Instability improvement of the subgrade soils by lime addition at Borg El-Arab, Alexandria, Egypt

- The study shows the different instability problems such as tilting of the power lines cables pillar which is constructed in thick alluvial deposits, which composed of intercalations of sand and mud. Furthermore, it was observed some remarked joints and cracks in the walls of the constructions.
- Lime-addition was used an alternative for improving soil properties. Some clayey sand mixes with Lime, determined gradations, abundant at Borg El-Arab, Egypt. Soils were stabilized and then subjected to moisture density relationship, compressive strength, and CBR tests.
- It was found out that with the adding of lime, grain size distribution of soil samples shifted to coarser side, while the fine particles are cemented with each other, Liquid and plastic limits values of treated soil decreased with the addition of 6% lime; this reduction could be explained by addition of non-plastic material to natural soil and also flocculation of particles due to the chemical reactions.
- Further all tests and reviews, lime can improve the geotechnical properties of the subgrade soils and increase the strength of these soils in compression. The soil treated with lime can be used as high strength base or sub-base materials for geotechnical engineering practices and mitigate the instability problems found at Borg Al-Arab, Egypt.

Subgrade soils can affect the stability of any construction elsewhere, instability problems were found at Borg El-Arab, Alexandria, Egypt. This paper investigates geoengineering properties of lime treated subgrade soils at Borg El-Arab. Basic laboratory tests, such as water content, wet and dry density, grain size, specific gravity and Atterberg limits, were performed for twenty-five samples. Moisture-density (compaction); California Bearing Ratio (CBR) and Unconfined Compression Strength (UCS) were conducted on treated and natural soils. The measured geotechnical parameters of the treated soil shows that 6% lime is good enough to stabilize the subgrade soils. It was found that by adding lime, samples shifted to coarser side, Atterberg limits values of the treated soil samples decreased and this will improve the soil to be more stable. On the other hand, Subgrade soils improved as a result of the bonding fine particles, cemented together to form larger size and reduce the plastiCity index which increase soils strength. The environmental scanning electron microscope (ESEM) is point to the presence of innovative aggregated cement materials which reduce the porosity and increase the strength as a long-term curing. Consequently, the mixture of soil with the lime has acceptable mechanical characteristics where, it composed of a high strength base or sub-base materials and this mixture considered as subgrade soil for stabilizations and mitigation the instability problems that found at Borg Al-Arab, Egypt.