Computers and Geotechnics最新文献

A thorough understanding and treatment of wave-structure interaction (WSI) mechanics is essential for the rigorous engineering design of coastal protections. Conventional numerical analysis methods are accurate and generalize well, but are heavily dependent on the adopted mesh resolution and frequently incur substantial computational costs. To bypass these limitations, a meshless multi-fidelity residual neural network (MRNN) emulator is introduced in this study to infer the spatio-temporal responses arising from WSI. MRNN first employs a ‘low-fidelity’ simulator to learn basic WSI relationships by training on simulations obtained using a coarse numerical mesh. Subsequently, a ‘high-fidelity’ (HF) simulator is then employed to learn the mapping between numerical simulations performed using the coarse mesh and additional detailed fine meshes. The results indicate that MRNN is a highly robust emulator which requires significantly less HF data through its hierarchical framework compared to conventional single-fidelity data-driven strategies. By way of example, the MRNN emulator is applied to the cases of a porous dam break and breakwater. A broad spectrum of WSI responses, such as water through the porous dam medium, can be accurately captured using the MRNN emulator which is benchmarked against a conventional numerical modelling with a fine mesh. The computational efficiency of the MRNN is shown to be independent of the mesh resolution and complexity of the studied partial differential equations. It provides a generic and utilitarian emulator for any engineering problem of interest.

To energizing implementation of “Carbon Peaking and Carbon Neutrality” strategy, a batch of pumped storage power stations represented by asphalt concrete panel dams have been planned in China. The safety assessment of the anti-seepage system is crucial to engineering construction. In this paper, a cross-scale approach and SBFEM are employed to investigate the deformation characteristics of a typical dam under various conditions, combining the generalized plastic model. The location of the weak area in the anti-seepage system is identified. Subsequently, a fresh step-type design is proposed based on simulations, aiming to enhance the stability performance of anti-seepage joint. The mechanism and influence of the step-type scheme are discussed from different perspectives through simulations. The research indicates that the asphalt panel slides along the underlying lapped concrete platform due to the uneven settlement between rockfill and concrete. Resulting in significant horizontal tensile strain at the top of the asphalt panel. The step-type design provides a positive reinforcement effect, significantly reducing slipping displacements along the interface and the tensile strain of the asphalt panel by hindering the slip path of the rockfill. An optimal range for the step-type design is recommended to be between 0.375 m and 0.45 m below the junction point. Additionally, a height of 0.45 m is suggested for the single-step form, while a height of 0.075 m is recommended for each step in the multiple-step form. For multiple steps, performance improves as the spacing between the steps increases. The adaptability of the panel to deformation is enhanced through the presented method, enhancing the safety margin of the anti-seepage system and offering guidance for similar projects.

The block-in-matrix rocks (bimrocks) are a complex type of rock in which hard blocks are bonded in a weak matrix. Despite the widespread distribution of bimrocks in nature, they are usually ignored in the design and analysis stages, resulting in underestimation or overestimating critical design parameters. Moreover, in studies regarding the failure behaviour of the bimrocks, strain rate has been ignored and no study has focused on the influence of strain rate on the failure mechanism of bimrocks. Therefore, this study aims to numerically study the impact of the strain rate increase on the bimrock rectangular specimens with different volumetric bloc proportions (VBP). The combined finite-discrete element method (FDEM) is employed as the numerical tool to analyze the study objectives. FDEM has proved to be a suitable candidate, having extraordinary capabilities in modeling fracture development in brittle rock under complex loading types. Before the analysis of the bimrocks, a verification example is explained to demonstrate the capability of this method in modeling an existing problem. Six strain rates of 0.046/s, 0.092/s, 0.18/s, 0.74/s, 1.85/s, and 5.55/s are the considered strain rates chosen according to a detailed literature search. This study first discusses the influence of the strain rate on the response of the intact specimens composed of pure matrix or pure block properties. Then, four VBP of 25%, 50%, 75%, and 90% are numerically built and put under the chosen strain rates. The simulation results show that the strain rate considerably impacts the failure pattern, peak stress, and post-peak behavior of the bimrocks. Notably, it is observed that the low to medium strain rate (0.046/s, 0.092/s, 0.18/s s) have a similar influence on the failure of the bimrocks, while the loadings higher than these amounts cause complex failure (mainly multiple fracturing or axial splitting) and rapid increase in the peak stress. Furthermore, these observations are somehow similar in the bimrocks having a VBP of equal or less than 75%. The bimrock with a VBP of 90% behaves differently, and the rate of change in loading has a minor influence on the failure type (all are of axial splitting). Also, the change in the rate of loading also has a slight impact on the peak stress, and this parameter is observed to have a little change even under the very high strain rate of 5.55/s.

The significance of various unloading conditions on the strength and deformation characteristics of transverse isotropic rocks cannot be overstated. In this paper, we utilized a discrete element numerical method to simulate unloading pressures on composite rocks featuring laminated dips of 0°, 30°, 45°, 60°, and 90°. We analyzed the effects of various initial confining pressures, degrees of initial damage, and unloading rates on the strength and deformation of these composite rocks. Real-time acoustic emission event monitoring was conducted on the composite rocks, and we investigated the internal damage deterioration mechanism under different unloading conditions based on the moment tensor theory. The findings indicated that the peak strength of all dipping composite rocks exhibited a positive correlation with the initial envelope pressure and a negative correlation with the unloading rate. Moreover, the strains including axial, lateral and volumetric demonstrated an increase with initial confining pressure and initial damage, while they decreased with the unloading rate. The final damage of the composite rock, quantified by the number of cracks, displayed a positive correlation with the initial confining pressure and initial damage, and a negative correlation with the unloading rate. Analysis of the moment tensor of acoustic emission events for each isotropy/deviation ratio revealed that the number of acoustic emission events associated with compression-dominated failure increased proportionally with increasing confining pressure, while the number of acoustic radiation events linked with tensile damage decreased. Furthermore, with the increase in the unloading rate, shear-dominated acoustic emission events escalated while compression-dominated acoustic radiation events decreased.

Permeable pipe piles accelerate the bearing capacity of the pile foundation by releasing the excess pore water pressure (EPWP) of the soil around the pile through appropriate openings in the pile body. This study couples the Material Point Method (MPM) and the Finite Element Method (FEM) to establish a full-process model of pile driving and consolidation of permeable piles, and proposes a continuous drainage boundary condition that can reflect the plugging effect of permeable holes. The correctness of the model and boundary conditions are verified by comparison with experiments, and then the effects of soil properties, opening characteristics, and boundary permeability on the accelerated consolidation effect of permeable piles are analyzed. The results show that: the permeable pile with a permeable area ratio greater than 50% and a local opening ratio greater than 5% can save more than 60% of the consolidation time compared to conventional piles; the proposed boundary conditions can accurately describe the permeability of the permeable hole under the influence of plugging; in addition, the calculation formulae for the accelerated consolidation effect of permeable piles and the variation of continuous drainage boundary interface parameters with permeable area ratio are given, which can provide references for engineering design.

For the box-jacking constructions with an extra large rectangular tunnel profile, they tend to face a challenge in efficiently tunneling and precisely regulating tunneling attitudes. So far, few investigations or technical experience can rise to this challenge. For this, based on Shasan project that employs a box-jacking machine featuring in the largest rectangular tunnel profile in the world, the study intends to find out an effective way to enhance tunneling efficiency and regulate tunneling attitudes through revolving patterns of cutterheads. Two classes of revolving patterns of cutterheads are thus designed, one is bilateral inconsistency of cutting velocities, and the other is cutting direction consistent or reverse on upper and lower tunneling faces. Via the approach coupling Discrete Element Method (DEM) to Finite Element Method (FEM), mechanical responses of soil and the machine during dynamic tunneling are obtained. Based on data obtained from the project, the numerical model proves valid for further parametric investigations. Grounded in numerical results, a linear correlation between revolving patterns of cutterheads and moments of machine is figured out, and their interaction mechanisms are revealed. Some suggestions for preventing muck from stagnation and for design of the machine are offered to coming practical engineering.

This paper deals with the wetting-induced instabilities that can occur in unsaturated shallow slopes and cause the evolution of slides into flowslides. In particular, it examines the instability phenomena that manifest in the unsaturated regime prior to shear failure, focusing on the triggering mechanism and predisposing factors. A theoretical index to capture instability initiation is derived in a general form that is valid for all single-surface isotropic hardening plasticity models, regardless of the assumption on the flow rule and the type of perturbation applied. The criterion is then specialised to the case of the WR2-Unsat model and used to monitor the stability of a soil element belonging to an ideal infinite slope during wetting processes. The results of the parametric study suggest that particular attention should be paid to relatively steep slopes with a shallow cover of no more than a couple of metres, consisting of highly collapsible and/or compressible coarse-grained soils with a low fine fraction susceptible to liquefaction.

The elasticity law is a great challenge in soils, due to the well-known non-linear, anisotropic, pressure-dependent soil response even at negligibly small strains. A new hyper-elastic formulation is proposed, based on a polynomial expression (including a fabric tensor defining the elastic anisotropy) with two branches, one for the negligibly small stresses, ensuring good convergence properties at low confining pressure, and one for the soil response at intermediate strains, corresponding to stress states inside a single large-sized, yield surface defining the occurrence of large irreversible strain. Typical numerical simulations are discussed for isotropic and oedometric compression and swelling tests, and for undrained triaxial compression tests. The results are compared with those obtained with similar hyper-elastic models proposed in the literature. A comparison with experimental oedometric and drained and undrained triaxial tests on undisturbed samples of London clay is provided, revealing that the proposed model has great flexibility in selecting both the shear stiffness and the evolution of elastic anisotropy, which can be chosen independently, thus providing a general applicability. For instance, the great flexibility of the proposed hyper-elastic formulation can be exploited to model the non-linear swelling curves typically observed in oedometric swelling tests of structured clays or active clays.

Structured soft clay is characterised by high sensitivity and compressibility and accumulates excessive deformation under long-term dynamic loads, e.g., traffic loads, which likely threatens the service performance of overlying structures. In this work, to model the long-term mechanical behaviour of structured soft clay and efficiently capture its structural degradation, a new constitutive model was developed. The structural properties of soft clay, i.e., high yield strength and cohesive strength, were considered by a proposed yield surface, with their evolutions related to the combined plastic volumetric and deviatoric strains. The cyclic response of clay to undrained conditions was described through bounding surface theory. Moreover, the influence of the loading frequency on the dynamic response of clay was incorporated into the plastic modulus, and the softening effect caused by the generated excess pore water pressure (EPWP) was described by the shrinkable yield surface. Model validation was then carried out by reproducing both the accumulated strains and EPWPs of five types of reconstituted and structured soft clay. The acceptable consistency between the simulated results and experimental data and the independent and physical meaning of the featured model parameters confirmed the efficiency of the proposed model. More importantly, the evolution of the structural internal variables $S_i$ and $p_t^{\prime }$ with the development of plastic strains effectively represented the structural destruction process of soft clay under long-term cyclic loading conditions.