Permeable Pile Research Articles

Semi-numerical analysis of negative skin friction on permeable pile due to consolidation induced by piling

A semi-numerical approach is proposed to estimate the dissipation of excess pore water pressure and the development of negative skin friction at the normal impervious pile and the permeable pile after piling. An impeded drainage boundary associated with the opening ratio and opening size is introduced to simulate the drainage condition at the soil-permeable pile interface. In the proposed mathematical framework, analytical approaches are adopted to solve the linear equations, and numerical techniques are utilized to address the nonlinear problems so that the adaptivity and efficiency of the mathematical framework can be well balanced. Through comparisons with the field tests, the model tests, and the theoretical answers, the correctness and rationality of the proposed method are validated. Through a parametric study, the key design parameters of the permeable pile are investigated, and the following design tips are obtained: 1. The opening ratio plays the most important role in the drainage efficiency of the permeable pile; 2. Increasing the number of openings is preferred rather than increasing the size of openings, especially when the opening ratio is determined.

Analysis of Group Pile Bearing Modes of Permeable Pile Dam with Different Incoming Flow Angles

Based on ABAQUS finite element analysis software, the group piles and single piles under different incoming flow angles are compared and calculated, the horizontal bearing characteristics of the group piles of permeable pile dam under different incoming flow angles are analyzed, the pile-soil force is solved, and the change rules of the load-displacement characteristics, the displacement distribution of the pile body, and the distribution of the pile body bending moment are analyzed in detail. The study shows that: for the group piles with flow angles of 0° and 45°, the stresses from the upstream piles to the downstream piles tend to increase along the flow direction, and a stress concentration occurs at the downstream pile; for the group piles with flow angles of 90°, the stresses gradually increase from the central pile to the piles on both sides, and the stress concentration area is distributed at the outermost pile. With the increase of the incoming flow angle, the horizontal bearing capacity of the whole group of piles shows an increasing trend, but due to the effect of the group piles, the bearing capacity of the unit piles is smaller than that of the single piles; The displacements of the group piles at different incoming flow angles were greater than those of the single piles, and the turning points were all at about 12 m below the mud surface; With the increase of incoming flow angle, the group pile starts to change from rigid deformation to flexible deformation, the maximum bending moment of the pile body decreases, and the maximum value of the bending moment of the pile body occurs at the burial depth of 5 m. The maximum value of the bending moment of the pile body decreases with the increase of incoming flow angle.

Numerical Simulations of Effects of the Layout of Permeable Pile Groin Systems on Longshore Currents

Coastal permeable groins have been used to protect beaches from erosion for centuries. However, the hydraulic functioning of permeable groins has not been fully understood and their design heavily depends on engineering experiences. In this study, numerical experiments were executed to investigate the effects of layout configurations of a permeable groin system on longshore currents. The non-hydrostatic SWASH (Simulating WAve till SHore) model was employed to carry out the numerical simulations. Two data sets obtained from physical laboratory experiments with different permeable groin layouts on different slopes are used to validate the accuracy of the model. Then, the longshore current reduction by the permeable groin system with varying configuration parameters (e.g., groin spacing, groin length) was numerically investigated under different environmental conditions (e.g., a slight or a moderate wave climate). From the calculation results of numerical experiments, it is indicated that permeable groins function efficiently to reduce the maximal longshore current velocity under the condition that the groin length ranges from 84% and 109% of the wave breaker zone width. The longshore current reduction rate monotonously decreases with the increase in groin spacing; permeable pile groin functions best to reduce longshore current with the minimal groin spacing-groin length ratio 1:1 among the range between 1:1 and 2:1. When the groin spacing–groin length ratios are 1:1 and 1.5:1, the longshore current reduction is not sensitive to the investigated wave conditions in this study. When the spatial ratio is 2:1, the permeable pile groin system functions worse under a moderate wave climate than under a slight wave climate, from the view of longshore current reduction.

Characteristics and Mechanism of Local Scour Reduction around Pier Using Permeable Sacrificial Pile in Clear Water

To improve the local scour protection of the pier using solid sacrificial piles, a kind of permeable sacrificial pile filled with stones is put forward in this study. Four influencing factors, including the size of the filling gravel of the permeable sacrificial pile, the distance between the pile and pier, the diameter ratio D1/D (D is the diameter of the pier and D1 is the diameter of the pile.), and the submergence rate of the pile, are studied in clear water condition with indoor tests and numerical simulations. The test results show that it has the best reduction effect on the local scour of the pier when the filled gravel size is 0.2–0.25 D, the distance between the pile and pier is 3.0 D, the diameter ratio is 1.0, and the submergence rate is 0.8. Results of the numerical simulation show that the permeable sacrificial pile has a significant weakening effect on the downflow in front of the pile and the flow velocity around the pile. In the same conditions, the reduction effects of the permeable sacrificial pile and the solid sacrificial pile on the pier are similar, but the local scour around the permeable sacrificial pile is less than that around the solid one. The pressure difference outside and inside the permeable pile causes the water to flow in the direction perpendicular to the isobars. This significantly impacts the flow velocity, the vortex system, and the shear stress around the permeable sacrificial pile and pier, which leads to a huge decrease in the local scour depths. The maximum shear stress on both sides of the permeable sacrificial pile and the pier is about 1/2 and 1/4 of those around the solid sacrificial pile respectively. And the area with lower velocity and shear stress behind the permeable sacrificial pile is larger than the area behind the solid ones.

A semi-analytical solution for consolidation of ground with local permeable pipe pile

Aiming at optimization of drainage holes for permeable pile, a scheme of local pervious segment is introduced in the body of pipe pile to accelerate the dissipation of excess pore water pressure caused by pile driving. An axisymmetric consolidation model is established for a single local permeable pile in saturated clay. The semi-analytical solution is obtained using the boundary transform and integral transform methods. The effectiveness of the proposed solution is assessed by comparing with the results of degradation analysis, finite difference analysis and model test. Upon the successful calibration of the solution, the impacts of pervious segment parameters, geometric dimensions of pipe pile and soil physical parameters on the consolidation of soils around the pile are analyzed. Results show that local permeable pile can accelerate the soil consolidation based on the premise of structural strength of the pile body, and the acceleration effect is mainly in the early stage of consolidation. With the increase of pervious segment length and position, aspect ratio of pile, and soil permeability coefficient ratio, the benefit of local permeable pile is more apparent, which can provide reference for design.

Field monitoring of bearing capacity efficiency of permeable pipe pile in clayey soil: A comparative study

For clayey soil, an effective solution to accelerate pore water pressure dissipation after pile installation is using permeable pipe piles. But the differences in bearing capacity efficiency between permeable and normal piles are still unclear. In this paper, a series of load tests were conducted to compare their performance. The bare fiber Bragg grating (FBG) sensors were used to monitor and explore the pile-soil interaction process, together with pore water pressure and earth pressure cells. The FBG-based performance evaluation system provides an effective tool for the analysis of piles. The results show that the time required for the permeable pile to reach the ultimate bearing capacity was shorter than that of the normal one. The drainage holes did not lead to quality problems of the pile. The positive effect of drainage holes on the end-bearing resistance was gradually evident with time. This study provides valuable insight into the working mechanism of permeable pipe piles.

Novel mitigation techniques using base opening and permeable piles against sand liquefaction induced uplift for existing manholes

Soil liquefaction induced manhole uplift causes significant disruptions to vital lifelines following major earthquakes. In the past decades, remediation measures have been proposed to tackle this problem for newly constructed manholes. Nonetheless, mitigation measures for existing manholes were rarely reported, which leaves existing manholes facing high uplift risk in future earthquakes. Aiming to address this problem, this study proposes a series of mitigation measures, including (1) opening a drainage hole at the manhole base, (2) installing a smooth permeable pile under the manhole, and (3) installing a permeable pile with spiral wings under the manhole. The experimental results revealed that these three methods can mitigate manholes uplift to different extents. The drainage opening can mitigate the manhole uplift by releasing the pore water pressure on the manhole invert and draining water into the manhole chamber. The smooth permeable pile can further mitigate the manhole uplift with more drained water and greater retained sidewall friction due to the lowered liquefaction degree in the surrounding soil as a result of the extended drainage effect. However, the additional pull-out resistance expected from the spiral wings was of little contribution in view of the slight uplift difference comparing to the smooth permeable pile. The above observations are also validated with theoretical force equilibrium.

Mathematical characterization of pile–soil interface boundary for consolidation analysis of soil around permeable pipe pile

A permeable pipe pile is proposed to accelerate the dissipation of excess pore-water pressure through drainage holes around the pile circumference into the pile’s cavity. This investigation generalizes the permeable pile–soil interface as an impeded boundary, based on which a mathematical model for soil consolidation around the permeable pile is derived. Subsequently, the influence of opening pattern, drainage hole-to-pipe pile radius ratio, and opening ratio on the consolidation efficiency is numerically investigated. A total of 240 numerical cases with different drainage hole-to-pipe pile radius ratios, opening ratios, and hydraulic conductivity ratios are calculated to determine the permeable pile–soil interface parameter using back-analysis, and an approximate expression for interface parameter is obtained. Comparing against experimentally measured excess pore-water pressure dissipation, the proposed technique with impeded drainage boundary can provide good evaluations for drainage characteristics at the permeable pile–soil interface and consolidation behavior of the surrounding soil. It is found that the spatial distribution pattern of drainage holes has negligible influence on the consolidation efficiency. Increasing the opening ratio (with constant opening size) or reducing the drainage hole-to-pipe pile radius ratio (with constant opening ratio) can both accelerate the consolidation efficiency.

Numerical modelling of hydrodynamics of permeable pile groins using SWASH

This paper focuses on a specific form of groins, Permeable Pile Groins (PPGs), consisting of a single or double rows of wooden piles. With only few experiments and simulations available to study the hydraulic functioning of PPGs, the correlation between the effectiveness and the characteristics of the groin system has yet to be fully understood. This paper presents the application of SWASH, a non-hydrostatic wave-flow model to simulate flow fields affected by PPGs. The SWASH model was calibrated to correctly reproduce longshore current fields in the laboratory. Then, introducing PPGs in the model, the simulation results are compared with available experimental measurements to investigate current-PPG interaction. The simulation results, which generally agree well with the measurements, show that PPGs hardly attenuate wave energy but considerably retard longshore currents within the groin fields. Rip currents are predicted to develop at both flank sides of each pile groin, due to local positive water level gradients toward the pile groins.

Seismic dynamic response analysis of permeable breakwater on piled foundation considering pile-soil interaction

In order to discuss the seismic response of pile foundation permeable breakwater structure under different working conditions, the dynamic implicit module in finite element software ABAQUS is used to analyze the seismic dynamic response of pile foundation permeable breakwater. Considering the nonlinear characteristics of pile-soil interaction the breakwater is simulated under different seismic intensity conditions. The acceleration, bending moment of pile foundation are analyzed by time-history analysis method. The influence of pile diameter on the whole structure is compared. The results show that the stronger the earthquake is, the more obvious the overall dynamic response of the structure is. The bending moment of pile body decreases first and then increases. The wider the diameter of pile foundation, the greater the stiffness of the whole structure, resulting in an increase in the seismic force received by the structure. Compared with the static load, the influence of earthquake on the permeable pile breakwater can not be ignored.

REVISITED HYDRAULIC FUNCTIONING OF PERMEABLE PILE GROINS

Since 1965, a new type of permeable groins (or ‘pile screens’ referred to Bakker et al.,(1984)), which consist of wooden pile rows with a high permeability, have been widely used to protect the coastline from recession in the Netherlands, especially at southwestern coastline. However, the hydraulic functioning of such structures has not been understood well compared to traditional impermeable pebble mound groins. As the wooden pile groins become older and the maintenance costs increase, the issue of their effectiveness has become of importance, while no serious research has been undertaken. This paper tries to tackle this issue. Based on experimental data which was obtained at Delft Hydraulics (Hulsbergen and Horst, 1973), the functioning of pile groins has been revisited and analyzed by an advanced numerical model. The simulations give deeper insights into the effectiveness of permeable pile groins under well controlled laboratory conditions.

Compressive and flexural behaviour of reinforced concrete permeable piles

Abstract Driven piles generate excess pore water pressures in the surrounding soil, where a full dissipation of these pressures may take a very long time. Measures are therefore sought to accelerate soil consolidation. The concept of permeable pile with drainage holes around the circumference of pipe pile could serve this purpose by providing drainage paths. However, the structural integrity of permeable pile may be deteriorated due to these openings. This paper presents the results of uniaxial compression and flexural tests on permeable and normal pile specimens. The influence of concrete strength and pattern of drainage holes in terms of diameter, total number and layers on the ultimate compressive strength is investigated. The crack pattern, deflection profile and concrete strains are measured for both normal and permeable piles. It has been found that drainage holes could cause the reduction in ultimate compressive strength, but the measured values are still far greater than design estimations. Moreover, the permeable piles have higher flexural capacity than the normal piles due to the stress redistribution.

Reply to comment by D. Carbone and D. Patanè on “Multidisciplinary investigation on a lava fountain preceding a flank eruption: The 10 May 2008 Etna case”

Reply to comment by D. Carbone and D. Patanè on “Multidisciplinary investigation on a lava fountain preceding a flank eruption: The 10 May 2008 Etna case”

Research on Key Technologies of River Rapid Survey by ADCP

ADCP is convenient for field measurements , But the work of data extraction is heavy , and the flow field distribution map and topographic contour map can’t get from the system software directly , so the rapid extraction of measurement data and mapping technology are two key technologies in river rapid survey by ADCP. This paper studies these two issues , proposed solutions, applied these technologies to the measurement of Nanguotou Permeable Pile Groynes on the Yellow River, and achieved satisfactory results.

Permeability effects of single groin on flow characteristics

The results of an experimental study on the flow characteristics around a groin structure of various geometries and permeabilities are presented. The impermeable rectangular, the permeable pile, and the triangular-shaped groins are considered. The velocity fields were observed using large-scale particle image velocimetry, whereas the maximum velocities were measured using an acoustic Doppler velocimeter. An increased velocity at the groin tip and a broad range of the recirculation zones were observed for the impermeable rectangular groin. For the permeable pile groin, the velocity at the groin tip, the vortex strength, and the scale of the recirculation zone tended to decrease as the openings between the piles increased. Also, the triangular-shaped groin formed narrower and longer recirculation zones compared with the permeable pile groin of identical cross-sectional flow area. These quantitative findings on the flow patterns for groins of various geometries and permeabilities are practically important to design and evaluate their performance in field applications.

A depth-averaged two-dimensional model for flow around permeable pile groins

Results of a comparison between in-situ experiment and numerical modelling for flow around permeable pile groins were presented. The groin sets consisted of porous-fence piles with a diameter of 1.0 m and were conducted in the Laonong River, Southern Taiwan. A numerical model that solved depthaveraged RANS (Reynolds-averaged Navier-Stokes equations) and the continuity equation was developed to simulate the flow around the permeable pile groins. The turbulent effects were determined by the standard e k turbulence model. Drag forces exerted by the flow on the permeable pile groins were considered by adding source terms into momentum equations. The numerical predictions showed good agreement with the experimental results. The present model captured important flow features that were critical for characterizing the engineering design. Furthermore, the influence of different discharges on the hydrodynamic characteristics of permeable pile groins was investigated by using the present model. When the flow passed through the permeable pile groins, flow velocity reduced downstream of the groins and the water depth dropped significantly in the stream wise direction. It was observed that the levels of the flow velocity and water depth reduction decreased as the flow discharge increased. This was attributed to extra momentum transfer between the jet flows passing through the gaps between the permeable pile groins and the flow just behind the permeable pile groins.

Field Applications on Electrokinetic Reactive Pile Technology for Removal of Cu from In-situ and Excavated Soils

This paper presents a preliminary field application of an electrokinetic reactive pile technology for removal of copper (Cu) from in-situ and excavated sorted soils. The electrokinetic reactive pile is composed of an electrokinetic remediation and permeable reactive pile system. Field electrokinetic reactive pile tests were carried out for the treatment of copper contaminated soil in-situ and sorted soil from buried waste material of this landfill. From the preliminary field investigations, the applicability of the electrokinetic reactive pile technology was evaluated. It was found that electrokinetic reactive pile system would be effective for removal of copper from in-situ and sorted soils.

Study on Three-Dimensionality of Flows around Impermeable Dike and Permeable Pile Dike

Study on Three-Dimensionality of Flows around Impermeable Dike and Permeable Pile Dike

Permeable Pile Groins

Permeable pile groins have been built on the southern shores of the Baltic Sea in large numbers for a century and a half, yet no explanation has been found in the literature on how these function. It is shown that pile groins act as a hydraulic roughness on the longshore current and that their effect on waves is negligible. By reducing, but not blocking, the littoral current, the velocity differential between the velocity seaward and in the pile-groin fields is smaller than with impervious groins. Hence, the circulation in the groin field due to the fluid drag at the seaward boundary is weaker and is concentrated mainly in the velocity interface in the form of small eddies. The reduced littoral current velocity in the pile-groin fields leads to a reduction of turbulence produced at the bed by the wave-current interaction, to a reduced amount of sediment suspended, and to a thinner layer of suspended sediment. Hence, the amounts of sediment advected by superimposed currents are reduced. The reduction is most effective for erosive-wave conditions and enables trapping or holding of sediment until the continuity of littoral transport is reestablished and the cross-shore transports balance over time.

Model Test for Reflection Coefficient of Wave Dissipating Pile Support Structures

A wave dissipating pile support sutructure with a permeable pile wall and wave chamber has the advantage of low wave reflection. Experiments were conducted to investigate characteristics of the reflection coefficients for structures. The results of the experiments indicate that the reflection coefficients are influenced by pile section type. A practical calculation method is derived for the prediction of refrection coefficients of the structure on the basis of Tanimoto's theory for the wave dissipating caisson.