High-strength Concrete Pipe Piles Research Articles

Bearing Performance of Prestressed High-Strength Concrete Pipe Pile Cap Connections under Truncated Pile Conditions

To investigate the load-carrying performance of the nodes between tubular piles and bearing platforms, low circumferential reciprocating load foot-scale tests were performed on two truncated PHC B 600 130 tubular piles. The development law of node destruction was explored. The test results revealed that under the action of tensile–bending–shear loading, the bearing concrete in the node area buckled and was damaged, and an articulation point was formed. When the embedment depth increased from 200 mm to 300 mm, the ultimate bearing capacities of the positive and negative nodes increased by 57.60% and 54.60%, respectively. Numerical simulation was used to analyze the bearing capacities of nodes with different types and embedment depths. Formulas for the bearing capacity of the nodes were proposed. Furthermore, two preferred node types were proposed as follows: pipe pile core-filled longitudinal reinforcement anchored to the bearing node and pipe pile body longitudinal reinforcement anchored to the bearing node + pipe pile core-filled longitudinal reinforcement anchored to the bearing node, with preferred embedment depths of 350 mm and 200 mm, respectively.

Research on bearing capacity of piles with negative skin friction based on field test

There are extensive deep soft soil layers in the coastal areas of China, and the drainage consolidation method is widely adopted for foundation pretreatment in these areas. However, there are still dozens of centimeters of post construction settlement, which may produce negative skin friction on the pile foundation. To accurately estimate the magnitude of negative skin friction, two prestressed high strength concrete pipe piles with different pile end holding layers were used to conduct field tests. The development law of negative skin friction of pile foundation with soil consolidation is studied by simulating different pre-load height conditions of soil around pile. The monitoring results of field tests indicate that with the soil settlement around the pile, the dragload increases gradually and the neutral point moves downward. When the relative displacement between the pile and soil is 87 cm, the neutral point position of the end bearing pile is approximately 44.6-m deep, and the dragload is about 3640 kN, while the friction pile is 30 m and 2160 kN. The analysis shows that if the pile foundation construction is carried out during the foundation pretreatment, the dragload is considerably large, and this may lead to excessive settlement and damage of the pile.

Study on the freezing resistance and repair technology of prestressed high-strength concrete pipe piles

This article takes a prestressed high-strength concrete tube pile (PHC tube pile) in Tianjin Port as the research object, considers the influence of the type of admixture, forming process, and maintenance method in the process of concrete fabrication, and carries out a rapid freeze-thaw test of PHC tube pile concrete. The changes in the mass loss rate, relative compressive strength, and relative dynamic modulus of elasticity with the number of freeze-thaw cycles, as well as the influence characteristics and mechanism of the admixture type, forming process, and curing method, were obtained. Based on this study, the repair and reinforcement of the base concrete were carried out using ultrahigh toughness cementitious composites and cementitious permeable crystalline composites, and a rapid freeze-thaw test was conducted on the repaired concrete specimens to verify the repair and reinforcement effects of the two materials. The study showed that the mass loss rate, relative strength, and relative dynamic elastic modulus can better characterize the freezing resistance of PHC piles, and it is safer to use the relative dynamic elastic modulus as the evaluation index of the freezing resistance of PHC pile concrete than the mass loss rate. The concrete admixture, forming process, and maintenance method have significant effects on the freezing resistance of the PHC pipe pile mix. The splitting damage surface of both ultrahigh-toughness cementitious composites (UHTTC) and cementitious capillary crystalline waterproofing (CCCW) repaired concrete is a reinforced surface, and both repair materials can improve the freezing resistance of PHC pipe piles through the crack arresting effect and reduction in initial porosity.

Shaking table test of prestressed high-strength concrete pipe piles reinforced with non-prestressed steel reinforcement

Prestressed high-strength concrete piles reinforced with non-prestressed steel reinforcement (PRHC piles) have been developed to improve their seismic performance. In this study, the seismic response and failure mechanism of PRHC piles was investigated using a shaking table test. The dynamic characteristics, dynamic soil pressure, superstructure response, acceleration magnification factors, maximum curvature ductility demand, bending moment response, and failure mode identification of the PRHC piles were determined. The performance of PRHC piles was compared with that of prestressed high-strength concrete pipe (PHC) piles, which showed that the PRHC piles experienced higher energy dissipation and lower maximum curvature ductility demands than PHC piles. In addition, the PRHC piles suffered bending failure at the upper-middle positions, and the plastic zones were higher than those of the PHC piles. The adverse effects of long-period and pulse-type ground motions on pipe piles should be considered in designing for strong seismic events. The addition of non-prestressed reinforcement to a pipe pile allows longer segments of the pipe pile to be involved in providing resistance.

Field and Numerical Study of the Bearing Capacity of Pre-Stressed High-Strength Concrete (PHC)-Pipe-Pile-Reinforced Soft Soil Foundations with Tie Beams

Pre-stressed high-strength concrete pipe piles (PHC pipe piles) have been widely used in actual soft foundation treatment projects due to their reliable quality, fast construction, assembly line production, and environmental friendliness. However, large-scale slip damage still occurs in construction projects. In order to reduce and avoid such accidents, a highway in Guangdong (section K31+100~K31+388) was taken as an example for this study. Plaxis 2D software (V22.01.00) was used to establish a PHC pipe pile composite roadbed model and investigate the effects of tie beam form, pile lengths, pile spacings, pile verticality, and embankment filling loading modes on the settlement and stability of the composite roadbed. The results show that the original treatment plan, which had the form of a PHC pipe pile with caps, had a low horizontal bearing capacity and a poor anti-disturbance ability, leading to the occurrence of a landslide accident. A comparison of different structural forms revealed that the longitudinal and transverse tie beam form was the most stable, followed by the transverse tie beam form, longitudinal tie beam form, PHC pipe pile form with caps, and PHC pipe pile form without caps. Compared to the structural form of PHC pipe piles with pile caps, the stabilities of the transverse tie beam form and the longitudinal tie beam form were improved by 42.47% and 38.61%, respectively, while that of the longitudinal and transverse tie beam form was improved by 50.87%. The application of longitudinal and transverse tie beams effectively reduced the settlement of the composite roadbed, as confirmed by both measured data and finite element analysis. This structure achieved the desired vertical settlement control and lateral anti-slip effects.

Multi-scale microstructure quantitative characterization and anti-erosion performance of PHC pipe pile

Pre-stressed high-strength concrete (PHC) pipe pile is widely used in many large-scale projects, thus their durability has attracted more and more attention. However, in most studies, PHC pipe pile is regarded as the same as ordinary reinforced concrete, ignoring the effect of special construction processes and hollow shape on its microstructure and anti-erosion performance. In this paper, the real PHC pipe pile was cored and cut to investigate the multi-scale microstructure and the anti-erosion performance of PHC pipe pile concrete layer. The results shown that pore content first increases and then decreases with PHC pipe pile from the outer layer to the inner layer (5F → 1F) by CT, BSE and LF-NMR results, and the pore content changes most significantly around the rebar in PHC pipe pile. In rebar interfacial transition zone (ITZ), the thickness of the voids in PHC pipe pile is greater than that of normal reinforced concrete under the same water-binder ratio condition. Additionally, the content of un-hydration products in aggregate ITZ is obviously greater than that in rebar ITZ. Furthermore, the chloride ion diffusion coefficient of the concrete on the outside of the PHC pipe pile is slightly larger than that on the inside, which is closely related to the higher pore connectivity of the concrete on the outside of the PHC pipe pile. Moreover, it was found that centrifugation can not only reduce the water-binder ratio of PHC pipe pile but also affect the radial pore structure of PHC pipe pile concrete, including porosity and pore connectivity. This work finally indicated that the microstructure of PHC pipe pile concrete is quite different from that of normal reinforced concrete, providing a theoretical basis for establishing the diffusion model of PHC pipe pile concrete.

Experimental study on permeability of spun high strength concrete material during mechanical loading

The pretensioned spun high strength concrete pipe pile (PHC pipe pile) is widely applied in important infrastructures of off-shore zones due to its low permeability and high capacity. During the construction process and the whole service period of PHC pipe piles, the damage is inevitably caused by many reasons, which may eventually cause the early durability failure of piles. Many researches have been conducted to study the change in permeability of normal concrete due to mechanical damage. However, the relation between permeability and damage of spun high strength concrete (SHSC) is still not been studied. To quantitively investigate the change of permeability of SHSC, a series of specimens of PHC pipe piles were tested for the change of permeability during mechanical loading process in this study. As a result, the relation of stress and permeability of spun high strength concrete as well as the crack roughness of the SHSC is obtained for efficient application in engineering. Before the 40% stress ratio, the permeability of the SHSC is slightly decreased as the compressive stress increases. The mean value and standard deviation of the intrinsic permeability of the SHSC are increased as the compressive stress loading reaches the peak stress. The order of magnitude of the crack roughness ξ can be taken as 10- 4 for engineering application. Compared with the vibrate-casted concrete, the crack roughness ξ is smaller, indicating that the crack surface of SHSC is rougher than the vibrate-casted concrete.

Shake-table test on dynamic response of prestressed high-strength concrete pipe piles under Soil–Structure interaction

This paper presents the results of a shake-table test on a superstructure model supported by a prestressed high-strength concrete (PHC) pipe pile in soft soil. The primary objective is to investigate the dynamic response of the PHC pipe pile in soft soil influenced by soil–structure interaction (SSI). Accordingly, a single PHC pipe pile with iron blocks is constructed and embedded in soft soil. First, the production of the physical model of the PHC pipe pile and experimental details are elucidated. Then, the study focuses on the dynamic response of the soil–pile–superstructure system considering different ground motion types and peak ground accelerations (PGAs). Finally, the inertial and kinematic effects on the dynamic response of the PHC pipe pile are analyzed. The results show that the SSI effect can increase the predominant period of the superstructure. With the SSI effect, the seismic design should consider the adverse effects of long-period and pulse-type ground motions on the pile. The SSI effect caused the rate of increase in the pile bending moment to be gradually higher than the increase in PGA. Moreover, the dynamic response of the PHC pipe pile is mainly dominated by the inertial effect.

Analytical solution for the horizontal dynamic response of strength composite piles in fractional viscoelastic unsaturated ground

The analytical representation of the dynamic interaction between a strength composite (SC) pile and unsaturated soil under lateral excitations at the pile head is studied using three-dimensional continuum modelling. The fractional standard line solid (FSLS) model is utilized in the governing equation of unsaturated soil to characterize the flow-independent viscosity of the soil skeleton. Timoshenko beam theory is employed to describe the horizontal dynamic behaviour of SC piles composed of cement-soil mixing (CM) piles and precast high-strength concrete (PHC) pipe piles. A closed series form solution of the horizontal dynamic behaviour for an SC pile embedded in unsaturated soil under lateral excitation at the pile head is deduced theoretically. The solutions of the proposed model are compared with those captured from existing solutions. Finally, the effects of physical parameters in the SC pile-unsaturated soil system on the horizontal dynamic behaviour of the SC pile are evaluated with analytical examples and parametric study. The results indicate that the radius and elastic modulus of the SC pile have a critical influence on the horizontal dynamic behaviour of the SC pile, the FSLS model parameters are the key factors influencing the horizontal dynamic behaviour of the SC pile, and the horizontal dynamic behaviour of the SC pile varies with the change in liquid saturation of unsaturated soil. The research results provide theoretical references for the anti-vibration design and safe operation of SC piles.

Experimental research on the flow law of the grouting fluid in an annular gap between a non-soil-squeezing PHC pipe pile wall and a hole wall

The bearing capacity of drilling with pre-stressed concrete pile cased pile (hereafter referred to as DPC pile) is closely related to the grouting effect on an annular gap between a pre-stressed high-strength concrete (PHC) pipe pile wall and a hole wall (hereafter referred to as the an annular pile–soil gap). A physical grouting model testing system for the DPC pile based on a high-precision three-dimensional (3D) scanner and a multi-functional grouting box has been independently developed. In this method, 3D geometric size and spatial point information of the grouting stone have been quantitatively characterized. The influences of the water–cement ratio, grouting pressure, collapsed holes, and falling sand have been studied. The conclusions are obtained as follows: (1) a quantitative characterization method of the 3D geometric dimensions of the grouting stone based on a 3D scan is accurate and reliable and can overcome the shortcomings of traditional manual measurement. (2) In the same horizontal plane, grouting body thickness gradually decreases as its horizontal distance from the grouting outlet increases, and the higher the elevation, the greater the rate of decrease; conversely, the lower the elevation, the slower the rate of decrease. When the horizontal distance from the pulp outlet is equal, slurry thickness gradually decreases as the height increases. (3) For the grouting liquid with a water–cement ratio of 0.5, grouting pressure should not be less than 0.6 MPa. (4) When the falling sand is not far above the grouting outlet, a grouting root system can be formed, whose grout veins, complexity, and grout coverage area can be optimally improved by changing the fluidity of the grout and grouting pressure. When the falling sand is on the side of the grouting outlet or the surface of the grouting outlet but far away from the grouting outlet, it is easy to be avoided by the grout, which can greatly reduce the grouting effect.

Research on Dynamic Pile-Driving Formula Parameters and Driving Feasibility of Extra-Long PHC Pipe Piles

Prestressed high-strength concrete (PHC) pipe pile has the advantages of high single pile bearing capacity, a wide range of applications, good driving resistance, fast construction speed, etc. It has been widely used in high-rise buildings, bridges, ports, and other industries. The application of extra-long PHC pipe piles with a length of more than 50 m is increasing. However, there are few studies on the drivability and hammering criteria of extra-long PHC piles. To analyze the drivability of extra-long piles and predict their bearing capacity, in this paper, high-strain dynamic tests were carried out on 14 test sections with the pile foundation of Temburong Bridge in Brunei as the research background. The hammer stop control criteria calculated according to the Hiley formula would lead to excessive hammering. Three types of damage occurred during construction: pile shaft breakage, weld tearing, and pile head breakage. The weight and drop height of the piling hammer selected for this project were appropriate, and the extra-long test piles can be hammered to the design depth. The values of Cp (Compression of the pile) and n (the efficiency of the blow) were fitted based on the dynamic test data, which provided a more accurate reference for the selection of subsequent piling parameters of the project. It provides a more accurate calculation method for predicting the bearing capacity of extra-long PHC piles and provides control criteria for pile stopping and a scientific basis for their design and construction.

Load-Bearing Characteristics of PHC Piles Constructed by the Inner Digging Method Based on Ultimate Load Testing and Numerical Simulation

This paper studies the load-bearing characteristics of two prestressed high-strength concrete (PHC) pipe piles constructed by the medium mid-digging and hammering methods. The ultimate load tests and numerical simulations of the pipe piles constructed by both methods were carried out to analyze the ultimate lateral resistance, and ultimate resistance performance characteristics of the two pipe piles and the influence of the wall thickness of the pipe piles on the bearing performance. The test results show that the pipe pile constructed by the middle inner digging method has a higher pile quality. The single pile bearing capacity of the pipe pile constructed by the middle inner digging method is 50% higher than that of the common hammering method. The enlarged part of the pile end has an obvious effect on improving the bearing capacity. The settlement of the pipe pile constructed by the middle inner digging method is smaller than that of the hammering method. The large diameter pipe pile constructed by the middle inner digging method usually shows characteristics of the end-bearing pile. The resistance of the pile end accounts for 40–50% of the top load. The numerical simulation results agree with the field test and are compared and discussed. The simulation results show that when the bearing capacity of the pile is provided by the pile side frictional resistance, the influence of the pile wall thickness on the bearing capacity is insignificant. When the top pile load is close to the bearing capacity of the pipe pile, the influence of the pipe pile wall thickness on the bearing capacity is greater.

Dynamic compressive and splitting tensile characteristics of rubber-modified non-autoclaved concrete pipe piles

Non-autoclaved concrete pipe piles are gaining attention as an environmentally friendly alternative to autoclaved concrete pipe piles. The purpose of this study was to investigate the changes in the impact resistance of a non-autoclaved concrete pipe pile with the addition of rubber. To this end, various volume fractions of rubber particles were used to replace the fine sand in the non-autoclaved pipe pile concrete (0%, 5%, 10%, 15% and 20%). The dynamic and static mechanical responses of rubber-modified non-autoclaved pipe pile concrete were explored through quasi-static and dynamic compression and splitting tensile tests. The results showed that (1) The tensile-compression ratio of the rubber-modified non-autoclaved pipe pile concrete increased with the rubber content, and the brittleness of non-autoclaved concrete was improved by adding rubber. (2) When subjected to impact load, rubber particles could absorb some of the impact energy, reduce the impact load on the aggregate, and prevented the aggregate from being crushed. (3) The impact toughness index and energy consumption ratio of non-autoclaved pipe pile concrete increased with the increase of rubber content. When the rubber content was 10%, the impact toughness index and energy consumption ratio of non-autoclaved pipe pile concrete were 52.2% and 51.2% higher than those of non-autoclaved pipe pile concrete without rubber particles, respectively, and its impact resistance was the best. The impact resistance of rubber-modified non-autoclaved pipe pile concrete was better than that of traditional autoclaved pipe pile concrete, and met the mechanical performance requirements of prestressed high-strength concrete pipe pile. It could be used as a new prestressed high-strength concrete pile material, which helped to reduce energy consumption in the production process of piles. The study provided parameter basis for the subsequent drop hammer impact test and numerical simulation of pipe piles.

Field Test Study on the Bearing Capacity of Extra-Long PHC Pipe Piles under Dynamic and Static Loads

Pretensioned prestressed high strength concrete (PHC) pipe piles are widely used in various engineering foundations, which have the advantages of high single pile bearing capacity, strong adaptability to geological conditions and high degree of construction mechanization. In order to study the vertical compressive bearing performance and settlement characteristics of ultra-long PHC pipe piles, high strain dynamic detections and static load tests were carried out on four PHC piles with a diameter of 0.9 m on site. It can be seen from the field test that the bearing capacity of the prefabricated pipe piles was time-dependent. By the end of the dynamic test, the bearing capacity of each test pile increased by 27% to 66%. The static load test also verified the rationality of the value of the restitution coefficient. Therefore, the final bearing capacity of the pile foundation can be predicted by using the high strain initial driving results and the restitution coefficient, which can reduce the repeated driving process, effectively save the cost and improve the engineering efficiency. Under 2.1 times the design load, the change range of the pile concrete modulus is from 37.5 GPa to 52 GPa, the change range of the pile side friction resistance is from 0 kPa to 97 kPa and the change range of the pile end to pile bottom load ratio is from 0% to 7.54%. During the test, the shaft friction and end bearing of the lower part of the piles were not fully mobilized. The shaft friction resistance, the end resistance and the movement behavior of the pile top and the end of the piles can provide parameter references for the subsequent design and construction of the piles.

Studies of nano-SiO2 and subsequent water curing on enhancing the frost resistance of autoclaved PHC pipe pile concrete

Autoclave curing will cause severe deterioration on the frost resistance of pre-stressed high-strength concrete (PHC) pipe pile. To clarify the frost resistance degradation mechanism of autoclaved PHC pipe pile concrete and obtain effective improvement measures, nano-SiO2 (NS) with cement replacement ratios of 0.5%, 1.0%, and 1.5% were adopted, and concrete specimens were fabricated and subjected to standard curing, autoclave curing, and autoclave curing + one week of subsequent water curing, respectively. Then, a rapid freeze-thaw cycle experiment was utilized to test their frost resistance. In addition, the micro-morphology and pore structure of different concrete were studied through scanning electron microscopy and nuclear magnetic resonance. The results indicate that the mechanisms of the degradation of autoclaved concrete in frost resistance are the increase of concrete porosity, harmful pore ratio, and concrete brittleness. Compared with standard curing, autoclave curing can result in 68.5% loss in the frost resistance of concrete. Through playing the filling and pozzolanic effects, NS can improve the compactness of autoclaved concrete and increase its frost resistance to a certain extent. Subsequent water curing can replenish water into concrete, promote the hydration of the residual unhydrated cementitious materials in concrete, enhance the compactness of concrete, and play a positive role in improving the frost resistance of concrete. The incorporation of 1.0% NS can enhance the frost resistance of autoclaved concrete by 66.6%, while the combination of 1.0% NS incorporation and one-week subsequent water curing can enhance the frost resistance by 89.2%. Exponential function can be used to simulate the frost resistance degradation of the autoclaved PHC pipe pile and predict its service life based on frost resistance.

Experimental Study on Bending Resistance of New Type Joint of Prestressed Concrete Pipe Pile

In the field of PHC pile joints, it is important that prestressed high-strength concrete pipe piles are referred to as PHC pipe piles. In conventional hoops, bamboo-like joints protrude from the pile joint position at the surface of the pile. Driving the pile in, disturbing the soil around the pile, and affecting the frictional resistance are serious issues. To address such issues, herein, a new type of clamping joint is proposed. A new method is presented to determine the size of the new joint that is flushed with the surface of the pile at the joint position. Bending resistance tests are conducted on four types of new joints for common pipe piles to study the deformation development process, bending bearing capacity, and damage characteristics of the new joints. Cracks are mainly distributed in the pure bending section and are approximately symmetrically distributed along both sides of the joint; there is no obvious cracking and damage in the joint until the pile cracks. Under the same bending moment, the deflection in the span of all specimens is greater than the deflection at the loading point.

Damage – Permeability analysis of pretensioned spun high strength concrete pipe piles based on stochastic damage model

In off-shore zones, the pretensioned spun high strength concrete (PHC) pipe piles are widely applied for its ability to provide high permeability resistance. However, one of the most applied pile-driving method of the PHC pipe piles is the hammer pile-driving method, and the piles are usually damaged due to the cyclical impact from the hammer. The damage in concrete will remarkably increase the permeability of the material, which will cause an early durability failure in the piles. By this means, a model that comprehensively relates the damage and permeability is firstly proposed under the framework of stochastic damage model in this study. By comparison to the experimental results, the proposed model is verified for its accuracy. And based on the proposed model, the engineering problem of damage - permeability performance of the PHC pipe piles of a construction site in Guangdong province is evaluated.

Durable life assessment of centrifugal stratified PHC piles in marine environment

This study proposes an analytical approach to assess the durable life of pre-stressed high-strength concrete (PHC) pipe piles exposed to the marine environment with consideration of centrifugal stratification and different end types. The durable life of the PHC pile is divided into two stages: the initiation stage for chloride penetration and the propagation stage for rust accumulation. To simulate the two stages, a two-layer composite cylinder diffusion model and a thick-walled ring mechanical model are developed based on the governing mechanisms. The proposed diffusion model is verified via comparisons with the numerical models with respect to chloride concentration under different stages. Then, extensive parametric studies based on the proposed method are performed to investigate the effects of end type, cover thickness, and steel bar diameter on the durable life of a PHC pipe pile. The results indicate that both increasing the cover thickness and using the closed-ended pile can significantly extend the durable life of a PHC pipe pile. Furthermore, the open-ended pile with a thinner mortar layer has a longer durable life, while the durable life of a closed-ended pile only slightly increases with a larger thickness of the mortar layer.

Field test research and design of a new heliostat support structure in coarse gravel

A solar power tower plant includes a solar tower and tens of thousands of heliostats, with the latter accounting for 40–50% of the total cost. To reduce heliostat costs, a new type of heliostat support structure (HSS) is proposed, consisting of a prestressed high-strength concrete pipe pile and cast-in-place concrete. With the performance and applicability of this structure unknown, full-scale field load testing of the proposed HSS on coarse gravel, subjected to lateral loads or torsion–lateral combined loads, was conducted. The results indicated that lateral load amplifies the rotation under torque and the proposed HSS for mirror arrays can provide sufficient rigidity to limit structural deformations within tolerable values under severe wind loading. Together with three-dimensional modelling, the performance of the proposed HSS was thoroughly investigated to facilitate the development of modified prediction methods for its lateral and torsional load responses. A detailed design procedure is proposed for the new structure, considering foundation deformations, bearing capacity and survival requirements. This study proved that the proposed HSS can improve the economic performance of solar power tower plants.

Static Load Test and Numerical Analysis of Influencing Factors of the Ultimate Bearing Capacity of PHC Pipe Piles in Multilayer Soil

Prestressed high-strength concrete (PHC) pipe piles have been widely used in engineering fields in recent years; however, the influencing factors of their ultimate bearing capacity (UBC) in multilayer soil need to be further studied. In this paper, a static load test (SLT) and numerical analysis are performed to obtain the load transfer and key UBC factors of pipe piles. The results show that the UBC of the test pile is mainly provided by the pile shaft resistance (PSR), but the pile tip resistance (PTR) cannot be ignored. Many factors can change the UBC of pipe piles, but their effects are different. The UBC of the pipe pile is linearly related to the friction coefficient and the outer-to-inner diameter ratio. Changes in the pile length make the UBC increase sharply. Low temperatures can produce freezing stress at the pile–soil interface. The effect of changing the Young modulus of pile tip soil is relatively small.