Performance of partially replaced collapsible soil – Field study

Abstract

Soil collapse occurs when increased moisture causes chemical or physical bonds between the soil particles to weaken, which allows the structure of the soil to collapse. Collapsible soils are generally low-density, fine-grained combinations of clay and sand left by mudflows that have dried, leaving tiny air pockets. When the soil is dry, the cemented materials are strong enough to bond the sand particles together. When natural soil becomes wet, moisture alters the cementation structure and the soil's strength is compromised, causing collapse or subsidence. Based on soil type and density, the potential for encountering collapsible soils throughout most of the project alignment is low. Conditions in arid and semi-arid climates like Borg El Arab, near Alexandria Egypt favor the formation of the most problematic collapsible soils. The behavior and performance of compacted sand replacement over treated collapsible soil by pre-wetting and compaction are investigated in the current study. Field investigation was performed in the form of plate loading tests conducted on compacted sand replacement over improved collapsible soil. Field plate load tests program was developed to explore the effect of compacted sand replacement thickness on collapsibility potential. Treated collapsible soil was replaced with imported cohesionless soil with variable thickness up to footing width. Results proved that the improvement of collapsible soils by sand/crushed stone replacement is possible to control/mitigate their risk potentials against sudden settlement when exposed to water. Replacement soil increases the rate and reduces the amount of footing settlement. For compacted collapsible soils, partial replacement by compacted sand/crushed stone layers decreases collapsibility potential risk. Results also, introduce the development of practical, economical and environmentally safe geochemical methods for collapsible soil stabilization and collapsible risk mitigation. ª 2015 Production and hosting by Elsevier B.V. on behalf of Faculty of Engineering, Alexandria University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/). ª 2015 Production and hosting by Elsevier B.V. on behalf of Faculty of Engineering, Alexandria University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Please cite this article in press as: N.A. Ali, Performance of partially replaced collapsible soil -Field study, Alexandria Eng. J. (2015), http://dx.

Enhancing mechanical behaviors of collapsible soil using two biopolymers

“…Schematic diagram of the used phases in the analysisThe model has been verified by comparing the numerical outcomes with two field test results obtained 1 from plate load test on collapsible soils afterAli (2015) andShalaby (2014) and it was noticed that there is a 2 good compatibility between the field test and the numerical model, which confirms the ability of using the 3 model to predict the behaviour of collapsible soils[35], Effects of inundation on pressure settlement curves 6The effect of inundation on both untreated and treated collapsible soil can be seen in figure13, where 7 the pressure settlement is drawn for untreated collapsible soil and xanthan gum treated soil with a 8 concentration of 2% cured for 1 week after and before water inundation. The ultimate bearing capacity 9 (q ult ) has been calculated from the intersection between the initial tangent and the steeper tangent to each 10 curve [37].…”