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Roof bolting has been used in underground entry (roadway) support in U.S. coal mines since the Coal Mine Health and Safety Act of 1969 (US Congress, 1977) recognized roof bolting as the only means of underground entry (roadway) support. For U.S. underground coal mines, roof bolting pattern is fixed at 4 × 4 ft (1.2 × 1.2 m), except in the Pittsburgh Seam where longwall mining is practiced, with occasional 3.6 × 4 ft (1.1 × 1.2 m) pattern. However, roof falls or roof failure often occurs in roof-bolted entries in U.S. coal mines. Roof falls can roughly be divided into four types: skin falls, large falls, cutter roofs, and massive falls. Based on this situation, the roof is initially strengthened by bolt based on suspension and friction mechanism. By comparing roof bolting patterns in different coal producing countries, bolt density in all other countries is much higher (except South Africa) than that used in the U.S. In spite of its long history of successful application with hundreds of millions of units installed, roof bolting design is still the lack of a commonly accepted method. [ABSTRACT FROM AUTHOR]

The prediction of roof convergence in mining area plays an important role in effectively preventing roof accidents and ensuring the safety of mine production. Because the roof pressure in the mine is affected by various natural and human factors, and there is a dynamic and fuzzy nonlinear relationship between the factors. At present, the lack of systematic management will seriously limit the analysis and judgment of the mine safety situation and lead to the occurrence of mine accidents. Strata control instrumentation and monitoring aim at the evaluation and monitoring of the trends of changing rock mechanical parameters such as dilation, load, convergence, stress and axial loading during mining. The objective of this paper is to provide an insight about the monitoring and analysis of convergence in underground coal mines. Also, it provides a comprehensive view of occupational accidents happened in mines along with the roof convergence and risk factors. Finally, the performance analysis of roof convergence rates is analysed. [ABSTRACT FROM AUTHOR]

Abstract A variation of direct velocity feedback, often referred to as skyhook damping, is discussed in this paper. Skyhook damping cannot be regarded as collocated control method since only the action force component is collocated with the velocity sensor mounted onto the receiving part of the structure. The reaction control force component reacting off the source part of the structure does not have a collocated sensor. Depending on the characteristics of the passive structure under control, the feedback loop may be quite insensitive to the effects produced by the non-collocated reaction control force component, and maintain stability properties that are otherwise characteristic only for collocated control. Moreover, there exist additional effects related to the response of structures activated by the application of skyhook damping. It is shown in this paper that the structure subjected to such active control, although exhibiting stable response and linear input-output relationships, no longer complies with the reciprocity principle. The absence of reciprocity is interesting given the recent efforts in developing metamaterial cloaks, where one of the critical issues is how to design material structures or systems that demonstrate non-reciprocal behaviour. [ABSTRACT FROM AUTHOR]

High capacity longwall technology introduced at Adriyala longwall project with a rated capacity of 3.0Mt per annum. Huge machinery required to be installed in longwall face and gate roads. This machinery required wider gate roads of 5.2 to 5.5m widths. The immediate roof in gate roads is coal with thicknenss of 4.0mtr. Immediate roof consists of 2 clay bands of 0.3m and 0.7m thickness within the bolted and above the bolted horizon causing bed separation in the immediate roof, resulted in that, during development of gate roadways, 85% of roadways are good in condition, 15% of gate roads were observed with guttering, geological disturbances, water seepage, and in some areas horizontal stress effect is also noticed. While retreating of longwalls, major disturbances were observed in gallery ahead of the longwall face, and also in cut through galleries and adjacent gate roads subjected to abutment loading. To overcome the above issues, Pre-tensioned bulbed type cable bolting is introduced first time in India as secondary support in gate roads of longwall panel to ensure its stability over long period and also to eliminate standing support in gate roads ahead of the longwall face. In this paper, the installation and performance of bulbed type cable bolt is discussed in detail. [ABSTRACT FROM AUTHOR]

Over the past few decades, several semi-active controllers have been proposed for vehicle suspension systems. Skyhook and groundhook controllers are well-studied and very effective in isolating vibrations. However, these controllers mitigate either the sprung or unsprung mass response at the expense of the other. Moreover, there is no sensor to directly measure the absolute velocity of components in the suspension system (and estimates are subject to error), making it challenging to implement skyhook and groundhook controllers in practical cases. To overcome these limitations, there is a need for a type of damping that mitigates both sprung and unsprung mass responses and also can be implemented using simple local sensors. This paper proposes the use of rate-independent linear damping (RILD) for vehicle suspension systems. RILD provides direct control over displacement; beneficial for low-frequency dynamic systems such as suspension systems that are subject to high frequency vibrations (relative to the system fundamental natural frequency). RILD directly attenuates displacement responses with low damping forces, producing low acceleration responses. The RILD damping force is proportional to the displacement advanced in phase π/2 radians, which makes it noncausal. In this study, a modal causal filter-based approach is proposed to mimic the ideal noncausal response of the RILD model. Acceleration measurements of the sprung mass are used with a Kalman filter to estimate the displacements needed for the algorithm. Numerical analyses were conducted to demonstrate performance of the proposed model in matching noncausal RILD responses. Additionally, the advantages of the proposed model over well-known skyhook and groundhook controllers are studied. [ABSTRACT FROM AUTHOR]

Canopy air curtain (CAC) technology has been developed by the National Institute for Occupational Safety and Health (NIOSH) for use on continuous miners and subsequently roof bolting machines in underground coal mines to protect operators of these machines from overexposure to respirable coal mine dust. The next logical progression is to develop a CAC for shuttle cars to protect operators from the same overexposures. NIOSH awarded a contract to Marshall University and J.H. Fletcher to develop the shuttle car CAC. NIOSH conducted laboratory testing to determine the dust control efficiency of the shuttle car CAC. Testing was conducted on two different cab configurations: a center drive similar to that on a Joy 10SC32AA cab model and an end drive similar to that on a Joy 10SC32AB cab model. Three different ventilation velocities were tested—0.61, 2.0, 4.3 m/s (120, 400, and 850 fpm). The lowest, 0.61 m/s (120 fpm), represented the ventilation velocity encountered during loading by the continuous miner, while the 4.3 m/s (850 fpm) velocity represented ventilation velocity airflow over the shuttle car while tramming against ventilation airflow. Test results showed an average of the dust control efficiencies ranging from 74 to 83% for 0.61 m/s (120 fpm), 39%-43% for 2.0 m/s (400 fpm), and 6%-16% for 4.3 m/s (850 fpm). Incorporating an airflow spoiler to the shuttle car CAC design and placing the CAC so that it is located 22.86 cm (9 in.) forward of the operator improved the dust control efficiency to 51%-55% for 4.3 m/s (850 fpm) with minimal impact on dust control efficiencies for lower ventilation velocities. These laboratory tests demonstrate that the newly developed shuttle car CAC has the potential to successfully protect shuttle car operators from coal mine respirable dust overexposures. [ABSTRACT FROM AUTHOR]

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To improve the switching time of the control force in standard sky-hook ON-OFF semi-active control algorithm, a state-adjust coefficient was adopted in the improved ON-OFF (ION-OFF) algorithm. In considering of the riding comfort and the handling stability of vehicle, a comprehensive performance assessment criterion on suspension system was established with the utilization of the corresponding passive suspension system. Several simulations and analyses were conducted on improved ON-OFF semi-active suspension system with the comparison of passive suspension system and ON-OFF semi-active suspension system. The simulation results showed that the optimal comprehensive performance of the improved ON-OFF suspension system could be achieved when the state-adjust coefficient equalled 0.6 as the vehicle running on C level road with the speed of 10 m/s, and the comprehensive performance was better than ON-OFF suspension system. Conclusions could be drawn from the frequency domain analysis that the performance of riding comfort and handling stability were both improved in the low resonance frequency and the mid-frequency range. The fact could be known that the comprehensive performance of the suspension system was associated with the frequency of the riding road and the sprung mass (SM) with the analysis of affecting factors. [ABSTRACT FROM AUTHOR]

Sky-hook damping is one of the most promising techniques for feedback control of structural vibrations. It is based on the idea of connecting the structure to an ideal fixed point of the space through passive dissipative devices. Herein the benefit of semiactive (SA) sky-hook (SH) damping is investigated for seismic protection of a two-storey steel frame via shaking table tests. This kind of SA control is achieved implementing a continuous monitoring of selected structural response parameters and using variable dampers. The damping properties of the latter are changed in real-time so as to make the force provided by the damper match the desired SH damping force as closely as possible. To this aim, two prototype magnetorheological dampers have been installed at the first level of the frame and remotely driven by a SH controller. The effectiveness of the control strategy is measured as response to reduction in terms of floor accelerations and interstory drift in respect to the uncontrolled configuration. Two different calibrations of the SH controller have been tested. The experimental results are deeply discussed in order to identify the optimal one and understand the motivations of its better performance. [ABSTRACT FROM AUTHOR]

This paper is concerned with the comfort-oriented vehicle suspension design problem by using a skyhook inerter configuration. The rationale of the skyhook inerter is to use a grounded inerter to virtually increase the sprung mass of a vehicle, as it is analytically demonstrated that increasing the sprung mass can always improve the ride comfort performance. Semi-active means to realize the skyhook inerter configuration are investigated by using semi-active inerters. Three control laws, that is the on-off control, the anti-chatter on-off control, and the continuous control, are proposed for the semi-active inerter to approximate the skyhook inerter. Numerical simulations are performed to demonstrate the effectiveness and performances of these control laws. It is shown that the semi-active realizations of the skyhook inerter by using the proposed control laws can achieve over 10% improvement compared with the traditional strut, and similar performances are obtained for these control laws, with slight differences with respect to different static stiffnesses of the suspension system. [ABSTRACT FROM AUTHOR]

The efficiency of vibration control in an automotive semi-active suspension system depends on the quality of information from sensors installed in the vehicle, including information about deflection of the suspension system. The control algorithm for vibration attenuation of the body takes into account its velocity as well as the relative velocity of the suspension. In this paper it is proposed to use the Linear Variable Differential Transformer (LVDT) unit to measure the suspension deflection and then to estimate its relative velocity. This approach is compared with a typical solution implemented in such applications, where the relative velocity is calculated by processing signals acquired from accelerometers placed on the body and on the chassis. The experiments performed for an experimental All-Terrain Vehicle (ATV) confirm that using LVDT units allows for improving ride comfort by better vibration attenuation of the body. [ABSTRACT FROM AUTHOR]

In general, underground mine/tunnels/roadways are supported especially in India, by using wooden cogs/props as support in addition to the massive use of roof bolting. But as wood is becoming scarce, there is need for suitable alternative supports to replace timbers in mines. Keeping in mind the Indian mining condition the support should be of greater longevity, light enough for easy portability and requiring less maintenance. Further, it should have facilities for height variation, sufficient yielding, continuous load monitoring and releasing remotely as the coal seam thickness varies widely in Indian mines. Then, the support material must be easily available and should have ease in operation by even an unskilled worker. Finally, the device must be economically viable for Indian mines, which is thriving for its longer life and should provide safety for miners. In this direction several efforts have been made to design such slow loading yielding props to meet all these requirements. After numerous attempts such innovative prop consisting of multiple disc springs has been designed and developed at CSIR-CIMFR of which the details description has been discussed in this paper. [ABSTRACT FROM AUTHOR]

Copyright of Scientific Bulletin of National Mining University is the property of National Mining University, State Higher Educational Institution and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Scientific Bulletin of National Mining University is the property of National Mining University, State Higher Educational Institution and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Dust generated from bolt hole drilling in roof bolting operation could have high quartz content. As a dust control measure, vacuum drilling is employed on most of the roof bolters in US underground mines. However, fine rock particulates from drilling could escape from the dust collection system and become airborne under some circumstances causing the roof bolter operators expose to quartz-rich respirable dust. A previous research shows that drilling can be controlled through properly selected penetration and rotational rates to reduce the specific energy of drilling. Less specific energy means less energy is wasted on generating noise, heat and over-breakage of rock. It implies that proper control of drilling has a great potential to generate significantly less fine rock dust during drilling. The drilling experiments have been conducted to study the effect of controlling drilling on reducing respirable dust. The preliminary results show that the size distributions of respirable dust were different when controlling drilling in different bite depths. This paper presents the findings from laboratory experimental studies. [ABSTRACT FROM AUTHOR]

Investigations have shown that human error is the most common cause of roof bolting injuries. Human error probability estimation has become a critical issue for human reliability analysis (HRA) of roof bolting operation. Specialist judgment plays a crucial role in quantifying human error probability in the field because of limited availability of empirical data. However, the aggregation of specialist judgment is typically not carried out in a formal way in HRA. In this paper, an approach to combine Bayesian methodology and the success likelihood index method was to build a computable model using information from specialists for HRA of roof bolting operation. A numerical example was used to illustrate the application of the proposed methodology. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In mine roadway support operations, floor bolting not only played a role in floor heave control, but also in reinforcing roof and its two sides. Correspondingly, bolting of roof and two sides also played a part in floor heave control. To quantify the effect of such bolting, based on roadway support in extremely weak rock, three physical models were produced and tested in laboratory. Through comparison of their displacements in three physical simulation experiments, the reinforcing effect of bolting in extremely weak rock roadways was quantified. Reinforcing coefficients was defined as displacement ratio between original support and new support regime. Results indicated that the reinforcing coefficients, for bolting of roof and its two sides, on floor, two sides, and roof reached 2.18, 3.56, and 1.81 respectively. The reinforcing coefficients for floor bolting on floor, two sides, and roof reached 3.06, 2.34, and 1.39 respectively. So in this extremely weak rock, the surrounding rock should be considered as an integral structure in any support operation: this allows for better local strength improvement, and provided future design guidance. [ABSTRACT FROM AUTHOR]

Among all United States underground coal fields, those in Illinois have the highest rate of roof fall events due to their weak and severely moisture sensitive roof rock units. Rockmass characterization is the key initial step in designing safe and economical roof control measures in underground coal mines. In this study, a performance-based roof rockmass characterization is investigated. The geologic conditions as well as underground mine geographic specifications, roof fall analysis, mining method, utilized supplemental roof control measures, and geotechnical properties of roof rock units were considered to link the roof performance to rockmass characterization. The coal mine roof rating (CMRR) rockmass characterization method was used to evaluate the roof conditions and roof support design for an underground coal mine located in the Illinois Coal Basin. The results of several mine visit mappings, laboratory test results, and geotechnical issues and concerns are presented and discussed. The roof support designs are analyzed based on the rockmass characterization and are compared with the observed performance. This study shows that (1) CMRR index is a reasonable method for characterizing roof rockmass; (2) moisture sensitivity and bedding strengths in the horizontal direction are essential parameters for roof support design in mines with weak roof conditions; and (3) the applicability of the analysis of roof bolt system for roof support design of the studied mine is questionable. [ABSTRACT FROM AUTHOR]

Bolt installation quality is influenced by various factors, some are well known and others are less recognised. A programme of field and laboratory studies was undertaken to examine various factors of relevance to the load transfer mechanism between the bolt, resin and rock to ensure test methods truly represent field performance. Short encapsulation tests were undertaken as part of the Australian Coal Association Research Program (ACARP) funded project (C21011) with the ultimate aim of developing standard test methods for assessing bolt encapsulation with chemical resin anchor installations. The field study consisted of a series of Short Encapsulation Pull Tests (SEPT) carried out in three mines with different geological conditions to determine the most representative and practical method of SEPT. Additional field work included installation of bolts into threaded steel tubes for subsequent removal and laboratory evaluation. A series of pull tests was carried out by installing bolts in overhead rig mounted sandstone block, cast in concrete with controlled encapsulation length. Factors of importance considered included; borehole diameter, resin annulus thickness, installation time (including bolt spin to the back and 'spin at back'), the effect of gloving and hole over drill. It was found that the borehole diameter had a detrimental effect on the encapsulation bonding strength. Bolt installation time of approximately 10 s constituted an acceptable time for effective bolt installation and within the resin manufacturers recommended time of 14 s. Maintaining constant length of encapsulation was paramount for obtaining consistency and repeatability of the test results. Finally, a numerical simulation study was carried out to assess the capabilities of FLAC 2D software in simulating the pull testing of rock bolts. [ABSTRACT FROM AUTHOR]

Copyright of Scientific Bulletin of National Mining University is the property of National Mining University, State Higher Educational Institution and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In underground mining, many miners are injured or lose their lives because of roof/pillar instability each year, and this is a persistent safety risk. Characterization of overlying strata is important for the design of safe and cost-effective ground support systems. Entry roof characterization can be performed by geological back-mapping of the ground using various methods such as geophysical logging, borescoping, rock mass rating, and intelligent roof bolt drilling systems. This paper offers a brief review of mine roof characterization methods, followed by an introduction to and discussion of roof characterization methods using instrumented roof bolters. A brief overview of the various instrumentation systems developed for roof bolt drills is presented. The results of the preliminary study and initial testing indicate that, despite recent improvements in the area of ground characterization by instrumented drills, there are still several issues that must be addressed to improve the efficiency and accuracy of existing systems. A summary of suggested improvements is provided. [ABSTRACT FROM AUTHOR]

In 1948 roof falls were the number one killer of coal miners in America. While the Bureau of Mines had been formed in 1910 to improve coalmine safety, it had largely focused on explosions, for which technological solutions appeared to exist. Roof falls, by contrast, were not amenable to a technical fix. Beginning in 1948, however, the Bureau discovered roof bolting, which it promoted as a safer technology that might yield dramatic benefits. The new approach spread rapidly, yet fatality rates from roof falls failed to decline for nearly two decades. This lag reflected the need for organizational learning, while companies also traded safety for productivity. Finally, only larger mines employed bolting and its impact was masked by a growth in the employment share of small companies. After 1965, as the expansion of small mines ended and organizational learning continued, fatality rates began a long decline. [ABSTRACT FROM AUTHOR]

Copyright of Scientific Bulletin of National Mining University is the property of National Mining University, State Higher Educational Institution and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The excavation and production in underground mines are complicated processes which consist of many different operations. The process of underground mining is considerably constrained by the geometry and geology of the mine. The various mining operations are normally performed in series at each working face. The delay of a single operation will lead to a domino effect, thus delay the starting time for the next process and the completion time of the entire process. This paper presents a new approach to the process control for underground mining operations, e.g. drilling, bolting, mucking. This approach can estimate the working time and its probability for each operation more efficiently and objectively by improving the existing PERT (Program Evaluation and Review Technique) and CPM (Critical Path Method). If the delay of the critical operation (which is on a critical path) inevitably affects the productivity of mined ore, the approach can rapidly assign mucking machines new jobs to increase this amount at a maximum level by using a new mucking algorithm under external constraints. [ABSTRACT FROM AUTHOR]

Skyhook technology is widely used in vibration control. However, it only attenuates vibration near the resonant frequency. To enhance the control performance of an isolation system, a new feedforward compensation control strategy, achieved by measuring base velocity with a geophone, is proposed in this paper. Firstly, the mathematical model of single degree-of-freedom pneumatic spring is derived in detail. Secondly, the feedback controller is designed experimentally, and an anti-windup proportion-integral controller is used. Thirdly, the feedforward compensation controller is designed using a finite impulse response filter, whose coefficients are updated on-line using the filtered-x least-mean-square algorithm with improved gradient estimate. At last, a series of experiments were conducted, and the velocity attenuation rate is calculated. The results of these experiments prove that the proposed method can greatly reduce base disturbance, and keep a high vibration velocity attenuation rate at all frequency points. [ABSTRACT FROM PUBLISHER]

This paper deals with finding the optimum parameters of a damped dynamic vibration absorber (DVA) to control chatter in metal cutting systems. The performance of conventional damped DVA is compared with the proposed skyhook damper in which the damper of the absorber system is connected between the absorber mass and an inertial reference in the sky, referred to as a skyhook damper. The damped DVA is optimized by reducing the magnitude in the positive side and increasing it in the negative side of the real part of the frequency response function of the main system. The optimum frequency ratio and the damping ratio of the damped DVA for the undamped and damped main system are obtained using analytical solutions and a numerical optimisation technique, viz genetic algorithm, respectively. The performance of the proposed skyhook damper is marginally better than the conventional type of damped DVA in controlling the vibration of the main system. This is verified by analyzing both the proposed and conventional models using finite element method-based commercial software ANSYS. [ABSTRACT FROM PUBLISHER]

In the present study, we investigate a control mechanism that dampens hand vibrations. Here, we propose a control method with two components to suppress hand vibrations. The first is a passive suppression method that lowers the joint stiffness to passively dampen the hand vibrations. The second is an active suppression method that adjusts an equilibrium point based on skyhook control to actively dampen the hand vibrations. In a simulation experiment, we applied these two methods to dampen hand vibrations during the shoulder’s horizontal oscillation. We also conducted a measurement experiment wherein a subject’s shoulder was sinusoidally oscillated by a platform that generated horizontal oscillations. The results of the measurement experiments showed that the jerk of each part of the arm in a task using a cup filled with water was smaller than the shoulder jerk and that in a task with a cup filled with stones was larger than the shoulder jerk. Moreover, the amplitude of the hand trajectory in both horizontal and vertical directions was smaller in a task using a cup filled with water than in a task using a cup filled with stones. The results of the measurement experiments were accurately reproduced by the active suppression method based on skyhook control. These results suggest that humans dampen hand vibrations by controlling the equilibrium point through the information of the external workspace and the internal body state rather than by lowering joint stiffness only by using internal information. [ABSTRACT FROM AUTHOR]

In this paper, the impact dynamics of rock bolt with passive friction control is modeled. Numerical investigations are performed for the bolts with frictional energy absorber under various dynamic loads. The results are compared with those from fully grouted rigid bolts. The studies indicate that without the frictional energy absorber, the bolts are highly susceptible to failure under dynamic impact loads, while the bolts with the fictional energy absorber significantly reduce this risk. The studies also reveal that the bolt sliding may occur at the combined effect of vibration frequency and velocity magnitude. Sliding will only initiate above certain threshold value defined by vibration frequency and velocity magnitude. Furthermore, the simulation results show that under certain impact forces when rock mass subject to only elastic deformation, bolt sliding may occur causing the detachment of bolt head and rock face, which may incapacitate the rock bolt in supporting the rock excavation. The investigation signifies that further development and appropriate design of the rock bolt system with a frictional energy absorber are critical in maintaining stability under dynamic loading. [ABSTRACT FROM AUTHOR]

The application of a rock bolting system for Indonesian underground coal mines has been attempted for several years without any success. Recently, two new underground mining trials were conducted in East Kalimantan, Indonesia, in order to investigate the possibility of using rock bolting to address the technical challenges of underground coal mines under weak geological conditions. Unfortunately, one of the trials failed and was given up due to a fatal roof fall accident. However, in another trial, even though roof falls have occurred within the working area, the bolted roadways showed reasonable stability over time. Moreover, a comprehensive monitoring system has been installed in order to monitor the ground behaviour and its characteristics. This application of a comprehensive monitoring system has enhanced the ability to increase the level of support and to react to changing/deteriorating conditions. This paper describes the conditions and geotechnical issues for underground mines in Indonesia, and discusses the applicability of the rock bolting system to address problems associated with weak strata conditions in Indonesia. [ABSTRACT FROM AUTHOR]

A passive realization method was presented for ideal skyhook damping to solve the technical prohlem in connecting the damper with the inertial reference system. This method takes the anti-resonance phenomenon in the inerter-spring-mass system. The passive realization method of ideal skyhook damping was applied to the vehicle suspension. A half-car model of passive skyhook-damping suspension was built to analyze the frequency-response characteristics of the suspension. The correctness and validity of the passive realization method of ideal skyhook damping were verified in theory. The results show that passive skyhook-damping suspension improves low-frequency response characteristics of vehicle. It inhibits the body's vertical and pitch vibration, as a result, improves ride comfort, and shows the main functions of the ideal skyhook-damping suspension. [ABSTRACT FROM AUTHOR]

Contrapose the problems of radomness of metal mesh selection and networking way which serious affecting the quality of support, the loading states, deformation and supporting effects of bolt metal weshes were studied by the method of laboratory tests. The special metal mesh deformation test bench and gauged metal meshes were designed and manufactured in the laboratory, the maximum surface protecting force and deflection of three kinds of metal meshes under different supporting states were measured, the influence of different networking modes on the metal meshes intensity utilization rate were analyzed, the ultimate bearing capacity and strength utilization ratio under different supporting states of 3 kinds of metal mesh were obtained. The metal mesh intensity utilization rate is low and the networking intensity is the weak links to restrict the surface protecting force of metal meshes was pointed out. The important method and way of improving the supporting effect of bolting is improving greatly the metal mesh pre-tension. [ABSTRACT FROM AUTHOR]

Minova is one of the world's leading suppliers of injection and bolting chemicals for use in underground mining, tunnelling and civil engineering. Developed from the range of silicate resins, Carbothix is a thixotropic resin system that can be used for the placement of rock bolts in underground mines. This paper describes the use of Carbothix in the underground environment and describes the cost benefits and advantages of using Carbothix for the anchoring of rock bolts. [ABSTRACT FROM AUTHOR]

Abstract: Methyl 3-iso-cucurbate was found to inhibit the stem elongation (bolting) of Qing geng cai (Brassica rapa var. chinensis) plants. Furthermore, its application did not induce leaf senescence and showed no acute toxicity against killifish. Therefore, it is a potential bolting inhibitor for winter annual crops, such as Qing geng cai. [Copyright &y& Elsevier]

Abstract: Problem: Operators of roof bolting machines in underground coal mines do so in confined spaces and in very close proximity to the moving equipment. Errors in the operation of these machines can have serious consequences, and the design of the equipment interface has a critical role in reducing the probability of such errors. Methods: An experiment was conducted to explore coding and directional compatibility on actual roof bolting equipment and to determine the feasibility of a visual feedback system to alert operators of critical movements and to also alert other workers in close proximity to the equipment to the pending movement of the machine. The quantitative results of the study confirmed the potential for both selection errors and direction errors to be made, particularly during training. Results: Subjective data confirmed a potential benefit of providing visual feedback of the intended operations and movements of the equipment. Impact: This research may influence the design of these and other similar control systems to provide evidence for the use of warning systems to improve operator situational awareness. [Copyright &y& Elsevier]

Purpose. To find the technological methods of increase the composite anchors production efficiency and to determine the research ways to solve important economic- engineering problems aimed at reducing of mine bolting prime cost. Methodology. Analysis and generalization of literary sources and tendencies of technological development of mine polymer anchoring, generalization of information about fastening tools and researches of authors dealing with polymer anchoring are the methodical basis of the complex research performed. Findings. We have substantiated the efficiency of polymer anchoring of mine workings which meets the world tendencies of composite anchor application. We have substantiated efficiency of the shape of anchor bar which has the tubular form with cell surface structure. We have analyzed the reinforcing materials for anchors taking into account their features, price and availability of domestic production. The list of additives required for binding agent improvement has been suggested and their influence on the material strength has been determined. The prototypes for industrial installations producing such anchors have been suggested. Originality. We have worked out the complex approach to define the shape, structure, reinforcing materials, additives to provide effective anchor bolting and proper strength of the structure. Practical value. The anchor structure, materials and technology of the polymer anchors pilot production have been determined. The research ways for development of effective mass production of polymer anchors corresponding to the specifications which allow reducing prime cost of mine polymer anchoring are defined. [ABSTRACT FROM AUTHOR]

Bolt pretension has an important part in roadway support, but the study on strengthening characteristics of anchorage body with pre-stressed bolts still has many problems. Mechanics characteristics of detached anchorage body was researched by using RMT-150C testing machine, which was fabricated by wax-sand, pretension bolts and plainstrain restrain device. The results indicate that strength enhancement factor of peak strength, residual strength are positive correlation with rock strength and pretension of bolts. Strength enhancement factor is gradually increasing with pretension when rock strength is constant, and the residual strength enhancement factor of pretention of is greater than that of peak. There are corresponding relationship with stress-strain curve and bolts loads. Congruent relationship exists between stress-strain curve and bolt load. Before surrender point, bolt load increases slowly; however which increases rapidly after surrender point. Bolt load increases gradually on post-peak points, and constantly descends on flow phase. The higher strength of rock is, the lower increase rate of bolts loads are with the same pretension. The increase rate smaller is, the higher pretension is with the same rock. The loss of pretension in failure stage is much more of soft rock than that of hard rock. The strengthening effect in soft rock is obvious than that of in hard rock. Site practice shows that surrounding rock deformation can be decreased effectively with high bolt pretension. [ABSTRACT FROM AUTHOR]

In order to get and predict initial support pressure, mechanical models of bolt's stress and bolt's installation were established, based on the hypothesis on surrounding rock of immediate bolt support in elastic-plastic status. The relationship between initial support pressure and tightening torque was analyzed, and theoretical solutions to initial support pressure were obtained for two contacts of pallet and nut. Meanwhile, verification research was carried out by "Bolt Force Transfer and Attenuating Test System". The results show that there is a linear relationship between initial support pressure and tightening torque under the same condition of bolt' s material quality, specification, row & line space; when the tightening torque is among 0 - 300 N * m, the equations of initial support pressure and tightening torque is right; initial support pressure can be quantized and predicted by tightening torque. [ABSTRACT FROM AUTHOR]

Abstract: Despite fully grouted bolts are nowadays widely used for tunnel support, bolting design is still based in many cases on empirical or semi-empirical considerations. This paper describes a three-dimensional theoretical and numerical model for the behavior of tunnels reinforced by bolts. From a theoretical viewpoint, the elastoplastic constitutive equations for the reinforced rock are derived in the framework of homogenization method. Emphasis is given to the formulation of the homogenized strength criterion with account for the bolt/rock interface properties. The anisotropic constitutive equations are then implemented in a 3D finite element computer code in which the processes of excavation, installation of bolts and lining placement are simulated by means of the “activation/deactivation” technique. Due to the multi-potential nature of the plastic flow, a specific iterative algorithm for plastic integration is proposed. The finite element model is applied to the analysis of the Kielder experimental tunnel for which in situ measured data are available. The accuracy of the numerical predictions based on homogenization method is also assessed by comparison with the results derived from implementation of the so-called embedded model. [Copyright &y& Elsevier]

A novel method was proposed to identify the modal parameters of roof bolter's drilling arm with high precision. In order to verify this method, we made an experiment, and the results showed that the method had a good validity and reliability. The proposed method is less affected by mode superposition and can overcome the disadvantages of traditional modal parameters identification method. Furthermore, the method can help to update the FEM model of roof bolter's drilling arm and the identified modal parameters also provide basic data to further dynamic analysis and optimum design. [ABSTRACT FROM AUTHOR]

According to the situation of gob-side entry retaining with the large and uneven deformation and poor support effects, took gob-side entry retaining in Qinxin colliery as engineering background, dealt with the numerical simulation analysis the relationship between support inside roadway, surrounding rock deformation and stress distribution, and the obtained support mechanism inside roadway of gob-side entry retaining are as follows: with the application of support with high resistance and yielding, increasing carrying capacity and deformation resistance of surrounding rock in roadway, adapting to large deformation and stress adjustment. The developed support technologies inside roadway of in gob-side entry retaining are:(1) basic support: using high-strength bolt and anchor support owning high pre-stress force, increasing carrying capacity of surrounding rock and adapting to large deformation; (2) reinforced support: within a certain range behind working face, in gob-side entry retaining, the hydraulic support with high resistance and yielding is used to strengthen roof and floor support, which means that in the intense stage of roof breakage and stress adjustment of surrounding rock of gob-side entry retaining, the hydraulic support can be used to support the roof and floor effectively and reduce the rotating, sinking of roof and floor heave, maintaining the stability of surrounding rock in gob-side entry retaining; (3) after the surrounding rock deformation stability in gob-side entry retaining, the hydraulic support used as reinforced support can be removed. [ABSTRACT FROM AUTHOR]

Inerters have become a hot topic in recent years especially in vehicle, train, building suspension systems, etc. Eight different layouts of suspensions were analyzed with a quarter-car model in this paper. Dimensionless root mean square (RMS) responses of the sprung mass vertical acceleration, the suspension travel, and the tire deflection are derived which were used to evaluate the performance of the quarter-car model. The behaviour of semi-active suspensions with inerters using Groundhook, Skyhook, and Hybrid control has been evaluated and compared to the performance of passive suspensions with inerters. Sensitivity analysis was applied to the development of a high performance semi-active suspension with an inerter. Numerical simulations indicate that a semi-active suspension with an inerter has much better performance than the passive suspension with an inerter, especially with the Hybrid control method, which has the best compromise between comfort and road holding quality. [ABSTRACT FROM AUTHOR]

Foreign and Ukrainian experience of application of modern roof bolting technology during mining shows that it provides stability and reliability of tunnels for continuous service in different use environment. One of the requirements of roof bolting installation is mounting it in loaded by rock pressure enclosing rock massif in immediate vicinity of coal face. It allows best preservation of natural monolithic state of marginal rock due to involvement of installed roof bolting into rock pressure resistance work. When the excavation is carried by means of mining combine, it is easy to install another row of anchors in time because destruction of the roof rocks is minimal and work gives the necessary effect. But in case of blast-hole drilling, excavation work breaks natural monolithic rock. Determination of the stress field around the coal face before, during and after explosion of blast-hole charges will allow estimation of the impact of the explosion on the stability of roof bolting and its ability to keep roof rocks in an undisturbed state. Thus the purpose of the research was the study of state the roof rocks fixed by the roof bolting in en excavation made by method of blast-hole drilling by means of mathematical modeling and mining experiments and observations data analysis. The article presents the results of numerical modeling of geomechanical and filtration processes around the mine working fixed by the roof bolting during explosion of blast-hole charges. The state of unfixed roof over the coal face with different delays of roof bolting installation from the coal face was done. It is shown, that roof bolting prevents rock foliation and destruction of the roof rocks even in en excavation made by method of blast-hole drilling. [ABSTRACT FROM AUTHOR]

In the paper, after short historical outline, a development of roof bolting use in Polish coal mines on the span of last twenty years was presented. Two characteristic examples of use were given. First of them is related to the solution, which found the widest use in mines. It consists in replacement of abutment at longwall and entry crossing with bolts. Second example concerns the use of independent roof bolting. For both examples, the geological conditions were described, as well as the applied patterns of bolting and the principles of support and mine working stability control. The realized review of development of roof bolting enables to present series of advantages resulting from the use of roof bolting. The use of independent roof bolting gives the largest efficiency effects. The calculations conducted for definite workings proved that the reduction of costs between 24 and 57% may be achieved in relation to arch support. Simultaneously, the fact attracts attention, that the total length of workings executed with independent roof bolting for last twenty years makes only 15% of stone coal workings total length realized in Polish coal mining on the span of one year only. [ABSTRACT FROM AUTHOR]

Abstract: The ground reinforcement by bolting is a technique in strong development. Bringing a perennial supplement of resistance to the ground, this technique permits to use poor grounds in a sensitive environment. It can be particularly, used for the reinforcement of tunnel faces. The full numerical simulation of such works remains a heavy and expensive process, notably in terms of geometrical complexity and various scale levels. During the preliminary project stage, it appears necessary to have simplified models, making possible to simply appreciate the effectiveness of the reinforcement. The existing simplified methods being not well adapted for the optimal conception of these reinforcement systems, a new method based on the convergence confinement approach is proposed and tested in this paper. [Copyright &y& Elsevier]

The paper presents an innovative dual purpose automotive suspension topology, combining for the first time the active damping qualities with mechanical vibrations power regeneration capabilities. The new configuration consists of a linear generator as an actuator, a power processing stage based on a gyrator operating under sliding mode control and dynamics controllers. The researched design is simple and energetically efficient, enables an accurate force-velocity suspension characteristic control as well as energy regeneration control, with no practical implementation constraints imposed over the theoretical design. Active damping is based on Skyhook suspension control scheme, which enables overcoming the passive damping tradeoff between high- and low-frequency performance, improving both body isolation and the tire's road grip. The system-level design includes configuration of three system operation modes: passive, semi-active or fully active damping, all using the same electro-mechanical infrastructure, and each focusing on different objective: dynamics improvement or power regeneration. Conclusively, the innovative hybrid suspension is theoretically researched, practically designed and analysed, and proven to be feasible as well as profitable in the aspects of power regeneration, vehicle dynamics improvement and human health risks reduction. [ABSTRACT FROM AUTHOR]

This article provides a non-dimensionalised closed-form analysis of semi-active vehicle suspensions, using a quarter-car model. The derivation of the closed-form solutions for three indices that can be used for ride comfort, vehicle handling, and stability are presented based on non-dimensionalised suspension parameters. The behaviour of semi-active vehicle suspensions is evaluated using skyhook, groundhook, and hybrid control policies, and compared with passive suspensions. The relationship between vibration isolation, suspension deflection, and road holding is studied, using three performance indices based on the mean square of the sprung mass acceleration, rattle space, and tyre deflection, respectively. The results of the study indicate that the hybrid control policy yields significantly better comfort than a passive suspension, without reducing the road-holding quality or increasing the suspension displacement for typical passenger cars. The results also indicate that for typical passenger cars, the hybrid control policy results in a better compromise between comfort, road holding and suspension travel requirements than both the skyhook and groundhook control methods. [ABSTRACT FROM AUTHOR]