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Go to Editorial ManagerThe finite element method is one of the important methods in analyzing geotechnical engineering problems; its main advantage is the ability to apply for the materials exhibiting non-linear stress-strain behavior. In this study the finite element program PLAXIS 3D 2013 is used to study the behavior of the piles under the influence of seismic waves in saturated sandy soil and the effect of adding geogrid with the pile foundation. The program has been used to facilitate the representation of the real model, input the required soil parameters and implementation of seismic data. Seismic wave, the soil geometry and the pile dimensions were fixed in all models, while dimension and depth of the geogrid used were varied to study the influence of different depth and dimension in reducing the pile displacements and the pore water pressure of soil. The results show that The reduction in settlement ratio (the difference between settlement of pile without and with using geogrid to the settlement without using geogrid) for ( ×L/2), (L×L) and (2L×2L) are 10.6%, 17% and 21.3% respectively. And the settlement ratio for geogrid at depths 8.33% and 12.5% of pile length are 9.6% and 17% respectively.
Shallow foundation suffers from considerable settlement, displacement and tilting under earthquakes. This is particularly due to the shaking associated with earthquakes that lead to the generation of horizontal seismic load transferred through the soil to the foundation. Also, liquefaction could take place during the earthquake in the saturated loose sand. To alleviate the detrimental effect of earthquakes, ground improvement is required. This study examines the response of the shallow square foundation rested on loose sand soil reinforced with geogrid reinforcement when subjected to 2023 Turkey earthquake by using a shaking table system. Different number of geogrid layers are installed; (one, two, three and four), also various geogrid configurations were examined which are (straight, trapezoidal and reverse trapezoidal). The acceleration response, settlement, horizontal displacement, rotation and pore water pressure developed in the sand soil and the shallow foundation during 2023 Turkey earthquake has been examined. The settlement and the horizontal displacement, foundation rotation, acceleration and pore water pressure were measured using rope displacement transducers, tilt sensors, accelerometers and pore water transducers respectively. The results showed that the acceleration amplifies when passing through loose sand. The results also indicated that the shallow foundation experienced noticeable settlement, horizontal displacement and rotation when subjected to the seismic loads. On the other hand, the installation of geogrid proved to be effective in controlling the problems associated with earthquakes. The optimum geogrid reinforcement is occurred when three layers of geogrid placed in reverse trapezoidal configuration (3RT) since it gave the best reduction in the acceleration amplification and the highest decrease in the foundation settlement, displacement and tilting which is about (60-66) %. Nevertheless, the effectiveness of geogrid minimizes when the sand soil becomes saturated. In addition, liquefaction occurs during earthquakes especially at the shallower depths because of the decrease in the shear strength of saturated soil.
This study explores the impact of adding high-density polyethylene (HDPE) and Novolac polymers to gypseous soil from Tikrit City, Iraq, to enhance its geotechnical properties. The soil contained 38% gypsum, and the polymers were added in varying proportions (1%, 3%, 6%). Both polymers improved maximum dry density, optimum moisture content, and reduced collapse potential (Ic). The collapse potential was reduced by 64%, 77.7%, and 83.2% at 1%, 3%, and 6% HDPE content, respectively. The collapse potential was reduced by 82.3%, 74.8%, and 51.9% at 1%, 3%, and 6% Novolac polymer content, respectively. In the dry conditions, the internal friction angle increased by about 22.9% and 5.7% as the HDPE content was increased by 3% and 6% respectively. Adding Novolac polymer also increased the internal friction angle by about 5.7% by the addition of 3% Novolac polymer. In soaked conditions, the best increase in internal friction angle (?) was 30% with the addition of 3% HDPE polymer. the internal friction angle increased by about 26.7% by adding 1% and 3% of Novolac polymer. The study concludes that adding HDPE and Novolac polymers can improve geotechnical properties, but their effect on CBR is complex and depends on the polymer percentage added and soil moisture state.
Expansive soil poses significant challenges for civil engineers worldwide since it seriously affects the structures built upon it. This soil has a very active group of minerals called montmorillonite, which is responsible for the significant volume change it exhibits. For a number of years, chemical additives have been utilized to stabilize soil, with various levels of success. Soil stabilization has involved the use of a variety of additives, including cement, lime, polymers, salts, and combinations of these. However, lime is very often used for expansive soil stabilization as it improves the soil's mechanical properties. The effects of adding three percentages of lime (3%, 6%, and 9%) to expansive soil to improve its engineering properties are investigated through several tests. The laboratory tests consist of standard compaction, sieve analysis, atterberg limits, hydrometer, California bearing ratio, consolidation test, swelling potential, and specific gravity. The test results displayed that the plasticity index, liquid limit, swelling potential, and maximum dry density, specific gravity decreased using (3%, 6%, and 9%) lime. In contrast, the plastic limit, and optimum moisture content increased using (3%, 6%, and 9%) lime. The California bearing ratio is increased from (12.13% to 14.65%) by adding (9% L). The swelling index and compression index are decreased from (0.070 to 0.030) and from (0.581 to 0.193) respectively by adding (9% L). The swelling percentage is reduced from (18.77% to 6.03%) by adding (9% L).