In a previous study, a series of 9 model tests performed on embankment models resting on soft clay treated with and without ordinary stone columns (OSC), encased stone columns (ESC), and with horizontal layer of geogrid at interface and at 0·1 h height has been carried out to investigate the behaviour of piled (stone columned) and geogrid reinforced embankments. In this paper, these tests are simulated numerically by the finite element method using the program Geostudio (SIGMA/W). Firstly, reanalysis was done of experimental work of embankment models constructed on soft clay treated with OSC and ESC. Secondly, embankment models reinforced by a horizontal layer resting on soft clay strengthened with OSC and ESC were analyzed. A horizontal layer of geogrid is embedded at different levels of embankment height. It was concluded that in the embankment models constructed on soft clay treated with stone columns at a spacing s = 2·5 d with length to diameter ratio L/d ratio = 8, the maximum bearing improvement ratio (qt/qunt) equals 1·33 for the ordinary stone columns and 1·59 for the encased stone columns and about 1·13 and 1·23 when one layer of geogrid is embedded at interface or at 0·1 h height, respectively.
In this study focuses on improving an expansive soils geotechnical properties treated by tire crumble and decreasing the natural contamination by this waste material. The waste rubber of tire in the form of crumble with size ranging between 0.08 to 2 mm with proportion from 0 to 10% was used in this examination. Routine tests such as compaction, unconfined compressive strength, consolidation and swelling pressure test have been done on untreated and treated soils with crumble tire rubber. According to the test results it was found that, the maximum dry density of treated samples decrease with increased tire crumble content, while a slight reduction in the optimum moisture content was found simultaneously. Also, the results of unconfined compression tests showed that, the crumble tire rubber could not improve the properties despite the fact that that the soil still in the hardened consistency. In like manner results demonstrate that using crumble rubber might be successful procedure in upgrading the soil characteristics against swelling potential of soils by approximately 29.8, 43.4, 49.39, 14.77 times than untreated soil for (1, 3, 5, 10%) tire crumble rubber content. In addition the results show increasing crumble tire rubber content from 1 to 5% gave low displacement values by about (26.01 - 43.9)% than its value in untreated samples. Finally, it has additionally seen that using of crumble tire rubber aides in decreasing the compression index, consolidation coefficient, permeability coefficient and volume change coefficient.
The use of stabilizing technologies has significantly expanded in recent years specially when sites are frequently construction in poor land locations. This study suggests using nano-silica to improve clayey soil's functionality. A range of nano-silica concentrations (0, 0.1, 0.2, 0.4, and 0.8) were used. Laboratory testing was used to identify Atterber's limitations, the optimum moisture content (OMC), the maximum dry density (MDD), and microstructural examination. According to the study, treating soil with 0.4-0.6% nano-silica yields the best results. According to the result, the liquid limit (LL) and plastic limit (PL) are reached maximum at 0.6% nano-silica, while the plasticity index is at its lowest point. The results showed that incorporating nano-silica into clay samples will lower the maximum.
Gypsum and anhydrite rocks are frequently found in numerous countries of the world in extensive deposits, the huge region in middle and west of Iraq is classified as a gypseous soil. Stone columns are non-time dependent foundation technique used to increase the structural stability and to reduce the structural deformations of soil. In the present study, the finite element method is used as a tool to utilized the effect of using stone columns with geogrid as reinforcing material for treatment gypsiferous subgrade soil under embankment during both construction and consolidation conditions. The results show that decreasing the stone column spacing leads to a considerable decrease in the settlement beneath the embankment, especially below the center line, reduction in the settlement of about 60% and when using geosynthetic material the reduction about 75%. Also, increases the excess pore water pressure immediately after the construction of each lift of the embankment and then falls with and without using geosynthetic material. The vertical stress in the gypsiferous subgrade soil increases at a very small rate especially in the early stages and decreases as stone columns spacing decreases.
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