Journal of Civil Engineering and Materials Application
Volume:1 Issue: 2, Spring 2017

Spur dikes are river training structures used for prevention of erosion at river banks and cause distancing of flow from the critical zone and creation of local contraction in water flow. In the present study, 2D modeling of the flow pattern around a spur dike in a straight canal with 6m length and 0.45m width is presented. Also the finite element method is utilized for solving the differential equations. Modeling of the turbulent flow around a single spur dike is performed using k- model in 𝜺 ANSYS software and the results were compared to those of the experimental study. The results show that the finite element method, by incorporating the k- model, models the flow pattern around the spur dike well and yields an average error value 𝜺 of 12.57%, and this shows a good agreement between the numerical modeling results and those of the experimental study.

Dynamic rock mechanics investigates the mechanical behavior of rock under dynamic loading conditions and change in mechanical properties of the rock. Loading techniques were almost used for both intermediate and high strain rate tests. In this work, dynamic tests and dynamic mechanical behavior of rock materials were studied. Dynamic tests were discussed to predict the stress-strain behavior. Different dynamic mechanical properties of rock materials including uniaxial and triaxial compressive strength, tensile strength, shear strength and fracture toughness were summarized. The effect of pressure, temperature and water saturation as well as microstructure, size and shape of rock on the mechanical properties of rock materials was considered.

The existing soils in the nature that is used for construction cannot necessarily bear the loadings on the structure. For example, in granular soils, the natural soil may be very loose and show a lot of elastic settlement. Sometimes, there are soft layers, saturated clay and swelling soils at the lower depths, which may cause significant settlement in the structure in terms of foundation load and clay layer thickness. To avoid such settlements, it is necessary to use certain techniques to improve the soil condition. One of the methods that have recently been widely used to reduce the settlement of soft soils and swelling soils is stone columns or single piles. In this research, first of all, the parameters in need for the analysis will be gained by using the experimental data, and then, the static and dynamic behavior of the confined stone columns is examined with geotextile and without geotextile by a group and single manner as in two-dimensional form using Plaxis numerical method of the finite element and the impact of the following parameters will be investigated in both static and dynamic modes: Column length, column diameter, single and group behavior of columns, and soil cohesion effect on the behavior of the confined stone column in geotextile and reduction of soil settlement during use of stone columns. The results of this research indicate correct understanding of the use of geotextile (Woven Geotextile with a specific elastic normal strength) to prevent the camber and the settlement of the column and increase of the strength and bearing capacity of the column.

The tendency to utilize the new technologies has increased due to ever increasing of the population and growing demand for housing as well as the ineffectiveness of traditional construction systems in our country. One of the main goals of using new methods, is to enhance the speed and improve the quality and structures? resistance, which is used in many projects in the world. It has been tried to investigate the effects of new construction technologies from the perspective of construction management on time, cost and quality of construction projects and also study their problems and development issues in the country. The subjects generalities and the literature review are expressed in the beginning of this research, and then the new methods in the world are presented briefly. Following this, the effects of this method on construction projects have been investigated using field studies and experts' opinions. The results of this study indicate that these methods will accelerate the projects time about 50%. Besides, construction costs have increased by about 30% in most individual projects and decrease the costs in mass projects. Most of the use of new construction technologies is in skeletal stage and installation of facilities. In recent years, the owners' tendency to new construction methods has increased in mass production projects. In recent years, the expertise of contractors has also grown and encouraging incentives from organizations like the municipality will lead to the development of these methods in the country. The greatest impact of modern technologies on construction operations is on the integrity and more stability of the structure, the long-term quality of that, the acceleration at the time of construction, better resistance to natural and environmental hazards, such as earthquakes, reducing the costs in massive construction scale, beauty and less harmful effects on the environment, more efficiency of installations and optimizing energy consumption.

One of the most important advances in the civil engineering industry is the application of nanotechnology and concrete performance in combination with some materials in order to improve their properties, behavior and structure, as well as the use of nanomaterials to produce high performance and multi-purpose concrete. Concretes properties, behavior and performance depends on the nanostructure of concrete and cement material which creates adhesion, cohesion and integrity. Therefore, concrete studies at the nanoscale are very important to develop new concrete materials and their applications. In this research, the effect of magnesium oxide (MgO) nanoparticles on the mechanical and practical properties of self-compacting concrete was investigated. Here, self-compacting concrete with different percentages of 1, 2, 3, and 4 of cement weight was made from MgO nanoparticles, and experiments of slump flow, slump flow T = 50 cm, L-box, U-box and V-funnel tests were conducted. The results showed that adding MgO nanoparticles of 2% by weight of cement to self- compacting concrete, increases compressive, tensile and flexural strength respectively by 33%, 20% and 59% at the age of 28-days.