Print ISSN: 1681-6900

Online ISSN: 2412-0758

Keywords : Unsaturated soil


Effect of Dynamic Earth Vibration on the Behavior of Laterally Loaded Single Pile Embedded within Unsaturated Soil

Maha H. Abood; Mahmood R. Mahmood; Nahla M. Salim

Engineering and Technology Journal, 2021, Volume 39, Issue 12, Pages 1748-1752
DOI: 10.30684/etj.v39i12.508

Most of the studies of laterally loaded piles focused on the behavior for piles subjected to static or cyclic lateral loading embedded within dry or saturated soils, few studies investigate the behavior of piles embedded within partially saturated soils and subjected to dynamic loads. In this research, an experimental study presents an aluminum pile model embedded within dry, fully saturated and partially saturated soils, subjected to dynamic load with the El Centro 1940 NS acceleration data (0.05g, 0.15g, and 0.32g) accelerations. Three different lowering levels of the water table for fully saturated soils model is achieved to get partially saturated soils of three different values of matrix suction. During an earthquake model, a liquefaction phenomenon is observed by boiling of sand and completed collapse in the soil as shown in the results. It is concluded that the resisting to the bending moment reduced by 22%, 50%, and 57% after 1st, 2nd and 3rd lowering of water level respectively, than that of the saturated condition. This reduction approaches to 28% for completely dry soil. It is worth to mention, that, the deflection of the pile reduced as the lowering of water level increased. The soil resistance increases with the increasing of dynamic load acceleration. The soil resistance increases about 35% when the acceleration increase from 0.05g to 0.15g and an increase of about 22% when the acceleration increases from 0.15g to 0.32g.

Variation of Matric Suction as a Function of Gypseous Soil Dry Density

Hussein H. Karim; Qasim A. Al-Obaidi; Ali A. Al-Shamoosi

Engineering and Technology Journal, 2020, Volume 38, Issue 6, Pages 861-868
DOI: 10.30684/etj.v38i6A.550

Gypseous soil is one of the most problematic types of collapsible soils which is affected by many geotechnical factors. The most important factors are the effect of loading and wetting and their relation to soil density, especially when the soil at unsaturation condition. Suction pressure is the main criteria in determining the deformation behaviour of unsaturated collapsible soil when these soils distributed in arid or semi-arid region. In this study, disturbed sample of sandy soil of more than 70% gypsum content is taken from Al-Ramadi city western of Iraq. This study interested to investigate the variation of matric suction with the dry density and their effects on deformation of gypseous soil. For this purpose, a soil-model device provided with high accurate Tensiometers and Time Domain Reflectometry sensors in addition to data logger is designed and manufactured. Tensiometer sensor is used to monitor and measure the matric suction, while the Time Domain Reflectometry is used to monitor and measure the volumetric water content in the soil mass. The results of the tests showed that there is a significant effect of soil dry density on the relationship between the matric suction and water content.

Effect of Suction on Volumetric Yielding Behavior under Different Initial Conditions for Fine-Grained Soils

Yasir Al-Badran; Tom Schanz

Engineering and Technology Journal, 2013, Volume 31, Issue 20, Pages 339-358

The unsaturated soils are difficult to consider within the framework of classical (saturated) soil mechanics. In general, the unsaturated soil is stiffer than the saturated one (hardening), so the location and slope of normal consolidated line (NCL) or the volumetric yielding behavior of unsaturated soil is different from the saturated behavior. This work investigates the volumetric yielding behavior of unsaturated soil; by determine the One-dimensional normal consolidated lines (NCL’s) under different suctions. Two materials namely pure Calcigel bentonite (100B) and a mixture of 30% Calcigel bentonite and 70 % Haider sand (30B) were prepared at two initial conditions (i.e. slurry and loose states). In this type of test, after reaching to the designed suction, the net stress is increased through the test while the suction is kept constant. Thirteen 30B specimens and two 100B specimens were tested under constant suction condition. The constant applied suction in this study was varied from 0 kPa till 39000 kPa because of the possibility to increase the preconsolidation pressure (yield stress) more than 24000 kPa (the maximum limit of the used one-dimensional high stress consolidation equipments). Two techniques (i.e. axis translation technique and vapor equilibrium technique) were used to apply and control suction on tests. The controlled-suction one-dimensional high stress consolidation tests results show that the position and the slope of NCL’s depend on both net stress and suction. The NCL’s either, for low suction value, has void ratio lower than the saturated NCL (associated with slope lower than the saturated NCL), or the NCL has void ratio higher than the saturated NCL (associated with slope higher than the saturated NCL) for higher suction value.

Total and Matric Suction in Unsaturated Soil with the Existence of Different Salts Content

Mohammed Y. Fattah; Asmaa Y. Yahya; Maysam Th. Al-Hadidi; Balqees A. Ahmed

Engineering and Technology Journal, 2013, Volume 31, Issue 20, Pages 280-298

Soils located above the groundwater table are generally unsaturated and exhibit negative pore-water pressures. A soil-water characteristic curve (SWCC) that relates the water content of a soil to matric suction is an important relationship for the unsaturated soil mechanics. The SWCC essentially shows the ability of an unsaturated soil to retain water under various matric suctions. The filter paper method is a soil suction measurement technique. Soil suction is one of the most important parameters describing the moisture condition of unsaturated soils. The measurement of soil suction is crucial for applying the theories of the engineering behavior of unsaturated soils.
In this paper, three soil samples were collected from three sites within Baghdad city in Iraq. These soils have different properties and they were prepared at different degrees of saturation. For each sample, the total and matric suction were measured by the filter paper method at different degrees of saturation. The soil samples were mixed with different percentages of Nacl salt. It was concluded that the suction increases with decrease of the degree of saturation. The relationships between the total and matric suction and the filter paper water content are approximately linear and indicate decrease of suction with increase of the filter paper water content. All soil samples exhibit unique linear relationship between the total suction and filter paper water content and matric suction. When salt exists in the soil, there is a noticeable increase in both matric and total suction.