Tunnel Surrounding Rock Research Articles

Optimization of Advanced Support Parameters of Surrounding Rock in Tunnels Constructed by ADECO-RS

So as to efficiently address the distortion of surrounding rock in tunnels constructed utilizing ADECO-RS, it is crucial to define suitable parameters for advanced support systems. This study took the 8 # tunnel in the F3 portion of the E60 Expressway in Georgia as an engineering case. Initially, the original support scheme underwent systematic monitoring and analysis in the field. Subsequently, the FLAC3D 6.0 software was employed to examine the influence of the advanced pipe roof and tunnel face fiberglass bolts on the steady state of the surrounding rock. Optimization of the support parameters was also proposed. Further, the sensitivity of different parameters to the distortion of the rock surrounding the tunnel was analyzed and ranked via an orthogonal experiment. Ultimately, the effectiveness of the optimization scheme was evaluated by numerical methods and field observations. The findings of the research indicate the following: (1) The monitoring results of the original support parameters show that the irrational design of the support parameters can bring about deformation non-convergence in the tunnel’s surrounding rock. Support parameters must be optimized. (2) The spacing of the pipe roof is positively correlated with the distortion of the surrounding rock. In contrast, the length and the grouting strength are negatively correlated with the distortion of the surrounding rock. The reinforcement density, length, and lap length of glass fiber bolts exhibit an inverse relationship with the distortion of the surrounding rock. (3) The efficacy of pipe shed grouting in mitigating subsidence and deformation of the vault is superior, followed by the spacing of the supports. In contrast, the length of the supports demonstrates comparatively lesser effectiveness. Under optimal parameters, the vault subsidence was reduced by 23.2%, 10.2%, and 2.0%, respectively. The most significant factor controlling the extrusion deformation of the tunnel face is bolt lap length, followed by reinforcement density and then reinforcement length. Extrusion displacement was reduced by 52.5%, 40.3%, and 9.3%, respectively, under the optimal parameters. (4) In comparison to the primordial support system, the optimized support scheme reduces the subsidence of the vault by about one time and the convergence deformation around the cave by about two times. The research findings offer guidance for analogous engineering support design and parameter optimization.

Study on the Settlement and Deformation Characteristics of Surrounding Rock of Loess Tunnel

There is a water culvert with masonry structure in the mountain of Hanguguan Tunnel. Soil deformation caused by tunnel excavation leads to channel cracking. On the one hand, channel water infiltration leads to loess tunnel collapse, which can easily cause engineering accidents and delay the construction period. On the other hand, it will affect the channel water supply and cause social problems. In this paper, the spatial deformation of the tunnel excavation process in the loess layer is revealed through the settlement of the vault in the tunnel, the monitoring of the convergence of the perimeter, and the force monitoring of the lining support structure of the Hanguguan tunnel, and the influence of the tunnel excavation deformation on the culvert is revealed through numerical calculation. The results show that the arch at the tunnel exit has the largest settlement deformation, the larger cumulative settlement, and the faster settlement rate, and the deformation of the culvert is small, only a millimeter. Compared with the monitoring data, the numerical simulation of tunnel excavation and the vertical settlement are basically consistent with the actual situation.

Improving predictions of rock tunnel squeezing with ensemble Q-learning and online Markov chain

Predicting rock tunnel squeezing in underground projects is challenging due to its intricate and unpredictable nature. This study proposes an innovative approach to enhance the accuracy and reliability of tunnel squeezing prediction. The proposed method combines ensemble learning techniques with Q-learning and online Markov chain integration. A deep learning model is trained on a comprehensive database comprising tunnel parameters including diameter (D), burial depth (H), support stiffness (K), and tunneling quality index (Q). Multiple deep learning models are trained concurrently, leveraging ensemble learning to capture diverse patterns and improve prediction performance. Integration of the Q-learning-Online Markov Chain further refines predictions. The online Markov chain analyzes historical sequences of tunnel parameters and squeezing class transitions, establishing transition probabilities between different squeezing classes. The Q-learning algorithm optimizes decision-making by learning the optimal policy for transitioning between tunnel states. The proposed model is evaluated using a dataset from various tunnel construction projects, assessing performance through metrics like accuracy, precision, recall, and F1-score. Results demonstrate the efficiency of the ensemble deep learning model combined with Q-learning-Online Markov Chain in predicting surrounding rock tunnel squeezing. This approach offers insights into parameter interrelationships and dynamic squeezing characteristics, enabling proactive planning and support measures implementation to mitigate tunnel squeezing hazards and ensure underground structure safety. Experimental results show the model achieves a prediction accuracy of 98.11%, surpassing individual CNN and RNN models, with an AUC value of 0.98.

Calculation Method for the Loose Circle of Tunnel-Surrounding Rock Considering the Strain-Softening Effect

Calculation Method for the Loose Circle of Tunnel-Surrounding Rock Considering the Strain-Softening Effect

Analysis of the Influence of Rock Mechanics Variables on the Stability of Tunnel Surrounding Rock Based on Engineering Mathematics Applications

Tunnels are essential infrastructure elements, and it is critical to maintain their stability for both operation and safety. Using engineering techniques, this study examines the correlation between rock mass motorized characteristics and tunnel surrounding rock stability. This study utilizes the multi-sensor monitoring data of the surrounding rock mechanical characteristics and tunnel support structure collected during tunnel boring machine construction as its research object. The integrated cuckoo search optimized Upgraded dynamic convolutional neural network (ICSO-UDCNN) has been utilized for predicting the tunnel parameters. In general, the surrounding rock’s hardness correlates with its level, which in turn determines how quickly tunnels are being excavated. There is a stronger correlation of 98\% between the field penetration index (FPI) variables of the rock’s characteristic slope along the conditions surrounding the tunnel. The most significant factor influencing its deformation is the surrounding rock’s mechanical characteristics. For engineers and other decision-makers engaged in tunnel design, building, and maintenance, the study’s findings add a greater understanding of the variables affecting tunnel stability. This research provides an establishment for enhancing security protocols, lowering hazards related to tunneling operation, and optimizing tunnel engineering techniques by quantitatively evaluating the influence of rock mass mechanical factors on solidity.

Study on Discrete Fracture Network Model and Rock Mass Quality Evaluation of Tunnel Surrounding Rock

Study on Discrete Fracture Network Model and Rock Mass Quality Evaluation of Tunnel Surrounding Rock

Spalling Failure Mechanism of Surrounding Rock in Deep Hard-Rock Tunnels

Spalling Failure Mechanism of Surrounding Rock in Deep Hard-Rock Tunnels

The Influence of Rock Thermal Stress on the Morphology and Expansion Pattern of the Plastic Zone in the Surrounding Rock of a Deep-Buried Tunnel under High Geothermal Temperature Conditions

The extent of the plastic zone is critical in determining the stability and extent of damage to the surrounding rock in tunnels, crucial for designing support structures and thermal insulation layers. This study focuses on understanding how rock thermal stress affects the expansion of the plastic zone in deep-buried tunnels subjected to high geothermal temperatures, based on the derivation of the boundary line formula of the plastic zone in a high geothermal tunnel, and combined with the test results of the hydraulic fracturing method in a high geothermal tunnel of the Bulunkou Hydropower Station in Xinjiang. The findings indicate that thermal stress in the rock mass slows the growth of the plastic zone but significantly increases its extent. However, the influence of thermal stress on the shape and size of the plastic zone is less significant compared to the lateral pressure coefficient. In conditions of high geothermal temperature and geostress, rock mass thermal stress induces substantial changes in the morphology and extent of the plastic zone, which cannot be overlooked and can lead to significant errors if not properly considered. The theoretical formulas derived from engineering analysis, along with observed patterns of plastic zone expansion, demonstrate practical applicability.

Stability Analysis of Surrounding Rock and Initial Support of Tunnel Undercrossing Multi-Situational Goafs: A Reference of Construction Guidance

To ensure the construction and operational safety of tunnel undercrossing multi-situational goafs, the Huaying Mountain High-Speed Rail Tunnel, a critical section of the Xi’an-Chongqing High-Speed Railway, was taken as a case study. Based on a three-dimensional finite difference numerical simulation platform, twelve situations were established to analyze the effects of three factors: distance, scale, and angle. The stability analysis was conducted by examining the displacement and deformation characteristics of the surrounding rock, stress changes, and axial forces of the initial support for each situation. The results show that in tunnel undercrossing multi-situational goafs, the vertical deformation, horizontal convergence of the surrounding rock, and the maximum axial force of initial support are all affected. Within a certain range, changes in distance significantly impact subsidence and settlement deformation of the surrounding rock. However, as the distance increases, the horizontal and vertical displacements of the tunnel and the axial force of the initial support tend to decrease. Conversely, the scale and angle of the goaf have an opposite effect on the surrounding rock: as the scale and angle increase, the stability of the surrounding rock deteriorates. In this case study, when the distance exceeds 1.13 times the tunnel span, the influence of the goaf on the stability of the surrounding rock gradually decreases. When the angle exceeds 45°, vertical displacement decreases, and the increasing trend of horizontal displacement gradually diminishes. The conclusions of this paper can provide guidance for designing reinforcement schemes for tunnels crossing through multi-situational goafs. The findings provide valuable insights and guidance for similar engineering projects.

Research on the Mechanism of Loose Deformation in Weak Fracture Zone Tunnel Surrounding Rock and Support Control

In the fractured weak fault zone, rock mass exhibits low strength and poor self-stability. The geological conditions are complex, and when tunnels cross through fractured zones, significant deformations and collapses are prone to occur, leading to geological hazards. This paper investigates the in situ stress and deformation patterns of the Dongmachang Tunnel No. 1, proposing support solutions for addressing tunnel deformations through field experiments and numerical simulations. The on-site monitoring results indicate that despite implementing measures such as grouting reinforcement and temporary steel supports to control surrounding rock deformation, significant structural damage still occurred in the tunnel support system. The manifestations included severe sinking and cracking of the arch crown, strong inward deformation of the sidewalls, widespread cracking, crushing, and spalling of shotcrete, slight arching uplift, and severe distortion and twisting of steel arches forming a “Z” or “S” shape. To ensure tunnel safety and control the stability of excavations in weak fault zones, a comparison of tunnel deformation support schemes is conducted through field experiments and numerical simulations, indicating that replacing the upper tunnel structure and invert can effectively prevent tunnel deformations. These measures are vital for the sustainable development of tunnel.

Study on the Stress and Deformation of Surrounding Rock and Support Structure of Super Large Section Tunnels Based on Different Excavation Methods

Study on the Stress and Deformation of Surrounding Rock and Support Structure of Super Large Section Tunnels Based on Different Excavation Methods

Research on the Back-Analysis of Tunnel Surrounding Rock Deformation Considering the Deterioration Effect of Surrounding Rock Parameters

Research on the Back-Analysis of Tunnel Surrounding Rock Deformation Considering the Deterioration Effect of Surrounding Rock Parameters

A novel tool for seismic response analysis of tunnel in multilayered media based on kinematic earthquake source

Earthquake damage of underground structure indicates that the seismic response of tunnels is affected by the earthquake source, propagation medium, and local tunnel-surrounding rock system. Current research on the seismic response of tunnels primarily focuses on local tunnel systems, posing a challenge in comprehensively assessing the impact of earthquakes on tunnel group. This study introduces a theoretical seismological approach for the seismic response analysis of tunnels and presents a novel methodology for assessing the response. The proposed approach uses a kinematic seismic source as the earthquake source, assuming the geological strata as a layered medium and a tunnel as a point within a semi-infinite space. The wavenumber-integral method was used to solve for the seismic wave field and strain. To reflect the followability of underground structure to the surrounding rock deformation, we improved it and derived an analytical formula for the strain. The 2022 Menyuan earthquake was considered as a case study; the seismic damage to tunnels along the Lan-Xin Railway was analyzed using the proposed approach. The results confirm that there is a strong correlation between tunnel damage and free-field strain induced by earthquakes. The theoretical influence range of earthquake on tunnel was investigated using the diameter deformation ratio of the tunnel as an indicator. For tunnels embedded in a grade III rock mass, the theoretical range was approximately 7.0 km on both sides of the fault. For tunnels embedded in a grade V rock mass, the theoretical range can reach up to 25.9 km. The results also revealed that tunnels on the hanging-wall side of the fault had a more significant impact than those on the foot-wall side, although their affected areas were smaller.

Long-Term Stability Analysis and Structural Safety Assessment of Tunnel Surrounding Rock in Carbonaceous Slate Formation

Long-Term Stability Analysis and Structural Safety Assessment of Tunnel Surrounding Rock in Carbonaceous Slate Formation

A Novel Double-Layer Plastic Zone Elastoplastic Model and Analytical Solutions Considering the Freezing Temperature Gradient of Surrounding Rock in Cold Region Tunnels

The frost heave force and the plastic zone caused by the frost heave of the surrounding rock are the primary causes of tunnel frost damage. Current research mainly focuses on the plastic damage caused by the frost heave rock zone on the inner layer rock, while neglecting the damage caused by the outer layer rock. It will not accurately evaluate the stability of tunnels in cold regions. A new elastoplastic calculation model of the tunnel surrounding rock double-layer plastic zone in cold regions is proposed to reveal the failure law of the surrounding rock under frost heave based on thermodynamics and elastic-plastic mechanics theory. The stress field and radius of the surrounding rock in the two-layer plastic zone are determined using the Unified Strength Theory. The radius and stress distribution of the double-layer plastic zone obtained by the theoretical solution are in accordance agreement with the numerical calculation, which verifies the correctness of the theoretical solution. The case analysis of the Yuximolegai Tunnel shows that the thicknesses of the inner and outer plastic zones of the surrounding rock reach 0.57 and 2.34 m, respectively. The outer plastic zone caused by non-uniform frost heaving of the surrounding rock has a larger influencing range than the inner plastic zone. The double-layer plastic zone expands rapidly with the increase in the volumetric frost heave coefficient and elastic modulus of the surrounding rock, but are significantly suppressed by the in-situ stress. The influence of lining thickness and non-uniform frost heave coefficient on the plastic zones is relatively minor, yet their impact on the frost heave force should not be overlooked.

Investigation into the Time-Dependent Characteristics of Stress and Deformation of Weak Surrounding Rock and Lining Structure in Operational Tunnels: Model Test

During the long-term operation of tunnels, surrounding rock undergoes creep effects under environmental loads, resulting in changes in the aging evolution model of stress and deformation in surrounding rock and lining, which affects the long-term operational safety of the tunnel. Therefore, using the model test device for time-dependent characteristics of stress and deformation of weak surrounding rock and lining structure in operational tunnels, taking into account the influence of tunnel burial depth and lateral pressure coefficient of surrounding rock, a model test on time-dependent characteristics of stress and deformation in weak surrounding rock and lining structure was conducted, and the stress and deformation time-varying curves at key locations of surrounding rock and lining were obtained. The time characteristics of surrounding rock stress, the contact force between surrounding rock and lining, internal force, and displacement of lining structure were analyzed. Research findings indicate that the stress of surrounding rock, the internal force and displacement of lining structure, and the contact force between surrounding rock and lining all increase and tend to be stable over time under constant load. This implies that the stress and deformation of the surrounding rock and lining structure exhibit time-dependent changes. With changes in burial depth and lateral pressure coefficient, significant variations are observed in the various indicators of stress and deformation in the surrounding rock and lining structure, indicating both time-dependent and long-term characteristics in terms of stress and deformation. The research results provide basic data support for the study of the time-dependent characteristics of stress and deformation between weak surrounding rock and lining structures in operational tunnels and can provide theoretical and technical guidance for the long-term service status discrimination and disaster prevention and control of operational tunnels.

Stability Prediction of Surrounding Rock in Tunnel Crossing Fault Zone Based on Cusp Catastrophe Theory

Stability Prediction of Surrounding Rock in Tunnel Crossing Fault Zone Based on Cusp Catastrophe Theory

Analysis of Stress Evolution Characteristics of Surrounding Rock in Deep-buried Tunnels Crossing Fault Zone

Analysis of Stress Evolution Characteristics of Surrounding Rock in Deep-buried Tunnels Crossing Fault Zone

Blasting profile evaluation of sand-mud interbedded surrounding rock during the large-span tunnel construction

The sand-mud interbedded surrounding rock contains discontinuities, such as horizontal bedding, joints, weak planes and weak interlayers. Drilling and blasting construction in this kind of surrounding rock is very likely to cause very serious over-/under-excavation phenomenon and excessive damage to surrounding rock, and the contour flatness after smooth blasting of the tunnel is also difficult to be guaranteed, which increases subsequent construction procedures and reduces production efficiency. In order to effectively evaluate the smooth blasting effect of the sand-mud interbedded surrounding rock tunnel, taking a tunnel project in southwest China as the research background, the blasting numerical simulation of the sand-mud interbedded surrounding rock tunnel was carried out using the dynamic analysis program, and the corresponding blasting optimization scheme was obtained. Subsequently, based on fuzzy mathematical theory, the evaluation system of blasting effect of sand-mud interbedded tunnel was established by combining the evaluation criteria of tunnel smooth blasting quality. Immediately afterwards, the weights of each influencing factor index were determined, and the blasting shaping effect of the original blasting scheme and the optimized blasting scheme was evaluated. Finally, the results have shown that the optimized tunnel blasting profile effect was better than the original blasting scheme. The corresponding research results have certain guiding significance for similar tunnel blasting effect evaluation and blasting parameter design.

Microbial Mineralization-Based Rapid and High-Strength Simultaneous Repair of Surrounding Rock Fracture Zones and Lining Cracks

Grouting technology based on microbial mineralization represents a novel approach to enhancing the properties of rock and soil. Widely studied for its combination of high efficiency and environmental friendliness, this method improves the strength and permeability of rock and soil. In this study, a novel approach involving bioslurry + filling particles was proposed to reinforce sand columns. It was observed that the addition of filling particles provided new nucleation sites for crystallization, significantly enhancing the cementation effect of sand particles. After 3 days of grouting treatment, sand columns containing 10% filling particles exhibited an order of magnitude reduction in permeability with the unconfined compressive strength (UCS) reaching 2.5 MPa, more than twice that of sand columns reinforced with bioslurry alone. Additionally, this study presented a method for the simultaneous repair of sand particles and concrete cracks. Results indicated that after 3 days of the grouting treatment, the interfacial shear strength between sand columns and concrete reached 100 kPa. Moreover, for concrete with crack apertures less than 1 mm, the permeability coefficient was reduced by over 80%, while the recovery ratio of the splitting tensile strength reached 64.2%. These findings highlight the potential of microbial mineralized grouting technology in addressing practical challenges, providing a foundation for the rapid and high-strength simultaneous repair of tunnel-surrounding rock fracture zones and lining cracks.