Abstract MOIL Limited is Schedule - A, Miniratna Category -I, Central Public Sector Enterprise (CPSE) under the administrative control of the Ministry of Steel, Government of India. At present, MOIL operates 10 mines in central India located in the state of Maharashtra and Madhya Pradesh. Expecting 3, rest of the mines is worked through underground methods at shallow 153 m to moderate depth 353 m below the surface. MOIL is producing annually more than 1.2 million tonnes of various grades of manganese ore. All the underground mines are using horizontal cut and fill (HCF) method of stoping or its variant with back filling by hydraulic sand stowing with roof bolt and cable bolt as a pre mining support system. This paper discusses impact of discontinuities on design of mechanized over hand cut and fill method of stoping for manganese ore body of Ukwa mine. The mine has the manganese ore body at an average thickness of 5 m and is highly jointed containing three sets of orthogonal joints. It is dipping 30° – 45° towards N32°W and the ore body has strike length 5000 m. The orientation of discontinuities was the primary factor influencing stability of excavation in the ore body. Kinematics analysis was used for evaluating potential modes of failure due to unfavorably oriented discontinuities. From the analysis it is found that pre mining support of roof bolt and long bolt to be introduced for supporting the entries to the stope and also for reinforcing the stope back during extraction of the slices. The extraction of the crown pillar should be under taken immediately after the completion of the stoping. Just after the filling with sand stowing of the stope, the SDL has to be run. In subsequent runs, the sand gets compacted and its bearing capacity increases. Taking these factors into consideration, a mechanized cut and fill method along with reinforcement plans of the stope has been designed for extraction the ore body up to 5 m thick and 35°–45° inclined. 1. Introduction The Ukwa Mine of MOIL Limited is being worked since 1903. The total lease hold area of the mine is 322.608 Ha, this includes three (3) leases in Ukwa, Lugma, Gudma and Samnapur villages in Tahsil Paraswada, Distt. Balaghat of Madhya Pradesh. Composite Lease Plan of 3 Leases of Ukwa Mine with forest area is shown in figure 1.

Abstract Though ground subsidence is generally associated with softer rock formations, several occurrences of cap rock failure and sink holes have been reported over open stopes of hard rock mines. Lead-zinc mining is being practised using underground stoping methods in the state of Rajasthan in northern part of India. In most of the cases the orebody occurs as steeply pitching deposit, but often some limbs or lenses of the main orebody occur flatly dipping. This makes them prone to sudden collapse, when extracted using open stoping methods at shallow and moderate depth of cover. It is therefore important to design the stoping method to avoid collapse of the surface crown. One such case example of a lead-zinc mine, where the orebody occurs almost flat below private agricultural land and in the vicinity of some important surface structures, is on the spot light. A stoping method and an extraction sequence are designed, using elasto-plastic numerical modelling to control surface subsidence, ensure operational safety and maximise ore recovery. The subsidence control measures adopted include leaving optimally designed post-pillars and back filling of the stoped out areas with cemented rock fill (CRF). About 5% of ore is designed to be left in post-pillars. With side confinement offered by the CRF on to these post-pillars, they shall ensure safety and stability of the surface crown during stoping operations. In addition to these measures cable bolts of 10m length are also used for reinforcement of the stope back and to ensure roof stability during extraction. Several hit and miss attempts using elasto-plastic numerical modelling have been done to arrive at the optimum extraction sequence and positioning of the post-pillars. The height of yield zones predicted from the numerical model is used as the main criterion to optimise the design. A scheme for cap rock monitoring is also devised to ensure ground stability. The designed stoping scheme has been successfully implemented in the mine. 1. Introduction Lead-Zinc deposits of high grade are being mined in the Northern part of India for several centuries using underground stoping methods of mining. Some methods involve backfilling for better ore recovery and ground stability. One of the cheapest form of back filling technique effectively used in some underground mines is the Cemented Rock Fill (CRF) (Stone, 1993). Ground subsidence is mostly associated with soft rock formations and flatly dipping deposits such as coal (Whittaker and Reddish, 1989). However several occurances of subsidence and sink holes have been reported over open stopes of hard rock mines as well (Szwedzicki, 1999, Hutchinson et al., 2002). It is hence important to design a stoping method with backfilling most of the voids prior to mine closure to ensure long-term stability of the surface. In this paper a case example of an underground hard rock mine with a flatly dipping orebody is presented. A stoping method in tandem with CRF backfilling is designed using three-dimensional elasto-plastic numerical modeling so as to ensure ground stability during and after extraction.

Abstract An area consisting of UG2 Spit Reef provided a unique challenge to extract the reserves by means of a safe and feasible mining strategy. The proposed strategy was required to ameliorate the exposure of personnel to geotechnical risk whilst providing a feasible scenario from a cost perspective. The initial full channel mining strategy would extract the reserves at stoping widths in excess of 2.0 m at perceived low levels of risk and low grade. A paradigm shift was required to deviate from this historic method. The proposed mining strategy entailed undercutting the internal waste layer resulting in the extraction of the UG2 reserves at stoping widths of less than 1.2 m at quantified low risk levels and high grade. No successful attempts had previously been recorded where the UG2 Split Reef had been undercut within a highly discontinuous rock mass area such as the Spruitfontein Fault zone. This resistance to change was devolatilized by the introduction of a rigid areal support medium concomitant with several other support unit alterations. This was nevertheless received with negative criticism by a mining team intent on resisting change. The benefit though of extracting the bottom reef portion exclusively, even with inflated support costs resulted in a beneficiated grade (channel grade) to in excess of 6.0 grams per tonne processed versus the 2.6 grams per tonne from the full channel mining extraction strategy. The proposed mining method and support strategy was presented in March of 2015 and implemented in March of 2017. This paper intends to share the findings pertaining to geotechnical design, support performance and design back-analysis from monitoring results. 1. Introduction Lonmin Platinum Marikana operations are situated along the Western limb of the Bushveld Igneous Complex in the North West Province of South Africa. Karee 3 Shaft (K3) is the largest of the 12 shafts on the Lonmin Marikana lease area. The shaft is able to hoist on average 12 400 t of UG2 and Merensky ore per day (285 200 t per month). The shallower reserves of both Merensky and UG2 Reefs have nearly been depleted and what remains (Fig. 1) are the reserves along both the eastern and western boundaries of the shaft as well as the deeper reserves (825 m below surface) along the sub-decline. Both reef bodies dip from South to North on average 11° with the Merensky Reef overlaying the UG2 Reef (145 m separation). The Spruitfontein Fault can be seen along the western boundary of the shaft (Fig. 1). This fault consists of 2 major faults in conjunction with several sympathetic faults and associated jointing concentrated in an area colloquially referred to as the Spruitfontein Fault zone. The western UG2 Reef horizon is also affected by the presence of Iron Rich Ultramafic Pegmatiod (Fig. 1 - IRUP indicated in maroon which is mostly unmined) and Split Reef (indicated in blue). Pothole features (indicated in yellow) that displace the reefs are also prevalent over the entire K3 shaft property along both UG2 and Merensky horizons.

Abstract In order to conduct disaster-prevention inspections without overlooking falling-rock sources, in this paper, we aim to establish a disaster-prevention inspection method using microtopography highlight maps and verify its effectiveness. First, we create the map using the data obtained from a high-density aerial laser. In our study, measurements were carried out using a measurement helicopter loaded with a laser measuring machine capable of irradiating 80,000 to 400,000 points per second. For creating a microtopographical representation, grid data, contour maps, inclination-amount diagrams that calculate the amount of inclination for each grid datum and change the lightness accordingly to express the topography, and wavelet-analysis diagrams that emphasize the change in the unevenness through wavelet analysis, are generally used. However, it is difficult to extract sources of falling rocks, because it is impossible to express the topographic change point between the contour lines in a contour map. It is also difficult to distinguish between ridges and valleys in the inclination-amount diagram because there is no information indicating the height difference. Furthermore, it is difficult to distinguish the microtopography in the wavelet-analysis diagram, because there is no information indicating the height difference or inclination. Therefore, in this study, we created a microtopography highlight map by overlaying 50 cm of grid data, the inclination-amount map, contour diagram, and wavelet-analysis diagram created from the measured laser data. A field survey verified that, by using this map, it was possible to detect a steep cliff of height 2 m or more, which is a possible source of falling rocks. In our study, we were able to extract sources of falling rocks from a microtopography highlight map. 1. Introduction The necessity of tackling falling-rock projects is increasing, especially, because of the recent heavy rains and earthquakes in Japan. In September 2017, a man riding a bike in the Hualien County in East Taiwan was hit by a falling stone and died. To avoid such painful accidents, improvements in countermeasure projects for falling rocks are necessary. In Japan's rock-fall countermeasure projects, visual tools (drawings) such as basic forest maps and aerial photographs are used to investigate slopes and grasp the locations of falling rocks. However, on slopes covered by trees, it is difficult to prepare a plan view by actual measurement. As a background of investigation using these drawings, this is because these can be made relatively easily. However, in the current countermeasure projects, it is difficult to grasp accurately the positions of the falling-rock origins, from the surveys using these drawings. This leads to a decrease in the investigation efficiency, which is caused by poor positioning accuracy during the survey and because of overlooking objects. In addition, there are problems related to the safety of investigators at the time of investigation, because survey routes must be selected using these drawings and reliable research routes cannot be obtained from them. To solve these problems, it is necessary to improve the accuracy of the drawings used for the survey.

Abstract Fault-slip induced by mining activities in underground mines could inflict severe damage to mine openings. In order to estimate the occurrence of fault-slip related seismic events, a better understanding of fault-slip potential in active mining areas is of importance. In the present paper, the variation in fault-slip potential induced by ore extraction in underground mining is examined with a 3D mine-wide model encompassing a steeply dipping tabular orebody at a depth of 1.5km below surface, and in situ stress conditions that are typical of the PreCambrian Shield. The fault is assumed to run parallel to the orebody. Static analysis is first carried out, in which stopes on a given sublevel are sequentially extracted from the center of the orebody in an outward direction. It is shown that when the first stope is extracted, a significant increase in fault-slip potential takes place within 10 m from the stope boundary, beyond which the mining-induced change in fault-slip potential drastically decreases. The area is thus considered a high risk for fault-slip due to the local unclamping effect triggered by stope extraction. As the mining sequence proceeds, a regional unclamping effect takes place and results in additional increase in fault-slip potential at the observation points. The change in fault-slip potential normalized by the shear strength eventually reaches 0.1 at a point 60 m away from the orebody. Thus, for the mining depth and field stress adopted in this study, it can be said that the range between 10 and 60 m away from the orebody represents moderate risk area for fault-slip, whereby the fault slip might be reactivated due to the regional unclamping effect induced by extracting a large volume of the orebody. Beyond this range, it may be assumed that the risk of fault-slip is quite low, and fault-slip could occur only if the stress state of the fault is critical before mining activity begins.

Abstract The geometric parameters of fractures such as orientation, frequency, size, and shape are used in the modeling of a fractured rock mass. One investigation to acquire geological data for setting these parameters is the geological observation of a gallery wall performed based on geologist's traditional techniques. However, it is necessary to reduce the work volume associated with geological observations of gallery walls because numerous geological observations must be conducted during construction of an underground facility for radioactive waste disposal. To reduce the differences in data quality attributable to geologist's individual skills, it is also necessary to provide a method to acquire objective data that are unaffected by a geologist's subjectivity. Three-dimensional laser scanning (3DLS), which can acquire point clouds indicating the gallery wall surface shape, is useful as a means for achieving these goals. To develop methods of geological observation applying 3DLS, acquisition of geometric data of fractures distributed on the gallery wall has been conducted using 3DLS data while clarifying the geological observation data necessary for modeling of a fractured rock mass. The acquired geometric data of fractures were compared with data acquired by a geologist. Consequently, the fractures were extracted by visible reading of images generated from 3DLS data, and a trace map was generated as geometric data. Strike/dip data of fractures were also acquired. The results confirmed that the geometric data of fractures derived from 3DLS data reached levels comparable to data acquired by a geologist.

ABSTRACT The paper discusses preliminary study on the effect of underground mining on large open pit slope stability in Mae Moh coalfield in Thailand. Mae Moh mine is currently operated as open pit mine and it is the largest open pit coal mine in Thailand. In the near future, however, the final pit limit of the mine will be reached and underground mining will be developed from the final highwall in the depth of 400–600 from the surface. However, due to the adverse geological and geotechnical conditions, such as weak mechanical properties of rock, extra-thickness (20–30 m) of coal seams, and huge final pit slope, various studies for underground mine are being carried out at the present. In this study, it was investigated for appropriate distance between open pit wall and underground mine, response of pit slope in different extent of rib pillars, which is measured horizontally minimum distance from the open pit wall to underground mine, and panels, and different mining height, and the interaction between open pit slope and underground working. The investigation was conducted by means of numerical techniques using three dimensional finite difference code FLAC3D.

ABSTRACT Difficult geo-mining conditions of a deep seated coal pillars limit the scope of conventional semi-mechanised depillaring process, mainly due to their slow rate of extraction. Application of a fully mechanized depillaring process has resulted faster rate of extraction resulting improvement in safety along with production and productivity of the depillaring faces. Out of six mechanized depillaring practices in India, the three successful ones of Anjan Hill, Jhanjra and Pinoura Mines do not belong to deep cover (<200m). While the Tandsi depillaring is practiced at nearly 260m depth of cover and achieved intermediate results. The deepest practiced mechanised depillaring panel in the county is CMP-1of VK7 at 377m of cover. This depillaring encountered massive collapse (before main fall), which adversely affected the pace of mechanisation for pillar extraction operation at higher depth in the country. Actual cause of the problem is still being investigated and is found difficult to be concluded. However, as per core analysis results, a good understanding of the nature of overlying strata might have guided the approach for a better pattern of the pillar extraction and the chance of failure might have been arrested. After realizing this fact, a depillaring operation in the neighboring panel 26 of the mine was successfully conducted. Here, the menace of dynamic loading due to competent overlying strata could successfully be encountered through management of the natural support only. The sixth mechanised depillaring face is successfully being practiced at GDK 11 Incline at around 310m of cover. Again, here application of available knowledge of the site conditions helped in successful completion of mechanised depillaring operation in couple of panels. Field investigations through underground instrumentation and monitoring showed distinct natures and amount of stress re-distribution for shallow and deep cover of the depillaring. The prominence of periodic nature of face loading at shallow cover got reduced during depillaring of a deep coal seam. Pillars around extraction line encountered, almost, continuous loading after first major fall during pillar extraction from deep seated coal seams.

Abstract: This work introduces the coastal geo-engineering issues for a suitable selection and geomaterial characterisation of quarries. The development of the research had two main phases: the field survey, applied cartography and inspection of maritime structures and the geological and geotechnical quarry assessment. This study reports results from the second phase which comprises the evaluation of quarries and the identification of potential areas for the extraction of armourstone with quality and availability to supply maritime structures. It was proposed a zoning of the NW Portugal region and taken into account some features like the land use, urban and settlement plans, geological setting, geotechnical and geomechanical description/typification of the rock masses. 459 quarries were identified, georeferenced and distributed in a total area of 14.010km2. More than 200 sites were selected, characterised and included in the GIS database project with interactive support (e.g. hyperlinks for the datasheets, photos or essential information). A total area of 4,1% was calculated, including relevant geological conditions and comprising existent quarries (active/inactive) or new places (suitable or predictable areas). A multidisciplinary perspective must be adopted providing a cost-effective method useful to the incorporation of important concepts (durability and integrity) in geo-monitoring coastal plans and highlighting GIS coastal projects. 1. INTRODUCTION 1.1 Importance of coastal geo-engineering in geomaterial characterisation Presently, concepts in geotechnical and geo-engineering fields are important for rock characterisation and subject of interest by many researchers ([1]). For the design and/or maintenance of coastal defence works the application of analysis methods and technologies related with these domains, are essential (e.g., [2]; [3]; [4]). From the geoengineering point of view, and within a scientific context, impacts caused by the construction of large structures and incorrect land use along the coastal areas, require comprehensive geological, geomechanical studies and engineering solutions for their mitigation. The coastal zone is considered highly dynamic and spatially variable ([5]) and therefore, coastal protection structures are important features in this kind of environment to take into account during a successful coastal maintenance program or management strategy. During the coastal structure's life it is necessary maintenance and repair works, hence, natural and durable rock is one of the main geomaterials employed in maritime works. The definition of geomaterial is: "processed or unprocessed soils, rocks or minerals used in the construction of buildings or structures, including man-made construction materials manufactured from soils, rocks or minerals" ([6]; [7]). This category of rock materials used in coastal defence works are subject to environmental conditions which differ, both in severity and type, from those encountered in other situations. Design requirements also include elements specific to coastal engineering structures and both these aspects must be given due consideration in the selection and specification of the rock. The two most important groups of properties of rock for use in coastal engineering are the geometric properties of shape, size and grading and the physical properties which include density and factors relating to mechanical strength, resistance to abrasion, porosity and durability ([7]).

Abstract: The study of structural lineaments is important for mineral exploration, geotectonic and geotechnical studies, flow and contaminant transport and for the mitigation of geologic hazards. This work deals with automatic extraction of lineaments from satellite imageries of different spatial resolutions as well as the analysis of these extracted lineaments. Wadi Bani Malik area located to the east of Jeddah city on the Red Sea coastal plain is chosen for this study. Six types of digital satellite imagery data were used, these are: Satellite imagery of low spatial resolution (LSR) including Landsat MSS of 80 m resolution, Landsat TM of 30 m resolution and Landsat TM of 25 m resolution; Satellite imagery of moderate spatial resolution (MSR) including Landsat ETM+ panchromatic of 15 m resolution and SPOT panchromatic of 10 m resolution; Satellite imagery of high spatial resolution (HSR) including the Indian Remote Sensing satellite IRS data of 5 m resolution. As expected, the analysis of the extracted lineaments from different data sets shows that the imagery data of HSR of the Indian IRS data gives the highest frequency of the extracted structural lineaments (N=3235), while the imagery data of LSR of the Landsat MSS data gives the lowest frequency of the extracted lineaments (N=89). The imagery data of MSR gives moderate frequency (N=1643) in average. It is recommended to use the imagery data of HSR and MSR for the extraction of structural lineaments for detailed and regional studies, respectively. The imagery data of LSR is not recommended for such studies; accordingly, it is not useful in the analyses of lineaments for geological purposes. INTRODUCTION Lineaments are defined as "mappable, simple or composite linear features of a surface, whose parts are aligned in a rectilinear or slightly curvilinear relationship and which differs distinctly from the pattern of adjacent features and presumably reflect a subsurface phenomenon" [1]. Extraction of lineaments from satellite imagery is important for many purposes such as geological mapping and mineral explorations [2] and seismic and landslide risk assessment [3]. Lineaments may reflect surfaces of discontinuity in the rocks or may reflect a geological structures or topographic features or human made features. Lineaments are usually extracted and interpreted from satellite imagery manually or automatically. Wadi Bani Malik area is chosen to apply the automatic extraction techniques from digital satellite imagery of different resolutions. The area is located to the east of Jeddah city, Kingdom of Saudi Arabia, between Latitudes 21° 34' and 21° 37' N and Longitudes 39° 17' and 39° 21' E (Fig. 1). IMAGE PROCESSING OF SATELLITE IMAGERY The six satellite imagery subset data of different spatial resolutions (LSR, MSR and HSR) for the study area were used in this work. 4 and 6). These subsets of satellite imageries for the investigated area were enhanced and prepared as false color composite imageries for LSR or as black and white imageries for MSR and HSR (Figs. 2, 4 and 6). These imageries were used for automatically extraction of the lineaments.

Abstract: Indian coalfields inherit difficult geo-mining conditions, which make it difficult to extract developed coal pillars by an underground mining approach. However, to meet the demand of coal production, three attempts of application of the mechanised depillaring have been made with mixed results. This paper, first, briefly presents results of the country's first fully mechanised depillaring face and, also, discusses the outcomes of two other attempts of mechanised depillaring. A brief review of the exiting geo-mining conditions Indian coal-fields shows that the role of support, both, natural and applied support is an important issue, which need to be addressed for the varying conditions of different sites. The important technical point to notice during the first fully mechanised depillaring face is successful application of high capacity, pre-tensioned, stiff and resin grouted roof bolts as systematic support of roof (SSR) and breaker line support for the laminated roof of the site. A review of different mechanised depillaring faces shows that the high capacity roof bolts and mobile roof support are complementary for weak and moderate roof strata. But, this approach of roof support may not always be applicable in India due to frequent encounter of massive roof strata. It is an open fact that pillar recovery at higher depth cover is another important emerging issue in the country. Coal mining activity at deeper cover is likely to intensify in the future because the shallower deposits are exhausting. At greater depths, the size of pillars is too wide to be fully extracted with single pass pillar stripping techniques. Here pillar splitting before extraction becomes the only alternative if the pillars are to be fully extracted. On the basis of experiences of different conventional semi-mechanised depillaring faces, this paper also discusses the rock mechanics aspect of manner of pillar extraction and efficacy of the left out fender for a successful high speed depillaring. It is realised that the experience of local rock mass behaviour is an important input for a successful adoption this mass production technology. Introduction Future extraction of coal, mainly through underground mining, is going to encounter, relatively, deeper excavations in difficult rock mass conditions. In India, large number of coal seams has extensively been developed by formation of pillars to meet the increasing demand of coal in the country. This is found to be a simple and safe method of coal production from underground mines. The process of pillar formation also received favourable situation due to presence of the competent coal seam and similar surrounding rock mass. Indian Coal Mines Regulations (CMR), 1957 is also quite liberal for pillar formation. This strategy of coal production found suitable for the Indian coal mining industry because of low capital investment and involvement of trivial technical expertise. Now, industry is looking towards the huge amount of coal locked up in the pillars. Underground coal mining in India is facing serious techno-economical challenge during depillaring of the developed coal seams. Conventional depillaring frequently encounters strata control problem and the productivity remains quite low.

ABSTRACT: Underground haulage drifts serve a crucial purpose of moving blasted ore material from the stopes. These drifts are driven in either footwall rock or hanging wall rock depending on the geology of the mine. As there is constant movement of men and material, the stability of these drifts is of critical importance and every measure is taken to make sure that these drifts are stable and functional. Significant effort is put into understanding the stability of these drifts and reinforcing them with suitable supports during the mine life. By making use of some user defined and built-in functions available in FLAC, a simple method to implement multiple simulations using random variables has been developed to determine the stability of underground haulage drift in the vicinity of mining activities, using numerical modelling. The probability of unsatisfactory drift performance is derived based on pre defined performance function of drift wall deformations. 1. INTRODUCTION Numerical modelling has become increasingly popular as a tool for geomechanics mine design and mine stability analysis. Methods like the finite elements, boundary elements and finite difference have proven to be extremely useful, and have been successfully used for the development of a wide range of commercially available numerical modelling software. In practice, commercial numerical modelling software is often used to perform deterministic analyses and the design values are selected accordingly. For example, the material is considered to be elastic or elastoplastic and the stability is assessed by examining the extent of yield zones, the deformations causing drift wall convergence or roof sag, etc. and, the design of support system for underground openings is based on a combination of past experience, empirical methods, and deterministic numerical models. Because of the deterministic nature of numerical models, model parametric studies or sensitivity analyses, in which model input data are varied within plausible range, are often carried out to allow for better understanding of the problem before hand, e.g. stability of mine openings, as a result of constant variation in estimated rock mass properties. Although, deterministic numerical modelling has been quite useful in estimating failure, it has been well recognized by many practitioners that numerical modelling alone cannot predict the probability of failure. Because of the inherent uncertainty associated with parameters like the in-situ stress fields, rock properties and geological features around the openings, there is also high uncertainty in the selection of support design based on such parameters. Thus, there is a need to perform stochastic analyses to derive a probability of failure to better understand the risk associated with choosing design parameters based on uncertain input data. Stochastic analysis techniques have been used with success in conjunction with limit equilibrium methods (LEM) to calculate the probability of failure in geotechnical applications like slope stability and isolated pillar collapse (Fenton and Griffiths, 2008). These problems are characterized by a single equation defining the safety factor as a function of one or two random variables, typically cohesion and angle of internal friction of the rock.

Abstract: Exploitation of minerals is a major source of revenue stimulating growth of a nation. Wave of globalization has further augmented endeavors in this direction leading to extraction of ore locked in remnant mine pillars situated in high ground stresses. One mega operation was carried out at Mochia mine involving mass firing of 0.55 million tonne of ore locked in a major mine pillar structure. Economic and safe extraction of minerals required not only the prediction of ground conditions through numerical simulations but taking preventive measure proactively also. Accordingly, whole of the depillaring operation was simulated on a Displacement Discontinuity based Software "N-Fold". To predict extent of failure of the critical mine openings a model (known as Drive Failure Model- correlating extent of failure with stress level) formulated by the authors was applied. Based on the outcome, mine openings were pre-supported prior to the mass firing the pillars. After the mass blast, these locations were again examined to determine the extent of failure and their safety status. The post blast observations revealed that the predictions made regarding extent of failure by the DFM are very encouraging. Success of the instant predictive modelling highlights potential of well calibrated numerical modelling carrying out safe and economic extraction of minerals at ever increasing depth. 1. INTRODUCTION Mochia, a Lead Zinc Underground mine of Hindustan Zinc Ltd., India, deploys open stoping for extraction of Lead Zinc ore. With progress of mining down the depth, a battery of mine pillars are formed. These mine pillars in due course of time started deteriorating causing unsafe and unpredictable ground conditions in the mine. In order to continue safe and economic extraction down the depth, some of these pillars needed their extraction (Rajmeny, unpubl. 2000). A mega operation involving mass mining of mine pillars (de-pillaring) having 0.55million tones of ore was carried out at Mochia. Safe re-entry into the mine for continuance ore extraction required numerical simulation of the depillaring and prediction of ground conditions of some of the strategic mine openings like haulage drive, extraction level, etc. Accordingly, whole of the depillaring operation was simulated on a Displacement Discontinuity based Software "N-Fold" (Golder, 1990). The Drive Failure model (DFM) – an empirical model- developed by the authors for predicting failure in drives (Rajmeny et al. 2002; Rajmeny et al. 2004) was applied to predict behaviour of the mine openings during the mass blasting at Mochia mine. It was also required to predict the behaviour of crown and rib pillars. On basis of the predictions, preventive measures including pre-supporting of the major areas of the mine such as main haulage drive at 39mRL (9th level) and LHD Garage were undertaken. These proactive measures manifested in safer re-entry in mine and resumption of ore extraction from the aforesaid pillar mass firing. Post blast ground observations were carried out to validate the DFM failure predicting model by comparing the predicted behaviour of different openings of the mine with the actual ground conditions.

SYNPOSIS: Compiled statistics show that the fall of roof is one of the major causes of coal mine accidents, contributing 44.6% of total underground accidents in India. 136 major accidents resulted into fatalities of 840 persons during 1901 to 2007. Most accidents occur in pillar mining districts, adopting Bord & Pillar (B&P) mining method (globally known as Room and Pillar mining with specific variations). This method shares about 90% of total underground coal production in India, employing about 57% of total workforce. Understanding ground control and related rock mechanics have been primordially the greatest challenge while undertaking exercises of rock excavation (primarily by blasting). In an effort to phase out timber supports usage, roof bolting occupies a pride of place. However, the application of cement bolting in India has been fallen short of planned targets of safety and productivity. The geotechnical issues are largely compounded by inventories and reinforcement procedures put in place. Keeping above aspects in view, this paper takes into account the prevailing geo-mining conditions. A simplified approach to deal with the roof control problems, presented here, consists of roof support design methodology using three dimensional numerical modelling, estimating the extent of a roof failure zone and respective rock load and finally linking with adequate support-safety factor. The approach is site-tested in many coal mines. Two representative case studies (moderate and high depths) are briefly cited, where suggested patterns of bolting were implemented. Fortuitously, the economics presented also suggests that resin reinforcement is need of the hour for Indian Coal Mines. 1.0 INTRODUCTION To improve the safety and to reduce fatigue of human beings, it was agreed upon in the recently concluded 10th Conference on Safety at New Delhi, India, that manual loading operations should be phased out in coal mines by identifying and introducing appropriate technologies in each locales, subject to understanding geo-mining conditions [1]. However in steep deposits, it is difficult to go for mechanisation with Bord & Pillar (B & P) pattern. Roof bolting with mechanised roof bolting machines will not only prevent workers to be exposed to hazardous conditions during supporting, but also will pave the way for mechanisation belowground in India. Expectedly, it will reduce the likely-occurrence of accidents. The productivity is very low, cost of coal production is high and majority of underground coal mines are incurring financial losses. Because of compelling socio-political reasons and sometimes because of technical reasons also, underground mines have to be run or to be planned for production. We need to plan coal extraction safely and economically to make underground mines viable in India. The key issue will be improving productivity which is dismally low. To meet the demand of energy and the aspirations of India's teeming millions, the coal industry has to achieve a growth rate of above 9%. The emphasis now is laid on underground winning of coal deposits in India to meet the ever-increasing energy demand. Roof bolting can be used gainfully to mitigate many ground control problems.

ABSTRACT Underground power plant projects play very important roles in meeting the requirements of present electricity requirements. Several underground structures are being built in regions that are highly prone to sheared and fault zones where their failures could cause severe damages to underground spaces. It is therefore essential to analyze and design underground structures for preventing any serious damages in these regions. Siah-Bisheh Dam and Underground Power Plan is one of the significant and important projects in Iran which is under construction. The project consists of two main parallel tunnels crossing the Alborz Structural Zone containing the Shale, Limestone and Sandstone in major parts. Because of the main role of these tunnels for conveying the water, studding and monitoring of the main fault and sheared zones and their effects on the stability of the parallel tunnels are essential. On account of these facts, at the first stage, practical methods were chosen to provide proper and reasonable supporting systems to meet the stability of the tunnels. At the second stage, two-dimensional static distinct and finite element methods were collected to perform static analysis of parallel tunnels. In this stage, with the use of the field monitoring results, the stability analysis was examined and provided supporting systems were optimized. The results of analysis were presented as displacement and strain curves and contours along the main fault, sheared zones and surrounding medium of the tunnels before and after the installing the provided supported systems [1]. 1. Introduction Siah-Bisheh Dam and Underground Power Plan project consists of two main parallel headrace tunnels. In this part of the project, a bigger chamber is located which is called Displacement Chamber Headrace (DCH). In DCH, there is a main fault connects Shemshak and Elika zones which are some parts of Alborz Structural Zone. There are also some shear zones besides. Stability analysis of these tunnels has been taken in account by using numerical Distinct and Finite elements methods separately [1]. Inputs of analysis have been gathered and determined from laboratory tests. In fact, at first stage, with use of GSI value, the strength parameters of rock mass were determined and equivalent medium which is consisting intact rock and joint sets has obtained and modeled. These parameters were examined with Rocdata software according to the latest Hock and Brown's failure criteria. The results of the analysis were compared with the monitoring data and the models were calibrated. Finally, appropriate supporting systems were determined with use of practical methods parallel to numerical analysis. 2. Statement of The Problem Siah-Bisheh Dam and Underground Power Plan is located in 155 Km of Chalous – Karaj road. It is planned to make balance the electricity power in the network [1]. In this research, the effects of shear zones and faults on the stability of DCH were examined. The dimensions of this structure are 10 × 10 × 37.5 m in width, height and length correspondingly.