Increase Of Pile Diameter Research Articles

Model test study of bridge pile horizontal bearing behavior under landslide deformation

Pile is a common foundation on the slope, which poses a serious threat to the construction and operation if the slope deformation and causes landslide. In this study, a model device of pile foundation on landslide was independently developed by relative displacement loading between pile and soil to explore the influence of landslide deformation on pile and analysis the soil failure rule and the deformation characteristics of pile in different stages of landslide deformation, a few model tests were completed including the relative displacement between soil and pile from 1 to 17 cm, and the pile diameter and the modulus of slide bed were also considered. The results indicated that: the evolution process of landslide deformation with pile foundation on could be divided into four stages including soil compaction, cracks growth, yield stage, and failure stage; ratios of the maximum soil pressure and bending moment growth from the soil compaction stage to the cracks growth stage to the total growth in these four stages are both exceeding 60%; the soil pressure increases with the increase of pile diameter and sliding bed modulus. Therefore, it is best to effectively monitor and control the landslide in the initial soil compression stage that in soil compaction stage and methods such as increasing pile foundations or reinforcing the sliding bed can be used for protection.

An approach for analysis of a single energy pile subjected to a horizontal load in sand

Many studies on horizontally loaded energy piles have tended to ignore the impact of axial frictional resistance in the analysis processes or lacked experimental validation. The effect of axial frictional resistance may be considered by conveniently calculating the frictional resistance and revealing the mechanism of axial frictional resistance. Our proposed displacement analysis approach takes into account pile-sand axial friction during heating. Validation was carried out through a centrifuge test case. Subsequent parametric analyses explored the influence of pile diameter and Young's modulus on the lateral response of the pile. Comparative results between the centrifuge test and proposed approach underscored its effectiveness in capturing the impact of friction resistance on energy piles during heating. The parametric analyses show that the increase in pile diameter from 0.5 m to 0.7 m and Young's modulus from 10 GPa to 20 GPa led to a decrease in normalized pile top displacement by 50.68% and 28.33%, a decrease in maximum soil pressure in front of the pile by 16.18% and 11.59%, and a decrease in maximum bending stress of the pile by 3.27% and an increase by 14.48%, respectively.

Load Transferring Characteristics of Expanded Pile with Cement Mortar Mixture for Pipe Pile

Two kinds of interface shear force transmission models of expanded pile are introduced in combination with FRIC subroutine. ABAQUS is used to carry out numerical analysis to study the load transfer characteristics of expanded pile under vertical load. The results show: the load on the top of the pile is transmitted by the strong cohesive force between the pipe pile and the expanded interface. Under the vertical load, the axial stress of the pipe pile in the expanded pile gradually decreases with the increase of depth, and the axial stress of the expanded part increases first and then decreases with the depth. With the increase of pile length, pipe pile diameter or expansion thickness, the axial stress of pipe pile increases as a whole. With the increase of pile length, the axial stress of the expansion body increases gradually, and with the increase of pile diameter or expansion thickness, the axial stress of the expansion body decreases gradually. The axial stress of the pipe pile in the equal core part of the non-equal core expanded pile gradually decreases with the increase of depth, and the axial stress of the expanded body increases with the increase of the pile length.

Theoretical Analysis of Deformation and Internal Forces of Used Piles Due to New Static-Pressure Pile Penetration

Evaluation of the impact of new static-pressure pile penetration on used piles is vitally important for the reutilization of the used piles. The cavity expansion theory in semi-infinite soil is adopted to obtain the displacement field of the surrounding soil caused by new pile penetration, and then the displacement is applied to the used pile based on a two-stage method to analyze the deformation and internal force of the used pile. The effects of constraint conditions of the used pile, the pile rigidity and the soil modulus on the response of the used pile are considered. Meanwhile, numerical analysis is adopted to verify the effectiveness of the theoretical method. The influence of the distance between the new and used piles and the radius of the new pile is analyzed, and the measures to reduce the influence of new pile penetration on existing piles are proposed. The results show that the form of pile end only affects the deformation near the pile end. With the increase in pile diameter, the existing pile deformation gradually increases. As the distance between the existing pile and new pile increases, the existing pile deformation decreases significantly.

Analysis for laterally loaded pile behavior on offshore sand slope crest considering friction effect and variational base angle in FW

The nonlinear response of horizontally loaded piles located at the crest of offshore cohesionless soil slope is analyzed, based on the failure wedge model (FW) with variational base angle, in this study. The pile deflection differential equation considering the three-dimensional friction effect is derived; the failure wedge model with the variational base angle on slope crest is proposed; the three-dimensional friction effect along the pile on the failure wedge is considered; the calculation formula for ultimate soil resistance around pile on cohesionless soil slope crest is derived. The feasibility of the proposed method is proved by comparing the theoretical results with the test results. Finally, the slope effect and friction effect along the pile on laterally loaded pile behavior and the influence of pile diameter on the friction effect are analyzed and discussed based on the proposed method. Slope can weaken the soil resistance around the pile, while friction can strengthen that around the pile. The friction effect gets more significant with the increase of pile diameter.

Parameter analysis of coupling characteristics and load‐sharing law of arch‐chord coupled anti‐sliding structure

AbstractArch‐chord coupled anti‐sliding structure is a new type of anti‐sliding structure composed of multiple single piles in a specific form. The coupling effect of pile and soil is the most important key point. In this article, the factors that affect the coupling bearing capacity and load sharing ratio of the arch‐chord coupled anti‐sliding structure are screened out, and the rule that the evaluation index is affected by each factor is analyzed. The results show that, with the increase of pile diameter, the value of structural coupling ultimate bearing capacity increases exponentially, but the growth rate slows down gradually. With the increase of pile spacing, the value of structural coupling ultimate bearing capacity decreases. With the increase of soil cohesion around the pile, the value of structural coupling ultimate bearing capacity increases linearly. The coupling ultimate bearing capacity and load sharing ratio of the anti‐sliding structure are the most sensitive to the change of the internal friction angle of the soil around the pile, and the pile diameter has little effect on the evaluation indexes.

Two-Dimensional Finite Element Analysis of Piled Raft Coefficient Settlement Ratio on Clays

Nowadays, designing a piled raft foundation is challenging because the behavior is three-dimensional. For some engineers, a three-dimensional analysis might not be affordable due to more costly than a two-dimensional analysis. In this study, 2D Finite element analysis – axisymmetric was used to study the piled raft foundation. The pile diameter and pile length were varied to investigate the relation between piled raft coefficient and load-settlement. In addition, the load transfer mechanism between the raft part and the pile part in clayey soils is also examined. The results show the longer the pile and the larger the diameter, the greater the load carried by the pile and the smaller the settlement. Increase in pile length by 5 m, resulting in a load transfer of 2% to 6% from a raft to pile, and reduced settlement by 2% to 3%. Furthermore, A 0.5 m increase in pile diameter results in an 8% to 25% load transfer from a raft to pile, and a 2% to 7% reduction in a settlement. The soil consistency affects the load distribution and settlement of the pile-raft foundation system. The higher the soil consistency, the smaller the amount transferred to the pile, and the higher the effectiveness of the pile in reducing the settlement that occurs.

Investigating the Response of Single Pile Under Pure Torsion

Abstract The single pile is a structural element that has an important role in supporting any part of the superstructure. This paper adopted three dimensional finite element modelling by using ANSYS to discover the influence of soil size domain on pile diameter, pile length, load eccentricity and torsion magnitude. One type of soil was used and described by Drucker-Prager model. The numerical analysis has been performed to show how the variation in soil size domain effects on the behaviour of single pile under torsion load. The procedure which is adopted in the investigation depends on fixing all variables and changing one variable to show the impact of this variable on the pile response considering soil domain variation. From the investigation, it is obvious that the pile diameter, eccentricity and torsion load have a major influence on the pile response, while the pile length has a minor influence on the pile response. Here, the increase in pile diameter reduces the load transfer to the soil; also the increase in eccentricity increases the load transfer to the soil while the increase in soil domain reduces the pile response. When the torsion load increases the pile response increases too. The pile response refers to displacement, rotation, shear force and bending moment.

Buckling Stability Analysis for Piles in the Slope Foundation Based on Cusp Catastrophe Theory

The aim of this paper is to analyze the buckling stability problem for piles in the slope foundation based on cusp catastrophe theory. Formulation of critical buckling load of piles in the slope foundation is obtained. The influential factors of slope angle, distribution of landslide thrust behind the pile, pile-embedded ratio, pile constraints, pile-side friction, pile-side soil resistance, and pile socketed ratio upon buckling stability characteristic for piles in the slope foundation are examined. The results reveal that when pile diameter remains unchanged, critical buckling load increases with the increase of pile length when pile-embedded ratio reaches 60%. When pile length remains unchanged, critical buckling load increases with the increase of pile diameter. Critical buckling load with the assumption of nonlinear horizontal elastic resistance of pile-side soil in the paper is more close to the value based on horizontal elastic resistance of pile-side soil suggested in the code. When slope angle increases, decreased extent of buckling critical load for piles 30–60 m in length is more obvious than the piles which are 10–30 m in length. Strengthening of pile constraints and increase of pile-embedded ratio and socketed ratio are helpful to pile critical buckling load increase. The influential factors of pile-side friction and landslide thrust behind the pile upon pile critical buckling load are tiny and can be neglected.

DEM STUDY ON THE PENETRATION OF JACKED PILES INTO LAYERED SOFT CLAY

In order to explore the variation law of soil particle displacement and pile force around piles during penetration process, the DEM (Discrete Element Method) model is used to test the penetration of pile foundation in layered soft soil foundation. The variation law of pile penetration force, radial pressure at pile-soil interface, friction resistance at pile side, displacement field and force field between particles during penetration process is analyzed. Research shows: (1) The penetration force increases with the increase of penetration depth and pile diameter. The increase of pile diameter is beneficial to overcome the influence of unfavorable strata. (2) At the same penetration depth, with the continuous penetration of the pile body, the radial pressure gradually decreases, showing a significant degradation phenomenon. The reason for the degradation of lateral friction is essentially the degradation of the radial pressure. (3) The distribution of contact force chain in different soil layers is similar, but the range of action is different. The contact force in silt layer is obviously larger than that in silty clay layer. The compressive stress of the soil at the end of the pile transfers radially with tensile stress. With the increase of pile diameter, the compressive stress and tensile stress in soil layer are gradually increasing, and the influence range of compressive stress and tensile stress is also gradually increasing. (4) The displacement of the soil below the pile tip is triangular, and the soil at the pile tip is squeezed around under the action of the pile tip. The influence range of particle displacement in each soil layer is different, and the influence range of particle displacement in silt layer is obviously smaller than that in silty clay layer.

Model test of the combined subgrade treatment by hydraulic sand fills and soil-cement mixing piles

The combined technology of hydraulic sand fills and soil-cement mixing piles has been widely applied to urban roads near rivers. Most of the previous studies were limited to the performance and strength of the soil-cement mixing pile and the effect of strengthening the foundation, which ignored the influence of pile layout on soil property parameters. Through laboratory model tests, various working conditions of hydraulic sand placed on a composite foundation were simulated, and the effects of rolling path, standing time, rolling machinery, drainage scheme, pile spacing and pile diameter on stress distribution and consolidation drainage of composite foundation under single variable were investigated in this paper. The test results indicated that the increase in pile diameter can significantly increase the pile-soil pressure ratio but easily causes an excessively high porewater pressure during the rolling of the subgrade. The increase in pile spacing reduces the pile-soil pressure ratio, promotes the drainage efficiency and restricts the pile group effect. Smooth-wheel rolling has a large influence on the stress path and leads to the soil arching effect in the foundation. Reasonable design of pile diameter, pile spacing and proper selection of rolling method are of great significance to improve the efficiency of subgrade reinforcement and reduce postconstruction settlement.

Effect of diameter on the load carrying capacity of Closed-Open Ended Pipe piles

This study investigates the behavior of the components on the pile loading capacity and the effect of removing the components. The sand is used as a fine, sandy soil. It was prepared with different densities using rain technology. The soil plug was removed by a device that was manufactured to remove the soil column trapped inside the piles of the pipes during installation by driving and pressing devices. The present study focuses on determining the effect of soil plug on the maximum load capacity of the open-end steel pipe pile and comparing it with the closed pipe pile. A new type of piles of pipes is proposed; piles of open-ended organic pipes driven and compressed in sandy soils of different densities (medium and dense) where axial pressure tests were carried out on the piles of the model. The end of the pile will be open at a predetermined depth in order to facilitate the penetration of the pile base and close it at a distance to increase the resistance of the pile base. The open pile models were modified by closing the ends of the pile by a welded plate at a distance of two, three, and four D (where D is the diameter of the pile) by the pile.It was concluded that increasing the diameter of the pile from 20 mm to 40 mm caused increase in the pile bearing capacity by about 275 – 615%, while in closed-ended piles, the same increase in pile diameter caused increase in the bearing capacity of about 320 – 860%. On the other hand, in closed-open-ended piles, this increase improves the bearing capacity by about 490 – 1020%. The results prove the controlling importance of the pile diameter in the proposed type of piles; closed-open-ended type.

Effects of scour-hole dimensions on lateral behavior of piles in sands

Scour is a process of soil erosion around foundations caused by currents and waves, which can severely compromise the performance of the foundations. The scour process forms a scour hole around the foundation. The existence of the scour hole has been considered by many design standards for pile foundations such as those from the US Federal Highway Administration (FHWA) and American Petroleum Institute (API). However, these standards recommend different procedures to evaluate lateral responses of piles subjected to local scour that forms three dimensions of scour hole. This paper presents a series of three-dimensional finite element (FE) parametric analyses to examine the feasibility of the standard methods (FHWA and API) as well as an analytical solution proposed by the authors through varying scour-hole dimensions, soil properties, and pile properties. The results showed that the analytical solution provided conservative results while the standard methods provided mixed results compared with the FE analyses. The loss of pile lateral capacity due to scour was more significant in dense sands than in loose sands (approximately 10% more). For a given relative scour depth, the increase in pile diameter increased the scour-induced loss of pile lateral capacity.

Analysis of Factors Affecting Bearing Capacity of Large Diameter Single Piles of Offshore Wind Power under Earthquake Loads

The offshore wind turbine single pile foundation structure is simple and easy to install, but in the earthquake environment, large horizontal displacement is easy to occur, which affects the safe operation of offshore wind turbines. For this reason, the bearing characteristics and influencing factors of large-diameter single-pile offshore wind power under earthquake load are analyzed. The Mohr-Coulomb model is used as the model. The ABAQUS is used to construct the large-scale single-pile finite element model of offshore wind power. Loads and analysis of bearing characteristics and influencing factors of large-diameter single-pile offshore wind power under seismic loading. It is found that the increase of pile foundation depth will significantly reduce the horizontal displacement at the top of single pile. After increasing to a certain extent, it has no significant effect on the development of horizontal deformation of large diameter single pile; with the increase of pile diameter and wall thickness, The deformation of large diameter single pile foundation is reduced, but the influence of the pile foundation thickness on the horizontal deformation of the large diame-ter single pile foundation is no longer significant.

Formation of soil plug in open-ended pipe piles in sandy soils

Open-ended pipe piles are commonly used for the foundations of offshore jacket platforms, mooring piles, offshore wind turbines and, in general, for pile foundations like micro piles, etc. Driveability of open-ended piles is greatly affected by the formation of soil plug during the driving, particularly in sandy soils. In order to study the behaviour of formation of soil plug during driving, open ended model piles were driven into uniformly graded sand in a calibration chamber in the laboratory scale as well as in the field. The influence of the pile diameter, hammer energy and pile penetration depth were studied. The results of the model pile tests showed that the incremental filling ratio (IFR, which indicates the degree of plugging) during driving decreased with pile penetration and increased with increase in hammer energy. IFR has also increased with increase in pile diameter. A correlation between plug length ratio (PLR, percentage plug height with respect to total penetration) and IFR is proposed based on the laboratory experiments.

Internal force calculation and supporting parameters sensitivity analysis of side piles in the subway station excavated by Pile-Beam-Arch method

The Pile-Beam-Arch (PBA) excavation method is widely used in subway station construction for it greatly reduces ground settlement caused by excavation. The stress state of side piles is extremely complex in the supporting system of the subway station excavated by PBA method. This paper deduces the internal force calculation formula for side piles under the most unfavorable loading state with the vertical force considered. Testing apparatus which can model the actual loading state of side piles are designed. Single-factor sensitivity analysis is conducted by means of the reduced-scale model test and numerical simulation to study the three supporting parameters (i.e. pile diameter, pile spacing and buried depth). Results indicate that: the additional bending moment induced by the vertical load at the pile top should be considered in internal force calculation of side piles; values from the deduced theoretical calculation formula agree with the test values; horizontal displacement of the pile body reduces significantly and the bending moment increases greatly with the increase of pile diameter or the decrease of pile spacing; the pile bottom basically meets the constraint condition of the fixed end when the buried depth is two times of the excavation depth. Under the test conditions of this paper, critical sensitivity values of three supporting parameters, i.e. pile diameter, pile spacing and buried depth, are respectively 32mm, 2d (pile diameter) and 2h (excavation depth). It’s more economical and effective to adopt the scheme of increasing pile diameter than the scheme of narrowing pile spacing when there’s a high requirement for displacement control of side piles.

Numerical study of ground vibration due to impact pile driving

Ground vibration due to pile driving is a long-lasting concern associated with the foundation construction industry. It is of great importance to estimate the level of vibration prior to the beginning of pile driving, to avoid structural damage, or disturbance of building occupants. In this study, an axisymmetric finite-element model that utilises an adaptive meshing algorithm has been introduced, using the commercial code Abaqus, to simulate full penetration of the pile from the ground surface to the desired depth by applying successive hammer impacts. The model has been verified by comparing the computed particle velocities with those measured in the field. The results indicate that the peak particle velocity at the ground surface does not occur when the pile toe is on the ground surface; as the pile penetrates into the ground, the particle velocity reaches a maximum value at a critical depth of penetration. Some sensitivity analyses have been performed to evaluate the effect of soil, pile and hammer properties on the level of vibrations. The results show that increase in pile diameter, hammer impact force, soil–pile friction and reduction in soil elastic modulus can increase the peak particle velocity.

Analysis of the Effect of Pile Skin Resistance Verses Pile Diameter Based on Experimental Research

In spite of the many recent advances in pile design and execution methods, the quantitative effects of grouted pile skin resistance and form on subsequent pile behavior remains an area for research. There are many parameters involved in the analysis of the bearing capacity of piles and descriptive method theory of the loading effect for each parameter is very complex. Many of these parameters are interrelated and investigation of the relationships leads to complex equations, which cannot be easily solved. The only reliable solution is to study the influence of each parameter by experimental model tests in equipped laboratories. This research presents the results of static compression tests on two model groups of pipe and grouted pile shafts (35mm, 50mm and 60 mm in diameters and 900 mm in length) installed into beds of Yazd siliceous sand (located in southeast Iran). The findings of the experimental research were to the average ultimate loads at failure for grouted piles were approximately 12% higher than for the pipe piles. The pile skin resistance is an effective factor on pile bearing capacity, the load transfer response appears to be more plastic with increasing pile diameter in siliceous sand and the skin resistance of the pile was not linearly proportional to the pile diameter and varied with increase in pile diameter.

Application of PCC pile in soil improvement of highway

The construction process and load-bearing behaviors of Cast-in-place concrete thin-wall pipe piles are analyzed based on its application on Yantong Expressway Project. The low strain test, static load test and field excavation were also carried out, and the bearing capacity of the new pile can meet the requirements of design. With the increase of pile diameter, the bearing capacity is increased. The settlement of composite foundation is decreased, when the replacement ratio of pile is increased. The test results also show that the load carried by inner soils is neglectable. According to the tests and application, it can be concluded that the new type of pile is convenient to construction with high bearing capacity and reliable quality, which has great potential in practical engineering.