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Several numerical challenges exist in the analysis of water-mooring line systems which require robust, yet practical, methods to address this type of fully coupled nonlinear dynamic problems. The present study proposes a novel class of numerical techniques for the formulation and implementation of a fully coupled dynamic system which involves water flows and catenary mooring line system. In particular, the three-dimensional water flow model is replaced by a simplified multilayer shallow water system with mass exchange terms between the layers including frictional forces at the bed topography and wind-driven forces at the water free-surface. Coupling conditions between the multilayer shallow water model and the mooring line system are also investigated in the current work. As numerical solvers we implement a fast finite volume method for the multilayer shallow water equations and a nonlinear dynamic analysis for the mooring line based on elastic catenary cable elements. Efficient calculations of the interaction forces between the shallow water flow and the submerged mooring line system and associated numerical implementations are also discussed. The accuracy and computational advantages of the proposed fully coupled system are verified using a series of well-established benchmark problems and wind-driven flows over both flat and non-flat beds. The computational results obtained show high performance the developed model and demonstrate the ability of the method to simulate fully coupled dynamic water-mooring line systems. • Development of simplified models for water-mooring line systems. • Multilayer shallow water flows with mass exchange for wind-driven flows. • Numerical methods based on elastic catenary cable elements for mooring line systems. • Interaction forces between the shallow water flow and the submerged mooring line system. • Numerical assessment and verification of fully coupled dynamic water-mooring line systems. [ABSTRACT FROM AUTHOR]

This paper presents a new computational strategy for kinematic upper bound limit analysis in the presence of seepage forces with an improved mesh refinement scheme. In particular, the original adaptive refinement scheme is enhanced with a simple but efficient error-indicator of the nodal plastic dissipation for high-order elements. The proposed refinement criteria facilitate a precise quantitative evaluation of errors in the nodal plastic energy dissipation across each element and ensure that the rate of total refined element number gradually decreases with adaptive step. Adhering to two-dimensional steady state seepage condition, numerical details regarding the calculation of total water head distributions for the seepage field are provided. In a similar manner as treating the unit weight of the soil, the effects of seepage forces are incorporated as body forces in the upper bound formulation. Detailed numerical procedure of the proposed error indicator-based h -adaptive refinement scheme incorporating the inclusion of seepage forces is addressed and implemented in the in-house code. Several benchmark problems, including both homogeneous and non-homogeneous soils, are analyzed to evaluate the excellent performance of the proposed error indicator-based h -adaptive refinement scheme in upper-bound limit analysis and assess the influence of seepage forces on the stability of geostructures through comparison with that for dry condition. [ABSTRACT FROM AUTHOR]

A hybrid material point/finite volume method for the numerical simulation of shallow water waves caused by large dynamic deformations in the bathymetry is presented. The proposed model consists of coupling the nonlinear shallow water equations for the water flow and a dynamic elastoplastic system for the seabed deformation. As a constitutive law, we consider a linear elastic-non-associative plastic model with the Drucker-Prager yield criterion allowing for large deformations under undrained cases. The transfer conditions between these models are achieved by using forces sampled from the hydraulic pressure and the friction terms along the interface between the seabed soil and shallow water. A detailed description regarding the coupled algorithm for the hybrid material point/finite volume method is presented. Several numerical examples are investigated to demonstrate the performance of the finite volume method for simulations of shallow water flow and the material point method for capturing the large deformation process of the solid phase. We also present numerical simulations of an undrained clay column collapse that induced shallow water waves and a dam-break problem to demonstrate the excellent performance of the proposed hybrid material point/finite volume method. [ABSTRACT FROM AUTHOR]

This paper presents a stability study on the collapse mechanisms of a plane-strain tunnel face in c - ϕ soils using the upper bound finite element method with rigid translatory moving elements (UBFELA-RTME) and nonlinear programming technique. Practical considerations are given to the unlined length influence behind the tunnel face. An advanced mesh adaptive updating strategy is adopted, aiming to improve the computational efficiency, the accuracy of upper-bound solutions, as well as the produced collapse mechanisms. The unlined length influence on the face stability and collapse mechanism of the tunnel face are determined with various combinations of tunnel depth ratios, soil friction angles, and dilatancy angles. Using the UBFELA-RTME with the Davis's approach and a mesh adapting strategy, the non-associated plasticity flow rule can be well approximated. The developed technique was validated against different numerical methods, and it is concluded that the tunnel face stability can be improved by increasing soil friction and dilatancy angles, and yet weakens as the unlined length increases where a mesh-liked collapse zone gradually appears on the tunnel vault top. It gradually evolves to a global collapse failure till the ground surface. The findings contribute to a better understanding of the ground surface failure under the unlined support length influence in tunnel construction. [ABSTRACT FROM AUTHOR]

The stability of dual circular tunnels subjected to surcharge loading in cohesive-frictional soils, obeying the Mohr–Coulomb failure criterion, is determined by an upper bound finite element method combined with rigid translatory moving elements (UBFEM-RTME). The stability results, which are considered to be influenced by the soil internal friction angle ( ϕ ), ratio of the tunnel cover to the tunnel diameter ( C / D ), ratio of the tunnels’ center-to-center distance to the tunnel diameter ( S / D ), and ratio of the product of the soil unit weight and the tunnel diameter to the soil cohesion ( γD / c ), are presented in the form of dimensionless stability numbers ( σ s / c ) and failure mechanisms. The results reveal that the values of stability numbers decrease continuously with increasing γD / c and increase with increasing C / D , S / D , and ϕ , except in the cases of moderate depth and close proximity. Most of the obtained failure mechanisms are constituted by two wedge-shaped areas composed of two groups of crossed slip lines and a complete rigid area. The results of this study compare reasonably well with the solutions reported in the literature. [ABSTRACT FROM AUTHOR]

This study presents an efficient and robust adaptive remeshing strategy in the kinematic upper-bound limit analysis in association with using six-node triangular elements and Second–Order Cone Programming (SOCP). In particular, a Synchronous Mesh Refining–Coarsening (SMRC) algorithm following a posterior plastic dissipation-based error indicator and the well-known Delaunay triangulation are implemented into the Upper Bound Finite Element Method (UBFEM). Detailed numerical implementation of the proposed method is presented, and its computational performance is demonstrated through several benchmark problems and comparisons with those solutions obtained using Pure Mesh Refinement (PMR) scheme. The proposed method, named UBFEM-SMRC, is proved to generate more rigorous solutions for all considered examples and significantly reduce the computational burdens of the UBFEM-PMR. Additionally, more clear adaptively refined mesh zones with intensive plastic dissipations, which can readily reproduce the potential failure mechanisms of geotechnical problems, are observed by successive performing of the proposed synchronous adaptive mesh refining–coarsening process. [ABSTRACT FROM AUTHOR]

The Material Point Method (MPM) has been gaining increasing popularity as an appropriate approach to the solution of coupled hydro-mechanical problems involving large deformations. This study extends the implicit GIMP-patch method for coupled poroelastic problems recently proposed by Zheng et al. (2021b) to tackle large-deformation problems in (nearly) isochoric elastoplastic geomaterials, particularly by remedying the numerical inaccuracies caused by volumetric locking, such as spurious stress oscillations and an excessively stiff overall response of the system at hand. To overcome these difficulties in two-phase coupled analyses, the B ¯ approach of Hughes (1980) is incorporated into an existing version of the implicit GIMP-patch method. Details regarding the formulation and implementation of the proposed method are provided, while several benchmark problems are numerically analysed to evaluate its performance in the presence of elastoplastic behaviour. Particular emphasis is placed on (i) mitigating effective stress oscillations and (ii) solving several two-phase, coupled, large deformation geotechnical problems. The numerical results confirm the suitability of the implicit B ¯ GIMP-patch method for the solution of geotechnical problems spanning weak to strong hydro-mechanical coupling and small to large deformations. [ABSTRACT FROM AUTHOR]

This paper presents a single-point Material Point Method (MPM) for large deformation problems in two-phase porous media such as soils. Many MPM formulations are known to produce numerical oscillations and inaccuracies in the simulated results, largely due to numerical integration and stress recovery performed at non-ideal locations, cell crossing errors, and mass moving from one background grid cell to another. The same drawbacks lead to even worse consequences in the presence of an interstitial fluid phase, especially when undrained/incompressible conditions are approached. In this study, an explicit stabilised MPM, based on the Generalised Interpolation Material Point (GIMP) method with Selective Reduced Integration (SRI), is proposed to mitigate typical numerical oscillations in (nearly) incompressible coupled problems. It includes two additional features to improve stress and pore pressure recovery, namely (i) patch recovery of pore pressure increments based on a Moving Least Squares Approximation, and (ii) two-phase extension of the Composite Material Point Method for effective stress recovery. The combination of components leads to a new method named GC-SRI-patch. After a detailed description of the approach, its effectiveness is verified through analysing various consolidation problems, with emphasis on the representation of pore pressures in time and space. [ABSTRACT FROM AUTHOR]

• A comprehensive geological field investigation and analysis to discern the water-inrush mechanism in the deep tunnel is conducted. • The flow path and dynamic characteristics of high-pressure water inrush are clarified. • A novel method for predicting joint water inflow in the intricate hydrological environment is introduced. • A series of innovative karst water treatment schemes involving coordinated grouting are proposed. • The effectiveness of the proposed measures is evidenced by monitoring results and the successful operation of the tunnel, demonstrating significant positive outcomes. Geological hazards, particularly water inrush, pose frequent challenges in tunnel constructions within karst regions. Drawing from the engineering experiences in addressing multiple large-scale water inrush hazards in the Dejiang tunnel, a combined method of field investigation and theoretical analysis was employed for qualitative and quantitative analyses of water inrush mechanisms. The regional geological investigation highlighted the formation of strong and weak aquifers due to alternating weak limestone and mudstone in the synclinal strata, creating favorable conditions for large-scale karst conduit. Atmospheric precipitation water connects karst cavities through groundwater-eroded karst conduit, establishing a recharge system for water inrush hazards. Three empirical formulas are adopted to investigate the influence of rainfall on the tunnel's actual water inflow. Importantly, it was found that considering only the influence of rainfall or surface water cannot reasonably predict the inflow in this area. The disaster's primary causes are attributed to the heavy rainfall, karst conduit, underground river, and weak strata, which have contributed to the persistent nature of water inrush events. The principle of "drainage and blockage" was used to address the issue of water inrush. Proposed remediation strategies during construction, including the innovative membrane bag high-pressure grouting, have proved to be effective in addressing the connected karst conduits. The drainage and blockage effects were achieved by installing drainage pipes during the grouting reinforcement process. Finally, the water pressure-resistant structure was employed to enhance the stiffness of the lining. As validated by monitoring data, the measures serve as crucial methods to guarantee the safety of tunnel structures, effectively prevent water inrush and amplify the ecological benefits of water-rich areas. [ABSTRACT FROM AUTHOR]

The deterioration of groundwater seepage on the tunnel face stability is a principal risk for tunnelling through watery ground, and a thorough understanding of soil–water coupled large deformation behaviors is essential for effective disaster prevention. This study employs a three-dimensional (3D) coupled Material Point Method (MPM) to analyze the hydro-dynamical collapse characteristics of the tunnel face, particularly focusing on tunnel shields with partially filled chambers where the air pressure is utilized to support the upper portion of the tunnel face. Initially, the validity of the 3D coupled MPM is verified through comparing numerical and analytical results of a 1D consolidation problem, covering from small to large deformation analyses. Subsequently, the evolutionary characteristics of the tunnel face collapse and ground response are investigated through a series of large-scale simulations. Special attention is given to differentiate failure responses between saturated and dry sand, emphasizing the weakening effect of seepage flow on tunnel faces. Furthermore, the influence of different combinations of construction conditions and soil properties on the collapse process is also investigated. Numerical results validate the efficacy of the 3D coupled MPM in addressing hydro-dynamical tunnel face collapse issues, with goals of providing insights into associated disaster prevention and post-failure behavior prediction. [ABSTRACT FROM AUTHOR]

This study employs geopolymer as a complete replacement for the cement to solidify the shield muck discharged from tunneling in the silty clay layer, thereby creating an innovative synchronous grouting material. This novel grouting material not only utilizes geopolymer as its primary cementitious component but also incorporates shield muck, promoting the efficient utilization of the shield muck. The cementitious process of the grout is initiated by the principles of geopolymerization. Through a series of laboratory tests assessing grout performance, the new grouting material was developed by further optimizing the grout proportion using the response surface method (RSM). This involves a comprehensive analysis of the impacts of various factors such as muck moisture content, foam injection ratio, ground granulated blast furnace slag (GGBS) content, and sand content, along with their interactions on the key response variables, including consistency, fluidity, 2 h bleeding rate, setting time, and 3 d unconfined compressive strength (UCS). The optimal proportion of the new grouting material is found to be 140% muck moisture, 100% GGBS, and 230% sand. Experimental results reveal that the GGBS content has the most significant effect on various properties of the grout, while the interaction between these factors has distinct effects on different grout properties. This novel synchronous grouting material was subsequently employed in the Nanjing Metro Line 6 project, and it was found that both surface settlement and segment uplift meet the specified requirements. • Shield muck was used to create a novel synchronous grouting material via geopolymerization. • The effect of muck moisture content, foam injection ratio, and GGBS content on grouting performance is analyzed by RSM. • The impact of foams presented in the shield muck on the new synchronous grouting material was investigated. • A new synchronous grouting material was field-tested and its efficacy was validated. [ABSTRACT FROM AUTHOR]

Conventional grouting materials often exhibit shortcomings when faced with water rushing in karst strata, such as easy dispersion, poor stability, and uncontrollable diffusion. This study introduces an organic-inorganic hybrid water-swelling material for grouting based on excellent synergistic interactions among Polymethylene Polyphenyl Isocyanate (PAPI), Nitrogen tetroxide (N204), Portland cement, and Triethylenediamine (A33) using a straightforward process. Meanwhile, optimal formulations for the WSGM are determined using a proposed matrix analysis model. Under specific conditions with an alcohol ester ratio of 0.9, cement content of 50 %, and catalyst content of 50 %, the resulting water-swelling grouting material (WSGM) exhibits a three-dimensional network structure, high viscosity, exceptional stability, and robust scour resistance (with an initial expansion time of 11 s, a gel time of 91 s, a volume expansion rate of 600 %, a compressive strength of 0.62 MPa, and a bonding strength of 0.39 MPa). The excellent performance of the WSGM is validated through a series of experimental tests. The potential formation mechanisms were discussed, considering the hardening process, X-ray diffraction (XRD) analysis, and scanning electron microscopy (SEM) analysis. This research holds the potential to advance the development of organic-inorganic hybrid water-swelling materials with excellent performance, opening new avenues in material preparation. • An organic-inorganic hybrid water-swelling grouting material (WSGS) for karst strata is proposed. • A matrix analysis model for determining optimal formulations of the WSGS is presented. • Recommended formulations for the WSGS include an alcohol ester ratio of 0.9 with cement and catalyst each at 50 %. • Optimized WSGS formulations in laboratory model tests show superior grouting quality. [ABSTRACT FROM AUTHOR]

To address the hysteresis in assessing the workability of conditioned soils and the inefficiency in estimating the soil volume flow rate in tunnelling practice, a novel real-time assessment and monitoring approach was proposed. Based on laser scanning technology and point cloud data analysis, the approach can monitor the workability and the volume flow rate of conditioned soils on the horizontal conveyor belt of an earth pressure balance (EPB) shield in real-time. Firstly, the accuracy of laser scanning measurements was verified by comparing manually measured slump and spread values with laser scanning results. Then, a series of model tests for scanning the coarse-grained soils with different conditioning parameters and belt speeds on the horizontal conveyor belt were performed. The appropriate ranges of secant angle and unevenness of soil cross-sectional profile were obtained for assessing the workability of conditioned soils. The volume flow rate was calculated by integrating the cross-sectional areas of conditioned soils. Finally, the proposed approach was successfully applied in identifying the workability of conditioned soil and its discharge rate in the EPB shield tunnelling project. This study contributes to the real-time monitoring of conditioned soils on the horizontal conveyor belt and provides practical insights for the optimal management of EPB shield tunnelling. [ABSTRACT FROM AUTHOR]

Tunnelling-induced ground responses in coarse-grained soils often exhibit complex behaviours such as soil arching and progressive ground instability. However, the effect of particle size distributions (PSDs) on ground responses in tunnelling remains largely unexplored. This study provides new insights into PSD's effect on tunnelling ground response and the underlying mechanism based on granular skeleton quantification. The coarse-grained soils with 9 typical PSDs were modelled by the discrete element method (DEM) with varied granular skeleton structures. A representative volume element (RVE) assembly method, with a novel iteration-based specimen generation method, is developed to build ground models incorporating millions of soil grains, where an eccentric displacement boundary was embedded for reproducing the tunnel volume losses. The results demonstrated that the change in skeleton structures from fine-grains to coarse-grains dominated leads to the acceleration of soil arch emergence and the deceleration of soil arch collapse-rebuilding. With an increase in d ed , the strengthened soil arch leads to a more evident deformation localization in ground, and results in more significant hysteresis of ground instability from the tunnel to the surface. The effect of PSDs on ground responses becomes prominent as the overburden thickness decreases and the tunnel volume loss increases, and a decrease in d ed would increase the risk of overall failure in tunnelling. [ABSTRACT FROM AUTHOR]

This study presents an improved semi-implicit MPM formulation for coupled large deformation problems in geotechnics based on the fractional step method. The main objective of this study is to make the choice of the time step size independent of the permeability and to reduce the pressure oscillations by applying the special splitting procedure and the stabilized technique. The proposed coupled MPM is validated by comparing numerical results with analytical solutions of the one-dimensional consolidation problem in both small and large deformation regimes. Three numerical tests are performed to further evaluate the performance of the proposed method, including a self-weight slumping block, 2D consolidation test, and the stability of a saturated elasto-plastic slope. The numerical results indicate that the proposed method is suitable for simulating fluid-saturated porous media involving large deformation. [ABSTRACT FROM AUTHOR]

• A multi-output stacked model for simultaneously predicting TBM thrust and torque. • Combining three machine learning methods to select feature parameters for prediction model. • OPTUNA optimizer is used for hyperparameter optimization to improve model performance. • A stacking algorithm framework is proposed for integrating multiple basic models. • Multi-output regression prediction is promising for TBM operation parameters. Thrust and torque are two key operation parameters for tunnel boring machine (TBM), a rapid and accurate simultaneous prediction or determination of them is essential for TBM construction. In this study, based on the real dataset collected from the Chaoerhe River to Liaohe River project, a stacking algorithm framework is proposed for establishing a multi-output stacked prediction model for TBM thrust and torque. Such model is constructed by integrating the basic models including Random Forest (RF), XGBoost and CatBoost , Support Vector Regression (SVR), and Multilayer Perceptron Neural Network (MLPNN). Both Knowledge Driven and Data Driven approaches were employed to select feature parameters, and the importance of these parameters was analyzed in combination with the RF , XGBoost , and CatBoost algorithms. Meanwhile, the OPTUNA optimizer and Non-dominated Sorting Genetic Algorithms III (NSGA-III) were used for hyperparameters optimization of models. The results indicate that the multi-output stacked prediction model outperforms the any of single basic models, with corresponding aCC , aRMSE and aRRMSE are 0.9524, 376.30 and 1.3260, respectively. Moreover, the method of multi-output prediction has about 5.8 times efficiency higher than the single-output prediction. The proposed framework provides an efficient, accurate, and promising method for the simultaneous prediction of multiple operation parameters of TBM. [ABSTRACT FROM AUTHOR]

This study investigates the stability of dual unlined elliptical tunnels in cohesive-frictional soils using upper-bound finite element methods with rigid translatory moving elements (UBFEM-RTME). Results are determined in terms of dimensionless stability numbers, which increase with ϕ and decrease with increasing B / D and C / D , and collapse mechanisms, which mainly include two wedge-shaped zones and a complete non-plastic wedge. The center-to-center distance S significantly affects the stability of dual tunnels, and the interaction between the elliptical tunnels tends to disappear when S c lies within (i) 2.5 D -4 D for C / D = 1, and (ii) 4 D -11 D for C / D = 5. The results agree well with those in literature. [ABSTRACT FROM AUTHOR]

The stability of an unlined elliptical tunnel in cohesive-frictional soils is determined. The analysis has been performed with two methods: finite element upper-bound method with plastic deformation elements (UP-PDE) and finite element upper-bound method with rigid translatory moving elements (UP-RTME). UP-PDE has been used to study tunnel stability by many scholars. The UP-RTME in combination with a finite element approach and triangular rigid translator moving elements is presented in detail. In the proposed method, the node coordinates and velocities of rigid elements are treated as unknowns without considering the rotating freedom. A specific plane strain formulation is proposed using nonlinear programming, and the optimal slip lines are determined by automatically adjusting the velocity discontinuities. Solutions for the influence of a range of soil parameters, dimensionless depths C / D and dimensionless spans B / D on the stability numbers γD / c and collapse mechanisms are solved using this method. The γD / c values increase with ϕ and decrease with C / D and B / D . γD / c is less sensitive to C / D as ϕ increases. The collapse mechanisms of unlined elliptical tunnels comprising two groups of slip lines are also presented, and they explicitly reflect the relative movement of blocks. The results show that these two methods are in agreement with each other. [ABSTRACT FROM AUTHOR]