Konya Ilgın linyit sahası şev stabilite analizi
Konya Ilgin lignite site slope stability analysis
Yazar: BÜŞRA ERTUĞRUL
Danışman: PROF. DR. SELAMET GÜRBÜZ ERÇELEBİ
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / Maden Mühendisliği Ana Bilim Dalı
Derece: Yüksek Lisans, 2015
Konu: Maden Mühendisliği ve Madencilik = Mining Engineering and Mining

Özet:
Günümüzde gelişen teknoloji ve artan hammadde ihtiyacına bağlı olarak artan üretim kapasiteleri ile birlikte açık işletme derinlikleri artmıştır. Bununla birlikte, artan üretim kapasiteleri ile paralel olarak teknik sınırlar da zorlanmaya başlanmış olup tüm mühendislik sektörlerinde olduğu gibi madencilik sektöründe de tüm çalışmalarda optimizasyon üzerinde durulan en önemli konu haline gelmiştir. Açık maden işletmelerinde, optimizasyon açısından yapılan değerlendirmelerin başında teknik ve ekonomik sınır şartları karşılayacak optimum şev geometrisinin belirlenmesi gelmektedir. Özellikle 20. yüzyılın son çeyreğinde gelişen bilgisayar teknolojisi ve yaygınlaşmaya başlayan şev stabilitesine yönelik paket programlarla birlikte şev stabilite analizleri daha gerçekçi, hassas ve hızlı yapılabilir hale gelmiştir. 
Bu çalışmada, Konya Ilgın Çavuşçu Gölü Havzasının kuzey bölümünde yer alan kömür sahaları ele alınmaktadır. Çalışmaya konu olan sahadaki formasyonlar; Kuvaterner yaşlı güncel birikinti çökeller ile kireçtaşı, Neojen yaşlı kil, killi kireçtaşı ile linyit ve Neojen öncesi yaşlı şist olarak sıralanmaktadır. Bu çalışmanın amacı, söz konusu sahadaki linyit rezervinin üretilebilmesi için teknik ve ekonomik açıdan optimum şev tasarımının belirlenmesidir. Belirtilen amaç doğrultusunda "kısa süreli şevler" olarak adlandırılan kazı şevleri için sismik yüklerin mevcut olmadığı durumlarda"1,30 emniyet katsayısı", sismik yüklerin mevcut olduğu durumlar için ise "1,00 emniyet katsayısı" sınır değer olarak kabul edilmiş olup sonlu elemanlar yöntemi ile analizler yapılmıştır. Analizler, Phase2 programı ile bölgenin 1. derece deprem bölgesi olması ve Çavuşçu Gölü tabanından gelmesi muhtemel sızıntı suları düşünülerek 3 farklı duruma göre 3 farklı analiz seti halinde yapılmıştır. Bu analiz setleri; yer altı suyunun ve sismik yüklerin mevcut olmadığı, yer altı suyunun mevcut olup sismik yüklerin mevcut olmadığı durum ile yer altı suyunun mevcut olmadığı fakat sismik yüklerin mevcut olduğu duruma göre yapılan analizleri içermektedir.
Duraylı şev geometrisinin tasarlanması noktasında; dekapaj miktarı açısından ekonomik ve teknik şartlar göz önünde bulundurularak optimum basamak genişliği yer yer 40 m, yer yer 50 m olarak belirlenirken,optimum basamak yüksekliği ise 15 m olarak belirlenmiştir. Belirlenen şev geometrisine göre genel (nihai) şev açısı değeri ise üretimin farklı dönemleri ve linyit havzasının farklı bölümlerinde 13,70° ile 17,40° arasında değişiklik göstermektedir.Analizlerde kullanılan kesitlerde gözlemlenen formasyonlar; düşük dayanıma sahip birikinti çökel, kireçtaşı-kil-marn, linyit, düşük dayanıma sahip taban kili ve şist şeklinde sıralanmaktadır.Belirlenen şev geometrileri doğrultusunda Phase2 programı ile analizler yapılarak "dayanım faktörü" değerleri ve stabilitenin bozulduğu durumda oluşacak kaymalar için "kayma daireleri" tespit edilmiştir.
Yapılan analizler neticesinde, veri setleri birbirleri ile hem "emniyet katsayıları" hem de "kayma daireleri" yani yorulma yüzeyleri açısından karşılaştırılmıştır. Bu sayede, sahada gerçekleşmesi muhtemel tüm durumlar göz önünde bulundurularak nihai sonuca varılmıştır. Analiz sonuçlarının değerlendirilmesi noktasında, sismik yüklerin mevcut olmadığı durumlarda 1,30 emniyet katsayısı değeri, sismik yüklerin mevcut olduğu durumlarda ise 1,00 emniyet katsayısı değeri sınır değer olarak alınmıştır. Bu bağlamda sonuçlar incelendiğinde; sadece suyun mevcut olduğu analiz setinde elde edilen emniyet katsayısı değerlerinin sınır değer kabul edilen emniyet katsayısı değerlerinden düşük olduğu, suyun mevcut olmadığı diğer iki analiz setinde ise sınır değerin üzerinde olduğu gözlenmiştir. Bu durum; ortamda suyun varlığına bağlı olarak ortaya çıkan hidrostatik basıncın, şevin duruylılığını yitirmesine sebep olduğunu göstermektedir. Buradan yola çıkarak, sahada şev duraylılığının sağlanabilmesi için drenaj çalışmalarıyla yer altı su seviyesinin düşürülmesi gerektiği sonucuna varılmıştır.

Abstract:
Nowadays, world open pit mining gets deeper since the demand of raw material and technology in mining is increased. To cover high demands, open pit mining capacity become higher and the operations related open pit mining has reach its technical limits to fulfill the demands. Thus this optimization has become an important topic in mining activities. One of the most popular topics in open pit optimization is slope stability due to compensate technical and economical limits in open pit mining. Especially in the late 20th century, the slope stability analysis have become realistic, easy and fast together with package computer programming.
Investigation of the rock slopes is vital for the design of many engineering processes such as embankment, earth dams roadside of highways and open pit mines. The engineering solutions to slope instability problems require good understanding of analytical methods, investigative tools and stabilization measures. Slope design made by using appropriate and accurate methods, both improves slope stability and provides the opportunity to work in a safe environment reducing accidents. 
The slope stability analysis of rocks is vital for designing safe slopes in open–pit mines. A proper slope design not only leads to improvements in slope stability and safety but also reduces costs, extends the life of mines and decreases the stripping ratio. There are different methods used to evaluate the slope stability of rocks. The assessment of slope stability in rocks is usually performed by kinematic analysis, limit equilibrium analysis and a rock mass classification system. Kinematic analysis is based on the motion of bodies without consideration of the forces that cause the motion. However, kinematic analysis does not consider the forces acting on a slope or important geotechnical parameters, such as cohesion and unit weight. The other method, known as limit equilibrium analysis, considers shear strength along a failure surface, the effects of pore water pressure and the influence of external forces, such as reinforcing elements or seismic accelerations limit equilibrium analysis is widely used and is a simple method to assess the stability of the slopes, it is often inadequate if the slope fails via complex mechanisms (e.g., discontinuity orientation, progressive weathering, excavation disturbances, etc.) Rock mass classification has been applied successfully in tunneling and underground mining. It should be noted, however, that the use of rock mass classifications developed particularly for underground works may lead to unsatisfactory results when applied to near-surface applications such as rock slopes. This is due to the restrictions of these systems which are not well considered). 
Rock slope failures (plane failure, wedge failure, circular failure, toppling failure and rock falls) mostly depend on various properties of rock mass. Theoretical evaluation on the most of geometric relationships among discontinuities by kinematic method is required for a solution of rock slope stability problems. If any emergency situation about slope failure as a result of kinematic analysis are faced with, the limit equilibrium analysis with potential hazards are investigated. The analysis of the stability of slopes using limit equilibrium methods necessitates determination of the critical slip surface that yields the minimum factor of safety (FS). This is especially important with regard to slope design, where engineers must determine the FS of a given slope in order to invoke remediating measures to stabilize the slope. Traditionally, engineering approaches have approximated the shear surface as circular, and have used a method of slices, such as the Bishop method, to solve equations of force or moment equilibrium. The Limit equilibrium methods are not interested in stress distribution along the slope, below or above the sliding surface and deformation and stress distribution after the mass break occurs. Therefore, the stress and displacement distributions in the slope can be calculated by using numerical methods. 
The majority of slope stability analysis performed in practice still use traditional limit equilibrium approaches involving methods of slices that have remained essentially unchanged for decades. Although limit equilibrium analysis is widely used and is a simple method to assess the stability of the slopes, The analysis of the stability of slopes using limit equilibrium methods necessitates determination of the critical slip surface that yields the minimum factor of safety (FS). Numerical methods solve the governing equation of continuum mechanics based on predefined boundary conditions. The factor of safety is not solved explicitly in numerical methods but can be assessed based on the shear strength reduction (SSR) technique). The finite element method represents a powerful alternative approach for slope stability analysis which is accurate, versatile and requires fewer a priori assumptions, especially, regarding the failure mechanism. Slope failure in the finite element model occurs `naturally' through the zones in which the shear strength of the soil is insuficient to resist the shear stresses.
Practising engineers are often sceptical of the need for such complexity, especially in view of the poor quality of soil property data often available from routine site investigations. Although this scepticism is often warranted, there are certain types of geotechnical problem for which the FE approach offers real benefits. The challenge for an experienced engineer is to know which kind of problem would benefit from a FE treatment and which would not. In general, linear problems such as the prediction of settlements and deformations, the calculation of low quantities due to steady seepage or the study of transient effects due to consolidation are all highly amenable to solution by finite elements. Traditional approaches involving charts, tables or graphical methods will often be adequate for routine problems but the FE approach may be valuable if awkward geometries or material variations are encountered which are not covered by traditional chart solutions. The use of nonlinear analysis in routine geotechnical practice is harder to justify, because there is usually a significant increase in complexity which is more likely to require the help of a modelling specialist. Nonlinear analysis are inherently iterative in nature, because the material properties and/ or the geometry of the problem are themselves a function of the `solution'. Objections to nonlinear analysis on the grounds that they require excessive computational power, however, have been largely overtaken by developments in, and falling costs of, computer hardware. A desktop computer with a standard processor is now capable of performing nonlinear analysis such as those described in this paper in a reasonable time spanÐ?minutes rather than hours or days. Slope stability represents an area of geotechnical analysis in which a nonlinear FE approach offers real benefits over existing methods
In this study, it is taken into consideration that the coal fields in the north area of Konya Ilgın Cavuscu Lake. Subjected materials are listed as quaternary age current accumulation sediments with limestone, Neojen old clay, clayey limestone with lignite and old slope before the old Neojen. The purpose of this study is the determination of the optimum slope design of the production of the lignite deposit. In accordance with this purpose, analysis were done finite elements method. "1,30 safety factor" and "1,00 safety factor" are taken as boundary value for excavation slope that called short term slope. "1,30 safety factor" is not, "1,00 safety factor" is in existance of seismic load. Analysis are made in three different analysis for three different cases with the phase2 program. They are considered the facts that the area is first degree earthquake field and the possibility of the existence of seepage water from the bottom of Cavuscu Lake. These analysis packs includes the analysis that are done according to cases of; both underground water and seismic load are not exist, underground water are exist but seismic load are not exist and underground water are not exist but seismic load is exist. 
It took into considering both economical and technical conditions for the determine of optimum bench parameters to design stabilize slope geometry. So bench height took as 15 m and it's length as 40 m and 50 m. According to the determined slope geometry general slope angle examined between 13,70° and 18,00° bearing in mind both the location of lignite and production schedule. The materials used in sections observed with analysis are following in ordered ; low mechanical strenghtened sediments, limestone – clay – marl, lignite, clay and schist that low mechanical strengthened. Using determined slope geometry the value of safety factor and slip circles specified for the slides may occurin instability using analysis in Phase2 software. 
According to analysis results, data sets are compared with each other in term of both safety factor and also slip circle also know as fatigue surface. Therefore final result is obtained by evaluating all possible field conditions. As estimating analysis results, safety factor value is assumed  as 1,30 in cases which have no seismic load while it is assumed as 1,00 in cases of including seismic load. As a conclusion, safety factor values are in cases where there is water lower than the limit value while they are in order two cases where there is no water more than the limit value. The situation shows that hydrostatic pressure which arise with existance of water caused loss of the sensibility of slope. Consequently, drainage works and level of underground water have to decrease to provide the sensibility of slope.