ریحانه نوری

In general, any damage or breakage in a building's foundation will cause it to settlement, resulting in damage to both the foundation and the structure itself. Considering the extent of the construction, it is important to pay attention to the issues related to the design and performance of the foundation of the structure. From a geotechnical engineering perspective, expansive soils are among the most important soil groups that need to have their characteristics accurately determined before design studies. Such soils cause significant damage to structures. For this reason, the behavior of expansive soils should be investigated and determined in advance to minimize the damage caused to the structure. Shallow foundations such as singular and strip foundations may be affected by non-uniform settlement, rotation, and bending moment due to soil expansion, leading to damage. One of the factors leading to non-uniform settlement and rotation in foundations is water infiltration under the foundation. Often, soil layers near the ground surface, crucial for engineering purposes, are in an unsaturated state. Thus, understanding the precise behavior of soil necessitates the application of complex unsaturated soil mechanics principles. In expansive soils, water infiltration causes a reduction in matric suction and consequently a decrease in shear strength and an increase in soil volume. In this paper, a numerical investigation of the behavior of shallow foundations in two models of singular and strip foundations under changing factors such as pipe bursting and absorption well has been conducted. Using Geostudio SIGMA/W software and Couple analysis, the simultaneous effect of change in matric suction and change in stress and strain has been investigated. Additionally, the effect of the number of building stories and changes in the position of pipe bursting or absorption well on the results has been studied. The analysis of the results indicates that pipe bursting and absorption wells lead to an increase in pore water pressure in the soil over time. Additionally, due to the characteristics of expansive soil, The damage to the structure increases with the passage of time and it has grown more in the first month. Also, the category of damage to the structure is more severe for the models where the one-story structure is built on the foundation. Due to the bursting of the pipe or the existence of the absorption well and also the expansive property of the soil under the foundation, the lower the intensity of the load on the soil or the number of floors of the building, the higher the swelling values of the soil will be. So it is recommended to construction tall structures on this soil. The amount of damage in the case of pipe burst is estimated to be higher than that of the absorption well. In terms of angular distortion, water permeation under the foundation and in neighboring borders, and in terms of horizontal strain, permeation under the center of the foundation are responsible for the most damage. Overall, the damage rating to the structure is higher for singular foundations than for strip foundations, and in many cases, the structure will experience severe damage, thus the use of strip foundations with appropriate thickness for buildings located on expansive soils is recommended.

Buried pipelines are used to transport water, liquid fuel, gas, oil, etc and they must remain in service in all circumstances such as permanent transverse ground deformation caused by slope instability. In the literature, modeling of soil-pipe interaction is carried out by using two methods of soil-equivalent springs and continuum. In this paper, numerical simulation in domain of continuum is applied to predict the behavior of the pipe embedded inside the slope. Problem modeling has been done in the FLAC 3D software by using finite difference method. The effect of parameters such as pipe diameter and thickness, width of the slope, soil adhesion and internal friction angle of soil on soil and pipe interactions were investigated. Comparison of the present numerical model with other numerical, analytical and physical models, indicates that the maximum displacement of the transverse ground and pipe occurs in the center of the area and reaches zero in the sides. Also, the anchor and force in the pipe are symmetric to the center of the model and reach a maximum value in the center. By taking steps such as increasing the diameter of the pipe, increasing the thickness of the pipe wall and reducing the angle of the slope, the displacements, tensions and strains created in the pipe can be reduced to some extent. On the other hand, the internal angle of friction of the soil and cohesion are effective in increasing the soil's resistance and also reducing the deformations in the pipe.