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Go to Editorial ManagerDue to significant increasing in seismic activity in world during the last decades especially in Middle East region; engineers have been giving increasing attention to the design of buildings for earthquake resistance. In this study 3-D seismic behavior of piles is investigated using the finite element program PLAXIS 3D 2013. _x000D_ Piles are one of the most commonly used foundations in seismic areas where the soil is inadequate to carry the load on its own. In these seismic areas, piles often pass through (penetrate) shallow loose and/or soft soil deposits and rests on competent end bearing soils. Thus a model of soil - pile system is simulated in the finite element program._x000D_ The dynamic parameters of soil are used as input dynamic data of PLAXIS 3D program, in addition to the static properties of soil collected from soil investigation works._x000D_ The research showed the susceptibility of PLAXIS 3D program in analyzing piles with different soil conditions under earthquake action. The results also showed the importance of studying seismic behavior of soil-pile system using 3-D analysis rather than 2-D analysis because the problem is truly 3-D and should be analyzed as such.
The 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).
An overview of electro-osmosis (EO) and electrokinetic (EK) soil treatment methods is provided in this paper, along with their impact on pile capacity, installation, and foundation shear strength after improving the geotechnical properties of weak soils, particularly soft clays. As a result of their low shear strength, high compressibility, and poor drainage characteristics, soft clayey soils pose significant challenges in civil engineering. With EO and EK, pore water and ions are moved through the soil matrix under an applied electric field, resulting in consolidation, increased shear strength, and reduced plasticity. This review explores the fundamental principles of EO and EK, including the mechanisms of water transport, ion migration, and electrochemical reactions. It examines various electrode configurations, treatment parameters, and their influence on soil improvement. Furthermore, the paper analyzes the effects of EO treatment on pile capacity, considering both the increase in soil strength and the reduction in pore water pressure during installation. The impact on pile installation methods, such as reducing driving resistance and improving grout penetration, is also discussed. Finally, the review investigates the enhancement of foundation shear strength through improved soil properties achieved by EO/EK treatment. By synthesizing existing research, this paper aims to provide a comprehensive understanding of the potential benefits and limitations of EO and EK methods for ground improvement in soft clayey soils, offering valuable insights for future research and practical applications in geotechnical engineering.
Driven piles have often been used in many civil structures to provide structural loading support. However, the unavoidable vibrations induced by pile driving processes may cause varying degrees of damage to adjacent structures. This research presents experimental studies to investigate the transmitted vibrations induced by impact of pile driving on vicinity piles. In the experimental work, a small scale model was tested in a sand box (steel container 1 × 1.5 × 0.8 m) with pile driving hammer device to install the impact pile in sand soil by dropping weights (1, 2, 3, 4 and 5 kg) for different heights of falling (4, 8, 12, 16 and 20 cm). The peak particle velocity was measured at a head of the vicinity piles by vibration meter device. In this study, several piles on different distances away from the vibration source were studied. The experimental results indicate that the peak particle velocity for vibrations emitted with impact pile driving is increased with increasing the energy and the penetration depth of pile driving for all vicinity piles and it can be decreased without change in the driving energy by decreasing the weight of hammer and increasing the height of falling hammer. Vibration intensities are attenuated with increasing surface distance from the pile driving and the peak particle velocity decreased uniformly with surface distance from the pile driving for piles. Also, through laboratory model representation and evaluation of the results obtained in the laboratory, the empirical relations which were determined based on the scaled-distance concept, are appropriate and give results very close and can be relied upon to represent the transmission of vibration resulting from the impact of pile driving to nearby piles.