Improving Physical Characteristics of Collapsible Soil (Case Study: Tehran-Semnan Railroad)

Collapsible soils which are mainly found in hot and dry regions are generally showing a considerable amount of decrease in their volume by increasing the humidity. This kind of soils could wildly be found in central part of Iran and has caused lots of problems for roads and railroads in that region. One of these railroads is Tehran-Semnan railroad which connect the capital city, Tehran, to central part of Iran. Appearance of wide cracks in the collapsible soil near the rail tracks has caused some worries about the safety and performance of the railroad. However, due to the high traffic of the railroad, it is impossible to block the road for remedy. Therefore using injection method has been found the most suitable alternative to improve the soil along railroad. In this paper, different characteristics of injection of different materials such as lime, cement and micro-silica have been studied. A comparison has also been done between behaviors of soils that have been remedied by injection of these materials. The results of field and laboratory tests revealed that the injection of lime has better effects on improving soil characteristics than the other materials. It will significantly decrease the collapsibility potential of soil in saturate condition and will cause an increase in loading capacity of soil. Lime injection has been suggested as the most appropriate solution for projects with similar geological condition.