Effect of pillar size change on stress distribution in metalliferous mines

Yeraltı metal madenciliğinde cevher kazanımı sırasında tavanın etkili bir şeklide desteklenmesi ve güvenliğin sağlanması amacıyla üretim alanında cevherlerden oluşan topuklar bırakılmaktadır. Topuk boyutlarının optimum seviyelerde olması cevher kazanımı açısından önemli hale gelmektedir. Gereğinden fazla boyutlarda bırakılacak olan topuk cevher kaybına sebebiyet verecek ve işletmeyi ekonomik yönden olumsuz etkileyecektir. Ayrıca, olması gerekenden az boyutlarda bırakılan topuk ise çalışılan bölgeyi iş güvenliği açısından daha tehlikeli hale getirecektir. Yapılan çalışmada, Phase2D sayısal modelleme programında farklı boyutlarda modellenmiş olan topuklar etrafında meydana gelen gerilmeler hesaplanmış ve topuklar etrafında oluşan gerilme dağılımı dikkate alınarak optimum topuk boyutları önerilmiştir.For the purpose of effectively supporting the roof and ensuring safety during ore recovery in underground metal mining, pillars composed of ores are left in production area. Optimum pillar sizes are becoming important for ore recovery. The pillar that will be left in more than necessary dimensions will cause loss of ore and will negatively affect the company economically. In addition, the pillar that is left in smaller sizes than it should be will make the working area more dangerous in terms of work safety. In the study, stresses occurring around pillars modeled in different sizes are calculated in Phase2D numerical modeling program and optimum pillar sizes are proposed considering the stress distribution that are occured surround of pillars

Truck Selection with the Fuzzy-WSM Method in Transportation Systems of Open Pit Mines

Open pit mines gain width and become more complicated as they are deeper today, and it is inevitable to carry the produced material with a truck transportation system. Therefore, in large-scale businesses, truck selection has great importance for the transportation costs to be sustainable. This study investigates the main factors and corresponding criteria influential in selection of trucks, which are the most frequent used means of transportation in open pit mines. Analytic hierarchy process and fuzzy weighted sum model are employed to solve the selection problem. Six different truck types and 20 selection criteria are considered. As a result of technical analysis, most suitable trucks are found

Impact of opioid-free analgesia on pain severity and patient satisfaction after discharge from surgery: multispecialty, prospective cohort study in 25 countries

Background: Balancing opioid stewardship and the need for adequate analgesia following discharge after surgery is challenging. This study aimed to compare the outcomes for patients discharged with opioid versus opioid-free analgesia after common surgical procedures.Methods: This international, multicentre, prospective cohort study collected data from patients undergoing common acute and elective general surgical, urological, gynaecological, and orthopaedic procedures. The primary outcomes were patient-reported time in severe pain measured on a numerical analogue scale from 0 to 100% and patient-reported satisfaction with pain relief during the first week following discharge. Data were collected by in-hospital chart review and patient telephone interview 1 week after discharge.Results: The study recruited 4273 patients from 144 centres in 25 countries; 1311 patients (30.7%) were prescribed opioid analgesia at discharge. Patients reported being in severe pain for 10 (i.q.r. 1-30)% of the first week after discharge and rated satisfaction with analgesia as 90 (i.q.r. 80-100) of 100. After adjustment for confounders, opioid analgesia on discharge was independently associated with increased pain severity (risk ratio 1.52, 95% c.i. 1.31 to 1.76; P < 0.001) and re-presentation to healthcare providers owing to side-effects of medication (OR 2.38, 95% c.i. 1.36 to 4.17; P = 0.004), but not with satisfaction with analgesia (beta coefficient 0.92, 95% c.i. -1.52 to 3.36; P = 0.468) compared with opioid-free analgesia. Although opioid prescribing varied greatly between high-income and low- and middle-income countries, patient-reported outcomes did not.Conclusion: Opioid analgesia prescription on surgical discharge is associated with a higher risk of re-presentation owing to side-effects of medication and increased patient-reported pain, but not with changes in patient-reported satisfaction. Opioid-free discharge analgesia should be adopted routinely

Examining of rock drilling properties in underground metal mine excavation

In underground metal mines, drilling and blasting is widely used production method. Drilling holes is especially a time consuming operation. The aim of this study is to examine and analyze drilling operation and its duration in underground ore and dead rock. Drillability experiments are carried out on samples taken from the field. In core sampling two different types of core samples are taken whether it is parallel or perpendicular to ore bedding and dead rock. Results of drillability experiments are compared between the two types of core samples. DRI values are found to be 51 and 47 for the parallel and perpendicular core samples to ore bedding, respectively. DRI values for the parallel and perpendicular core samples to dead rock bedding are found to be 57 and 55 for the, respectively. In addition, graphs of drilling speed and drilling depth belonging to ore and dead rock are analyzed. It is examined that drilling speed increases steadily to maximum point in the first 5sec. and stays stable after that point. Therefore, it is concluded that production galleries and holes which are formed parallel to bedding would increase production efficiency

Disturbance factor effects on the selected geotechnical properties of the discontinuities

Günümüz açık ocak madenciliğinde ocak üretim maliyetinin yaklaşık yüzde otuzu patlatma işlemlerinden kaynaklanmaktadır. Ayrıca patlatma işleminde ve patlatma verimindeki en önemli parametrelerden biri de süreksizliklerdir. Süreksizliklerin devamlılığı ve açıklığı, patlatma verimine doğrudan etki eden unsurlardır. Açık ocaklarda yapılan patlatma işlemlerinden kaya kütlesi içindeki süreksizlikler etkilenmekte ve açıklıkları artmaktadır._x000B_Bu bilgiler doğrultusunda gerçekleştirilen bu çalışmada iki farklı işletmede arazi çalışmaları gerçekleştirilmiş ve arazilerde yapılan patlatma işlemleri sonrasında kaya kütlelerinde meydana gelen örselenmenin, süreksizliklerin açıklığına olan etkileri araştırılmıştır._x000B_Yapılan çalışmalarda, her patlatmaya ait özgül şarj miktarları hesaplanmış ve özgül şarj miktarları ile patlatma işlemi sonrasında süreksizliklerde meydana gelen değişimler arasında bağlantı kurulmaya çalışılmıştır._x000B_Ayrıca, patlatma yapılan aynalardaki süreksizlik aralıkları ve patlatma parametreleri dikkate alınarak patlatmadan sonraki tane yığın boyut dağılımları görüntü analizi yöntemi yardımıyla tanımlanmıştır. The cost of blasting operations is about thirty percentage of all production expenses for open pit mine operations. Discontinuities are one of the most important parameters for blasting operations. The persistency and the aperture of discontinuities are directly affected from the blasting efficiency. Blasting operations in open pit mines affect the discontinuities into the rock mass and change its properties._x000B_In this study, the field studies were computed for two different quarries and the effect of disturbance on discontinuities into the rock mass after blasting operations were studied._x000B_The specific charge for blasting were calculated for every blasting operation and the relationships between specific charge and change of the discontinuity aperture after the blasting operations were studied._x000B_Also particle size distribution were tried to be determined by considering spacing of discontinuities and the blasting parameters by using the image analyzing method

Determination of Most Suitable Working Height of Powered Roof Support Considering Roof Stresses

In order to meet the increasing demand for coal, longwalls having large working heights up to 7.3 m are being operated worlwide. As the working heights increase, the load-bearing capacities of powered roof supports used at such longwalls are to be raised too. From a powered roof support it is expected that it safely bears the roof loads and transmits them to the footwall at different working heights. This article presents the results of numerical analyses on roof stresses at different longwall working heights. In order to determine the most suitable longwall working height, average stress distributions that occur on roof and gob zones are calculated for different longwall working heights. For this purpose, numerical models are built up and the procedure is applied to a real-life underground coal mine. Six distinct longwalls are modeled considering rock mass properties and working heights. In conclusion, the most suitable longwall working height for the mine under study is determined considering stresses occurring on roof strata and the gob zone