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This study centers on the use of smart technology to improve the lifecycle management of underground facilities. It presents a comprehensive digital solution that addresses the challenges of underground facilities, particularly those related to the extensive use of underground space, as well as the requirements for safety, sustainability, and quality of services. The proposed solution emerged from discussions with experts, companies, and cities involved in the design, construction, and management of underground facilities. In this paper, we first discuss the major challenges of underground facilities, then, we present the development of a smart solution to address these challenges. This study demonstrates a promising perspective for the use of smart technology in the optimal management of underground facilities, and paves the way for its implementation.

The stability analysis of rock blocks on man-made excavation faces (e.g. tunnel, cavern, and slope) subject to seismic loads is an important issue in the field of rock engineering. This paper proposes a generalized block theory (GBT) by combining a pseudo-static method and the traditional block theory to evaluate the stability of blocky rock masses during earthquake activities. In our analysis, the basic safety factors are derived considering time-varying seismic loads to determine the stability of a rock block at each time step. Afterwards, two new parameters, Pu and Vu, are used to evaluate the seismic stability of a rock block, where Pu is the instability probability defined as the ratio of the time for the block becoming unstable to the total seismic loading time, and Vu is the probabilistic instability volume defined as Pu times the block volume. As for a blocky rock mass system, its probabilistic instability volume is the sum of Vu of all seismically unstable blocks and the instability probability is the ratio of its probabilistic instability volume and total volume of seismically unstable blocks. Through the simulation of a generic slope excavation, we observe that seismic loads significantly affect the stability and kinematics of a rock block during an earthquake. For a blocky rock mass, both Pu and Vu decay with the epicentral distance, in general following an inverse power law trend. Furthermore, it is found that the local site effect also has a strong influence on the slope stability under seismic loads. ISSN:1434-453X ISSN:0723-2632

PurposeEmbracing big data has been at the forefront of research for project management. Although there is a consensus that the adoption of big data has significantly positive impact on project performance, far less is known about how this innovative information technology becomes an effective driver of construction project quality improvement. This study aims to better understand the mechanism and conditions under which big data can effectively improve project quality performance.Design/methodology/approachAdopting Chinese construction enterprises as samples, the theoretical framework proposed in this paper is verified by the empirical results of the two-level hierarchical linear model. The moderated mediation analysis is also conducted to test the hypotheses. Finally, the empirical findings are validated by a comparative case study.FindingsThe results show that big data facilitates the development of technology capability, which further produces remarkable quality performance. That is, a project team's technology capability acts as a mediator in the relationship between organizational adaptability of big data and predictive analytics and project quality performance. It is also observed that two types of project team interdependence (goal and task interdependence) positively moderate the mediation effect.Research limitations/implicationsThe questionnaire study from China only represents the relationship within a short time interval in the current context. Future studies should apply longitudinal designs to properly test the causality and use multiple data sources to ensure the validity and robustness of the conclusions.Practical implicationsThe value of big data in terms of quality improvement could not be determined in a vacuum; it also depends on the internal capability development and elaborate design of project governance.Originality/valueThis study provides an extension of the existing big data studies and fuels the ongoing debate on its actual outcomes in project management. It not only clarifies the direct effect of big data on project quality improvement but also identifies the mechanism and conditions under which the adoption of big data can play an effective role.

Block theory has been widely used in analyzing the stability of rock blocks during engineering activities in jointed rock masses due to its simplicity and computational efficiency. This paper extended the traditional block theory to tunnels constructed using tunnel boring machine (TBM) by incorporating the disc cutter-block interaction mechanism. The rock blocks were divided into front, corner and rear blocks according to their spatial positions with respect to the cutterhead. The interaction between different blocks and the disc cutters mounted on the cutterhead were examined by estimating the forces exerted by disc cutters on the blocks relative to the location of the blocks in the face, direction of movement of the discs, and the depth of penetration. The estimated forces were then used in a subsequent analysis to calculate factor of safety for individual blocks and probability of blocks dislodging from its location. Two new evaluation parameters, e A and e η , were proposed to account for the probability of block instability. e A is the ratio of exposed area of unstable blocks to the face area and quantifies the size of unstable blocks relative to the face, and e η is the ratio of cutterhead rotation angles making a block unstable to the total rotation angles in a revolution which reflects the possibility of encountering an unstable block during a single round of revolution. This paper discussed the implementation of the idea of using fundamental concepts of block theory to determine block stability at the face and related analysis for assessment of face stability. The proposed method was used in evaluation of the stability conditions for a water-conveyance tunnel in western China that is currently under construction using a hard rock TBM.

It is well documented in the experimental literature that liquefied sands behave differently from virgin sands without a shearing history. In this study, undrained DEM simulations were performed on both a virgin sample and samples liquefied by cyclic loading. An identical critical state was reached regardless of liquefaction history. The fundamental mechanisms underlying the difference in the stress–strain responses between the liquefied sands and virgin sand were interpreted within the framework of jamming transition. The virgin sample was jammed throughout the simulation, characterised by a fully-percolated force transmission network of increasing resilience and mechanical stability. In contrast, the initially liquefied samples experienced an apparent phase transition from unjammed to jammed states. A fully-percolated force transmission network did not exist, and thus the unjammed samples flowed during the initial stage of loading. As loading proceeded, the force transmission network became fully percolated, and its resilience and mechanical stability developed. All of the micro-scale parameters reflecting the resilience and mechanical stability of the force transmission network reached identical values at the critical state independent of liquefaction history. Finally, a micro-scale approach based on the degree of indeterminacy was proposed to identify the four-stage post-liquefaction behaviour.

This paper investigated the three-dimensional effect through full-scale loading tests on both a single (isolated) full-ring structure and a staggered-fabricated three-ring structure for a water storage and sewage tunnel. Some observations common for both the single-ring and three-ring tests were identified: both the internal forces and deformation of the testing specimen increase as the burial depth increases; whereas, the axial force decreases but the deformation of the testing specimen increases with increasing inner water head. Comparing with the single-ring tests, the deformation of longitudinal joints and the convergence deformation of the testing specimen are significantly reduced in the three-ring tests. The reasons may be two-fold: firstly, the staggered fabrication causes the redistribution of bending moment in the longitudinal direction, which transfers a certain amount of bending moment from the longitudinal joints to the segment body of adjacent rings; secondly, the presence of thrust force leads to the closure of circumferential joints, which co-acting with the longitudinal bolts, enforces the joints to deform together with the segment body of adjacent rings and thus restricts the deformation of the longitudinal joints. It is also shown that the mechanism of bending moment transmission is not unique but depends on the loading conditions and joint locations.

The slurry infiltration process plays a crucial role in the slurry shield tunneling process, during which a filter cake is expected to form on the tunnel face to transmit the support pressure. This paper proposed a coupled computational fluid dynamics (CFD)-discrete element method (DEM) numerical approach to investigate the slurry infiltration and filter cake formation by modeling the slurry filtration column test, which incorporates the particles, fluid phase, and their interactions. The Simplified Johnson-Kendall-Roberts (SJKR) model was employed to consider the cohesion effect between slurry particles. The validity of the current approach was verified based on the Kozeny-Carman Equation modified by Ergun (1952) . The slurry filtration process was divided into four stages with different characteristics of filter cake porosity and pressure drop. Influences of some key model parameters including externally-applied pressure, friction coefficient and cohesion energy density on filter cake formation were investigated and the underlying mechanisms were explored. The law of pressure variation within the filter cake was proposed. A linear relationship between pressure drop ratio and porosity of filter cake was established, which will be useful for predicting the effectiveness of support pressure transmission due to slurry filtration.

A reconfigurable loading and data acquisition platform was developed for the first time to perform ‘standing’ prototype loading tests on a special-shape segmental lining. The testing lining was seated on rubber bearing plates installed at the invert region to simulate the structure-subgrade interaction. The mechanical characteristics of the testing lining under the deadweight condition and subject to different shallow overburden conditions were examined. The influences of lateral earth pressure and soil reaction pressure on the structural performance of the testing lining were investigated. The testing results showed that the distributions of internal forces and deformation under the deadweight condition differed greatly from that obtained in earth-and-water pressure loading tests. Although the contribution of deadweight to the internal forces was small, its influence on deformation was significant for shallowly-buried cases. The structural response of the lining in current ‘standing’ loading tests was different from that observed in conventional ‘lying’ loading tests. In ‘standing’ loading tests, the internal forces and deformation at the invert region were smaller than that at the crown area. Increasing lateral earth pressure and soil reaction pressure were beneficial for enhancing the overall rigidity of the lining structure. The testing results also indicated that the structural responses (rotational stiffness, effective rigidity ratio and moment transferring coefficient) of the lining structure depended on the joint locations, and evolved during loading.

The slurry filtration process at a tunnel face plays an important role in supporting pressure transmission, which is crucial to the stability of a tunnel face during shield tunneling. In this paper, a series of coupled computational fluid dynamics (CFD)-discrete element method (DEM) numerical simulations were carried out to model the slurry filtration column test. A simplified JKR (Johnson-Kendall-Roberts) model was used to simulate the cohesion between slurry particles. Four types of filter cake formation were identified under different combinations of size ratios between slurry and sand particles, and cohesion between slurry particles according to morphology and pore pressure distribution characteristics. These types were external filter cake, external & internal filter cake, internal filter cake & deep penetration and external & internal filter cake & deep penetration. The contact-based analysis of the constriction (void throat) sizes reveals that the dynamic evolution of the pore structure is closely related to the slurry infiltration process, i.e., the infiltration of slurry particles tends to seal the infiltration channel, which prevents infiltration of any more particles. The variation of Dc50 (the median constriction size) is closely related to the infiltration state of the slurry particles. The pressure drop within the filter cake becomes significant, i.e., the filter cake will become effective, only when the ratio of Dc50 to the size of slurry particles is below a threshold value. The current study provides new insight into the fundamental mechanism underlying the slurry filtration process during shield tunneling.

The traditional Block Theory divides a concave block into a finite number of convex sub-blocks before the removability analysis, and deals with the removability and kinematics independently, which are computationally inefficient. This paper proposes a new concept of removable domain, based on which a generalized joint pyramid (GJP) method is established to overcome the aforementioned limitations. The translational removability analysis of convex and concave blocks can be unified through GJP based on the fact that concave regions have no contribution to the removability and can thus be omitted accordingly, avoiding partition of concave blocks into convex sub-blocks. To achieve this, joints are classified as essential joints and redundant joints. Only essential joints are considered in kinematics analysis as the block will not penetrate the rock mass when sliding along the essential joints, and its motion changes once the essential joints are altered. Thereby, the number of joint planes in the removability analysis and the number of possible motion modes that need to be assessed in the kinematics analysis can be significantly reduced. The GJP method was implemented in the stereo-analytical method and its efficiency and effectiveness in the removability and kinematics analysis of translational motion were demonstrated through some generic scenarios. ISSN:0266-352X ISSN:1873-7633

Tayi tunnel is one of the component tunnels in the Jian-Ge-Yuan Highway Project located in Yunnan Province, southeast of China. It mainly passes through talus-like formations comprised of rock blocks of diverse sizes and weak interlayers with clayey soils with different fractions. Such a special composition leads to the loose and fractured structure of talus-like formations, which is highly sensitive to the excavation perturbation. Therefore, Tayi tunnel has become the controlled pot of the whole highway project as the construction speed has to be slowed down to reduce the deformation of surrounding talus-like rock mass. To better understand the tunnel-induced ground response and the interaction between the surrounding rock mass and tunnel lining, a comprehensive in situ monitoring program was set up. The in situ monitoring contents included the surrounding rock pressure on the primary lining, the primary lining deformation, and the stress of steel arches. Based on the monitoring data, the temporal and the long-term spatial characteristics of mechanical behavior of surrounding rock mass and lining structure due to the excavation process were analyzed and discussed. It is found that the excavation of lower benches released the surrounding rock pressure around upper benches, resulting in the decrease of the surrounding rock pressure on the primary lining and the stress of steel arches. In addition, the monitoring data revealed that the primary lining sustained bias pressure from the surrounding rock mass, which thereby caused unsymmetrical deformation of the primary lining, in accordance with the monitored displacement data. A dynamically adaptive support system was implemented to strengthen the bearing capacity of the lining system especially in the region of an extremely weak rock mass. After such treatment, the deformation of the primary lining has been well controlled and the construction speed has been considerably enhanced.

A variety of approaches have been proposed to determine the onset of jamming (unjamming) transition for granular medium. However, these approaches all have their own limitations. In this study, the applicability of the existing approaches in identifying the jamming (unjamming) transition instant is evaluated based on the discrete element method simulations on both frictionless and frictional specimens subjected to different loading protocols which lead to isotropic jamming, shear jamming and shear unjamming. A new approach based on Hill’s criterion of failure is proposed, which defines the transition of second order work from positive to negative as the onset of jamming (unjamming) transition. The jamming (unjamming) transition instant determined from the new approach is compared with those determined from some classic approaches. It is found that the second order work-based approach not only locates the critical solid fraction in the jamming diagram consistent with other approaches, but is also able to identify the onset of jamming (unjamming) transition for loading protocols that are difficult to be assessed by the existing approaches. This more robust approach is useful for the study of jamming phenomena under a broader types of loading protocols, and can be further employed to derive the jamming diagram of real materials.

This study explores the link between the monotonic and cyclic undrained behaviour of sands using the discrete element method (DEM). It is shown that DEM can effectively capture the flow deformation of sands sheared under both monotonic and cyclic undrained loading conditions. When subjected to cyclic shearing, flow-type failure is observed for a loose sample, while cyclic mobility is observed for a dense sample. A strong correlation between the monotonic and cyclic loading behaviour that has been revealed experimentally is also confirmed in DEM simulations: (a) flow deformation occurs in the compressive loading direction when the cyclic stress path intersects the monotonic compression stress path prior to the monotonic extension stress path, and vice versa; (b) the onset of flow deformation in q– $$p^{\prime }$$ space is located in the zone bounded by the critical state line and the instability line determined from monotonic simulations. Hill’s condition of instability is shown to be effective to describe the onset of flow failure. Micro-mechanical analyses reveal that flow deformation is initiated when the index of redundancy excluding floating particles drops to below 1.0 under both monotonic and cyclic loading conditions. Flow deformation induced by either monotonic or cyclic loading is characterized by an abrupt change of structural fabric which is highly anisotropic. The reason why the dense sample dilated during monotonic loading but showed cyclic mobility (temporary liquefaction) during cyclic loading is attributed to the repeating reversal of loading direction, which leads to the periodic change of microstructure.

In this paper, a novel loading setup was developed for performing full-scale loading tests on ‘standing’ segmental lining of a sub-rectangular shield tunnel, which for the first time allows the mechanical behaviour of segmental lining subject to self-weight to be assessed in a full-scale loading test. Granular rubber bearings with an equivalent coefficient of subgrade reaction close to hard plastic clay were used to simulate subgrade soils. The experimental results showed that the internal force distribution and deformation pattern of lining ring subject to self-weight loading differed significantly from that observed in a ‘lying’ loading test considering soil-and-water pressures due to the absence of lateral confinement and different boundary conditions. Specifically, maximum positive bending moments were observed at the crown and invert regions, and the largest negative bending moments occurred at the two waists. Stress concentration was not observed at the corners. The axial force was not universally compressive with tensile axial forces present at the crown region. Furthermore, the convergence deformation under self-weight loading was non-negligible. The overall lateral expansion deformation was close to the vertical convergence deformation, but the deformation was smaller at the invert than that at the crown. It is suggested that the influence of self-weight be considered in future full-scale loading tests, especially for shallowly-buried tunnels.

It is important to consider machine–block interaction when assessing the stability of tunnels excavated by tunnel boring machine (TBM) in blocky rock mass as the behavior of rock blocks changes with TBM progression. The cutterhead motion (advancement and rotation) alters the geometry of rock blocks and the cutters acting on the block. As a consequence, the contact forces between the cutterhead and rock blocks change, which leads to the variation of block kinematics and stability. This paper extends the traditional block theory to analyze the life-cycle behavioristics (morphology, mechanics, kinematics and stability) of rock blocks during TBM tunneling considering TBM–block interaction. The morphology analysis follows the traditional block theory but considers TBM–block interaction. The cutterhead–block interaction is decomposed into a normal component and a tangential component, both of which depend on cutterhead motion. The removability conditions and mechanical equations for three traditional translational modes and two rotational modes are derived, based on which the kinematics and stability of rock blocks during TBM tunneling can be determined. Implementation of the proposed methodologies in reflecting the dynamic evolution of block behavioristics in the process of TBM tunneling is demonstrated through a generic example.

We present a numerical study of spatio-temporal damage evolution and fracture displacements around underground excavation in fractured rock masses. We conduct a comparative analysis of this problem based on a mechanical (M) model by assuming an invariant pore pressure and a hydro-mechanical (HM) model by solving the coupling between the fluid and solid fields. In both models, an elasto-brittle constitutive law is employed to mimic the deformational and failure behavior of intact rocks, while a non-linear stress-displacement relationship is used to account for the normal compression and shear dislocation of natural fractures. In the HM model, we simulate excavation-induced transient groundwater flow in fractured porous rocks based on Darcy's law. The hydraulic and mechanical fields are linked based on the coupling mechanisms of poroelasticity (direct HM coupling) and stress-dependent material properties (indirect HM coupling). Many important HM phenomena such as stress perturbation, pore pressure fluctuation, damage evolution and fracture deformation are realistically captured in our simulation. We find that both direct and indirect couplings play important roles, and the excavation-induced disturbance in rock varies with the coupling degree characterized by the Biot coefficient. One interesting observation is that excavation-induced stress redistribution around the tunnel instantly causes perturbed pore pressure in low-permeability matrix, which gradually becomes dissipated during the post-excavation drainage. We also highlight the role of natural fractures in the tunnel inflow process and elucidate the consequences of spatial and temporal pressure variations. In addition, we analyze the microseismicity occurrence during and after the excavation to gain insights into excavation and drainage-induced responses in the fractured rock. The results of our simulation and analysis have important implications for underground excavation involved in many geoengineering applications such as civil infrastructure, nuclear waste repository and oil/gas/geothermal wellbore systems., Engineering Geology, 289, ISSN:0013-7952, ISSN:1872-6917

Capturing the cracking process during prototype loading tests of segmental lining is crucial for the design of tunnel structures. This paper presents an application case history of 3D digital image...

Identifying the morphology of rock blocks is vital to accurate modelling of rock mass structures. This paper applies the concepts of directed edges and vertex chain operations which are typical for block tracing approach to block assembling approach to construct the structure of three-dimensional fractured rock masses. Polygon subtraction and union algorithms that rely merely on vertex chain operation are proposed, which allow a fast and convenient construction of complex faces/loops. Apart from its robustness in dealing with finite discontinuities and complex geometries, the advantages of the current methodology in tackling some challenging issues associated with the morphological analysis of rock blocks are addressed. In particular, the identification of complex blocks with interior voids such as cavity, pit and torus can be readily achieved based on the number and the type of loops. The improved morphology visualization approach can benefit the pre-processing stage when analyzing the stability of rock masses subject to various engineering impacts using the block theory and the discrete element method.

Constructing deeply-buried stormwater sewage and storage tunnels is an effective method to mitigate the waterlogging and sewer overflow problems in modern cities. Prior to construction of such tunnels, a structural loading test is essential for acquiring the mechanical responses under complex loading conditions, such as cyclic inner hydraulic head, during which capturing the full-ring deformation of the tunnel lining is significant for a comprehensive understanding of the tunnel&rsquo, s mechanical behaviors. This paper introduces the application of terrestrial laser scanning (TLS) technology in the full-scale structural loading tests of a large stormwater sewage and storage tunnel, which gives the full-ring deformation throughout the tests. A data processing methodology was developed to extract the key data points of the lining segments from the original data cloud by removing noise points and mitigating data jump, based on which the deformation of testing the lining segments at arbitrary locations can be calculated. Furthermore, a post-processing software was developed to visualize the full-ring deformation. The full-ring deformation at different loading conditions and its evolution under cyclic loading were captured. It is shown that the lining&rsquo, s convergence deformation is more sensitive to the inner hydraulic head than to the external soil-water pressure, and the deformation cannot fully recover in a water-inflow-and-drainage cycle due to the presence of joints.

This paper examines the role of TBM tail-grouting on surface settlement of coarse-grained soils in urban area. The influence of tail grouting on the ground surface settlement is firstly demonstrated through a challenging shield-driven tunnel project in Beijing City, China. FEA modelling incorporating the excavation sequence and tail grouting details is then set up to support the field observations, based on which the influences of different TBM tail-grouting parameters on ground settlement are investigated, especially the asymmetric tail-grouting in which one of the two grouting openings at the upper part of the shield tail is malfunctioned. It is shown that the grouting volume variation is inconsistent with the development of the grouting pressure, and the ground deformation in coarse-grained soils is directly related to the tail-grouting pressure rather than the grouting volume ratio. Asymmetric tail-grouting will result in notable offset of the maximum surface settlement point in settlement trough from tunnel centerline which correlates exponentially with the parameter ξ defined to represent the asymmetry ratio of the grouting pressure.

A tensor-based approach is adopted to investigate the evolution of stress variability within granular media based on DEM simulations of both cyclic and static liquefactions. The bulk stress dispersion is evaluated using the effective variance of the entire stress tensor field and the local stress fluctuation is quantified by the Euclidean distance between the stress tensor of individual particles and the global stress tensor. The orientation discrepancies between the local stress tensor and global fabric tensor, and between the local and global stress tensors are examined by their joint invariants. We observe that the bulk stress dispersion decreases but the discrepancy of local stress fluctuation increases upon liquefaction. The initially deviatoric stress-dominated stress variability gradually becomes hydrostatic stress-dominated, and returns to deviatoric stress-dominated again after liquefaction. The liquefaction process is characterized by the degradation of coaxiality between the local stress tensor and the global fabric tensor and that between the local and global stress tensors. There exists a range of threshold values for such coaxiality, below which liquefaction occurs. Particles with coaxiality higher than the threshold value and particles with coaxality lower than the threshold value exhibit different roles in sustaining external loads. However, the discrepancy becomes neutral upon liquefaction.

This paper investigates the process of tail-grouting during tunnel excavation using the URUP (Ultra-rapid Underpass) method. A small-scale model test was conducted to investigate the grouting-induced influence on surrounding soils and the filling process of the grout mortar during URUP tunneling. Particular attention was paid to tunneling phases with negative and shallow overburdens. In addition, ground responses including surface settlement, grouting pressure and earth pressure around the tunnel were monitored in the experiment. Combined with the experimental observation, the grouting effect behind the tunnel linings under different overburdens was analyzed. According to the experiment results, the grouting pressure was not uniformly distributed within the tail-void, with the maximum magnitude monitored adjacent to the injection openings. The earth pressure was more sensitive to the grouting volume ratio than to the pause/restart of tail-grouting operation, and the surface settlement was positively correlated to the grouting-volume ratio (GVR) during tail-grouting. The influence zone of each opening was not uniform and symmetric within the tail-void. The experiment suggested a reasonable GVR range of 130–160% for the URUP tunneling with a shallow overburden. For negative overburden phases, a GVR smaller than 145% is suggested to avoid unexpected overflow to the ground surface during tail-grouting.

The deeply-buried tunnels serve as an effective method for the sustainable management of stormwater to mitigate the waterlogging and sewer overflow problems of modern cities in rainy seasons. This paper presents a series of full-scale structural loading tests on the segmental lining of a large deeply-buried stormwater storage tunnel considering the operation conditions, in which the cycle of water inflow and drainage was repeated. The testing results show that water inflow has notable influences on the mechanical and structural behaviors of segmental lining. The bending moment increases slightly but the axial force decreases significantly with the increasing inner hydrostatic water head. The convergence deformation develops during water inflow and recovers in the process of drainage, following a parabola pattern. However, the deformation cannot be fully recovered after complete drainage, mostly due to the residual deformation of segmental joints. The structural responses of the segmental lining remain approximately constant subjected to a limited number of loading cycles. The effects of water inflow on the distribution of internal forces and deformation deviate from the elastic solutions for homogeneous ring subjected to isotropic inner pressure. The influences of bending moment and axial force on joint behavior are unified through eccentricity. Three distinct zones associated with the interaction condition between adjacent blocks at the joint are identified for the relationship between joint deformation and eccentricity, and also for the relationship between joint rotational stiffness and eccentricity. The observations made in the current study may shed light on the design and construction of similar projects in pilot cities committed for the Sponge City policy of China.

Circular tunnels are usually encountered when excavating in weak soil medium at shallow depth and using shield machines. However, special shaped tunnels such as squared tunnels and sub-rectangular tunnels are also recently used to improve the efficiency of underground space use. This paper focuses on improving the performance of the Hyperstatic Reaction Method (HRM), which is a numerical method, for the case of squared or sub-rectangular tunnels. Special attention is paid to the tunnel shape influence by using various tunnel wall radii. The numerical HRM model was validated based on a comparison with the finite element method (FEM). The results indicated that HRM can be effectively used to estimate the behavior of squared or sub-rectangular tunnels. Then a parametric study was conducted to highlight the influence of the earth pressure coefficient and of the soil Young’s modulus on the structural forces, and deformations induced by the excavation in the tunnel lining.

The ultrarapid underpass (URUP) tunneling method, in which a shield machine is launched and received at the ground surface level, has been developed for tunneling in congested areas. This p...

A new block-classification method for tunnel construction using a tunnel-boring machine (TBM) to capture the geometrical and mechanical transformation of rock blocks in the course of TBM excavation is proposed in this paper. The machine–block interaction is interpreted by dividing the joint blocks into blocks influenced by TBM excavation and blocks uninfluenced by TBM excavation. The influenced blocks are categorized further as contacting or noncontacting blocks according to whether they are in contact with the TBM. The contacting blocks include the front block, the corner block, and the rear block, based on the spatial location of blocks with respect to the cutterhead. Different types of blocks have distinct kinematic and mechanical characteristics. The sizes and shapes evolve, and the categories may be changed for rock blocks during excavation. The identification algorithms for influenced blocks and three types of contacting blocks are presented. Finally, a simple example considering a double-shield TBM tunnel excavation is used to illustrate the effectiveness of the new block-classification approach to guide TBM tunneling. The new classification approach will be helpful in evaluating the block removability and the possibility of cutterhead clogging and to shield blockage during tunneling with a TBM.

A series of prototype structural loading tests were performed in this paper to explore the mechanical behavior of a large special-shaped shield tunnel lining towards failure. To replicate the real working conditions, the testing specimen was fabricated and tested in a ‘standing’ state. It was shown that, similar to circular tunnels, the internal forces and overall deformation of the special-shaped lining structure increased with increasing burial depth. However, the maximum negative bending moments of the special-shaped lining structure were present at the shoulder areas rather than at the waist areas. The two key design parameters, effective transverse rigidity ratio and rotational stiffness, were shown to evolve during loading. A unique relationship between the joint rotational stiffness and eccentricity was obtained, which could be divided into an axial force-dominating phase and a bending moment-dominating phase. Different cracks appeared at different loading stages and the crack width also evolved as loading proceeded. Empirical correlations between various structural properties and cracking characteristics were established, based on which the progressive failure process was elucidated. It was found that due to the transferring of bending moment, cracks were mostly concentrated on segmental bodies in the ring(s) adjacent to the longitudinal joints.

Soil disturbance has always been the major concern in shield tunneling activity. This paper presents the investigation on the micro-scale responses of the soils during shield tunnel excavation in sandy-cobble stratum. The code paraEllip3d is employed in discrete element method (DEM) analysis in which the soils are mimicked as an assembly of ellipsoids. Triaxial tests on the micro-scale responses of cobbles are carried out using the materials sampled from the tunnel face during construction period, and corresponding DEM simulations are performed to calibrate the micro parameters for the ellipsoids. On this basis, the face instability process during the shield tunneling in cobbles is studied using 1 g model test as well as corresponding DEM simulation. The micro-scale responses of cobbles are investigated by triaxial test as well as corresponding DEM simulations. Multiple material responses are discussed in the DEM simulations, including the stress&ndash, strain relationship, the contact distribution, and the force chain evolution in the elementary and model test. Finally, the mechanism of tunnel face instability in cobbles are discussed on the basis of aforementioned investigations.

The macro stress–strain responses of sands are closely related to the evolution of the force transmission network. In this paper, variations of the mechanical stability and reversibility of the force transmission network during the cyclic liquefaction process are explored using discrete element method (DEM) simulations. It is shown that sands degrade gradually from hyperstatic states to isostatic states during cyclic loading and become hypostatic when approaching liquefaction. During this process, the number of excessive contacts decreases gradually and the sample becomes unjammed. An effective and resilient force transmission network should contain enough mechanically stable particles to spread throughout the entire sample. Structural degradation during cyclic loading towards liquefaction is associated with decreasing reversibility of the force transmission network that is characterized by increasing mean squared displacement, increasing fraction of broken contacts and decreasing size of the largest force transmission network. Flow deformation and the development of significant double-amplitude axial strain are attributed to the inability of a large proportion of the broken contacts to re-form post-liquefaction. The size of the largest force transmission network ( S L ) decays linearly with mean effective stress and there exists a critical value of S L below which liquefaction will occur.

This paper investigates the influences of confining pressure and cyclic deviatoric stress on the undrained cyclic loading behavior of saturated granular materials using DEM. Cyclic mobility, which is typical for sand under cyclic loading conditions in the absence of initial deviatoric stress, is captured. DEM simulation results show that the number of loading cycles to initial liquefaction increases with increasing confining pressure but decreases as cyclic deviatoric stress increases. Cyclic mobility is characterized by alternating abrupt drops and gains of coordination number accompanied by alternating abrupt decreases and increases of deviatoric fabric. The runaway deformation can be either compressive or extensive depending on whether the instability state under monotonic compression loading conditions or that under monotonic extension loading conditions is reached first during cyclic shearing.

Tunneling in highly permeable ground using a slurry shield machine can be challenging because it is difficult to form the so-called filter cake on the tunnel face to transport the support pressure. Consequently, destructive accidents might happen, such as face instability and water inrush. How to form an efficient filter cake in time is crucial during engineering practice, especially in ground with high permeability. Various theoretical and experimental analyses regarding the formation of filter cakes have been conducted. However, due to the complexity of this problem, which has to incorporate the mechanical and hydraulic behaviors of the fluid&ndash, solid mixture system, few numerical simulations are found in the literature. In this paper, with the aid of a newly developed numerical tool, a coupled CFD (computational fluid dynamics)&ndash, DEM (discrete element method) simulation is established to study the slurry infiltration and filter cake formation during slurry shield tunneling. The slurry infiltration process is simulated by modelling the scheme of the infiltration column test, in which sedimentation behaviors of slurry particles are captured and compared with experimental results. The results show that the sedimentation behaviors of the slurry particles and filter cake formation phenomenon are well captured by simulations and in accordance with the experiments, which indicates the robustness of the coupled CFD&ndash, DEM simulation used in present work.