In Japan, a bench cut method is mainly applied for limestone quarries. As most of the mines are located in the mountain regions and steep slope mountains, the shaft and the underground opening for installation of facilities such as crushing equipment are applied in order to provide workability and economic efficiency for transportation and crushing ores. However, as the mining operation proceeds, the level of the pit will be down and the distance between the mining area which is the bottom of the pit and the opening for underground facilities such as crushing equipment become to be short. In order to maintain the safe mining operation and the stability of the underground opening, the appropriate distance between them has to be maintained. Therefore, in order to develop the guidelines for safety distance between the mining area and the underground opening for installation of facilities such as crushing equipment under different rock mass conditions in a limestone quarry, a series of numerical simulations are conducted by means of finite differential code “FLAC3D”. 1. Introduction Currently, more than 200 limestone mines are in operation in Japan. A bench cut method is mainly applied for limestone quarries of the open-pit mine. In general, the limestone ore excavated from a limestone quarry at a high elevation is introduced into the shaft to achieve efficient transportation by utilizing the gravity. After that, the ore is crushed by the underground crusher and transported by the belt conveyor to the facility of processing at the foot. As most of the mines are located in the mountain regions with a steep slope, the shaft and the underground opening for installation of facilities such as crushing equipment are applied in order to provide workability and economic efficiency for the transportation and crushing ores. However, the stability of the shaft and the underground opening is suspected when the rock mass conditions are poor due to the existence of a fractured zone. In addition to that, as the mining operation proceeds, the distance between the surface and the underground opening becomes to be short with the down of the level of the pit. In order to maintain the stability of the underground opening, the appropriate distance between them has to be maintained. However, there are few studies about the influence of the rock mass conditions especially fractured zone and the mining operation on the stability of the underground opening. Therefore, in order to discuss the safety distance between the surface and the underground opening for installation of facilities such as crushing equipment under different rock mass conditions in a limestone quarry, a series of numerical simulations are conducted by means of finite differential code “FLAC3D”.

This study describes the importance on the evaluation of rock mass condition before mining and probability of failure during mining under slope surface in shallow depth. It is well known that several factors can affect the stability of underground openings such as the quality of rock mass, the in-situ stress, the depth below the surface and opening geometry. In addition to those parameters, if underground mining is conducted near the slope surface, the influence of slope surface should be taken into account during any mining activities. Consequently, stability analysis has been conducted for three different conditions including the evaluation on the strength of rock mass in the sloping surface, assessment on the stability of stope mining near the slope surface, and instability of stope in the nearground region in various mine condition. The preliminary results show the instability of rock mass near to slope surface is more severe than that of the rock mass far from the slope surface, therefore large instabilities of rock mass near the slope surface are experienced. In addition, the occurrence of failure zones of stope mining in the near-ground region under slope surface become more pronounced in weaker geological condition and higher stress ratio. All the investigations for these analyses are conducted by means of 3D finite difference software using FLAC 3D . 1. Introduction Stope mining is the most common mining method adopted in underground metal mines of Myanmar. However, the assessments on the stability of stope still remain quite limited in those mining industries. Currently, most of the underground metal mines are being mined-out or still mining at shallow ground part. Moreover, there are not so many recorded data regarding rock mass failures cases in underground mining due to cut and fill stoping methods in Myanmar. Hence, the study on the stability of underground mines in shallow part become one of the important issues to mitigate the unpredictable nature of rock failures. Two forms of instability are readily observed around underground openings: (1) structurally controlled gravity-driven processes (2) stress-induced failure or yielding (Martin et al. 2003). In many pieces of literatures, some instability indicators are usually defined in terms of failure zones, stress condition, displacement and extent of yield zones (Abdellah et al. 2018) (Karian 2016) (Purwanto et al. 2013). In this study, the evaluation on rock mass condition and mining under the sloping surface are described by the occurrence of natural and mining-induced differential stress and failure zones affected to mining activities. Considering the importance stability of underground mining under slope surface, some investigations on the characteristics of rock mass and mining condition are carried out at Modi Taung gold mine, one of the largest underground gold mines in Myanmar.

Infrastructure development in urban areas has progressed rapidly, and the demand for construction of pipes for electricity, gas, water supply and sewerage, etc. is increasing. In the urban construction of pipe, the non-open cut method is generally used to prevent traffic disturbance, building influence, noise and vibration, one of which is a Shield method. Shield method is a construction method that rotates the cutter head at the tip of the shield machine, excavates the ground, and constructs an underground pipe ditch. In recent years, construction condition of Shield method is diversified such as long distance, great depth, high water pressure and gravel ground, etc. Bit wear is a factor affecting workability and economic efficiency in Shield method, and the various investigations have been discussed so far, but the quantitative guidelines on bit wear prediction have not been established because the wear factor is complicated in the gravel ground. This study was conducted in order to obtain fundamental knowledge for predicting bit wear in gravel ground. 1. Introduction The shield machine has the cutter head with bits as shown in Fig.1, and the ground is excavated by rotating the cutter head and pushing it by thrust jacks. However, the bit wear during cutting operation is inevitable. As the bit wear has an obvious impact on the construction progress and cost, such as lowering of drivage efficiency, increasing the frequency of bit replacement, etc (H. Shimada et al, 1989). Therefore, the prediction of cutter bit wear in advance is important. However, there is few research on the characteristics of bit wear in gravel ground and the prediction method of the bit wear in theoretically and quantitatively. From above point of view, this paper discusses the effects of characteristics of gravel and the gravel content on the characteristics of bit wear in gravel ground based on the results of a series of laboratory tests for the simulated sample of the gravel ground in order to develop the prediction method of bit wear for excavation in gravel ground.

The ideal mindset of coal mine industries is to extract the maximum amount of coal possible from the coal seam resource. However, there is an absolute limitation when it comes to coal excavation depending on geological condition and the adopted mining method of each mine. As a result, there must be some remain coal thickness left. This can be beneficial for coal bed that is surrounded by weaker dominant rock as the remained coal can help improve the stability of any opening structure during the mining development and excavation. This research seeks to identify the optimum remain coal thickness (RCT) above and below the excavation in order to maximize the stability of the gate-entry and investigate appropriate support for gate-entry. With this in mind, a trial panel of an Indonesian coal mine, which is located in East Kalimantan, is selected as the research study area. This mine situated in weak geological condition, which is common for coal resource in this region. This paper use FLAC3D for numerical simulation. Preliminary result, show that the reduction of displacement on top and bottom of the gate-entry does not increase much when the RCT is left more than 1 m on both the gate roof and floor. This can be a great indicator for optimum thickness for remain coal. The outcome also shows that steel arch SS540 with 1 m spacing is appropriated for adopting in this trail panel gate support system. The result from this research is essential for developing mine design in this region as well as other coal resources that have a similar condition. This knowledge also allows mine design to have a better support system optimization compare to previous work, which did not consider the effect of RCT. 1. Introduction Indonesia hosts an abundant portion of thick coal deposit, which is usually found in weak geological condition (Sasaoka et al., 2015). This weak geological condition has led to the limitation of excavation into a certain height (Ozfirat et al., 2005). As a result, some of coal thickness remains on top and bottom of the excavation. This can be beneficial for coal bed that is surrounded by weaker dominant rock as the harder remained coal can help improving the stability of any opening structure during the mining development and excavation.

In recent years, the underground space has overcrowded with the overcrowding of urban areas. Therefore, the adjacent construction of underground structures is increasing. In such a construction, an influence of the construction of a new structure on the existing structure has to be considered. In order to minimize the influence on such existing structures, application of the underpinning method is expected. The underpinning method is a construction method that attempts to reduce the influence on the existing structures by excavating the ground around existing structures with constructing, rebuilding, and reinforcing new foundations. This study focuses on the underpinning method using pipe jacking. In order to ensure the effectiveness of the underpinning method, 3D finite element analysis was carried out. In particular, four major considerable factors were discussed: the influence of pipe presence, comparison of using conventional underpinning and pipe jacking, the influence of the distance between the pipes and new structure, the influence of pipe length. Based on the numerical results, it is possible to reduce the vertical displacement on the existing structure by using the underpinning method using pipe jacking. Additionally, the underpinning method using pipe jacking is effective to reduce the displacement over a wide range compared with the conventional underpinning method. Furthermore, the influence on the existing structure and the surrounding ground can be minimized by adopting the proper distance of pipe length and the space between the pipes and the new structure. 1. Introduction In recent years, overcrowding has occurred due to the factors such as population increase in urban areas. Various structures are complicated in the underground space and the underground space is overcrowded along with the overcrowding of urban areas. Therefore, adjacent constructions of underground structures are increasing in the underground space of urban areas. Adjacent construction of the underground structure is the construction such as adding an underground tunnel to the surroundings of the drainage pipeline. In adjoining constructions of such underground structures, it is a problem that the influence on existing structures becomes particularly large when constructing new structures. Application of the underpinning method is expected as a construction method to reduce the influence on existing structures. Recently construction methods such as cutting edge jacking method, and shielding method are mainly applied when constructing an underground structure. (Matsumoto et al., 2015) These construction methods are required to occupy a wide range of construction area, long construction period and high cost, so it is difficult to apply those construction methods in urban areas. Therefore, pipe jacking method which is non-cutting technique is required as an effective construction method in urban areas (Japan Tunneling Association, 1997). For the above reasons, construction of the underpinning method using the pipe jacking method is expected for adjoining construction of underground structure.

Kyaukpahto gold mine located in the Kawlin Township, Sagaing Region of Myanmar is the first open pit and the largest gold mine of Myanmar. As the gold is exploited by open-pit mining, a large amount of waste rocks are disposed at waste dumps near the mine site. The metal sulfides such as pyrite, arsenopyrite, and chalcopyrite in the waste rocks are exposed to the surface, favoring the oxidation of these metal sulfides and generating acidic water. There is a possibility of AMD generation in the open pit and at the low grade ore dump. This work focuses on assessment of the potential acid-forming waste rocks and characterization of these waste rocks in Kyaukpahto gold mine. Waste rocks and water samples were taken from the open pit, low grade ore dump, and waste dumps and subjected to various tests and analyses such as NAG test, Paste pH test, Paste EC test, ANC test, XRF, XRD, and ICP-MS analyses. Based on the results of the chemical tests and analyses, waste rock samples collected from open pit and low grade ore dump are identified as PAF rocks which particularly concerned with the potential generation of acidic mine water. Two-step batch leaching test indicated that low pH value (pH 4) and elution of metal ions such as As, Al, Fe, Cu, Zn, and SO 4 2− were observed with the high concentration from the samples. Elution of As is higher than other metal ions and this elution process will take place over a longer period than other metal ions. Thus, it is very critical to take appropriate measures against generation of AMD, such as controls on sulfides oxidation, and reduction of metals elution. 1. Introduction Acid mine drainage (AMD) which is also known as acid rock drainage (ARD), causes environmental problems that affect many countries with historic or current mining activities. AMD is resulted from the exposure of sulfide ores and minerals to water and oxygen. When the ore is exposed to generate AMD, sulfate and heavy metals such as iron, copper, lead, nickel, manganese, cadmium, aluminium and zinc are also released to contaminate into that water (Moodley et al., 2017). Acidic, metals-rich waters may also form in spoil heaps, waste rocks and mine tailings, essentially by the same biologically reactions as in mine adits, shafts, pit-walls and pit-floors. Due to the more disaggregated (and more concentrated, in the case of tailings) nature of the acid-generating minerals in these waste materials, AMD that flows from them may be more aggressive than that discharges from the mine itself. Another important consideration is that it poses the potential long-term pollution problem as the production of AMD may continue for several years after mines was closed and tailing dams was decommissioned. (Johnson & Hallberg, 2005). The most common acid-generating sulfide minerals are enlisted as pyrite/marcasite (FeS 2 ), pyrrhotite (FeS), chalcopyrite (CuFeS 2 ) and arsenopyrite (FeAsS). In general, pyrite, the most common sulfide mineral of waste rocks and typical of many oxidation processes during weathering, is oxidized in accordance with the following reactions (Sengupta, 1993): (Equation)