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—Abstract: The use of high-strength rock bolt in the underground often occured brittle fracture in the threaded section, this is closely related to bolt material impact toughness. Tested the impact absorbed energy of four manufacturers of the yield strength of 500MPa rock bolt and the impact absorbed energy value ranging from 19J to 165J. Tested bending test of the bolt rod and threaded section that has a different impact absorbed energy, the results showed that: the impact toughness affects the cold bending of the rock bolt thread segment, when the impact absorbed energy value is less than 30J rock bolt thread segment cold bending poor; impact toughness has no obvious affect on the cold bending of rod.

Pretension is a key factor affecting the performance of rock bolt. It is usually applied on the bolt by tightening the nut. The efficiency of the torque-to-pretension conversion is significantly influenced by the thread rolling accuracy. In this study, the influence of the thread rolling accuracy upon the pretension is investigated. Factors influencing the thread rolling efficiency, i.e., rock bolt material quality, rolling technic and equipments, are examined. To study the relationship between torque and pretension, a laboratory table was specially designed and a series of tests were carried out on the rock bolts with different thread accuracy. The result indicates that the higher the thread rolling accuracy, the higher the coefficient of torque-to-pretension conversion. And the coefficient can be improved by daubing lubrication oil on the thread. In China, the rock bolt thread encounters the issue of low rolling accuracy which results in coarse thread surface. As a result, the efficiency of the torque-to-pretension conversion is greatly reduced. In addition, the rock bolt is susceptible to break at the thread end. Essential approach to resolve these issues is to significantly improve the thread rolling accuracy by adopting advanced equipment.

Based on the application of Rock Bolt Foundation in metallurgical industrial plant foundation design, this paper utilized bolt deformation formulas that derived by Gu Shuancheng and others to calculate deformation of rock blot. The result is consistent with the experimental value, the authors can further verify the experimental and theoretical calculation value eventually by finite element analysis software ANSYS, which provides a reference for practical application of rock bolt foundation in metallurgical industrial plant.

Restricted by the construction environment, the cable crane is an effective means to resolve the transportation of materials and component in the mountainous area. Compared with traditional gravity anchor base, cable crane fixed on the rock bolt foundation can take advantage of the bearing capacity of bedrock, and the construction method is simple and of good economic benefit. With the effect of the construction methods, design theory of geological conditions, and other factors, however, force calculation is much complicated. By analyzing the failure modes of rock bolt foundation, anchor foundation bearing capacity factors and multi anchorage effect on anchoring force, we studied the design process of rock bolt foundation, geotechnical strength parameters and the safety coefficient of reference value. Further, a construction way is proposed to improve the basic bearing capacity of rock bolt. Combing with engineering examples, we also demonstrated the security and reliability of the design method .

This paper used LS-DYNA simulation software to simulate rock bolt breaking position, displacements at different locations and the plastic deformation under dynamic load. Major drew the following conclusions: plastic deformation of the bolt away from breaks 600mm is only 1/20 compared with breaks; deformation of the rock bolt increased as the distance away from dynamic load applied position reduced, rock bolt deformation under dynamic load has a local effect; rock bolt deformation under dynamic load and rock bolt deformation under static load had essentially different.

The artificial neural network has been widely used in various field of science and engineering. The artificial neural network has marvelous ability to gain knowledge. In this paper, according to principle of artificial neural network , Model of artificial neural network of rock bolt support of roadway of coal mine has been constructed,Learning system of BP artificial neural network has been trained,it is shown by engineering application that artificial neural network can handle imperfect or incomplete data and it can capture nonlinear and complex relationships among variables of a system. the artificial neural network is emerging as a powerful tool for modeling with the complex system. Method and parameters of rock bolt support of roadway of coal mine can be predicated accurately using artificial neural network, that is of significance and valuable to those subjects of investigation and design of mining engineering

The bolt’s load transfer differential equation has established according the stress equilibrium in a small section of a bolt and load transfer mechanics. And according the rock mass deformation before and after bolt assembling, the rock bolt’s load transfer equation has gained. In this paper, from later researching achievement, the radial displacement function of brittle wall rock for tunnel is gotten. And combining the radial deformation of tunnel wall rock mass, the axial force and friction resistance of rock bolt have gotten in brittle wall rock mass. Through analyzing the stress distribution feature and stress distribution tendency and affection factors, the affection factors to anchoring results is the dilatancy angle. And through the studying, it is show that the axial force and shear stress of rock bolt are bigger with the dilatancy angle increase

The rock bolt has been widely used as an effective reinforcement in civil and mining engineering for a long time. However, the anchored mechanism of it is not well understood. This paper obtained the expression of the shear stress and axial force of stretched fully grouted rock bolt base on previous working, and detailed analysis the influence parameters of stress distribution. It is considered the anchored effect is influenced by some factors. Augmenting diameter of rock bolt, increasing the pre-stress magnitude and improving the strength of grout may all improve the anchored effect of rock bolt. As the rock character and the grout property are similar, the rock bolt anchored effect is optimal. There is a stress concentrated phenomena at the front of rock bolt. It is shown that the distribution of shear stress and axial force are not even distribution and exponentially attenuated along a fully grouted bolt.

It is important for evaluating the condition of rock bolts to theoretically investigate the propagation of elastic waves in Rock bolt .In this paper, ultrasonic guided wave propagation and the interaction law with the artificial corrosion ring defect in the solid cylinder were studied through the rock bolt was modeled as a cylindrical. A large number of numerical simulation experiments were carried out using finite element method based on ABAQUS, The longitudinal mode of the propagation characteristics and law were analyzed in the solid cylinder, and the best excitation model and frequency were selected for the signal dispersion by combining curve with wave structures knowledge. The outcome of this research indicated that L(0,1) reflection coefficient is increased as well as during the depth incremental change when given a particular axial length; With the increment of the axial, L(0,1) and F(1,1) of the reflection coefficient maintain the similar trend when the ring defect depth coefficient 10%.

Experiments were conducted to study the attenuation properties of ultrasonic guided wave propagating in anchored rock bolts. Results show that concrete as anchored material at different curing time can represent different bonding quality, and attenuation coefficient value of ultrasonic guided wave in anchored bolt increases as the increasing of curing time. At the mean time, the attenuation coefficient value becomes larger when the anchored length of rock bolt increases. So attenuation coefficient value is an efficient tool to evaluate the bonding quality of anchored rock bolt.

The anchorage length of the bolt in rock bolt crane girder is obtained by means of rigid limit equilibrium method and the critical the anchorage length of bolt is calculated by analytical solution. Combined with the calculation results, the analysis on the mechanical characteristics is carried on by building the finite element model of rock bolt crane girder with different anchorage length of bolt. The analysis results indicate that the bearing characteristics of rock bolt crane girder are not improved significantly with the increase of anchorage length when the anchorage length of bolt exceeds the engineering critical anchorage length. The existence of critical anchorage length of blot is proved further, and the rationality of analytical solution for critical anchorage length is validated.

Rock bolt crane girder is a structure form which is widely used in the underground powerhouse of hydropower station. It makes reinforced concrete anchored in the underground powerhouse rock using anchor rod, and makes the reinforced concrete, anchor rod and surrounding rock work together to resist the load. Stability has been a common problem in the realm of engineered construction. This article will analysis the stability of the rock bolt crane girder in a underground powerhouse of hydropower station by using the traditional rigid body limit equilibrium method and the finite element method, and give several destroying forms. The results show that the rigid body limit equilibrium method is flawed, need to be corrected; In overload cases, the contact surface of girder and rock crack, it turns the damage to the bottom O point at the end; When it is simulated by the strength storage method, the crane girder's shear yield slips the damage along the base.

Bolts are widely used in slope engineering, tunnel and large cave supporting structures, as well as restoration of engineering structures. They can improve the strength and stability of ground, rock mass, and other structures. The traditional steel bolt has some disadvantages, such as easy corrosion, heavy weight, and difficult operation. Glass Fiber Reinforced Polymer (GFRP) is more resistant to chloride, stronger and lighter than steel. Those advantages make it a better alternative in some fields of engineering. To utilize GFRP bars as rock bolt, some aspects of its behavior, such as bond strength in mortar, bearing capacity, and bond stress distributing along its interface, have to be examined. This paper presents a research on bond behavior of GFRP rock bolts. A concrete block is used to represent rock mass in laboratory. Modified pull out tests were conducted on selected GFRP bars and compared with steel ones that were grouted with mortar in concrete blocks. Bond characteristics of mortar grouted GFRP rock bolts with diameter 16mm were mainly evaluated and other specs of bolts were also discussed.

With development of coal mining technology and equipment, the coal roadway section size increases gradually, making roadway more difficult to support. In the paper, the supporting of large cross-section roadway in Hedong mine is studied and roadway excavation supporting process is simulated by FLAC3D. Coal roadway deformation and the problem of original supporting scheme are analyzed including displacement field, stress filed and plastic zone. Several supporting optimizations are proposed combined with site investigation and simulation analysis. And the optimizations are simulated and calculated. By comprehensive comparison, the optimal supporting scheme is obtained and some supporting law in large cross-section roadway is concluded. These are helpful for supporting design in future.

In this paper, the mechanical behaviors of pipe roof and bolt of shallow and unsymmetrical tunnel in soft rock are analyzed. Through the finite element software Phase2.0, combined with the geological conditions that construction site often appear, the mechanical behaviors of pipe roof and bolt and surrounding rock in the process of horseshoe highway tunnel construction in the condition that surface is soft rock and underground for the bedrock are analyzed. Research results show that: after tunnel excavation in soft rock, surrounding rock near the tunnel is easy to suffer soft-rock large deformation even failure, which needs to timely support；Due to the impact of the unsymmetrical tunnel, the mechanical behaviors of surrounding rock are unsymmetrical, such as the maximum displacement of tunnel around 0.4 m distant from apex of arch ring, the stress is asymmetrical on both sides of the tunnel arch ring etc; In addition, pipe roof can effectively prevent from the displacement of soft rock strata, improve tunnel strength factor, reduce the plastic zone of surrounding rock. This paper provides theoretical basis for the design of pipe roof and bolt.

Metallurgical industry factory building is usually high. Under the action of wind load and horizontal crane force, large moment will be induced at the column base. That is to say, the moment acting on the foundation is large. The embedded depth is relatively deep and the size of factory building foundation is relatively big. In the case of foundations based on the natural rock, if the routine design code adopted, the high capacity of the rock can not be fully utilized. The use of bolt at the bottom surface of the foundation integrates the foundation and the natural rock, hence reduces the foundation size and embedded depth to save the investment.

As the primary technique to offer safety and productivity improvement s for under- ground project s , rock bolt s have been widely used in t he construction of t raffic and hydro- power stations. The quality of the rock bolt s is of great importance and has been paid a lot of at tention to. This paper reviewed the history of some techniques used for the inspection of rock bolt s and analyzed their t heory and application. It point sout that the t heoretic p roblem is t he primary problem existed in t hese techniques.Nondestructive testing of bolt develops quickly with plenteous accomplishments and experiences.And we state these accomplishments mainly and look into the future.

Rock movement caused by external explosion loading can damage the nearby tunnel or cavern.To avoid damage, energy absorbing bolts with high load-displacement and large energy absorptioncapacities are required. The deformation and friction of the bolt absorb energy during the rock movementand preventing the structure from damage. To maximize the energy absorption capacity in the limitedspace inside the borehole, we developed a new bolt that utilizes the friction and plastic deformation ofthe sleeve. To develop the new bolt, FE simulation in Abaqus was used to improve designs beforefabrication. Two prototypes of the new design was fabricated and tested by static pull test. The resultsshowed the bolts yielded in the desired way. The experimental results prove the new bolt is capable ofabsorbing large amount of energy and accommodating large displacement.

Corrosion is a negative contributor on the structural integrity of rock bolt and leads to degradation of the mechanical properties of steel rock bolt. Exposure to chloride, seawater, salt and saltwater and deicing chemical environments influences rock bolt and weakens it. In order to evaluate the influence of corrosion and the size of the steel on the mechanical properties of rock bolt, an experimental investigation was conducted on rock bolt whose rebar is 8, 12, 16, and 18 mm diameter, and which were artificially corroded for 10, 20, 30, 45, 60, 90, and 120 days. By the simulation corrosion test of loaded and unloaded bolts in Na2SO4 solution, the relation curves of the mechanical performance with the corrosive conditions and the corrosion time are given. The mechanical performance is compared between these two types of bolts. At the same time, the influential trend of the load on the mechanical performance of the corroded bolt is analyzed. The laboratory tests suggest that corrosion duration and rebar size had a significant impact on the strength and ductility degradation of the specimens. after being corroded in Na2SO4 solution, both the ultimate bearing capacity and the maximal tensility of loaded bolt decrease far more than those of unloaded bolt, and the endurance and service life of loaded bolt will also be shortened much more severely. The tensile mechanical properties before and after corrosion indicated progressive variation and drastic drop in their values.

With the plenty of exploitation and application of underground space, the security of underground cavern under the explosive stress wave become the problem that urgent need to be solved. This article give a comprehensive description for the explosion stress wave disturbance effect of underground caverns from three aspects, (1) summarize the current research of the blasting load characteristics and its disturbance effect of the anchored caverns from theoretical research, experimental study and numerical simulation, etc.; (2) state the research status and achievements of rock bolt in anchored cavern under explosive stress waves; (3) according to the present problems of the research for explosion stress wave disturbance effect of underground caverns put forward that adopting multi parameters analysis method, utilizing the numerical simulation technology, the disturbance effect research of anchored caverns, which will be the future development direction.

The dynamic properties of rock bolts are characterized by measurement. The acceleration and strain of a rock bolt specimen were recorded using axial impact testing in laboratory environment. The systems dynamic properties such as natural frequencies and damping are characterized by using spectral analysis and Wavelet method. The characterized dynamic properties are used to update and calibrate a system simulation model, which is a multiple-degree-of-freedom system involving roof mass, the roof bolt, grout interface and head connections. The proposed approach enables accurately and effectively quantifying system dynamic parameters and establishing the analytical model for the design, development and performance monitoring of roof bolting systems.

Taking Liang Zhuang phyllite tunnel as the research object, the paper tries to analyze the variation rules of formation stress and initial support stress in the construction process based on numerical simulation of surrounding rocks grade III, IV and V, and also by using the measured data to have a better analysis of the stress state of surrounding rocks and support in the construction process, thus to grasp the rules for better construction. The result shows that the maximum compressive stress of initial support increases in the process of excavation, while the maximum formation stress is relatively stable in the process of excavation, with a slightly down trend, and whether there is a rock bolt or not, it doesnt have an obvious effect on the distribution and size of initial support stress.

Health monitoring of rock bolts can indirectly indicate the state of rock which is crucial for mining safety. This paper presents an innovative application of the Self-excited Acoustical System SAS for stress change measurement in rock bolts which are used to secure roofs and walls in mines and tunnels. The method gives information on the change of rock stress in the immediate area next to the bolt. It can be used also to determine the necessity of the exploited bolt replacement.

Using the software of ABAQUS,for the Geological conditions that the upper part is the clay and the Lower part is the rock..The model of digging plus rock bolt Complex environmentally undisturbed soil foundation combined with soil.Which analysis by the numerical simulation.Refer to the test compound type foundations Dimensions,get a three-dimensional finite element model.Applying the same concentration and test loads.Get the oad-displacement curve obtained by calculation.Measured values with the experimental results was very close to,This proved the feasibility of numerical simulation methods.

Based on the local deformation theory, we study the mechanics behavior of anchorage interface of full-length bonded rock bolt by using a mathematics model (tri-linear model). With pull-out load increasing, the changing process of anchorage interface of full-length bonded bolt is divided into three stages in this paper: elastic stage, plastic softening stage and crack slipping stage. It is found that in the state of elastic, axis force decreases rapidly with bolt depth increasing, and when pull-out load is greater than elastic ultimate load, attenuation degree will slow for the occurring of interface plastic softening and crack slipping in the top of bolt. The result indicates that the continuous change of axis force with bolt depth reflects that the bolt interface bond strength changes with the increase of pulling load.

Taking the method of shotcrete and rock bolt support can effectively keep slope stability and prevent soil erosion, but this method also makes the local microclimate change. This paper is to discuss the microclimate effect of revegetation on concrete slope, which take the excavated slope in Guandi hydropower station as the research object. The results show that, vegetation can significantly reduce the ground temperature and increase humidity on concrete slope, and adjust humidity changes. Especially under the conditions of high temperature in sunny day, the microclimate regulation effect of vegetation on naked slope is more obvious.

Gypsum breccia is a kind of soft rock-hard soil, and its component is complex. It has poor cementation, low intensity, strong water reaction, slight expansibility and corrosion. During the tunnel construction of gypsum breccia stratum, the mechanical characteristic of supporting structure is very complex. In order to ensure the safety, reasonability and economy of tunnel support system, it is important to acquire the information on displacement and stress of surrounding rock and support system. Two test sections are selected to monitor. Based on the measured data, the distribution characteristics and the time variation law of different kinds of support in gypsum breccia stratum are studied, including surrounding rock pressure, axial force of rock bolt, support pressure and stress. Such conclusions can be got: When strengthened lining (16# I-steel) of the V-grade surrounding rock used, support system performs well; but the stiffness of primary support is not enough if grillage lining is used. Growth of surrounding pressure is for a long time, which shows that the rock mass has Flow characteristics. Especially the surrounding rock pressure increases continuously. The spatial distribution is random, and the value is large. The stiffness of support system should be strengthened. Most blots at the waist arch are compressive. Bolts at the foot arch and sidewall are under tension. The maximum is nearly 124kN. Contact pressure between primary support and secondary lining at the sidewall is higher than that at arch parts. Steel frame stress comes up to 80% of the maximum within 20 days. Excavation of invert has great influences on stress state of surrounding rock and support system.

After the rock bolt or cable bolt installed in rock and soil mass, as the time goes on, the pre-stress load in bolt maybe losing. Through studying and analyzing the field test data, the factors leading to pre-stress losing are both external and internal factors. The internal factors are cable steel wire loose and rock and soil mass creep deformation. In which the cable steel wire has been pre-tensioned, its affection for load losing is very little. While the rock and soil mass creep deformations have great affection to pre-stress loss. There, if the cable bolt is installed in hard rock, the rock creep deformation will be very little and the load losing in cable bolt will be very few. But if the cable bolt is installed in soft rock and soil mass, the creep deformation will be very much greater than in hard rock, and the pre-stress losing in cable bolt will be very great. The external factors are shocking load, such as blasting load, storm rainfall, temperature change and stress change of anchored rock mass. Through analyzing these affecting factors, some recommend the compensative measures which include choosing appropriate steel wire, pre-tensioning and over-tensioning cable bolt, controlling the blasting rigorous and monitoring the cable long time enough in work time.

Rock anchor foundation can be widely used for the practical transmission line engineering in mountain areas. On strong-weathered sandstone ground, ten sets of uplift static load test of single rock anchor foundation were carried out. Based on the testing results, the typical failure modes and the ultimate uplift bearing capacity of foundations were obtained. Internal force distribution and effective anchorage depth were investigated through stain measurements. Design parameters of rock anchor foundation on sandstone ground were proposed, which can provide a reference for transmission line engineering design.

Taking +150 inclined shaft going through the soft rock strata at Muchengjian mine as the background, and based on the analysis of the deformation and failure feature of the roadway surrounding rock in the soft rock strata, this paper makes X-Ray Differaction (XRD) phase analysis of the soft rock; using finite difference numerical software FLAC3D, it stimulates and makes comparative analysis of the stress and deformation distribution characteristics of the roadway surrounding rock with bolt support with different intervals, and the support of the high-strength bolt with high pre-tension stress in the inclined shaft through the soft rock strata. The results show that the roadway surrounding rock in the +150 inclined shaft at Muchengjian mine is swelling soft rock prone to softening, degradation and swelling in water, which is bad for the roadway support; different types of rock strata have significant different impact on the stress and deformation of the roadway surrounding rock; for the soft rock roadway, the increased pre-tension stress of the bolt can cause higher compressive stress in the roadway surrounding rock and reduce the tension failure of the surrounding rock;compared with the end anchorage, the full-size anchorage with high pre-tension stress can cause the overlap of the conical compressive stress zone and enhance the roadway overall support.

Support of soft rock is a big challenge in all mines at home and abroad. Soft rock is of different kinds of rheological property for geological conditions, mine ground pressure and so on. It brings about really difficult problem to roadway support. In order to ensure safety application and prolong usage, shaft station need to be reinforced. Sight instrument was used to analyze broken conditions. The results show that the broken depth in roof rock is 5~6 m, and greater than 4 m in sidewalls. According to failure characters and sight results, we determine that rock of shaft station belongs to high geo-stress and jointed soft rock. On this basis, technology of grouting reinforcement combined with cable anchor support is carried out. Monitoring results of surface convergence and cable force show that bearing capacity of surrounding rock increases obviously, roadway contraction and floor heave are well controlled.

Based on the introduction of the researches on the influence of the surrounding rock strength on the anchorage performance of resin anchored bolts at home and abroad, the numerical simulation was adopted to analyse anchorage system of single bolt support small-scale by using the finite difference program FLAC3D. The results showed that the stress distributions in resin capsules and surrounding rocks were different with the different strengths of surrounding rocks. The stresses in the surrounding rocks gradually decreased with the reduction of rock strength, but the plastic zone gradually expanded. On the basis, such technological approaches were brought forward to ensure support effect in the soft rock roadways by improving the materials and formulations of the resin capsules and increasing the support density and the anchorage length appropriately.

Bad and asymmetrical deformation occurred in soft tilted strata roadway for the existence of tectonic stress, we carried out the study on geostatic stress character and optimizing bolting support parameters in 2# coalbed of Zijin Colliery. Based on original rock stress measurement, broken rock zone measurement and survey of roadway deformation, characters of original rock stress and range of broken rock zone were given. According to existent problems, a variety of numerical computations were carried out by FLAC3D, failure mechanism of roof is shear-tensile failure. New support methods of bolt installed vertically in tilted roof and strengthening support of sidewalls and corners of roadway are figured out. The research was carried out for 600 meters. The monitoring results prove that the optimized support design is viable and the new bolting parameters are reasonable.

A tunnel in Chengde collapsed several times and cracks existed in the second lining. Using non-destructive testing equipment, tunnel support was detected to find out the hidden trouble early. In the section of K16+890~K16+950, the quality of tunnel support was assessed, with GPR and anchor measuring apparatus. In the tunnel, the thickness of composite lining was 25cm, and the second lining was 38cm, both of which met the design requirements. Positive peak method was selected to locate on I beam. The average longitude space of I beam was 127cm, while the design value is 120cm. Many rock bolts was lacked at the right crown. Moreover, the bolts in the haunch did not kept in diamond layout, close to I beam. Through analyzing waveforms of impact-echo, the number of qualified bolts only made up 74 per cent of the total bolts. The large space of I beam led to the lack of holding power. Meanwhile, the disqualified bolts limit the coordination deformation between surrounding rock and support. All the support defects led to tunnel collapse. These tests results demonstrate that NDTcan be used to mitigate the risks of tunnel construction.

This present paper adopts a constitutive model for elastic damage of intermittently jointed rock mass, damage-evolution equations and a supporting model of damaged rock-bolt bar(DRBB) element to simulate effect of reinforcement. The results have indicated that the above method well describes the progressive failure process of the surrounding rock mass and the anchorage effect. The theoretical achievements are of referential value to designers.

In the deep rock mass surrounding, rock burst, large deformation, zonal fracturing and phenomena like these may occur in the tunnel excavation process. When zonal fracturing happens, it is essential to reconsider the types of support, the boundary of support and the approach of tunnel excavation. In this paper, the control theory about the surrounding rock stability under high pre-existing stresses was researched, and the efficient support form which was the combination of high strength anchor bar and anchor cable was ascertained to be adaptive to deep tunnel excavation. According to the deformation and zonal fracturing mechanism of the surrounding rock, a comprehensive support program that combined intensive short anchor bars and long anchor cables was established, and the numerical simulation was carried out to verify the feasibility of the support form.

broken rock zone is the main reason for the convergence of surrounding rock deformation, and its thickness not only is a reflection of many factors which influence the stability of surrounding rock, but also is the results of the interaction of many factors, a comprehensive classification index. Roadway support design based on classification result of broken rock zone, has a solid theoretical foundation, and the field application effect is remarkable.

The 5204 transport roadway roof displacement encountered during the tunneling and mining is more than 240mm, which severely damaged the shape of the roadway. The anchor cable of the top is pulled off and supporting failure takes place. According to the analysis of the surrounding rock pressure behavior law, the concept of supporting new technology based on the concept of "coordinating role of long bolt - surrounding rock" is brought up. This technology can achieve a reasonable match of the supporting object with the displacement and support strength of the surrounding rock. Based on this concept, FLAC3D numerical simulation analysis, combined with the engineering analogy method, produces the long bolting parameters on the 5402 transport roadway. The industrial test results show that in the mining face, the force state of the long bolt is good. When larger displacement in the roof appears, the long bolt is not pulled off and the support failure does not occurs .It means the long bolt has adapted the large deformation of the roadway roof. The research results can provide a reference for similar mechanized caving roadway supporting.

The effect of feet-lock bolt was studied in the rheological surrounding rock by numerical simulation. The results show: feet-lock bolt can improve the force state of vault, feet-lock bolt and grouting can improve the effect of vault stress state better in weak rock. After invert is applied, invert become the main load-bearing structure, the function of feet-lock bolt is greatly reduced after invert applied.

Treating surrounding rock as absolutely loose mass helps to determine positions of the four key reinforced points in roadway, in other words, they are juncture locations between 45 degrees angle directions of two arch haunches and two footwalls. Surrounding rock deformation can be effectively controlled with the help of reinforcement on key reinforced points, furthermore, it is possible to save lots of supporting materials, in short, it is a very effect way. New technology proposed in this paper what is about stable augmentation has deeply unearthed important effect of anchor in floor of roadway, it argues that anchor in floor has quadruplex efficacies: transferable effect of surrounding rock stress, displacement boundary effect, decreasing equivalent stress of basic angle area and the inverted wedge effect, so it can suppress floor heave effectively, and this lays a solid foundation for roadway stability. Article deeply analyzed basic mechanism about deformation of roadway under loading, exposed essentiality of roadway support, and provided important theoretical basis for floor heave control emerged more and more frequently in deep mine roadway. Key words: broken rock zone, bolt support, floor heave, equivalent stress

High stress in the surrounding rock mass causes serious stability problems. The applied support system used in this conduction should be able to carry high loads and also accommodate large deformations without experiencing serious damage. In this paper, a brief overview of the history of yielding/energy-absorbing rock bolts is provided. And then, a new yielding bolt invented by the author is introduced in detail, including its layout and principle. Theoretical analysis shows that the bolt has large load-bearing and deformation capacities, thereby absorbing a large amount of energy to maintain the stability of surrounding rock.

The effect of the roadway with no supporting and roadway that was reinforcement by rock bolts and anchor robs, anchor rod combined bolting shoring, anchor rod combined anchor rope and lining timbering was simulated by using numerical simulation software FLAC3D. The results showed that the deformation of no supporting roadway is maximal, and the maximal position is vault. The displacement of top floor and two side decreases after supported, which can reinforce surrounding rock. The reinforcement effect of the anchor rod combined anchor rope and lining timbering is best.

Based on the deep soft rock creep mechanism, according to the physical characteristics of bauxitic mudstone in ingate at the level of -1015 m of Kong Zhuang colliery, we solved the technical difficult problem of choosing anchor points of soft rock supporting roadway in ingate. Using high strength and low relaxation steel strand to reinforce by crossed anchor, in combination with the depth hole grouting technology, improve pressure-bearing capacity of wall rock in the ingate, safe passage and drainage pipe area. We analyze the stress distribution characteristics of rock mass, contrasting on the stress distribution at the end of partially grouted bolt and the rock mass. Practice shows that crossed anchor rock mass has triaxial compression over all, the bunch body has a single structure, and it is easily to be analyzed. We not only control the roof settling in the area of ingate is, but also solve the floor heave problem in safe passage and drainage pipe area.

It is of great significance to select the reasonable support pattern and support parameters for accurately determining the magnitude of the broken rock zone of roadway. At present, the test methods of the broken rock zone of the roadway surrounding rock all have stated disfigurements and deficiency. The borehole imaging method has advantages: simple operation and the test results being intuitive and reliable. The test results and analysis of the broken rock zone of rail crossheading in 3down 109 coal face of Luxi Coal Mine show that the test results consistent well with the actual situation and they have practical reference value for the test and application of the broken rock zone of the roadway surrounding rock.

soft rock; parameter; bolt-mesh-anchor support; ground pressure.

The damage features of surrounding rock in the process of bottom excavation in deep hard rock tunnel were investigated, combining with the actual tunnel data of JinpingⅡHydropower Station and using numerical simulation approach. The evolution mechanism of microfractures initiation, growth and expansion in deep intact rock mass was performed. It’s shown that the fractures caused by bottom excavation develop to deeper surrounding rock due to stress adjustment, and the zone that have been supported also has some damage. The research results provide important references to understand the damage features of surrounding rock in deep hard rock under high geostress.

For the purpose of stability of surrounding rocks of tunnel during the stage of construction and operation, a series of monitoring methods and measurement are carried out to investigate performance of Heishan tunnel through selecting 5 cross sections for monitoring. Based on the monitoring data, convergence around tunnel, displacement of different points of interior of surrounding rock, axial forces of rock bolts and pressure of surrounding rock are analyzed. The characteristics of selected cross sections are useful for engineers to optimize the preliminary design of tunnel. Furthermore, the study results can be used to guide the design, monitoring and construction for future tunnels with the similar geological condition.

Slope excavations are often constructed in stratified host rock masses in practice. The stratification in a rock mass is generally characterised by its planar geometry and persistence. The mechanical properties of the joints dictate both the deformation and strength characteristics of the stratified rock mass. Thus, it is imperative that the influence of the joints be incorporated in any type of load-deformation analysis of slope excavations in layered rock masses. Rock bolts have been widely used as the primary support system to stabilize the rock masses of slope. In general, rock bolts reinforce rock masses through restraining the deformation within rock masses and reduces the yield region around the excavation boundary. In order to improve bolting design, it is necessary to have a good understanding of the behaviour of rock bolts in deformed rock masses. In the present paper, the numerical analysis method is adopted to built the three springs bolt element; then the excavation in the stratified rock slope is simulated to improve the understanding of the slope deformation and bolt mechanical characteristic.

The properties of a longitudinal guided wave with central frequency 5kHz propagating in partially grouted rock bolts were studied by experimental and numerical simulation methods. The guided wave was excited by the impact–echo method on the free end of the bolt, and the excited wave measured in the experiments was used as excitation input in the numerical simulation. The numerical results match well with the experimental ones. Two empirical formulas were obtained for when the reflected waves from the upper interface and from the embedded end of the bolt could be distinguishably detected. Conclusion is drawn from the simulation results that the guided wave energy velocity in the embedded section of the bolt increases with the increase of elastic modulus of the grout media. A new method was proposed for anchorage quality testing and its effectiveness was proved by a testing example.

High frequency longitudinal guided waves were used to inspect the anchored rock bolts. Experiments were conducted to find the optimal frequencies for the bolt testing. A broad-band signal was excited at the top end of the bolt, and the power spectral density(PSD) analysis of the bolt end reflected waves was made. Base on that the frequency component of the bolt end reflected waves could be obtain, and the frequencies with higher power spectral density values are the optimal ones. At optimal frequencies, the guided wave attenuates more slightly than it is at other frequencies and the bolt end reflected waves can be clearly acquisitioned. Experimental results show that the optimal frequencies of guided wave in a free bolt and in an anchored bolt are quite the same, and they are mainly affected by the bolt instead of the anchor media. Conclusions can be drawn that the propagation velocities of guided wave at optimal frequencies in a free bolt are close to those in the embedded section of the bolt. As a result, the bolt length and the position of flaw in the anchored bolt can be determined by the guided wave velocity in a free bolt and the reflected wave from the bolt end and from the flaw, respectively.