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Purpose – The experiments of this study investigated the effect of the subgrade degree of saturation on the value of the stresses generated on the surface and the middle (vertical and lateral stresses). The objectives of this study can be identified by studying the effect of subgrade layer degree of saturation variation, load amplitude and load frequency on the transmitted stresses through the ballast layer to the subgrade layer and the stress distribution inside it and investigating the excess pore water pressure development in the clay layer in the case of a fully saturated subgrade layer and the change in matric suction in the case of an unsaturated subgrade layer. Design/methodology/approach – Thirty-six laboratory experiments were conducted using approximately half-scale replicas of real railways, with an iron box measuring 1.5 x 1.0 × 1.0 m. Inside the box, a 0.5 m thick layer of clay soil representing the base layer was built. Above it is a 0.2 m thick ballast layer made of crushed stone, and on top of that is a 0.8 m long rail line supported by three 0.9 m (0.1 × 0.1 m) slipper beams. The subgrade layer has been built at the following various saturation levels: 100, 80, 70 and 60%. Experiments were conducted with various frequencies of 1, 2 and 4 Hz with load amplitudes of 15, 25 and 35 kN. Findings – The results of the study demonstrated that as the subgrade degree of saturation decreased from 100 to 60%, the ratio of stress in the lateral direction to stress in the vertical direction generated in the middle of the subgrade layer decreased as well. On average, this ratio changed from approximately 0.75 to approximately 0.65. Originality/value – The study discovered that as the test proceeded and the number of cycles increased, the value of negative water pressure (matric suction) in the case of unsaturated subgrade soils declined. The frequency of loads had no bearing on the ratio of decline in matric suction values, which was greater under a larger load amplitude than a lower one. As the test progressed (as the number of cycles increased), the matric suction dropped. For larger load amplitudes, there is a greater shift in matric suction. The change in matric suction is greater at higher saturation levels than it is at lower saturation levels. Furthermore, it is seen that the load frequency value has no bearing on how the matric suction changes. For all load frequencies and subgrade layer saturation levels, the track panel settlement rises with the load amplitude. Higher load frequency and saturation levels have a greater impact.

The conventional methods follow in designing piles adopt the assumption of saturated condition of soil depending on soil parameters at saturated condition while at most cases the whole piles or part of them lays in unsaturated soil zone, thus the estimated pile capacity will be far of the real. This issue made the need to study the pile capacity at unsaturated condition and compare it with saturated condition. This study is performed to investigate the behavior of single pile inserted in clay soil at different degrees of saturation. The test was performed under axial compression loads by using different degrees of saturation (100,80,60,40%). A pile of 14x14 mm cross section with different slenderness ratios (L/D) (24,30,36) employed in the study. The impact of saturation degree, matric suction and slenderness ratio on pile load capacity is examined. The results illustrate that pile capacity influenced considerably by the saturation degree, matric suction, and slenderness ratio. The results showed that when saturation degree reduced from 100% to (80,60,40%), bearing capacity of pile increased for all L/D used. An example ultimate capacity of pile with L/D (24) increased (380, 512, 63%) by de-creasing degree of saturation from 100 % to(80 ,60 ,40%) respectively, this means the pile capacity increased about four times by decreasing Sr. from 100 % to 80 % , five times by decrease Sr. from 100% to 60 % and little increase (63 %) in pile capacity by decreasing Sr. to 40 %.A close results had been observed at L/D 30 and 36. The effect of increasing slenderness ratio had been studied at different saturation degrees, an ex-ample by increasing L/D from 24 to 30 pile capacity increased (11.45, 10.2, 25, 32.5%) at Sr.(100 ,80 ,60 ,40%) respectively.

Earthquakes are sudden and unpredictable natural activity that causes severe damage. As a result of the increasing seismic activity in Iraq, it has become necessary to conduct a study on the impact of earthquakes and methods of damping them. Since traditional seismic damping methods for construction are very expensive, alternative solutions are necessary. Therefore, this research proposes a new damping method that depends on surrounding the piles with rubber crumbs, as the rubber works to dampen the seismic force before it reaches the piles before moving to the structure. This method is considered a type of sustainability. The study included a set of variables, including (the thickness of the rubber that surrounds the piles, and the position of placing the rubber that sleeved the piles). The tests were carried out using the shaking table device. The results showed that surrounding the piles with rubber gave distinct results in damping the seismic force and it is considered an easy damping method due to its ease of implementation, as well as its economic feasibility. The results showed for the models that surround the rubber in the upper part of the pile, an increase in the values of the acceleration of the structure and a decrease in the values of the movement speed of the structure, the values of the lateral displacement of the structure. The models in which the rubber surrounds the middle and bottom part of the pile, the results were close to the reference model.

The theoretical and practical studies of the cyclic loads resulting from the movement and passage of trains on the unsaturated subgrade to determine the effect of the degree of saturation and moisture content on the foundations and infrastructure of the railway lines, especially the settlement in the railway lines as a result of the development of the train loads. Thirty-six laboratory experiments were carried out using models that simulate a railway with nearly half the scale of the real one, using an iron box of (1.5 × 1.0 × 1.0) meters and a layer of clay soil with a thickness of 0.5 m representing the base layer, were constructed inside it. Above it, there is a layer of crushed stone representing a 0.2 m thick ballast, topped by a rail line of 0.8 m long installed on three sleeper beams with dimensions of 0.9 m (0.1 × 0.1 m). The subgrade layer has been constructed at different saturation degrees as follows: 100, 80, 70, and 60%. The tests were carried out using different load amplitudes and frequencies. These experiments investigated the effect of the subgrade degree of saturation on the value of the stresses generated on the surface and the middle (vertical and lateral stresses) and the settlement of the subgrade. In the case of unsaturated subgrade soil, an increase in load frequency has a clear effect on increasing the generated stresses in the subgrade layer, especially with lower saturation levels. However, the results and measurements of these experiments found that the load frequency almost had no effect on the values of the stresses generated on the surface and inside the subgrade layer with a 100% degree of saturation. The results of the investigation demonstrated that, while load frequency had a minimal effect on track-panel settlement, it increased with the load amplitude and subgrade soil saturation degree. The change of settlement of the track panel with the number of cycles has a high rate at the beginning; after a while from that, it decreases gradually until, after some value of the number of cycles, the settlement changes at a very low rate and gradually.

In this paper, the finite element method is utilized as a tool for carrying out differentanalyses of stone column–soil systems under different conditions. A trial is made toimprove the behaviour of stone column by encasing the stone column by geogrid asreinforcement material .The program CRISP2D is used in the analysis of problems. The program adopts thefinite element method and allows prediction to be made of soil deformations consideringMohr–Coulomb failure criterion for elastic-plastic soil behaviour.A parametric study is carried out to investigate the behaviour of ordinary andencased floating stone columns in different conditions. Different parameters were studied toshow their effect on the bearing improvement and settlement reduction of the stone column.These include the length to diameter ratio (L/d), shear strength of the surrounding soil and,the area replacement ratio (as) and others.It was found that the important increase in strength of stone column occurs when itis encased by geogrid for (length/diameter) L/d = 8 while in case of L/d = 4, a slightincrease in the bearing improvement ratio at the early stages of applying the load isobtained and then the value of (q/Cu) for both ordinary and encased stone columns is thesame.

A finite element method is practical and applicable for many fields including for geotechnical engineering structures. Seepage through earth dam is difficult to analyze especially dams with multiple zones. The problem becomes complex if it requires deformation analysis taking into account seismic conditions. Therefore, finite element is the best tool for analyzing seepage flow in an earth fill dam. The main objective of the paper is to simulate the seepage flow through an earth fill dam. Hassan Kanosh Dam which is located in the north eastern part of Iraq is chosen as a case study. There are three periods in the life of a dam which may be critical from the standpoint of shear failure and which must be analyzed; during construction condition, full reservoir condition, and rapid drawdown condition. The program SIGMA/W which is a finite element software coupled with SEEP/W, (another GEO-SLOPE software product) to analyze the dam. The stability analysis performed showed that all parts of the dam are safe within the prescribed rang of factors of safety for the possible loading and operation cases. It is recommended, however, that close control of the quality of the works during construction must be maintained to realize the shearing strengths necessary to fulfill the assumed strength and even more. It is recommended to check routinely the foundation conditions during excavation to realize the same end results.