توفيق عامر جواد شير علي

In footings construction, it is very important to protect the reinforced concrete in direct contact with the soil from the ground water attack, especially if it is consisting of risky salt such as NaCl. One of the main objectives of this paper is to study the effect of ground water NaCl attack on the compressive strength and on steel reinforcement of footings, which is usually subjected to ground water. The experimental work consists of two main stages; first is preparing plain concrete and reinforced concrete for ordinary and high strength concrete and the second stage is finding the compressive strength and reduction in the weight of reinforcement (Corrosion) after curing the specimens in salty water of NaCl concentration 4000 mg/l. The important conclusions are the compressive strength of concrete decreases when the concrete is submerged with salty water (NaCl) with percentage decrease 51% for ordinary concrete (OC) and 38% for high strength concrete (HSC). Regarding the effect of concrete cover on reinforcement, the results show that the corrosion in steel reinforcement decreases when the concrete cover increases. Finally, use of high strength concrete and a suitable concrete cover are very useful in protecting the reinforced footings and in improving durability.

The presence of gypsum in soils causes significant changes in the behavior and alters the properties of these types of soils. Gypsum and anhydrite rocks are often found in many countries of the world in extensive deposits. It was known in Greek as Gypsosa, in German as gips (which could be probably derived from Greek) and in Latin as gypsum. Large area in middle and west of Iraq is classified as a gypseous soil. This paper aims to study the benefit of using Netlon CE121 geogrid as reinforcing material on CBR (California Bearing Ratio) which is adopted as an indication for treatment. A laboratory tests were performed on a gypseous soil samples to study the effect of the first layer location (u) of geogrid and soaking on CBR are studied. 4, 15 and 30 days are adopted as a period of soaking. CBR corresponding to 14 kN/m3 is adopted as a reference value to make the comparisons. The results show that the use of geogrid reinforcement increase the value of California Bearing Ratio (CBR) and the location of first layer of geogrid under the surface have a large influence on CBR, the reliable depth is 0.15D where D is the diameter of CBR mold. CBR value for the optimum point increased almost two times when compared with unreinforced soil. Also CBR decrease when the period of soaking increases for unreinforced and reinforced soil. The experimental results shows that the ultimate bearing capacity increase when CBR increase for unreinforced and reinforced soil.

An experimental study of the strain behavior of high strength geogrids used to reinforce sandy soil under a 60 x 230 mm rectangular footing is conducted. The effect of two types of geogrids on the bearing capacity of the composite is investigated as well. Three layers of Netlon CE121 and Tensar SS2 geogrids were used. The first layer was positioned at 0.25B below the footing base while the third layer at a depth of B below the base where B is the footing width. The main aim of the study is to measure the strain and elongation occurring in the ribs of Tensar SS2 geogrid. The peak tensile strength of Tensar SS2 geogrid MD/XMD is 14.4/28.2 kN/m and it is 6.4 kN/m for Netlon CE121. TML strain gauges and other compatible accessories are used. The sand is statically loaded; the relative density was 71.8 % using a raining technique. It is found that the use of geogrids produces a bearing capacity ratio of reinforced to unreinforced sand of 2.35 and 2.9 for Netlon CE121 and Tensar SS2 respectively. The results revealed also that the measured strain and elongation in the ribs decrease as the depth of geogrid layers increases and as the horizontal distance from the footing centre increases as well. The strain in geogrid ribs practically diminishes at a depth of about the width of footing (B) and at a horizontal distance of about 2.33B from the centerline of footing. A maximum rib strain of about 0.0001 was measured corresponding to a maximum footing bearing stress of 363 kN/m2.

The soil properties are an important parameter for architectural and structural design of structures. Al-Najaf city in Iraq is a famous tourist destination, so in the last one decade a number of multistory buildings, bridges, highways, schools, hospitals, etc. have been constructed. This study investigates the properties of the soil to give a base data, which can be used for the future construction design. The physical and chemical soil properties were investigated and analyzed. The results show that the most of the soil is classified as a sandy soil with little fines having a cohesion varying from 0 to 13.2 kPa and angle of internal friction varying from 26.3 to 41.2 degrees; while liquid and plastic limits (LL and PL) vary from 21 to 29% and from 11 to 15% respectively. The low values of LL and PL for the soil of western locations increase towards the eastern locations. The values of maximum dry density and optimum moisture content vary from 17.5 to 19 kN/m3 and 8.6 to 13.2% respectively. The studies also show that the organic content and sulphate content have a low varies between 1 and 2.9% and 2.2 and 2.7% respectively while the gypsum content varies from 13.6 to 28.3%. The assemblages of gypsum soil concentrated in the west side of the city.

Recently, a fast evolution of structures in urban centres attended by a dearth of beneficial areas has pushed the specialists to recover soil properties in order to carry the applied loadings of structures. One of the technology of soil advancement is use of admixtures. In Iraq, the tires Reclaim are produced by Ministry of Industry and Metals with low costs because it is considered as a by-product of tires manufacturing. This paper concerned with investigates the use of Reclaim as additive to soil. The effect of Reclaim on California Bearing Ratio (CBR) of sandy soil is studied. Many of laboratory tests was carried out on the original soil (0% Reclaim) and using 0.5%, 2%, 4% Reclaim by the weight of soil. A CBR laboratory tests on soil samples without and with Reclaim under 4 days soaking condition to simulate the long-term soaking case. The results show that the dry unit weight of sandy soil increase when the Percent of Reclaim increase. Also, for all cases (0%, 0.5%, 2% and 4%) Reclaim, CBR increase as the dry unit weight increase for each case. The main important conclusion conducted that CBR decrease when the percent of Reclaim increase, thus, use of Reclaim do not improve the soil to carry the applied loads, the increment in CBR varies from 7.6% to 68.8%.

In consolidation theory the pore pressure is outlined as the dissipation over the hydrostatic pressure or the pore pressure in excess of steady state flow condition. The main goal of this study is to formulate the finite difference method by which calculate the pore pressure use MATLAB software and study the effect of load, coefficient of consolidation (Cv) on the value of the pore pressure progressing in two different layers of clay soil. The variation of pore pressure with time within the depth of soil layers is investigated also. A parametric study for three case of load which are fill, strip and rectangle is conducted. The main conclusions of the study outlined that the pore pressure increase with increase the load, the increase more significant for fill load smaller than strip and rectangular loadings. Also, the pore pressure at threshold between two layers increase with the increase of the consolidation coefficient of the first layer (Cv1) and decrease when the consolidation coefficient of the second layer (Cv2) increase and the pore pressure decrease gradually with time in the first and second layers but it increase at the begin of applying load and then decrease until vanishes at the threshold between two layers

A study of the behavior of two types of geogrids used to reinforce sandy soil under strip footings. Three layers of Netlon CE121 and Tensar SS2 geogrid were used. A series of a laboratory tests were performed to compare the estimate a bearing capacity of sand with and without using geogrids. The aim of the study is to measure the strain and elongation occurring in the ribs of Tensar SS2 geogrid only. TML strain gauges and other required accessories are used for this purpose. The soil is loaded with a rate of loadings 1 mm/s in order to simulate a static loading case with relative density of sand as 71.8 % using raining technique. It is found that the use of geogrids gives a bearing capacity with geogrid to bearing capacity without geogrid (BCR) of 1.9 and 2.5 for Netlon CE121 and Tensar SS2 respectively. The results founded also that the strain and elongation decrease gradually when the depth under footing increases as well as the distance from the centerline of footing. The strain in geogrid r ibs approaches zero at a depth of about the width of footing (B) and a distance of about 3.6B from the centerline of footing. The strain and elongation have vanished in the third layer located at depth B beneath the footing.

Probably the most common type of deep foundations is the pile foundation. Piles are defined as relatively long, slender, column-like members. The piles is constructed with a pile cap in most of work of buildings and bridges. The piles in this case are considered carry the load alone and the cap only distribute the load on piles, this system is called piled-raft foundation. The aim of this paper is study the behavior of piled-strip system under a rate of loadings of 1 mm/s as a static loading and presents the sharing between footing and piles in. The sand container is manufactured to contain the soil using inside dimensions of 1 m long, 0.5 m width and 0.6 m depth. The box consists of four steel side frames and a steel base frame which are connected to each other by bolting and welding to form the box frames of the model. Strip footing model is manufactured to represents the pile cap of which encloses the piles under the columns load. The model was made of steel plates welded to transform the load using two v-shaped grooves to house the knife – edge loading blades. To achieve a plane strain condition the dimensions of footing are chosen to have 0.49 m length, 0.135 m width, and 0.2 m height. To achieve the plane strain piles conditions of piles footing, the steel frame with the dimensions of 0.49 m length, 0.4 m depth, and 0.03 m thickness is enfolded by 1 mm aluminum plate. Abrasive papers were glued to give the required roughness to simulate the piles in site. An experimental tests shows that the two capacities of pile, end bearing capacity and skin friction resistance sharing with 75.6% and 24.4% of piles capacity respectively. The results show also that the settlement is smaller for piled-strip system than the piles alone. The results also show that the sharing of footing in capacity with a 33.8% and the piles with 66.2%.

The use of soil reinforcement has become widely adopted due to successive development of different types of geosynthetics. Although soil reinforcement had gained wide acceptance in other countries, Iraq is still hesitated to adopt the system. This paper is an economic study to investigate the feasibility of using geogrids in the foundation of interchange bridges, resting on sandy soils, instead of piles. The design restrictions are imposed as design constraints in the analysis of both cases (geogrids and piles). Choice of the design parameters are made in a way that fit local circumstances in middle and south Iraq considering common safety factors. Three layers of two types of geogrids are analyzed namely Netlon CE121 and Tensar SS2. MATLAB package program is used for optimization. The constraints and the objective function are designed to optimize one unit block of foundation (under one piles cap). Tables of optimal costs and figures showing cost behavior for different combinations of loads and angles of internal friction of soil are presented. It has been found that reinforced soil is considered as cost-effective solution which is much more economical than piles. Based on a typical design commonly used on local scale, cost saving appear to reach (54%).

Cement is expected to provide a stabilization agent to the local granular materials used in roads and airports construction as a sub-base course. The performance-related properties of granular materials have been studied (with and without cement). The effect of cement addition on the results of CBR test and Atterberg limits determination has been studied. The factors which have been selected in this study include cement content, and the aging time after which the specimen has been tested. The ideal (cement /granular materials) ratio has been found as 6% that is give CBR value more than 100% of the CBR value for granular material only. The increment of CBR value due to the cement addition as 6% on the ESAL repetitions until reach terminal serviceability index ρt=2.5 has been studied according to AASHTO Guide. The cement addition as 6% to the sub-base course increases ESAL repetitions by about 45% greater than sub-base course established from granular materials without cement, within the limitation of this study.

The main goal of this study is studying the improvement the engineering properties of soil mass. These properties are shear strength and maximum dry density which are effect on the foundations of the structures and their stability. The cohesionless soil can be given some cohesion by rearrangement of soil particles and decrease the voids between the particles by adding fine particles between them and decrease voids and increase the density, then the required properties can be improved. the chemical combinations due to the additives can also generate new bonded materials give the soil mass a good properties. In this study, the effect of different percent of Bentonite which was added to the soil on the properties of soil. The grain size distribution of soil sample and the classification of soil was (sandy poorly graded) using the Unified Soil Classification. The compaction test was made for (2.5, 5, 7.5, 10)% of Bentonite. The direct shear test was made on the soil sample also for the same percent and the shear strength parameters ( C & Ø ) was improved. The ideal percent of Bentonite can be used is 7.5%.