Rockburst Tendency Research Articles

Research Progress on the Mechanisms and Control Methods of Rockbursts under Water–Rock Interactions

Rock bursts are among the most severe and unpredictable hazards encountered in deep rock engineering, posing substantial threats to both construction safety and project progress. This study provides a comprehensive investigation into how moisture infiltration influences the propensity for rock bursts, aiming to establish new theoretical foundations and practical methods for their prevention. Through the analysis of meticulous laboratory mechanical experiments and sophisticated numerical simulations, we analyzed the variations in the physical and mechanical properties of rocks under different moisture conditions, with a particular focus on strength, brittleness, and energy release characteristics. The findings reveal that moisture infiltration significantly diminishes rock strength and reduces the likelihood of brittle fractures, thereby effectively mitigating the risk of rock bursts. Additionally, further research indicates that in high-moisture environments, the marked reduction in rock burst tendency is attributed to increased rock toughness and the suppression of crack propagation. This study advocates for the implementation of moisture control measures as a pre-treatment strategy for deep rock masses. This innovative approach presents a viable and effective solution to enhance engineering safety and improve construction efficiency, offering a practical method for managing rock burst risks in challenging environments.

Mechanical mechanism analysis of rockburst in deep-buried tunnel with high in-situ stress

The Qinling water conveyance tunnel has a large buried depth and high in-situ stress level, and rockburst disasters frequently occurred during excavation. In order to find out the mechanical mechanism of rockburst, the research work in this paper is as follows: (1) In-situ three-dimensional hydraulic fracturing method was used to measure the in-situ stress of the deep buried tunnel crossing the ridge. (2) Based on the measured in-situ stress results, the stress distribution characteristics of the tunnel crossing the ridge were obtained by the multiple linear regression method, and the rockburst tendency during construction was predicted. (3) A three-dimensional numerical model of tunnel excavation was established to analyze the dynamic adjustment characteristics of the surrounding rock stress and elastic strain energy during TBM excavation, and to clarify the mechanical mechanism of rockburst. The research results show that the maximum principal stress of the deep-buried tunnel crossing the ridge of Qinling is 40–66 MPa, which belongs to extremely high in-situ stress level, and medium-strong rockburst may occur during excavation. In the process of TBM excavation, the stress of the surrounding rock in the range of 2.6 times the diameter of the tunnel before and after the working face is adjusted violently, and the concentrated zones after the stress redistribution are mainly distributed in the arch roof and arch bottom, and the stress concentration coefficient can reach 2.06. The arch roof, arch waist, and arch bottom are susceptible to immediate rockburst due to stress transient unloading at the moment of excavation. After the elastic strain energy of the surrounding rock at the arch roof and the arch bottom is released and accumulated, it is easy to cause time delayed rockburst, and the depth of the rockburst pit can reach 3.5 m, which is consistent with the rockburst phenomenon in the field.

Study on the size effect of rock burst tendency of red sandstone under uniaxial compression

The study of rock burst tendency of rock masses with different sizes plays a key role in the prevention of rock burst. Through theoretical analysis, it is proposed that uniaxial compressive strength and deformation modulus ratio are the key mechanical parameters affecting rock burst occurrence. In order to find out the size effect of uniaxial compressive strength and deformation modulus ratio, theoretical analysis and uniaxial compression experiment are carried out on rock samples with different heights, different cross-sectional areas and different volumes. The results show that the smaller the uniaxial compressive strength is, the larger the deformation modulus ratio is, and the more likely rock burst are to occur. On the contrary, rock burst is still not easy to generate. The uniaxial compressive strength of rock samples with different heights, different cross-sectional areas and different volumes increases with the increase of rock sample size. The deformation modulus ratio of rock samples with different heights and different volumes shows an upward trend on the whole, while that of rock samples with different cross-sectional areas shows a downward trend on the whole. The fracture forms of rock are analyzed using the energy conversion law in the process of deformation and failure for three kinds of rock with different shapes and sizes.

Rockburst hazard assessment and prevention and control strategies in the Ruihai gold mine

Ruihai gold mine is a super large underwater gold mine with an initial mining depth of more than 1,400 m. Deep mining may face rockburst disaster. In order to scientifically control the potential rockburst risk, ensure the safety of underground personnel and equipment, and realize the safe and efficient mining of the mine, it is necessary to evaluate the rockburst risk of the mine and formulate appropriate rockburst risk warning and mitigation strategies. XRD mineral composition analysis and conventional rock mechanical tests were carried out on the parent rock granite samples. The results show that there are differences in the lithologic composition and rock mechanics parameters of the three colors of granite, which are preliminarily determined as three kinds of granite; The rockburst tendency of three kinds of granites is evaluated by using three classical rockburst criteria, and the discrimination results of the three rockburst criteria are not completely consistent or even contradictory. The application limitations rockburst risk assessment based on index criteria are discussed and analyzed in detail. It is proposed to apply microseismic monitoring technology to warn and manage the rockburst risk of Ruihai gold mine in development and mining stages, and put forward microseismic monitoring layout schemes and targeted rockburst prevention and control measures in different stages. The research results can provide reference for similar projects.

Experimental Study on Mode I Fracture Characteristics of Granite after Low Temperature Cooling with Liquid Nitrogen

Liquid nitrogen fracturing has emerged as a promising technique in fluid fracturing, providing significant advantages for the utilization and development of geothermal energy. Similarly to hydraulic fracturing in reservoirs, liquid nitrogen fracturing entails a common challenge of fluid–rock interaction, encompassing the permeation and diffusion processes of fluids within rock pores and fractures. Geomechanical analysis plays a crucial role in evaluating the transfer and diffusion capabilities of fluids within rocks, enabling the prediction of fracturing outcomes and fracture network development. This technique is particularly advantageous for facilitating heat exchange with hot dry rocks and inducing fractures within rock formations. The primary objective of this study is to examine the effects of liquid nitrogen fracturing on hot dry rocks, focusing specifically on granite specimens. The experimental design comprises two sets of granite samples to explore the impact of liquid nitrogen cooling cycles on the mode I fracture characteristics, acoustic emission features, and rock burst tendency of granite. By examining the mechanical properties, acoustic emission features, and rock burst tendencies under different cycling conditions, the effectiveness of liquid nitrogen fracturing technology is revealed. The results indicate that: (1) The ultimate load-bearing capacity of the samples gradually decreases with an increase in the number of cycling times. (2) The analysis of acoustic emission signals reveals a progressive increase in the cumulative energy of the samples with cycling times, indicating that cycling stimulates the release of stored energy within the samples. (3) After undergoing various cycling treatments, the granite surface becomes rougher, exhibiting increased porosity and notable mineral particle detachment. These results suggest that the cyclic application of high-temperature heating and liquid nitrogen cooling promotes the formation of internal fractures in granite. This phenomenon is believed to be influenced by the inherent heterogeneity and expansion–contraction of internal particles. Furthermore, a detailed analysis of the morphological sections provides insights into the structural changes induced by liquid nitrogen fracturing in granite samples.

Development and performance study on low strength and high rockburst tendency similar simulation material of coal

The current similar simulation materials (SSM) are featured with the contradiction between low strength and high rockburst tendency (RT), thus being unable to simultaneously realize the qualitative rockburst of small size specimen and the impact damage restoration of large size model. In this case, this study developed a new SSM of low strength and high RT by using water glass (WG) as cement, talcum powder (TP) as aggregate and adding curing agent sodium silicofluoride (SSF). Under the requirements of initial set volume shrinkage rate (IVSR), long-term volume decay rate (LVDR), uniaxial compressive strength (UCS) and modulus index (MI), the optimal ratios of SSF and TP were obtained 20% and 70% by orthogonal experiment and multiple linear regression method, respectively. Micro-macroscopic experiments such as uniaxial compression, scanning electron microscope (SEM), acoustic emission (AE) and Infrared thermal imager were utilized to monitor in real time the energy-temperature-strength synergistic change characteristics and similarities between this material and the coal with a strong RT. The experimental results show that: the UCS value of this material is 6.11 MPa and its MI is 11.57, which meets the requirements for low strength and high RT. Meanwhile it satisfies a certain similar proportionality between its physical parameters and those of coal. In the whole process of uniaxial compression, there are energy and temperature homologous changes in the characteristics of consistency, and both materials conform to the stress–strain phase law. The infrared radiation temperature displays a trend of “slowly decreasing-gradually warming-continuously cooling-suddenly warming-sharply cooling”. The AE energy count rate shows a trend of “calm transition and sudden increase before and after the stress peak”. All are characterized by strong RT. There is still some difference between the two specimens during energy and temperature changes, due to their different molding characteristics and load-bearing capacity. The feasibility of the material was confirmed in terms of physical parameters, degree of rockburst and homologous energy and temperature characteristics. Meanwhile, this study revealed the multi-parameter precursor characteristics of rockburst damage in the specimen, which can lay a foundation for the prevention and study of impact ground pressure disaster.

Numerical study of mechanical properties and microcrack evolution of double-layer composite rock specimens with fissures under uniaxial compression

Layered and heterogenous fissured rock masses are ubiquitous in nature. Fissures exert significant influence as release surfaces and nucleation sites for failure in layered rock masses. However, key mechanisms controlling microcrack initiation and extension in layered and heterogenous rock masses remain unclear. We complete a suite of numerical (granular mechanics) and complementary physical compression experiments on layered rocks containing fissures in different modalities where the overlying layer is both stronger and stiffer. We complete this to understand the impact of local specimen and system stiffness on ultimate strength and modes of failure (stability). We systematically examine the influence of fissure angles, lengths and positions on the mechanical response, including observations of microcrack evolution and tendency for instability (i.e. rock bursting), constrained by acoustic emission (AE). Peak strength and overall elastic moduli vary in a predictable and systematic manner. The strengths and stiffnesses of the double-layer composite specimens fall between those of the homogeneous weak and strong single layer specimens. The AE counts, micro crack growth and failure characteristics of the double-layer composite specimens are closely related to the fissure angles, lengths and positions. Whether the weak rock or the strong rock contains fissures, the rock burst tendency of the double-layer composite specimens decreases in varying degrees–defining the potential of pre-blasting/fracturing to soften the mass. Fissure angles and lengths do not have to be too large. Additionally, failure in the double-layer composite specimens results not only from crack propagation in the weak layer, but also failure of the entire specimen when the length of the fissure in the strong layer is sufficiently large. These observations provide a reference for stability evaluation and disaster mitigation of layered rock masses in engineering.

An insight from energy index characterization to determine the proneness of rockburst for hard rock

The evaluation index and classification criterion of coal bursting liability are often used to evaluate hard rock rockburst proneness. In view of the great difference between the engineering conditions of embedding rocks (hard) and coal seam (softer), the evaluation results of rockburst proneness of hard rock are not accord with the actual situation. Aiming at this problem, rockburst tendency indices were studied by laboratory test in this paper. Based on the analysis of the data, it is concluded that the peak-strength strain energy storage index WETP and residual elastic energy index AEF can reflect the energy and rockburst proneness of hard rock from the elastic energy storage and residual elastic energy. By designing the cyclic loading and unloading test and the uniaxial compression test of rock, the loading rates of the above two kinds of energy indices were determined, and the determination and calculation process of the above two kinds of energy indices were clarified. The experimental results show that the linear elastic energy storage law obtained by cyclic loading and unloading of one sample is not very different from that obtained by multiple samples, both methods can be used for measurement. The peak-strength elastic energy density, pre-peak total input energy density and post-peak failure energy density of rock increase slightly with the strain rate, and the degree of rock fragmentation also has the same trend. The energy index of rock cannot fully reflect the rockburst proneness of rock. Based on the test process and results, in the case of hard rocks, 0.3–1 mm/min could be used for displacement control mode, and 50–140 kN/min should be used for load control mode. Extensometer or instrument sensor can be the strain acquisition methods.

Measurement and Classification Criteria of Strength Decrease Rate and Brittleness Indicator Index for Rockburst Proneness Evaluation of Hard Rocks.

Rockburst is one of the common geological hazards. It is of great significance to study the evaluation indexes and classification criteria of the bursting liability of hard rocks, which is important for the prediction and prevention of rockbursts in hard rocks. In this study, the evaluation of the rockburst tendency was conducted using two indoor non-energy indexes, namely the brittleness indicator (B2) and the strength decrease rate (SDR). The measuring methods of B and SDR as well as the classification criteria were analyzed. Firstly, the most rational calculation formulas for B and SDR were selected based on previous studies. The B2 equaled to the ratio between the difference and sum of uniaxial compressive strength and Brazilian tensile strength of rocks. The SDR was the average stress decrease rate of the post-peak stage in uniaxial compression tests and equaled the uniaxial compressive strength dividing the duration time of post-peak rock failure in uniaxial compression tests. Secondly, the uniaxial compression tests of different rock types were designed and carried out, and the change trend of B and SDR with the increase of loading rate in uniaxial compression tests were studied in detail. The results showed that after the loading rate was greater than 5 mm/min or 100 kN/min, the B value was affected, limited by the loading rate, while the SDR value was more affected by the strain rate. The displacement control, with a loading rate of 0.1-0.7 mm/min, was recommended for the measurement of B and SDR. The classification criteria of B2 and SDR were proposed, and four grades of rockburst tendency were defined for SDR and B2 according to the test results.

Stability Index of Surrounding Rock during Deep Rock Excavation Considering Energy Release Speed

Rockburst is a kind of dynamic rock failure process that is easily induced by the excavation of a high-stress rock mass. However, from an energy perspective, the existing indexes for rockburst tendency have a limitation in that they do not consider the energy release speed. In this study, energy release effectiveness was proposed based on the local energy release rate while considering the influence of the energy release speed. The index can evaluate the stability of surrounding rock during the excavation of high-stress rock. The index can be obtained by recording the strain energy density of every element in the model during excavation and identifying the maximum strain energy density (Eimax), the minimum strain energy density (Eimin), the maximum time (timax), and the minimum time (timin) to calculate energy release speed and energy release effectiveness. A case study of the excavation of an experimental tunnel, namely, the URL of AECL, was adopted to validate the index. The results indicated that the proposed index can clearly identify the location and strength of the impact tendency area, and it can be effectively applied to the stability analysis during the excavation of deep tunnels.

Study on Rockburst Tendency of Deep Underground Engineering based on Multi-Factor Influence

Rockburst disaster seriously threatens the construction schedule of underground tunnel engineering and the safety of construction workers. Rockburst prediction has become one of the critical methods for evaluation of surrounding rock stability and safe construction of deep underground engineering. To further understand the occurrence mechanism of rockburst disaster and predict rockburst in underground engineering more accurately, firstly, the typical rockburst tendency criterion and the critical factors affecting the rockburst development process are systematically summarized and analyzed, and the main control factors reflecting the whole process of rockburst development are screened and analyzed: mechanics, brittleness, integrity, and energy storage factor. Secondly, according to the comprehensive consideration of the main control factors, based on the energy conversion and overall failure mechanism in the process of rock failure, a new multi-parameter rockburst tendency criterion is proposed by comprehensively considering the stress states of rock unit under different stress paths. Finally, the rockburst criterion proposed in this paper is applied to typical engineering cases to verify its rationality and accuracy. Based on a rockburst section in the Sangzhuling tunnel, the possible location of rockburst is simulated based on the 3D discrete element numerical simulation platform, and the rockburst criterion proposed in this paper is further verified by actual engineering. The results show that: the rockburst criterion considering the mechanical factor(σθ/σc), brittleness factor(σc/σt), integrity factor (Kv) and energy storage factor (Ue/U0) can comprehensively and truly reflect the rockburst development process; based on the rockburst tendency criterion proposed in this paper, the occurrence of rockburst in typical engineering cases is calculated and verified, and the predicted results are in good agreement with the actual situation; the numerical simulation of the typical rockburst section prediction in the Sangzhuling tunnel shows that the distribution characteristics of rockburst tendency based on the criterion in this paper are consistent with the on-site rockburst occurrence, and there is a strong rockburst tendency on the right of the tunnel vault, which further verifies the effectiveness and engineering applicability of the criterion in the rockburst tendency prediction. The results of the research can provide some reference for predicting the tendency of rockburst in deep underground engineering.

Evaluation of Rock Burst Propensity and Rock Burst Mechanism in Deep Phosphate Mines: A Case Study of Sujiapo Phosphate Mine, Hubei Province, China

Rockburst is one of the major problems in rock underground engineering and mechanics. To make a risk assessment of rockburst and improve the mine safety index, some evaluation systems for rockburst propensity have been proposed and applied, and progress has been made in the study of high-value mines and single evaluation systems, but these evaluation systems are still immature for deep low and medium grade phosphate mines with more complex influencing factors. Therefore, to solve this problem, this study takes the phosphate mining area of the Sujiapo phosphate mine as the main research object, and combines the characteristics of the deep rockburst of the phosphate mine and its physical and mechanical properties; the evaluation system combines fuzzy mathematical method and multiple evaluation methods to determine the propensity of rockburst of deep mining of Sujiapo phosphate mine. The JSM-500LV SEM and acoustic emission results are used to analyze the microscopic mechanism of rockburst from the morphology and composition of the rocks, and the rationality of the evaluation system is further demonstrated. The study shows that dolomite and phosphorite in the study area are moderate rockburst, and shale has a weak rockburst tendency; because the roof dolomite and phosphorite crystallization degree are higher, the elastic modulus is large. Under the action of external load, the roof dolomite stored more elastic strain energy. Deformation damage consumes less energy. The energy released to the outside world after the damage is large, more likely to occur brittle damage, and the rockburst tendency is high. Therefore, the evaluation system combining multiple evaluation methods can comprehensively determine rockburst in phosphate mines.

Experimental Investigation of Pre-Flawed Rocks under Dynamic Loading: Insights from Fracturing Characteristics and Energy Evolution.

Different fractures exist widely in rock mass and play a significant role in their deformation and strength properties. Crack rocks are often subjected to dynamic disturbances, which exist in many fields of geotechnical engineering practices. In this study, dynamic compression tests were carried out on rock specimens with parallel cracks using a split hopkinson pressure bar apparatus. Tests determined the effects of strain rate and crack intensity on dynamic responses, including progressive failure behavior, rock fragmentation characteristics, and energy dissipation. Based on the crack classification method, tensile-shear mixed cracking dominates the failure of rock specimens under the action of impact loading. Increasing the flaw inclination angle from 0°-90° changes the predominant cracking mechanism from tensile cracking to mixed tensile-shear cracking. The larger the loading rate, the more obvious the cracking mechanism, which indicates that the loading rate can promote the cracking failure of rock specimens. The fragmentation analysis shows that rock samples are significantly broken at higher loading rates, and higher loading rates lead to smaller average fragment sizes; therefore, the larger the fractal dimension is, the more uniform the broken fragments of smaller sizes are. Energy utilization efficiency decreases while energy dissipation density increases with increasing strain rate. For a given loading rate, the energy absorption density and energy utilization efficiency first decrease and then increase with increasing flaw inclination, while the rockburst tendency of rock decreases initially and then increases. We also find that the elastic-plastic strain energy density increases linearly with the total input energy density, confirming that the linear energy property of granite has not been altered by the loading rate. According to this inherent property, the peak elastic strain energy of the crack specimen can be calculated accurately. On this basis, the rockburst proneness of granite can be determined quantitatively using the residual elastic energy index, and the result is consistent with the intensity of actual rockburst for the specimens.

Acoustic Emission Parameter Characterization of Damage Process of the Limestone with Different Rockburst Tendencies

The laboratory discrimination tests of the rockburst tendency and AE tests under the uniaxial compression were conducted on the limestone. Three criterions were used to judge the rockburst tendency of the limestone with a buried depth of 600–1000 m under the same borehole. The rock damages were quantified by the AE events, ring count and energy. The fractal characteristics of these parameters were compared and analyzed. The characterization accuracy of these parameters on the damage process of the limestone with different rockburst tendencies was discussed. The AE parameters of the limestone with different rockburst tendencies increase sharply when the stress is near its peak. With the increase in the rockburst tendency, the variation of the AE event rate and ring count of the limestone is more and more consistent with the AE energy. Based on the characterization of the AE events and ring count, the damage process is characterized by a gradual evolution, while based on the energy characterization, it is characterized by a stepped evolution. The damage represented by the AE energy reveals the intensity and instantaneity of the rockburst failure. According to the verification of the CV value, the fractal dimension D of the AE energy fluctuates more gently with the increase in the rockburst tendency. It reflects the energy storage characteristics of the rock with a rockburst tendency in the loading process, which is consistent with the failure mechanism of the rockburst. Therefore, AE energy is more accurate to characterize and predict the failure of the limestone with a rockburst tendency.

Research on Multifactor Analysis and Quantitative Evaluation Method of Rockburst Risk in Coal Mines

Abstract The prevention of rockbursts is significant to ensure mining safety in deep coal mines. The multifactor analysis and a new quantitative evaluation method for rockbursts in coal mines are proposed in this study. In the aspect of rockburst analysis, a multifactor system of rockburst risk based on the material, stress, and large-scale geological structure is proposed. The factors influencing rockbursts in coal mines are analyzed by numerical simulations. Based on a standard mining model, three comparative models considering the rockburst tendency, high stress, and geological structure are established. The distribution of maximum principal stress and plastic zone during the mining process is compared. The reasons why these three types of factors are liable to trigger rockbursts lie in generating high-stress zones in surrounding rock masses. In the aspect of quantitative evaluation, the monitored microseismic signal is selected as the key indicator, and the daily frequency of microseisms is analyzed. A normal distribution function based on the daily frequency of microseisms is established. The interval of daily frequency of microseisms is set to judge whether the microseismic frequency is abnormal and then determine the rockburst risk of coal mines. Considering the results of multifactor analysis, it is proposed that the monitoring system combining microseisms with stress is the direction to accurately and quantitatively evaluate the rockburst risk in the future. This study makes specific explorations in the quantitative evaluation of rockburst risk in coal mines.

Mechanism Study and Tendency Judgement of Rockburst in Deep-Buried Underground Engineering

Rockburst is a type of dynamic instability failure phenomenon and frequently brings huge losses to underground engineering projects such as mines and tunnels. In order to explore rockburst mechanisms and predict rockbursts better, relying on the background of Wulaofeng deep-buried highway tunnel, in situ stress measurement was performed using new wireless devices, and mechanics tests of surrounding rock samples taken from different burial depths were carried out. The rockburst mechanism was explored from the microscopic perspective based on the analysis of scanning electron microscopy (SEM). Rockburst tendency was judged comprehensively by a tendency analysis, grade prediction and numerical simulation. The result showed that the mechanical parameters of granite rocks in the deep-buried section were larger than those in the entrance section, and the fractured morphology mainly comprised sheet and monolithic block, corresponding to transgranular fracture and intergranular fracture. Rocks with few types of mineral cementation, good crystallization and small particle size differences had better energy storage and release characteristics. There was little difference in the rockburst tendency of rocks with different buried depths, but there were obvious differences in the rockburst grade. In the deep-buried section of the tunnel, the rockburst grade was of a moderate–heavy level and the rockburst risk at the vault and right spandrel of the cross section was more severe, which was basically consistent with the situation at the tunnel site. This study can provide a theoretical basis for the prevention and control of rockbursts in Wulaofeng tunnel and other similar engineering projects.

Effect of Loading Rates on Mechanical Characteristics and Rock Burst Tendency of Coal-Rock Combined Samples

According to the universal law of thermodynamics, the failure of any substance is closely related to its energy change. Understanding the strain energy and rock burst tendency of rock or coal under different loading rates is critical in many geological projects, such as mining, tunneling, and other underground engineering project. The mechanical and energy evolution characteristics of the coal-rock combined sample under different loading rates of uniaxial compression were numerically investigated. And, the rock burst tendency was also calculated by the Rock Burst Energy Index KE. The results show that with the increase of the loading rate, the total input energy, elastic strain energy, and dissipation energy all show an increasing trend. But the growth trend is different. And, under the five loading rates, the Rock Burst Energy Index KE of the coal-rock combined sample were all between 1.5 ≤ KE < 5. That is, they all have weak rock burst tendency. And the rock burst energy index increases first and then decreases with the increase of loading rates. This study provides references for propulsion speed of working face in the field mining practice.

Experimental and numerical study on fracture characteristics and constitutive model of sandstone under freeze-thaw-fatigue

The present paper proposes a whole-process constitutive model of rock mass under freeze-thaw-fatigue based on the Drucker-Prager criterion and the Lemaitre strain equivalence hypothesis and by using a Weibull distribution. The fracture characteristics of rock mass under freeze-thaw-fatigue are studied from a macro and mesoscopic perspective, by using the discrete element method and acoustic emission technology. The results show that as the number of freeze-thaw treatments increases, the b value fluctuation amplitude of the rock mass at fatigue failure decreases, the shear crack increases, the anisotropy of the mesoscopic force field enhances, and the required energy decreases, and the rock burst tendency weakens.

Investigation of Rock Burst Mechanism under Thermomechanical Coupling Conditions Based on Rock Mechanical Tests

Abstract The thermomechanical (TM) coupling effects of rock bursts have attracted considerable attention from researchers owing to the high geothermal and geostresses in deep tunnels in regions such as Western China. To study the brittleness and rock burst mechanism under TM conditions, various tests, such as splitting, uniaxial compression, rock burst tendency, and rock burst physical model tests, were conducted at temperatures ranging from 20°C to 80°C. The results revealed that, when granite samples were heated, their tensile strengths decreased in the splitting tests. Their peak stresses and the corresponding strains increased; their macroscopic tensile fracture surfaces became more evident; and the microcosmic tensile properties of intergranular fractures became prominent under uniaxial compression. Rock burst physical model tests and acoustic emission monitoring results revealed that, at higher temperatures, the fracture degree and failure range were larger, the energy was higher and more concentrated during failure, and failure occurred earlier. The brittleness index B, rock burst tendency Wet, and σθ/σc all exhibited a clear increasing tendency with an increase in temperature. The rock burst mechanism, considering the temperature effect, can be summarized as follows: the increase in brittle tensile fracture components and geostress caused by temperature increasing is conducive to the rapid release of energy, which will promote the occurrence of rock burst. The researching result is of great academic value and practical significance for the prevention, design, and safe construction of rock burst in deep high geothermal tunnels.

Research on Rock Burst Control Mechanism of Deep Buried Tunnel Using Surrounding Rock Modification Theory

In order to solve the rock burst disaster during the excavation of deep buried high stress hard rock tunnel, the method of changing the properties of surrounding rock by blasting is proposed in this paper. This method can effectively change the physical and mechanical properties of surrounding rock, reduce the storage capacity of surrounding rock corresponding to variable energy, and transfer the stress concentration position to the deep layer, which is an effective means to control rock burst. Taking the tunnel with rockburst tendency as an example, the stress distribution characteristics and displacement changes of surrounding rock under different modification depths are studied by using the numerical calculation method and elastic-plastic mechanics theory, and the effect is tested combined with microseismic data. The results show that the thickness of tunnel blasting loosening is closely related to the stress concentration of surrounding rock, and blasting loosening can effectively inhibit the occurrence and prevention of rock burst. With the increase of blasting depth, the maximum stress concentration decreases. The relevant research results can be used to reasonably design the blasting and loose surrounding rock reconstruction of high stress rock burst tunnel and improve the theoretical and practical basis.