Pipe-piles are installed using impact or vibratory driving which influences the soil in different ways including the void ratio and stress distribution. Such complex problems are hard to investigate ...on the field as well as using numerical methods. Here, a sophisticated numerical approach is employed to evaluate the soil behavior during pile installation. Also, a sensitivity analysis on the frequency and the impact duration is done for vibratory and impact driving, respectively. The investigation includes the required force of the pile installation, pile penetration behavior, plugging formation inside the pile, and the change of the soil state including the change in the horizontal stress and density around the pile during the installation. Results of the numerical model show several advantages of vibratory driving over impact driving in the dense sand including, reaching the designated depth using less momentum and work as well as more soil compaction.
•An advanced numerical method, Multi-Material Arbitrary Lagrangian Eulerian (MMALE) with the hypoplastic material model.•The numerical model is validated against pipe-pile installation tests.•An analysis on the effects of change in frequency during vibratory driving, and impact duration during impact driving.•The momentum of total applied force-time curve of driving is used to compare between vibratory and impact driving methods.•Several possible advantages of vibratory driving over impact driving are presented.
Dynamic soil-structure interaction (SSI) is an important field in civil engineering with applications in earthquake engineering, structural dynamics, and structural health monitoring (SHM). There is ...an ongoing need for the development of numerical methods that can accurately estimate SSI parameters to model these systems. In this paper, a Frequency Response Function (FRF)-based model updating method is developed that can estimate the embedded length of foundation piles, in addition to the mobilized soil mass and stiffness, when a lateral impact load is applied. Knowledge of the embedded length of piles is very important for modelling foundation behaviour, and may not be readily available from as-built construction information. For example, if developing reference damage models or digital twins of foundation structures, full knowledge of the pile geometry is required. The work in this paper develops a two-stage iterative model updating method, which utilizes FRF data obtained at the pile’s head as a result of an applied lateral impact load. The method uses information from the 1st mode of vibration to estimate the mobilised soil mass and stiffness, and subsequently uses information from the 2nd mode of vibration to estimate the embedded length. To appraise the approach, impact tests are numerically simulated on a number of ‘piles’ (numerical spring-beam systems) with varying length/diameter (L/D) ratios to derive FRFs, whereby the models have known length and dynamic properties. These FRFs are then used as targets in the model updating approach, which iteratively varies the properties of a numerical model of a pile to obtain a match in the FRF data, and subsequently estimates the mobilised stiffness, mass, and embedded length. The results of the analyses illustrate that by minimising the difference in the first and second FRF peaks between the target and estimated FRFs, the method can accurately estimate the mass, stiffness and embedded length properties of the test ‘piles’. The performance of the approach against numerical case applications is assessed in this paper, as the properties of these systems are known in advance, facilitating quantification of the errors and performance. The developed method requires further validation through full-scale testing to confirm its effectiveness in real-world scenarios.
► Positive effect of diverse rotation on soil structural quality. ► Diverse crop rotation needed for optimal performance of no tilled soil. ► Crop yield correlated significantly with the visual soil ...structure scores.
Tillage and rotation are fundamental factors influencing soil quality and thus the sustainability of cropping systems. Many studies have focused on the effects of either tillage or rotation, but few have quantified the long term integrated effects of both. We studied the issue using a 30-year old long-term rotation and tillage treatment experiment on a Canadian silt loam soil. Topsoil measurements were carried out for three different rotations: R1, (C–C–C–C) continuous corn (Zea mays L.), R6, (C–C–O(RC), B(RC)) corn, corn, oats (Avena fatua L.) and spring barley (Hordeum vulgare L.) and R8, (C–C–S–S) corn, corn, soybean (Glycine max L.), soybean. A red clover (Trifolium pretense L.) cover crop was under seeded in oats and spring barley in R6. In 2010, first year corn was grown in R6 and R8. The tillage treatments included no tillage, NT and mouldboard ploughing, MP. Topsoil structural quality was visually evaluated in early June and mid October. Minimal disturbed soil cores collected in early June were used for X-ray CT scanning and to quantify water content and porosity. Soil friability was determined on the soil samples using a drop shatter test. Crop yield was determined and correlated to the soil quality estimates. We found significant effect of both rotation and tillage on visual soil structure at both times of assessment. Poor soil structure was found for NT except when combined with a diverse crop rotation (R6). The soil core pore characteristics data also displayed a significant effect of tillage but only a weak insignificant effect of rotation. The drop shatter results were in accordance with the visual assessment data. Crop yield correlated significantly with the visual soil structure scores. We conclude that a diverse crop rotation was needed for an optimal performance of NT for the studied soil.
This work reveals the existence of a new dynamic load amplification mechanism due to ground surface loads. It is caused by the interaction between a moving vehicle's axle configuration and the ...vibration characteristics of the underlying soil-guideway system. It is more dominant than the traditionally considered ‘critical velocity’ dynamic amplification mechanism of the guideway-ground structure, and is of relevance to very high speed transport systems such as high speed rail.
To demonstrate the new amplification mechanism, first a numerical model is developed, capable of simulating ground-wave propagation in the presence of a series of discrete high speed loads moving on a soil-guideway system. The model couples analytical equations for the transportation system guideway with the thin-layer element method for ground simulation. As a practical example, it is validated using high speed railroad field data and then used to analyse the response of a generalised single moving load at high speed. Next the effect of multiple discrete vehicle-guideway contact points is studied and it is shown that dynamic amplification is highly sensitive to load spacing when the speed is greater than the critical velocity. In particular, large resonant effects occur when the axle/magnet loading frequency and the propagating wave vibration frequency of the soil-guideway structure are equivalent. As an example, it is shown that for an individual case, although critical velocity might increase displacements by 50–100%, for the same scenario, axle configuration can increase displacements by 400%. It is also shown that resonance is sensitive to the total number of loading points and the individual frequencies excited by various spacings. The findings are important for current (e.g. high speed railway) and potential future (e.g. hyperloop) transport systems required to operate at speeds either close-to, or greater than the critical velocity of their supporting guideway-soil structure. In such situations, it is important to design the vehicle and supporting structure(s) as a combined system, rather than in isolation.
•A new dynamic load amplification mechanism for moving ground surface loads is presented.•Vehicle-guideway contact configuration is dominant in resonant amplification.•Resonant amplification can be more important than critical velocity amplification alone.•Findings are relevant for high speed rail and future transportation technologies (e.g. hyperloop vacuum systems).•Very high speed vehicles and transport infrastructure should be designed as a combined system.
Ground vibrations induced by railway traffic at grade and in tunnels are often studied by means of two-and-half dimensional (2.5D) models that are based on a Fourier transform of the coordinate in ...the longitudinal direction of the track. In this paper, the need for 2.5D coupled finite element-boundary element models is demonstrated in two cases where the prediction of railway induced vibrations is considered. A recently proposed novel 2.5D methodology is used where the finite element method is combined with a boundary element method, based on a regularized boundary integral equation. In the formulation of the boundary integral equation, Green's functions of a layered elastic halfspace are used, so that no discretization of the free surface or the layer interfaces is required. In the first case, two alternative models for a ballasted track on an embankment are compared. In the first model, the ballast and the embankment are modelled as a continuum using 2.5D solid elements, whereas a simplified beam representation is adopted in the second model. The free field vibrations predicted by both models are compared to those measured during a passage of the TGVA at a site in Reugny (France). A very large difference is found for the free field response of both models that is due to the fact that the deformation of the cross section of the embankment is disregarded in the simplified representation. In the second case, the track and free field response due to a harmonic load in a tunnel embedded in a layered halfspace are considered. A simplified methodology based on the use of the full space Green's function in the tunnel–soil interaction problem is investigated. It is shown that the rigorous finite element-boundary element method is required when the distance between the tunnel and the free surface and the layer interfaces of the halfspace is small compared to the wavelength in the soil.
•Energy based analysis and design framework for soil-structure systems.•Thermodynamics based.•Comprehensive analysis and design approach for soil-structure systems.
Presented is an energy-based ...analysis and design framework for soil structure interaction system. Theoretical formulation based on thermodynamics and engineering mechanics for calculating energy dissipation in soil and structural elastic plastic finite elements is presented and discussed. The importance of incorporation of plastic free energy, that ensures nonnegative incremental energy dissipation, also known as the second law of thermodynamics, is emphasized. For application to practical engineering problems, the presented framework is implemented in the Real-ESSI Simulator and visualized using ParaView. In order to illustrate the proposed framework, a practical model composed of a reinforced concrete frame structure, underlying soil, and soil-foundation interface is developed and analyzed. Elastic-plastic material model and viscous, Rayleigh damping parameters are calibrated to represent typical realistic cases. Spatial and time distribution of energy dissipation density is analyzed and discussed. Locations with high plastic energy dissipation, used as a proxy for material and structural damage are identified. In addition, locations of high plastic energy dissipation within soil and soil-foundation interface, that are used to dissipate seismic energy before it reaches structure, are also identified. Influences of input seismic motion scale and design variation on system performance are investigated. It is shown that traditional displacement-based design parameters, such as peak displacement and maximum interstory drift ratio, could underestimate the change of system performance when different seismic motion scale or structural design are used.
This paper compares the response of a jacket-supported offshore wind turbine (OWT) under wave loading, when (a) soil–structure interaction (SSI) is ignored and (b) SSI is considered. The jacket is ...placed in a water depth of 70m and soil conditions off the west coast of India are used in the study. The rotor of the OWT is considered to be parked, under a survival average wind speed of 50m/s, significant waver height Hs=16m and peak spectral period Tp=18s. The significance of includng SSI in OWT studies is investigated by means of pushover analyses and irregular-wave dynamic analyses. Modal studies are performed to determine the variation in the free-vibration response of the two cases. It is observed that ignoring SSI tends to over-estimate the ultimate strength characteristics of the OWT by 3–60% in various modes or increase the tower top displacement above serviceable limit. For dynamics analysis, the wave elevation is generated using wave superposition method. The JONSWAP wave spectrum is discretized using constant area method which introduces additional uncertainty. The analysis shows that approximately 200 frequencies are necessary using constant area method to capture the tail region appropriately. Also the statistical uncertainty in the generation of wave elevation for dynamic analyses is quantified by means of sample convergence studies. The results show that approximately 20–40 samples are required in order to obtain reasonable statistics.
•Time domain response of jacket offshore wind turbine with soil effects is studied.•Considering SSI, natural frequency shifts by 60%, ultimate load lowers by 4 times.•Failure nature under SSI by lateral pile movement; without SSI by member buckling.•The stochastic load effects require 20-40 MCS for correct ensemble statistics.
Much research has been conducted in recent decades on structural control to improve the performance of different towers and high-rise buildings against severe earthquakes and strong winds. Most ...studies on building vibration control have been considered just two-dimensionally using shear frame models. In reality, most of the buildings might have irregular plans and thus experience torsion when subjected to earthquakes. Such torsion would further increase the structural response. On the other hand, some buildings are located on soft soil that would trigger the soil-structure interaction (SSI) effects required to be considered for design purposes. The main dynamic behavior parameters like natural frequencies, damping ratios and mode shapes would depend on construction site conditions and thus the SSI effects must be taken into account for buildings on soft soil. In this paper, a mathematical model is developed for calculating the seismic response of an irregular multi-story building equipped with active tendons. The SSI effect is then introduced by changing structure mass, stiffness and damping matrices. The model is employed to obtain the seismic response of 10-story buildings using active tendon with LQR algorithm. The building is modeled as a structure composed of members connected by rigid floor diaphragms with three degrees of freedom at each story; i.e. lateral displacements in two perpendicular directions and a rotation with respect to a vertical axis. Results showed that active tendons have low effects on the reduction of structural response when the building has been located on soft soils.
•Eccentricities in plan caused tendons in perpendicular direction to be active during an earthquake.•Soft soil induces the active tendon produce high force to reduce structural response.•Structural response mitigation fails in the buildings located on soft soil by active tendons•Reduction of structural response is similar in all stories of buildings located on soft soil.
•Root traits have a major role in modifying ecosystem processes.•These impacts of root traits operate via a variety of mechanisms.•Global change could modify relations between root traits and the ...soil environment.•Such modifications could have far-reaching implications for ecosystem processes.
Ecologists are increasingly adopting trait-based approaches to understand how community change influences ecosystem processes. However, most of this research has focussed on aboveground plant traits, whereas it is becoming clear that root traits are important drivers of many ecosystem processes, such as carbon (C) and nutrient cycling, and the formation and structural stability of soil. Here, we synthesise emerging evidence that illustrates how root traits impact ecosystem processes, and propose a pathway to unravel the complex roles of root traits in driving ecosystem processes and their response to global change. Finally, we identify research challenges and novel technologies to address them.
Soil Structure interaction of Laterally Loaded Piles Samuel, Kesiya Elizabeth; John, Beena Mary; Nair, Rajesh P
IOP conference series. Earth and environmental science,
04/2023, Letnik:
1161, Številka:
1
Journal Article
Recenzirano
Odprti dostop
Abstract
The rapid development of the global economy has led to an increased energy demand throughout the world. More than 70% of the world’s energy consumption is from the use of fossil fuels. In ...the wake of rising global temperatures and increased carbon emissions, policymakers across the globe think about alternate and renewable ways of energy generation, among which wind energy is a promising energy source. Offshore wind turbines are new technologies and are challenging when it comes to their installation in harsh ocean environment as they are subjected to environmental loads caused by wind, wave and currents. These loads are then transferred to foundation. Monopiles are the most common foundations used in offshore wind turbines today and therefore its analysis is important. Monopiles are single large diameter tubular steel piles of diameter 3–7 m driven into the seabed with typical penetration depth of 25–30 m, and are subjected to lateral dynamic loads. Soil structure interaction of monopile is an important aspect to be considered in its design and for the present study, PLAXIS 3D geotechnical software is used for the soil-pile interaction and the corresponding displacement behaviour of the pile under study. The dynamic analysis due to the wave forces on the monopile is carried out using wave data off Gulf of Mannar, near the Tamil Nadu coast, and the embedment length of the pile is varied to study the effect of diameter of pile and embedment length on the displacement characteristics of the pile.
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