• Geomechanics and Engineering
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• v.4 no.2
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• pp.79-90
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• 2012

Air pluviation method is widely adopted for preparation of large, uniform and repeatable sand beds of desired densities for laboratory studies to simulate in-situ conditions and obtain test results which are highly reliable. This paper presents details of a portable traveling pluviator recently developed for model sand bed preparation. The pluviator essentially consisted of a hopper, orifice plates for varying deposition intensity, combination of flexible and rigid tubes for smooth travel of material, and a set of diffuser sieves to obtain uniformity of pluviated sand bed. It was observed that sand beds of lower relative density can be achieved by controlling height of fall, whereas, denser sand beds could be obtained by controlling deposition intensity. Uniformity of pluviated sand beds was evaluated using cone penetration test and at lower relative densities minor variation in density was observed with depth. With increase in relative density of sand bed higher repeatability of uniform pluviation was achieved.

• Geomechanics and Engineering
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• v.28 no.5
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• pp.521-529
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• 2022

This research work deals with the development of air pluviation method for preparing uniform sand specimens for conducting large scale laboratory testing. Simulating real field conditions and to get reliable results, air pluviation method is highly desirable. This paper presents a special technique called air pluviation or sand raining technique for achieving uniform relative density. The apparatus is accompanied by a hopper, shutters with different orifice sizes and numbers and set of sieves. Before using this apparatus, calibration curves are drawn for relative density against different height of fall (H) and shutter sizes. From these calibration curves, corresponding to the desired relative density of 60%, the shutter size of 13mm and height of fall of 457.2 mm, are selected and maintained throughout the pluviation process. The density obtained from the mobile pluviator is then verified using the Dynamic Cone Penetrometer (DCP) test where the soil is poured in the box using defined shutter size and fall height. The results obtained from the DCP test are averaged as 60±0.5 which was desirable. The mobile pluviator used in this research is also capable of obtaining relative densities up to 90%. The instrument is validated using experimental and numerical approach. In numerical study, Plaxis 3D software is used in which the soil mass is defined by 10-Node tetrahedral elements and 6-Node plate is used to simulate plate behavior in the validation phase. The results obtained from numerical approach were compared with that of experimental one which showed very close correlation.

• Geomechanics and Engineering
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• v.14 no.2
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• pp.131-139
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• 2018

The preparation of repeatable and uniformly reconstituted soil specimens up to the specified conditions is an essential requirement for the laboratory tests. In this study for large samples replication, the simultaneous usage of the traveling pluviation and curtain raining technique is used to develop a new method, called the curtain travelling pluviator (CTP). This simple and cost effective system is based on the air pluviation approach, whilst reducing the sample production time, can reproduce uniform samples with relative densities ranging from 25% to 96%. In order to investigate the resulting suitability and uniformity from the proposed method, a series of tests is performed. The effect of curtain traveling velocity, curtain width, drop height, and flow rate on the parameters of the sample is thoroughly investigated. Increase in the curtain velocity and drop height leads to the increase in relative density for the sand specimen. Increase in curtain width typically resulted in the reduction of relative density. Test results reveal that the terminal drop height for the sand specimen in this study is more than 500 mm. Relative density contour lines are presented that can be utilized in optimizing the drop height and curtain width parameters. Sample uniformity in the vertical and horizontal orientation is investigated through the sampling containers. Increasing relative density tends to result in the higher sample repeatability and uniformity.

• Journal of the Korean Geosynthetics Society
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• v.16 no.4
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• pp.1-11
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• 2017

In this study, 1/6 small-scale model tests of helical piles were conducted to evaluate their installation time and ultimate capacities. Model sand layers were constructed using sand pluviating method to produce uniform soil relative density. For installation of different helical piles varying locations (vertical center-to-center spacings of 50 mm and 150 mm) of helix plates, two different rotation speeds of 15 rpm and 30 rpm were implemented. Cone penetration equipment was installed within the hallow section of the helical pile to increase ultimate capacity of helical pile and to evaluate soil properties of plugged soils and soils below pile tip after installation of the piles. Based on the test results, the most fasted installation was possible under the condition of "rotation speed of 30 rpm and center-to-center spacing of 50 mm", and the highest ultimate capacity was mobilized under the condition of "rotation speed of 30 rpm and center-to-center spacing of 150 mm with cone penetration implementation."

• Journal of the Korean Geosynthetics Society
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• v.16 no.2
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• pp.67-77
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• 2017

This study analyzes behavior of bearing capacity of open-ended pipe pile from laboratory experiment results. Unlike the conventional pipe piles, cone penetration is implemented into the inside of the pipe pile. During the cone penetration, cone driving energy helps densification of plugged soils and soils below the pile end. Sand pluviator was used to obtain homogeneous soil layers. Two kinds of piles with different pile outer surface roughness were prepared, and two different drop heights of pile driving were applied. Eight experimental cases varying pile outer surface roughness, pile driving energy for conventional and cone penetration implemented piles were conducted. From the experiments, ultimate load of the pile increased approximately by 70% for increased pile driving height, and it increased by 21% for rougher surface pile. When cone penetration is implemented, the ultimate load increased by 40% in average.