Journal of Civil Engineering and Materials Application
Volume:4 Issue: 1, Winter 2020

This paper aims to evaluate the full-depth reclamation (FDR) technique for the improvement of urban streets in the city of Sirjan from a technical standpoint. Also, experimental results of soil-reclaimed asphalt pavement (RAP) blend stabilized with Portland cement has been represented. The experimental program of this research includes two phases. The first phase includes geotechnical investigation of different pavement layers for assessment of the quality of existing materials and estimation of a structural number of existing pavements, and the second phase includes determination of optimum mix design for the recycled layer (stabilized soil-RAP blend). To this end, unconfined compressive strength and density tests were conducted on several soil/RAP ratios of 100/0, 80/20, 60/40, and 40/60. For each blend, different percentages of Portland cement were mixed to soil/RAP blends and cured for 7 and 28 days. Results showed that by adding RAP to virgin soil, unconfined compression strength and optimum moisture content of stabilized samples decrease. Furthermore, the addition of Portland cement to the mixture increases compressive strength and decreases optimum moisture content. The results of this study also show the significant ability of FDR to increase the structural number of distressed pavements.

In this paper, the gene expression-programming model was applied to present a novel model for the bond strength of concrete and fiber-reinforced polymer estimation. In order to do this, collected data were divided into the trained and tested ones by gene expression programming (GEP) means. The input parameters are the width of fiber-reinforced polymer, the width of concrete, thickness of fiber-reinforced polymer, the elastic modulus of fiber-reinforced polymer (FRP), concrete cylinder compressive strength, and bond length. The output parameters are the bond strength of concrete and FRP. Finally, a novel relationship was derived using the GEP to predict the bond strength of FRP -to-concrete composite joints. Results showed that the presented relationship was more convenient than the other models and that it was a powerful tool to predict the bond strength values of the FRP -to-concrete composite. For example, R-square (R2) of the present work is 0.92 compared to that (< 0.82) reported for other models. Among the models presented by other researchers, that of Dai et al. is more accurate than the other ones, and the model offered by Khalifa et al. has the lowest accuracy.

This work presents in evaluation in regard to the addition of CNTs dispersion in water ultrasound before it incorporation to concrete mass. The dispersion of carbon Nano tubes have been achieved by use of surfactants and other chemical compounds along with vigorous agitation by signification. The various researches have reported varied results experimenting with different amounts of CNTs and different dispersion techniques leading to a conclusion that 0.03 to 0.5% additions of CNTs to cement enhance the properties greatly. Nano particles are filled the porosity of concrete, therefore reduced permeability and increased the concrete strength and its sustainability. In this research, Nano carbon tube for enhancing the physical properties was used. For the experimental work in this research 5 control specimens 50 x 50 x 50 mm and 5 samples containing 0.03% Nano carbon as percentage of sand and cement, specimens were made based on ASTM C349. With considering the results obtained from experiment, the 0.03% CNT multi wall added to the mortar the strength increased by 39%, this can be attributed to the dispersion of CNT in concrete and protecting concrete from progressive cracks. In the other words, treated CNT in composite concrete matrix, provided more surface connection due to high specific areas resulted transferring more forces, so they provided better connection, therefore preventing matrix surrounding from any micro-structures cracks of the samples were also improved properties greatly.

The reinforced elements such as nailing and anchor have been widely used for the stability of excavation and trench because of not taking up a large space, improved soil properties by injection, greater safety and possibility of being used as permanent retaining structure. Due to the complex behavior of reinforced excavation, the stability analysis of reinforced excavation is performed by finite element method. Some factors such as boundary interval, dimensions and type of elements, and type of behavior model of materials affect the numerical results. Due to the complex behavior of the soil stress-strain, influence from stress path and loading history, and existence of groundwater, different behavior models have been proposed to simulate the materials. In this study, the effect of soil behavior model on the response of anchored excavation was investigated. For this purpose, using the finite element method in the plane strain conditions, the excavation reinforced with anchorage system was simulated for different geometrical conditions, and the results of the excavation response were compared for the Mohr-Coulomb, Drucker-Prager, and modified Cam-Clay behavior models. In the shallow excavation, it was found that the Mohr-Coulomb behavior model has the least displacement and the Drucker-Prager behavior model has the largest lateral displacement. The Drucker-Prager behavior model should be considered as a reliable criterion for the design and control of the excavation because of the greater results regarding the lateral displacement of excavation and generally, excavation deformation.

The vulnerability of fluid reservoirs in recent earthquakes and locating of Iran in the Alpine-Himalayan seismic belt and the frequent occurrence of destructive earthquakes, as well as the existence of various faults in our country, results in the safe design and analysis of these structures. Seismic excitations in the near range of the fault have different properties compared to the far fault seismic excitations, such as high-frequency content, long periodic pulses in speed-time history, etc. in the near-fault seismic excitations. Therefore, in the present study, the seismic performance of concrete reservoirs was evaluated by considering soil-structure-fluid interaction under near- and far-fault earthquakes. For this purpose, the finite element method was used for numerical simulation by Abacus software. The nonlinear behavior of the bed and the concrete were modeled with the behavioral models of Mohr-Coulomb and damaged plastic concrete, respectively. The Euler–Lagrange element was used to introduce the hydrodynamic pressure of the reservoir fluid and infinite element was used to prevent reflection of seismic waves and earthquake energy loss in the boundary around the bed. After analyzing the boundary distance sensitivity and dimensional analysis of the elements while validating the simulation of parametric studies, the present study was conducted for variables such as earthquake frequency contents, field earthquake, reservoir geometry, and different bed hardness and practical results were presented by comparing the results.