Pile Structure Research Articles

The effect of antifreeze reagent on seasonal frozen soils

The design, construction, and maintenance of pile foundations are dependent on special weather conditions in Northern and Central part of Kazakhstan. The winter months in these areas are very long which starts from November to March and the air temperature usually reaches – 40-50°C. These circumstances lead to the seasonal freezing ground, special physical behavior of soil, physical properties of construction materials. The main problem of pile driving in winter is frozen ground which is difficult to excavate and driving. Moreover, the Static Load Tests for estimating the bearing capacity of pile foundations do not show accurate records in frozen soil. To solve the problems mentioned above, a special antifreeze composition has been developed and established its protective effect against soil freezing in winter. The implementation of the proposed method leads to a high productivity of driving reinforced concrete piles without the risk of their destruction. This eliminates the need for additional drilling works and more powerful and expensive rock drills, if the soil is protected from freezing. According to a special formula, the optimal mass of antifreeze is calculated, which allows protecting the soil without harming not only the soil, but also the structure of the concrete pile and the environment. During the static load test, piles driven into soil that had been covered with antifreeze has showed more accurate bearing capacity data. Scientific and experimental studies have established that antifreeze reduces the compressibility of frozen soil.

Reduction of propeller jet flow scour around a pile structure by using collar plate

In this study, the effect of the collar plate usage on local scour around a pile due to propeller jet flow was investigated experimentally. Experiments were carried out for unconfined conditions, only existence of a pile and a pile with collar plate. Three different collar plate widths (W) and two different locations of the collar plate with respect to the seabed (hc) were used to determine the effect of the collar plate on scour. Three different rotational speeds were used and scour around a pile was measured by using an Acoustic Doppler Velocimeter Profiler (ADVP). Since the experiments were completed before reaching the equilibrium state, present study can be considered as a short-term study. The results of the experimental studies show that the amount of reduction of scour around a pile is sensitive to the collar plate width and location of the collar plate. A collar plate application is an effective way for reducing scour around a pile. The most effective type of collar plate was determined as a condition in which W/D and hc/y0 are equal to 3 and 0, respectively. The amount of reduction in scour around a pile was observed as 75%.

Centrifuge study on the use of protective walls to reduce tunnelling-induced damage of buildings

Tunnel excavation in urban areas causes ground movements that could damage existing nearby piled structures. In practice, to protect structures from tunnelling-induced damage, a stiff protective wall can be constructed between the tunnel and the adjacent piled structure. In this paper, results from four hybrid geotechnical centrifuge tests (where data are coupled between the centrifuge and numerical models) are used to quantify the effect of protective walls on reducing the impact of tunnelling on an adjacent framed building with four piles. Two protective walls with different embedded depths are considered: a ‘shallow’ wall with its toe at the tunnel axis depth and a ‘deep’ wall with its toe below the tunnel invert. Compared to the ‘no-wall’ case, the ‘deep’ protective wall is shown to significantly reduce uneven pile settlements, structural distortions, and load transfer (through the building) between piles; the ‘shallow’ wall is shown to have little benefit. Data from the instrumented walls and piles are used to explain the dominant mechanisms at play and investigate how the load is redistributed within the piles.

Determination of concreting quality of bored piles by CHA method

In the presented article, the authors consider the issues of quality control of bored piles in the practice of bridge construction. The importance of quality control of these pile structures is emphasized. The basic requirements for quality control in the production of construction works and their acceptance are presented. A description of the control method is given. As a practical example, the results of quality control of the execution of bored piles by the method of cross well ultrasonic scanning at the bridge over the river Chusovaya. An assessment of the state of bored piles after testing is given.

Investigating the Influence of Structure and Heterogeneity in Waste Rock Piles on Mass Loading Rates—A Reactive Transport Modeling Study

Placement methods and material availability during waste rock pile (WRP) construction may create significant heterogeneities in physical and geochemical parameters (such as grain size, permeability, mineralogy, and reactivity) and influence the internal pile structure. Due to the enormous scale of WRPs, it is difficult to capture the influence of heterogeneities on mine drainage composition and evolution. Although laboratory- or field-scale experimental studies have provided much insight, it is often challenging to translate these results to full scale WRPs. This study uses a numerical modeling approach to investigate the influence of physical and chemical heterogeneities, structure, and scale on the release of acid rock drainage (ARD) through 2D reactive transport simulations. Specifically, the sensitivity of drainage quality to parameters including grain size distribution, sulfide mineral weathering rates, abundance and distribution of primary minerals, and pile structure as a function of construction methods are investigated. The geochemical model includes sulfide oxidation, pH buffering by calcite dissolution, and ferrihydrite and gypsum as secondary phases. Simulation results indicate that the implications of heterogeneity and construction method are scale-dependent; when grain size distribution trends observed in a pile's core are applied to the entirety of a pile, results between push- and end-dumping methods vary substantially—however, predicted drainage for different construction methods become more similar when features such as traffic surfaces, structural variation, and multiple benches are also considered. For all scales and construction methods investigated, simulated results demonstrate that pile heterogeneity and structure decrease peak mass loading rates 2 to 3-fold, but cause prolonged ARD release compared to the homogeneous case. These findings have implications for the economics of planning water treatment facilities for life of mine and closure operations.

Physical model on effects of tunnelling towards single piles under zoned of influence

Tunnel excavation usually will causes soil redistribution and settlement. Hence, for urban areas where large building used pile for foundation, tunnelling might affect the pile integrity. Engineers pose great role in order to correctly estimating the stress changes onto pile structures. It is particularly vital to estimate the tunnelling effects when new tunnels are to be built near an existing pile. Therefore, this paper presents a physical modelling to investigate the tunnel-pile-soil interaction. Sand box test with pile and tunnel model was developed to imitate the field condition. The laboratory testing conducted with constant parameter tunnel cover to tunnel diameter ratio of 2.5 with pile to tunnel distance of 1.5 of tunnel diameter. Two rate of tunnel excavation were carried out. Laboratory tests determined the longitudinal and transverse ground surface settlement induced by tunnelling, as well as the movement and induced bending moment on a single pile foundation. For validation, initial results were compared with previous findings and shows an agreement. Further test then conducted with higher tunnelling speed. With higher speed, it was found that surface settlements, pile movements and bending moment are more affected.

Monitoring and Analysis of Pore and Earth Pressure at the Pile Surface Using Piezoresistive Silicon Pressure Transducers

The piezoresistive silicon pressure transducers based on the piezoresistive effect have demonstrated their potential in the accurate monitoring of pressure. However, their usage in the pore and earth pressure monitoring at the pile surface under hydraulic jacking has not yet been explored. In this study, two self-made model piles (one is a closed-ended pile and the other is an open-ended pile) were instrumented with piezoresistive silicon earth transducers and pore pressure transducers and then driven into the soil using a hydraulic jack. A comprehensive investigation was first carried out for the structure of the model piles, the installation procedure of the transducers, and the composition of the test system. The pore and earth pressure measurements of the transducers were used for the evaluation of the distribution of the pore pressure, excess pore pressure, radial earth pressure, and radial effective earth pressure. The model test results indicate that the piezoresistive silicon pressure transducers are suitable for monitoring the pore and earth pressure at the pile surface during jacking. In addition, the pore pressure, excess pore pressure, radial earth pressure, and effective radial earth pressure along the test piles were affected by the penetration depth and the pile end form.

EXPERIMENTAL STUDY ON THE INTERACTION OF SINGLE PILE AND CALCAREOUS SOIL SUBJECTED TO CYCLIC LOAD

This paper presents the results of an experimental study on the resistance of steel pipe pile in calcareous soil. The authors conducted experiments with repetitive static loads acting on a test pile, linked measuring heads to determine pile top displacement and axial deformation of the pile. The obtained results show the interaction of steel pipe piles and calcareous soil under subjected to cyclic load by the ideal elastic and plasticity model; friction formed by the relative displacement between pile structure and calcareous soil subjected to axial cyclic load reaches the limit state when displacement is 2.5 mm.

“Effectiveness Of Cfg Pile-Slab Shape On Smooth Soil For Supporting Excessive-Pace Railway Embankment”

Reducing the settlements of smooth foundation efficiently is a crucial problem of excessive-pace railway creation in China. The new CFG pile-slab structure composite foundation is a floor remedy method that is carried out on CFG pile basis and pile-slab structure composite basis. Based on the revel in of constructing Beijing-Shanghai excessive-pace railway in China, the settlement-controlling effect, the settlement distribution legal guidelines and 3 key influence elements for structural shape of latest CFG pile-slab structural foundation are studied by the use of physical model exams and numerical simulations. The research results on this look at imply that the piles and soil bearing capacities of the new CFG pile-slab shape can be positioned into complete play due to the “load dispensing” function of slabs. The settlement decreasing effect of the new CFG pile-slab shape is first rate and can meet the requirements of high-pace railway creation. The affected location of engineering load has a depth over 18.Seventy five m and horizontal period of 7.Five m nearing the embankment slope toe. The parametric observe presents the optimalizing structural form for high-quality agreement-controlling effect. The bodily version test results display precise concordance with the numerical simulation effects. The mixture of bodily version assessments and numerical simulations justifies the usage of this version in geotechnical engineering practices.

DETERMINATION OF RATIONAL PARAMETERS OF SUPPORTING STRUCTURES MADE OF SOIL-CEMENT PILES ON LANDSLIDE-PRONE SLOPES

Purpose. The article proposes a method for determining the rational parameters of supporting structures made of soil-cement piles on landslide-prone slopes. Methodology. To achieve this purpose, the authors performed comparative calculations of finite-element models of landslide-prone layered slope with the arrangement of supporting structures of soil-cement piles: vertical, located at an angle to the vertical axis, combined with a concrete grillage, without grillage, with different diameters, with different distances between piles, but of the same length, which is justified by the location determined by preliminary calculations of the sliding surface. Findings. According to the results of calculating the contact problem of the interaction of the soil mass and the supporting structure, the regularities of formation of strength and stability of the reinforced landslide-prone slope were obtained, which makes it possible to predict its geomechanical stability depending on the possible location of the sliding surface curve. The method of increasing the stability coefficient of the soil slope depending on the variation of the parameters of the soil-cement supporting pile structure is substantiated. Numerical calculations substantiate the parameters of soil-cement pile supporting structures – the length of the piles, their diameter, the distance between the piles, the angle of their inclination and the feasibility of combining the piles with a concrete grillage. Originality. For the first time, the formation regularities of strength and stability of soil-cement supporting structure for strengthening the landslide-prone slopes are obtained, which makes it possible to predict their geomechanical stability depending on the possible location of the sliding surface curve. For the first time, the dependences of changes in absolute displacements, relative deformations, coefficients of strength, stability, as well as Mises stresses in the elements of supporting structures of soil-cement piles on the angle of their inclination, distance between piles and the presence of a concrete grillage that joins them. Methods for assessing and predicting the landslide danger of soil slopes were further developed, which allowed to substantiate the method of increasing the strength coefficient depending on the variation of the parameters of the soil-cement supporting structure. For the first time, the parameters of the method of increasing the stability of landslide-prone slopes with pile supporting structures based on the complex mathematical and centrifugal modeling using real landslides and similarity criteria are substantiated. Practical value. The authors have developed and patented a method of strengthening landslide slopes with the help of soil-cement piles, combined with a concrete grillage, located perpendicular to the movement vector of the landslide body.

Research on Grouting Construction of Icebreaking Cone Structure of Single Pile in Dalian Offshore Wind Power Project

Introduction The icebreaking cone structure is a unique structure of the offshore wind power single pile foundation structure in north. The installation of the icebreaking cone is one of the key points and difficulties in the construction of the single pile foundation. The grouting connection technology solves this problem through assembled construction successfully. For the first time in China， a single pile icebreaking cone structure is used in an offshore wind power project in Dalian. Method Supported by the engineering practice of the project’s icebreaking cone grouting construction he critical technique of single pile icebreaking cone grounding construction was studied including installation preparation， grouting material selection， grouting pipeline design and optimization， grouting plugging and grouting construction quality control etc. Result In this study， by using Ugrount® SKG-V， self-developed high-strength grouting material， the small-scale containerized integrated marine wind power grouting equipment and the self-developed underwater grouting technology， the material and construction performance had met the requirements， and the grouting connection between single pile icebreaking cone structure and single pile was successfully completed for the first time. Conclusion This material and technology are expected to be widely applied in the single pile foundation structure of offshore wind power in northern China.

Sortase-assembled pili in Corynebacterium diphtheriae are built using a latch mechanism

Gram-positive bacteria assemble pili (fimbriae) on their surfaces to adhere to host tissues and to promote polymicrobial interactions. These hair-like structures, although very thin (1 to 5 nm), exhibit impressive tensile strengths because their protein components (pilins) are covalently crosslinked together via lysine-isopeptide bonds by pilus-specific sortase enzymes. While atomic structures of isolated pilins have been determined, how they are joined together by sortases and how these interpilin crosslinks stabilize pilus structure are poorly understood. Using a reconstituted pilus assembly system and hybrid structural biology methods, we elucidated the solution structure and dynamics of the crosslinked interface that is repeated to build the prototypical SpaA pilus from Corynebacterium diphtheriae We show that sortase-catalyzed introduction of a K190-T494 isopeptide bond between adjacent SpaA pilins causes them to form a rigid interface in which the LPLTG sorting signal is inserted into a large binding groove. Cellular and quantitative kinetic measurements of the crosslinking reaction shed light onto the mechanism of pilus biogenesis. We propose that the pilus-specific sortase in C. diphtheriae uses a latch mechanism to select K190 on SpaA for crosslinking in which the sorting signal is partially transferred from the enzyme to a binding groove in SpaA in order to facilitate catalysis. This process is facilitated by a conserved loop in SpaA, which after crosslinking forms a stabilizing latch that covers the K190-T494 isopeptide bond. General features of the structure and sortase-catalyzed assembly mechanism of the SpaA pilus are likely conserved in Gram-positive bacteria.

Optimal Plastic Analysis and Design of Pile Foundations Under Reliable Conditions

In this research, in order to evaluate the plastic limit load and also plastic design parameters of the long pile foundations subjected to horizontal loads, shakedown method is applied. In carrying out shakedown analysis and design methods, large plastic deformations and residual displacements could develop in the pile foundation which might lead to the failure of the structure. For this reason, complementary strain energy of residual forces proposed as a limit condition to control the plastic deformation of the pile structure. Furthermore, considering the uncertainties (strength, manufacturing, geometry) the limit conditions on the complementary strain energy of residual forces are assumed randomly and the reliability condition was formed by the use of the strict reliability index. The influence of the limit conditions on the plastic limit load and design parameters of the long pile in cohesionless soil subjected to lateral load were investigated and limit curves for shakedown load factors are presented. The numerical results show that the probabilistic given limit conditions on the complementary strain energy of residual forces have significant influence on the load bearing limit and the design parameters of pile foundations. The formulations of the reliability based problems lead to mathematical programming which were carried out by the use of non-linear algorithm.

Performance Assessment of Interaction Soil Pile Structure Using the Fragility Methodology

This study aimed to investigate whether the seismic fragility and performance of interaction soil-pile-structure (ISPS) were affected by different parameters: axial load, a section of the pile, and the longitudinal steel ratio of the pile were implanted in different type of sand (loose, medium, dense). In order to better understand the ISPS phenomena, a series of nonlinear static analysis have been conducted for two different cases, namely: (i) fixed system and (ii) ISPS system, to get the curves of the capacity of every parameter for developing the fragility curve. After a comparison of the numerical results of pushover analysis and fragility curves, the results indicate that these parameters are significantly influenced on lateral capacity, ductility and seismic fragility on the ISPS. The increasing in the axial load exhibit high probabilities of exceeding the damage state. The increase in pile section and longitudinal steel ratio, the effect of probability damage (low and high) are not only related to the propriety geometrically, but also related to the values of ductility and lateral capacity of the system. Doi: 10.28991/cej-2021-03091660 Full Text: PDF

Seismic Optimization of High Cantilever Multianchor Pile Strengthening Soil Slopes against Earthquakes

To explore the optimal seismic performance of multianchor pile, we carried out a series of shaking table tests. Based on the special form of multianchor piles’ reinforcement, we put forward the optimal design scheme of using EPS foam as damping layers and energy-dissipation springs for improving the self-coordinating devices of anchor head. By measuring acceleration and dynamic soil-pressure response under different intensities of vibration, we analyzed the correlation between acceleration caused by seismic wave action and damage characterized by time-domain and spectral characteristics of dynamic soil-pressure. We discuss in detail the relationship between frequency and specific period of dynamic soil-pressure and acceleration. We then used the SPECTR program to calculate the energy spectrum. Under the reciprocating action of seismic waves of different intensities, our slope model showed the continuous effect of spatial coupling deformation leading to regional damage and failure. Furthermore, the spatial distribution for amplitude of acceleration and dynamic soil-pressure showed the outstanding response of lateral amplitude of pile structures without optimization. The energy-spectrum distribution of acceleration seismic input was orderly, while the dynamic soil-pressure distribution of piles was disordered. Low-frequency (≤10 Hz) seismic waves have a great influence on these structures. The difference of acceleration hysteresis along the elevations was mainly caused by the propagation stage after the main earthquake. The correlation between dynamic soil-pressure and acceleration response in each group before the pile occurred in the same earthquake area was very weak, showing a low correlation. The optimization effect of optimized structures is related to the position of the shock-absorbing layer. Under high acceleration, multianchor piles easily cause bulge failures or shear failures at the positions of sliding surfaces. These results are helpful for improvements to reliably optimize designs in pile structure dynamic parameters.

A simplified calculation method of ice–structure–water dynamic interaction under earthquake action

Our study aims to find a simplified calculation method of ice–structure–water​ dynamic interaction under seismic load to be used in seismic design of offshore structure. In our proposed method, the ice, modelled in the form of a spring with certain stiffness and damping, constrains the structure at the point of consolidation, and sea ice vibrates with the structure in the form of additional mass under the earthquake action; the influence of hydrodynamic pressure on the structure is based on improved Morison’s hydrodynamic pressure theory. Then, to determine the error of our proposed method, we carried out a shaking table experiment for seismic simulating, and designed an equivalent material for sea ice based on similarity law, and we found that the calculations of our proposed method agree well with the respective experimental data. Finally, we investigated the influence of sea ice on seismic design parameters of an elevated pile structure, and the results show that the internal force increases rapidly at the action position of sea ice, and the displacement and acceleration of the structure top are more sensitive to the high-frequency components of the seismic wave; the sea ice not only decreases the energy dissipation capacity, but also changes the action mode of hydrodynamic pressure on the structure.

Analytical model for time history analysis of single pier bridges considering soil–pile structure interaction effects

This study presents simplified analytical model to analyze the seismic response of typical bridge considering soil–pile structure interaction (SPSI). For this purpose, a typical bridge was selected as a case study. A 6 DOF model was developed by considering the effects of SPSI. In order to evaluate the performance of the analytical model, modal analysis of MRO bridge was first performed. According to the results, the natural period of the MRO bridge was 0.40 s. The natural period calculated in this study differs by 1.7% to 16% from other studies. Three earthquake records were then used to examine the performance of the proposed analytical model for predicting the seismic behavior of the bridge. The analytical model can predict the response of the maximum acceleration of deck up to 16% difference from that of the instrumented structure. Considering the effects of SPSI, the calculated acceleration response for bridge deck is on average 5% to 40% closer to the instrumentation data than the fixed base condition. The proposed analytical model could predict the acceleration response spectra for all three earthquakes with a relatively good approximation. Considering the effects of soil–pile structure interaction, the calculated natural period of bridge system is 10% to 40% closer to the instrumentation data than the fixed base condition.

Formation Mechanism of Preferential Flow Paths and Seepage Characteristics of a Novel Growable Pile for Heap Leaching of Rare Earth

In the traditional heap leaching of rare earth minerals, the top of the rare earth pile is covered with leaching liquid. This creates trouble for vegetation restoration carried out timely on the top of the pile. In order to solve this trouble, a novel pile structure into which leaching liquid is laterally injected is proposed for heap leaching of rare earth. In this study, a laboratory test is carried out to study the formation and distribution of preferential flow paths for the rare earth pile under a horizontal liquid injection condition. Furthermore, numerical simulations based on a dual‐permeability model are conducted to investigate the influence of the preferential flow paths on the seepage characteristics in the rare earth pile. The results show that, under the horizontal liquid injection condition, the fine particles of the rare earth move away from the liquid injection end and also toward the lower part of the pile. The migration of the fine particles results in the formation and connection of macropore, thereby generating preferential flow paths in the rare earth pile. The preferential flow paths are mainly distributed in the lower part of the pile near the liquid injection end. This causes the fluid in the lower part of the pile to seep faster significantly than that in the upper part. Within the region where the preferential flow paths develop, the seepage in the early stage of the horizontal liquid injection is dominated by preferential flow. The preferential flow is more significant at the locations farther away from the liquid injection end.

The influence of the stratum structure of the pipe pile sliding pile of the offshore platform

This article has carried on the theoretical analysis to the generation mechanism of the sliding pile phenomenon. A certain prediction was made on the causes of slipping piles and their influencing factors. At the same time, it is based on the collected field measurement data, an engineering example is selected to briefly analyze the changes in the bearing capacity of the pile foundation after the sliding pile occurs. It is found that the influence of the sliding pile on the bearing capacity of the pile foundation is mainly the influence on the side friction resistance of the pile, and the reduction of the soil resistance is also mainly due to the reduction of the side friction resistance of the pile. Finally, using ABAQUS finite element analysis software, a numerical simulation analysis was carried out on the changes of the stratum structure, the analysis results show that the position change of the soft soil layer has a certain influence on the bearing capacity of the pile, but it does not change the settlement of the pile top under the limit state; The greater the strength of the supporting layer, the greater the bearing capacity and the greater the displacement when reaching the limit state; The length of the slipped pile does not affect the bearing capacity of the pile foundation, and the farther the slipping occurs from the bearing layer, the smaller the impact on the bearing capacity of the pile foundation. Therefore, in the actual project, attention should be paid to the selection of the bearing layer and the soft soil layer close to the bearing layer should be removed to reduce the impact of the slipping pile on the bearing capacity of the pile foundation and ensure that the bearing capacity of the pile foundation meets the design requirements.

Optimization of SOFC stack gas distribution structure based on BP Neural network and CFD

The flow field distribution of solid oxide fuel cells significantly affects the performance of the stack. The flow uniformity can be improved and the power generation efficiency can be improved by optimizing the gas distribution structure of the stack. Based on the simplified 6kW stack model, the stack gas distribution structure with two-stage buffer cavity was designed, and the stack model was numerically simulated by ANSYS Fluent software. The BP neural network model, which can predict the uniformity of the outlet of the integrated stack, is established successfully. The parameters of the gas distribution structure are analyzed and optimized by using the orthogonal test and BP neural network. The results show that at the same time considering pile distribution structure under the condition of surface area and uniformity, when the first stage inlet buffer chamber depth is 40 mm, the channel width is 40 mm, the secondary inlet buffer chamber depth is 80 mm, can effectively reduce the electric pile distribution structure, surface area, to reduce heat loss, at the same time guarantee the integrated electric reactor outlet flow uniformity of more than 96%, greatly improves the efficiency of power generation.