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

Abstract

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.

1. Introduction

As surface mineral resources are increasingly depleted, deep mining has become a standard practice [1,2,3]. However, the challenging conditions of deep rock mining, characterized by “three high and one disturbance” (high pressure, high temperature, high stress, and disturbance), pose significant obstacles to the safe and efficient extraction of deep resources. Rockburst, in particular, is a major disaster in deep mining [4,5,6]. It occurs when rock masses fracture suddenly due to high in situ stress conditions, releasing substantial amounts of energy that threaten both construction equipment and personnel safety [7,8,9]. The likelihood of rockbursts is influenced by a range of factors, including in situ stress, rock lithology, structural features of the rock mass, burial depth, geological formations, hydrogeological conditions, and excavation and blasting methods [10,11,12]. The intricate interactions among these factors make understanding and controlling rockbursts a crucial challenge in deep mining [13,14,15].

Currently, researchers both domestically and internationally have carried out extensive studies on rockbursts [16,17,18,19,20]. Niu et al. [16] analyzed geological information and rockburst occurrence times collected from various drilling and blasting programs in deep tunnels. They established a link between the timing characteristics of rockbursts and microseismic (MS) sequences, utilizing the mechanisms behind MS sequences to explain possible rockburst types and their timing, influenced by geological conditions as well as drilling and blasting practices. Their findings revealed that rockbursts could happen at any stage of the blasting cycle, with the highest frequency occurring during hazard elimination and support phases, and the lowest frequency during drilling and loading phases. Peng et al. [1] carried out simulation tests of slab cracking damage in different arch structures and found that 1/4 three-centered arches were safer and more economical than 1/3 three-centered arches and semicircular arches. Martin et al. [17] carried out a series of uniaxial compression tests on columnar granite specimens containing circular apertures (apertures with radii ranging from 20 to 103 mm) to study the effect of aperture dimensions on the damage to the wall and pointed out that the field tunnel apertures were not affected by scale effects. wall slab cracking is not affected by scale effects. Liu et al. [18] conducted two types of rockburst experiments—strain burst and impact-induced rockburst—using a strain burst device equipped with an acoustic emission (AE) monitoring system and an impact-induced rockburst setup, under varying initial geological stresses. The findings revealed that the rockburst process was consistent across different initial stresses, with the intensity of rockbursts increasing as the initial in situ stress rose. Si et al. [11] investigated circular tunnels’ damage process and evolution mechanism under complex stress paths, including in situ stress, excavation unloading, and stress redistribution. The results revealed that, within a certain range of in situ stress, the support of surrounding rock plays a more significant role in reducing damage risk and severity compared to unloading methods in deep underground projects. C.D. Martin et al. [19] found that at moderate depths, the stress damage zone only appears in a localized area around the tunnel, whereas at greater depths, the stress damage zone will extend along the entire tunnel excavation boundary. A. Mazaira et al. [20] showed that with increasing depths, the stress-induced damage can be transformed from a surface spalling to an intense rockburst. Si et al. [21,22] investigated the rockburst characteristics of basalt and granite, identifying the influence mechanisms of liner angle and unloading rate using uniaxial compression and triaxial unloading compression tests. Peng et al. [23] conducted a true triaxial rock explosion simulation test and found that with the increase in axial stress, the surrounding rock damage intensity increases, but the initial damage vertical stress increases first (10~50 MPa) and then decreases (50~80 MPa).

However, in the process of deep well mining, the action of water on rock can be seen everywhere, and the rockburst phenomenon occurs from time to time, so the mechanism of the effect of water on rockburst becomes a hot topic, and a large number of scholars have begun to carry out research in this area. Luo et al. [24] used a true triaxial rockburst test system to carry out rockburst tests on red coarse-grained granite with different water content and analyzed the rockburst after rockburst with different water saturation levels The characteristics of strength and deformation, damage, and ejection process, damage mode and acoustic emission (AE) of rock specimens with different water saturations were analyzed. Discussed the relationship between water content and kinetic energy of rock explosion ejection and the impact of water on the rock explosion mechanism. Chen et al. [25] analyzed the rock explosion effect of different water content of red sandstone, combined with a high-speed camera monitoring the whole rock fall and analyzed the ejection form of rock explosion. Liu et al. [26] studied the effect of water content on the rock explosion phenomenon of tunnels with horizontal joints, and through the scanning electron microscope (SEM) and particle size analyzer to analyze the effect of rock explosion on the rock explosion phenomenon. SEM) and particle size analyzer to analyze the microstructure of rockburst debris. Luo et al. [27] analyzed the effect of water on rockburst propensity from the perspective of energy storage and conducted uniaxial compression tests on saturated, natural, and oven-dried red sandstone specimens to evaluate the rockburst susceptibility to propensity by using a combination of strain-energy calculations and experimental observations. Luo [28] carried out a series of uniaxial and true triaxial compression tests on two round-hole red sandstone samples with different water content. A series of uniaxial and true triaxial compression tests were carried out to study the effect of water on the stress, energy, and fracture characteristics of rock damage in hard rock tunnels. Liu et al. [29] analyzed the effect of water on sandstone rockbursts and the mechanism of water on sandstone rockburst prevention and control from the perspective of energy and damage modes in order to study the mechanism of mitigating rockbursts by injecting water into the surrounding rock. Zhang et al. [30] discussed the uniaxial addition and removal of the effect of water on the brittleness and the rockburst susceptibility of granite by using a combination of strain energy calculations and experimental observations. Li et al. [31] monitored an early warning of rockburst by means of electromagnetic radiation (EMR) and monitored the EMR signal of sandstone samples with different water content under uniaxial compression, and the results showed that with the increase in water content, the EMR signal and mechanical strength of sandstone are weakened. Wang et al. [32] conducted a study of sandstone samples with different water content. A series of triaxial unloading compression tests as well as acoustic emission monitoring were carried out on sandstone specimens with different water contents. The mechanical properties, damage characteristics, and swelling behavior of the sandstone specimens were compared appropriately. Huang et al. [33] investigated the effect of water content on the mechanical properties and the evolution of crack extension of sandstone by means of indoor compression tests and numerical simulation of the engineering discrete element method (EDEM) for sandstone under different conditions. Feng et al. [34] used a true triaxial test system of unloaded minimum principal stress to investigate the mechanical strength of sandstone specimens subjected to various water contents and intermediate principal stresses. The crack extension behavior of red sandstone affected by various water contents and intermediate principal stresses was investigated by Lu et al. [35], who investigated the mechanical properties and energy dissipation characteristics of sandstone with different water contents under dynamic loading by means of the split Hopkinson press bar (SHPB) test. Zhou et al. [3] conducted a series of uniaxial compression tests on sandstone samples with different water contents. The effect of water content on the energy evolution characteristics during the loading process was analyzed, revealing the fundamental mechanism of rock explosion inhibition by water injection in rocks. Additionally, studies have indicated that rockbursts are less likely to occur in underground engineering within rock masses that have high moisture content [28,36]. Fowkes et al. [37] observed that the presence of water and slurry in tunnels significantly decreases the probability of rockburst occurrences. Ortlepp et al. [38] studied rockburst incidents across different hard rock mines and discovered that rockbursts occurred less frequently in rock masses with higher moisture content. This is because in deep underground environments, rock masses are exposed to high geological stress and complex groundwater conditions [39,40]. Therefore, to better understand the mechanisms of strain rockbursts under the influence of moisture, considering the impact of water on strain-induced rockbursts is crucial.

In this paper, the recent progress in understanding the mechanism of water influence on rock burst occurrence at home and abroad is made from several aspects, such as the mechanism of water influence on rock burst occurrence, the study of rock burst tendency under different water content conditions, the weakening effect of water on hard rock and the evolution law of microcracks in rock, the mechanical properties of rock under wet and dry conditions, and rock burst prevention considering the water effect. In this paper, the typical engineering examples are introduced, and the next research work is introduced and prospected.

2. The Mechanisms through Which Water Impacts the Physical and Mechanical Properties of Rocks

Typically, the presence of water reduces the strength and elastic brittleness of rocks, making them more susceptible to damage and affecting their physical properties [41,42,43]. Shen et al. [44] studied the stress–strain response and electromagnetic radiation (EMR) signal characteristics of water-saturated sandstone under uniaxial cyclic loading and unloading conditions. Their results showed that dry sandstone exhibited significantly higher peak stress than water-saturated samples under cyclic loading and unloading. With increasing water content, the rock’s strength, load-bearing capacity, and fatigue life all decreased. Luo et al. [45] performed true triaxial tests on a sample of naturally saturated red sandstone cubes containing pore space. They found that in high-stress environments, the presence of water led to a deterioration in tunnel stability, resulting in large-scale, severe stress-induced damage. Huang et al. [46] combined the benefits of water pressure blasting and hydraulic fracturing. Hydraulic-controlled blasting is performed first, followed by the use of hydraulic fracturing to alter the structure of coal and rock blocks. Experiments have demonstrated the effectiveness of this method.

Additionally, the chemical reactions between water and rocks are crucial factors affecting rock stability and failure modes [47,48]. For instance, in rocks containing soluble salts, the infiltration of water molecules can react with these salts to form new substances, altering the rock’s chemical composition [47]. This phenomenon is particularly pronounced in salt rock regions and has a substantial impact on rock stability and engineering safety. Many researchers have explained this impact from a microscopic perspective, finding that the primary cause is chemical corrosion, which reduces the cohesion of the rock [47,48,49,50].

The impact of water on rock stability and failure modes is a complex process influenced by multiple factors. The strength of rocks can vary greatly under different conditions of water action, as can the pattern of damage [51,52,53]. For example, Luo [39] carried out several true triaxial compression tests on sandstone specimens with varying levels of water moisture to examine the effect of water on the mechanical properties of hard rocks. Cai et al. [54] examined how water affects the dynamic behavior and failure characteristics of sandstone through experiments simulating geological stress conditions. The study found that water content significantly affects dynamic properties such as sandstone’s dynamic strength, wave velocity, and energy absorption capacity. Additionally, under high permeability pressure conditions, damage patterns and properties of sandstones change with varying water content. Chen et al. [55] studied how water weakens sandstone and affects the development of microcracks using triaxial compression tests. Their results revealed that higher water content decreases rock brittleness and increases plastic deformation. Moreover, water content significantly affects the dynamic strength, stiffness, and toughness of sandstone, altering its fracture patterns and damage mechanisms [54,55,56].

The content of moisture significantly affects the mechanical behavior of rocks around tunnels or underground chambers. [57,58]. Therefore, a comprehensive understanding of how water affects rock strength and failure modes is essential for rock engineering projects, both in terms of stability analysis and design. [59,60]. In practical engineering, it is essential to account for the effects of water and implement appropriate measures to maintain project stability and security.

3. Research Progress on Water’s Impact in Strain-Induced Rockburst Experiments

3.1. Study of Strain-Induced Rockburst Tendencies under Different Moisture Contents

To explore how water affects the mechanical characteristics of rocks, Luo [39] carried out uniaxial and true triaxial compression experiments on natural water content (NWC) red sandstone samples, as did saturated water content (SWC) samples. They monitored and recorded the tunnel sidewalls in real time from intact to damaged. These results and data were synthesized to clarify the physico-mechanical how water affects the surrounding hard rock.

First, they selected three cylindrical samples and measured their mass (m₁) with natural water content (NWC) using an electronic scale. The dry mass (m₂) of the samples was then obtained by drying the samples in an oven, at 105 °C for 1 day to eliminate the moisture within the samples and then weigh them. Subsequently, they soaked the dried specimens with water for 2 days to reach saturated water content (SWC) conditions and were weighed for SWC mass (m₃). The test is carried out on the sample for uniaxial compression. Figure 1a shows the stress–strain curves from these tests. “The stress-axial strain curves for the NWC samples” exhibited considerable variability, whereas the SWC samples displayed much more uniform curves. This suggests that red sandstone becomes more homogeneous under SWC conditions, with less noticeable changes in physical properties. Compared to uniaxial compression results, “the strength and modulus of elasticity” of sandstone decreased under SWC conditions, specifically by 11.2 MPa (11.5% reduction) and 0.8 GPa (4.3% reduction), respectively. This indicates that water presence diminishes both the strength and modulus of elasticity of red sandstone, with strength reductions being more pronounced [61].

Figure 2 illustrates the damage pattern of the sample in the uniaxial compression test. For both moisture content conditions, the rocks are mainly damaged by shear. Samples D₃ and W₂ showed shear failure along single shear planes, while other samples exhibited shear failure along conjugate shear planes forming an ‘X’ shape. During the tests, the three NWC cylindrical samples experienced a sudden and rapid stress drop upon reaching peak stress. In contrast, the SWC samples did not show a sudden stress drop at peak stress (Figure 1b). Around the peak stress of the stress–strain curves, there were noticeable fluctuations, but the degree of failure was less severe in the SWC samples compared to the NWC samples. This indicates that, under the NWC condition, red sandstone experienced more severe failure and demonstrated a greater propensity for rockbursts compared to red sandstone in the SWC condition.

Next, the researchers performed true triaxial tests on the samples, The loading stresses were recorded and plotted as shown in Figure 3. The result reveals that, during the stepped loading phase, the variation in stress for SWC samples is notably less than that observed in NWC samples. Additionally, the initial stress and maximum vertical stress during the stepped loading phase are higher for SWC samples than for NWC samples. This suggests that the presence of water makes it initially more difficult for macroscopic damage to occur in tunnels. Nevertheless, once damage occurs in saturated hard rock tunnels, even small stresses can contribute to the appearance of significant damage. The researcher observed the damage observed on the side walls of the cube hole specimens prior to the unloading phase. Under triaxial stress conditions, all the holes experienced considerable flaking on the sidewalls that are at a right angle to the direction of the applied upright load. Upon comparing the extent of sidewall damage, it is evident that in the NWC cubic hole specimens, the damage zones along the hole axis were highly variable, with distinct areas of concentrated damage. Additionally, there were clear disparities in the damage on the two opposite sidewalls within the same sample. In contrast, “the sidewalls’ damaged zones of SWC cubic hole specimens” were characterized by a more consistent and evenly spread pattern along the hole’s axis. There was also less disparity in the damage between the two opposing sides of the same sample. During the tests, NWC cubic hole samples exhibited significant sidewall damage and rapid plate separation, indicative of rockbursts. In contrast, SWC cubic hole samples showed milder sidewall damage and minimal plate separation, indicating spalling. The comparison highlights clear differences in initial damage patterns based on moisture levels. Under SWC conditions, the rock’s brittleness around the hole decreased, leading to reduced damage severity, consistent with uniaxial compression test results.

From the above study, it was found that water affects hard rock materials and structures differently. For hard rock tunnels susceptible to rock bursts, applying water to the rock surface or injecting water into the surrounding rock can mitigate or even prevent the occurrence of rock bursts [62,63,64].

3.2. The Weakening Effect of Water on Hard Rock and the Evolution of Internal Microcracks in the Rock

Investigating how water reduces the strength of hard rock and influences the development of internal microcracks is a crucial area in rock mechanics research. Water infiltration leads to physical and chemical alterations in the rock, which impact its overall strength and stability [47,48,49,50]. Furthermore, water can facilitate the growth and progression of internal microcracks, thereby influencing the mechanical properties of the rock [55]. To study how water promotes rock bursting through the relationship between energy distribution and water content, Chen et al. [55] explored the mechanical properties of hard sandstone samples at various moisture levels and investigated how moisture affects their brittleness. By integrating acoustic emission analysis, they tracked the development of microcracks in hard sandstone and examined how water influences rock brittleness from an energy-based perspective.

Axial load tests conducted under varying restraining pressures and moisture levels revealed a significant impact of moisture on rock deformation as deviatoric stress increased. Higher moisture levels corresponded with reduced strain at peak stress, indicating a notable decrease in both the strength and stiffness of the rock. The data on Young’s modulus and peak strength further demonstrated that these values diminish as moisture content rises, with a Ks value closer to 1, reflecting a more pronounced weakening effect. Additionally, both lateral and volumetric strains after failure were reduced with increasing moisture. The triaxial compressive strength also declined with greater moisture content, underscoring the softening effect of moisture on sandstone.

As moisture content increases, peak strength indicators (σ_cc, σ_ci, σ_cd, and σ_f) decline, reflecting a decrease in the rock’s load-bearing capacity. In contrast, when moisture levels are held constant, these strength parameters rise with increasing confining pressure, as the pressure helps to prevent rock failure. Additionally, the accumulation of total energy slows as moisture content rises, a critical factor in using water to reduce rock bursts. The rate of elastic strain energy accumulation during the energy storage phase also decreases with higher moisture levels. The rock’s energy storage capacity, represented by residual elastic strain energy (RESE), shows a clear linear decline as moisture content increases. However, greater confining pressure enhances the rock’s ability to store energy.

The energy storage and release mechanism of rocks mainly involves the accumulation and dissipation of strain energy. Uniaxial compression tests show that rocks follow linear energy storage and dissipation laws during loading, i.e., the input strain energy, elastic strain energy, and dissipated strain energy are linearly related to the square of the stress at different unloading points. The energy storage potential includes relative and ultimate energy storage potentials, while the energy release potential reflects the extent of energy release when the rock reaches the damage threshold. The presence of water can seriously affect the microstructural integrity of rocks. Moisture weakens the microstructure of rocks, increases porosity, and reduces bond strength, thus reducing the strength and hardness of rocks. The deterioration of the microstructure directly affects the stress distribution within the rock mass, reducing its energy storage capacity and intensifying the dissipation process. Water-saturated rocks have a lower potential for energy release during damage, leading to faster damage and greater deformation, thus affecting the overall stability of the rock mass.

These observations highlight the complex interplay between water content, confining pressure, and the physical behavior of sandstones. The data show that an increase in moisture not only reduces peak strength and modulus of elasticity but also affects the energy storage capacity of the rock and its response to applied stresses. This understanding is crucial for predicting rock stability and damage mechanisms under various geological conditions. These insights can inform practical approaches to mitigating rockburst hazards in engineering applications, and future research should continue to explore these relationships and make full use of water to weaken rockburst hazards.

The experiment tracked acoustic emission energy and found that higher moisture content led to a significant increase in energy release before reaching peak stress. This reduction in acoustic emission intensity indicates a decline in brittle failure as moisture levels rise. Additionally, as moisture increases, the number of internal cracks at the point of failure decreases, suggesting reduced brittleness and a lower capacity for energy storage and strain energy release. This lowers the risk and severity of rock bursts, highlighting the effectiveness of water injection as a preventive measure in underground engineering.

Additionally, Chen et al. [49] examined the strength, deformation, and fracture properties of rock samples with varying moisture contents using uniaxial tests. They found that increasing moisture content led to reductions in rock strength and stiffness, while plastic deformation and fracture toughness increased. Additionally, Chen et al. observed that different hard rock types responded differently to the same moisture content, highlighting the need to understand these variations for geological engineering applications. Similarly, Cai et al. [49] investigated the dynamic properties of hard sandstone samples under geological stress with different moisture levels. Their study demonstrated that moisture significantly impacts the dynamic behavior and failure characteristics of hard sandstone. Increased moisture content resulted in decreased strength and stiffness of the sandstone, while plastic deformation and fracture toughness were enhanced. Cai et al. [54] also noted that hard sandstone types displayed distinct dynamic responses under identical geological stress conditions.

These findings are highly significant for understanding how moist hard rocks perform and are utilized in geological engineering scenarios. For example, when dealing with mining operations, tunnel excavation, and other similar engineering projects, it becomes crucial to evaluate how groundwater affects the mechanical properties and dynamic responses of hard sandstone. Understanding these impacts is essential for implementing effective measures to ensure safety and stability in engineering practices. Moreover, this research provides foundational data and theoretical insights that are valuable for related fields. It also offers a reference point for future investigations into the behavior and failure patterns of moist hard rocks when subjected to geological stress, contributing to a more comprehensive understanding of these materials.

3.3. Study on the Mechanical Properties of Sandstone under Wet–Dry Cyclic Conditions

Studying the mechanical properties of sandstone under wet–dry cyclic conditions is important because these conditions are commonly encountered in natural environments. Wet–dry cycles can induce stress and strain within sandstone, affecting its mechanical properties [65,66,67]. Common wet–dry cycle conditions include humid and arid climates, as well as variations in groundwater levels. In this field, scientists often use experimental techniques to evaluate the physical properties of sandstone, including dynamic elastic modulus, tensile strength, and compressive strength, under different wet–dry cyclic conditions. They also explore the rock’s fracture behavior and damage mechanisms [67,68,69]. Common experimental techniques include dynamic tensile tests, compression tests, and digital image correlation [70]. These studies are essential for grasping how wet–dry cycles affect the mechanical properties of geological materials in natural environments. They offer important insights that are beneficial for engineering design and applications in related fields.

Cai et al. [56] investigated through experiments and numerical simulations how wet–dry cycles lead to reductions in the strength, stiffness, and toughness of sandstone, as well as alterations in its fracture behavior and damage mechanisms. The study revealed that wet–dry cycles cause the expansion and contraction of pore water within the sandstone, resulting in changes in internal stress, which in turn leads to the propagation and aggregation of microcracks, ultimately forming macrocracks. Additionally, Cai et al. [56] investigated how wet–dry cycles influence the fracture behavior and damage mechanisms of various sandstone types. Zhou et al. [68,69] studied the effects of these cycles on the dynamic tensile and compressive properties of sandstone. Their findings revealed that repeated wet–dry cycles markedly decrease both dynamic tensile and compressive strengths, while also affecting deformation behavior. These results are crucial for understanding the stability of rock structures in natural and engineering settings. The three referenced studies collectively examine the mechanical properties of sandstone under wet and dry cyclic conditions [67,68,69]. These studies provide valuable references for further research in the field, though they differ slightly in focus and methodology. The following provides a detailed explanation:

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Similarities:

• All the studies concentrate on the mechanical properties of sandstone subjected to wet and dry cyclic conditions;
• All utilize experimental techniques to assess the dynamic tensile or compressive properties of sandstone;
• All findings indicate that wet and dry cycles have a significant impact on the mechanical properties of sandstone.

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Differences:

• Cai et al. [56] focus more on the fracture behavior and damage mechanisms of sandstone under wet and dry cyclic conditions, while the other two studies place greater emphasis on its dynamic tensile or compressive properties;
• Zhou et al. [68] primarily test the dynamic tensile properties of sandstone, whereas Zhou et al. [69] focus mainly on its dynamic compressive properties.
• The experimental methods used in the three studies differ slightly.

For example, Cai et al. [56] employed digital image correlation to investigate sandstone’s fracture behavior, while the other two studies used different testing equipment and methods. Zhou et al. [68] employed a dynamic tensile testing machine to evaluate the dynamic elastic modulus and tensile strength of sandstone under wet and dry cyclic conditions. This approach uses dynamic loads to replicate the stress conditions sandstone experiences in natural settings. In contrast, Zhou et al. [69] utilized a compression testing machine to measure the compressive strength, dynamic elastic modulus, and Poisson’s ratio of sandstone under similar cyclic conditions. This method applies either static or dynamic loads to mimic the stress conditions in natural environments. Both experimental techniques are standard in material mechanics testing and provide precise measurements of material properties.

Overall, these three studies examined the mechanical properties of sandstone under wet and dry cyclic conditions. They used experimental techniques to assess physical properties such as dynamic elastic modulus, tensile strength, and compressive strength, revealing that wet and dry cycles have a significant impact on these properties. Additionally, Cai et al. [56] specifically investigated how these cycles affect the fracture behavior and damage mechanisms of sandstone.

4. Consideration of Water’s Impact on Rockburst Prediction and Prevention

The impact of water on rock bursts is a complex issue. On the one hand, water can increase pore water pressure within the rock, thereby reducing its strength and stability, and increasing the risk of rock bursts. On the other hand, water can also slow the propagation of cracks by filling pores and reducing friction, thereby decreasing the risk of rock bursts. Therefore, when considering the impact of water on the development of rock bursts, it is essential to take into account multiple factors and analyze and assess the situation based on specific conditions [71,72,73].

4.1. Subsection

In certain situations, water may promote the occurrence of rock bursts. For example, in underground mining, an increase in groundwater levels can raise the pore water pressure within the mined-out area, potentially leading to collapses and rock burst incidents [74,75]. Conversely, water may also reduce or delay the occurrence of rock bursts. For instance, during natural disasters such as earthquakes, the differing reflection and refraction patterns of fluids and solid media during seismic wave propagation may affect the stress distribution and crack propagation within the rock, thereby reducing the risk of rock bursts.

Predicting rock bursts with accuracy remains a complex challenge, making the development of reliable and precise prediction models crucial. Several researchers have explored this issue. Zhang et al. [76] proposed a new hybrid model for rockburst strength prediction. Firstly, this study was conducted in a specific engineering environment using two parts of data constructed by TBM method for model training, validation, and improvement. In other application scenarios, such as rockburst warning for tunnels constructed by the drill-and-blast method or rockburst warning for tunnels under different stresses and rock conditions, further validation and improvement are needed. Secondly, due to the limitation of data completeness, this study only quantified information on previous rockburst events and excavation progress, excluding geological conditions other than microseismic parameters. Using more diverse and comprehensive information as inputs could improve the accuracy of the warning system. Long et al. [77] investigated an intelligent dynamic warning method for rockbursts. The prediction model combined rough set theory with a multidimensional cloud model to establish a hybrid prediction model for rockbursts. The accuracy of the model was validated using 18 rockburst cases in the test dataset, but since the dataset is limited, subsequent phases of the study will involve extending the dataset to cover a wider range of actual rockburst cases. To prevent and control rock bursts, key strategies include managing intrinsic factors and enhancing surrounding rock performance through high-pressure water spraying and microwave heating; addressing rock burst stress conditions with techniques like borehole pressure relief and pressure-relief blasting; and bolstering surrounding rock resistance using shotcrete, energy-absorbing bolts, and steel supports [78]. Wang et al. [32] and Liu et al. [29] confirmed that injecting water into surrounding rock effectively reduces rock burst intensity during tunnel excavation.

4.2. Consider the Prevention and Control of Water-Affected Rockbursts

In coal mining, preventing rock bursts is often closely tied to managing water conditions. Techniques such as large-diameter drilling and water injection are employed to alleviate high-stress concentrations, reduce the strength of the coal mass, and diminish the risk of rock bursts. Hydraulic cutting technology utilizes a high-pressure liquid to achieve the cutting of materials. The basic principle is that the liquid (usually water) is pressurized to an extremely high level by means of a hydraulic pump, and then the high-pressure liquid is ejected through a fine nozzle. This technique enables cutting to be carried out without generating high temperatures and therefore does not result in thermal deformation or hardening of the material. A common form of hydraulic cutting is high-pressure waterjet (HPWJ), while waterjet with added abrasives (AWJ) is suitable for harder materials.

When stress concentrations are not effectively managed, strong disturbance stress blasting may be utilized to address the issue [79,80]. Zhang et al. [81] proposed a strategy involving the arrangement of small panels and large coal pillars to facilitate pressure relief and prevent rock bursts. This method aims to strategically distribute stress and mitigate the conditions that lead to rock bursts. Chi et al. [82] demonstrated that hydraulic cutting is effective in reducing and redistributing stress concentrations within the coal seam. This approach also lessens the potential impact on the coal rock mass, thereby significantly lowering the probability of coal rock bursts. Large-diameter drilling technology is mainly used to excavate large-diameter holes in rock, soil, and other geological conditions, and is widely used in tunneling, foundation construction, and oil and gas drilling. This technology usually uses automated drilling equipment, which can efficiently complete the excavation of large-volume holes.

In conclusion, the impact of water on rock bursts is a complex issue that requires detailed analysis and assessment based on specific conditions. Future research should further explore the mechanisms by which water influences the development trends of rock bursts in various environments and propose corresponding prevention and control measures. For instance, in underground mining, reducing groundwater levels, strengthening support systems, and enhancing drainage can help mitigate the effects of water on rock bursts. In natural disaster scenarios, improving the seismic resilience of buildings and infrastructure, and planning urban and transportation systems more effectively, can reduce the occurrence of rock burst incidents. Specific measures are set out below:

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Hydraulic fracturing and pressure-relief water injection. Hydraulic fracturing creates fissures in the rock body by injecting high-pressure water, releasing stress, slowing down stress concentration, and reducing the risk of rock explosion. Bucking water injection makes the stress release smoother by reducing the initial stress in the rock body, which is suitable for high-risk areas with stress concentration.

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Rock softening and wet blasting. Water injection is used to soften the rock, reduce its strength and brittleness, thereby reducing the energy release during the rupture, to prevent rock burst. Wet blasting uses water to reduce the temperature and stress concentration during blasting, mitigating the risk of rock explosion generated during blasting.

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Groundwater drainage and water curtain spraying. A drainage system is used to control the accumulation of groundwater, reduce the water content of the rock mass, and improve its stability. Water curtain spraying by reducing the surface temperature of the rock body and friction in the fissure, effectively preventing the rock explosion caused by temperature changes, is suitable for high-temperature stress environments.

4.3. Integration of Water-Prevented Rockbursts

Water injection technology plays a significant role in preventing rock bursts and has been widely used in mining operations. The primary purpose is to reduce stress concentration in the rock mass by injecting water, thereby reducing the probability of rock bursts. Below are the steps and potential challenges of integrating water injection technology into rock burst prevention protocols:

• Challenges in Coal Mining Environments

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  Poor permeability of coal seams: Coal seams are usually compact and have low permeability, which may result in poor diffusion of water injection. Higher injection pressures or longer injection durations may be needed to ensure adequate penetration into the coal seams.

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  Risks of methane release: In coal mines, the water injection process may release gaseous methane, increasing the risk of gas explosions. Thus, gas monitoring and venting measures must be integrated to ensure the safety of the injection process.

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  Deformation and support challenges in tunnels: Water injection may soften and deform the rock layers surrounding tunnels, presenting new challenges for tunnel support. Support designs and injection plans must be combined to balance the geological changes caused by water injection with support stability.

• Challenges in Metal Mining Environments

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  Diversity of rock types: The rock layers in metal mines vary, including hard rocks (like granite) and soft rocks (like shale). The stress concentration and permeability characteristics differ significantly between different rock layers, necessitating tailored water injection strategies for each type.

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  Seismic activity induced by water injection: In metal mines, especially under hard rock conditions, high-pressure water injection may induce small earthquakes or fault slips, increasing the risk of local geological disasters. Detailed seismic monitoring and risk assessments are required.

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  Water resource management in mining areas: In some metal mines, groundwater resource management is a critical issue. Water injection may alter the hydrological conditions of the mining area, necessitating a balance between sustainable water resource utilization and rock burst prevention needs.

Incorporating water injection techniques into existing rock burst prevention programs may present several challenges. Water injection can potentially trigger groundwater contamination, especially if the water quality is not adequately treated or if the rock chemistry is complex. Therefore, using treated water sources and implementing on-site water quality monitoring can help mitigate contamination risks and ensure environmental safety. Secondly, in regions where water resources are scarce, managing the amount of water injected is crucial to avoid overconsumption. Implementing water reuse and conservation measures, such as rainwater harvesting systems, can reduce dependence on traditional water sources. Lastly, the long-term effects of water injection on rock stability must be carefully considered, as prolonged water exposure may weaken rocks and affect their stability. Long-term monitoring, combined with reinforcement support measures and stability prediction modeling, is recommended to manage potential impacts. Addressing these challenges effectively will help minimize negative environmental and resource impacts while improving rock burst prevention and control, providing a scientific and technical basis for engineering practice.

4.4. Vision for the Future

Additionally, future research could investigate the rock burst characteristics of different rock types under various water conditions and focus on developing new prevention and control technologies. Details are as follows:

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Rock explosion characteristics of different rock types in the water environment. Study the mechanical performance of different rocks in various water environments, to explore the water content, permeability and other factors on the rock strength, brittleness and stress concentration changes. This type of research can reveal the mechanism of water on different rocks in a particular environment, to help predict and control the conditions for the occurrence of rock bursts, especially in the wet or water-saturated underground engineering.

(2)

Development of new prevention and control technologies. For the risk of rockbursts in the water environment, new prevention and control technologies can be developed in the future, such as the use of nanomaterials or intelligent water control technology to change the mechanical properties of the rock, thereby reducing the occurrence of rockbursts. In addition, technologies that can actively regulate the water content of the rock body can be developed to control water infiltration and diffusion in order to enhance rock stability.

(3)

Intelligent monitoring and early warning system. Combined with advanced sensing technology, develop a system for real-time monitoring of the water content status and stress changes in the rock body, and use data-driven intelligent algorithms for rock explosion risk prediction and early warning. Such a system can provide accurate rock burst prevention information by monitoring the dynamic changes in water and rock, helping to take timely countermeasures during engineering construction.

5. Conclusions

The mechanical properties of rocks and their influence on rock burst phenomena have been a central topic in geotechnical engineering for many years. Recent studies have increasingly underscored the substantial effects of moisture on rock mechanics. This paper examines how water affects rock mechanical properties and rock burst behavior, summarizing methods and experimental advancements related to the water-induced weakening of rock bursts. The key conclusions are as follows:

• Water’s weakening effects: Water notably weakens the mechanical properties of rocks through both physical and chemical mechanisms. It accelerates the breakdown of the rock’s microstructure, enhances the development and propagation of microcracks, and decreases the rock’s strength and stiffness. Moreover, water reduces the rock’s elastic strain energy storage, increases energy dissipation, and hinders the concentrated release of elastic strain energy, thereby lessening the severity of rock failure.
• Reduction in rock burst risk: Water reduces the likelihood and severity of rock bursts by weakening the rock’s mechanical properties and diminishing its energy storage capacity. Practical engineering strategies, including water injection into the surrounding rock, high-pressure water spraying, and hydraulic cutting, are used to mitigate the risk of rock bursts.
• Considerations for rock burst testing: When performing rock burst experiments, it is crucial to consider how different types and amounts of water affect rock mechanical properties and test outcomes. In high-pressure rock burst tests, the influence of water on compressive strength, dynamic strength, and fracture patterns should be carefully evaluated. Addressing the impact of moisture comprehensively and exploring prediction and control methods under various interacting conditions can offer valuable insights for practical applications in geotechnical engineering.

In summary, ongoing research into the effects of moisture on rock mechanical properties and rock burst testing enables more accurate simulation of real-world conditions, improves the reliability of experimental outcomes, and provides valuable insights for practical applications in geotechnical engineering.