Vertical Piles Research Articles

Basic Robotecnical Platform for Implementation of Accurate Farming Technologies

Improvement of modern technical systems and technologies. Increasing the productivity of modern agricultural machines with increasing their weight, which leads, in the course of their work, to a significant compaction of the soil. The heterogeneity of the soil, as a bearing surface, causes not adjustable fluctuations in the workplace, which makes automation of the application of robotics more difficult. Modern solutions to the problems of reducing the negative impact on the soil, increasing the permeability of aggregates due to the reconstruction of the propulsors do not give the proper effect. More cardinally solve these problems, as well as the ability to implement automation and robotics bridge systems such as ABAC, moving along rail tracks, AASP on vertical piles and point gravel-halide supports with concrete platforms. The most promising of these is the AAS platform, which is a 30x10 m bridge structure that moves by step-by-step extension, the beams onto 3 subsequent pads located 10 m away. After entering the new position of the bridge platform, along the long 30-meter span beams Moves the work-technological module with a set of working elements, performing the programmed operations. Thus, in the AASP bridge system under consideration, the soil area subjected to compaction at reference points is just over 1% of the 70% protraction of modern machines. Compared to the ABAC system, moving along railways, the equipment of point supports is much less expensive and requires insignificant operating costs. At the same time, the rigidity of AASP design ensures stable operation of technological mechanisms in a programmed robotic mode with a minimum of unproductive energy costs associated with movement.

Heating and cooling induced stresses and displacements in heat exchanger piles in sand

Heating and cooling of heat exchanger piles causes changes in the axial stresses in the pile and vertical pile displacements. Changes in axial stress (thermal stresses) are more significant in the case of fixed head piles, while vertical displacements are more important in the case of free head piles. This paper presents a series of finite element analyses that was performed in order to investigate the effect of the heating or cooling duration, the surface thermal boundary condition, the mechanical and thermal parameters of the soil and the temperature change in the pile, on the thermal stresses that develop in fixed head piles and the thermal vertical displacements of free head piles in sand. The numerical modelling procedure is first validated through the simulation of a set of published centrifuge experiments of heat exchanger model piles in sand. The results of an extensive parametric numerical investigation are then presented and the effect of the abovementioned potentially influencing factors is presented and discussed. Based on the numerical results, the most important parameters that affect the mechanical response of heat exchanger piles to heating or cooling are identified. Finally, design charts are proposed for the calculation of the maximum thermal stresses that develop in fixed head piles and the pile head thermal vertical displacement of free head piles.

Behavioural analysis of vertical and batter pile groups under vertical and lateral loading in sand

Laboratory model tests were carried out to study the behaviour of vertical piles and batter pile groups under vertical and lateral load. The model pile groups were made up of mild steel rod of 8-mm diameter. Parameters such as degree of batter and different length to diameter ratios of 7.50, 15.00 and 22.50 were considered in this study. The size of the model tank was 1000 mm × 1000mm × 800 mm. Experiments were performed on 3 × 3 model pile groups with a row of batter piles both positive and negative in addition to vertical pile groups with batter angle 0° in sandy soil subject to vertical and lateral loads. It was observed that the behaviour of vertical pile groups and group of piles with batter piles were similar but it showed substantial variation in the capacity of pile groups. Results indicated that the load–settlement relationships were non-linear for all model pile groups both under vertical and lateral loading. Numerical FEM analysis using ABAQUS/CAE 6.11 was also used to compare and validate the load carrying capacity of pile groups obtained from the experimental model tests.

Experimental investigation of vertical and batter pile groups subjected to dynamic loads

In the present work, the dynamic responses of cast in-situ reinforced concrete vertical and batter pile groups constructed in the silty sand have been investigated. An experimental study was carried out on four pile groups: a group of three vertical piles and a group of three batter piles arranged in triangular pattern, and a group of four vertical piles and a group of four batter piles arranged in square pattern. All batter piles were inclined at 20° to the vertical. Each pile group had a rigid pile cap supporting the oscillator-motor assembly for generating the dynamic loads. The pile groups were tested by varying the exciting force level in different loading direction, and their responses were compared in terms of resonant frequency and peak displacement. The peak displacement of the batter pile group shows a significant reduction (about 25% and 50% in vertical and lateral directions, respectively) compared to their respective vertical pile groups.

Analysis of Vertical Piles Embedded in Organic Soil under Oblique Pull-Out Load

Abstract Experiments regarding single model piles embedded in organic soil were conducted to determine the effect of pile type and soil density on ultimate pile oblique pull-out loads. Wood, steel, and smooth as well as rough concrete piles with diameters of 20 mm and embedment lengths of 200, 400, and 600 mm (length-to-diameter ratio L/D of 10, 20, and 30) were examined. The pull load was applied at an inclination of 0°, 30°, 60°, and 90° to the vertical axis of the pile. For each inclination angle, ultimate pull-out capacity was determined from load-displacement curves. Test results indicate that ultimate pull-out capacity increased with an increase in L/D ratio. While there was an increase in the pull-out load resistance of wood, steel, and smooth concrete piles when the angle of load inclination increased, there was a decrease in the pull-out load resistance of rough concrete piles when the load inclination angle exceeded 30°. Moreover, ultimate load capacity decreased when soil density decreased. Lateral pull-out capacity exceeded the axial uplift capacity of the steel, wood, and smooth concrete piles, and there was a slight increase in the ultimate load capacity of the rough concrete pile. The ultimate resistance of the piles was calculated theoretically via a semiempirical method and compared with test results. A comparison of the measured and predicted values indicated reasonable agreement pertaining to rough concrete piles and a disconnect regarding the other piles.

Numerical investigation of solitary wave interaction with a row of vertical slotted piles on a sloping beach

To improve our current understanding of tsunami-like solitary waves interacting with a row of vertical slotted piles on a sloping beach, a 3D numerical wave tank based on the CFD tool OpenFOAM® was developed in this study. The Navier-Stokes equations were employed to solve the two-phase incompressible flow, combining with an improved VOF method to track the free surface and a LES model to resolve the turbulence. The numerical model was firstly validated by our laboratory measurements of wave, flow and dynamic pressure around both a row of piles and a single pile on a slope subjected to solitary waves. Subsequently, a series of numerical experiments were conducted to analyze the breaking wave force in view of varying incident wave heights, offshore water depths, spaces between adjacent piles and beach slopes. Finally, a slamming coefficient was discussed to account for the breaking wave force impacting on the piles.

Parameter estimation of a breaking wave slamming load model using Monte Carlo simulation

For offshore wind turbines (OWTs) located in relatively shallow water, the design is influenced by the occurrence of breaking waves. The strongly nonlinear properties associated with the wave breaking process result in challenges in modelling their impact loads on the structures. The total impact loads are normally calculated as the sum of a slowly varying quasi-static load and an impulsive slamming load. The quasi-static load is normally calculated using Morison’s equation and the slamming load is approximated by the Goda model or the Wienke-Oumeraci model. Given the dynamic properties of OWTs, structural resonances might be excited by the impulsive slamming load. Therefore, there is a clear need to evaluate the response effect excited by the slamming load. In this paper, the response of a vertical pile subjected to a severe breaking wave case is investigated by a combination of data from a large-scale experiment and numerical simulations. The slowly varying quasi-static load obtained in a non-breaking wave packet is modelled using Morison’s equation with the wave kinematics obtained from a fully nonlinear potential flow solver OceanWave3D. The governing parameters used in a slamming load model are estimated using the Monte Carlo method and verified by comparing the experimental data with the numerical simulation results. It is found that the slamming coefficient and the curling factor are close to the values found by the Wienke-Oumeraci model, however the impact duration is significantly larger than the values found by the Goda model and the Wienke-Oumeraci model, which is important for the assessment of the dynamic responses of OWTs.

Evaluation of vertical effective stress and pile tension capacity in sands considering scour-hole dimensions

Evaluation of vertical effective stress of soils around piles is essential to calculation of pile capacities. However, the widely-used design manuals such as FHWA and API recommend different methods for calculating the vertical effective stress under scour conditions, which thus lead to different calculations of pile capacities. This paper was to evaluate the suitability of the existing methods and the proposed analytical solution for estimation of pile tension capacity by comparing them with FE analyses under different scour-hole dimensions. Based on the comparisons, recommendations were developed for selecting an appropriate method to calculate pile tension capacity under different scour-hole conditions.

Modeling oblique load carrying capacity of batter pile groups using neural network, random forest regression and M5 model tree

M5 model tree, random forest regression (RF) and neural network (NN) based modelling approaches were used to predict oblique load carrying capacity of batter pile groups using 247 laboratory experiments with smooth and rough pile groups. Pile length (L), angle of oblique load (α), sand density (ρ), number of batter piles (B), and number of vertical piles (V) as input and oblique load (Q) as output was used. Results suggest improved performance by RF regression for both pile groups. M5 model tree provides simple linear relation which can be used for the prediction of oblique load for field data also. Model developed using RF regression approach with smooth pile group data was found to be in good agreement for rough piles data. NN based approach was found performing equally well with both smooth and rough piles. Sensitivity analysis using all three modelling approaches suggest angle of oblique load (α) and number of batter pile (B) affect the oblique load capacity for both smooth and rough pile groups.

Experimental investigation of local scour around submerged piles in steady current

Submerged vertical piles are an analogue for a range of subsea structures. In this paper scour around submerged piles with both circular and square cross-section are explored experimentally in steady currents. A wide range of cylinder height to diameter ratio (h/D= 0.1–8) is considered for flow intensities spanning clear-water to sheet flow conditions. Results are presented in terms of the equilibrium scour depth and the time-scale of the scour process. For the cross-sectional shapes considered the experimental results indicate that the equilibrium scour depth reduces with aspect ratio when h/D<∼ 4, whilst for larger aspect ratio the scour depth is similar to that for an infinitely tall cylinder. The amount of reduction in scour depth with aspect ratio for short piles is found to be dependent on the flow intensity, such that the effects of aspect ratio and flow intensity on scour depth are not separable. With respect to the time-scale, the experiments indicate that for a flow intensity corresponding to live-bed conditions, a maximum time-scale occurs for an intermediate aspect ratio; for aspect ratios below this value the time-scale reduces because the equilibrium scour depth reduces, whilst for larger aspect ratios the time-scale reduces because the local transport rate is increased. Alternatively, in clear-water conditions the time-scale reduces continuously with increasing aspect ratio. Empirical equations are derived based on the experimental results so as to better account for aspect ratio in scour design.

Hydro- and Morpho-dynamics Induced by a Vertical Slender Pile under Regular and Random Waves

Hydro- and Morpho-dynamics Induced by a Vertical Slender Pile under Regular and Random Waves

A foundation treatment optimization approach study in hydraulic engineering

To reach a better foundation treatment project, an optimized analysis of composite foundation was studied in the field of hydraulic engineering. Its unique characteristics in hydraulic engineering were concluded. And, the overall and detailed analysis of the composite foundation model established was carried out. The index parameters of the vertical reinforced rigid pile composite foundation were formulated. Further, considering the unique role of cushion in hydraulic engineering, its penetration and regularity were analyzed. Then, comparative and optimized analyses of cushion multistage physical dimensions and multistage material characteristics were established. The parameters of the piles distance were optimized and the multilevel scientific and reasonable parameters information was obtained. Based on the information of these parameters, the practical application was verified. It effectively supported the effective application of vertical reinforcement rigid pile composite foundation in hydraulic engineering. The service mechanism of composite foundation was fully analyzed.

Changes in flow structures and energy reduction through compound tsunami mitigation system with embankment and lined piles

For mitigating tsunamis that overtop an embankment, flume tests were conducted to clarify the energy reduction of a tsunami due to a compound defense system by a combination of a sea embankment and lined vertical piles behind the embankment. The relationship between the flow structure and energy reduction was investigated with changing pile height, spacing, and number of rows. The flow structure was classified into 10 types, and the patterns were classified into two. The energy reduction increased with smaller spacing between lined piles, and the reduction of energy and fluid force behind piles gradually decreased when the piles were submerged. In some cases, energy reduction became very low or energy was locally concentrated because standing waves were generated behind the piles. Two important parameters were proposed, ResP*, consisting of pile spacing, pile diameter, and number of lines of piles in the downstream direction, and Ps*, comprising overflowing water depth, pile height, and embankment height. Ps* discriminates whether the piles are emergent or submerged, and ResP* classifies the change in the flow structure pattern. Recommended design criteria to reduce tsunami energy and to prevent the formation of the standing waves downstream of piles were elucidated by these two parameters.

ANALYTICAL STUDY OF NATURAL DRAUGHT COOLING TOWER ON VERTICAL PILES USING FINITE ELEMENT METHOD

The study aimed to analyse the behavior of natural draught cooling tower (NDCT) resting on a vertical pile foundation specifically focusing on prevailing soil conditions in the coastal areas. 27 different cases of shell thickness variation models are studied. The study adopted FEM analysis of NDCT and its foundation as a composite model which also facilitate to study the impact of providing a vertical pile foundation on the behavior of NDCT super structure. Results demonstrated that the reactions on all the piles are within the allowable pile capacities in all cases 1 to 27. In addition, our arc over which lift occurs in the foundation was 0º.The pile support reactions indicate that the horizontal loads on all the piles are varying based on the loads from the superstructure and when the NDCT super structure and its foundation were analysed with composite model.Maximum displacement of the shell and pile forces are reducing by increasing the top level of bottom ring beam.Further, our paper did show the deflection profile and pile reaction variation profile closer to realistic/actual behavior of NDCT than a conventional model.Therefore, the methodology adopted in this paper to study the behavior of 3D modeling of NDCT and its foundation could able to predict the dynamic responses of wind structure. From the results of the study it was established that in coastal areas NDCT can be supported on simple vertical piles instead of conventional raker piles. Further the study also identified optimum shell thickness profiles to be adopted to obtain the optimum foundation and the superstable structure for NDCT resting on vertical pile foundation.

ANALYTICAL STUDY OF SHELL THICKNESS VARIATION MODELS FOR NATURAL DRAUGHT COOLING TOWER ON VERTICAL PILE FOUNDATION

Natural Draught Cooling Tower (NDCT) is an important and essential structure in nuclear and thermal power stations as it contributes both to the energy efficient output and balance to an environment. From the structural point of view, high rise concrete structure is subject to various dynamic loads in an unfavorable way. Wind loading is important in NDCT design for structural safety, elastic stability, vibration properties and the initiation of concrete cracking in comparison to other structures. The behavior change of NDCT due to the variation of shell thickness when NDCT rested on a vertical pile foundation is very interesting. Therefore, the objective of the present paper is to briefly present the finite element modeling and analytical study of NDCT with twenty-seven different types of shell thickness models for the same height of NDCT. Each model is identified based on the separate case number from 1 to 27, and FEM analysis was carried out using Staad Pro-V8i software considering gravity loads, wind load. Further, design wind pressure at different levels along the height of NDCT was calculated as per IS 875 (part 3) 1987 code after applying Interference factor (IF) of 1.573. Due to the lack of wind study findings, the IF was considered as 1.573 while the maximum value of IF was 1.43 as per BS: 4485 (1975). Distribution of wind pressure at each level of NDCT in the circumferential direction was as per IS11504-1985. The overall study identified optimum shell thickness varying models to obtain the optimum foundation as well as super-stable structure. Further, the comparison was made between the guest and peak factor method and found that wind load due to gust factor method was critical and therefore recommended.

Behavioral Characteristics of Group Batter Piles According to Pile Inclination and Action Direction under Statically Lateral Loads

Abstract Pile foundations are designed by vertical piles; however, sometimes batter piles are considered because of their bending rigidity. In general, batter piles are known to have more lateral resistance than the vertical piles, but limited research has been conducted on them because of application limitations and the fact that interpreting construction equipment is difficult. Additionally, field application cases are rarely used for off-shore plants in which lateral loads have a great effect on the foundations of wind power structures. In a single pile, the interaction behavior of a subgrade-pile is so complicated that accurate predictions are impossible. This study is designed to aid in understanding the behavioral characteristics of group batter piles on which a lateral load acts through a model test. The experiments were conducted with 22 single batter piles and 48 group batter piles, and the results showed that the lateral resistance increased as the tilt angle rose. Furthermore, the lateral resistance was at its peak when the lateral loading angle was 60°, and the resistance of the front pile was greater than that of the rear pile. The bending moment, according to the angle of tilt, changed as the group of piles generally increased and as the angle of tilt rose for both the front and rear piles. The action position of the maximum bending moment tends to go up toward the upper part of the piles as the angle of tilt rises for the front and rear piles.

Artificial intelligence design charts for predicting friction capacity of driven pile in clay

In this study, five nonlinear prediction tools are used to model and predict the friction capacity of driven piles installed in clay including classical support vector machine (SVM) and two of its variants, namely regularized generalized proximal SVM and twin SVM, adaptive neuro-fuzzy inference system (ANFIS) and genetic programming (GP). The undrained shear strength, effective vertical stress, pile diameter and pile length are taken as the input parameters of the developed models, and the friction capacity is considered as the output. A total of 80 experimental observations are collected and used to train and test several models estimating the friction capacity of a driven pile in clay. The results demonstrate that, noting the root-mean-square error (RMSE) value, for prediction of the friction capacity of driven piles in clay the ANFIS model gives a better convergence to the in situ results, compared with the GP and SVM models. The developed ANFIS model provided a simple and reliable design structure for proper selection of the pile friction capacity of driven piles installed in clay. Furthermore, a simple mathematical formula is presented based on the GP model. The predicted results are compared with in situ data set models to demonstrate the abilities of the AI models. In order to perform a model evaluation, in addition to RMSE, the regression coefficient of determination is obtained through testing and training of the SVM, ANFIS and GP models. The results show high reliability for the developed models. The presented ANFIS and GP models are introduced as new models in the field of geotechnical engineering.

A hypoplastic macroelement formulation for single batter piles in sand

SummaryBatter piles are widely used in geotechnical engineering when substantial lateral resistance is needed or to avoid the interference with existing underground constructions. Nevertheless, there is a lack of fast numerical tools for nonlinear soil‐structure interactions problems for this type of foundation. A novel hypoplastic macroelement is proposed, able to reproduce the nonlinear response of a single batter pile in sand under monotonic and cyclic static loadings. The behavior of batter piles (15°, 30°, and 45°) is first numerically investigated using 3D finite element modeling and compared with the behavior of vertical piles. It is shown that their response mainly depends on the pile inclination and the loading direction. Then, starting from the macroelement for single vertical piles in sand by Li et al (Acta Geotechnica, 11(2):373‐390, 2016), an extension is proposed to take into account the pile inclination introducing simple analytical equations in the expression describing the failure surface. 3D finite element numerical models are adopted to validate the macroelement that is proven able to reproduce the nonlinear behavior in terms of global quantities (forces‐displacements) and to significantly reduce the necessary computational time.

STRESS-STRAIN STATE FINITE ELEMENT MODEL OF PILE-FOUNDATION BRICK BUILDING VERTICAL EXTENSION

Relevance: Numerical simulation is provided for the stress-strain state of a pile-foundation brick building with the additional structure. The simulation is performed with MicroFe computer system which creates a model of the base – foundation – superstructure system. In this model, finite elements represent the piles. Purpose: The aim of the paper is to perform the finite element analysis of the base – foundation – superstructure system deformation and compare the theoretical and experimental results. Methodology/approach: Two approaches to the numerical simulation are used: 1) rigid foundation and 2) pliable foundation due to the pile displacement. Findings: The bay analysis based on the first approach shows that the stress values exceed the theoretical in some of the structures. The bay analysis based on the second approach shows that the reinforcement deficit amounts to less than 1 % as compared to the theoretical calculations. The obtained results on the estimated and actual displacement at the wall pedestal part show a 15 % difference. During constructing the additional structure, the calculated values of the stress achieve the maximum and exceed design values. With account of the piled foundation, the stress reduction is obtained in engineering structures. Results: The finite element model is designed for the base – foundation – superstructure system. As a result of comparison of theoretical and experimental results, the main parameters of the absolute and relative vertical pile displacement do not exceed the allowable values determined by the national standards.

Comparison of static lateral behavior of three pile group configurations using three-dimensional finite element modeling

The lateral resistance of three pile group configurations was investigated using three dimensional (3-D) finite element modeling. The three pile groups considered in the study were a vertical pile group, a battered pile group, and a mix of vertical and battered piles in a group. The study was motivated by the full-scale static load test that was conducted on the M19 pier foundation in the I-10 twin span bridge in Louisiana. The static lateral resistance of the M19 battered pile group was investigated previously using a 3-D finite element simulation and verified with the aid of experimental results. In the present study, the M19 battered pile group model was used as the basis for the vertical and mixed pile groups for developing their 3-D finite element models. The nonlinear material behavior was accounted for using elastoplastic constitutive models such as the concrete damaged plasticity model and the anisotropic modified Cam clay model. The lateral resistance of the pile groups was investigated in terms of load–displacement, axial load, bending moment, pile damage, soil resistance, and p-multipliers. The results show that the battered pile group had the largest lateral resistance, followed by the mixed and vertical pile groups, respectively. The largest lateral load share was carried by the two middle rows in the battered pile group, while it was in the leading row in the vertical and mixed pile groups. The soil resistance profiles show that the vertical pile group mobilized greater soil resistance than the battered and mixed pile groups at the same lateral load. The back-calculated p-multipliers are the highest in the battered pile group case, followed by the mixed and vertical pile groups, respectively.