Vicinity Of Pile Research Articles

E-Defense shaking test and pushover analyses for lateral pile behavior in a group considering soil deformation in vicinity of piles

Large-scale E-Defense shaking table tests were performed using a 3 × 3 pile group in dry sand layers to clarify dynamic lateral pile behavior in a group. The mechanism behind the seismic response of piles in a group was investigated based on the earth pressure acting on piles and soil deformation in the vicinity of the pile and that in the free field. The test results indicated that soil deformation in the vicinity of piles is the key factor influencing group effects during an earthquake. To evaluate pile response in a group, a new concept involving static pushover analyses of pile groups considering soil deformation in the vicinity of piles was developed. The estimated pile response showed reasonable agreement with the experimental results obtained without using p-multipliers. The proposed method could evaluate pile responses considering soil and pile properties, loading levels, pile spacing, and kinematic effects. Thus, the proposed method could help better estimate pile response during earthquakes.

The effects of uniform and nonuniform pile spacing variations on local scour at pile groups

ABSTRACTPile groups are frequently used to support bridge decks. Scour in the vicinity of piles is the main cause for the bridges failure. In this research, to address the effects of uniform and nonuniform pile spacing on the equilibrium scour depth, laboratory experiments were carried out under steady clear-water conditions. For this purpose, scour depth produced by pile group with various pile spacing and arrangement was investigated using a laboratory flume. Flume bed was covered by uniform sediments with a median size of 0.9 mm and 0.2 m thickness. Flow discharge and velocity as well as scour depth were recorded in each experiment and the data were analyzed. The results showed that the pile spacing influences the local scour depth and with increase in uniform and transverse (perpendicular to the flow) spacing, the maximum scour depth was reduced. The pile spacing variation in line with the flow has a minor effect on scour depth. In addition, the pile spacing perpendicular to the flow was with the most influences on scour depth. The results of this research can be used by engineers to optimize the design of bridges.

Acid-Generating and Leaching Potential of Soils in a Coal Waste Rock Pile in Northeastern China

ABSTRACTThe present study involved the assessment of potential generation of acid drainage and also metal leaching from an abandoned large (175 m) low sulfur waste rock pile—the dominant mine waste at the site—at the Haizhou coal mine. Laboratory-based static and column leaching tests on waste rock samples were conducted. The static tests were done for 8 composite samples collected from different parts of pile. A column study was performed using mixture of waste rock soil samples to assess metals attenuation process of background soils in vicinity of pile when rainwater reacts with low-sulfide waste rocks. Total concentration of major elements in solid samples was determined using dispersive X-ray fluorescence spectrometry (XRF) and chemical analysis of leachate were measured by inductively coupled plasma optical emission spectrometry (ICP-OES), ion chromatography and titration methods. The inverse geochemical modeling using PHREEQC was applied to explain possible mass transfer processes between column leachates of waste pile and background soils. Static tests (including acid–base accounting (ABA) and net acid generation (NAG)) and mineralogical information suggest that the waste rock is non-acid generating. The large amount of aluminosilicate minerals and probably trace amounts of carbonates with respect to low sulfur content of waste rock pile represents a potentially large source of neutralization potential according to static test results. It was also found that presence of inherent neutralizing materials in waste rock and also in surrounding background soils provide sufficient neutrality and possibly immobilize the trace and heavy metal contents of waste rocks and potentially protects water resources.

回転貫入により施工される羽根付き杭の周辺地盤の土性変化と水平抵抗特性

A rotary press-in pile with wings has advantages to get large vertical bearing capacity for its pile diameter and to reduce the amount of soil excavated for its installation. On the other hand, it has been concerned that the rotary pile might cause weakening of the soil around the rotary pile. Even in the case of clay, it has not been confirmed that such weakening of the surrounding soil would be caused by peripheral soil displacement during pile installation and/or the passage of pile wings. In this paper, a series of experiments was performed to grasp the behavior of a rotary press-in pile horizontally loaded, and the property changes of surrounding soil by installing a rotary press-in pile with wings. In the experiments, the execution of pile installation was managed with constantly maintaining the ratio of s/p in the range of 1.0±0.1, where s is the penetration length of pile rotated by one revolution and p is the helical pitch of its pile wing. The experiments were carried out at two different sites, where one was the site depositing an alluvium clay layer and the other with a diluvial loam layer. In the experiments, in order to investigate the properties of soil around a pile, the measurements of bulk density and water content were conducted for soil samples taken from the vicinity of the pile shaft with specially equipped apparatus. And also, the one dimensional consolidation test, and the tri-axial compression test were performed for samples taken in the vicinity of the pile were performed. The lateral loading tests, apparatus of one of which was directly equipped with pile shaft and the other of which was normal test, were carried out. In order to compare the differences in the pile installation methods, the laterally loading tests for the pile installed by rotation method and the buried pile were carried out. As a result of this study, the conclusions are as follows. 1) In the soil around a rotary press-in pile with wings, density increase and stiffness decrease were caused by soil displacement and wing passage. 2) The range where soil density increases depends on the compressibility of soil. 3) The stiffness decrease of the soil in the vicinity of pile is more strongly affected by soil displacement than by wing passage. 4) The installation method of the rotary pile constantly maintaining s/p can provide appropriate installation without the occurrence of void around the wing although there seemed the gap between the pile shaft and the ground in any case. 5) The coefficient of horizontal subgrade reaction for the rotary pile with wings became 0.54-0.74 times as large as that for the buried pile due to the gap between pile shaft and ground, and the stiffness decrease of the soil in the vicinity of the pile.

Numerical and wind tunnel modeling on the windbreak effectiveness to control the aeolian erosion of conical stockpiles

There are many industrial sites where open aggregate conical piles exist to store granular materials, like coal, industrial residuals, or other minerals. Usually these storage piles are placed in open areas, making them susceptible to wind erosion, which can create health, environmental, and/or economical concerns. It is common to minimize the dust emission through the placement of windbreaks in the vicinity of the storage piles, which reduces the wind speed in the vicinity of the pile’s surface. In this work, some experimental results from a wind tunnel study on the erosion of a conical sand pile, exposed or protected by a fence with porosities of 0, 70, and 83%, are shown. For the sheltered cases, the windbreak was placed at several distances from the pile’s leading edge, ranging from H to 4H, where H is the initial height of the non-eroded pile. The evolution of the shape of the sand pile is shown, at different instances in time, and the pile deformation quantified, using a novel experimental setup developed for wind erosion studies. This information might be regarded as a useful dataset for the benchmark of computational models aiming to produce the transient simulation of the aeolian erosion of stockpiles. The CFD results are comprised of the modeling of several experimental scenarios. The computational results for the surface wind velocity show a good correlation with the initial deformation of the pile. Based on the results, the isocontours of (u s /u r ) presented might be regarded as a good basis for the estimation of the pile shear velocity.