Search Results (30)

The Qinghai–Xizang Plateau and its surrounding regions have experienced intense tectonic activity, resulting in complex geostress environments that cause frequent and distinctive rockburst disasters in plateau tunnel engineering. In this study, numerical simulations were conducted to investigate the distribution characteristics and patterns of tunnel rockbursts in high-altitude regions, using geostress orientation, lateral pressure coefficient, and tunnel depth as the primary independent variables. Secondary development of FLAC3D 7.00.126 was carried out using FISH language to enable the recording and visualization of tangential stress, the Russense rockburst criterion, and elastic strain energy. Based on this, the influence mechanisms of these key geostress parameters on the location, extent, and intensity of rockbursts within tunnel cross sections were analyzed. Results indicate that geostress orientation predominantly affects the location of rockbursts, with the surrounding rock in the direction of the minimum principal stress on the tunnel cross section being particularly prone to rockburst risks. The lateral pressure coefficient primarily influences the rockburst intensity and pit range within local stress concentration zones, with higher values leading to greater rockburst intensity. Notably, when structural stress is sufficiently large, rockbursts may occur even in tunnels with shallow burial depths. Tunnel depth determines the magnitude of geostress, mainly affecting the overall risk and potential extent of rockbursts within the cross section, with greater depths leading to higher rockburst intensities and a wider affected area. Full article

The instability of mine roadways is significantly influenced by the coupled effects of groundwater seepage and non-uniform loading. These interactions often induce localized plastic deformation and progressive failure, particularly in the roof and sidewall regions. Seepage elevates pore water pressure and deteriorates the mechanical properties of the rock mass, while non-uniform loading leads to stress concentration. The combined effect facilitates the propagation of microcracks and the formation of shear zones, ultimately resulting in localized instability. This initial damage disrupts the mechanical equilibrium and can evolve into severe geohazards, including roof collapse, water inrush, and rockburst. Therefore, understanding the damage and failure mechanisms of mine roadways at the mesoscale, under the combined influence of stress heterogeneity and hydraulic weakening, is of critical importance based on laboratory experiments and numerical simulations. However, the large scale of in situ roadway structures imposes significant constraints on full-scale physical modeling due to limitations in laboratory space and loading capacity. To address these challenges, a straight-wall circular arch roadway was adopted as the geometric prototype, with a total height of 4 m (2 m for the straight wall and 2 m for the arch), a base width of 4 m, and an arch radius of 2 m. Scaled physical models were fabricated based on geometric similarity principles, using defect-bearing sandstone specimens with dimensions of 100 mm × 30 mm × 100 mm (length × width × height) and pore-type defects measuring 40 mm × 20 mm × 20 mm (base × wall height × arch radius), to replicate the stress distribution and deformation behavior of the prototype. Uniaxial compression tests on water-saturated sandstone specimens were performed using a TAW-2000 electro-hydraulic servo testing system. The failure process was continuously monitored through acoustic emission (AE) techniques and static strain acquisition systems. Concurrently, FLAC^3D 6.0 numerical simulations were employed to analyze the evolution of internal stress fields and the spatial distribution of plastic zones in saturated sandstone containing pore defects. Experimental results indicate that under non-uniform loading, the stress–strain curves of saturated sandstone with pore-type defects typically exhibit four distinct deformation stages. The extent of crack initiation, propagation, and coalescence is strongly correlated with the magnitude and heterogeneity of localized stress concentrations. AE parameters, including ringing counts and peak frequencies, reveal pronounced spatial partitioning. The internal stress field exhibits an overall banded pattern, with localized variations induced by stress anisotropy. Numerical simulation results further show that shear failure zones tend to cluster regionally, while tensile failure zones are more evenly distributed. Additionally, the stress field configuration at the specimen crown significantly influences the dispersion characteristics of the stress–strain response. These findings offer valuable theoretical insights and practical guidance for surrounding rock control, early warning systems, and reinforcement strategies in water-infiltrated mine roadways subjected to non-uniform loading conditions. Full article

Granite is widely used in laboratory rockburst simulations due to its exceptional strength, brittleness, and uniform composition. This study employs a true triaxial loading system to replicate asymmetric stress states near free surfaces, allowing precise control of three-dimensional stresses to simulate strain-mode rockbursts. Advanced monitoring tools, such as acoustic emission (AE) and high-speed imaging, were used to investigate the evolution process, failure mechanisms, and monitoring strategies. The evolution of strain-mode rockbursts is divided into five stages: stress accumulation, crack initiation, critical instability, rockburst occurrence, and residual stress adjustment. Each stage exhibits dynamic responses and progressive energy release. Failure is governed by a tension–shear coexistence mechanism, where vertical splitting and diagonal shear fractures near free surfaces lead to V-shaped craters and violent rock fragment ejection. This reflects the brittle nature of granite under high-stress conditions. The AE monitoring proved highly effective in identifying rockburst precursors, with key indicators including quiet periods of low AE activity and sudden surges in AE counts, coupled with ‘V-shaped’ b-value troughs, offering reliable early warning signals. These findings provide critical insights into strain-mode rockburst dynamics, highlighting the transition from elastic deformation to dynamic failure and the role of energy release mechanisms. Full article

In terms of rockburst control technology, it is generally believed that optimizing the section design and adopting the step method can effectively suppress the occurrence of rockburst, but there is no literature to explain the reasons for adopting this method from the experimental point of view. In addition, compared with the application of support, this method can achieve the effect of not increasing the construction process, not affecting the progress of the project and reducing the project cost. In view of this, the Gaoloushan deep-buried tunnel with rockburst was taken as the research object in this paper. Firstly, the excavation scheme based on the step method was proposed, and its explosion-proof effect was verified again. The experimental results showed that the step method could be essentially regarded as the transformation of surrounding rock by reasonably distributing explosives and reducing the working section. The beneficial effects of this method were as follows: the release intensity of absolute energy was slowed down, the way of energy release was changed; the stress condition of surrounding rock was improved; the path of the continuous supplement of strain energy in the original rockburst area was cut off; and the energy accumulation degree of surrounding rock was reduced, so that the accumulated energy in the rock mass did not exceed its energy storage limit at the location where the rockburst should have occurred. The reduced high energy was released in an orderly manner and induced the rock failure process, forming a fracture zone and a plastic zone. In the process of expansion, the fracture zone and plastic zone further reduced the stress concentration of the surrounding rock and deteriorated the mechanical properties of the surrounding rock. The stress concentration zone was transferred to the deeper surrounding rock outside the unloading relaxation zone, and part of the elastic energy accumulated in the surrounding rock was released. The strain energy could be distributed and dissipated, and the effect of energy safety and slow release was achieved. Full article

Parallelepipeds specimens were made to further investigate the rockburst occurrence mechanism of ore pillars in underground mining units. The investigation was carried out with uniaxial compression systems and real-time testing systems, such as stress, video, and acoustic emission, combined with digital image correlation (DIC) and SEM electron microscope scanning technology, to systematically analyze the evolution of rockburst of ore pillars, strain field characteristics, acoustic emission characteristics, mesoscopic characteristics of the rockburst fracture, morphology of the bursting crater, and debris characteristics. The findings demonstrate that the pillar’s rockburst process went through four stages, including the calm period, the particle ejection period, the block spalling period, and the full collapse period. According to DIC digital image correlation technology, the development of cracks in the rock is not obvious during the calm period, but during the small particle ejection and block spalling periods, the microcracks started to form and expand more quickly and eventually reached the critical surface of the rock, resulting in the formation of a complete macro-rockburst rupture zone. During stage I of the test, the rate of acoustic emission events and energy was relatively low; from stages II to IV, the rate gradually increased; and in stage V, the rate of acoustic emission events and energy reached its maximum value at the precise moment the rock exploded, releasing all of its stored energy. The specimen pit section primarily exhibits shear damage and the fracture exhibits shear fracture morphology, while the ejecta body primarily exhibits tensile damage and the fracture exhibits tensile fracture morphology. The location of the explosion pit is distributed on the left and right sides of the middle pillar of the specimen, and the shape is a deep “V”. The majority of the rockburst debris is greater than 5 mm, and it mostly takes the shape of thin plates, which is comparable to the field rockburst debris’s shape features. Full article

The relationship between slabbing failure and rockburst has become a hot issue in rockburst research. In this paper, the experimental system of impact rockburst is used to conduct a simulation experiment of rockburst induced by slab failure on metamorphic sandstone samples taken from the deep-buried horseshoe-shaped tunnel in Gaoloushan, with “pan-shaped” rockburst pits on site and laboratory simulation experiments, which prove the rationality of the experimental results of rockburst. The quantitative analysis of the displacement field in the process of the slab buckling rockburst is carried out, which shows that the slab structure will undergo a long period of gestation before its formation, and the formation of the slab structure will accelerate the occurrence of rockburst. This type of rockburst has attenuation characteristics in the process of rockburst; in addition, the phenomenon of “slab buckling circle” is found. The generation of the “slab buckling circle” and the formation of slab buckling cracks are inconsistent, which is a time-lagged fracture in engineering. The relationship between the rupture parameters of rockburst disaster rock mass and time shows a compound exponential growth relationship, revealing that the mechanism of the slab buckling rockburst can be regarded as the result of the combined action of shear crack and tension crack, which plays a leading role, reflecting the characteristic of progressive fracture development. It is a typical progressive fracture-induced instability rockburst model, which is a strain-lag rockburst. Full article

The use of tunnel boring machines (TBMs) in deep hard rock tunnels disrupts the original stress equilibrium of the rock mass, often resulting in the aggregation and release of a large amount of elastic strain energy, and even leading to rockburst. Under extremely high rockburst proneness conditions, advance stress release boreholes (ASRBs) deployed behind the TBM cutter head can be used to reduce stress concentration levels. However, there is a lack of scientific design methods for the parameters of the ASRB program for TBM tunnels, leading to poor stress release and difficulty in mitigating high-intensity rockburst hazards. This study proposes a parameter design method for ASRBs in the potential rockburst seismic source area of deeply buried hard rock TBM tunnels, including test scheme establishment methods, parameter selection methods, and parameter space relationship and evaluation index establishment methods. A deep tunnel in southwest China was used as an engineering case study to explore the effect of stress release and energy dissipation under different ASRB layout schemes. The results show that the sensitivity of the five important design parameters of ASRBs to the stress release effect is, in descending order, “aperture”, “inclination”, “included angle”, “spacing”, and “length”. A parameter control law for ASRBs is proposed, which confirms their effectiveness in preventing, controlling, and reducing rockburst disasters in deep hard rock TBM tunnels. Full article

Strain rockburst is a severe failure phenomenon caused by the release of elastic strain energy in intact rocks under high-stress conditions. They frequently occur in deep tunnels, causing significant economic losses, casualties, and construction delays. Understanding the factors influencing this disaster is of significance for tunnel construction. This paper first proposes a novel three-dimensional (3D) discrete element numerical analysis method for rockburst numerical analysis considering the full stress state energy based on the bonded block model and the mechanics, brittleness, integrity, and energy storage of the surrounding rock. This numerical method is first validated via laboratory tests and engineering-scale applications and then is applied to study the effects of compressive and tensile strengths of rock mass, tunnel depth, and lateral pressure coefficient on strain rockburst. Meanwhile, sensitivity analyses of these influencing factors are conducted using numerical results and systematic analysis methods, and the influence degree of each factor on the rockburst tendency is explored and ranked. The results reveal that laboratory tests and actual engineering conditions are consistent with numerical simulation results, which validates the rationality and applicability of the novel rockburst analysis method proposed in this paper. With the increase in compressive strength, the stress concentration degree, energy accumulation level, maximum stress difference, and maximum elastic strain energy within the rock mass all increase, leading to a stronger rockburst tendency. Tunnel depth and the lateral stress coefficient are positively correlated with rockburst tendency. As the lateral pressure coefficient and tunnel depth increase, rockburst tendency exponentially increases, while the maximum stress difference and maximum elastic strain energy within the rock mass also increase. The influence degree of each factor is ranked from highest to lowest as follows: tensile strength, lateral pressure coefficient, compressive strength, and tunnel depth. The research results provide theoretical support and technical guidance for the effective prediction, prevention, and control of rock burst disasters in deep tunnels. Full article

Rockburst is an extremely hazardous geological disaster. In order to accurately predict the hazardous degree of rockbursts, this paper proposes eight new classification models for predicting the intensity level of rockbursts based on intelligent optimisation algorithms and deep learning techniques and collects 287 sets of real rockburst data to form a sample database, in which six quantitative indicators are selected as feature parameters. In order to validate the effectiveness of the constructed eight machine learning prediction models, the study selected Accuracy, Precision, Recall and F1 Score to evaluate the prediction performance of each model. The results show that the NGO-CNN-BiGRU-Attention model has the best prediction performance, with an accuracy of 0.98. Subsequently, engineering validation of the model is carried out using eight sets of real rockburst data from Daxiangling Tunnel, and the results show that the model has a strong generalisation ability and can satisfy the relevant engineering applications. In addition, this paper also uses SHAP technology to quantify the impact of different factors on the rockburst intensity level and found that the elastic strain energy index and stress ratio have the greatest impact on the rockburst intensity level. Full article

Rockbursts represent one of the most serious and severe natural hazards emerging in underground copper mines within the Legnica–Glogow Copper District (LGCD) in Poland. The contributing factor determining the scale of this event is mining-induced seismicity of the rock strata. Extensive expertise of the copper mining practitioners clearly indicates that high-energy tremors are the consequence of tectonic disturbances or can be attributed to stress/strain behaviour within the burst-prone roof strata. Apparently, seismic activity is a triggering factor; hence, attempts are made by mine operators to mitigate and control that risk. Underlying the effective rockburst control strategy is a reliable seismicity forecast, taking into account the causes of the registered phenomena. The paper summarises the geomechanics analyses aimed to verify the actual seismic and rockburst hazard levels in one of the panels within the copper mine Rudna (LGCD). Two traverses were designated at the face range and comparative analyses were conducted to establish correlations between the locations of epicentres of registered tremors and anomaly zones obtained via analytical modelling of changes in stress/strain behaviours within the rock strata. The main objective of this study was to evaluate the likelihood of activating carbonate/anhydrite layers within the main roof over the excavation being mined, with an aim to verify the potential causes and conditions which might have triggered the registered high-energy events. Special attention is given to two seismic events giving rise to rockbursts in mine workings. Results seem to confirm the adequacy and effectiveness of solutions provided by mechanics of deformable bodies in the context of forecasting the scale and risk of dynamic phenomena and selecting the appropriate mitigation and control measures in copper mines employing the room-and-pillar mining system. Full article

Solving the challenges facing the mining industry is crucial for shaping the global attitude towards clean energy technologies associated with critical minerals extracted from depth. One of these challenges is the well-known explosion-like fractures (rockbursts) or spalling failures associated with the initiation of internal cracks. To prevent such catastrophic failure, shotcrete, as a cement grout, is widely used in tunnel support applications. In areas where the tunnels are constructed within the limestone strata using tunnel boring machines (TBM), drilling, and/or blasting, millions of cubic meters of crushed limestone (CL) in powder form are extracted and landfilled as waste. Given the fact that natural sand consumption as a raw material in the construction industry exceeds previous records, recycling of such excavation material is now becoming increasingly needed. From this perspective, this study aims to utilize crushed limestone as a potentially sustainable alternative to natural sand in shotcrete applications in deep tunnels. Accordingly, several strength characterization and crack initiation determinations through various stress–strain-based models were carried out on cylindrical samples containing different proportions of crushed limestone. By increasing the crushed limestone content in the shotcrete mix, the crack initiation stress (as a measure of the in situ spalling strength) increased as well. The results suggest that the crushed limestone has good potential to replace the natural sand in the shotcrete mixture used in tunnel support applications. Full article

Rigid structural planes encountered during construction have an obvious influence on rockburst intensity and occurrence mechanism. The high-intensity rockburst induced by the structural plane poses a great threat to the safety construction of the tunnel. A novel 3D discrete element numerical analysis method for rockburst is proposed with the help of the bonded block model and multi-parameter rockburst energy index. According to this method, the influence of multivariate information characteristics such as stress, energy, fracture, and rockburst proneness index on the surrounding rock during the strain-structural plane slip rockburst in deep tunnels is systematically investigated. The results are drawn as follows: The results show that from the analysis of multivariate information characteristics of strain-structural plane slip rockburst, the rock between the plane and tunnel is a typical rockburst risk area. The dip angle, length, and relative distance of the structural plane have a significant influence on the multivariate catastrophe information characteristics of the surrounding rock: As the dip angle increases, the fracture propagation range within the risk rock expands, but the rockburst intensity and the occurrence range gradually decrease; as the length increases, the fracture propagation range, rockburst intensity and occurrence range within the risk rock increase slightly; as the relative distance increases, the fracture propagation range and rockburst intensity gradually weaken, and the occurrence range of rockburst first increases and then decreases. Using the “11.28” strain-structural plane slip rockburst case as a basis, engineering validation research was conducted. The simulation results are found to be essentially consistent with the rockburst condition on the field, validating the rationality and applicability of the novel rockburst analysis method proposed in this paper. Full article

This study aims at the problems of the difficulty in controlling the stability of the surrounding rock and the high-impact danger of knife handle-type working face mining. We take the I010206 working face of Kuangou Coal Mine in Xinjiang as the engineering background, establish the mechanical model of roof periodic fracture and the FLAC^3D numerical model of a working face, and analyze the evolution characteristics of the surrounding rock stress and energy when the working face is widened, revealing the mechanism of induced impact caused by overburden fracture in the working face, putting forward the technology of hydraulic fracturing to relieve the danger in the roof area, and comparing the pressure relief effect. The research results show the following: (1) After the working face is widened, the overlying strata load is transferred to the coal seam in front of the working face and the upper and lower sides of the working face. after mining; the abutment pressure of the I010408 working face in the B4-1 coal seam is superimposed with the abutment pressure of the I010206 working face in the B2 coal seam, the stress concentration is higher, and the lateral support pressure of the goaf forms a high static load. The large-area roof caving forms a high dynamic load. All of them are more likely to induce rockburst. (2) In knife handle-type working face mining, the peak value of the advanced abutment pressure in working faces first decreases and then increases, and the advanced abutment pressure increases from 10.31 MPa to 14.62 MPa; the peak value and concentration degree of strain energy density increase with the increase in working face width. (3) Measures were proposed to weaken the hydraulic fracturing roof in advance. After using hydraulic fracturing technology, the pressure step distance of the working surface roof was reduced, and the microseismic energy frequency was significantly reduced. These measures reduced the impact risk of the working face and ensured the safe mining of the working face. Full article

The application of load on rock materials stimulates a weak current known as Pressure Stimulated Current (PSC). This study focuses on investigating the damage evolution of granite rocks through the analysis of PSC responses. Uniaxial loading experiments were conducted on granite samples, and the accompanying PSC was measured in real-time. The relationship between PSC characteristics and mechanical behaviors of granite was examined to explore precursory information related to granite failure. The damage evolution of granite was assessed using a damage variable defined as the cumulative charge (time integral of PSC). The results clearly demonstrate a close correlation between the variation of PSC and the mechanical behaviors of rock. Specifically, during the compaction and elastic deformation stages, PSC exhibits a slow and linear increase. However, once deformation enters the plastic stage, PSC demonstrates an accelerated upward trend. Additionally, it was observed that a stress drop coincides with an abnormal increase in PSC, which is followed by a rapid decay. The fluctuation observed after the abnormal increase in PSC during the accelerated growth phase can serve as a precursor of rock failure. Furthermore, the cumulative charge quantity effectively correlates with the damage process of granite samples. The stress–strain curve obtained from a theoretical constitutive model, established based on the damage variable represented by normalized cumulative charge, aligns reasonably well with the experimental results, affirming that the defined damage variable accurately reflects the damage evolution process of rocks. It is hypothesized that PSCs are carried by electrons within the rocks, which are stimulated by electron diffusion during deformation and experience a sharp increase upon rock fracturing. The research findings hold theoretical significance for predicting rockburst incidents using the PSC method. Full article

Strain burst hazard is one of the main challenges that faces deep underground environments. To manage it, it is needed to assess its probability occurrence (or potential). Various methods have been proposed over the years to assess the phenomenon early on. However, due to uncertainties in rock mass properties and the physical processes of the phenomenon, mitigation measures are an additional important line of defense to ensure workplace safety. While work has been carried out to assess the rockburst hazard better and improve support systems, the effect of mitigation measures on strain burst hazard potential is unclear. This paper studies the influence of the implementation of shotcrete and rockbolts support and destress blasting in tunnels on strain burst potential, based on two-dimensional numerical models of circular tunnels. The results highlight that, as expected, the use of mitigation measures allows the strain burst occurrence to decrease. However, the strain burst hazard level does not decrease easily, even when using mitigation measures. In the case of serious overbreak hazards, only a combination of system support and destress blasting seems to have an impact on these events, and not for all the simulated cases. Full article