
Ls : Panjang power shovel tanpa boom (m)
G : Radius lantai kerja yang terpotong oleh shovel (m)
Wb : Lebar untuk broken material (m)
- Lewis (Elements of Mining)
Tinggi jenjang sebagai berikut :
o Untuk hidraulicking yang baik adalah 20 ft dan maksimum 60 ft
o Untuk dredging kedalaman ideal antara 50 ft – 80 ft, tetapi ada yang sampai 130 m
o Untuk Open-cut antara 12 ft – 75 ft; yang baik 30 ft. Sedangkan untuk tambang bijih dapat mencapai 225 ft. Lebar jenjang disesuaikan dengan loading track, daerah operasi power shovel serta untuk peledakan. Lebarnya antara 20 ft – 75 ft, umumnya 50 ft dan idealnya 30 ft .
o Untuk hidraulicking yang baik adalah 20 ft dan maksimum 60 ft
o Untuk dredging kedalaman ideal antara 50 ft – 80 ft, tetapi ada yang sampai 130 m
o Untuk Open-cut antara 12 ft – 75 ft; yang baik 30 ft. Sedangkan untuk tambang bijih dapat mencapai 225 ft. Lebar jenjang disesuaikan dengan loading track, daerah operasi power shovel serta untuk peledakan. Lebarnya antara 20 ft – 75 ft, umumnya 50 ft dan idealnya 30 ft .
- L. Shevyakov (Mining of Mineral Deposits)
Lebar jenjang tergantung pada metode penggalian dan kekerasan bahan galian yang ditambang.
o Untuk Material Lunak
B = (1,00 s.d 1,50 ) Ro + L + L1 + L2
Where
: B : Width
level (m) Ro :
Digging radius of the loading device (m)
L : Distance ant ara side level with rail (3
- 4 m) L1 : Width of the lorry (1.75 – 3.00 m) L2 : Distance to keep from landslide (m)
: B : Width
level (m) Ro :
Digging radius of the loading device (m)
L : Distance ant ara side level with rail (3
- 4 m) L1 : Width of the lorry (1.75 – 3.00 m) L2 : Distance to keep from landslide (m)
o For Hard Materials
B = N + L + L1 + L2
where
: B : Width
level (m) N : Width required for broken material (m)
: B : Width
level (m) N : Width required for broken material (m)
Here is not provided width for digging tool /
load, because it is considered a loading tool works besides broken material- Melinkov and Chevnokov (Safety in Open Cast Mining)
o For soft strata
load, because it is considered a loading tool works besides broken material- Melinkov and Chevnokov (Safety in Open Cast Mining)
o For soft strata
B = 2R + C + C1 + L
where
: B : Width
level (m) R :
Digging radius of loading tool (m)
C : Side distance of level or broken material
to the middle line of rail (m) L : width provided for safety factor, usually as large as dump-truck (m) o For soft layer (soft strata)
: B : Width
level (m) R :
Digging radius of loading tool (m)
C : Side distance of level or broken material
to the middle line of rail (m) L : width provided for safety factor, usually as large as dump-truck (m) o For soft layer (soft strata)
B = a + C + C1 + L + A
where
: B : Width
level (m) a
: Width for broken material (m) A : Cutting width pert ama (m)
-Popov (The Working of Mineral Deposit)
: B : Width
level (m) a
: Width for broken material (m) A : Cutting width pert ama (m)
-Popov (The Working of Mineral Deposit)
A. Its height and slope
i) The slope of the level depends on the water bladder of the excavation material; when relatively dry usually allows a large incline.
ii) Generally the level height ranges from 12 – 15 m with a slope:
ii) Generally the level height ranges from 12 – 15 m with a slope:
- for frozen rocks : 70o
– 80o - for sedimentary
rocks : 50o – 60o - for
ledge rocks and dry sand : 40o – 50o - for argilaceous rocks : 35o – 45o
– 80o - for sedimentary
rocks : 50o – 60o - for
ledge rocks and dry sand : 40o – 50o - for argilaceous rocks : 35o – 45o
B. Level width
The width of the level is between 40 – 60 m, usually also made between 80 – 100 m if using multi row bore-hole. Minimum width for hard rocks:
Vr = A + C + C1 + L + B
Where
: Vr : Minimum
level width (m) A
: Width for broken material (m)
C : Heap side
distance to the center side of the rail
(m) C1 : Half width of the
lorry ( m) B : Blown sediment width (6 - 12 m) L : Width provided to guarantee sediment extraction at the level below- Young (Elements of Mining)
: Vr : Minimum
level width (m) A
: Width for broken material (m)
C : Heap side
distance to the center side of the rail
(m) C1 : Half width of the
lorry ( m) B : Blown sediment width (6 - 12 m) L : Width provided to guarantee sediment extraction at the level below- Young (Elements of Mining)
o High
level - for iron ore mining :
20 - 40 ft -
for copper ore mining : 30 - 70 ft - for lime st on e : up to 200 ft
level - for iron ore mining :
20 - 40 ft -
for copper ore mining : 30 - 70 ft - for lime st on e : up to 200 ft
o Width: 50 – 250 ft
o Tilt level : 45o
– 65o- E. P. Pfeider (Surface Mining)
– 65o- E. P. Pfeider (Surface Mining)
L = Lm + SF x
where
: L : Height
level (m) Lm : Maximum
cutting height of tool-load (m) SF : Swell Factor (m)
x = 0.33 for corner cut
= 0.50 for box cut way
: L : Height
level (m) Lm : Maximum
cutting height of tool-load (m) SF : Swell Factor (m)
x = 0.33 for corner cut
= 0.50 for box cut way
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