No abstract

The present study attempts to represent the behavior of shallow foundations under the effect of eccentric inclined loading in terms of the main criteria of design which are the ultimate bearing capacity, permissible settlement, horizontal displacement and tilt. Due to the square shape of the analysed foundations, three dimensional finite element analysis are used. Elastic-perfectly plastic behavior of soil and rigid of foundations was adopted using Mohr-Coulomb criterion, 15-Node wedge elements were used to model and represent the soil and 5-Node linear elements with three degree of freedom to model and represent the foundations in used program PLAXIS 3D TUNNEL version 1.2.The results of analysis were presented in the form of pressuresettlement, pressure-horizontal displacement and pressure-tilt characteristics. Then the ultimate bearing capacity of the foundations were gotten and compared with (Meyerhof, 1956) and (Saran & Agrawal, 1991), a good agreement was found between them. Using the data obtained from the analysis, non-dimensional correlations have been developed for predicting the values of settlement, horizontal displacement and tilt of eccentrically-obliquely loaded foundations. These relationships can be used by the engineers.

Gypseous soil which is used is taken from Tikrit city in Salah Aldeen government and specially from Tikrit University from a depth (1.5-2)m, It’s type is sandy gravely with a small percentage of silt and clay while the percentage of gypsum is (34-36)%, The tests on soil is standard proctor compaction, direct shear, collapsibility and California bearing ratio. The number of samples is (70). The effect of adding concrete waste (2, 4, 6 and 8%) and waste of Asphalt mixture (2, 4, 6 and 8) % on dry soil, as well as the effect of mixture of the optimum percentages of both additions on the properties of gypseous soil, is the aim of the study. Adding concrete waste at optimum percentage (6)% causes an increase maximum dry density at (16)% and a decrease in optimum moisture content at (5)%. Whereas adding concrete mixture waste in its optimum percentage (2)% caused a decrease in maximum dry density values with an increase of optimum moisture content, and when adding mixture of optimum percentage of waste, an increase happened in the M.D.D.(14)% with a decrease in O.M.C. at (4)%. Adding the optimum percentage (8) % for both. Value of cohesion increases (100)% when adding concrete waste with an increase in the angle of internal friction (14)% and a decrease in collapsibility in a percentage of (90)%, while adding waste of asphalt mixture shows an increase in cohesion value (112)% with a decrease in the angle of internal friction (2)%and a decrease in collapsibility in a percentage of (90)%, when adding mixture of optimum percentages the value of cohesion increase (108)% with an increase in angle of internal friction (14)%and a decrease in collapsibility in a percentage of (91)%. Values of California Bearing Ratio in dry and soaked condition increases (49)% when adding (8)% of concrete wastes which is the optimum percentage, while adding waste of asphalt mixture causes a decrease in the value of C.B.R. and the optimum percentage is (2)% , but adding optimum percentages mixture of them causes an increase in values of (52)% in dry condition and (53)% in soaked condition.

Proper dam management should be ensured regularly to avoid breaches and failure. In this study, the finite element method was used to analyse the stability of the Shirin earthen dam under various conditions. The necessary laboratory tests for soils used in the construction of the dam were carried out in the laboratories of the College of the Engineering /University of Tikrit, and these data were employed in the GEO-STUDIO program to analyse the seepage and stability of the dam. The seepage was analysed at three levels of the water lake reservoir including the highest, middle and lowest water levels. In addition, factors such as the permeability of the shell layer, the presence and thickness of the dam’s core layer, the placement of filters at the back of the dam and the exit gradient have been considered. The results have shown that by increasing the permeability of the shell layer, the exit gradient is decreased while the seepage through the dam body is increased. The presence of the dam’s core layer has a significant effect on reducing the amount of seepage through the dam’s body as the amount of seepage is reduced by (99%). Moreover, it was found that the minimum safety factor is 1.95 and it occurs after (4 days) of the rapid emptying of the reservoir, and this indicates that the upstream slope of the dams is safe during water emptying.

This study included (40) tests of loading a square footing (100*100 mm) resting on two layered soils (sand over gypseous soils) using a steel box with the dimensions of (900*900*500 mm). Gypseous soil was brought from Tikrit-University with gypsum content 61%. The tests were divided into two groups. The first groups included (4) tests for gypseous soil only by using the field and maximum densities (14.5, 18.75 kN/m3) respectively, without soaking and with soaking where gypseous soil lost a great value of its resistance. The second group included (36) tests of loading two layers of soil by replacing a layer of gypseous soil by sandy soil with relative density (30%, 60%, and 80%) and depths (B/2, B and 3/2 B). The results showed that the replacement process gave an improvement in the bearing capacity when the gypseous soil was compacted to field density and soaked with a relative density of sand (80%) while the other cases did not have any improvement. The results of loading the two layers of soil also show that the soaking of gypseous soil under the sandy layer affects on the resistance of sand through reducing it especially when the depth of sand was (B/2) this effect decreased gradually with increase in the depth of the sandy layer.