The objective of this paper is to numerically study the behavior pipe pile under axial compression embedded in organic soil has been numerically predicted. The pipe pile used in the study has been produced by steel and it has outer and inner diameters of 20 mm and 15 mm, respectively. The pile embedded in organic soil, which has the pile length ratios of 10, 20 and 30 (L/D), has been exposed to the axial load for different diameter ratios (d/D = 0, 0.25, 0.50 and 0.75). Numerical analyses have been performed by using Plaxis 3D computer program which is based on finite element method. The capability of the numerical analysis in the prediction of the load capacity of pipe pile has been studied. It has been understood that the results obtained from numerical analysis and experiment are in a good agreement, and then it has been observed in the parametric study that the load capacity of single pipe pile increases with the increase of the pile length and the wall thickness.
Experiments regarding single model piles embedded in organic soil were conducted to determine the effect of pile type and soil density on ultimate pile oblique pull-out loads. Wood, steel, and smooth as well as rough concrete piles with diameters of 20 mm and embedment lengths of 200, 400, and 600 mm (length-to-diameter ratio L/D of 10, 20, and 30) were examined. The pull load was applied at an inclination of 0°, 30°, 60°, and 90° to the vertical axis of the pile. For each inclination angle, ultimate pull-out capacity was determined from load-displacement curves. Test results indicate that ultimate pull-out capacity increased with an increase in L/D ratio. While there was an increase in the pull-out load resistance of wood, steel, and smooth concrete piles when the angle of load inclination increased, there was a decrease in the pull-out load resistance of rough concrete piles when the load inclination angle exceeded 30°. Moreover, ultimate load capacity decreased when soil density decreased. Lateral pull-out capacity exceeded the axial uplift capacity of the steel, wood, and smooth concrete piles, and there was a slight increase in the ultimate load capacity of the rough concrete pile. The ultimate resistance of the piles was calculated theoretically via a semiempirical method and compared with test results. A comparison of the measured and predicted values indicated reasonable agreement pertaining to rough concrete piles and a disconnect regarding the other piles.
This paper herein presents an experimental investigation to explore the performance of organic soil under two stages of consolidation: primary and secondary consolidations. An organic soil with 23% of organic matter has been used in this study at three different molding water contents. Water contents used were optimum water content (OWC), liquid limit (LL), and an intermediate level of water content (MC) between OWC and LL. It was found that more water content, more void ratio, and more consolidation. The calculated coefficient of secondary consolidation C α within a range started from the lower value of 0.0044 for OWC and ended with the upper value of 0.0181 for MC. The molding water content has no significant effect on the secondary consolidation coefficient when the stress has increased, increasing in water content (more than optimum water content) gives fairly close values of coefficient of secondary consolidation (for MC and LL), and the coefficient of secondary consolidation has increased when the water content increased.
This study was undertaken to investigate some specific problems that limit a safe design and construction of structures on problematic soils. An experimental study was carried out to examine the influence of loading rate and moisture content on shear strength of organic soil. Influece of moisture content on interface friction between organic soil and structural materials was also attempted. A commonly used soil in Iraq was prepared at varying moisture contents of 39%, 57% and 75%. The experimental results showed that the increase in water content will decrease the shear stress and the internal friction angle. An increase of the shearing rate was found to decrease the shear stress and internal friction angle for all percetanges of water contents. Further, direct shear tests were carried out to detect the interface shear stress behavior between organic soil and structural materials. The results revealed that the increase in water content was shown to have significant negetavie effects on the interface internal friction and angle shear strength.
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