Assessment of overburden dump slope stability is an issue that continuously evolves with time. Engineered slope structures in large opencast mines require a continuous assessment of their stability condition. In this paper, machine learning application has been used for the stability classification of dump slopes. Although, some research work has already been done in this area, they mainly aim to assess the accuracy and reliability of results obtained by the machine learning method. Also, these studies are based on supervised learning algorithm where the output with limited dataset has been obtained from conventional methods. No comprehensive research has been done for assessment of stability condition of overburden dump structures with the help of machine learning till now. In order to overcome these limitations, an updated and proper methodology has been worked out in this study. It provides a three-category classification of dump slope stability in introducing ‘critically stable condition’ in addition to the ‘stable’ and ‘unstable’ categories that already exist in previous classification systems. A dump structure under this category is more prone to failure even when the Factor of Safety (FoS) is greater than 1. Three standard methods of supervised learning classification, i.e., Decision Tree Classifier (DTC), Support Vector Classifier (SVC) and Naive Bayes classifier (NBC) have been used to arrive at this conclusion. The performance of these methods have also been analysed with the help of the confusion matrix. For these supervised learning methods, the output obtained from numerical modelling software FLAC 2D v7.0 have been used. Six input parameters have been considered for the parametric numerical modelling study, i.e., Total Dump Height, Bench Height, Bench Width, Bench Slope Angle, Cohesive strength and the angle of internal Friction of the dump material. It has been found that the DTC method performed well with the highest accuracy score of 0.9355, while the accuracy score of SVC & NBC are 0.7742 and 0.6451, respectively, for the given range of input parameters.

Abstract Properties of rock mass vary and an exact value of one of the properties at any given location cannot be predicted. On the other hand, in applying some classical methods of structure stability analyses, only one value of certain parameter must be input to the formulas or even the computer codes. Stability of the structure is evaluated by comparing the capacity (strength or resisting force) of the structure and the demand (stress or disturbing force) and expressed in term of Factor of Safety (FoS). The FoS calculated by this deterministic approach obviously has limitation for assuring the stability of structure. The rock mass uncertainties can be dealt with by taking into account statistical distributions of the parameters in the FoS calculation or by developing empirical design guidelines or curves based on a particular regression techniques on case histories of stable and unstable structures with particular design parameters and properties. This paper gives some examples illustrating approaches for dealing with uncertainties in the rock mass. 1. Introduction Design and construction in rock require processes and procedures that are in many ways different from other design and construction projects, because the main construction material is the rock mass itself rather than an engineered material. The rock mass properties do not have a single fixed value but may assume any number of values at any given location. It is then obvious that the classical approach of Factor of Safety (FoS) where the calculations are based on one value of a certain parameter, is unable to fully assure that a structure with FoS greater than 1.0 will be stable. Two approaches can be utilised in dealing with the rock mass properties uncertainties. First, the FoS calculation is conducted by taking into consideration all possible values of rock mass properties. In practice, the values can be represented by the statistical mean and the standard of deviation of the parameters which depend on their statistical distribution functions. The calculated FoS then has also mean value and standard of deviation. Probability of having a particular value of FoS can also be calculated. Secondly, stable and unstable structures case histories can be collected and for practical reasons, the main data that must be recorded for each structure are geometry, strength, stress, and stability condition. Curve separating stable and unstable case histories can be constructed by using regression techniques. In addition, iso-probability of stable (or failure) curves can also be plotted.

Abstract GPS is now being used widely for monitoring rock displacements, and it has been a useful tool for various rock engineering projects. The most important technical issue for the practical use of GPS in monitoring displacements is to perform real-time and precise monitoring even under adverse observation conditions, i.e., steep slopes, the existence of trees and walls above/around the sensors, bad weather conditions, etc. The authors and their colleagues have developed a precise real-time displacement monitoring system using GPS and have established a method of data processing which can automatically reduce the errors caused by meteorological factors and obstructions above the antennas. In this research, the GPS displacement monitoring system is applied to monitor the displacements of an unstable steep slope for the safe management of a national road in Japan over the long term. Three-dimensional displacement monitoring results are shown. 1. Introduction Monitoring rock displacements is important to assessing the stability of rock slopes. The Global Positioning System (GPS) can continuously measure three-dimensional displacements over extensive areas. The "ISRM Suggested Method for Monitoring Rock Displacements Using the Global Positioning System" was proposed (Shimizu et al., 2014) as technology which can be used by anyone. In this research, the GPS displacement monitoring system developed by the authors is applied to assess the stability of an unstable steep slope along a national road in Japan. Since local slope failures have occurred in the slope several times over the last 20 years, displacement monitoring has been conducted by borehole inclinometers and surface extensometers. Some of the instruments, however, have occasionally not worked due to large deformations, and it has become difficult to perform the monitoring continuously. In order to overcome such trouble, the GPS monitoring system has been applied (Furuyama et al., 2014). In this paper, the results of three-dimensional displacement monitoring using GPS are shown, and the applicability of this system for assessing slope stability is discussed.

Abstract The process of slope stability analysis is one of the most important stages in design of some civil and mining projects. Bimslopes are made from bimrocks (block-in-matrix rocks) where rocky blocks are distributed in a bonded matrix of finer texture. This kind of slopes usually are seen in weathered and shallow environments. Previous studies have shown that VBP (Volumetric Block Proportion) is one of the most significant factors affecting bimrocks strength and consequently the stability of bim lopes. In this paper, the influence of blocks orientation on bimslope stability have been investigated. For this purpose, 60 theoretical models have been made which all of them have a specific block size distribution and VBP. These bimslopes are contained the blocks with different dips versus the face. Also for each kind of blocks orientation, 10 different blocks arrangements have been modeled. The Finite element method (FEM) have been used to analysis the stability of these bimslopes models. The results show the orientation of blocks have a strong impact on safety factor and stability of bimslopes. The obtained graphs from this study can be used in the projects are faced the bimslopes. 1. Introduction The behavior of soil and rock mass have been widely analyzed. Furthermore, some environments are included the rocky blocks randomly scattered in a soil mass which called bimrocks (block-in-matrix rocks). Several studies have been conducted to identify bimrocks (Medley, 1994; Riedmuller et al. 2001; Afifipour and Moarefvand; 2014). But there are still man y unknown aspects of bimrocks behavior such as the reaction in slope stability and tunneling issues. Two kind of bimrocks with different volumetric block proportion (VBP) in Iran are presented in Fig. 1. In this paper, the influence of blocks orientation on the stability of bimroc ks slopes (bimslopes) have been studied. For this purpose, the finite element method have been utilized. 2. Bimrocks The bimrocks are defined as mixtures of rocks composed of geotechnically significant blocks within a bonded matrix of finer texture such as melanges, fault rocks and weathered rocks (Medley, 1994).

Abstract In room-and-pillar mining method which is commonly adopted for underground limestone mine in Korea, the design of safety pillar is very important for securing a safety in mining operation as well as for preventing a collapse in roof. It is known that the stability of safety pillar in underground mine openings is mainly determined by characteristics of rock and discontinuities during mining process and also affected by time-dependent weathering characteristics of rock after completion of mining operation. For analyzing the effect of time-dependent weathering characteristics of rock on pillar stability, in this study, a freeze-thaw test for Poongchon limestone obtained from underground limestone mine has been implemented in temperature range of -18 ~ +4? for simulating the weathering process. Changes in physical and mechanical characteristics of rock and discontinuities are determined from artificial weathering test and used for numerical analysis on time-dependent pillar stability. 1. Introduction Mining methods are being changed recently from surface mining method to underground mining method, for reasons of increment of environmental issues in Korea. For underground mining operations, therefore, the room-and-pillar mining method has been commonly adopted in underground limestone mine in Korea. Considering a room-and-pillar method in underground limestone mine, safety pillar designing should be reflected on long-term stability and its weakening process should be also reviewed by chemical and physical weathering (Chatterji and Christensen, 1979; Goudie, 1999; Hanja, 2003; Park and Park, 2015). For analyzing the effect of time-dependent weathering characteristics of rock on pillar stability, in this study, a freeze-thaw test on Poongchon limestone from underground limestone mine was performed in temperature range of -18 ~ +4? for simulating the physical weathering process. The artificial weathering test by a freeze-thaw test deduced changes in several physical properties such as density, absorption, elastic wave velocity, shore hardness, and shear strength of rock mass. These results were used for numerical analysis on time-dependent stability of safety pillar.

Abstract The slope of interest, locates in southern Taiwan, has its dip direction approximately parallel with the cleavage of Mesozoic slate formation. The Ailiao River and three highway traverses over the slope at various elevations, leading to river bank erosion inevitably and artificial cutting with engineering stability measures. Typhoon Morakot in 2009 brought heavy rainfall and caused hazardous landslides. After that, sliding and deformation of the slope with various degrees were observed at different locations. This study investigates the influence of river bank erosion and artificial cutting on the sliding and deformation of the slope by several methods. Results of multi-temporal aerial image interpretation indicate that the case slope is stable with limited deformation while daylight is unobserved. Gully developed along the dip direction with some instable movement masses adjacently falling down occasionally. Deformations and propagation of rock discontinuities in different scopes of the slope that are sub zoned by daylights caused by artificial cutting and gullies differ from each other. Typhoon Morakot lead to slide of residual soil with shallow rock stratum of the study slope, and silt up of the Ailiao River. The river water may weaken the rock stratum and cause bank erosion at higher elevation than before, reducing stability of the study slope. Site investigation and monitoring results also reveal various evidences consistent with those mentioned above. 1. Introduction Deformation and associate stability of a slope are critical information for geohazard mitigation. Some slopes failure occur with limited monitored deformation before movement, while the other exhibits time-dependent deformation that is significant in magnitude, but unobvious sliding surface, for instance, gravitational induced deep-seated deformation. The understanding for deformation patterns and associated temporal variation for a slope is then paid high attentions recently.

Abstract Numerical modelling is widely used in the rock block displacement analysis because it has more capabilities than analytical-conventional methods. Numerical modelling is able to solve the case with a complex geometry, precise calculation more parameters and quick calculation time. The use of this method needs to be validated due to a mismatch between the conditions of the numerical model with actual conditions in the field. Numerical modelling is done by distinct element method and one of the numerical validation methods is physical modelling in a laboratory. The geometry of the physical modelling in the laboratory using rock slope model with plane failure type as rock block object which will fail and using cement material. Physical modelling will be given load behind the slope using a pendulum as a seismic load with some variation of angles and be placing vibration test device (minimate III) above physical modelling to record the value of vibration due to a load of a given. Each test will be obtained the value of block displacement and vibration value. Based on this research, the results of numerical modelling approach value of displacement resulting from physical modelling test in the laboratory. 1. Introduction Rock block displacement to be one of problem on rock mechanics and engineering. The analysis of rock block displacement are mainly related to many parameters, such as the geological structure, pore pressure, rock mechanical properties, seismic load, field stress, and other parameters. With the many parameters that are encountered, so it needs a calculation method that can calculate quickly and complex. The numerical method is one that can be used to solve this case because it would be very helpful to rock mechanic engineers in calculating and analyzing a rock block displacement or slope instability.

ABSTRACT: In this paper, the ANSYS software is used to simulate the effect of the surface blasting on underground chambers. The EH4 electromagnetic imaging system is employed to determine the different lithology and faults distribution of stratigraphy from roof to the ground, and the IDTS3850 tester to measure the blasting vibration data, then a linear fitting is used to analyze the particle vibration velocity attenuation law of underground chamber roof based on Sadowsky empirical formula. The LS-DYNA module of ANSYS software which provides explosive material model and JWL equation can simulate the blasting loads. The corresponding impact of blasting loads on the stability of chamber was assessed from the peak vibration velocity and stress by using Lagrange method and matched post-processing procedures LS-PREPOST. It is shown that the maximum vibration velocity in the surrounding the chamber is on the side face to the blast; under certain circumstances, although the surface blasting causes chamber displacement and wall caving phenomena, it does not affect the overall stability. 1 INTRODUCTION After decades of exploitation in our country, most of the open-pit mines nears the end, and transformation from open-pit to underground mining has become a trend. In order to realize the smooth transition to underground, maintain steady production scale and longer construction transition, most of the mines use the combined open pit-underground mining as the transition pattern. With the increase of underground mining, study on the stability of underground engineering is much important. Because of the complexity and uncertainty of the rock mass, it is difficult to obtain quite accurate geological conditions and the occurrence of environmental information before construction, so the general stability evaluation method of underground chamber like field measurement method, engineering analogy method and experience forecast method, etc. are difficult to completely solve the problem in engineering practice, thus, numerical simulation analysis of field monitoring measurement is very necessary (Li et al. 2003, Singh 2002, Cui & Chen 1999). In this paper, the ANSYS software is used to simulate the effect of the surface blasting on underground chamber, in which the 15-DYNA module can process kinds of complicated nonlinear problems, its practical algorithm is especially suitable for analysis of dynamic nonlinear problem, and it can successfully simulate the explosion process of numerous media and various blasting process (Xiao 2004).

ABSTRACT: The tertiary soft rock (or tertiary hard soil) is half-diagenetic rock (soil) and its properties are different from hard rock and soil. A lot of engineering practices show that the stability of thick tertiary soft rock slopes is affected seriously by underground water and rainfall. A high open-pit slope which is made up of super-thick tertiary soft rock is taken as a case, firstly the variation laws of the physical and mechanical parameters of the tertiary soft rock in this slope with different water content had been analyzed through drill hole sampling and laboratory testing. Then a fluid-solid coupling model had been established based on the limit equilibrium theory, finite element method and saturated-unsaturated seepage theory, to study the effect of seepage field caused by underground water and rainfall on the stability of the slope. The experimental and numerical results show that the cohesion of the tertiary soft rock is rather sensitive to water content but the internal friction angle is insensitive; the slope will be unstable in the present level of underground water, and only the depth of waterline is dropped for 100m can the slope be safe; both transient saturated zone and pore water pressure increase with longer duration of rainfall, but the heaviest rainfall can only lead to the shallow slope sliding within the thickness of 20 m and local rainfall has less impact on the whole slope stability. 1 INTRODUCTION The stability of slopes greatly affects the economic benefits and production safety of open-pit mines in the process of strip mining, so studies on open-pit slopes have always been the hot subjects. There have many research achievements on the issues of hard rock slopes, soft rock slopes and soil slopes in the field of open-pit mines, hydroelectric dams, highway and railway slopes etc (Naghadehi et al. 2013, Dine et al. 2011, Huang 2007). However, the tertiary soft rock (or called the tertiary hard soil) is a kind of half-diagenetic soft rock (soil) which is in the status from soil to rock, and at present there aren't targeted rules and enough research results for determining the bearing capacity of this kind of rock by existing different standards (Zhang & Qu 2000a). A lot of engineering practices show that the tertiary soft rock (soil) is a kind of regional special soil which is highly vulnerable to environmental changes (including the natural environment and engineering environment) and has significant drying shrinkage and water absorption expansion characteristics (Zhang & Qu 2000b, Feda et al. 1995).

ABSTRACT: From the viewpoint of tunnel stability, two proposed models are presented in this paper for estimating the minimum rock cover of a sub-water tunnel in the cases of homogeneous rock mass and inhomogeneous rock mass, which are based on the concept that minimum rock cover is obtained when support pressure at crown reaches to the minimum. The first model is based on the assumption that rock mass is homogeneous, where rock mass strength complies with Mohr-Coulomb failure criterion, while the latter is for inhomogeneous rock mass. Furthermore, comparison is made among the proposed models, Norwegian empirical curve and Japanese minimum water inflow model to estimate the thickness of the minimum rock cover. 1 INTRODUCTION Alignment of a sub-water tunnel is determined by geological and topographical conditions, as well as the tunnel's maximum gradient requirements, and minimum rock cover above tunnel crown. The minimum rock cover, defined as the minimum distance between the crown of a tunnel and the surface of bed rock under water (sea or lake), is a crucial dimension for the layout of a sub-water tunnel. Currently, two methods are popularly used in determining the minimum rock cover for planning a sub-water tunnel, one is Norwegian empirical curve which is founded on the basis of Nordic subsea tunnel construction practice (Dahle & Nilsen 1994, Palmstrom 1994 & 2002). The other is Japanese minimum water inflow model which has been applied in most of subsea tunnels in Japan and also in China (Li et al. 2007). In this paper, main works are emphasized on the following three subjects. Brief introduction of two popularly used determination methods; Basing on the concept of minimizing support pressure at crown, two models are proposed to be used in estimating the minimum rock cover for homogeneous rock mass and inhomogeneous rock mass, respectively; Comparison is made among these three determination methods.

ABSTRACT: Based on the theory of three-dimensional elastic-plastic seepage, the prediction of sandstone displacement and stress distribution law of the shaft frozen wall in Xiaozhuang Coal Mine was calculated. The prediction of sandstone displacement of frozen wall is performed by FEM numerical calculation. The results indicate that the biggest radial displacement was 2.036 × 10 −3 m when the thickness of frozen wall and roadway height were 2.5 m and 4 m, respectively, which could meet the requirements of safety regulations that the radial displacement should not exceed 50 mm and would not cause damage to the frozen pipe. The result showed that the design of frozen wall thickness and roadway height was proper, which can ensure the construction smooth. The actual monitoring data were basically consistent with predictive value. The study shows that FEM calculation could well predicate the radial displacement of frozen wall, and it is a quilt effective way of research to predicate stability of surrounding rock. 1 INTRODUCTION Freezing method is the main construction method which can make sure the wellbore across the unstable alluvium and weathering zone of bedrock and nearby the upper aquifer (Chen et al. 2000, Cui et al. 1998), freezing method construction can guarantee the working face anhydrous (Cui 2008). Frozen design must be aiming at the buried characteristics of alluvium and frozen rock mechanics characteristics, to meet the strength of the frozen wall, the deformation and water plugging requirements. At present the main problem of the freezing method construction is the frozen wall displacement is too large which leads to the broken of freezing pipe. Freezing method in general can be divided into the whole deep freezing method and the partial deep freezing method (Yao et al. 2005). Partial deep freezing method construction can avoid the damage, which the in-gate construction can easily produce the annular water channel by the frozen pipe and temperature tube, and the damage caused by the cavern rock (Zhao et al. 2012), and now non whole deep freezing method construction is been widely noticed (Yang et al. 2012). Xiaozhuang coal mine is the first to use the partial deep freezing method construction in northwest. In this paper, based on Xiaozhuang Coal Mine construction, research on the partial deep freezing method construction is carry out. By using of FEM software ABAQUS, following the process of the partial deep freezing method construction, the displacement law of the frozen wall, combined with the actual testing data analyze the stability of surrounding rock of the shaft frozen wall in rich water sandstone is analysed. The reasonable parameters for stability of surrounding rock of the shaft frozen wall in rich water sandstone formation is provided.

ABSTRACT: Rock structure is very important for the stability of rock slopes. RFPA is a professional finite element software for failure process analysis of material. RFPA-Centrifuge is used to simulate the failure process of rock slopes with a weak stratum which is in different height, the characteristics of the failure processes of the three dimensional-models and the factors of safety are gotten. The results showed that with the same mechanical parameters, the shorter distance between the weak stratum and the crest of slope is, the bigger the factor of the safety is and the smaller of the instability area is. Therefore, using software to simulate the failure process of slopes before the engineering excavation, different measures will be provided reference for supporting on rock slopes with weak strata. 1 INTRODUCTION Mostly rock mass at surface layer of earth had formed many structure planes with regular distribution in lengthy geological history. For rock slopes, stability analysis is difficult because there are so many discontinuity structure planes in rock mass, which has different construction and characteristic. Such as layer plane, joints, fracture, weak interlayer, vein, etc. Engineering rock mass has complex geological occurrence environment, the force conditions and border conditions are kaleidoscope, it's very difficult to express stress state and stability with classic mathematics mechanical method, this is restricted with the development of joint rock mass mechanics in a long time. The rapid development of computer technology changed this status, numerical calculation methods gradually became tools for rock mechanical research and engineering calculation. Weak strata are the weakness places in rock mass under dynamic loading conditions because of the lower modulus and strength, which is usually impact on the engineering projects. In recent years, the dynamical problem of rock slope with weak strata has caused widespread attention in the geotechnical engineering field (Huang 2007). Du Xiao-li (Duet al. 2010) discussed the relationship between the inclination of structures and slope stability by finite element method. Chai Hong-bao (Chai et al. 2011) studied the amplification rule of slope under the action of vertical upward shear wave. Huang run-qiu (Huang & Yu 2003) simulated the impact of magnified effect of earthquake wave with elastic-plastic parameters involving weak interlayer, and obtained the results that magnified effect is mainly related to velocity, not density.

ABSTRACT: In order to solve the surrounding rock damage problems of winch chamber in No. III I Mining Area of Yangzhuang Mine, such as, two sides getting closer, severe skin falling off the roof of pulp and serious floor heave, through the laboratory test, theoretical analysis and FLAC 3D numerical analysis, the failure mechanism of the surrounding rock is studied. The results show that weak surrounding rock layers, a lot of clay mineral components and unreasonable supporting structure and parameters were the immediate causes for the failure, the excavation of old roadway around the winch chamber was the indirect cause, which provided scientific theory basis for the repair of the winch chamber and can be applied to the repair of similar mine chamber damage. 1 INTRODUCTION The winch chamber in No. III I Mining Area of Yangzhuang Mine was founded in 2006 bearing the III I Mining feeding task and discharging gangue. Since October 2010, field workers have found that there were some cracks in the winch chamber accompanied by stagging off, this phenomenon was particularly fiercer in March 2012. The layer of winch chamber roof fell off seriously, causing tuck net phenomenon obviously with reinforced metal mesh tearing and steel strip breaking. As shown in Figure 1, the floor heave of winch chamber became serious, leading to a serious distortion, and making the winch can't use normally. In order to ensure safety production and avoid the passive situation of the heavy casualties and the stagnation of production, we must study the failure mechanism of winch chamber and adopt comprehensive and effective measures to control it. The failure mechanism was complex. Many researchers at home and abroad have made a lot of researches and have gained great achievements on listening comprehension studies. Manchao He and Xiaoming Sun etc (He et al. 2002, He et al. 2004, Jiang et al. 2005, Jia 2006) put forward a standpoint that weak surrounding rock layers has a great influence on the stability of surrounding rock by analyzing the structure of surrounding rock. Lijun Han (Wang et al. 2005, Li et al. 2012) studied the influence on the stability of surrounding rock and concluded that high content of clay mineral composition was easy to cause damage of surrounding rock.

ABSTRACT: The starter dam of a tailings pond, adopted sectional construction, might cause differential settlement, which will bring bad impact on the dam stability during use later. First, the deformation rate of starter dam was monitored by INSAR technology for 14 hours, which demonstrated that the nonuniform deformation rate was within the permissible security range. Secondly, by means of numerical calculation, simulating the real conditions of sequence of sectional construction, studying the distribution and the change relationship of the starter dam deformation along with the construction steps, it was concluded that the numerical calculation results mostly coincided with the monitoring results on both the whole settlement and uneven settlement distribution of the starter dam. At last, considering the real situation of tailings pond in the later use, the stability of the starter dam was analyzed under the fluid-structure interaction. The results show that the starter dam could remain stable during construction and later use. 1 OVERVIEW Tailing pond, damming the valley mouth or compound, is used for storage of ore tailings or industrial waste, which is produced by metal and nonmetal mines after beneficiation. Tailing pond is a major hazard with high potential of man-made debris flow, once the dam breaks, it will cause great disaster follows by great losses. Operational tailing ponds are not only related to the mine's own safety and economic benefits, but also closely related to the lives and property of the downstream residents and their surrounding environment (Ma et al. 2010, Xie et al. 2009). The security and stability of starter Dam with Section Construction plays a vital role for the safe operation of tailing pond. Therefore, the starter tailing dam stability monitoring and analysis are of great significance.

ABSTRACT: With the aim to overcome the difficulty of determining the reasonable cutting height, the influence factors of determining the cutting height were analyzed in detail. Combined with the Panel 30101 of some mine, the stability of coal wall, the working resistance of support, the top-coal migration and recovery at different cutting height are studied by using numerical simulation and field practice. The result shows that the stability of coal wall, the support working resistance, top-coal migration positively correlate with the cutting height, which is not a linear relation, with the increase of cutting height, the top-coal recovery shows a trend of increases first and then decrease. Overall considering that the stability of coal wall, the working resistance of support, the top-coal migration and recovery, the determination a cutting height of 5 m for the Panel 30101 is reasonable. With the development of the large cutting height mining and top-coal caving theory and techniques, as well as the improvement of fully-mechanized equipment, the extremely-thick coal seam is increasingly considered to be mined by top-coal caving with great mining height. And this mining method positively combines the advantages of large cutting height mining and top-coal caving. To be exact, it is relatively lower-cost, more efficient and more productive. As a result, it is the best choice for extremely-thick coal seam (Cao 2008). However, the development of top-coal caving with great mining height is restricted because of low top coal recovery rate, rib spalling, adaptability of support and great amount of gas emission, and all these factors have something to do with cutting height (Wang 2005, Yan & Yin 2008, Yan & Yin 2008). The cutting height is therefore the key to achieve safety, high productivity and efficiency for top-coal caving with great mining height. Many studies have been done to obtain a appropriate cutting height in the past few years. Article (Liu 2011) investigated the relationship between cutting height and gas emission through numerical simulation, indicating that the gas density decreases as the cutting height increases. Article (Xia & Kang 2008) studied the influence of cutting height on rib stability, demonstrate the increase of cutting height results in the deterioration of rib spalling.

ABSTRACT: According to the typical conditions of special water preserved mining area, the aquiclude stability with two equispaced filling strips is analyzed by using the physical simulation experiment and theoretical analysis, and the mechanical model of elastic foundation beam of strip filling aquiclude strata is set up. Based on that, the calculation method of load and the compression displacement of the filling strip is presented, and the deflection formula of the water resisting beam is given, and the position and depth of the downward crack is determined. Based on the aquiclude stability criterion, the calculation method of reasonable filling strip width and interval width is put forward. The result shows that the reasonable strip interval increases with the increase of the mining height, the thickness and strength of the beam, and the depth of the downward crack is mainly relate. 1 INTRODUCTION There are rich shallow buried coal seams in the Western China, and the coal reserves and production are among the forefront (Huang 2002). The water preserved mining is an urgent and frontier research project of shallow coal seam mining (Qian et al. 2003). Our study shows that the stability of aquifuge is related with the mining height and aquiclude thickness. Based on the study of dynamic fracture of overburden, the aquiclude stability criterion have setup, and the water preserved mining classification have put forward according to the geological conditions of Yushenfu coal field (Huang 2010, Wang et al. 2010). Among them, the overburden aquiclude thickness less than 18 times mining height is named special water preserved mining, and the aquiclude rock group will be completely in the water flowing fractured zone after roof caving mining. For this case, it needs to take filling mining method to realize water preserved mining.

ABSTRACT: Layered rock slope failure is a vital problem in the geotechnical engineering. Based on the equivalent continuum and the compound material mechanics, the layered rock mass is treated as an anisotropic elastic medium. Then, the failure modes of slopes with layered rocks have been studied by numerical simulation using COMSOL software. Numerical results show that the damage zone of the slope first increases then decreases with the increase of layered structural plane angle θ. When θ = 30°, the slope is most easily to destroy. Moreover, the proposed numerical method is applied in Sijiaying iron mine and the results are in good agreement with the actual failure. The successful application shows that the proposed method is reasonable and feasible for the simulation of failure modes of such layered rock slopes. 1 INTRODUCTION Layered rock slope failure is a vital problem in the geotechnical engineering, and the research for layered rock slope failure mode is a major issue of realistic significance (Xian 1989). Many methods are used to understand the failure of slopes, each one having its own merits as well as limitations. The stability of large rock slopes, which are susceptible to rock mass failures, can be analyzed by traditional limit equilibrium methods (Bishop 1955, Janbu 1954) based on assumptions regarding the inclination and location of the interstice forces. For many cases, the limit equilibrium methods have proven to give convincing results despite its limitations. However, to identify failure modes of slopes using the traditional limit equilibrium methods, a range of specified slip surfaces need to be given to simulate the safety factor and the minimum will be recognized as the final slip surface (Baker 1980). This method is not convenient and accurate for rock slope engineering due to the heavy work and randomness in choosing slip surfaces. The conventional numerical modeling has been developed and has become increasingly popular for complex slope stability analysis. Application of numerical simulation is increasing due to many advantages over limit equilibrium method. A number of landslide studies have been carried out using numerical simulation (Singh et al. 2008, Kripamoy et al. 2012). However, these studies have been done always based on that rock mass per se is still simply treated as isotropic material.

ABSTRACT: The body structure type of layered structure in 11-B area of north slope was identified and classified based on the background of Shuichang Iron Mine high-steep slope. The generalized model of slope was established in this region and internal stress and displacement distribution features of reverse layered soil-rock aggregate dualistic structural slope were analyzed, through the main failure mode of this kind of slope was obtained and the high-steep slope stability in 11-B area for dynamic excavation on condition of complex tectonic stress field was analyzed emphatically. The results indicated that: 1. The dual structure of earth-rock aggregate slope was classified according to the relationship between slope strike of dualistic bedrock structure and rock strata. It was helpful to improve the accuracy for generalized slope model identification. 2. On the slope surface and the top of the slope with reverse layered dualistic soil-rock structure, the maximum principal stress paralleled to its face and the minimum principal stress went perpendicular to its face. The minimum principal stress would change to tensile stress when it went beyond zero. The phenomenon of the stress concentration appeared at toe of the slope. The maximum principal stress value increased prominently along the tangent slope foot. The minimum principal stress value significantly reduced and even changed to the tensile stress along the radial direction. The maximum horizontal displacement occurred at top of slope surface. The landslide type was more prone to bending toppling destruction. 3. In the whole mining process, the influence range of slope excavation developed simultaneously along the slope surface direction and perpendicular to the slope surface direction, and formed a circular destruction at the bottom of slope surface. The slope can fail easily if it is covered with hard rock. Moreover, when shear outlet consisting of the mudstone and weak rock that are located near the slope edge, the overlying loose layers slides more easily. 1 INTRODUCTION Soil-rock aggregate means a kind of geological body containing unique engineering geological characteristics and mechanical properties between soil mass and rock mass (Wu 2012).

ABSTRACT: It has wide distributions and large recoverable reserves of Jurassic period coal seam in China. It is difficult to maintain stability of the development roadways with long service term for Jurassic strata because there are abundant argillaceous rocks and some minerals in the high argillaceous rocks will be expanding while meeting with water. The fractures of the roadways develop well under high stress and are suitable to filling with grouting. But the poor cementing performance of cement with argillaceous rock as well as a heavy water filtration rate of cement slurry had resulted in failures of many engineering cases adopting cement grouting to reinforce this kind of roadways. In this paper, according to characters of the high argillaceous rock in Jurassic strata, a marlaceous inorganic grouting material which possesses the well cementing performance with argillaceous rocks and little filtration rate was introduced; and the grouting reinforcement mechanism, construction technique and engineering application effect about it was clarified. It will be of great significance for reinforcement and maintenance of the development roadways with high argillaceous rocks. 1 INTRODUCTION According to statistics, 60% of the proved coal reserves in China distributes in Early-Middle Jurassic period of northern North China, southern Northeast China and Northwest China, along with late Jurassic to early Cretaceous period of Northeast China and east Inner Mongolia. The period of coal forming is short and argillaceous rocks are abundant in Jurassic strata. Moreover, there are quite a few expanded minerals in some strata. So the roadways are easily to be deformed and damaged when affected by mining-induced stress. In addition, this kind of soft rock roadways has an obvious time effect. For the development roadways with long service term, serious deformations are frequently observed and part of the roadways has suffered deformation and maintenance time after time. The stability support of the development roadways really need much cost.

ABSTRACT: Bolt and wall rock should be regarded as a whole in the tunnel stability analysis. Based on the principle of bolt-rock combined action, a monitoring system of bolt stress and wall rock strain was developed, and a judging standard for the warning level of the rock stability was put forward, including the rock movement, rock moving velocity, rock moving acceleration, and the stress variation rate of bolt. The method was used in the PanGuShan mine, and an early-warning was made for some dangerous area. Based on the data acquisition of stress and strain of bolt, the system realized online monitoring by underground wireless transmission, it would be useful for the prevention of ground pressure disaster. 1 INTRODUCTION Pangushan Bismuth & Tungsten Mine is the only production site of Pangushan Jiangxi Tungsten Industry Co., Ltd. The Mine is located 33 kilometers south of the city of Yudu County, Jiangxi Province, and it's under the administrative jurisdiction of Pangushan Town in Yudu County of Jiangxi. Composed by three sets of veins, the mine is developed with joints, and there are seven groups of distributed faults. In June 1966 and July 1967, destructive activities of ground pressure occurred in the upper part of the mine, causing serious losses. After it was converted to deep mining since the 1990s, ground pressure activities occurred frequently, and in the mid-sections of 535 m-485 m and 485 m-335 m, the active blocks in vertical goaf are big enough to pose serious threats. Based on the above, anchorage supports were adopted to places that may affect the stability of rocks in Pangushan tungsten mine, reinforced by security rock pillars and other methods. At the same time, the ground pressure of key areas was monitored through sophisticated methods. By analyzing the monitoring data of Pangushan tungsten mine, a complete set of system for monitoring and warning ground pressure has been developed and it is of great significance for preventing harms caused by ground pressure.