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Tunnel Construction Process: (a) Tunnel Excavation, (b) Primary Lining, (c) Inverted Arch, (d) Secondary Lining
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Tunnel excavation has a substantial effect on the stability of rock slopes. The influence of tunnel excavation on the deformation and mechanical characteristics of a bedded slope is investigated by analysing the cumulative displacement, stress, and strain of the slope using the finite-element method (FEM) and field monitoring method. The deformatio...
Citations
... Given the constraints of terrestrial transportation routes, constructing tunnels through mountains has emerged as an indispensable strategy for infrastructure development. The influence of tunnel excavation on slope stability is significant and cannot be overlooked 3,4 . Instability of tunnel slopes can gravely disrupt the seamless execution of construction projects and the regular functioning of land transportation 5,6 . ...
Continuous displacement prediction of tunnel slope deformation can serve as a basis for evaluating slope stability. For this purpose, a fusion optimized prediction model based on wavelet decomposition (WD), particle swarm optimization with genetic algorithm enhancement (IPSO), and gated recurrent unit (GRU) termed WD-IPSO-GRU is proposed. Initially, WD preprocesses noise and features in field displacement monitoring data; subsequently, IPSO dynamically sets learning factors and weights, optimizing the number of neurons and iteration times in GRU hidden layers L1 and L2, and introduces Dropout technique to prevent overfitting, enhancing GRU model performance in long-term sequence prediction tasks. Finally, leveraging the optimal solution enables prediction of GNSS displacement of tunnel slope surfaces. Results indicate that compared to GRU, recurrent neural network (RNN), and long short-term memory (LSTM) models, the WD-IPSO-GRU model demonstrates higher prediction accuracy. The root mean square error (RMSE), mean absolute percentage error (MAPE), and coefficient of determination (R²) for site 02 are 0.16, 0.18%, and 0.95 respectively, providing a new approach for tunnel slope displacement prediction.
... At present, many experts and scholars have conducted a lot of research on the mechanical properties of prefabricated underground utility tunnel under eccentric compression or local ultimate loads [29][30][31][32]. Excavation of the surrounding rock for an existing tunnel disturbed the existing equilibrium of the surrounding rock and tunnel, and the stress adjustification process in the surrounding rock and the existing tunnel may adversely affect the tunnel's lining structure [33][34][35][36]. In addition, the tunnels, especially some masonry tunnels that have been in service for a long time, maybe highly cracked under unloading-induced rebound and construction-induced disturbance, so it is necessary to reinforce the existing tunnels, especially old masonry tunnels, before the nearby construction [37]. ...
Because the urban tunnel is an essential knot of urban traffic and an easy blocking point in busy hours, upgrading the urban tunnel was necessary for the city after the tunnel being in service for a long time. However, to demolish the existing tunnel, some problems may be encountered, and these problems include occurrence of longitudinal cracks at the tunnel vault, increase of load due to infrastructure construction over the tunnel, unloading due to excavation of the rock over the tunnel, and uneven load due to asymmetric excavation or construction. To reinforce a cracked tunnel in Chongqing City, China, steel arches were installed to improve its bearing capacity, but some steel arches failed during the excavation of ground over the tunnel. Therefore, the scheme of “steel arch + shotcrete + tube column + transversal horizontal bracing” (hereinafter referred to as SASTCT) was proposed to ensure tunnel safety due to unloading and uneven load during the subsequent construction procedures. Numerical analysis indicated that the SASTCT measure can ensure the safety of the traffic and subsequent construction, which can provide some suggestions for similar tunnel upgrades in the future.
... For example, Ersöz et al. (2021), Ersöz and Topal (2018) assessed rock slope stability, considering the effects of weathering and excavation, by combining deterministic methods with the Slope Stability Probability Classification (SSPC). Similarly, Song et al. (2021) employed a combined approach of finite-element analysis and field monitoring to investigate the cumulative displacements, stresses, and strains of bedding rock slopes. They analyzed the influence of tunnel excavation on slope deformation and mechanical behavior. ...
In the analysis of stability for soil–rock mixture (S-RM) slopes, the limit equilibrium method (LEM) has limitations in capturing the properties of discrete materials. Therefore, this study proposes the use of the discrete element method (DEM) to analyze the stability of S-RM slopes. A novel approach for building a discrete element model of S-RM slopes is presented, which enables the development of S-RM slope models with varying rock contents, block size distributions, and compactness. The factor of safety (FoS) for S-RM slopes is proposed based on the gravity overload coefficient, and a slope stability criterion in the discrete element calculation cycle is established. The results indicate that for rock contents below 60%, the FoS for S-RM slopes is lower than that for pure soil slopes, suggesting that a limited number of rock blocks may potentially have a negative impact on slope stability. Only when the rock content is greater than 60%, do the rock blocks contact each other and form force transmission between the main rock skeleton, which can enhance the stability of S-RM slopes. In addition, there is a significant localization of deformation in the shear zone, as evidenced by the larger particle rotation compared to other areas.
... Currently, China has emerged as the leading country worldwide in terms of scale and complexity of tunnel and underground construction (Song et al., 2021;Xu et al., 2022). The 21st century has witnessed significant advancements in underground engineering in China (Ding and Xu, 2017;Liu et al., 2020;Huang et al., 2022). ...
The shield machine is clogged frequently when tunneling in cohesive strata. Shield clogging is closely linked to the shear strength exhibited at the clay-metal interface. To investigate the impact of anti-sticking coating technology on the shear strength at the clay-metal interface, a series of direct shear tests were conducted. The obtained test results revealed an initial increase in shear stress at the clay-metal interface as shear displacement increased, eventually reaching a state of stabilization. The shear strength exhibited a gradual increase initially, followed by a significant increase, and eventually reached a plateau with the rise in the consistency index. It was observed that the adhesion between the anti-adhesion coating and clay was relatively weak, but the presence of the anti-adhesion coating effectively reduced the risk of shield clogging.
... The effective control of the slope instability damage in tunnels and post-disaster treatment have been the focus of research in the field [18]. Sensors [19,20], optical fibers [21], and other monitoring and measuring methods are usually used to evaluate the deformation characteristics and stability of tunnel slopes, and protection techniques, such as prestressed concrete cylinder pipe [22], pipe jacking [23], and construction optimization [24,25], have been developed. However, the geological conditions of tunnel engineering are complex, and the applicability of protection techniques is not widespread. ...
Previous studies have analyzed the damage of tunnels and slopes as a single entity, ignoring the interaction effect between the tunnels and slopes, which will have an impact on the accuracy of the damage mechanism and the safety of the treatment measures. In this paper, three types of simulation models are established—the natural state, after tunnel excavation, and after reinforcement measures—considering a case study of an underpass landslide tunnel in southwest China. Based on the theory of underpass landslide tunnels and the strength reduction method, the interaction damage mechanism of this underpass landslide tunnel is revealed, and a reasonable treatment plan is proposed. The analysis results show the following: there is an obvious interaction effect between the tunnel collapse and the slope instability; a large number of mudstones common in the surrounding rock of the tunnel have rheological properties, which amplify the influence of the interaction effect of the tunnel through the landslide; and the proposed comprehensive treatment measures of “rescue inside the tunnel cave + tunnel slope treatment” have strong pertinence and effectiveness, and they fundamentally address the tunnel collapse and the slope instability of the tunnel.
... Therefore, there is a large plastic zone in the soil mass that cannot accurately identify the slip surface. Furthermore, the above FEM assumes that the slope is an ideal elastic-plastic body, and the nonuniformity and the non-linear constitutive relation of the slope cannot be accurately reflected [31,32]. This may be the reason for the inconsistency between the critical slip surface and the abnormal strain zone. ...
The real-time evaluation of slope stability is a crucial technical issue in foundation excavation and slope construction. However, conventional monitoring methods often fall short of achieving real-time and accurate measurements, which poses challenges to the timely assessment of slope stability. To address this problem, laboratory tests and numerical simulations were jointly used to evaluate slope stability in this paper. In numerical simulations, the finite element method (FEM) results clearly illustrate the distribution and evolution of internal strain during slope excavation, and the limit equilibrium method (LEM) calculates changes in the safety factor. In laboratory tests, the fiber Bragg grating (FBG) sensing technology was employed to monitor the internal strain of the slope in real time. The distribution characteristics of the slope internal strain field under the condition of stepped excavation were analyzed, and the feasibility of strain-based evaluation of slope stability was discussed. The measurements with FBG sensing technology agree well with the numerical simulation results, indicating that FBG can effectively monitor soil strain information. Of great significance is that the maximum horizontal strain of the slope is closely related to the safety factor and can be used to evaluate slope stability. Notably, the horizontal soil strain of the slope provides insight into both the formation and evolution of the critical sliding surface during excavation. The combination of numerical simulation and intelligent monitoring technology based on FBG proposed in this paper provides a reference for capturing strain information inside the slope and realizing real-time assessment and critical warning of slope stability.
... The seismic stability of slopes at tunnel portals containing complex geological conditions is particularly prominent. With the rapid development of tunnel engineering, it is also faced with various challenges brought about by the Responsible Editor: Murat Karakus changeable natural environment and complex geological conditions (Zhang et al. 2017;Song et al. 2021a). Tunnel construction inevitably runs through the inner or surrounding areas of the landslide body, causing disturbance to the rock mass and leading to landslide disasters ( Fig. 1) (Zhang et al. 2015;Wang et al. 2020a, b). ...
Tunnel‒landslide systems are important and difficult engineering problems in tunnel construction. To investigate the dynamic response characteristics of the tunnel-slope system, the seismic response characteristics of layered slopes containing double-hole tunnels at the tunnel portal were investigated using the finite element method (FEM). Two two-dimensional models, including the layered slope (Model 1) and layered slope at the tunnel portal (Model 2), incorporating finite-element meshes with infinite-element boundaries for the models were used in the numerical dynamic analyses. The results show that the lithology of the surrounding rock and the tunnel structure have impacts on the wave propagation characteristics of slopes. Obvious slope elevation and surface dynamic amplification effects can be found. The dynamic amplification effect of the slopes increases with elevation, and the amplification effect of the slope surface is greater than that of the slope interior. In addition, the directions of waves affect the dynamic response of slopes. The vertical wave has a greater impact on the amplification effect of the tunnel structure and bedrock area than the horizontal wave. Horizontal waves have a greater magnification effect in soft and hard rock strata. Moreover, the tunnel structure magnifies the dynamic response of slopes, and the amplification effect of Model 2 to that of Model 1 is 1.0–1.25, overall. The magnification effect of the tunnel structure is mainly concentrated in the adjacent area of the tunnels, and the magnification effect of the left tunnel structure is greater than that of the right structure.
... Xiao et al. [12] used three-dimensional numerical simulation to simulate six typical construction stages, analyzed the influence of the tunnel support structure, terrain, and geological conditions on the mechanical properties of pipe roofs, and revealed the change law of the stress and bending moment distribution on pipe roofs during excavation. Song [13] investigated the effect of tunnel excavation on the deformation and mechanical properties of laminated slopes by analyzing the cumulative displacement, stress, and strain of the slopes. Kaya [14] studied the damage mechanisms of slopes on road tunnel routes by means of the kinematic, limit equilibrium, and numerical stability analysis methods. ...
A low-clearance tunnel portal in the shallow-buried, joint-developed, broken, and loose surrounding rock slope deposit may cause safety issues during construction. In this study, the Guanyin Mountain Tunnel of the Chong-Ai expressway was taken as a case study, and the characteristics of the loose and broken surrounding rocks, their low clearance, and shallow buried bias were comprehensively studied. The three-dimensional numerical model of the Guanyin Mountain tunnel portal section was constructed by the Rhino, AutoCAD, and FLAC 3D software, and the whole construction process of the tunnel portal was simulated. Under the conditions of loose and broken surrounding rocks, the surrounding rock deformation, surface settlement, and slope stability at the portal of the shallow buried tunnel with a small clear distance during the construction of the center diaphragm (CD) method and circular reserved core soil method were studied. The following conclusions are drawn. During the simulated excavation of the tunnel, the maximum surface settlement is 10.74 mm, which meets the requirement of the specification. When the left tunnel is excavated, the surrounding rock deformation of the right arch shoulder should be carefully considered. The maximum deformation value can reach 14.314 mm. After excavation, the deformation rate of the right tunnel is large, and initial support should be installed in time. Since the stratum rock at the portal of the tunnel is strongly weathered, the uplift value of the arch bottom is large and gradually decreases along the axial direction. The tunnel arch bottom and arch foot are plastic areas prone to tensile damage. Therefore, it is imperative to strengthen the inverted arch support of the tunnel in the strongly weathered rock stratum. The excavation sequence of the tunnel portal section adopts the method of excavating the left tunnel first and then excavating the right tunnel, which is more conducive to ensuring the slope stability.
... Slope instability is affected by many factors such as rainfall, earthquakes, geological structures, blasting, and excavation (Song et al. 2018;Du et al. 2020b). The structural characteristics of a rock mass control the stability and deformation characteristics of rock slopes Song et al. 2021;Tao et al. 2022). The discontinuities in a rock mass degrade the strength of the rock mass and reduce the stability of slopes to a large degree; in particular, the discontinuous distribution characteristics of joints affect the stability of slopes (Li et al. 2008;Yong et al. 2018;Chen et al. 2021). ...
Because of the complexity of geological conditions and disturbance of external factors, the process of instability of open-pit landslides is very complicated. To illustrate this complex process, taking an open-pit coal mine landslide as an example, an accurate landslide geological section was established via detailed field investigation, remote sensing image interpretation, and field borehole data, in this study. A two-dimensional discrete-element model was established by the Fast CPU Matrix Computing of Discrete-Element Method (MatDEM, Version 1.60). The failure evolution of the landslide was investigated; then, the deformation behavior and dynamic characteristics of the landslide were systematically studied. The analyses of the failure process, velocity, displacement, and heat showed that the evolution of the landslide could be divided into the stages of initial deformation, accelerated deformation, and deceleration and stabilization. During the movement of the landslide, the gravitational potential energy of the landslide gradually converted into kinetic energy, heat, and elastic potential energy. The kinetic energy in the initial stage was small but rapidly increased and occupied the dominant position in the second stage. The kinetic energy gradually decreased and tended to be stable in the third stage. The final geometry and accumulation characteristics of the landslide obtained by numerical simulation were consistent with the corresponding field investigation and remote sensing interpretation. This work can provide a reference for the study of the evolution and prevention of open-pit mine landslides.
... Under the action of seismic waves, curved tunnels suffer from damage, especially in shallowly buried rock strata. The reasons are complicated, including the complexities of geological engineering conditions, stratigraphic physical and mechanically unique properties, inevitable nearby construction, and so on [1]. Large damage degrees will adversely affect the safety and serviceability of curved tunnels [2]. ...
It is still challenging to anticipate with accuracy how tunnels will behave and if they will fail when subjected to an earthquake load. In this study, assuming nonlinear material behavior and a three-dimensional inelastic rock medium, the theory of damage mechanics is applied to numerical simulation to build a curved tunnel-surrounding rock model, whose correctness was verified in laboratory experiments. To better understand the influence of surrounding rock strength on the seismic performance of a curved tunnel, the stratum parameters of the curved tunnel-surrounding rock system are quantified. The findings demonstrate that the damage process in curved tunnels is a circular process of damage change, and the model accurately captures these structural aspects of the damage evolution process. In addition, structural damage can be identified using displacement detection because the displacement of a curved tunnel is directly related to its compression damage. Finally, the seismic response of the curved tunnel-surrounding rock system is studied parametrically to determine the extent to which different parameters affect the seismic response. These parameters, including elastic modulus, friction angle, cohesion, and Poisson’s ratio, are characteristics of rock-medium materials. We then created multi-factor evaluation formulas to direct the surrounding rock to reinforce.
