PHC Pile Research Articles

Experimental and numerical investigations on the mechanical response of full-scale PHC pile foundations for solar power generation

Experimental and numerical investigations on the mechanical response of full-scale PHC pile foundations for solar power generation

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.

Exploring the Utilization of PHC Pile Waste Concrete as Filler in Asphalt Mastics.

Using solid waste to replace limestone filler in asphalt concrete can not only reduce the cost of road construction, but also improve the utilization rate of solid waste. In this study, PHC pile waste concrete (PPWC) was innovatively used to replace limestone filler in asphalt mixture and its effect on the physical and rheological properties of asphalt mastics was studied. Firstly, PPWC was ground into filler particles with a diameter less than 0.075 mm. The physical properties, particle characteristics and chemical composition of PPWC filler and limestone filler were compared. Asphalt mastics were prepared with different filler-asphalt volume ratios (20%, 30% and 40%) and the physical properties, high-temperature rheological properties and low-temperature cracking resistance of asphalt mastics were tested. The experimental results showed that the surface of PPWC filler is rougher and has lower density and smaller particle size than limestone filler. When the filler content is the same, PPWC filler asphalt mastics have lower penetration and ductility, higher softening point than limestone filler asphalt mastics, and the viscosity of PPWC filler asphalt mastics is more sensitive than limestone filler asphalt mastics. PPWC filler asphalt mastics demonstrated superior high-temperature stability, but poorer low-temperature cracking resistance compared to limestone filler asphalt mastics. In conclusion, PPWC fillers can be used to replace limestone fillers in asphalt mixtures. The finding of this study will provide a new solution for the construction of eco-friendly roads.

Experimental study on the bearing property of the composite foundation with stiffened deep cement mixing pile based on the PHC pile

Inserting a prestressed high-intensity concrete pipe pile into a cement–soil mixing pile can form a new composite pile named the composite foundation with stiffened deep cement mixing (SDCM) pile. The Huanghuai alluvial stratum in China is selected to carry out the in situ test for the SDCM pile, and the bearing capacity of the SDCM pile is tested by the slow-speed maintenance load method. The results show that for an SDCM pile with dense silt and fine sand as the bearing layer, the characteristic value of bearing capacity can reach 2,300 kN, which means an SDCM pile with a length of 8.0 m meets the load requirement of a general high-rise building. Further analysis shows that the SDCM pile saves more than 40% of the cost compared with the traditional CFG pile and has better quality control advantages at the same time. This research can provide basic data and design references for similar site foundation projects.

Seismic performance of pretensioned centrifugal spun concrete piles with steel strands

Pretensioned centrifugal spun concrete piles with steel strands (PSC piles) have been developed to improve the seismic performance of the piles by using higher strength and more ductile prestressing steel strands, instead of the more traditional high strength steel bars. This paper presents a systematic evaluation of the seismic behavior of PSC piles by means of full-scale test and finite element (FE) simulation. Lateral cyclic loading tests have been carried out on three full-scale PSC pile specimens subjected to different axial compressive forces. The performances of test specimens, including cracking pattern, lateral bearing and deformation capacities, stiffness degradation, energy dissipation and failure mode are examined. The performances of PSC piles are subsequently compared with piles reinforced by high strength steel bars (referred as PHC piles) tested in a previous study. A detailed FE model was developed to simulate the hysteretic behavior of PSC piles using DIANA. This model was validated against test results and then used for parametric analyses. The effects of four key design parameters, in terms of axial force ratio, steel strand ratio, prestressing level of steel strands and concrete wall thickness, on the cyclic behavior of PSC piles have been investigated. The results show that all PSC pile specimens are dominated by the bending damage, and their cyclic behavior and failure mode are influenced significantly by the axial force. The lateral bearing capacity increases remarkably while the deformation capacity generally decreases with the increase of the axial force ratio. The PSC pile failure is mainly dominated by the tensile rupture of steel strands under lower axial force ratios, while concrete crushing under higher axial force ratios. Compared with PHC piles, PSC piles with a smaller reinforcement ratio demonstrate better overall seismic performance, especially ductility, under low to medium axial force ratios, as in such cases the high ductility of steel strands can be fully utilized. Further improvement of the seismic performance of PSC piles under higher axial force ratios can generally be achieved by increasing concrete wall thickness.

Eco-Economic Performance Estimation Method for Pretensioned Spun High-Strength Concrete Pile Installation

Pile installation has an environmental impact through its various processes ranging from raw material extraction to construction. In addition, the environmental performance, productivity, and cost of pile installation depend on the construction plan. Therefore, the chain of activities must be considered when analyzing the sustainability of pile installation. A rational construction plan must carefully examine the factors that affect the productivity and sustainability of pile installations. This study presents a method for evaluating eco-economic performance by analyzing the resource utilization and processes of PHC pile installation. First, a process modeling technique, wherein details are broken down to the work task level, based on energy consumption and resource cost, is proposed. Second, a simulation method that calculates the eco-economic performance of the PHC pile process and resources (e.g., equipment) is presented. Third, a quantitative comparison of durations, costs, and emissions resulting from simulation, estimation based on the CSPR (Construction Standard Production Rate) and IUC (Itemized Unit Cost), site contract, and actual construction is presented. The results reveal that the method effectively reflects the prediction of duration, cost, and carbon emissions generated in the real world during the construction planning stage.

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.

A Study on the Field Experiment and Marketability Analysis of PHC Pile and Steel Pipe Pile Head Cutting Robot

A Study on the Field Experiment and Marketability Analysis of PHC Pile and Steel Pipe Pile Head Cutting Robot

A Study on Development of PHC pile driving force increase device on soft ground

A Study on Development of PHC pile driving force increase device on soft ground

Point Foundation (PF) method: Principles and recent research findings

Conventionally, cement deep mixing (CDM) columns are designed to have constant diameters over the improved depth as this facilitates the construction procedures. However, this design pattern may be inefficient in cases of spread footings or shallow foundations. This paper first briefly introduces principles, construction procedures and quality control techniques of an innovative CDM method that can create head-enlarged column, named as Point Foundation (PF). The method is practically implemented with a specific binder that is environment-friendly and more effective in strength enhancing compared with the common binder as cement. Static load tests on three instrumented PF columns indicate that the variation trend of induced vertical stress profile along the columns in general is similar to that under the centre of shallow footings on elastic soil medium. However, the stress profile in the (semi-rigid) PF columns is larger than that in elastic soil but less than that in (rigid) PHC pile. This confirms the load transfer mechanism along semi-rigid columns like CDM/PF. Test results also indicate that at the depth of one to two times head diameters the induced stress remains just 20% the applied pressure. Findings on the trend of the induced vertical stress in the columns suggests that the settlement of common shallow footings on CDM/PF column-reinforced grounds should be evaluated using 3D condition taking into account the fact that the induced stress decreases with depth.
 Keywords:
 ground improvement; Point Foundation (PF); tapered cross section; load transfer mechanism; load-settlement behavior.

Study of seismic behavior of PHC piles with partial normal-strength deformed bars

Nine PHC piles with partial normal-strength deformed bars were prepared in present study, and cyclic loading tests were implemented to evaluate these piles’ seismic performance. The influence of the axial compression ratio and the amount of normal-strength deformed bars on failure modes, crack patterns, strength, stiffness, and ductility were examined. The test findings indicate that the change of axial compression ratio has a noticeable influence on the failure mode of PHC piles. A larger axial compression ratio results in a higher cracking bending resistance, ultimate bending resistance, and initial stiffness, but the propagation heights of flexural cracks decrease as the axial compression ratio increases. Furthermore, increasing the amount of normal-strength deformed bars causes a slight decrease in ductility. Finally, a calculation formula was proposed to predict the flexural capacity of PHC piles with partial normal-strength deformed bars.

Study on Seismic Performance of Improved High‐Strength Concrete Pipe‐Pile Cap Connection

Four prestressed high‐strength concrete pile‐ (PHC pile‐) pile cap connections under low‐cycle loading were tested to study the test phenomena, failure modes, hysteretic performance, ductility, and bearing capacity. The PHC piles were reinforced with steel fiber and deformed bars and CFRP. The tests results showed that the connections were damaged by bending. The concrete of the caps were squeezed to be crushed. The concrete of connection was crushed and formed a hinge joint that resulted in the connection rotating unrestricted, and the rotation capacity of connection increased. The PHC pile reinforced with steel fiber and deformed bars can improve the displacement ductility of the connections. The finite element software ABAQUS was used to simulate the nonlinear behavior of pile‐cap connections. The prediction agreed relatively well with the experimental results. The stress and strain of specimens were studied. The connections should be designed with enough rotating capacity and make sure the cap will not be damaged by squeezing or prying due to the rotation of pile end.

Flexural and shear behavior of large diameter PHC pile reinforced by rebar and infilled concrete

The purpose of this paper is to provide an experimental and analytical study on the reinforced large diameter pretensioned high strength concrete (R-LDPHC) pile. R-LDPHC pile was reinforced with infilled concrete, longitudinal, and transverse rebar to increase the flexural and shear strength of conventional large diameter PHC (LDPHC) pile without changing dimension of the pile. To evaluate the shear and flexural strength enhancement effects of R-LDPHC piles compared with conventional LDPHC pile, a two-point loading tests were conducted under simple supported conditions. Nonlinear analysis on the basis of the conventional layered sectional approach was also performed to evaluate effects of infilled concrete and longitudinal rebar on the flexural strength of conventional LDPHC pile. Moreover, ultimate strength design method was adopted to estimate the effect of transverse rebar and infilled concrete on the shear strength of a pile. The analytical results were compared with the results of the bending and shear test. Test results showed that the flexural strength and shear strength of RLDPHC pile were increased by 2.3 times and 3.3 times compared to those of the conventional LDPHC pile, respectively. From the analytical study, it was found that the flexural strength and shear strength of R-LDPHC pile can be predicted by the analytical method by considering rebar and infilled concrete effects, and the average difference of flexural strength between experimental results and calculated result was 10.5% at the ultimate state.

软弱土地区PHC管桩复合地基加固参数研究

软弱土地区PHC管桩复合地基加固参数研究

Development of all-in-one attachment-based PHC pile head cutting robot

ABSTRACTPHC pile head cutting is an essential operation in foundation works, as it is needed to level the pile foundations. However, as it involves workers manually cutting the PHC pile with a grinder, the PHC pile head cutting process has several challenges with regard to safety, convenience, productivity, and quality. To address such problems, in this study, we define the core element technologies and automated work processes of an all-in-one attachment-based PHC pile head cutting robot that allow a series of operations to be performed in sequence – recognizing a cut-off line on PHC piles; cutting them; and separating, lifting, transporting, and unloading the severed top parts of the piles – without the need to involve workers onsite. Additionally, a prototype of the robot is developed and subjected to performance evaluation and productivity analysis. The results of the performance evaluation and productivity analysis of the conventional and automated methods performed using Web-CYCLONE simulations indicate that the automated method can improve the productivity by 3.13% compared with the conventional method. It is anticipated that when deployed onsite, the proposed robot can not only increase the productivity but also improve the convenience and quality of work at the PHC pile head cutting job site.

Study(IV) on the Development of Charts and Formulae Predicting Allowable Axial Bearing Capacity for Prebored PHC Pile Socketed into Weathered Rock through Sandy Soil Layer - Field Verification of Long-term Allowable Compressive Load of PHC Piles by Analyzing Pile Load Test Results -

Study(IV) on the Development of Charts and Formulae Predicting Allowable Axial Bearing Capacity for Prebored PHC Pile Socketed into Weathered Rock through Sandy Soil Layer - Field Verification of Long-term Allowable Compressive Load of PHC Piles by Analyzing Pile Load Test Results -

Case Study on Design Efficiency and Bearing Capacity Characteristics of Bored PHC Piles

Case Study on Design Efficiency and Bearing Capacity Characteristics of Bored PHC Piles

Erratum for “Effect of Open-Ended PHC Pile Installation during Embankment Widening on the Surrounding Soil” by Guowei Li, Andrew Cudzo Amenuvor, Yuzhou Hou, Xiaocen Lu, Jiantao Wu, and Thang Ngoc Nguyen

Erratum for “Effect of Open-Ended PHC Pile Installation during Embankment Widening on the Surrounding Soil” by Guowei Li, Andrew Cudzo Amenuvor, Yuzhou Hou, Xiaocen Lu, Jiantao Wu, and Thang Ngoc Nguyen

Site test study of pile-soil stress ratio of composite foundation in karst area

Aiming at the special geological conditions in Karst areas, the pile-soil stress ratio of composite foundation is analyzed. According to carry out the field test of composite foundation in Karst area, soil pressure boxes are arranged to measure the stress of piles and soil at the same time. As the load increased, the variation trend of the pile-soil stress ratio of composite foundation is analyzed. On the basic, the pile-soil stress ratio is compared with non-karst area. The test result showed that both the pile-soil stress ratio of PHC piles and high pressure jet grouting piles increase. The increase of the PHC piles is more obvious. The pile-soil stress ratio of PHC piles is larger than high pressure jet grouting piles. The main reason is that the strength of cement-soil mixed piles is lower. The high pressure jet grouting piles plays an important role in improving soil bearing capacity between piles and supporting the side abutment pressure of PHC piles in composite foundation. It is shown that the stress concentration is more obvious in karst area.