JOURNAL OF NEW APPROACHES IN CIVIL ENGINEERING
Year:2017 | Volume:1 | Issue:1 |Papers Count:4

In this paper, the effect of the vertical component of the earthquake acceleration on the seismic bearing capacity factors (i.e. Nq, Nc and Ng) are investigated by employing the method of stress characteristics. By mixing the differential equations of stress equilibrium and the Moher-coulomb failure criterion, a system of plastic equilibrium equations is obtained. The generated stresses in the soil mass under the foot surface and next to it in limit state is calculated by solving plastic equilibrium equation system with the method of characteristics. Results show that, the effect of the vertical component of the earthquake acceleration in absence of horizontal component will cause reduction of the bearing capacity factors Nq, Ng; because having no effect on Nc. The effect of the vertical component of the earthquake acceleration associated with horizontal component will cause reduction resonance on the seismic bearing capacity factors. Using the principle of superposition to obtain of the ultimate bearing pressure of the footing can be a safety.

Passive method is a new way in stabilizing loose soils. This method is as a type of interlocking of soil structure. In order to successfully improve in this method, it is necessary to achieve proper penetration length and increase the shear strength of parameters. Previous studies have shown an increased resistance to liquefaction and decreased permeability due to colloidal Nano silica injection. In this research, sandy soil was mixed with silt in 5, 10 and 15 percent. Then, specimens in dry and saturated conditions were placed under the influence of Nano silica colloid. For determining geotechnical properties of improved specimens direct shear test was performed in three situation (dry, saturated, and grouted). Also, for studying drainage condition after improving constant head permeability test was carried out. The results showed that by adjusting ionic strength and rheometry properties such as viscosity and gel modulus, it is possible to achieve proper penetration length and obtain the required strength for injection in silty sand with a high non plastic fines content. Besides, with the injection of Nano silica colloid, the amount of vertical settlement in the samples decreased significantly. Also, the amount of permeability of the stabilized materials showed a decreasing trend.

Ensuring proper behavior of rockfill dams in several conditions such as during construction, dewatering and operation with considering serious damages due to failure of the dam and existence of multiple uncertainities in basics, assumptions and design parameters of dam is important object and inevitable. Main idea of this paper is study of behavioral dams with using instrumentations. Maroon rockfill dam is located in 19 kilometers of behbahan city in Khuzestan province. This dam with 165 meter heigth is one of the high dams in Iran. In this research in five years of operation period behavioral of Maroon dam was performed. With considering numerous data of instrumentations in dam with design diagrams for important parameters such as settlement, pore water pressure, total stress, strain and water leakage behavior of dam was evaluated.

Anchored soldier piles and lagging walls (Berlin Wall) is one of the modern methods to excavation stabilization in recent years. The aim of this paper is the study of behavior of deep excavation by anchored soldier piles using numerical modeling in PlAXIS 3D software. For this purpose the effect of surcharge loading, mechanical properties of soils and length of anchors on deformations and distribution of tensions are studied. In this study, the soil type and the depth of excavation is selected clay and 15meters, respectively. The obtained results show that the surcharge load, mechanical properties and anchor length have a significant effect on the behavior of the excavations. With increasing of cohesion and friction angle of soils, magnitude of deformations and stresses decrease. But increasing of the anchors length has not impressive effect on deformations and stresses.