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Rock bolts are commonly used to stabilise slopes and underground excavations but their installation can sometimes be difficult in challenging grounds due to excessive leakage or washout of the grout. To manage these problems, tubular geotextile socks have been adopted in the industry but there has been a lack of research on their properties. To advance the understanding of sock behaviour, the water permittivity and filtration properties of two types of grout sock have been investigated in their unstretched state. From the permittivity tests, it is shown that water flow through these socks will be laminar and that using more than one layer in a setup can effectively reduce the flow velocity. Moreover, it has been shown that the effect of the tester should be considered in the analysis or else the permittivity of the geotextile could be underestimated. From the filtration tests, it is shown that both types of grout sock tested are effective in minimising grout loss and that the permittivity of the filter cake will be many orders of magnitude lower than that of the socks. The results also show that the water–cement ratio of the grout will be reduced as a result of the dewatering process.

In order to study the mechanical mechanism of the new tension–compression composite anchor, the finite element software is used to establish the numerical calculation model of the new composite anchor, and the numerical drawing test is carried out. Through numerical experiments, the optimal position range of the bolt bearing plate is obtained, and the axial load and shear stress distribution of the bolt were analyzed. The results show that the ultimate pullout force of the new tension–compression composite bolt increases first and then decreases with the movement of the bearing plate position, and the optimal position is at the position where the length ratio of the tension–compression anchorage section is 3:4. At the same time, the study shows that the optimal position of the bearing plate has an optimal position interval. The ultimate uplift capacity of the new tension–compression composite anchor is 118.6% and 94% higher than that of the traditional tension anchor and pressure anchor, respectively. The shear stress distribution of the new tension–compression composite anchor is more uniform. The peak shear stress first appears at the bearing plate and begins to transfer to both sides of the bearing plate with the increase in the drawing force, which increases first and then decreases. Since the new tension–compression composite anchorage section is in an unbonded state, the axial load of the bolt is always equal to the drawing force. The axial force distribution of the tensile anchorage section is similar to that of the traditional tensile bolt and decreases exponentially along the axial direction of the bolt. Under the action of ultimate drawing force, the plastic zone distribution of the new tension–compression composite anchor is different from that of the traditional tension anchor and the traditional pressure anchor. The plastic zone first appears in the position of the bearing plate and begins to transfer to both sides of the bearing plate with the increase in the drawing force. When the plastic strain exceeds the allowable strain of the interface, the bolt pulls out from the anchor hole and the bolt support structure fails.

The problem of proper assessment of the technical functionality of rock bolt support systems is still valid. Many research centers have undertaken efforts to diagnose and monitor the technical state of such a support system used in mines and tunneling. With that aim the method of quality assessment of grouted rock bolts was invented and a relevant apparatus was constructed. The method concerns non-destructive identification of discontinuity of a resin layer (grout) surrounding rock bolts. The method is based on an impact excitation of a rock bolt and uses modal analysis procedures. Assuming that the installed rock bolt acts as an oscillator, different lengths and positions of grouting discontinuity alter its modal parameters. The extraction of these modal parameters, of which a resonant frequency is seen as the most valued, enable the relevant identification of grout discontinuity. After constructing a prototype version and validating the results for known cases of resin discontinuity in an experimental coal mine, the apparatus fulfilling ATEX requirements was developed. Subsequently that version was also verified both in laboratory conditions and in an experimental coal mine. As necessary for proper identification of discontinuity length, the reference data base was developed and elaborated consisting of a very large number of finite element models (FE models), namely discontinuity cases. The models encountered different rock bolt lengths and diameters, different rock strata parameters and different positions and lengths of resin layers. Then the method was used in a working coal mine to monitor a technical state of rock bolt support system mounted to reinforce long underground openings. The data base was utilized as reference for investigated rock bolts.

Roof falls are currently one of the most dangerous threats associated with underground mining at great depth. Every occurrence of such an event poses a significant risk to the mining crew and disturbs the continuity of the mining process, which clearly affects the economy of the exploitation process. The development of a reliable monitoring system may significantly reduce the impact of eventual roof failure and will have a positive effect on the sustainability of the extraction process. Within this research study, a prototype of an instrumented rock bolt developed for continuous stress measurement is presented. The procedure of a 4-groove multilevel instrumented rock bolt is described and the calibration process is shown. Then, preliminary results of long-term in situ monitoring are presented. Based on the continuous monitoring of stress distribution within immediate roof strata, it was concluded that the developed instrumented rock bolt provides reliable results and is a very useful device, ensuring the possibility of early warning for miners about increasing roof fall risk.

Optimizing or revising support systems are inevitable due to the existence of high probabilities and uncertainties in underground mines. For this aim, field data and measurements are the only scales available to truly measure the performance of these systems. This paper presents a site-dependent approach for optimizing/revising the applied rock bolt support systems and estimating the efficiency of installation operation based on the field data for underground coal mines. For this purpose, a comprehensive database containing field data from 128 different mining locations of an underground coal mine was taken into account. At first, the relationships between field data and measured displacement by installed tell-tale extensometers (TTD) in the roof to determine the effective parameters on the roof instability were analyzed. In the following, a method was introduced to calculate the weighting factor of the effective parameters in the system using coefficient of determination (R2) and sensitivity index (SI). The sensitivity index was developed for sensitivity analysis of all considered parameters on TTD under fair conditions. Then, a method entitled field data-based risk index (FDRI) model was presented to evaluate the risk of roof instability supported by rock bolt systems which was validated by the considered case study. Finally, a process was proposed to optimize/revise a rock bolt design using the results of FDRI model and introduced data-driven efficiency (DDE) theory. DDE theory was provided to relative estimation of the efficiency of the installation operation of rock bolts. This research presents a systematic method for selecting the effective parameters on an issue or hazard, determining their weight in the system and carrying out relevant ratings needed for risk assessment.

In this study, different plate fixing designs were tested in order to improve rock bolting performances. Instead of commonly used steel nuts, different plate fixing designs were investigated by both laboratory and site studies. In addition, the usability of nuts and energy absorbers made of the polyamide type engineering polymer was investigated to assess whether they are advantageous for the aim of supplying high-energy absorbing features. In this experimental study, deformation-controlled load tests were carried out to evaluate the bearing and energy absorption capacities of totally eight different groups of specimens. According to the findings from this study, use of the polyamide material with steel nuts as an energy absorber material, rather than using instead of steel nuts supplies good results. As another outcome, it has been determined that use of proper washers between steel nuts and polyamide absorbers can significantly improve the energy absorption performances. It has been evaluated that the energy absorption capacity of the bolt plates can be economically increased up to 10 times by using suitable polyamide energy absorbers placed between the plate and steel nut parts. It was concluded that the polyamides can be used to remarkably improve the rock bolting performances especially in the rock masses where the high energy absorption capacity property is needed, like those with rock bursting, squeezing and swelling problems.

This thesis was scanned from the print manuscript for digital preservation and is copyright the author. Researchers can access this thesis by asking their local university, institution or public library to make a request on their behalf. Monash staff and postgraduate students can use the link in the References field.

The blasting tunneling construction method is often used in the underground engineering projects such as tunnels, coal mines roadway, chambers and so on, rock bolt and shotcrete support is used. Although the blasting construction method has many advantages, but also will be accompanied by adverse effects. Blasting vibration of blasting construction not only to the surrounding environment, building (structure) and other adverse effects, but also on the support of the underground project itself has a negative impact. In order to discuss the impact of blasting vibration on shotcrete and rock bolt support in the process of blasting tunneling of roadway, a certain amount of explosives is detonated in the hole of the working face, the finite element software ANSYS/LS-DYNA was used to establish the numerical calculation model, through time history analysis calculation, the distribution law of the vibration velocity on the shotcrete surface along the section and the variation law of the longitudinal tension and compression stress of the rock bolt are obtained. The results show that the blasting vibration produced by blasting tunneling has a great influence on the shotcrete at the shoulder, but little influence on the axial force of the rock bolt.

Rock bolting technique is an important reinforcement measure in the geotechnical engineering practice. New rock bolts have been continuously emerging through the development of rock supporting technology. Complex conditions, such as high crustal stress, extremely soft rock, and strong mining disturbance often occur in the deep mining, resulting in large deformation of the surrounding rock masses. Since the deformation of traditional rock bolts is generally below 200 mm, failure often occurs to the rock bolts because of insufficient deformability. To effectively control the large deformation of surrounding rock masses caused by complex conditions, it is necessary to develop large deformation rock bolts with high constant resistance, also called energy-absorbing bolts. This paper systematically reviews the development of large deformation rock bolts and the structure, energy absorption mechanism, anchorage performance, and mechanical properties of several typical large deformation rock bolts. The advantages and disadvantages of existing large deformation rock bolts are compared and the concept of constant resistance large deformation support is introduced.

Coal auger mining is a promising technology used for excavating thin coal seams. The efficiency of auger mining is largely related to the stability of mine roadways in the influence zone of the coal-face. Roof bolting systems are promising in such conditions. An adequate choice of roof bolting parameters is only possible if one understands the features of the stratification of the rocks and stages of deformation of the array in auger mining. Modern monitoring methods of the condition of rocks are based on the use of mechanical benchmarks, sounding of the mine array and the use of optical devices. There are few studies concerning roadways with auger mining. The innovations presented in this manuscript are a determination of the research results of the in-situ processes of rock deformation around a roadway in auger mining which will help to better understand the features of deformation processes in the technological method and design an adequate support system. Some field studies were undertaken in order to investigate the geo-mechanical processes that can be observed while auger mining a roadway with fully grouted bolts of 2.4 m in length. The research included monitoring rock stratification with the help of mechanical telltales, the convergence in the roadway using contour benchmarks, measurements of altitude and rock falls, and visual observations. The presented results show that roof-bolting can be used to support the roadways for auger mining., Rudarenje ugljena svrdlima (augerima), tj. strojevima za iskopavanje ugljena bušenjem, tehnologija je primjerena za vađenje tankih ugljenih slojeva, a učinkovitost uvelike ovisi o stabilnosti rudničkih okana na ugljenome čelu, što se rješava podgradama. Prikladan odabir varijabli podgrade moguć je samo kada se razumiju svojstva slojeva u toj krovini te njihova podložnost deformacijama kod bušenja svrdlima. Suvremene metode praćenja svojstava stijena temelje se na mehaničkim provjerama, sondiranju i optičkome ispitivanju. Postoji nekoliko studija takvih uvjeta, a ovdje su dane inovacije kod opažanja deformacija in situ, tj. u oknima u kojima se buši. Tako se bolje opisao proces deformiranja te tehnologija izgradnje adekvatnih podgrada. Odabrano je nekoliko terenskih studija kojima su izučena geomehanička svojstva stijena tijekom bušenja uz uporabu injektiranja u dužini od 2,4 m. Praćenjem uslojenosti i pojava mehaničkih nedostataka u oknima kartiranjem, mjerenjem visine i vizualnim opažanjem uočavani su nedostatci. Rezultati su pokazali kako je podgrađivanje sidrenjem poželjno.

Some mountain tunnels suffer from perennial deformation induced by overburden and confining stresses. Conventionally rock bolts are being used as a countermeasure . Oftentimes the conventional rock bolts fail to deliver their optimum performance, owing to several potential causes. Such as: the ground around the tunnel is too plasticized while transmitting shear forces along with the solidified mortar; and the rock bolts are poorly anchored with grout at the rear end. Considering these facts, we develop a bonding of rock bolt, named CIB-bolt, a combined mechanism deals with ground Improvement, to improve the plasticized ground while preventing further deformation of tunnel and to achieve positive bonding of rock bolts. To confirm the effectiveness of the developed rock bolt which was utilized in the experiment model, a real field application and numerical analysis also were conducted. Observed results indicate that, the developed rock bolt exhibits excellent performance in transmitting axial stresses towards the hard layers of rock. This mechanism can prevent the yielding or plasticization of adjacent ground and control the deformations of tunnel lining .

The proposal of the NATM has changed people’s understanding of the support principle. Therefore, how to improve the self-supporting capacity of surrounding rock has become an important issue in support research. Bolts and lining are widely used together in various support projects because their bearing and reinforcement effects are in line with the concept of the NATM. This paper puts forward a model to analyze the mechanical behavior of a deeply buried circular tunnel jointly supported by lining and point-anchored rock bolts. Rock mass, lining, and bolts maintain an elastic state and are in full contact with each other. In addition, point-anchored rock bolts are replaced by pairs of concentrated forces of equal magnitude that act in opposite directions. By using the complex function method, the linear equations for calculating the axial force of the bolts and the relevant analytical function coefficients can be established, based on the stress condition of the inner boundary of the lining, the continuity conditions at the interface between the lining and the surrounding rock, and the compatibility condition of the displacement between the bolts and the surrounding rock. Then, using the analytical functions, the stress and displacement of any point in the lining and surrounding rock can be calculated. The results were compared with the numerical solutions. Moreover, the effects of the bolts and the Young’s modulus of the lining on the whole support system are discussed.

An accurate model for the prediction of the rheological behavior of surrounding rocks is essential to the designing of rock bolts for tunnels under squeezing conditions. Our understanding of the state of the art suggests that the rheology of rock consists of the transient, the steady-state, and the accelerated regimes. Thus, a visco-elastic-plastic rheological model, namely the Komamura-Huang-Bingham model, was developed. The model used the Drucker-Prager yield criterion in order to consider the effects of the intermediate principal stress on the strength of the rock mass. The developed model was implemented in the framework of finite element simulations. It was validated by comparing the simulation results with the on-site monitoring data. The focus of the simulations was on the mechanical behavior of the rock bolts and the surrounding rock mechanics during the construction of the tunnel. A sensitivity analysis was performed with respect to the length of the bolts and the stress-to-strength ratio of the rock was performed. It was shown that increasing the length of the bolts up to 9 m results in a reduction in rock deformation. This critical value of the bolts’ length is approximately equal to the diameter of the investigated tunnel. A further increase in the length results in an insignificant reduction in the deformation of the surrounding rock. In the case of the Class A and B squeezing conditions suggested by Hoek, the deformation of the surrounding rock is insensitive to the length of the bolts. The elongation of the bolts does not change considerably with time, which is in contrast to the Class C and D squeezing conditions. The extent of the plastic zone is related to time and in situ stress but is independent of the length of the bolts. This is consistent with the characteristics of the nonlinear rheology of rock mass.

The complex geological structure of Taiwan often makes it difficult to control the deformation behavior of tunnel excavations. To simplify analyses, most traditional empirical formulations and modern numerical analyses do not consider the existence of rock bolts. For this reason, this study aimed to investigate the vertical displacements caused in tunnel crowns under various geological conditions using a three-dimensional finite element analysis with tunnels of different cross sections as an example. The analysis was performed using two rock material models: the Mohr–Coulomb and Hoek–Brown models. The results indicated that there was an insignificant difference between the two models in terms of the magnitudes of displacement and the distribution profiles obtained. When a tunnel was being excavated, the weaker the site was geologically and the larger the cross section, the larger the vertical crown displacement. In addition, the presence of rock bolts had a significant influence on the displacement in areas where the geology was weak and the cross section was large. The numerical analysis results of the Mohr–Coulomb and Hoek–Brown models were compared with the values calculated using the formulas suggested by Unlu and Gercek. At the excavation face, the displacement ratio derived from the prediction formula of Unlu and Gercek was smaller than the numerical analysis result, and the difference between the two became larger when the rock mass quality was worse.

A rock and/or coal burst is an uncontrolled failure that releases a massive amount of kinetic energy, inducing excessive displacement of coal/rock mass. Combined support to controlling rock and/or coal dynamic failures is an essential part of the rock burst management. In the design of rock support, it is essential to consider not only the capacity of the individual elements but also their compatibility with each other and their interactions. This paper aimed to develop a novel full-scale numerical procedure to evaluate the behaviour of individual support elements and their interactions under dynamic loads using Finite Element Commercial Package ABAQUS/Explicit. A mutual interaction relationship between two indicators, namely Cable/Rock Bolt Dissipated Energy and the Steel Mesh Dissipated Energy is also developed, and an interaction diagram is provided. The proposed design concept can be used for the selection of an appropriate support system for coal burst management.

This paper modified the original structural elements of pile in FLAC3D to analyse the performance of rock bolts. For the contact surface between the bar and the binding grout, bonding behaviour was modelled using the tri-linear constitutive relation. Pull tests were used to testify the effectiveness of the modified pile elements. A satisfactory correlation was acquired between the modelling and physical results. This testified that the improved pile elements can successfully analyse the performance of bolts. Then, a numerical coal roadway was established and reinforced with the modified pile elements. After equilibrium, a non-uniform force distribution occurred along bolts. The axial force around the middle was maximal and the tensioning force at two ends of the bolt was minimal. A parametric analysis was performed to analyse the effect of relevant factors on performance of bolts. The results showed that with the bonding strength of the bolt surface raising, the neutral point shifted towards the excavation direction. Moreover, when the applied vertical stress was beyond a limit, the axial force in the bolts installed in the roadway side reduced dramatically. However, for the bolts installed in the roof, the axial force in the bolts was still raising.

Rock bolts have been widely employed on slopes as a reinforcement measure. Modeling the shear mechanical behaviors of bolted rock joints is very complicated due to the complex factors that affect the axial and shear forces on the bolts. The rough surface of the joint surface undergoes a dilation effect and morphological abrasion under shearing. However, existing analysis models do not fully consider these effects. This study proposes an analytical model for predicting the shear behaviors of bolted rough joints. The model considers the relationship between the dilation effect and the bolt deformation and the influence of joint surface abrasion on the attenuation of the internal friction angle. Moreover, the axial force development is corrected at a bolt installation angle of 90 degrees, and the effect of the initial normal stress of the joint surface on the deformation and fracture of the bolt is also considered. The analysis model successfully predicts the shear load-shear displacement curve of the anchoring joint and the change curve of the anchor shaft force. The analysis model is verified by an indoor direct shear test. The validation shows that the proposed model can effectively describe the deformation characteristics of the bolts in shear tests.

Failures of rock bolts installed in jointed rock masses due to shear movement along weak joints in bedding rock slopes or underground caverns are common. Existing models to design rock bolts often only consider a rock bolt’s shear behavior in the elastic stage and ignore their larger non-elastic deformations, which significantly underestimates the bolt’s contribution to the joint shear resistance. Therefore, developing an analytical model capable of reflecting the plastic strain‑hardening of rockbolts subjected to large deformation is very necessary for more effective numerical simulation models as well as rock support design. An experimental investigation was conducted on grouted bolts subjected to joint shear movement. The bolt installation angle with respect to the joint was varied in the tests. Pairs of strain gauges attached to the surface of the bolt shank near the joint measured the bolt deformation during the shear testing. The deformation characteristics of the bolt and grout in the elastic and the plastic stages were evaluated. Based on the experimental measurements, a new analytical model to predict the bolt’s ultimate contribution to the shear resistance of a joint was developed. This model considers large deformations. The analytical model includes the influences of the bolt angle, rock mass strength, joint dilation angle, and bolt tensile strain. A comparison of the model predictions with results from large-scale tests and other existing methods shows good agreement with the tests and an improvement over existing methods.

Rock bolts are one of the most effective and conventional support techniques widely used in underground mining and tunneling operations to stabilize excavations and jointed rock masses. External factors such as corrosion, overloading, and improper installation can weaken rock bolts, which could result in ground failure causing injury or loss of life and production. Monitoring the health condition of rock bolts will reduce the risk of accidents providing a safer environment for workers and equipment. This paper reviews monitoring methods currently used to assess the condition of installed rock bolts. Furthermore, we classify the surveyed techniques depending on the type of problems they attempt to solve. Presented are methods such as ultrasonics, fiber optics, piezoelectric, electromagnetics, impact echo, acoustic emission, and numerical algorithms. Each method is based on a unique physical principle that aids in evaluating corrosion and strain levels in the rock bolt. However, recent research to detect corrosion has primarily focused on rebar type of rock bolts used in concrete structures. Consequently, more research is needed to monitor the condition of the other types of rock bolts used in the industry such as cable bolts and split set bolts. In conclusion, the paper highlights various methods of studying rock bolt failure initiated by strain, corrosion, and improper installation of the grouts. It also explores the research advancement made for the study of rock bolt failure. This investigation is specifically beneficial to the mining and tunneling industry for better understanding and prediction of rock bolt failure.

Numerical modelling has become an important tool in the underground rock bolt reinforcement designing process. Numerical modelling provides the advantage of easily and quickly simulating complex underground geometries and mechanisms with sensitivity analyses. However, a numerical model needs to be calibrated using mathematical solutions, lab testing or with actual in-situ observations and measurements (which is the preferred method) before its results can be quantitatively applied to reinforcement design. Instrumented rock bolts provide a useful data source for calibrating in-situ rock bolt models. In this work, procedures have been presented to identify and determine the orientation of structures in the rock mass based on the strains on the instrumented rock bolts. A method to calibrate the rock bolt model with in-situ data is also presented. The results of the presented procedures have been validated with laboratory tests and numerical modelling. The procedures have been applied to create and calibrate an in-situ rock bolt model in FLAC3D and the results are validated using in-situ data.

In this study, a deeply buried circular tunnel supported with point-anchored rock bolts was investigated. Assuming that the effects of each rock bolt on the surrounding rock are simplified to two identical concentrated forces acting in opposite directions, a viscoelastic analytical solution for the axial forces of the rock bolts is presented herein based on the complex variable method and correspondence principle. First, in the solution process, the surrounding rock is considered as an elastic material. A linear equation system for the axial forces was established according to the deformation coordination condition between the surrounding rock and the rock bolts. Second, the surrounding rock was considered as a viscoelastic material. Based on the correspondence principle, Laplace transformation was performed for the equation system of the axial forces to obtain its expression in the Laplace domain, and the values of the axial forces in the Laplace domain could be determined by solving the obtained expression. Finally, the viscoelastic semi-analytical solution for the axial forces was established using the numerical method of the Laplace inverse transformation. The results obtained were also compared with the numerical methods of ANSYS. Accordingly, the effects of the lateral stress coefficient, rock mass Young’s modulus, rock bolt length, viscosity coefficient, and preload on the axial forces of the rock bolts were discussed.

The purpose of a rock bolt is to improve the strength capacity of a jointed rock mass. The strengthened arch controlling area can be formed based on the superposition of the controlling influence range of the bolt with the controlling influence angle of rock bolt playing an important role. However, quantitative research on the influence angle is still rare. In this study, numerical simulations and mathematical analysis are used to study the law of stress field distribution and the controlling influence angle through a single bolt, and the following conclusions can be obtained. (1) The compressive stress field is roughly distributed in an "Apple shape" and in a "conical" spatial distribution. (2) The bolt controlling angle is not a constant 45°, and it is influenced by the rock mass strength and bolt parameters. It decreases with the increasing elastic modulus of the bolt, bolt diameter and bolt length. It also increases with the increasing pretension and rock mass strength. The length has less influence on the supporting range. (3) Based on the experimental results, an optimal analytical model to predict the bolt’s controlling influence angle was developed. The analytical model includes the influences of the rock mass strength and bolt parameters. (4) A comparison between the model predictions with the results from the Dabei Mining 103 face transportation tunnel and the existing results shows the rationale behind the original support design scheme and an improvement over the existing results.

In this paper, eight shear tests were carried out utilising a double shear with infilled shear interfaces after determining an appropriate experimental design and modified testing scheme. For this, two rock bolts, 20-tonne and 30-tonne, were tested with modified double shear testing apparatus at different pretension loads. The infilled test scheme was conducted with 5mm thick sandy clay infilled shear interfaces. A 40MPa small aggregate concrete was used for all samples to simulate the host rock. Based on the shear profiles, it was found that all samples followed a three-part failure profile consisting of elastic, strain softening and failure regions. The results of double shear tests revealed that the 20-tonne rock bolt saw a significant overall decrease of approximately 30% in its failure displacement response as opposed to the 30-tonne samples’ which saw a 6% increase. Also, it was concluded that the 30-tonne samples outperformed the 20-tonne rock bolts by up to 30%, irrespective of initial pretension settings. Comparing the physical failure characteristics of the samples found that both the 20-tonne and 30-tonne samples exhibited the same response to increased pretension. As the pretension increased, the angle experienced at the hinge point also increased incrementally.

The widespread existence of weak interlayer poses a serious threat to the stability of roadway surrounding rock under constant stiffness restraint boundary condition in lateral direction (axial direction of roadway) and the rock bolt is widely used to reinforce the surrounding rock of roadway. So, in this paper, the reinforcement performance of the bolted rock mass with a weak interlayer was investigated under constant lateral stiffness (CLS) boundary condition. The research results indicated that the peak strength and elasticity modulus of the samples exponentially increase with the increasing of bolt pretension force and density. Two parameters Rp and RE were put forward to quantitatively describe the reinforcement effect of bolt pretension force and density on the peak strength and elasticity modulus of the samples. Under CLS boundary condition, the lateral direction of the samples experienced loading-unloading and expansion - compaction deformation periods during the whole triaxial compression process. The mechanism for the transformation of expansion - to - compaction was explained. Two new failure modes of the samples were observed and analyzed in detail, and were found them different from those of the bolted jointed rock mass and bedded rock mass.

Glass-Reinforced Polymer (GRP) bolts are increasingly used in Australian coal mines as a means of rib support in heading development and for coal-face equipment recovery. Unlike metallic rock bolts, GRP bolts are made through pultrusion resulting in anchor bolts with differing performance characteristics to that of steel. Therefore, previous studies of steel rock bolts could not be utilised to describe the load transfer characteristics of their fibreglass counterparts. This thesis expanded on the shear load transfer mechanisms of fully grouted fibreglass rock bolts utilising a double shear system. Analytical and numerical models were also developed to simulate the shear performance of the fibreglass rock bolts. Two experimental test schemes were carried out. The first with clean shear interfaces and the second with infilled shear interfaces comprised of sandy clay, applied to a thickness of 5mm. Two types of fully grouted rock bolts; 20-tonne and 30-tonne were tested with pretension loads of 0kN, 10kN, 15kN and 20kN. It was found that increasing the pretension also increased the confining pressures at the shear interfaces for both clean and infilled joints. This in turn reduced the damage propagating from the bolt at the shear interface as well as reducing the hinge point bending. Infilled shear interface samples experienced a decrease in the failure displacement while also resulting in an increase to the peak shear force. The analytical model was developed utilising the Fourier transform, energy balance theory and linear elastic theory. The result was an empirical relationship that could determine the double shear performance of fibreglass rock bolts with close agreement to the experimental data. Coefficients were incorporated to facilitate model calibration and tuning. Finally, three-dimensional (3D) modelling was utilised to conduct numerical simulations of fibreglass rock bolts subjected to single shear and double shear scenarios. The numerical model was calibrated against experimental data and then extended to conduct a sensitivity analysis on fibreglass rock bolts subjected to variations of the double shear test parameters. Scenarios included rock bolt installation angles, shearing rates and various host rock strengths. The combined experimental, analytical and numerical studies provide a comprehensive understanding of the shear behaviour of fibreglass rock bolts. By studying the impact of pretension and shear interfaces, this research has successfully modelled the shear failure mechanisms of 20-tonne and 30-tonne fibreglass rock bolts.

In the past two decades, the corrosion failures of rock reinforcement bolts in underground coal mines have been increasingly reported. Preliminary studies have shown that these failures were predominantly related to pitting and stress corrosion cracking. The analyses in affected mines indicated microbially induced corrosion (MIC) as one of the primary corrosion causes. As such, there is an urgent demand from industries to develop methods to mitigate MIC-associated failures of rock bolts in underground coal mines. This study examined epoxy coating to determine its effectiveness in preventing biofilm formation on steel surfaces and, in turn, averting MIC. The corrosion-causing bacteria were isolated and enriched from groundwater samples collected from the affected mine sites. Coated and uncoated rock bolt samples were prepared from the bolts and incubated in media in the absence and presence of the corrosion-causing bacteria. Fluorescence microscopy imaging found no evidence of bacterial biomass growth on the surface of the epoxy-coated steel surfaces after 30 days, while the non-coated surfaces were colonised by biomass. The observations suggest the potential of epoxy coating for bolt MIC prevention. Future studies to assess the applicability of epoxy coating in the underground mine environment are recommended.

Considering the large-span underground excavation subway station of Qingdao Metro Line 6 of China for analysis, it is necessary to optimize the traditional support system by investigating relevant codes and other tunnel projects. Based on the active support concept, a high prestressed rock bolt support system is proposed, and the optimization direction is defined to apply a high prestress force to rock bolts, increasing the appropriate spacing between supporting arches and strengthening support at key parts such as the large arch foot area, sidewalls and junctions. Numerical calculations and field monitoring are performed to analyze and evaluate the new support system. Numerical simulation results show that the new support system can effectively improve the stress state of the surrounding rock; the tensile stress area markedly decreases in size or disappears; and the plastic area also decreases in size. Field monitoring results show that the settlement of the arch crown is concentrated at 2–5 mm and the deformation rates are less than 0.5 mm/day. The supporting arches, shotcrete and rock bolts are all less than the yield strength and a high safety reserve. These results verify the safety and rationality of the proposed support system, which can be used as a reference for similar projects.

The deformation and support method of roadways have always been important issues in safemining and production. Vinacomin's statistics show that, by 2021, there will be 64.19 km of roadwaysthat need to be repaired (accounting for 25% of the total new roadways). Thus, the problem of maintainingroadway stability is facing difficulties in underground coal mines in Vietnam. To find out the causes ofroadway failures, a case study at roadways of the Khe Cham I and Khe Cham III coal mines, Vietnam, ispresented in this paper. Based on the results of a detailed field survey, the deformation characteristics ofroadways and the failure mode of support structures were investigated. The results show that the roadwaydeformation is severe and the main support cannot control surrounding rock mass. Also, the destructionof support structure is frequent on reused roadways, affecting production efficiency and work safety.Therefore, to reduce deformation and increase roadway stability, a new support method called “multistageanchor of rock bolt + cable bolt” has been developed and a new longwall mining system with criticalcoal pillar width has been proposed. The new findings of the research can provide references for scientificstudies, and apply them in Vietnam's underground coal mine practices.

In the present paper, a new type of surface-bonded fiber Bragg grating (FBG) dynamometry bolt is designed. It is assumed that the adhesive layer is a linear viscoelastic material and its creep mechanical behavior is expressed by the standard linear solid model. The shear strain transfer model of the surface-bonded FBG sensor is established. Additionally, the instantaneous and quasistatic strain transfer functions of the surface-bonded FBG sensor are obtained. The functions are validated by a uniaxial tensile test and a long-term constant-load tensile test. The test results show that the strain measured by the FBG sensor has a proportional relationship with the strain measured by the resistance strain gauge. Furthermore, under the fixed load for a long period of time, the strain of the FBG sensor has a tendency to drift and the strain reduction rate is about 40.5%. Finally, the field application is carried out in a mining area. It has been proved that the ground pressure online monitoring system based on the FBG sensing technology can successfully monitor the stress of the rock bolt.

One of the important factors affecting the anchoring force of the end encapsulated bolt is the mechanical properties of the rock formation at the anchoring end. For the fully encapsulated bolt, its bearing performance is closely related to the mechanical properties of the bolt passing through the rock stratum and its permutation mode. In this study, a series of laboratory pull-out tests of multi-strata anchorage systems was carried out based on an actual engineering background. The bearing performances and failure mechanisms of the multi-strata anchorage system under different anchoring methods and combinations of rock stratum were studied. The evolution law of the axial force and shear stress of the Agent-Rock interface was also analyzed. The test results showed that, for end encapsulation, changes in the mechanical properties of the rock strata at the anchoring end caused differences in bearing capacity, while full-length encapsulation markedly reduced the disparities. The position of the stratum with the highest general interface shear strength affected the mechanical response of the anchoring interface. The progressive failure process of multi-strata anchorage systems was discussed, and suggestions for rock bolt support in coal mine roadways were also proposed.