Short Piles Research Articles

Experimental Investigation of Stress Distribution of Vertically Loaded Short Displacement Pile in Cohesion-less Soil

One can find lot of the methods and theories to determine and interpret the nature of the bearing capacity of displacement piles in cohesion-less soil. The presence of many methods leads to the variety of results and yields that no general and relevant methods have been proposed yet. Many experimental investigations do not fit properly the results of known numerical simulations. These simulations yield that the shear stress near the end of the pile increases significantly, when compared with the rest of pile length. Current investigation presents the specific test results of the short displacement pile under vertical load in cohesion-less soil. The full scale test was performed and the vertical stresses beneath base and shear stresses along the pile have been measured, as a result the shear stress significant increase near the end of the pile was observed. The obtained results can be used for developing the shaft and tip bearing capacity evaluation method for the short displacement piles in cohesion-less soil.

The Dynamic Characteristic Experimental Method on the Composite Foundation with Rigid-Flexible Compound Piles

Based on the idea of optimization design of pile type, the composite foundations, which include cememt-flyash-gaavel (for short CFG) long piles and cement-soil (for short CS) short piles, and CS piles with CFG core as well, are formed. The method of the site dynamic characteristic tests of the composite foundations is discussed. The test results show that fireworks bomb may replace demolitions as the vibration resource. Vibration time is about 0.1 sec. Horizontal vibration major frequency is at 22.476 - 56.436 Hz, and vertical vibration major frequency is at 15.538 - 55.884 Hz. The pile arrangements of the composite foundation in the same site have more effect on the acceleration peak value. From the point of vibration, the anti-seismic effect of the CS piles with CFG core is better than others.

Research on the Pile Side Friction of Composite Foundation with Long-Short-Piles under High-Rise Building

It is used as an example that the composite foundation with long-short-piles is used in liquefied soil under a high-rise building .By using the finite element method, the effects of short pile replacement ratio, long pile replacement ratio, raft thickness on side friction of the pile are discussed respectively. The results show that: Short pile replacement ratio changes have an effect on side friction of the long pile from 4m to 15m. With long pile replacement ratio increasing, negative friction and positive friction of the long pile decreases gradually. With the raft thickness increasing, negative friction and positive friction of the long pile decreases gradually. Otherwise, the distance of side friction of the long pile comes up to zero increase gradually. These conclusions are provided as references for future optimum design.

Depth of Fixity of Piles in Clay Under Dynamic Lateral Load

Dynamic experiments were carried out on instrumented model aluminium single piles embedded in clay of different consistencies to study its bending behaviour under lateral loads. Piles with different length to diameter ratios were used. Dynamic lateral load of different magnitudes ranging from 7 to 30 N at wide range of frequencies from 2 to 50 Hz were applied. The load transferred to the pile, pile head displacement and the strain variation along the pile length were measured using a dedicated data acquisition system. Static lateral load tests were also performed to investigate the magnification of dynamic response of piles in clay. It is found that the maximum bending moment due to dynamic load is magnified by about 1.5–4 times in comparison to the static load for short piles but about 9 times for long piles. Depth of fixity and effective pile length is also largely amplified under dynamic loads, thus indicating that a pile which behaves as a flexible pile under static load, may not exhibit flexible behaviour under dynamic load.

Lateral capacity of piles in layered soil: a simple approach

Appropriate assessment of lateral capacity of pile foundation is known to be a complex problem involving soil-structure interaction. Having reviewed the available methods in brief, relative paucity of simple and rational technique to evaluate lateral capacity of pile in layered soil is identified. In this context, two efficient approaches for the assessment of lateral capacity of short pile embedded in bi-layer cohesive deposit is developed. It is presumed that the allowable lateral capacity of short pile is generally dictated by the permissible lateral displacement within which pile-soil system may be assumed to be elastic. The applicability of the scheme, depicted through illustration, is believed to be of ample help at least for practical purpose.

Model Test Studies of the Vertical Bearing Behavior of Bored Piles with Breakage Defects

In order to study the vertical bearing behavior of bored piles with breakage defects, a series of methods for simulation of normal piles and broken piles in laboratory was developed and used to investigate the vertical bearing behavior of these piles. The load-settlement curves of normal piles and broken piles were measured and analyzed. The tests revealed that the upper part of a broken pile works alone as a short pile before it contact with the lower part of the pile at the end of the first sudden drop stage.The analysis of the test results showed that the position of the breakage defect has a great influence on the lost in vertical bearing capacity of the pile.

Application of Long-Short-Pile Composite Foundation of High-Rise Building in Soft Soil

A case of the long-short-pile composite foundation in liquefied soft soil under a 30-storey high-rise building is presented, in which the long and short piles are made of cement-flyash-gravel (CFG) and lime. A new design calculation method of bearing capacity and settlement of composite foundation is introduced, and the calculated value is compared with the actual measurement. The results show that the liquefaction of soft ground is eliminated and the demand of load and settlement for upper building is met. At the same time, it is proved that the design method is feasible.

A Study on Bearing Characteristics of Horizontally-Loaded Short Piles in 750kV Transmission Line on Loess Foundation

For the angle tower foundation of 750kV transmission line, the overturning effect caused by wire tension is a control factor of tower foundation design. The pile foundation on loess was taken as a research object in this study, where two typical regions along 750kV Lanzhou - Tianshui - Baoji transmission line were selected to carry out the site full-size horizontal static load test. Through the arrangement of displacement sensors and earth pressure cells around piles, the load-displacement curve of pile lateral soil under horizontal loads was obtained as well as the distribution law of soil stress at different locations of the pile. Based on the "m" method, the soil stress at different locations of the pile was calculated. The results showed that the calculated results were well consistent with experimental results. This research work can provide a theoretical basis and design guidance for tower foundation selection and design optimization of 750kV transmission line.

Settlement Analysis of Single Large-Diameter and Super-Long Bored Piles in Cohesive Soils

The behavior of single axially loaded large-diameter and super-long bored piles have large difference to single small diameter short piles. The article analyzes the load transfer characteristic of single axially loaded large-diameter and super-long bored piles in deep soft clay in the Yangtze River Delta region. And the hybrid method of finite element analysis of rod structure coupling with the shear displacement method for single pile was utilized to simulating and predicting the single pile performance. It is verified that the settlement calculation hybrid method in this paper is reliable.

Vertical Load Mechanism Analysis and Experimental Research on Super-Long PHC Pipe Pile in Soft Clay

Pile foundation design has gradually used the super-long pile structure form with the port and offshore engineering construction developing towards to the direction of large-scale, deepwater, and coast geological becomes more complex, bearing stratum becomes more deeper. PHC pile is the first choice of pile foundation design form, just because it has many advantages. The former researches of pile vertical load mainly on limit bearing capacity, the calculation is reasonable for short pile and middle long pile, however, it is not reasonable for super-long pile, pile body side and tip resistance can not reach the limit when structure is to limit. This paper puts forward the calculation model of super-long PHC pile vertical load in soft clay based on vertical load mechanism analysis and experimental research on the foundation pile, and the calculated and test value coincide preferably.

Centrifuge modelling of spudcan–pile interaction in soft clay

The installation and extraction of jack-up spudcans may induce significant stresses in the adjacent piles supporting the permanent jacket platforms at an offshore site. In the present study, centrifuge model tests were conducted to investigate the effects of spudcan movements on the lateral and axial behaviour of adjacent fixed-head piles embedded in soft clay. Parameters such as jack-up operation period, clearance between the spudcan and pile, and the embedment length of the pile are examined. The test results show that the most critical period for platform piles is at the end of spudcan installation, and the lateral pile behaviour is more severely affected than the axial pile behaviour. During spudcan installation, the induced bending moment on a pile located one-quarter spudcan diameter away from the spudcan edge is about 2·4 times that of a pile located one spudcan diameter away. For a deeply buried spudcan with penetration of over three-quarters spudcan diameter, the induced bending moment on longer piles is much smaller than that on shorter piles. The experimental findings provide further insights into the underlying mechanisms governing spudcan–pile interaction in soft clay under various configurations and conditions.

The Iridescent Blue-Black Boy with Wings (After Márquez)

The Iridescent Blue-Black Boy with Wings (After Márquez)

Control of calcium carbonate crystallization by using anionic polymethylsiloxanes as templates

Sulfonated (SO3H-PMS) and carboxylated (CO2H-PMS) polymethylsiloxanes were synthesized and their effects as anionic template modifier on the CaCO3 crystal morphologies were evaluated. In vitro crystallization assays of CaCO3 were performed at room temperature by using gas diffusion method at different concentration, pH and time. SEM images of CaCO3 showed well-defined short calcite piles (ca. 5μm) and elongated calcite (ca. 20μm) when SO3H-PMS was used. When CO2H-PMS was used, the morphology of CaCO3 crystals was single-truncated at pH 7–9 and aggregated-modified calcite at pH 10–11. However, at pH 12 the least stable donut-shaped vaterite crystals were formed. EDS and XRD confirmed the presence of Si from anionic PMS templates on the CaCO3 surfaces and its polymorphism, respectively. Results showed that the selective morphologies of CaCO3 reflect the electrostatic interaction of anionic groups of functionalized PMS with Ca2+ adsorbed on CaCO3 crystals. Rounded and truncated-modified fluorescent CaCO3 was also produced by the inclusion of functionalized PMS into the lattice of CaCO3 matrix. We demonstrated that the anionic PMS offer a good modifier for polymer-controlled crystallization and a convenient approach for understanding the biomineralization field.

Performance of Port Facilities in Southern Chile during the 27 February 2010 Maule Earthquake

This article describes the seismic performance of a group of ports in southern Chile during the 27 February 2010 Maule, Chile, earthquake. Direct costs in damage for these ports have been estimated in slightly less than US$300 million. Similarly to the performance of other ports in previous earthquakes, the most common failures observed were soil related, and include soil liquefaction, lateral spreading, and pile failures. Structural failures were mostly due to short pile effects and natural torsion. This situation is contrasted herein with the performance of the South Coronel Pier, which was seismically isolated in 2007. The isolated portion of this port remained operational after the earthquake, which was the main design goal. Post-earthquake preliminary analyses indicate that the structure was subjected to deformations and forces of approximately 60% to 70% of their design values, respectively. Piles and superstructure remained within elastic range, while the isolators experienced important nonlinear deformations.

A New Type of Pile – Long with Cushion-Short without Cushion Rigid Pile

At present, in the deep soft soil area, pile types of composite foundation include rigid-flexible and long-short piles, rigid long- short pile , pile partner, and this paper proposes a new type of pile - rigid long-short piles with no cushion short pile. Using the one Finite element software Midas- GTS , this paper compared these pile types ,in vertical direction element stress, pile-soil stress ratio and cushion stress level the cushion of pile-soil stress ratio and stress level, to illustrate the advantages of the new pile.

Simple technologies for on-farm composting of cattle slurry solid fraction

Composting technologies and control systems have reached an advanced stage of development, but these are too complex and expensive for most agricultural practitioners for treating livestock slurries. The development of simple, but robust and cost-effective techniques for composting animal slurries is therefore required to realise the potential benefits of waste sanitation and soil improvement associated with composted livestock manures. Cattle slurry solid fraction (SF) was collected at the rates of 4m3h−1 and 1m3h−1 and composted in tall (1.7m) and short (1.2m) static piles, to evaluate the physicochemical characteristics and nutrient dynamics of SF during composting without addition of bulking agent materials, and without turning or water addition. Highest maximum temperatures (62–64°C) were measured in tall piles compared to short piles (52°C). However, maximum rates of organic matter (OM) destruction were observed at mesophilic temperature ranges in short piles, compared to tall piles, whereas thermophilic temperatures in tall piles maximised sanitation and enhanced moisture reduction. Final OM losses were within the range of 520–660gkg−1 dry solids and the net loss of OM significantly (P<0.001) increased nutrient concentrations during the composting period. An advanced degree of stabilization of the SF was indicated by low final pile temperatures and C/N ratio, low concentrations of NH4+ and increased concentrations of NO3- in SF composts. The results indicated that minimum intervention composting of SF in static piles over 168days can produce agronomically effective organic soil amendments containing significant amounts of OM (772–856gkg−1) and plant nutrients. The implications of a minimal intervention management approach to composting SF on compost pathogen reduction are discussed and possible measures to improve sanitation are suggested.

Ground movements in EPB shield tunneling of Bangkok subway project and impacts on adjacent buildings

Monitoring data of the first Bangkok subway project excavated by 8 EPB shields were analyzed to evaluate the ground movement characteristics and responses of adjacent buildings. Mostly the maximum ground surface settlements were in the range of 20–40mm, corresponding to 0.5–2.0% of tunnel volume loss, although few sections experienced larger settlements reaching 100mm. Larger ground losses tended to occur while excavating in sand or mixed soil layers and at locations of long duration stoppage. There was only a slight trend of relationship between the settlement and shield pressure. The predominant factor controlling the movement was the human related factor in shield operating which was not easy to predict. Obstructions from piled foundations and other known and unknown buried utilities and objects, resulted in non-conformance of ground surface settlement troughs to the Gaussian function, thus they could not be predicted by any empirical and analytical methods. Shield face pressures often caused outward ground displacements that complicated the final ground movements, particularly the lateral displacement which could not be predicted by available analytical methods. Long term consolidation settlements mainly occurred in the soft clay layer, but the amount and rate did not seem significant. On impacts to buildings, buildings on deep piles showed the least induced settlements. But for buildings on short piles, the settlements may be larger or smaller than ground surface settlements, depending on the distance from tunnel center line and pile tip depth.

Numerical modelling of short pile behaviour subjected to lateral load

The behaviour of laterally loaded short rigid piles founded in sandy soil has been investigated numerically by performing a series of three-dimensional non-linear finite element analyses. The parameters investigated are relative density and elasticity modulus of sandy soil, load eccentricity, pile geometry and geometric configurations such as pile cross-section, embedment ratio and pile diameter. The results of the existing design methods used for predicting the lateral load capacity of short rigid piles were compared with the results of the three-dimensional non-linear finite element analyses. The results proved that the parameters investigated had considerable effect on the behaviour of rigid piles subjected to lateral loads. It was also shown that the value of the ultimate lateral load capacity could be significantly different depending on the conventional methods used.

Numerical Analysis of Long-Short-Pile Composite Foundation with Cushion or No Cushion

With the Drucker-Prager yield criterion, the ANSYS software is used to analyze the long-short-pile composite foundation by using three-dimensional nonlinear finite element method. The influences of load on axial stress and maximal axial stress of head of pile with cushion or not have been investigated by simulating composite foundation through nine long piles and sixteen short piles. The result indicates the cushion can reduce the stress concentration in head of pile effectively with increase of load. This conclusion has a certain value for engineering.

Shear Keyを付けた異形短杭の引抜き抵抗力に関する実験的考察 施設園芸ハウスの耐風性に関する研究 (IV)

Shear Keyを付けた異形短杭の引抜き抵抗力に関する実験的考察 施設園芸ハウスの耐風性に関する研究 (IV)