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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.

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

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Based on the practical engineering ,by using the 3D-FEM of elastic-plasticity, a reasonable model for simulation of tunnel excavation and shotcrete lining and rock bolts builds up, surrounding rock using Mohr-Coulomb constitutive model of ABAQUS, lining using Concrete Damaged Plasticity constitutive model, and bolt using elastic-plasticity constitutive model. By using strength reduction finite element method, analysis for safety coefficient of stability of surrounding rock with primary shotcrete lining and rock bolts under the four limit state criteria. It is concluded that the appearance of divergence of the computation may precede by displacement of characteristic points, The safety coefficient of the running-through of the plastic zone of the surrounding rock and the running-through of the plastic zone of the shotcrete and a great amount of rock bolts yielding are less than the divergence of the computation and displacement of characteristic points.

With the increasement of mining depth, the strata behavior of the roadway is obvious. As the stress of surrounding rock increases, the bottom of the soft rock roadway becomes deformed easily compressed by its top rock and two sides rock, which leads to the occurrence of the pucking and roadway destruction. Aiming the air inlet roadway destruction phenomenon of -450th level powder magazine in Hebi Zhongtai Mining Co.Ltd, the geological condition and the mechanism of the roadway failure are analysed comprehensively, and the bolt-grout supporting method is also proposed in this paper. At last, the deformation and heaving floor are controlled effectively which is proved by the field monitoring results.

A numerical simulation method of the rock bolts non-destructive testing based on ANSYS is presented. ANSYS/ LS-DYNA which is a kind of software of rock bolts dynamic finite domain analysis is used to establish a three-dimension model, after sine curve excitation is loaded, the reflection curve of naked rock bolts, or rock bolts with different defects are got, and the relationship curve between elastic modulus and stress wave velocity are got correspondingly. Experiment result proved that the aboved method was satisfied to simulate the stress wave propagation and the reflection situation in the rock bolts.

The effect of anchor on fractured rock specimens in splitting test is simulated by DDARF method in this research. The results are compared and agree well with laboratory test results. The DDARF program is also adopted to analyze the stability of an underground cavern with four groups of randomly generated joints in the surrounding rocks, in which two conditions with and without rock bolts are considered. Besides, the crack propagation process around the cavern and the displacements of key points in the surrounding rock are monitored and applied to investigate the stability of the cavern.