This study aims to reveal the floor heave failure mechanism of weakly cemented soft rock roadways under tectonic stress and propose effective control measures. In this study, the mechanical properties and creep properties of weakly cemented mudstone were analyzed through triaxial compression tests and triaxial creep tests. Based on the Burgers model, an equivalent nonlinear creep damage model that can reflect the post-peak strain softening characteristics of mudstone was established. Numerical simulation analysis was carried out using the discrete element program to reveal the floor heave deformation and failure mechanism of soft rock roadways and propose effective control measures. The study found that the creep damage model has a high degree of agreement with the creep test results and can well reflect the creep damage and strength attenuation characteristics of mudstone. The floor heave is dominated by the extrusion-flow type, and the main causes of this roadway floor heave are the mudstone's high creep response, high horizontal tectonic stress, and incomplete support structure. A comprehensive control technology of "active–passive combined support" was proposed and implemented on-site, and the floor heave deformation was reduced by 85.3% compared with that under the original support. This study can provide valuable references and a basis for the mechanism analysis and prevention of large floor heave deformation in soft rock roadways. © 2025 Elsevier Ltd

Featured Application A framework combining energy damage evolution and PSO-BP optimization enables accurate prediction of tunnel instability and support design, improving safety and guiding tunneling under complex geological conditions.Abstract This study focuses on tunnel construction in fault fracture zones and systematically investigates the energy evolution and damage catastrophe mechanisms of surrounding rock during excavation, based on energy conservation principles and cusp catastrophe theory. A tunnel instability prediction and support optimization framework integrating energy damage evolution and intelligent optimization algorithms was developed. Field tests, rock mechanics experiments, and Discrete Fracture Network (DFN) numerical simulations reveal the intrinsic relationships among energy input, dissipation, damage accumulation, and instability under complex geological conditions. Particle Swarm Optimization-Back Propagation (PSO-BP) is applied to optimize tunnel support parameters. Model performance is evaluated using the Mean Absolute Error (MAE), Mean Squared Error (MSE), Mean Absolute Percentage Error (MAPE), and R-squared (R2). The results show that upon reaching structural mutation zones, the system damage variable (ds), displacement, and dissipated energy increase abruptly, indicating critical instability. Numerical simulation and catastrophe feature analysis demonstrate that energy-related damage accumulation is effectively suppressed, the system damage variable decreases significantly, and crown stability is greatly enhanced. These findings provide a theoretical basis and practical reference for optimizing tunnel support design and controlling instability risks in complex geological settings.

The time-delayed failure of rocks is a potential geological hazard, and it poses severe challenges to the stabilization and safety in deep rock engineering. To explore the triaxial time-delayed failure process under high-stress conditions, this paper conducts time-delayed triaxial compression (TDTC) experiments on multiple granite samples. A three-dimensional grain-based model (3D-GBM) for pre-cracked granite is constructed. Combined with the parallel-bonded stress corrosion (PSC) model, TDTC numerical simulations are carried out to investigate the triaxial time-delayed damage and fracture characteristics of pre-cracked granite under high-stress levels. The results show that when the stress level k is 85 %, the fracture characteristic of each type of sample is the most obvious. The fractal dimension and damage variable of the type B-30 sample are the largest. The pre-cracked granite 3D-GBM based on the real mineral composition achieves a high consistency between the numerical simulations and the experimental results in conventional triaxial compression tests. For all types of samples, the axial strain confining pressure compliance during the time-delayed deformation stage shows a gradual upward trend as k increases. The fracture degree is most significant when k = 85 % for the same type of samples. The x-direction particle displacement of the type B-30 sample is the largest. The number of intragranular cracks in all samples is generally larger than that of intergranular cracks for k = 85 %. © 2025 Elsevier B.V.

Tunnel roofs with weak surrounding rock are highly susceptible to progressive collapse failure under the seepage effect. To study the progressive collapse mechanism of a tunnel roof, a fluid-solid coupling model test was carried out for a tunnel with weak surrounding rock under complex geological conditions. The progressive failure and stress evolution of the tunnel-surrounding rock were analyzed. A three-dimensional progressive collapse mechanism of the tunnel roof was modeled, and upper bound analysis of the progressive collapse mechanism under weak surrounding rock was carried out, considering the seepage effect. Influences of relevant parameters on the secondary collapse range and collapse gravitational force were studied. Regarding the parameters of the surrounding rock as random variables, the progressive collapse characteristics of rock surrounding the tunnel roof were analyzed. The collapse arches for the model test, theoretical calculation, and actual site were compared, to verify the rationality of the progressive collapse mechanism. The results show that, for the fluid-solid coupling, similar materials better simulate the tunnel progressive failure process under the groundwater effect. In the model test, the tunnel-surrounding rock produces a stress relaxation zone, which gradually extends to the surrounding rock depth. The incremental changes in the collapse arch are more significant along the vertical direction than along the horizontal direction. The secondary collapse range in the tunnel progressive collapse mechanism is related to the ratio of the compressive strength of the surrounding rock between the primary and secondary collapse, and the variation of relevant parameters has some influence on the collapse range and collapse gravitational force. The tunnel collapse characteristics determined by regarding the surrounding rock parameters as random variables are similar to the actual collapse characteristics, and rationally predict the progressive collapse range of the tunnel-surrounding rock. These results provide a theoretical basis for tunnel construction and safe operation.

为研究冻融循环作用对砂岩物理力学特性的影响，针对不同含水质量分数的砂岩，开展不同冻融循环次数的冻融循环试验和单轴压缩试验。基于岩石损伤力学理论，构建砂岩冻融-荷载耦合损伤模型，并验证模型的可靠性。研究结果表明：随着冻融循环次数的增加，砂岩产生累积冻融损伤，导致其强度降低，变形量增加。冻融-荷载作用下岩石总损伤值的变化曲线整体呈“S”型，验证了该损伤模型对受载冻融砂岩力学特性的适配性。研究结论可为寒区隧道工程冻害灾变防治提供参考。

冻融循环对岩石的损伤劣化严重影响寒区隧道工程的长期服役性能。为获取裂隙岩石冻融损伤细观特征和冻融后受载力学特性，开展了不同冻融循环次数下饱水裂隙砂岩力学特性试验，推导了冻融过程冻结水体积增量、补给量与冻融循环次数的关系方程。采用颗粒流方法构建一种基于水冰相变体积膨胀理论的岩石冻融劣化模型，通过室内试验验证该模型的可靠性。研究表明：随着冻融循环次数N的增加，试样的力学特性均表现为线性衰减，衰减程度与N呈正相关，且当裂隙倾角为30°时，试样表现的力学特性最弱；裂隙试样在冻融作用下裂隙处的劣化程度大于其它部位，除试样表面颗粒剥落之外，沿裂隙端部产生冻融微裂纹，冻融损伤在试样表层及内部不断积累；颗粒流冻融过程产生的细观微裂纹以张拉裂纹为主，且裂纹数量与N呈正相关，冻融微裂纹由试样表层逐步向内部扩展发育，微裂纹的数量及分布特征影响试样受载破坏形态，且多表现为分布于受载破坏主破裂带附近的次生裂纹破裂带。该研究为冻融作用下岩石损伤劣化过程提供了新思路与新参考，也有助于推动寒区隧道工程灾变预测和长期服役性能评估。

The creep failure of rocks is related to its microstructure, external loading and time. A nonlinear yield model was introduced to describe the variation in the cohesion and friction angle with plastic strain and intergranular stress. The mechanical properties and creep characteristics of deep granite were obtained by indoor tests, and a variable radius particle clump model was constructed based on the particle flow method. The bond-weakening-friction-strengthening model was combined with the parallel bond stress corrosion method to establish the bond-degradation creep model of granite. The creep failure time, creep rate and tension and shear fractures number of the parallel bond stress corrosion model and the bond-degradation creep model were compared and analyzed to verify the applicability of the model. The fracture evolution law of deep roadway surrounding rock was studied based on the bond-degradation creep model. The results show that the rock failure characteristics and tension-compression ratio obtained by the variable radius particle clump modeling method are closer to the actual situation. Compared with the parallel bond stress corrosion model, the creep failure time of the bond-degradation creep model is shorter, more microfractures are generated during the failure process, and the numerical creep curves are more consistent with the test curves. The deep roadway vault shear failure and sidewall plate crack failure characteristics calculated based on the bond-degradation creep model are basically similar to the actual project situation. The bond-degradation creep model can better simulate the creep damage process of rocks under high stress, and is more suitable for analyzing the fracture evolution law of surrounding rock in deep hard rock cavern. © 2025. The Author(s).

Tunneling through existing buildings in shallow soft rock strata is a key and difficult issue in tunnel construction. To investigate the disturbance and deformation mechanism of soft rock stratum in the tunnel underpass project, based on the Longquanshan Tunnel, a more suitable construction method for shallow tunnel underpassing existing buildings was proposed − the New Sidewall (NS) method. Using FLAC3D, a refined numerical model of a shallow tunnel passing under a glass trestle was established to study the disturbance effect of different construction methods on the soft ground layer and the degree of influence of the glass trestle piles. The applicability and control effect of the work method was verified combined with on-site monitoring data. Results indicate that the large deformations and other engineering problems in the tunnel are mainly caused by the weak surrounding rocks in the shallow inlet section. The cover layer of the shallow buried section is thin and unable to form an arch, and the original three-step method is ineffective in controlling deformation. The deformation of the surrounding rock is controlled significantly when high-pressure rotary jet grouting piles are used to reinforce the ground layer in the tunnel section. However, the deformation is still large when using the Cross Diaphragm (CRD) method, Center Diaphragm (CD) method, and three-step method. The NS method has the advantages of optimized zoning of the palm face and a temporary support structure for large deformations. The proposed NS method of construction can effectively reduce excavation disturbance, control the deformation of surrounding rock and surface, and ensure the safe operation of the glass stack. © 2025 Elsevier Ltd

Damage deterioration of rock by freeze-thaw cycles seriously affects the long-term service performance of tunnel projects in cold regions. In order to obtain the fine-scale characteristics of freeze-thaw damage and post-freeze-thaw loading mechanical properties of fissured rocks, tests on the mechanical properties of water-filled fissured sandstones under different levels of freeze-thaw cycles were carried out. Equations were derived to describe the relationship between the volume increment of frozen water, recharge, and the number of freeze-thaw cycles throughout the freeze-thaw process. The particle flow method is used to construct a rock freeze-thaw deterioration model based on the theory of water ice phase transition volume expansion, and the reliability of the model is verified by indoor tests. It is shown that with the increase of the number of freeze-thaw cycles N, the mechanical properties of the specimens show linear attenuation, the degree of attenuation is positively correlated with N. And the mechanical properties of the specimens are the weakest when the fissure inclination angle is 30°. The degradation of fissure specimens due to freezing and thawing is more pronounced than in other parts of the sample. In addition to surface particle flaking, microcracks develop at the ends of the fissures. This results in freeze-thaw damage accumulating both on the surface layer and internally within the specimen. The fine microcracks produced by the freeze-thaw process of granular flow are mainly tensile cracks, and the number of cracks is positively correlated with N. The freeze-thaw microcracks are gradually extended and developed from the surface layer of the specimen to the inner layer, and the number of microcracks and their distribution characteristics affect the load damage morphology of the specimen, and they are mostly manifested as the secondary cracks distributed in the vicinity of the main rupture zone of the load damage rupture zone. This study provides new ideas and references for the damage degradation process of rock under freeze-thaw action, and also helps to promote the prediction of catastrophic changes and long-term service performance assessment of tunnel engineering in cold regions. © 2025 Biodiversity Research Center Academia Sinica. All rights reserved.