Print ISSN: 1813-0526

Online ISSN: 2220-1270

Main Subjects : Civil Engineering

Numerical Investigation the Failure Mechanism of Left Slope of Darbandikhan Dam

Tareq H. AL-Rahal; Suhail I. Khattab; Bayar J. Al- Sulayfani

Al-Rafidain Engineering Journal (AREJ), 2020, Volume 25, Issue 2, Pages 1-11
DOI: 10.33899/rengj.2020.126573.1013

The aim of this research is to analyze the stability of the left shoulder slope of the Derbandikhan Dam failure due to rainfall and earthquake. This slope consists of unsaturated low plasticity clayey soil. All analyses were conducted by using the Geo-Studio program. The field survey was carried out for the study site and the soil samples were taken to perform the necessary laboratory tests to obtain the required soil properties. The field conditions (Rainfall and earthquake) were simulated, where the slope was exposed to rainfall at (24) mm / day intensity to various periods (10, 20, 30, 40, 50 and 60) days. A slope stability analysis was performed at end of each period. Moreover, another analyses were performed by exposed slope to an earthquake at end of each rainfall period.  Safety factor reached to critical value (1) when slope was exposed to the earthquake after (20) days of rain. 

A Review on Mix Design of Self-Compacting Concrete

Nuha H. Al_jubory; Tuqa Waleed Ahmed; Roua Suhail Zidan

Al-Rafidain Engineering Journal (AREJ), 2020, Volume 25, Issue 2, Pages 12-21
DOI: 10.33899/rengj.2020.126727.1017

In recent years, the use of self-compacting concrete in structures has increased significantly around the world
Many studies have been carried out on the characteristics of this type of concrete with the urgent need to design concrete mix and to find the material ratios used in this type of concrete so far there are no standard mix design self-compacting concrete methods, but there are many types of research to design mixes. Hence the need to review and compare these methods is of considered interest. The review of these studies helps researchers to choose the appropriate method of designing the mixtures of self-compacting concrete and their requirements, whether the strength or workability requirements.

Effect of Water Content and Dry Density on the Shear Strength Parameters for Expansive Soil

Ali Nazal Mohammed; Amina A. Khalil

Al-Rafidain Engineering Journal (AREJ), 2020, Volume 25, Issue 2, Pages 22-29
DOI: 10.33899/rengj.2020.126901.1033

The decrease in shear strength to soil is the cause of many geotechnical problems, especially in clay soils, which may occur due to changes in some soil properties, such as moisture content. Changing the values ​​of moisture content and dry density are important factors that have a clear impact on the shear strength of the soil due to the sensitivity of the soil to such changes, especially expansive clay soils, which requires the study of these factors and their impact on shear strength. The present research aims to study the effect of changes in compaction properties (moisture content and dry density) on the values ​​of shear strength parameters (cohesion and internal friction angle) using direct shear test of expansive soil. Clay soils were selected from the city of Mosul with high expansive properties, and within two sets of tests with a total of thirty compact models. Five percentages of moisture content range between(%32–% 17)  With five percentages of dry density, which ranged between(13.7- 17.7 ).
                The results showed that the shear strength values ​​decrease with increasing moisture content and increasing with increasing dry density at each vertical load . From the results obtained, the cohesion values ​​decreased by increasing the moisture content when dry density was constant and at its lowest value (12.75 ) at moisture content 32%. As for the values ​​of the internal friction angle, they decrease by increasing the moisture content when the dry density is constant and by the lowest value for the angle of internal friction (23.30) at the moisture content 32% and the dry density 13.7 . It is noted that the values ​​of both cohesion and the angle of internal friction increase with increasing dry density and with the highest value of cohesion ( 117.01 ) and the internal friction angle (450), respectively, at a dry density of 17.7 and a moisture content of 17%. 

Soil Reinforcement Using Natural and Synthetic Fibers (A Review)

Abdulrahman Hani Aldaood; Amina A. Khalil; Ibrahim Mahmood Alkiki

Al-Rafidain Engineering Journal (AREJ), 2020, Volume 25, Issue 1, Pages 118-125
DOI: 10.33899/rengj.2020.126506.1006

Soil reinforcement is one of the important techniques in geotechnical engineering, which is used to enhanced the engineering properties of soil. Soil reinforcement means, addition of natural or synthetic fibers to soil which act as tension members and sharing together with soil to sustain the applied loads. In soil reinforcement technique different types of fibers having different shapes can be used. The fibers used in soil can be having a shape like staples, chips, yarns, crumbs, bristles/hairs and other shapes. In the present time the using of fibers (especially natural fibers) in the earth construction works represent one of the cost-effective and environmentally friendly ground improvement techniques. The main objective of this paper, is to review the definition, mechanism, and application of using fibers in soil reinforcement through different scientific papers published in this subject. Further, the advantages and executive problems related to using fibers in soil reinforcement were discussed.

Comparative Rheological and Mechanical Characteristics of Different Warm-Mix Asphalt Additives Under Aging Conditions

Salim Abdullah Khalid; Abdulrhem Ibrahem Al-Hadidy

Al-Rafidain Engineering Journal (AREJ), 2020, Volume 25, Issue 1, Pages 41-48
DOI: 10.33899/rengj.2020.126842.1025

This study compares the rheological and mechanical characteristics of three different kinds of warm-mix asphalt additives (WMAA) namely: natural zeolite (NZ), synthetic zeolite (SZ) and manufactured zeolite (MZ). 40/50 Dora penetration grade bitumen and one dosage of each WMAA were chosen. The resultant WMA binders were subjected to penetration, softening point, ductility, elastic recovery, Furol viscosity, elastic modulus, temperature susceptibility, aging, cracking index, compatibility, extensional viscosity, and shear strength tests. Test results depict that the rheological and mechanical characteristics of NZ and MZ binders are better than SZ binder against resistance to high and low temperature effects.

Strengthening and Rehabilitation of Concrete Prisms Using GFRP Sheets

Ashtar S. Al-Luhybi; Bayar J. Al- Sulayfani

Al-Rafidain Engineering Journal (AREJ), 2020, Volume 25, Issue 1, Pages 17-23
DOI: 10.33899/rengj.2020.126531.1008

The use of external strengthening by fiber reinforced polymer (FRP) technology has significantly increased in recent decades. This is because (FRP) has the properties that make it the most suitable option for strengthening and rehabilitation of damaged concrete structures instead of using traditional materials such as steel plates. In this paper, the behaviour of non-reinforced concrete beams externally wrapped with Glass Fiber Reinforced Polymer (GFRP) sheets has been examined. Fourteen unreinforced concrete prisms were cast with a rectangular section of (150 × 125 mm) and a length of (760mm), these specimens were divided into five group. First group was not externally wrapped with GFRP sheets (control specimens), and the remaining groups were GFRP wrapped with a variable number of GFRP layers (thickness of wrapping). In the first stage of study, the prisms have been tested and the effect of external wrapping and increasing the wrapping thickness on the behaviour of prisms was observed. In the second stage, the unwrapped concrete prisms that were tested and failed (control specimens) were rehabilitated by externally wrapping them with one layer of GFRP sheets. The results have shown that wrapping with GFRP sheets increased the capacity of the prisms and failure load had reached to (342.5%) for prisms wrapped with three layers when compared to the control specimens. It was also noticed that there was an increase in the toughness of the prisms by increasing the number of GFRP layers. The results have shown that there was a decrease in the failure load of the four layer wrapped prisms, and this was due to the early failure of the prisms due to the debonding of the GFRP sheets from the prism surface. The damaged specimens which were later rehabilitated have shown an increase in load carrying capacity compared to the control specimen.

Performance Study of Concentrated Circular Channels System (Orbal) for Removing Nutrients from Domestic Wastewater

Ammar Th. Hamad Al-Tai; Moamen W. Fathel Al-Tak

Al-Rafidain Engineering Journal (AREJ), 2019, Volume 24, Issue 2, Pages 65-73
DOI: 10.33899/rengj.2019.164328

   A biological nutrient removal was investigated as a continuous flow (orbal) system to study the efficiency of system for removing phosphor and nitrogen compounds, and to predict the effect of internal and external recirculation rates on its performance. The pilot plant consisted of three concentric circular channels: outer, intermediate and inner in capacities of 24, 16.8 and 8.7 m3 respectively. The last sedimentation basin has sludge return system to the outer channel. Pilot plant also has an internal cycle to return the mixed liquor from the inner channel to the intermediate one. Continues Flow was used to feed the plant with raw municipal wastewater from Al-Khadraa residential quarter at an average flow rate of 66.7 m3/day. The plant was equipped with a modified surface aeration system operating in total power equal to 0.48 kW to achieve the required dissolved oxygen concentrations in the outer, middle, and inner channels:  0.38, 1.3, and 2.4 mg /L respectively. The three-channel was operated on two levels of returned activated sludge (RAS): 60% and 80%. It has three levels of internal cycle (IR): 100%, 150% and 200%. The results showed: the total removal efficiencies of phosphorous, and ammonia were in the range of: (93.3% - 88.5%) and (93.5% - 92.4%), respectively. The results meet the Iraqi standards for wastewater disposal into rivers. This study revealed there is no significant correlation between removal efficiency of ammonia with the internal and external recirculation ratios, while the effluent phosphor concentrations significantly affected by RAS and IR ratios. This study adopted the hypothesis: the process of simultaneous nitrification and denitrification (SND) occurs in the outer channel, while the phosphorus removal by the pilot plant was performed by the mechanism of enhanced biological phosphorous removal (EBPR).

Neighborhood Sustainability Evaluation Based on UN-Habitat … Principles: Case Study Masike and Avro city in Duhok

Layla M. Raswol

Al-Rafidain Engineering Journal (AREJ), 2019, Volume 24, Issue 1, Pages 26-34
DOI: 10.33899/rengj.2019.163124

The aim of this research is to introduce guidelines and concepts to optimize the urban Design and planning for residential area and to contribute to the sustainable housing development in Kurdistan cities. The Housing Sector as one of the most important sectors in the city development has facing a lot of challenges in terms of sustainability due to the rapid population growth in cities of Iraqi Kurdistan. The city of Duhok as an example of other cities in the region has experienced dynamic urban growth in the last decades as a result of the unstable political and economic conditions in the Region. The local government has tried to cover housing shortage by many strategies such as plot distribution as well as supporting investors to provide housing units to meet people 's housing need. The main research objective is to evaluate the urban sustainability of the selected neighborhoods in the new developed area of Duhok city. The research used the principles of UN- Habitat for analyzing neighborhood sustainability by quantitative measurement of: efficient streets network, high density, mix use, social mix and limited land use specialization. The research outcomes indicate that there is an urgent need to direct the urban growth to more walkable mixed land use neighborhoods rather than car-oriented development by integrating the urban sustainability principles in the new housing projects to create healthier living environment for the residents.