Abstract
One of the Iraqi geotechnical problems is the presence of gypseous soils covering about (27-36) percentage of Iraq soils containing gypsum between (10-70) ratios. The main reason for soil problematic is the gypsum dissolution when these soils are inundated. However, the soluble gypsum can be leached out of the soil particles, so these problems can be led to cracking, tilting, and collapsing the related soil structure and changing the soil properties. The aim of this work is to investigate the performance of under-reamed piles as a new, improved method to reduce the moisture sensitive and the primary triggering mechanism for the volume reduction of collapsible soil, which is considered as a non-elastic deformation; this was done by carrying series of inundation these soil with using different types of under reamed piles to arrive the best and suitable type useful in gypseous soils. The piles with reams are concrete piles with one or more ream, so under-reamed piles are suitable in weak soils where sizable ground movement, variations, filed up ground, silty clay, and loose sand which has the advantage to increase the soil strength. This paper includes the experimental model of under-reamed piles under static load simulated by a steel plate on the pile cap, then the load-settlement curve, friction force, and bearing force founded from the investigation of different patterns of reamed. It was found that a number of bulbs had a significant reduction on settlement reach to 93% in case of using triple under-reamed pile which is the greatest results in comparison with other patterns and reference pile of the uniform cross-section in the wet state.
Highlights
Many of the engineering problems are confronted due to the degradation of gypsum when such soils by water wetting, soaking, or leaching, especially in sandy gypseous soils, so these issues are normally prompted to break, inclining and collapsing the connected structure [1,2]
The results show that the under-reamed pile's bearing capacity is higher compared to the straight shaft, about 305%
In this study, the bearing capacity of the under-reamed pile in collapsible soil was experimentally observed by changing the geometry of the under-reamed pile position, spacing, and numbering of the bulb
Summary
Many of the engineering problems are confronted due to the degradation of gypsum when such soils by water wetting, soaking, or leaching, especially in sandy gypseous soils, so these issues are normally prompted to break, inclining and collapsing the connected structure [1,2]. Al-Busoda and Al-Rubaye [3] scanned the selected soil characteristics from Salah-Aldeen Governorate 70% gypsum content in dry and soaked conditions. The effects noted that the angle of internal friction is diminished marginally to 12.2% and 9.2% after soaking for 6 and 24 hours individually. The effects shown that the cohesion properties have a considerable lessening 91.5% and 94.2% after saturated for 6 and 24 hours respectively compared to dry conditions [4]. It is intended to opponent the reduction in the collapsible soil properties under soaking conditions. Al-Zabedy and AlKifae [5] observed that geogrid improved the bearing capacity of gypsum-soaked soils from 275 kN/m2 before using reinforcement materials 415 kN/m2
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