Abstract Hydro-mechanical property variation of deep coal seams with CO 2 injection is a critical issue in the CO 2 sequestration process as this causes unpredictable CO 2 injectibilities and significant safety issues. CO 2 adsorption-induced coal matrix swelling is the main identified cause, where super-critical CO 2 is expected to create a greater influence compared to sub-critical CO 2 , due to its highly chemically reactive nature. Therefore, this study aimed to distinguish the effects of sub- and super-critical CO 2 injections on coal flow and strength properties. A high-pressure rig was first developed to conduct experiments under in-situ conditions and the developed rig was then used to conduct coal permeability tests. The test results exhibit a much greater swelling effect with super-critical CO 2 adsorption, which therefore produces lower permeability values in coal compared to sub-critical CO 2 . Temperature also appears to create a significant influence on CO 2 flow behaviour in coal, and CO 2 permeability clearly increases with increasing temperature for high CO 2 injection pressure (> 10MPa). Interestingly, N 2 has the potential to reverse CO 2 -induced swelling effect to some extent, which is favourable for field projects. The results of UCS strength tests show that both strength and Young's modulus of any type of coal are significantly reduced due to CO 2 adsorption, and the reduction is higher for super-critical CO 2 adsorption than sub-critical CO 2 . CO 2 adsorption-induced strength reduction increases with increasing coal rank, which is due to the well-developed natural cleat system in mature high rank coals. The extensive time and cost of laboratory experiments can be minimised by the use of appropriate numerical modelling tools and this study therefore provides a step-by-step guide to the development of such a modelling tool using a user-friendly field-scale simulator (COMET 3). This model can be effectively used to predict the CO 2 movements in coal under tri-axial laboratory conditions. Theoretical models play an important role in speeding the identification of coal mass properties and are believed to be more accurate. Therefore, a theoretical equation for coal cleat permeability under non-zero lateral strain tri-axial test condition was also developed. These models are expected to be highly useful in future, laboratory-scale CO 2 sequestration studies to establish the required tri-axial test conditions.

ABSTRACT A study was undertaken to investigate changes in the strength and failure pattern of otherwise standard rock core specimens containing regularly spaced discontinuities. The objective was to assess changes in the nature of rock failure resulting from these discontinuities. Test core specimens were prepared from sandstone having dimensions of 44 and 110 mm for diameter and height respectively. The core specimens were cut at right angles to the longitudinal axis of the core producing composite specimens having 2, 3, 4 or 5 regularly-spaced surfaces. As well as testing specimens having dry, clean fracture surfaces, the test program also considered different infill materials and hence friction values using dry and oiled-impregnated paper. The study found the strength of specimens decreased with the number of discontinuities. While the UCS strength of the intact rock specimen was 35.8 MPa, the strength of composite specimens having five segments was reduced by 50% to 17.9 MPa. This is despite the reduction in the slenderness ratio of each segment in the composite specimen that would usually result in an increase in strength. Less sensitive were changes in infill material having little discernible effect over for the limited range of friction surfaces investigated.

ABSTRACT This article describes the results of ultrasonic triaxial tests performed at high temperature to simulate the impact of SAGD (Steam Assisted Gravity Drainage) project on the rock properties of a heavy oil reservoir in Venezuela. The tests were performed using unconsolidated sandstone samples at high temperatures. The purpose of these tests was to evaluate the impact of temperature on the compressional velocity in order to predict rock strength from logs during SAGD operations. These analyses are crucial to evaluate the impact of high temperature on UCS, Poisson's Ratio, Young's Modulus and Internal Frictional Angle. The results are indicating a reduction of compressional velocity of about 20% at 1500C. The article describes the results and discusses the used methodology.

ABSTRACT The plastic characteristics of the coal seam floor has been explored in this article on FEM stength reduction with the software of ANSYS, and the plastic area perforation process has been given. The slip scope given on FEM strength reduction are much close to the theoretical solution, the plastic failure fields depth of the coal seam floor is similar to Prandtl type, comparing some parameters with the theoretical solution. The solution error between FEM strength reduction and theoretical solution is less than 10%, which showed that the finite element intensity reduction method used to solve floor damage process is feasible. The scope of its plastic area can be used to reserve the safe thickness in water outburst from coal seam floor and the maximum effective spacing of protected seam.

ABSTRACT Cement grouting has been used as an effective method to reduce the permeability of the fractures in rocks. This study discusses the mechanism how cement grout controlled water permeation through the fractures in rocks, and focuses on the effectiveness of the clogging of cement particles for closing water paths. Quantitative investigation is made through laboratory tests and numerical simulation implementing a finite difference method (FDM) and a moving particle semi-implicit (MPS) method. As a result, a model is proposed of grouting mechanism using cement particles, and the validity of the proposed model is verified by numerical simulation.

Abstract: Perforation job consists of creating holes in the near-wellbore formation by shooting the perforation agent through the formation in order to provide a means for hydraulic communication between the wellbore and hydrocarbon bearing formation. Perforation itself may alter the porosity and induce damage to the rocks in the vicinity of the wellbore to some extent, which consequently results in reduced production. Due to difficulties associated with conducting laboratory experiment under in-situ stress conditions to study a perforation scenario and inefficiency of commonly used numerical simulators suitable for continuous medium to model such a dynamic process, in this work a discrete element method (DEM) code was used for modeling purposes. Using particle flow code (PFC) porosity and different in-situ stress changes were simulated in 2D to distinguish the level of rock damage along or/and around a perforation tunnel. The formation was simulated as an assembly of densely packed particles bonded together. The perforation was simulated by shooting an agent penetrating through the wellbore wall with a high velocity to create a perforation tunnel. The results are presented in this paper and the advantages and disadvantages of the DEM code and 2D numerical approach are explained. The simulation results obtained for different scenarios of operating conditions and rock mass properties will also be compared with previous models. INTRODUCTION DEM based codes have been used in a wide range of petroleum applications including sanding prediction and wellbore stability, modeling of hydraulic fracturing and fluid leak-off in a fracpack [1–3]. However, this technique has rarely been used for modeling perforation phenomenon [4, 5]. The results of recent studies demonstrate the possible applications of DEM numerical codes for modeling a perforation job. In this paper, it is shown in particular how porosity may change around the perforation tunnel during a short period. This, to the best knowledge of the authors, has not been the subject of any study in the past. In contrary to a small number of numerical studies, considerable experimental works have been carried out to investigate the effect of operating conditions and rock parameters on the quality of perforation job. The results of these experiments show that formation porosity [6], ultimate strength [7–10], wellbore pressure [8], acoustic velocities and bulk modulus [11–13], grain size [14], lithology [15], heterogeneity [16], and confining and effective stresses [10, 12, & 17] are the important factors that may affect the job performance. Amongst these parameters, few available publications discussed whether or how porosity may change around the perforation tunnel as a result of perforation, yet the available literatures present dissimilar conclusions. Some papers report that as a result of perforation the rock grains are subjected to a severe shock-type pressure (in orders of millions of psi) in a very short time period (microseconds) and accordingly metamorphous rock structure with lower porosity may be formed [18]. In these studies the porosity reduction also is considered due to grains compaction and/or creation of planar fractures around the perforation hole, and also validated by experimental results.

Abstract: The Ube-Isa Limestone Mine in Japan is surrounded by many residents, and blasting events causing airblast (infrasound and low-frequency sound; 1 to 80 Hz) have been problems to solve. Strategies to reduce the airblast should be studied for both influences on humans and impacts on homes in the area. The matters are dependent on not only the airblast (sound) level but also the frequency. For reduction of airblast level, we have focused our studies on blasting free face area and blasting direction. And for control of frequency, we have focused on time delay of shot by using non-electric detonator and electronic detonator. By applying the above strategies, blasts over 95 dB has decreased by half, and our studies indicate that a rattling of fixtures can be controlled by adjusting time delay shot. 1. INTRODUCTION Ube-Isa Limestone Mine lies in MINE city in Yamaguchi Prefecture, Japan. The annual limestone output was 8 million tons in 2008. The total production is 440 million tons (Japan's top) for 60 years since 1948. As the mine is surrounded by many residents, blasting events causing ground vibration and airblast (infrasound and low frequency sound) have been problems to solve. And recently, the impact of the airblasts have been getting larger because gradually our mining operation have been moving closer and closer to resident homes. Before this airblast study, ground vibration has been controlled by the explosive's volume and time delay shot. But an effective method of airblast control had not been set up. Strategies to reduce the airblast should be studied for both influences on residence such as stress, headache, ringing in ears and for fixtures in the home such as rattling of doors and windows. The above matters are dependent on not only the airblast (sound) level but also the frequency. Blasting free face area and blasting direction are studied for reduction of the airblast levels. Time delay of shot is studied for the frequency control by using non-electric detonators and electronic detonators. After our study, several definite results of the airblast reduction have been given as follows. 2. MEASURES OF AIRBLAST REDUCTION For reduction of noise, there are 3 measures from the following viewpoints, source of sound conveying process receiving side. However, measure-2) is not expected to be effective to reduce the noise because airblasts have long wavelengths that diffract even soundproofing walls. Measure-3) is also not realistic because of the number of factors that exist at the sound receiving side. For these reasons, measure-1) source of sound, which is the blasting itself, has been the focus strategy. 3. REDUCTION OF AIRBLAST LEVEL (1) Area Reduction of Blasting Free Face We tried to validate that the area reduction of blasting free face can lower the airblast level(dB). We compared airblast levels that occurred from 4 types of blasting as the ratio of free face area; standard:1,low bench:0.8, multiple row:0.6 and face covered:0.2 under the conditions of the same volume and powder factor by arranging them in parallel as shown in Fig.1.

SYNOPSIS: The present paper deals with climate change impact on stability of underground cavities due to its indirect effect on ground water levels. In France, several back-analyses have confirmed that variations of underground water tables play a key role in the genesis of surface disorders above shallow mine workings. The paper presents the forecast impacts of climate change on the behaviour of underground water tables as well as the consequences of those variations on the stability of disused underground cavities. A particular collapse that affected the Paris Basin during a major flood of the Seine River, one century ago (January 1910), with dramatic consequences, illustrates the importance of water variation impacts on the rock mass behaviour. The high sensitivity of the extracted material (very pure chalk) to water as well as the dynamics of the mine flooding process are described. The most realistic mechanisms and scenario enabling to explain massive failure of the underground workings are then discussed. 1. INTRODUCTION The existence of a global warming process of the global climate is now well admitted by the scientific community. The rise of the average temperatures of air and oceans, as well as the observation of the de-icing of ice caps and the rise of mean sea level constitute some clear indicators. The various studied prospective scenarios, depending on the efficiency of prevention policies engaged by governments show that, up to 2100, the average rise in temperature on the surface of the Earth could vary between 1,5 and 6 °C [1]. Such a temperature increase would be likely to generate serious disturbances on climatic parameters (e.g. modification of rainfalls, disturbances of water tables). Numerous international studies are being performed in order to make progress in the understanding and prediction of the consequences of the presumed climate change. Among these studies, very few relate to the matter of underground cavities. The paper deals with the impact of climate change on stability of underground cavities. This topic may become a serious problem in France due to the existence of very numerous (hundred of thousands) shallow underground cavities, natural or manmade, well known or totally unlocated, undermining French territory. Several recent examples have confirmed that, among those, the level and variations of underground water tables have a key role in the genesis of surface disturbances. Major trends concerning the forecast impacts of climate change on underground water tables as well as the consequences of those variations on the mechanical behaviour of shallow underground workings (impacts on strata and discontinuities) are thus briefly presented. Among others, the specific case of a ground collapse (with dramatic human consequences: 7 deaths and 7 severe injured persons) that affected the Paris Basin during a major flood of the Seine River, one century ago is then described, as a perfect illustration of the importance of water variation impacts on rock mass behaviour. The chalk mine of Lorroy (city of Chateau-Landon), collapsed in January 1910, in direct connection with the flood of the Seine River.

Abstract At the Sarcheshmeh mine, the design and stability analysis is very critical due to the existence of major features such as faults and dikes, and relation of various joint sets with the geometrical form of the pit. Western area of Sarcheshmeh mine includes various types of failures, commonly structural failure type such as Sarcheshmeh pseudowedge failure. This type of failure consists of large and weak blocks of weathered highly jointed andesite surrounded by a fault and important joints. Existence and extension of near parallel faults filled with pyrite-clay in the western wall of Sarcheshmeh mine along with the geometry of this wall results in special slide conditions which need to be considered during mine expansion project. There are some limitations in using limit equilibrium methods to analyze this type of sliding. This paper analyzes Sarcheshmeh pseudowedge failure using three dimensional distinct elements method. The influence of effective parameters on the stability of such failures is quantitatively calculated and proper solutions are discussed. 1. Introduction The Sarcheshmeh porphyry copper-molybdenum deposit is located in southern Iran, at 30 degree N lat., 56 degree E long. It is currently the largest open pit mine in Iran. Western area of Sarcheshmeh mine includes various types of failures, commonly structural failure type such as Sarcheshmeh pseudowedge failure. This type of failure consists of large and weak blocks of weathered highly jointed andesite. Due to intersect of a fault with the rock mass surrounding the walls of this area (figure 1), various wedge-like rocks have been progressively sliding on the fault plane [1]. Sarcheshmeh mine is being expanded as a result of cut off grade reduction. Existence and extension of near parallel faults has made pseudowedge failure a new challenge in expanding western area of Sarcheshmeh mine. Most parts of this rare failure are kinematically stable but they will become instable with time and therefore they can not be kinematically analyzed. In limit equilibrium analysis, the stability is investigated regardless of its relation with displacements and safety factor is calculated based on static condition. Therefore, when displacements occur in a slope, limit equilibrium methods are not suitable to evaluate the effect of such displacements on total stability of the slope [2]. An example of such analysis has been done on Sarcheshmeh pseudowedge failure [3]. Numerical methods are available to analyze and model this phenomenon according to observations. This paper analyzes Sarcheshmeh pseudowedge failure using three-dimensional distinct elements method. The influence of effective parameters on the stability of such failure is quantitatively calculated and proper solutions are discussed. 2. Geological Settings Porphyry ores, such as Sarcheshmeh, are the most complex geological environments in terms of fracturing. The Sarcheshmeh deposit is related to the Late Tertiary granodioritic stock which intruded the early Tertiary volcanics. The deposit 560 was intruded by intra-mineralization and post mineralization dikes and intrusives [4].

I. UNDERGROUND WORKS AND THE ENVIRONMENT As far as the single underground work (cavern or tunnel) is consIdered - instead of the whole structure that can have one of more tunnels - the physical features of the environmental impact are examined, why the social and economical aspects are not taken into account. Actually, an underground work gives some positive points environmentally friendly, in a way more incisive than other structures built on the territory; these key points are interesting to choose the underground solution: the underground structure does not create physical barriers crossing the land; It is not exposed to the site, and only the two adits are visible; the operation is not influenced by atmospherical agents; it is not subjected to surface stability phenomena (apart those of the portals); less maintenance costs are required if compared to an analogous surface structure; the tunnel reduces the length of the way offering the conditions for energetic savings; (during the operation) the emission of noise, gas, dust are concentrated at the adits ' it is quite protected against the seismic actions. 1 he underground work presents also negative environmental features. which can decrease the level of acceptance. Apart from the disturbs due to the construction phase when the land is occupied by operative services (roads. houses, trucks) - which are nevertheless reduced when compared to the open site works - one can have the noise dust gas vibration emissions, pollution Water, perturbation of' normal load traffic and surface uses, especially when located in urban areas; underground construction have also four other main environmental problems: perturbation, pollution and drainage of the groundwater; selliements of the surface of the land; Waste rock disposal: uncertainties in the preventive definition (for example in the design phase) of the geological, geotechnical. geohydrological conditions of the underground, which determine the risk of collapse and consequently sink holes. On the other site the risk of delays and increasing of the construction costs: I These demanding 'subjects have been studied by the ITA (Internalional Tunnelling Associations) which created in 1995 the Working Group 15 under the name of "Underground works and environment". The main objective of this group is 10 help the economic agents that operate in the underground world to take advantage of the opportunities and to minimiqe the risks associated with the new environmental culture. 1.1 Environmental Legislative Framework Environmental legislation has both positive and negative consequences on the different agents that operate in the underground world. But on the other hand, an increase in production costs and a major responsibility demand of the economical agents. As environmental legislation becomes more and more strict. underground works will take advantage of their advanced positionas compared to the superficial ones. The tunnelling associations of the countries participating in the survey hold varying opinions about the interrelations between underground works and the environment, although the totality consider that the increasing environmental sensitivity and legislation will have a positive influence on the future development of underground works.

ABSTRACT: A large scale rock slope failure, with an estimated collapse volume of 2,700,000m 3 , occurred at a site where the deformational behavior had been monitored over several years. The characteristics or the behavior were in that the deformation was recorded not only during excavation of the slope, but also "between excavations. This paper presents a summary of an investigation on the deformational mechanism both during and between excavations. In particular, a finite element procedure used herein has introduced a new method of modeling deformation between excavations so that it can associate with a reduction of material strength parameters. The results of this investigation suggest that a sign of a large scale collapse might have been seen in a relatively early stage of the slope excavation procedure. I. INTRODUCTION As one of the practical data interpretation methods, Sakurai et al (Sakurai, 1998. & Okuda, 1999) have suggested back analysis techniques for monitoring displacements measured during slope excavation, in which safety factor is calculated based on measured displacements. However, the methods had a difficulty in interpreting displacements which occur when excavation procedure is not progressing. The reason was that in this method, like in most of the previous approaches dealing with identification of measured displacements for safety assessment of slopes, the modeling was based on a deformation process by directly relating excavation to measured displacement. However in reality, significant amount of deformation occurs, just like the case in concern, between excavations due to various reasons such as rainfalls, degradation of rock materials along weak planes, etc. In order to describe these processes correctly, a new computational approach was developed by which displacements measured between excavations could be explained in terms of the loss of strength or stiffness along a potential slip planes of a rock slope. The paper describes briefly the nature of the slope failure, conceptual ideas of the new modeling methods, and one of the possible interpretations of the massive rock slope failure. 2. MODELLING In this attempt, a new framework of the modeling procedure was prepared, in which an ordinary force-displacement relationship and material property degradation displacement relationship, were encoded in a nonlinear FEM procedure. The first option treats a standard force-displacement relationship in which displacements measured during excavation arc modeled. The second option, of course, is introduced in order to model deformational behavior occurring when no excavation is made. A summary is given below to describe some of the key features addressed in this approach. 2.1 Anisotropy parameter "m" A basic constitutive relationship employs an anisotropy parameter "m" which was suggested by Sakurai 1), 2). In this model, the anisotropy parameter, relating shear stress and strain, is reduced in an exponential fashion as shear strain increases. The reduction of the parameter is associated with potential slip plane directions. 2.2 Corrective scheme of stress state The Mohr-Coulomb friction law is imposed along potential slip plane directions and stresses computed in an incremental scheme are corrected to be on or within a failure envelope.

ABSTRACT: Several studies until now have been carried out on the variance of strength when curing concrete is subjected to Vibration. But the vibration sources considered on these studies were impact, shaking table and surface blasting Mortar lining model with cylindrical shape was made for laboratory tests and real concrete wall and bottom lining model was built in tunnel for field test. The results of the laboratory test showed that vibration with 2cm/sec increased P-wave velocity of mortar lining model and vibration with 5cm/sec could decrease P-wave velocity. The results of field test showed that compressive strength of all lining concrete subjected to blast-vibration below 2.5cm/sec for curing period was increased. The critical value of blast-vibration on concrete after 5 hours of casting was 3–4cm/sec, which can decrease the strength of concrete from small-scaled test blasting on concrete lining. This result was in accordance with the result when compared with P-wave velocity. I. INSTRUCTION Mostly, the lining-concrete at tunnel site has been poured after the blasting work for the excavation of rocks in Korea. To do these two works simultaneously can reduce working hours for tunneling, but blast-vibration generated by blasting work can cause damage of curing lining-concrete. Damages of curing lining-concrete mean the strength decrease of concrete or occurrence of cracks at lining, so many studies to determine the effect of blast-vibration on curing lining-concrete in tunnel are necessary. The strength of concrete is increased gradually after casting. Therefore early aged concrete is more dangerous by blast-vibration. Lining-concrete poured in tunnel is subjected by blast vibration of which dominant frequency is over 150Hz. But the dominant frequency of vibration in several studies conducted to determine the effect of vibration on curing concrete until now was mostly below 100Hz. Also vibration source in these studies was not tunnel blasting but was shaking table, impact hammer or surface blasting (Bastian, 1970; Howes, 1979; Desai et al, 1984; Lim et al, 1994; Hulshizer, 1996). Therefore, in this study impact hammer test at laboratory and blast-vibration test at tunnel site were conducted to determine the effect of vibration of which dominant frequency is in the range of 150–300Hz on curing lining concrete. We measured the strength and elastic wave velocity of concrete specimen at 28 days after casting and the variance of strength and elastic wave were analyzed according to magnitude of vibration that subjected to lining concrete. 2. IMPACT VIBRATION TEST 2.1 Test Procedure Mortar lining model with cylindrical shape was cast between sheeting and rock block. The structure of this model is similar to that of concrete lining in tunnel site. Two types of hexahedral rock block were used. The size of 30B block is 300 x300x300mm, and that of 50B block is 300x300x500mm. A cylindrical hole to copy tunnel was built by coring at the center of each rock block. The diameter of cored hole at each rock block is about 100mm and the thickness of mortar lining model is about 12mm.