Expansive Soils Stabilized By Lime Used In Filling Highway Embankment

Subgrade soils of a highway in Anhui province are recognized as problematic soils since they exhibit low strength, high swell and shrinkage characteristics. These properties weaken the subgrades and cause severe damage to the pavements and it display high swell potential under high degree of consistency and the expansive soils with lower volume change potential maintain the CBR values very lower than the request of minimum strength for the fillings used in embankment of highways. According to the problems in recent research, the aim and plan of this task are proposed.In the present thesis, the strength, swell and shrinkage characteristics of the soil and the soil treated with lime were evaluated based on the normal experiments used to test the soil. Base on indexes of free swelling ratio, Atterberg limits, grain distribution and some other physical property, this soil should to be identified weak expansive soil and high liquid limit clays. A new compaction test defined as modified wetting method is more rational for effective control of field compaction than on drying path or wetting path. For compacted stabilized expansive soils, this research has performed laboratory tests to investigate the influence of initial state parameters (water content and dry density) and different testing conditions on swell percent, swelling pressure, CBR value and modulus of resilience. On the basis of investigation results, the concept of the initial physical state or the consistency is developed, and then the initial consistency is discovered to have a significant relationship with swelling and strength characteristics. According to tests of EDTA titration, the lime-treated expansive soils displayed significantly deduction in EDTA titration for longer periods of mellowing. The higher the limes content of lime-treated expansive soils, the larger the reduction in EDTA titration. While the lower the water content, the larger the reduction. So the calibration curve for the effect lime content of lime-treated soils affected by the curing time has been measured using at EDTA titration.Expansive soil improved with relative low lime content (<5%) as fillings used in highway embankment has displayed lower potential for massive volume change. It can be accepted for the compacted expansive soil mass that decreasing the volume change potential with proper increasing its initial water content and decreasing its initial consistency. The optimum lime-additive amounts and checkout criteria can be decided from swelling and shrinkage characteristics and strength of expansive soils improved with lime.