Types Of Piles Research Articles

Experimental Study on the Symmetry of the Soil-Arching Effect of a Pile Foundation in a Reinforced High-Fill Area

In addition to the vertical external load and soil settlement load, the pile foundation in reinforced high-fill areas is also affected by the horizontal load caused by the rear stacking load, and pile stress is affected by the soil-arching effect in reinforced areas that have typical passive pile characteristics. In order to study the symmetry of the soil-arching effect of pile foundations in a reinforced-fill area, indoor model tests were designed and the relevant data for the pile foundation and reinforced soil under surcharge were obtained. Through the analysis, the following conclusions were drawn: the peak bending moment of the pile body is basically consistent with the position of the potential sliding surface of reinforced soil; the maximum shear force of the pile body appears about 150 mm below the embedding point; with an increase in depth, the soil-arching effect becomes obvious. There are two different forms of friction, soil-arching and direct soil-arching between piles and behind piles, and the soil between single-row piles has a symmetrical distribution. In addition to the vertical external load and soil settlement load, the pile foundation in reinforced high-fill areas will also be affected by the horizontal load caused by the rear stacking load, and pile stress will be affected by the soil-arching effect in reinforced areas, which has typical passive pile characteristics. In order to study the symmetry of the soil-arching effect of pile foundations in a reinforced-fill area, indoor model tests were designed, and the relevant data for pile foundation and reinforced soil under surcharge were obtained. Through analysis, the following conclusions were drawn: (1) the peak bending moment of the pile body is basically consistent with the position of the potential sliding surface of reinforced soil; the maximum shear force of the pile body appears about 150 mm below the embedding point; with an increase in depth, the soil-arching effect becomes obvious. There are two different forms of friction, soil-arching and direct soil-arching between piles and behind piles, and the soil between single-row piles has a symmetrical distribution.

Load-bearing capacity of open-ended pipe piles with interior wings in sand

ABSTRACT Pipe pile models were installed with varying pile lengths in accordance with the ratio (L/D = 15 and 20) in loose, sandy soil with a relative density of 25%. Open-ended pipe piles at distances of two or three dimensions now have interior wings added. The new model shows a larger bearing capacity than the traditional pipe piles (open-ended and closed-ended), which is the most significant outcome of the experimental work done to build the traditional open-ended pipe piles model. The bearing capacities of open-ended pipe piles with interior wings (OE-IW 2D, 3D, 4D, and 5D) are higher than those of typical open-ended piles (94%, 99%, 55% and 136%), and for (L/D = 15), they are (48%, 52%, 18% and 80%) higher than those of closed-end piles. While Open-ended piles with interior wings (OEIW 2D, 3D, 4D, 5D) have a higher-bearing capacity (34%, 40%, 38% and 9%) than the traditional open-ended pile.

Bearing behaviors of rock-socketed piles in layered dynamically compacted soil-rock mixtures: A case study

After layered dynamic compaction (DC) treatment in a mountainous area with deep backfill in Chongqing, China, a series of pile tests and analyses were conducted to evaluate the vertical bearing capacity of rock-socketed piles and to investigate their mechanical characteristic and load-bearing behavior. Static pile load tests (SPLT) were carried out on three types of rock-socketed piles with different diameters (800 mm, 1000 mm, and 1200 mm). Based on the test data of pile reinforcement stress, the pile axial force, frictional resistance, and load-sharing ratio were calculated and analyzed. The results indicate that load-settlement curves of static load tests for all piles change progressively, and the S-lgt curves are relatively straight lines without obvious downward bending. The pile axial force exhibits the characteristics of “large at the top and small at the bottom”, resulting in stress concentration at the pile top, especially prominent in longer piles (lengths of 33.2–37.1 m). Additionally, the overall frictional resistance increases with the increase of pile top load. In shorter piles (lengths of 16.5–22.6 m), the frictional resistance presents a C-type curve with depth, while in longer piles, it presents an S-type curve distribution. Comparatively, the test pile bears the upper load mainly by the side friction resistance, which is more prominent in the longer pile. With the increase of pile top load, the load-sharing ratio of side friction decreases and the load-sharing ratio of pile tip resistance increases.

Bearing Characteristics of Screw-Groove Piles: Model Test and Numerical Analysis.

Screw-groove piles, a new type of precast pile, are economically and environmentally friendly and improve the load-bearing performance of piles through a unique screw-groove structure. To reveal the load-transfer characteristics and bearing mechanism of the screw-groove pile, the axial force, load-settlement curve, skin friction, bearing capacity, and response characteristics of the foundation for piles under vertical loading were analyzed. Furthermore, a parameter analysis of the ultimate bearing capacity and material utilization of screw-groove piles was performed using the finite element method. The results demonstrate that the screw-groove pile had an ultimate bearing capacity 1.85 times higher than that of the circular pile, and its material utilization rate was 2.85 times higher. The screw-groove surface end resistance and pile-tip resistance formed a multipoint vertical bearing mode. It efficiently utilized the soil's shear strength and mobilized a larger volume of surrounding soil to share the load. The screw-groove structure increased the pile-soil interaction surface, thereby increasing the skin friction resistance of the pile. Additionally, increasing the inner radius of the screw groove boosts the pile's bearing capacity but may reduce material utilization. An optimal screw-groove spacing balances both factors, while excessive groove thickness lowers material use. The pile shows high sensitivity to soil parameters.

Bearing capacity of constrained grouting expansion bored pile based on CPTU and expansion tests

Bored Pile of Constrained Grouting Expansion (BPCGE) is a new type of pile that combines grouting, compression, and expansion technologies. However, there is still insufficient understanding of its bearing characteristics and strength degradation, especially when the surrounding mass is located in soft cohesive soil layers. To address the issues mentioned above, analysis of bearing capacity and strength assessment of BPCGE based on piezocone penetration test (CPTU) and expansion tests are taken into account. Firstly, based on the similarity between the pile prototypes and models, constrained grouting expansion tests are conducted to study the borehole expansion and soil consolidation effects, and analyze the influence on effective stress of soil around the pile and stress relaxation characteristics of cohesive soil. Secondly, CPTU tests and numerical simulations were carried out to investigate the size effect of BPCGE, and a conversion relationship between lateral friction resistance of pile and CPTU friction resistance was established. Finally, the ultimate bearing capacity of BPCGE is proposed. In an application of a high-rise residential project, the calculation method based on CPTU data can effectively predict the ultimate bearing capacity of BPCGE, saving 262 ordinary piles.

3D numerical response of different pipe pile under combined loadings condition embedded in loose sand

ABSTRACT One significant phenomenon not adequately considered in the present design recommendations is pipe pile plugging. Understanding its mechanism is essential for designing new structures. A series of numerical simulations were established to investigate the bending moment, end bearing, and lateral displacement responses of open-ended pipe piles with and without a soil plug and closed-ended pipe piles. After the model has been verified through experimental work, many parameters were performed such as friction angles, pile length, and pile head. It was concluded that for all pile types, there is a significant decrease in the end bearing capacity with the increase of friction angle. Similarly, the bending moment decreases as the friction angle increases. In addition, the maximum bending moment gradually increases with the increases of pile length. Finally, the maximum lateral displacement decreases linearly with the friction angle for different conditions of soil inside the pile, pile lengths, and e/L.

Fatigue analysis of offshore wind turbines with soil-structure interaction and various pile types

Monopile offshore wind turbines (OWTs) are susceptible to fatigue damage, and time domain fatigue analysis is time-consuming and unsuitable for simulating various loading conditions. In this study, frequency domain fatigue analysis of OWTs with soil-structure interaction (SSI) and different monopile designs (the conventional monopile, monopiles with an extension, a wheel, and four spoiler ribs) is conducted. First, detailed 3D finite element models of OWTs are developed. The tower, monopile, and soil are modelled using solid elements, and SSI is accounted for using the Mohr-Coulomb failure criterion and surface-to-surface contact. Next, the power spectral densities of wind and wave loads on the tower and monopile are derived. Subsequently, the fatigue damages of the OWTs are evaluated under individual and combined wind and wave loads. The results show that damage increases with wave height, peaking at the rated wind speed and wave frequency close to the first frequency of the OWTs. Wind-induced damage is significantly greater than wave-induced damage, and the combined wind and wave loads produce more damage than the sum of the individual loads. Additionally, alternative monopile designs, particularly the monopile with a wheel, can reduce fatigue damage, though stress concentration effects on the wheel and ribs require careful consideration.

Research on Load Transfer Mechanism of Pre-Stressed High-Strength Concrete Nodular Pile Embedded in Deep Soft Soil

The pre-stressed high-strength concrete (PHC) nodular pile is a type of PHC pile with a variable cross-section of the pile shaft, and it has normally been applied in ground treatment projects in recent years. The PHC nodular pile shaft consists of nodules, which introduce differences for the load transfer mechanism of the PHC nodular pile compared to the conventional PHC pipe pile. In this paper, the load transfer mechanism and influencing factors of the bearing capacity of the PHC nodular pile were investigated based on a group of field tests and numerical simulations. The following conclusions were obtained based on the analysis of the field test and simulation results: the nodules along the pile could effectively increase the ultimate capacity of the PHC nodular pile, and the field test results showed that the ultimate capacity of 450 (500) mm PHC nodular piles was about 1.23–1.38 times of the 450 mm PHC pipe pile after being cured for 40 days, which can be used for the design of PHC nodular pile. The simulation results showed that the bearing capacity of the PHC nodular pile would decrease with the increase in nodular spacing and nodular length along the pile shaft, while increasing with the increase in nodular diameter, and the diameter of the nodule can be increased moderately to improve the ultimate capacity of the PHC nodular pile.

Influence of Soil Plugging on Dynamic Soil Response During Simulated Pipe Pile Driving Model Test in Sands

The squeezing effect and strike-induced vibration generated by pile driving pose a threat to adjacent structures. To mitigate the squeezing effect, open-ended pipe piles were implemented. However, this type of pile brings a degree of soil-plugging effect, particularly in sandy soil, which complicates the squeezing effect and the dynamic responses of the pile during pile driving. In this study, model experiments were conducted using both open-ended piles and open-ended piles with different fixed-length soil plugs to investigate the squeezing effect and dynamic responses of the piles. Moreover, spectrum analysis was performed to explore the patterns of vibration waves in the open-ended pipe pile during the striking process. For open-ended pipe piles, acceleration fluctuations were detectable solely when the pile reached the sensor depth and at the end of the pile driving process, which revealed that the hammering energy was mainly consumed by pile settlement and the formation of the soil plug. When the formation of the soil plug was completed, the majority of the energy was converted into propagating vibration, resulting in the emergence of another crest of acceleration. The spectrum analysis revealed that the maximum amplitude occurred when the penetration depth was equal to half of the pile length.

Presenting a model for estimating the cube compressive strength of self-compacting concrete in cast in-situ piles using GEP

The cast in-situ pile is a widely used type of deep foundations which its execution in civil projects is increasing daily. The use of ordinary concrete in this type of piles causes technical and executive problems, a decrease in the compressive strength (CS) of concrete, and an increase in the permeability under the ground level. But use of the self-compacting concrete in the cast in-situ piles while increasing the CS of concrete ensures proper compaction, increase in the execution speed, and easy placing of concrete. In this article, utilizing the data obtained from the laboratory results and also the application of soft computing techniques, predicting the degree of CS of self-compacting concrete (SCC) in concrete piles was investigated. To estimate the CS of SCC, a total number of 7 inputs were implemented. Then, using gene expression programming (GEP) a model was presented for estimating the CS of SCC in the cast in-situ piles. The results of the neural network showed a precision of 99.98% which exhibits the high accuracy of the model. The use of this model could greatly help persons, companies, and research centers in the preparation and construction of self-compacting concrete with the desired CS.

Experimental Investigation of the Axial Load Capacity of Bilateral Helix-Stiffened Cement Mixing Piles in Soft Marine Soil

Bilateral helix-stiffened cement mixing piles (BHCMPs) are a new type of robust composite pile. In this paper, the influence of design parameters, such as the diameter of inner helix plates and the number and size of outer mixing helix plates, on the vertical bearing performance of the pile foundation and the behavior of the pile diameter are investigated through laboratory model tests. The results indicate that incorporating a reverse-mixing process in the pile formation of helix-stiffened cement mixing piles can enhance the overall ultimate bearing capacity and strengthen the soil-cement of the piles. In the case of the same double-blade inner drill pipe, for every 22 mm increase in the blades, its ultimate compressive load-bearing capacity was increased by 10% to 25%, and its pullout load-bearing capacity was increased by 15% to 45%. With further increases in the blades, the percentage increase in the compressive and pullout load-bearing capacity was reduced. With an increase in the number of external mixing blades, its compressive load capacity increased in the range of 5% to 20%, and the elevation load capacity increased in the range of 10% to 25%. Increasing the number of reverse-mixing helix plates on the outer casing enhances the soil-cement strength of the pile body by approximately 15–20% for each additional plate. The average strength of the pile-body soil-cement for each additional plate is estimated to be 1 to 1.4 times that of the previous set, indicating that increased mixing iterations can enhance the perimeter soil-cement strength of the pile. The average bond diameter of soil-cement piles with double-blade internal drilling rods could be seen from the diameter of the piles formed, which was 1.02 to 1.21 times the diameter of the blades.

Optimising the embodied carbon of laterally loaded piles using a genetic algorithm and finite element simulation

With the need to cut embodied carbon from the construction industry, there has been a growing interest in optimising the design of different structural elements. This paper, for the first time, minimises the embodied carbon of laterally-loaded piles using a hybrid genetic algorithm. The research is split into four stages. Firstly, the optimisation algorithm is set and run to produce the optimal piles of lateral capacity 0.5 MN at a 25 mm lateral displacement limit, the embodied carbon of solid cylindrical and hollow cylindrical optimised pile designs is compared showing a significant reduction in the embodied carbon when the hollow geometry is used. Then an analysis is presented to test the effect of different displacement limits on the resulting embodied carbon, showing that the lateral displacement limit has a significant effect on the overall embodied carbon of the pile designs, highlighting a scope for reducing the embodied carbon if more pile displacement is permissible. A finite element model is built using ABAQUS simulation package to investigate the soil-pile interaction and compare the two optimal pile designs. Finally, the lateral load capacity of four different pile geometries is calculated to demonstrate the effect of pile geometry on its lateral load capacity, hollow cylindrical piles, showed to have the highest lateral load capacity compared to the other pile types. We conclude that the opportunity for significant carbon savings exists in laterally loaded piles through both optimisation and careful consideration of performance criteria.

Bearing Characteristics of Deep Cement Mixing Integrated Drilling, Mixing and Jetting Piles Based on Numerical Simulation

The Deep Cement Mixing Integrated Drilling, Mixing and Jetting (DMJ) technique has been developed through the installation of high-pressure spray holes at the mixing blades, with the objective of enhancing the bearing capacity of deep-mixed piles in the Yellow River floodplain. In order to enhance the bearing capacity of the foundation, variable-modulus piles and capped piles were incorporated within the DMJ piles. Engineering applications have demonstrated that DMJ piles can effectively address the issue of foundation reinforcement in the Yellow River floodplain region, minimize the wastage of cement, and reduce the environmental pollution associated with waste slurry. Nevertheless, a comprehensive study of the relevant factors is still lacking in the available literature. This study addresses this gap by conducting a numerical simulation of these two types of DMJ piles based on the preliminary field test data, with the objective of analyzing both the single-pile-bearing characteristics and the composite foundation-bearing characteristics. Furthermore, the study seeks to optimize the DMJ pile’s structure based on the simulation results. The findings demonstrate that the premature failure of a single pile during the bearing process can be averted if the modulus of the pile core reaches a minimum of 0.3 GPa or if the pile cap thickness exceeds 1 m. The utilization of large-diameter drilling, stirring and spraying piles can markedly enhance the bearing capacity of the composite foundation and mitigate the differential settlement of pile and soil. The spacing of the pile has been identified as a significant factor influencing the differential settlement of pile and soil. Consequently, this study also examines the impact of pile spacing on the differential settlement of piles and soil.

Database Analysis of Long-Term Settlement Behavior of Pile Foundations in Shanghai Soft Coastal Clays

A database of 195 field records of long-term settlement of high-rise buildings in Shanghai soft coastal clays is presented. The collected field records are divided into two categories based on pile type, i.e., bored pile and precast pile. Based on the settlement recorders collected, the long-term settlement behavior and settlement duration of the pile foundations in soft coastal clays are investigated. The statistical results show that the pile foundation in Shanghai soft coastal clays can be divided into three kinds of site conditions by considering the pile length and variation of long-term deformation behavior. Prediction models based on the power function are proposed to calculate the normalized final settlement for both bored pile and precast pile foundations. Based on the statistical results, the average normalized final settlement (settlement per floor), average settlement ratio (final settlement to the settlement when the superstructure is completed), and average settlement duration in the three site conditions for both bored pile and precast pile foundations are given. Additionally, an exponential settlement prediction model that can accurately forecast the entire settlement and post-construction settlement characteristics of buildings in Shanghai’s soft soil area is proposed. These statistical results can be referred to the preliminary foundation design works, which contribute to the quick evaluation of the possible settlement range, settlement ratio, and settlement duration of the proposed building constructed in the soft coastal clay area in Shanghai.

Scaled model tests on pile types influencing the stability of stiffened deep mixed pile-supported embankment over soft clay

Scaled model tests on pile types influencing the stability of stiffened deep mixed pile-supported embankment over soft clay

Full-scale in-situ tests on a displacement cast in situ energy pile: Effects of cyclic thermal loads under different mechanical load levels on pile stress and strain

Numerous full-scale in situ tests have been conducted to assess the effect of thermal cycles on the pile response. However, those studies investigated the response of only precast and cast in-situ energy piles, with limited focus on the impact of the applied mechanical load on the pile response. This study presents the results of a field test conducted on a new type of energy pile, i.e. a displacement cast in-situ energy pile in multilayered soft soils, subjected to different fixed mechanical loads while undergoing simultaneous thermal cycles. Four tests were carried out, each corresponding to various axial loads ranging from 0 % to 60 % of the pile’s estimated bearing capacity. After applying the axial load on the pile head (0 %, 30 %, 40 %, or 60 % of the bearing capacity), the pile was subjected to up to ten thermal cycles. The highest magnitudes of thermal axial strains were observed near the pile top due to the lowest restraint provided by the made ground layer in all tests. Under zero (0 %) mechanical load, the thermal axial strains near the pile head were elastic and recoverable, while residual strain was observed near the toe. Under reasonable working mechanical loads (30 %, 40 %, or 60 %) residual strains were observed near both the pile head and the toe, with higher residual strains observed under higher mechanical loads. The results indicate that the cyclic thermal loadings could induce an increase in the compressive stress in the energy pile, attributed to the drag-down effects of the surrounding soil. The compressive stress induced by drag-down effects counteracts thermally induced tensile stress and thus leads to an insignificant effect on the energy pile during cooling. A limited impact of the shaft capacity was observed and was mainly attributed to the drag-down of the surrounding soil and thermal creep along the pile-soil interface.

Bearing Performance of a Helical Pile for Offshore Photovoltaic under Horizontal Cyclic Loading

For an offshore photovoltaic helical pile foundation, significant horizontal cyclic loading is imposed by wind and waves. To study a fixed offshore PV helical pile’s horizontal cyclic bearing performance, a numerical model of the helical pile under horizontal cyclic loading was established using an elastic–plastic boundary interface constitutive model of the clay soil. This model was compared with a monopile of the same diameter under similar conditions. The study examined the effects of horizontal cyclic loading amplitude, period, and vertical loads on the horizontal cyclic bearing performance. The results show that under horizontal monotonic loading, the bearing capacities of a helical pile and monopile in a serviceability limit state are quite similar. However, as the amplitude of horizontal cyclic loading increases, soil stiffness deteriorates significantly, leading to greater horizontal displacement accumulation for both types of piles. The helical pile’s bearing capacity under horizontal cyclic loadings is approximately 60% of that under monotonic loading. With shorter cyclic loading periods, horizontal displacement accumulates rapidly in the initial stage and stabilizes over a shorter duration. In contrast, longer cyclic loading periods lead to slower initial displacement accumulation, but the total accumulated displacement at stabilization is greater. When vertical loads are applied, the helical pile exhibits more stable horizontal cyclic bearing performance than the monopile.

Study of Deformation Performance and Seismic Damage on Pile-Supported Wharf by Shaking Table Test

Combined with the research results of shaking table test, through the deformation performance of steel pipe pile foundation, the seismic damage and seismic performance of steel pipe high pile wharf are evaluated, and the appropriate evaluation method is given. By setting the numerical analytical model of multi working condition steel pipe high pile wharf with different water depth, different pile types and different pile diameters, the limit displacement of the pile in the soil under different ground motions is calculated. The calculated results show that, the plasticity ratio (defined as μ = δu/δy ) of the structural system of steel pipe high pile wharf ranges from 1.5 to 3.0; and the fitting relationship between plasticity ratio μ and the diameter thickness ratio D/t was obtained. The fitting relationship is tested by the existing experimental research results. The results show that the given fitting relationship can be in good agreement with the experimental results in the range of ± 15%. On the basis of this fitting relationship, taking the diameter thickness ratio as the basic parameter, a seismic damage evaluation method of steel pipe high pile wharf structure based on deformation performance is proposed.

Study on construction technology and bearing mechanism of pressure cast-in-situ pile with spray-expanded frustum

The pressure cast-in-situ pile with spray-expanded frustum (PCPSF) is a new type of pile developed by the last author, which is composed of pile body, ribbed plate and expanded body with double-frustum. This paper presents the equipment used to produce the PCPSF and the spray-expansion extrusion vibration and pressure method used for construction of the PCPSF. The PCPSF model of cement soil transition layer around pile is built with finite element software. The accuracy of the numerical calculations is verified through a comparison with the results of static load tests conducted on PCPSF. Furthermore, the impact of the expanding ratio, expanded body location, and ribbed plate length on the response of the PCPSF is investigated. The results show that: (1) the ultimate bearing capacity (UBC) of PCPSF single pile is proportional to the diameter expanding ratio and the length of the ribbed plate; (2) the improvement of the bearing capacity of single cubic concrete of PCPSF decreases with the increase of expanding ratio; (3) the bearing capacity of expanded body can be activated ahead of time as it advances up in position, and there is a trend toward a steady increase in the combined bearing capacity of the expanded body and pile end; (4) as the expanded body moves up, the vertical stress of the soil below pile tip decreases, the rate of decay of additional stress is accelerated; (5) under the identical circumstances, the PCPSF's bearing capacity is 1.5 times greater than the traditional cast-in-place pile's, and the presence of cement soil transition layer contributes 15 % of the lateral resistance of the PCPSF.

The Behavior of Enlarged Base Pile Under Compression and Uplift Loading in Partially Saturated Sand

The aim of this paper is to study the behavior of enlarged base piles embedded within partially saturated soils under compression and uplift loading. This type of pile is rarely excavated and cast on-site. Accordingly, to construct an enlarged base pile model, an excavator was designed and manufactured to give appropriate shape through drilling and casting in the laboratory through the design and manufacture of an excavator to produce piles with a shaft of 35 mm in diameter, 500 mm in length, and a base of 80 mm in diameter inclined at an angle of 60 degrees. Three different partial saturation soils were achieved by lowering the water level below the soil surface 20, 40, and 60 cm and measuring the suction force of each stage using a Tensiometer. The average matrix suction results were 6.4, 7.6, and 9.1 kPa for each lower water level, respectively. The test results showed that the bearing capacity of the enlarged base piles under compression load in partially saturated soil was higher than that in the case of full saturation because of matrix suction, with an improvement rate of 2.5–4.5 times compared with the case of fully saturated soil. Additionally, test results showed that the enlarged base piles subjected to uplift loading in partially saturated soil were significantly improved compared with the fully saturated condition, with an improvement rate of 1.5 - 3 times. The reason for this is the apparent surface cohesion of the sandy soil, which increases the bearing capacity of the sandy soil. This study sheds light on the phenomenon of apparent surface cohesion of sandy soil and the extent of its effect on increasing the soil’s resistance to the loads placed on it. Doi: 10.28991/CEJ-2024-010-10-08 Full Text: PDF