Rock Stress Field Research Articles

Research on the Support Technology for Deep Large-Section Refuge Chambers in Broken Surrounding Rock in a Roadway

The phenomenon of peripheral rock instability is more common in crushed bedrock roadways, and the fundamental reason for this lies in the significantly different characteristics of its peripheral rock stress field. Taking the newly dug belt inclined shaft of PingDingShan TianAn Coal Co., Ltd. No. 6 Mine as the engineering background, a mechanical model of a broken perimeter rock roadway was established by using classical rock mechanics theory. Stress distribution around the roadway of the broken perimeter rock medium was systematically analyzed, and radial and tangential stress formulas of the broken perimeter rock were deduced. Through the formula calculation, it was deduced that there was a stress drop in the intact surrounding rock outside the disturbed zone, and the radial stress of the intact surrounding rock in its deep part was relatively increased, while the tangential stress was relatively decreased. The existence of crushed surrounding rock increased the minimum principal stress and decreased the maximum principal stress of the unfractured surrounding rock, which proves that a well-maintained disturbed zone can play a lining role. Thus, a “U-shaped steel + inverted arch + bottom arch linkage beam + floor bolt compensation” support program was proposed. This joint support program easily forms a closed support structure, which is more effective in controlling the deformation of tunnel perimeter rock. The support structure can effectively resist the deformation of the surrounding rock and enhance bottom drum resistance. Through numerical simulation, it was concluded that the horizontal displacement of the two gangs was reduced by 70%, and the displacement of the top and bottom plates was reduced by 77% after optimization of the support, which effectively controlled the stability of the broken surrounding rock.

Research on the evolutionary patterns and control of surrounding rock superimposed stress field local area loading in double-layer Island face main roadway

Double-layer island working face main roadway coal pillars are affected by complex mining stress superposition, when different coal pillar width combinations, the surrounding rock stress field will produce different degrees of regional loading increase effect; the study of the surrounding rock stress field regional superposition loading increase law is meaningful to explaining the failure mode of the roadway and determining the critical control area. This study combines numerical simulation with on-site monitoring and other methods and draws the following conclusions: The superimposed loading increase law (“decreasing” → “increasing”) of the abutment pressure and deviatoric stress in the lower coal seam of the double-layer island working face during the mining; the type of the principal stress deflection in the advance working face region; and by obtaining the three types of development morphology of the deviatoric stress peak zone of the roadway and its corresponding nine evolution modes (one type of circular tube → four types of inverse hyperbolic body → four types of hyperbolic body) in the double-layered island working face mining. Indicated the critical reinforcement area corresponding to the main roadway when at different combinations of coal pillar widths; determined the main track roadway protective coal pillars width for 40 m and the shape of the roadway peak deviatoric stress zone is the inverse class hyperbolic body mode; according to the evolution mode of the peak deviatoric stress zone, determined the synergistic failure control program for the asymmetric critical zone of the roadway surrounding rock which is a targeted scientific support method; after the feedback of on-site monitoring and, the support program is reasonable and effective.

Numerical simulation analysis of the influence of karst cave orientation and surrounding rock properties on tunnel excavation

Abstract The underground distribution of complex karst geology in the Zhangjiajie region of China poses a significant threat to the construction safety of tunnels, not only increasing project investments but also severely impacting the stable operation of engineering construction. This paper, based on ABAQUS numerical simulation, explores the influence of karst caves around tunnels in different orientations of surrounding rock environments through the rock strength, stress field, and dimension of surrounding rock mass. The results are as follows: (1) With the decrease in cohesive strength of the cave surrounding rock, the stability of the tunnel is enhanced. (2) The maximum displacement of the lower cave is 0.02011 m, greater than that of the side cave, which is 0.01965 m; the maximum principal stress of the lower cave is 7.457 MPa, greater than that of the side cave, which is 7.423 MPa. The lower cave has a greater impact on tunnel construction and can further reduce the stability of the karst tunnel surrounding rock. This paper has researched the influence of caves on tunneling through surrounding rock and investigated the effects of cave orientation, cohesive strength, and other parameters on tunnel construction. It provides theoretical guidance for tunnel alignment and pre-processing of concealed caves.

Determination of mine fault activation degree and the division of tectonic stress hazard zones

This article conducts a comprehensive study on the activation characteristics of faults in the mine and analyzes the distribution patterns of the original rock stress field. Through quantitative research and analysis, we determine the partitioning characteristics of tectonic stress in the mine field under the dual effects of fault activation and original rock stress. The study also reveals the significant impact of different fault activation characteristics and different tectonic stress partitions on the stability of roadway surrounding rock. Using the Mohr–Coulomb strength criterion as a foundation, we investigate the mechanisms of fault activation and establish a mathematical model for fuzzy comprehensive evaluation. This model enables us to determine the strength level of fault activation in coal seam 9 of the Limin coal mine and construct a geological structure model. It has realized the transformation of fault activation degree from qualitative evaluation to quantitative evaluation. The stress state analysis software is used to draw the division of tectonic stress dangerous areas under the synergistic effect of fault activation and original rock stress. We then analyze the impact on the stability of roadway surrounding rock in these different hazardous areas. Utilizing the fuzzy comprehensive evaluation method, we take into account the impact of faults on the distribution characteristics of stress fields and the stability of roadway surrounding rock. This approach enables us to more accurately and comprehensively determine the hazardous areas of tectonic stress in the mine field under the dual effects of faults and original rock stress.

Study on Composite Rock-Breaking Mechanism of Ultrahigh-Pressure Water Jet–PDC Cutter

Summary The drilling industry is paying increasing attention to deep and ultradeep wells because of the gradual decline and depletion of recoverable resources on the shallow surface. However, the difficulty of conventional mechanical rock-breaking grows significantly with increasing drilling depth. It has been found that the effect of a high-pressure water jet combined with a polycrystalline diamond compact (PDC) cutter is significant and can greatly increase the efficacy of rock breaking. A composite rock-breaking experimental device with a high-pressure jet was designed to carry out composite rock-breaking experiments. Meanwhile, a composite rock-breaking numerical model of high-pressure water jet-PDC cutter was created by smoothed particle hydrodynamics/finite element method (SPH/FEM). After verifying the reliability of the numerical model through experiments, the key factors, including rock stress field, cutting force, and jet field, were extracted to analyze the composite rock-breaking mechanism. The results show that the enhancing effect of jet impact on rock breaking is mainly reflected in three aspects: (1) The high-pressure water jet can create a groove and crater on the rock surface, effectively unloading the rock stress at the bottom of the well and increasing the area of rock damage; (2) PDC cutter vibration can be efficiently reduced with high-pressure jet; and (3) the rock debris in front of the cutter is cleaned in time, avoiding the waste of energy caused by the secondary cutting and reducing the temperature rise of the PDC cutter. Besides, it has been investigated how parameters like jet pressure, nozzle diameter, impact distance, and cutting depth influence the effect of jet rock breaking. The findings indicate that the best rock-breaking efficiency and economy occur at jet pressures of 30–40 MPa. Correspondingly, in terms of nozzle angle, nozzle diameter, and impact distance, the ideal ranges are 60°, 1.0–1.5 mm, and 10 mm, respectively, wherein the ideal impact distance is approximately 10 times the nozzle diameter. This research is critical for the advancement of high-pressure jet drilling technology and the design of supporting drill bits.

Research on mechanical response and time-space distribution of supporting structure of deep-buried tunnel in naturally water-rich loess

When the water content is small, the strength and stiffness of loess is considerably high. But with the increasing of water content, the shear strength of loess decreases since the matric suction of unsaturated loess decrease. If loess is soaked in water for long time after reaching the saturated state and the linking intensity weakened, the loess would be prone to softening deformation, so as to the stress of the tunnel supporting structure, which will cause the decreasing of the stability and durability of the tunnel. Therefore, the in-situ monitoring of surrounding rock deformation and stress characteristics of supporting structure is very important and was carried out in the deep-buried tunnel in naturally water-rich loess in this paper. The time–space effect of tunnel surrounding rock deformation, mechanical response of primary support, and secondary lining were monitored and analyzed. The results indicated that the deformation of surrounding rock was quite large, and the reserved settlement was insufficient. The analysis and calculation of the surrounding rock pressure and the stress of the steel arch indicated that the primary supporting structure of the upper bench was unsafe, the arch-foot had a trend of bending deformation to the side of the tunnel′s inner contour, and the inverted arch had a trend of uplift. Through the analysis of the contact pressure and the stress of the secondary lining reinforced concrete, the sidewall had a trend to deform to a side of the tunnel′s inner contour due to squeezing of the surrounding rock. The inverted arch had a trend to uplift, indicating the significant change and redistribution of the groundwater and surrounding rock stress field. The stress and deformation of supporting structure were highly complex both in space distribution and time development. The research results could provide specific reference and guidance for the design and construction of deep-buried tunnels in naturally water-rich loess.

The shape function method of nonlinear thermal stress of granite fracture tips in a high-temperature environment

Exposed rock masses in tunnel portals are susceptible to thermal deterioration in southern China, where temperatures are relatively high. The thermal stress field of rock masses is affected by fracture shape and distribution as fractures near the surface are channels for solar radiation energy to be converted into rock thermal energy. In this study, a function expression is developed for triangular heat sources of fractured rock masses in a tunnel portal in a high-temperature environment. By the function expression, the temperature field and thermal stress field are calculated, and the influence of fracture shape parameters and multi-fracture interaction is analyzed. The results are as follows: (1) the temperature field and thermal stress field of exposed rocks are redistributed by fractures. The internal temperature of the fractured rocks is higher than that of non-fractured rocks, and thermal stress near the fracture tip increases. (2) For triangular fractures of the same length, thermal stress increases as the apex angle increases. (3) When the spacing between parallel fractures or coplanar fractures is close, the superposition effect of thermal stress becomes significant. (4) In a high-temperature environment, temperature field and thermal stress field of a fractured rock are both nonlinear as temperature and thermal stress around fractures increase significantly. The results provide effective reference for stability evaluation of fractured rock masses in tunnel portals and offer theoretical foundation for thermal diseases analysis and protection measures of tunnel engineering in high-temperature environments of southern China.

Exploring the impact of fracture interaction on connectivity and flow channelling using grown fracture networks

Quantitative assessment of the flow properties and mechanical stability of naturally fractured rock is frequently practised across the mining, petroleum, geothermal, geological disposal, construction and environmental remediation industries. These fluid and mechanical behaviours are strongly influenced by the connectivity of the fracture system and the size of the intact rock blocks. However, these are amongst the more difficult fracture system properties to characterize and honour in numerical simulations. Nonetheless, they are still the product of interactions between fractures that can be conceptualized as a series of deformation events following geomechanical principles. Generating numerical models of fracture networks by simulating this deformation with a coupled and evolving rock mass and stress field is a significant undertaking. Instead, large-scale fracture network models can be ‘grown’ dynamically according to rules that mimic the underlying mechanical processes and deformation history. This paper explores a computationally efficient rules-based method to generate fracture networks, demonstrates how different types of fracture patterns can be simulated, and illustrates how inclusion of fracture interactions can affect flow and mechanical properties. Relative to methods without fracture interaction and in contrast to some other rules-based approaches, the method described here regularizes and increases fracture connectivity and decreases flow channelling.

Theoretical analysis of the surrounding rock stress field and energy field in shallow rectangular chambers during excavation

The mechanical analysis of surrounding rock after chamber excavation is of great significance for revealing the essence of stratum disturbances. Based on the Schwarz alternating method, a shallow rectangular chamber model was decomposed into a rectangular hole problem in an infinite plane and a half-plane problem. The general iterative expression and the explicit stress solution in shallow rectangular chambers when the mapping coefficient takes three terms were established by processing the boundary conditions with a mapping function and Fourier series. Then the analytical solution of the energy density accumulation of the surrounding rock was deduced, and the reliability of the theoretical solutions of the stress field and energy field were verified by numerical simulations. The disturbance laws of the lateral pressure coefficient, burial depth and chamber shape on the two fields were also analysed. The results show that the horizontal stress at the sidewall increases with increasing lateral pressure coefficient and burial depth. The peak of the vertical stress moves away from the wall with increasing lateral pressure coefficient. The energy accumulation at the corner increases with increasing chamber height and decreases with increasing burial depth and chamber width, forming a high stress area at the sidewall. With increasing Poisson's ratio, the corner energy distribution gradually flattens, and the energy decays more rapidly with distance.

Negative Poisson’s ratio cable compensation support for 32 m super-large-span highway tunnel: A case study

Although super-large-span tunnels ensure convenient transportation, they face many support challenges. The lack of normative construction guidance and the limited number of reference engineering cases pose a significant challenge to the stability control of super-large-span tunnels. Based on the geological conditions of a super-large-span tunnel (span = 32.17 m) at the bifurcation section of the Shenzhen interchange, this study determined support parameters via theoretical calculation, numerical simulation, and engineering analogy. The support effects of negative Poisson’s ratio (NPR) anchor cables and ordinary anchor cables on super-long-span tunnels were simulated and studied. Further, based on FLAC3D simulations, the surrounding rock stress field of NPR anchor cables was analyzed under different prestressing conditions, and the mechanism of a long-short combination, high-prestress compensation NPR anchor cable support was revealed. On the basis of numerical simulations, to our knowledge, the three-dimensional (3D) geomechanical model test of the NPR anchor cable and ordinary anchor cable support for super-large-span tunnel excavation is conducted for the first time, revealing the stress evolution law of super-large-span tunnels, deformation and failure characteristics of the surrounding rock, and the changing trend of the anchor cable’s axial force, and verifies that NPR anchor cables with high preloads are suitable for super-large-span tunnel support and have advantages over ordinary anchor cables. This study can provide a reliable theoretical reference for the support design and stability control of the surrounding rock of similar shallow-buried super-large-span tunnels.

Porous Media Model of Reservoir considering Seepage Stress Coupling and Seepage Field Analysis

In the process of reservoir exploitation, the range of rock stress field changes is much larger than the reservoir area where the seepage occurs; so the amount of calculation of the existing seepage stress full coupling method is often very huge. Based on the theory of seepage mechanics and rock mechanics, a coupling analysis model of reservoir multiphase seepage and stress is established, and a numerical solution is established by using finite element and finite difference methods. The evolution law of the seepage field and stress field and the change of rock mechanics parameters can be studied, with emphasis on the readjustment of rock stress distribution and its deformation characteristics under the influence of the seepage field. At the same time, to improve the calculation efficiency of numerical simulation, considering the difference between the seepage calculation area and stress calculation area, the finite element method is improved. The percolation area of the reservoir is calculated with a fine grid to obtain a more accurate distribution of underground fluid. The coarse grid is used to calculate the stress calculation area and to reduce the calculation time. The mechanical equilibrium equation in the fully coupled theory is discretized on the coarse grid by the finite element method. The mass conservation equation is discretized on the fine grid by the finite volume method. The numerical simulation of Terzaghi’s one-dimensional consolidation problem and Mandel’s two-dimensional consolidation problem shows that the calculation results of this method are in good agreement with the analytical solution. Through the numerical calculation of a two-dimensional single-phase flow single well production problem and a three-dimensional two-phase flow five-point well pattern production problem, the influence of the seepage stress coupling effect in reservoir numerical simulation is analyzed.

Fracture evolution and fracture mechanism of tunnel surrounding rock: A case study based on laboratory tests and theoretical analysis

AbstractTo explore the fracture characteristics and fracture mechanism of the surrounding rock of straight‐walled arched tunnels, this study first carried out biaxial compression tests on rock samples and analyzed the disaster evolution characteristics under loading. Then, a stress distribution function was established using a complex function, and the distribution characteristics of the surrounding rock stress field were determined. Finally, combining the stress field with results obtained by computational tomography and acoustic emission measurements, the dynamic evolution of the main fracture mechanism of the tunnel surrounding rock was comprehensively analyzed, and the fracture mechanism of the surrounding rock of the straight‐walled arched tunnel was elucidated. The research results strengthen the understanding of rock fracture evolution during tunnel construction and operation and provide a basis for tunnel construction and surrounding rock stability analysis.

The Transient Unloading Response of a Deep-Buried Single Fracture Tunnel Based on the Particle Flow Method

Particle flow numerical simulation was used to reproduce the transient unloading process of a deep-buried single fracture tunnel. The influence of fracture characteristics on the transient unloading effect was analyzed from the aspects of stress state, deformation characteristics, fracture propagation, and energy conversion. The results shows that the surrounding rock stress field of the deep-buried tunnel is divided into four areas: weak stress area I, strong stress area II, stress adjustment area III, and initial stress area IV. The fracture has an important impact on the stress adjustment process of transient unloading of the deep-buried tunnel, and the stress concentration area will be transferred from the bottom corner of the chamber and the vault to the fracture tip. With the increase in the fracture length, the distance from the stress concentration area at the fracture tip to the free surface gradually increases, and the damage area of the surrounding rock gradually migrates to the deep area of the rock mass. At this time, the release amount of strain energy gradually decreases and tends to be stable, while the dissipation energy shows a near ‘U’ shape change trend of decreasing first and then increasing. Under different fracture angles, the number of mesocracks is significantly different. Among them, the number of mesocracks in the 60° and 30° fractured surrounding rocks is greater followed by the 0° fractured surrounding rock, and the number of mesocracks in the 45° and 90° fractured surrounding rocks is relatively less. In addition, the proportion of compression-shear cracks shows a change trend of increasing first and then decreasing with the increase in the fracture angle, and it reaches the maximum value in the 45° fractured surrounding rock.

Abutment Pressure Distribution Law and Support Analysis of Super Large Mining Height Face.

Under the condition of the shallow coal seam, the laws of roof activity after large mining height longwall face mining and prevention measures for large-area roof weighting are problems that need to be solved urgently. In the background of the super large mining height working face in the upper 108 working face of Jinjitan Coal Mine 12-2, the spatial distribution characteristics of the development and change of the mining-induced abutment pressure and the related support design in the 8.2 m super large mining height and fully mechanized mining face were conducted. It reveals the distribution characteristics of the dynamic stress field and internal and external stress fields. The influence range of the abutment pressure of the super high mining height working face was measured on site. The numerical simulation is carried out, the roadway support structure is analyzed, and the improvement measures are proposed. The research results demonstrate that: The influence range of abutment pressure is 234 m, the obvious influence range of the leading pressure is 47-60 m, and the peak position of the influence of the leading pressure is 15-20 m. The 5 m range is the lateral inward stress field of the coal pillar, the 10-15 m range is the outward stress field of the coal pillar, and the 20 m range is the original rock stress field of the coal pillar. Therefore, it is proposed that the reasonable size of the coal pillar for roadway protection is 20-22 m. Adjusting the distance between screw steel and FRP bolts from 1000 mm to 1200 mm, the length of the roof prestressed anchor cable should be appropriately reduced to 5.5-6 m according to the lithology of the roof.

Instability Mechanism and Control Method of Surrounding Rock of Water-Rich Roadway Roof

Surrounding rock properties and occurrence stability of a coal seam roof are prerequisites for ensuring the safe and efficient operation of mines. In this study, the mechanisms and control of weakened water-rich roadway roof slabs were investigated regarding the engineering background of water-rich roadway roof slab destabilization in a coal mine in the western Qingyang mining area. The spatial and temporal evolution law of rock deformation and damage of such roadways during excavation were determined through field measurements. First, we tested the strength of the roof slab surrounding rock in water-rich roadways with different water contents and concluded that the primary and excavation-disturbing fissures of the coal-sedimentary rock body are the external conditions for the occurrence of water–rock interaction in water-rich coal seam roadways. Moreover, the rock mechanical damage phenomenon exhibited by clay minerals in contact with water is the key factor leading to the destabilization of the water-rich roof slab’s surrounding rock. Second, a technical approach for controlling the stability of the surrounding rock by adjusting the form of the roadway section and optimizing the support parameters was proposed, and the distribution law of the surrounding rock stress field and displacement field of each section was revealed via numerical calculation. It is considered that adjustment of the stress and displacement control of the surrounding rock of the roadway is more favorable for the straight wall circular arch section. Based on the results of the sensitive orthogonal numerical simulation test, the technical parameters and scheme of the roadway support optimization were proposed. Finally, the research results were applied in the field, and the deformations of the top and bottom slab and the two ribs of the roadway after optimizing the section and support parameters were calculated as 61% and 34% lower, respectively, than those before optimization, indicating that the proposed approach can effectively control the deformation of the water-rich roadway’s surrounding rock and achieve more economic and effective stability control of this type of roadway. The research results provide new ideas and methods for controlling the surrounding rock of water-rich soft rock roadways in the western mining areas of China, which has broad application value and prospects.

Study on Complex Theory Solution and Numerical Simulation of Fracture Mechanics of Surrounding Rock Stress and Energy Field in Fault Type Rock Burst Stope

Rock burst is one of the most sophisticated and threatening problems in the process of mining activities of underground coal mines, which can evolve into phenomena such as gas outburst, violent ground pressure behavior of surrounding rock of stope roadway, and high dynamic load energy event of roof overburden fracture through the interaction between various influencing factors. This paper deeply studies the causes, consequences, and disaster mechanism of “2–2 rock burst accident” in Xinjulong coal mine, gives the network diagram of the relationship between the main influencing factors of fault type rock burst and high-energy events, establishes a mechanical model on this basis, and explores the influence and evolution law of fault influencing factors on the elastic strain energy field of surrounding rock of stope roadway.

Composite rock-breaking of high-pressure CO2 jet & polycrystalline-diamond-compact (PDC) cutter using a coupled SPH/FEM model

CO 2 drilling is a promising underbalance drilling technology with great advantages, such as lower cutting force, intense cooling and excellent lubrication. However, in the underbalance drilling, the mechanism of the coupling CO 2 jet and polycrystalline-diamond-compact (PDC) cutter are still unclear. Whereby, we established a coupled Smoothed Particle Hydrodynamics/Finite Element Method (SPH/FEM) model to simulate the composite rock-breaking of high-pressure CO 2 jet & PDC cutter. Combined with the experimental research results, the mechanism of composite rock-breaking is studied from the perspectives of rock stress field, cutting force and jet field. The results show that the composite rock-breaking can effectively relieve the influence of vibration and shock on PDC cutter. Meanwhile, the high-pressure CO 2 jet has a positive effect on carrying rock debris, which can effectively reduce the temperature rising and the thermal wear of the PDC cutter. In addition, the effects of CO 2 jet parameters on composite rock-breaking were studied, such as jet impact velocity, nozzle diameter, jet injection angle and impact distance. The studies show that when the impact velocity of the CO 2 jet is greater than 250 m/s, the CO 2 jet could quickly break the rock. It is found that the optimal range of nozzle diameter is 1.5–2.5 mm, the best injection angle of CO 2 jet is 60°, the optimal impact distance is 10 times the nozzle diameter. The above studies could provide theoretical supports and technical guidance for composite rock-breaking, which is useful for the CO 2 underbalance drilling and drill bit design.

A fully coupled hydraulic-mechanical model of deep tunnel considering permeability variation

When the buried depth of underground engineering exceeds 1000 m, the deep surrounding rock will show typical nonlinear deformation characteristics due to the coupling effect of high in-situ stress, and high seepage pressure. The stress field of surrounding rock will change the distribution characteristics of seepage field, and in turn, the change of seepage field will affect the distribution of surrounding rock stress field, which is a process of mutual influence and interaction. Considering the variation of permeability coefficient of deep surrounding rock and non-Darcy flow movement of fluid, a fully coupled hydraulic-mechanical analytical model of deep tunnel was proposed based on Hoek-Brown criterion and effective stress principle, and the detailed application method of the model was also given. Through the triaxial compression test under hydro-mechanical coupling, the nonlinear softening model considering seepage pressure and permeability variation equation were established, which solved two key problems of the model. The corresponding numerical calculation program was compiled based on ABAQUS finite element platform, and the reliability of the calculation program was verified by comparing with the model test results. The influence of the thickness of the grouting layer, the permeability coefficient of the grouting layer, the number of drainage holes and the depth of drainage holes on tunnel surrounding rock seepage pressure and lining seepage pressure were calculated and analyzed, and the anti-seepage optimization design of Xianglushan tunnel was carried out.

Experimental Study on the Interaction between Backfill and Surrounding Rock in the Overhand Cut-and-Fill Method

Backfilling is commonly used in underground mines to improve the stability of overlying strata. The performance of the backfill and its interaction with surrounding rock are the key issues in backfill mining research. In this paper, the displacement and stress field evolution characteristics of the overlying strata in backfill mining were analyzed by a physical model, as well as the interaction between the backfill and surrounding rock. The research results show that when backfill mining is employed, the backfill mass and the unexcavated rock mass jointly bear the loads of the overlying strata. The loads of the overlying strata are transferred to the dense backfill mass and the surrounding rock. The stress in the near-field area of the surrounding rock increases and stabilizes gradually. The backfill mass improves the stress distribution state and reduces the stress concentration of the surrounding rock, which is conducive to preventing the progressive damage of the overlying strata. In addition, the backfill mass excavation has a significant influence on the stability of the overlying strata and the surrounding rock stress field. The backfill mass is a passive force-bearing structure that can effectively manage the deformation of the overlying strata and the phenomenon of underground pressure.

Analysis of Surrounding Rock Pressure of Deep Buried Tunnel considering the Influence of Seepage

This paper takes the surrounding rock of deep tunnel as the research object and considers the action mechanism under the influence of seepage. Based on the Mohr-Coulomb criterion, the stress mechanism of surrounding rock of deep buried tunnel is analyzed by a convergence constraint method. Based on the elastic-plastic solution, the nonlinear elastic-plastic solution of the interaction between surrounding rock and lining structure considering the effect of seepage force is proposed, and the radius of surrounding rock plastic zone is obtained. The relationship between surrounding rock stress and displacement, radial deformation of lining, and support reaction force was observed. At the same time, considering the effects of seepage, strain softening, and intermediate principal stress, the surrounding rock is divided into a plastic residual zone, plastic softening zone, and elastic zone, and the stress distribution expressions of the plastic zone and each zone of surrounding rock of circular tunnel are derived. The results show that with the change of nonuniform permeability coefficient, the seepage shows anisotropy in different directions, and the closer to the horizontal or vertical direction, the more obvious the influence of nonuniform permeability coefficient on pore water pressure distribution. Seepage and material softening have different effects on the distribution of surrounding rock stress field and the size of plastic zone. Material softening is more unfavorable to the stability of surrounding rock than seepage. The intermediate principal stress coefficient has a significant impact on the tangential stress and plastic zone of surrounding rock. When the intermediate principal stress effect is not considered, the calculation results are relatively conservative and cannot give full play to the strength of surrounding rock effectively. The research conclusion can provide a theoretical reference for studying the stability of surrounding rock in tunnel excavation under water-bearing rock.