Search Results (13)

The failure mechanism of fractured rock masses under high in situ stress is crucial to the stability of deep underground engineering. This study employs the discrete element method to investigate the evolution of the excavation damage zone (EDZ) in deep-buried tunnels. Numerical models of granite were developed to analyze how confining pressure influences single fractures with varying characteristics and to compare the behavior of filled versus unfilled fractures in double-fracture configurations. The results show the following: (1) confining pressure exerts a dual role, promoting crack initiation and EDZ expansion in intact rock and exposed fractures due to stress concentration while suppressing damage near hidden filled fractures through confinement; (2) EDZ geometry is governed by fracture orientation and filling condition, with filled fractures maintaining stress continuity and raising the crack initiation stress ratio to 0.3–0.4; (3) in multi-fracture setups, unfilled fractures facilitate stress release and crack coalescence, whereas filled fractures act as barriers, diverting cracks and promoting symmetric stress redistribution; and (4) models accurately reproduced failure patterns from real rockburst cases, validating the method for predicting fracture behavior, with filled fractures reducing EDZ area by up to 44%. These findings provide theoretical support for rockburst risk assessment and support design in complex geological conditions. Full article

Clarifying the trade-offs/synergies of ecosystem services is crucial for achieving a win-win situation in economic development and ecological conservation. Past studies have lacked research on ecosystem service functional management zones that integrate socio-economic factors and ecological conservation, particularly based on predictive scenarios. Based on the above, this study innovatively established a multi scenario simulation model and framework (EST-EMZ) for the study of ecosystem service (ES) trade-off/synergy and ecological management zoning, combining remote sensing and socio-economic data from 2000 to 2020 in the Chang-Zhu-Tan Metropolitan Area (CZTMA). The model evaluates the dynamic trade-offs/synergies among different ecosystem services under various scenarios, aiming to seek the optimal management approach for enhancing the functionality and optimizing the structure of ESs in the future of the CZTMA. The results indicate the following: (1) From 2000 to 2020, the Ecosystem Service Value (ESV) of the CZTMA gradually declined from 601.57 billion yuan to 584.65 billion yuan. Under the three future scenarios, the ESV also decreased, with the Ecological Conservation Scenario (ECS) experiencing the most minor decline, and the Economic Priority Scenario (EPS) witnessing the most substantial decrease. (2) In the historical period and the 2030 predicted scenarios, there is a predominant synergy among paired ESs in the CZTMA. Throughout the study period, the region’s dominant ecosystem service bundle (ESB) is the high-service ecological regulation bundle, primarily located in the northeastern, western, and southern areas dominated by forests. (3) Based on ESV and urbanization intensity (UI), five different ecosystem management zones were identified: water balance zone (WBZ), coordinated improvement zone (CIZ), ecologically weak zone (EWZ), ecological conservation zone (ECZ), and ecological derivative zone (EDZ). Corresponding management and protection strategies for ecosystem services were proposed. The research findings offer potential solutions for optimizing land use and managing the trade-offs of ESs in metropolitan areas. Full article

The geological disposal of high-level radioactive waste is the final step in the nuclear fuel cycle. It is realized via isolating the high-level radioactive waste in the geological environment with an appropriate system of engineered barriers. Radionuclides-containing materials must be isolated from the biosphere until the radioactivity contained in them has diminished to a safe level. In the case of high-level radioactive waste, it could take hundreds of thousands of years. Within such a long timescale, a number of physical and chemical processes will take part in the geological repository. For the assessment of radionuclide migration from a geological repository, it is necessary to predict the repository’s behavior once placed in the host rock as well as the host-rock response to disturbances due to construction. In this study, the analysis of repository barriers (backfill, concrete, inner excavation disturbed zone (EDZ), outer EDZ, host rock) thermo–hydraulic–mechanical (THM) evolution was performed, and the scope of gas-induced desaturation was analyzed with COMSOL Multiphysics. The analysis was based on modelling of a two-phase flow of miscible fluid (water and H₂) considering important phenomena such as gas dissolution and diffusion, advective–diffusive transport in the gaseous phase, and mechanical deformations due to thermal expansion of water and porous media. The importance of proper consideration of temperature-dependent thermodynamic properties of water and THM couplings in the analysis of near-field processes was also discussed. The modelling demonstrated that such activities as 50 years’ ventilation of the waste disposal tunnel in initially saturated porous media, and such processes as gas generation due to corrosion of waste package or heat load from the waste, also led to desaturation of barriers. H₂ gas generation led to the desaturation in engineered barriers and in a part of the EDZ close to the gas generation place vanishing soon after finish of gas generation, while the host rock remained saturated during the gas generation phase (50–100,000 years). Radionuclide transport properties in porous media such as effective diffusivity are highly dependent on the water content in the barriers determined by their porosity and saturation. Full article

The water inflow into tunnels will vary with the development of excavation damage zones (EDZs). Currently, there are few analytical studies on the evaluation of the water inflow into deeply buried symmetrical subsea tunnels, considering the influence of EDZs. Therefore, a solution was analytically developed using seepage mechanics, conformal mappings, and the superposition principle. The proposed solution was verified with a simplified solution and a numerical solution. A range of parametric analyses were performed to determine the effects of EDZs and spatial parameters on the water inflow, and an application to an engineering case was carried out. The results in this study reveal that the relative error between the proposed solution and the numerical solution is always less than 2.5% when the ratio of the buried depth to the radius of the tunnel is greater than or equal to 4. The water inflow increases significantly at an early stage of increasing the EDZ permeability coefficient, then gradually stabilizes and increases approximately linearly with the EDZ thickness. The effects of EDZs are greater with smaller buried depths and greater distances between the two tunnel centres. Compared with a single subsea tunnel, there is a diverting effect between the symmetrical subsea tunnels, which can be promoted by increasing the EDZ parameters. Moreover, this diverting effect increases as the buried depth increases and the distance between the two tunnel centres decreases. The application in this study shows that an increase of 13.82% to 30.42% in the water inflow occurred after considering the EDZs’ effects. The proposed solution can provide an efficient method to evaluate the water inflow into the deeply buried symmetrical subsea tunnels with EDZs. Full article

Etridiazole (EDZ) is a thiadiazole-containing fungicide commonly used to control Pythium and Phytophthora spp. Although previous studies have shown that EDZ is teratogenic, the exact molecular mechanisms underlying its toxicity remain unknown. In this study, a zebrafish (Danio rerio; ZF) model was used to explore the molecular pathways associated with EDZ toxicity. The whole transcriptome of ZF embryos exposed to 96 h of EDZ was analyzed, along with developmental abnormalities. EDZ-induced malformations were primarily related to the eyes, heart, and growth of the ZF. Compared to untreated ZF, etridiazole-treated ZF had 2882 differentially expressed genes (DEGs), consisting of 1651 downregulated genes and 1231 upregulated genes. Gene ontology enrichment analysis showed that DEGs were involved in biological processes, such as sensory perception, visual perception, sensory organ development, and visual system development, and showed transmembrane transporter and peptidase regulator activities. Metabolism, phototransduction, aminoacyl-tRNA biosynthesis, MAPK signaling pathway, calcium signaling pathway, and vascular smooth muscle contraction were among the most enriched KEGG pathways. The qPCR analyses of the eight random genes were in good agreement with the transcriptome data. These results suggest several putative mechanisms underlying EDZ-induced developmental deformities in ZF. Full article

This study is aimed at investigating the excavation damage characteristics of surrounding rock in Jinping deeply buried marble tunnels, China. According to the acoustic detection results of tunnel cross-sections under the condition of tunnel boring machine (TBM) obtained on site, the PFC microscopic parameters of Types II/III tunnel marble were simulated and calibrated through the PFC^2D program. In doing so, the excavation damage characteristics of surrounding rock of deeply-buried sections in Jinping diversion tunnels were simulated. The results reveal that the excavation damage zones (EDZ) of surrounding rock of Types II/III marble sections in Jinping tunnels are unevenly distributed around the tunnels; the largest zone is located from the top arch to the north arch shoulder. The EDZ depth and damage degree of surrounding rock rise with the increase in buried depth, and they also increase with the decrease in rock quality. Generally, the maximum damage depth of Type III surrounding rock is about 1.0 m larger than that of Type II surrounding rock under the same buried depth, which is basically consistent with the detection results of the relaxation depth of surrounding rock. The simulation well discloses the excavation damage characteristics of surrounding rock in Jinping deeply buried tunnels. Full article

The support theory of the excavation disturbance zone (EDZ) cannot provide an accurate physical explanation or theoretical description of the time-dependent properties required for the development of an EDZ. Therefore, the primary factors that cause the formation of an EDZ should be determined to further improve the support theory of the EDZ and grasp the principle underlying the control of the long-term stability of rock masses. Considering the headrace tunnel and nuclear waste repository as the research background, this study aimed to understand the deformation damage evolution process of the surrounding rock after tunnel excavation under different working conditions using the self-developed realistic failure process analysis (RFPA^2D) code. The simulation revealed the following. First, an EDZ is formed, although the deformation damage to the surrounding rock is relatively small under the action of environmental factors. Second, under the action of stress in the abovementioned case, the deformation speed, damage degree, and scope of the surrounding rock significantly increase, accelerating the formation and development of the EDZ. Therefore, the boundary of the EDZ expands significantly. Third, when environmental factors are blocked, the range of the EDZ is small due to the small deformation damage to the surrounding rock. Thus, the main factors responsible for the formation of the EDZ are environmental factors, whereas stress is only an auxiliary factor. A numerical simulation method that considers environmental factors can more accurately reproduce the formation of an EDZ. Therefore, a study of the internal mechanism of the EDZ phenomenon can provide a more in-depth understanding of the essential characteristics of an EDZ at the macro level. Furthermore, it can provide a scientific basis and method for the construction and support designs of underground excavation projects and widen the possibilities for further improving the support theory of the EDZ. Full article

An accurate theoretical model to predict the extent and mechanical behavior of the excavation damage zone (EDZ) in the surrounding rock of deep-buried tunnel is of great importance for the practical engineering applications. Using the elastic-plastic theory and combined with the analysis on the stress characteristics of the tunnel surrounding rock, this paper present a predict model for the EDZ formation and evolution. A three-zone composite mechanical model was established for the tunnel surround rock and the corresponding stress state and displacement field of three zones were derived. The effects of the strain softening and dilatancy during rock deformation was taken into account. The correctness of the proposed model was validated by the existing theoretical models. A sensitivity analysis for different influencing factors in this model was also performed. The results can benefit for the future numerical and experimental studies. Full article

Geothermal power is being regarded as depending on techniques derived from hydrocarbon production in worldwide current strategy. However, it has artificially been developed far less than its natural potentials due to technical restrictions. This paper introduces the Enhanced Geothermal System based on Excavation (EGS-E), which is an innovative scheme of geothermal energy extraction. Then, based on cohesion-weakening-friction-strengthening model (CWFS) and literature investigation of granite test at high temperature, the initiation, propagation of excavation damaged zones (EDZs) under unloading and the EDZs scale in EGS-E closed to hydrostatic pressure state is studied. Finally, we have a discussion about the further evolution of surrounding rock stress and EDZs during ventilation is studied by thermal-mechanical coupling. The results show that the influence of high temperature damage on the mechanical parameters of granite should be considered; Lateral pressure coefficient affects the fracture morphology and scale of tunnel surrounding rock, and EDZs area is larger when the lateral pressure coefficient is 1.0 or 1.2; Ventilation of high temperature and high in-situ stress tunnel have a significant effect on the EDZs scale; Additional tensile stress is generated in the shallow of tunnel surrounding rock, and the compressive stress concentration transfers to the deep. EDZs experiences three expansion stages of slow, rapid and deceleration with cooling time, and the thermal insulation layer prolongs the slow growth stage. Full article

In this paper, a Fiber Bragg Grating (FBG) stress sensor is developed to measure the stress variation between the lower Excavation Damaged Zone (EDZ) and the upper undistributed rock. The disturbance brought by the environmental temperature can be differentially compensated with two FBGs mounted symmetrically on the spokes. Through finite element analysis, it can be known that the direct stress and shear stress are pointed at the angles of 45° and 60° on both sides of the coal mine roadway, respectively. The anchor ends of the sensors are installed into the upper undistributed rock and the bolt tails of the mine roadway with a depth of 700 m and fastened by nuts to secure the load sensing device on the surface of the rock. When the shallow foundation of surrounding rock is pressed and deformed toward the coal mining road, the structural modifications can be converted into the stress of rock bolt and the strain of spoke. Thus, the FBG mounted on the surface of the spoke receives the shift information of the Bragg wavelength. The monitoring results indicate that the FBG stress sensors are sensitive to the variation of the EDZ. During the blasting, the stress amplitude varies from 40.256 to 175.058 kPa, and the creep time changes from 21 to 74 min. The proposed method can be applied in the field of underground coal mines for safety condition monitoring of the EDZ and forecasting the coal mine roadway stability. Full article

The European Union policy of encouraging renewable energy sources and a sustainable and safe low-carbon economy requires flexible energy storage systems (FESSs), such as pumped-storage hydropower (PSH) systems. Energy storage systems are the key to facilitate a high penetration of the renewable energy sources in the electrical grids. Disused mining structures in closed underground coal mines in NW Spain have been selected as a case study to analyze the construction of underground pumped-storage hydropower (UPSH) plants. Mine water, depth and subsurface space in closured coal mines may be used for the construction of FESSs with reduced environmental impacts. This paper analyzes the stability of a network of tunnels used as a lower water reservoir at 450 m depth in sandstone and shale formations. Empirical methods based on rock mass classification systems are employed to preliminarily design the support systems and to determinate the rock mass properties. In addition, 3D numerical modelling has been conducted in order to verify the stability of the underground excavations. The deformations and thickness of the excavation damage zones (EDZs) around the excavations have been evaluated in the simulations without considering a support system and considering systematic grouted rock bolts and a layer of reinforced shotcrete as support system. The results obtained show that the excavation of the network of tunnels is technically feasible with the support system that has been designed. Full article

The mechanical behavior of the sandstone at the dam site is important to the stability of the hydropower station to be built in Southwest China. A series of triaxial compression tests under different confining pressures were conducted in the laboratory. The critical stresses were determined and the relationship between the critical stress and confining pressure were analyzed. The Young’s modulus increases non-linearly with the confining pressure while the plastic strain increment $N_{\varphi }$ and the dilation angle ϕ showed a negative response. Scanning electron microscope (SEM) tests showed that the failure of the sandstone under compression is a coupled process of crack growth and frictional sliding. Based on the experimental results, a coupled elastoplastic damage model was proposed within the irreversible thermodynamic framework. The plastic deformation and damage evolution were described by using the micromechanical homogenization method. The plastic flow is inherently driven by the damage evolution. Furthermore, a numerical integration algorithm was developed to simulate the coupled elastoplastic damage behavior of sandstone. The main inelastic properties of the sandstone were well captured. The model will be implemented into the finite element method (FEM) to estimate the excavation damaged zones (EDZs) which can provide a reference for the design and construction of such a huge hydropower project. Full article

Excavation-damaged zones (EDZs) induced in underground mining and civil engineering potentially threaten tunnel safety and stability, and increase construction and support costs. In this paper, an investigation of the excavation damaged zone (EDZ) around roadways in Fankou lead-zinc mine in Guangzhou, China is performed by applying a seismic velocity method accompanied by SET-PLT-01 nonmetallic ultrasonic detector. Meanwhile, the in situ stress in the mining area was measured based on the stress relief method with the Swedish high-precision LUT system. The results indicate that the stress field is dominated by the maximum horizontal tectonic stress, and the extents of the EDZ on the roof-floor region are greater than that on the sidewall. In addition, both of the in situ stresses and EDZs show an increasing trend with an increase of depth. Analytical solutions of EDZ around circular openings in the brittle rock mass subjected to non-hydrostatic stress fields are presented in terms of the Mohr–Coulomb and generalized Hoek–Brown criteria, and validated by several cases mentioned above. The extents of EDZ solved by closed-form solutions were found to be in a great agreement with those obtained in the field. Finally, a series of parametric studies are conducted to investigate the effects of cohesion (c), friction angle (φ), geological strength index (GSI), m_i, uniaxial compressive strength (σ_c), and disturbance factor (D) on EDZ. It is shown that the effects of c, φ, GSI, and σ_c are significant; however, more attention should be paid to consider the dynamic disturbances induced by mechanical drilling, blasting, and seismic waves in tunnel excavations or operations. Full article