Large Soil Deformations Research Articles

A Numerical Investigation on the Sinkage of the Deep-Sea Mining Vehicle Based on a Modified Constitutive Soil Model

Abstract The seabed soil of the polymetallic nodule mining area is relatively thin, soft, and fluid, which will produce large deformation under external disturbance. Its undrained shear strength is related to strain-rate and strain-softening effect. It is an important engineering safety problem for the deep-sea mining vehicle (DSMV) to travel in the soft seabed, and its sinkage is a vital index affecting the traction performance. It is necessary to study the sinkage performance of the DSMV under the characteristics of large soil deformation, but there are only few existing studies. This study established a numerical model of seabed soft soil with Tresca constitutive considering strain-rate and strain-softening effects. First, a numerical simulation study was carried out on the interaction between the DSMV track plate and the seabed soil, and the influence of track plate structures on the pressure–sinkage characteristic was obtained. Then, a simplified three-dimensional model of the “PIONEER-I” DSMV was established. Under the condition of wet weight and initial vertical velocity, the influence of different initial bottoming velocities, weight, and soil parameters on the sinkage of the DSMV was obtained. An empirical prediction model of the DSMV sinkage was established based on the energy method and numerical calculation results.

Analysis of r - Adaptive coupling adaptive time integration strategy in FEM of seismic liquefaction

In seismic finite element analysis of saturated soils, the challenges primarily reside in liquefaction and the large deformation of soil induced by strong earthquakes. Traditional updated Lagrangian methods may result in severe mesh distortion after updating the spatial configuration of nodes. To address this issue, this study develops an r - adaptive approach based on a solid - fluid coupling finite element method (FEM) platform to mitigate mesh distortion problems. This technique optimizes mesh nodes without altering the overall topology, thereby maintaining mesh integrity. However, enhancing mesh accuracy comes at the expense of increased computational costs. To alleviate high computational expenses, this study couples two types of adaptive time stepping techniques, based on mixed error and displacement history curvature, with mesh adaptation. Through verification on two typical dynamic liquefaction models of saturated soil on embankment and subway station, this technique effectively balances the relationship between computational accuracy and costs.

Simulation of controlled modulus column installation using a large deformation finite element analysis

Controlled modulus columns (CMC) are widely used in ground improvement techniques where grout columns are constructed by penetrating an auger into the ground using the displacement approach. Numerical simulation of this problem is challenging owing to the large soil deformations associated with installation. Small strain-based finite element analysis procedures available in commercial finite element modeling software are unsuitable for simulating this problem because they cannot simulate large soil deformations around the auger during column installation. Hence, this study presents a numerical approach based on the finite element method to simulate the installation of CMCs. The numerical modeling technique adopted in this study considers large soil deformations around columns during penetration, and the proposed approach is based on remeshing and interpolation techniques. This method was developed using the Python development environment (PDE) within the ABAQUS/standard finite element program. It can penetrate columns below the ground surface without causing large mesh distortions. In this study, silty sand-type soil was considered; hence, the constitutive behavior was simulated using the Mohr–Coulomb criteria. The load-carrying capacity of a controlled modulus column was predicted and compared with an empirical equation based on the cone penetration resistance. The influence zone and failure mechanism of the soil during installation were determined by considering the stress distribution and soil flow pattern around the column.

Inrushing failure characteristics of deep shaft structures in soft soils based on material point method simulation

In areas with soft soil, inrushing may occur during the construction of deep shaft structures under high water pressures, causing destructive accidents. Most studies on inrushing have used the finite element method. However, it is difficult to achieve a large deformation simulation because of mesh limitations. The material point method is not constrained by the mesh, and the material properties and motion information of the material are stored at the material points. Therefore, it can be used to effectively simulate large soil deformations. In this study, a numerical model for a deep shaft structure in Shanghai was formulated using the material point method to simulate the evolution of inrushing failure. The likelihood of inrushing damage at different excavation depths was analyzed. Soil heave at the bottom of the pit in the absence of inrushing was examined. The structural and environmental factors affecting the inrushing process are discussed. Strategies have been proposed from different perspectives, such as structure, environment, and construction methods, to reduce the damage caused by inrushing, thereby providing a reference for the safer construction of deep shaft structures.

Evolution of mechanical properties of shield tunnels induced by water-soil gushing

Water-soil gushing in shield tunnels has been a major threat to the safety of tunnel structures. However, traditional numerical methods cannot reasonably simulate large soil deformation around the tunnel caused by the water-soil gushing. Therefore, it is difficult to reveal the evolution of the internal force and deformation of tunnel structures. In this paper, based on the two-phase Material Point Method, the numerical analysis method for the water-soil gushing was established to investigate the development of water-soil pressure acting on the tunnel surface, and then the evolution of the tunnel mechanical behaviours in the process of tunnel gushing was further studied. The results indicate that during the “rapid gushing stage”, the tunnel surface pressures around the leakage point decrease sharply, whereas those on the tunnel invert increase significantly. This gives rise to a significant increase in the shear force and bending moment of the tunnel lining, with increase rates of 114% and 82%, respectively. In addition, the axial and angular deformation of Joint No.2 near the leakage point increased significantly, which may lead to serious longitudinal joint dislocation or even concrete crushing. Thus, close attention to the joint deformation is required.

Study on large deformation of soil–rock mixed slope based on GPU accelerated material point method

This study assesses the effect of stone content on the stability of soil–rock mixture slopes and the dynamics of ensuing large displacement landslides using a material point strength reduction method. This method evaluates structural stability by incrementally decreasing material strength parameters. The author created four distinct soil–rock mixture slope models with varying stone contents yet consistent stone size distributions through digital image processing. The initial conditions were established by linearly ramping up the gravity in fixed proportionate steps until the full value was attained. Stability was monitored until a sudden shift in displacement marked the onset of instability. Upon destabilization, the author employed the material point method to reconstruct the landslide dynamics. Due to the substantial computational requirements, the author developed a high-performance GPU-based framework for the material point method, prioritizing the parallelization of the MPM algorithm and the optimization of data structures and memory allocation to exploit GPU parallel processing capabilities. Our results demonstrate a clear positive correlation between stone content and slope stability; increasing stone content from 10 to 20% improved the safety factor from 1.9 to 2.4, and further increments to 30% and 40% ensured comprehensive stability. This study not only sheds light on slope stability and the mechanics of landslides but also underscores the effectiveness of GPU-accelerated methods in handling complex geotechnical simulations.

A frictional contact algorithm in smoothed particle method with application in large deformation of soils

A frictional contact algorithm in smoothed particle method with application in large deformation of soils

Numerical implementation of the hypoplastic model for SPH analysis of soil structure development in extremely large deformation

The extremely large deformation of soil is a significant challenge due to the dynamic changes in soil structure, but it is poorly understood owing to inadequate effective numerical methods. This paper presents a numerical method for analysing the responses of sand-like granular soil undergoing extremely large deformation. The proposed method utilizes the Smoothed Particle Hydrodynamics (SPH) technique, which is a meshfree particle-based approach capable of circumventing the computational difficulties associated with mesh distortion. The Gudehus-Bauer (G-B) hypoplastic model, which can capture the pressure- and density- dependent mechanical behaviour of granular soil, is implemented into the in-house developed SPH code. Concerning the characteristics of large deformation, the Green-Naghdi rate is applied in this study to achieve objective stress integration. An adaptive explicit stress integration scheme, termed Modified Euler automatic Substepping with Error Control (M-E-SEC) is utilized to handle the time integration of the SPH equation system. Additionally, a stability correction method is introduced to suppress the breakdown problem that occurs at low-stress states. The effectiveness of the proposed method is validated by experimental data. Furthermore, several numerical examples are presented to elucidate the evolution of shear band structures in granular soils subject to extremely large deformation levels.

Multicore CPU-based parallel computing accelerated digital image correlation for large soil deformations measurement

This paper presents a new approach for measuring large deformations in geotechnical experiments employing digital image correlation (DIC) or particle image velocity (PIV) techniques. The proposed method is based on the Eulerian analysis scheme, allowing for the application of multicore central processing unit (CPU)-based parallel computing to expedite the processing of experimental images. The displacement increments obtained through DIC analysis on the Eulerian mesh nodes (subset centers) are then mapped onto tracer particles (TPs), which are assigned by users to track material movement. Finally, accumulated displacements and strains are determined on these TPs. Two example applications are presented to showcase the capabilities of the proposed method: a centrifuge half model test of flat circular footing penetrating sand overlying clay and a full transparent soil model test (TMST) of conical pile penetration. A comparison with other standard first-order deformation algorithms and the Lagrangian analysis scheme demonstrates that the presented method offers comparable precision but significantly faster computation speed, with an improvement of over six times when processing a considerable number of (e.g. over 20) images. This enhanced computational speed can greatly reduce the time required for image post-processing. The proposed method is particularly suitable for large deformation experiments that involve the analysis of numerous images and require high precision.

Micromechanical analysis of the suction bucket-granular soil interactions under the pull action of anchor lines: Embedded length effect

The micro-mechanism of interactions between suction buckets and granular soil under different embedded lengths remains unclear. This study investigates the micro-to-macro interactions between suction buckets and granular soil under an inclined pull action of anchor lines, taking the embedded length effect into consideration. The granular soil was modeled using the discrete element method (DEM), while the suction bucket was modeled using the finite element method (FEM). The peak pull force in DEM-FEM simulations was validated using model test results, while macro and micro behaviors of the structure-soil interaction were analyzed. The findings demonstrated that the embedded length effect shaped the pull force-displacement curve by influencing the interaction modes between structures and granular soil. Discontinuity and large soil deformation occurrences can be successfully simulated using the DEM-FEM method and the relationships to embedded lengths were discovered. Besides, clear relationships among bucket rotation angles, the effective supporting areas, vertical pull-out displacement, shear wear, and deformation of buckets, were established. Furthermore, a detailed investigation of particle-scale behaviors led to an identification of mechanical failure modes of suction bucket-granular soil interaction. The findings suggest that ignoring the embedded length effect could lead to misestimating the uplift capacity and failure modes of the suction buckets.

Numerical analysis of the post-installation consolidated response of skirted foundations

The effect of the installation process on the subsequent foundation consolidation response requires assessment when the preload is initially applied. In the framework of effective stress, the influence of large soil deformations during penetration is analysed in this study using a comparison of results from large deformation finite element (LDFE) analysis based on periodic mesh regeneration (Ritss technique) and a 'wished-in-place' small strain finite element (SSFE) model. The LDFE results demonstrate that considerations of the skirt penetration and soil plug bulge lead to different soil excess pore pressure and void ratio change distributions from that of the SSFE analysis, thereby affecting the foundation settlement and consolidated bearing capacity. The normalised fully consolidated undrained bearing capacity grows linearly with the preload ratio for preloads higher than the penetration resistance, and the capacity obtained from the LDFE is higher. The settlement ratio and the proportion of partially consolidated to fully consolidated capacity gain can be represented as a hyperbolic function of a revised dimensionless time factor. The methods integrated in this study can be used to predict the increase in the vertical undrained capacity of skirted foundations after consolidation, accounting for installation effects in engineering practice.

Modeling Dynamics of Laterally Impacted Piles in Gravel Using Erosion Method

Understanding the dynamic interaction between piles and the surrounding soil under vehicular impacts is essential for effectively designing and optimizing soil-embedded vehicle barrier systems. The complex behavior of pile–soil systems under impact loading, attributed to the soil’s nonlinear behavior and large deformation experienced by both components, presents significant simulation challenges. Popular computation techniques, such as the updated Lagrangian finite element method (UL-FEM), encounter difficulties in scenarios marked by large soil deformation, e.g., impacts involving rigid piles. While mesh-free particle and discrete element methods offer another option, their computational demands for field-scale pile–soil impact simulations are considerable. We introduce the erosion method to bridge this gap by integrating UL-FEM with an erosion algorithm for simulating large soil deformations during vehicular impacts. Validation against established physical impact tests confirmed the method’s effectiveness for flexible and rigid pile failure mechanisms. Additionally, this method was used to examine the effects of soil mesh density, soil domain sizes, and boundary conditions on the dynamic impact response of pile–soil systems. Our findings provide guidelines for optimal soil domain size, mesh density, and boundary conditions. This investigation sets the stage for improved, computationally efficient techniques for the pile–soil impact problem, leading to better pile designs for vehicular impacts.

Analysis of bucket foundation installation in clay considering soil large deformation

Bucket foundations are increasingly used to support offshore wind turbines. Its bearing performance has been extensively investigated, but its installation process has been addressed in a few investigations. This study investigates the penetration resistance during the installation of bucket foundations in clay through finite element models that consider large soil deformations. The proper finite element modeling scheme is assessed first, then a validated numerical model is employed to investigate the effects of length-diameter ratio and soil properties on the soil plug and penetration resistance. The results indicate that a minimum element dimension and penetration velocity should be set to 1/6th of skirt thickness and 0.3 m/s to ensure a good balance between computational accuracy and efficiency. An increase in the bucket length-to-diameter ratio increases the height of soil heave, while soil nonuniformity reduces it. In addition, the height of soil heave is slightly influenced by the friction coefficient and undrained shear strength of the soil. On the other hand, the penetration resistance is strongly affected by the soil undrained shear strength and bucket length-diameter ratio, but slightly affected by the friction coefficient.

Micromechanical analysis of suction pile-granular soil interaction under inclined pulling load of mooring line: Mooring depth effect

The micro-mechanism of mooing depth effect on the interactions between suction piles and granular soil remains unclear. This study investigates suction pile-soil interaction behaviour under the inclined pulling load of a mooring line, as well as mooring depth effects. The discrete element method (DEM) was used to model granular soil, while the suction pile was modelled via finite element method (FEM). Results in DEM-FEM simulations were compared with that in the model tests first. Then, the macro and micro behaviours during suction pile-soil interactions were analysed. Based on the results, the pulling force-displacement curves could be categorised into two groups according to the curve shapes associated with suction pile motion patterns. Discontinuity and occurrences of large soil deformation were successfully reproduced. Next, suction pile movement and deformation were quantitatively analysed in terms of vertical pull-out displacement, pile rotation, and effective support around suction piles. Furthermore, the particle-scale behaviours of soil were analysed, finishing with the identification of conclusive mechanical failure patterns. This study indicates that neglecting the mooring depth of the mooring lines may lead to a significant underestimation of the uplift capacity of a suction pile, as well as misinterpretation of the failure mode of the granular soil.

Numerical modelling of sand plug formation during punch-through of a spudcan footing

Jack-up vessels are widely used within the offshore industry both to service oil and gas platforms, and more recently also for installation of wind turbine generators and their foundations. When a jack-up vessel jacks next to an existing structure, the soil displacements induced by penetration of the spudcan footings of the jack-up may lead to loading and deformation of the structure. In order to assess this loading, an accurate understanding of the flow of soil around the penetrating spudcan is required. Spudcan penetration in layered soils provides additional complexity compared to uniform ground conditions. This paper focuses on the case of sand overlaying clay, where a sand plug can form under the spudcan base during punch-through. The bearing pressure of the spudcan and deformation patterns in the soil adjacent to the spudcan are modelled in a finite element model using Plaxis 2D with updated mesh formulation to allow for the modelling of large soil deformations. The results are found to provide a reasonable match with displacement measurements from centrifuge tests, albeit with larger difference for derived bearing pressure. Hence, the developed model can be used to model soil displacements induced by spudcan loading in an accurate and computationally efficient manner.

Micromechanical analysis of suction bucket-granular soil interaction under eccentric pulling action of mooring lines: Effect of horizontal pulling angle

Previous suction bucket-soil interaction simulations usually apply fixed loads on suction buckets as the action of mooring lines, ignoring the contact behaviors between mooring lines and suction buckets. This study investigates suction bucket-soil interaction under the above contact behaviors with the horizontal pulling angle effect. Granular soil was generated in the DEM part while the suction buckets were simulated with meshes in the FEM part. The pulling action of mooring lines was applied by a hanger that can slide and rotate at the contact point. The micro-to-macro results revealed that the shape difference in pulling force-displacement curves can be explained by the effect of decomposed pulling actions on soil behaviors. Besides, the horizontal pulling angle effect on discontinuity and occurrences of large soil deformation can be successfully modeled by the coupled DEM-FEM method. Meanwhile, the horizontal pulling angle effect associated with different interface frictions on the movement and deformation of suction buckets were discovered. Furthermore, conclusive failure patterns of suction bucket-soil interaction were identified after analyzing particle-scale soil behaviors. The study indicates that neglecting the horizontal pulling angle of the mooring lines could result in severely misestimating the uplift capacity of a suction bucket and the soil failure pattern.

DEM study of particle scale effect on plain and rotary jacked pile behaviour in granular materials

The capacity of open-ended piles strongly depends on the potential plugging occurring during installation. The Discrete Element Method (DEM) is particularly suitable to the study of pile plugging, as it can model large soil deformation. However, DEM simulation of the 3D boundary value problems is computationally expensive, and particle upscaling is usually used to reduce the number of particles modelled. In this paper, two granular beds were created with the same average porosity, initial stress field and contact parameters, but different particle scales. Two pile geometries were installed by plain and rotary jacking. Normalised results show that the pile penetration mechanism is strongly affected by the particle scale. Larger particles lead to earlier pile plugging, higher shaft resistance and require a greater force to penetrate the ground. This effect can be linked to a modified penetration mechanism, with larger shear zones and less well defined “nose cone” under the pile tip for larger particles. Changing particle scaling has a neutral effect on the total penetration resistance of a rotary jacked pile, but reduces the base penetration and increases the plug resistance. Maximising the ratio of particle scale to wall thickness is key to adequately capturing the pile coring mechanism.

Two-layer two-phase material point method simulation of granular landslides and generated tsunami waves

Numerical modeling of the entire process of tsunamis generation by granular landslides is very difficult and challenging as it involves the soil–water interaction, large deformation of soil, and the fluidization and sedimentation of sand. In this study, a computational model based on the two-layer two-phase material point method (MPM) is developed to simulate granular-landslide-generated tsunamis, wherein the soil–water interaction, large deformation of soil, and fluidization and sedimentation of sand are well modeled. The soil behavior is described using a Mohr–Coulomb model with a non-associated flow rule, while the water is considered as weakly compressible. Furthermore, three different benchmark problems are simulated. All computed results well agree with the corresponding analytical solution and laboratory test data, verifying the effectiveness of the proposed two-layer two-phase MPM for modeling the subaerial and submerged granular-landslide-generated tsunamis. Additionally, the influence of different soil material parameters on the water wave generated by the subaerial granular landslide is investigated.

Data Analysis of the Effect of Different Nanomaterials on Antislide Pile Performance in Railway Landslides

Engineering geological conditions in our country are complex and diverse. Many high-rise buildings, bridges, and launch towers are inevitably built on high and steep slopes. Heavy rain, earthquake, human engineering activities, and other factors lead to frequent landslides, soil creep deformation, and overall sliding, resulting in a certain bending moment and flexural deformation of foundation piles, may cause damage to the substructure and foundation pile failure, and then endanger the safety of the superstructure. In the past, bridge pile group foundation was used in bridge pile foundation engineering to improve the impact situation, but the stress environment of bridge pile foundation in landslide is obviously different from that of bridge pile foundation in the flat area. The large deformation of soil in front of the pile will easily cause the phenomenon of soil sliding and peeling, which will increase the technical difficulty of antislide pile construction. Based on this, this study firstly briefly introduces the relevant theories and technologies of railway landslide antislide pile technology and then establishes the static model of railway landslide antislide piles with different nanomaterials. Finally, the reinforcement technology of different nanomaterial antislide piles for railway landslide is expounded, which can provide guarantee for the application of different nanomaterial antislide piles for railway landslide. The results show that the preloading is carried out according to 1/10 of the design load to reduce the void between the soils. After the load is maintained for 2 hours, the load is unloaded to 0, and good skid resistance can be obtained.

Two-Phase Two-Layer Depth-Integrated SPH-FD Model: Application to Lahars and Debris Flows

The complex nature of debris flows suggests that the pore-water pressure evolution and dewatering of a flowing mass caused by the high permeability of soil or terrain could play an essential role in the dynamics behavior of fast landslides. Dewatering causes desaturation, reducing the pore-water pressure and improving the shear strength of liquefied soils. A new approach to landslide propagation modeling considering the dewatering of a mass debris flow has drawn research attention. The problem is characterized by a transition from saturated to unsaturated soil. This paper aims to address this scientific gap. A depth-integrated model was developed to analyze the dewatering of landslides, in which, desaturation plays an important role in the dynamics behavior of the propagation. This study adopted an SPH numerical method to model landslide propagation consisting of pore-water and a soil skeleton in fully or partially saturated soils. In a two-phase model, the soil–water mixture was discretized and represented by two sets of SPH nodes carrying all field variables, such as velocity, displacement, and basal pore-water pressure. The pore-water was described by an additional set of balance equations to take into account its velocity. In the developed two-layer model, an upper desaturated layer and a lower saturated layer were considered to enhance the description of dewatering. This is the so-called two-phase two-layer formulation, which is capable of simulating the entire process of landslides propagation, including the large deformation of soils and corresponding pore-water pressure evolutions, where the effect of the dewatering in saturated soils is also taken into account. A dam-break problem was analyzed through the new and previously developed model. A flume test performed at Trondheim was also used to validate the proposed model by comparing the numerical results with measurements obtained from the experiment. Finally, the model was applied to simulate a real case lahar, which is an appropriate benchmark case used to examine the applicability of the developed model. The simulation results demonstrated that taking into account the effects of dewatering and the vital parameter of relative height is essential for the landslide propagation modeling of a desaturated flowing mass.