Research On The Engineering Behavior And Dynamic Response Characteristics Of Unsaturated Lime-treated Expansive Soil

Based on the features of roadbed soil under train load, lime-treated expansive soil was researched systematically, according to the indoor experiment, about its characteristics of strength and deformation under static and dynamic loads. The main results are summarized in the following:Firstly, on the basis of compaction peculiarity and unconfined compression strength of lime-treated expansive soil analyzed, the ratio of lime (3.0%) and controlling factors of making sample were determined by contrasting to the unconfined compression strength of field lime-treated expansive soil and some related standards. Then the pressure plate test was used to measure the soil-water characteristic curve(SWCC) of lime-treated expansive soil using the axis-translation technique, it was found that the result was far from that of intact expansive soil. Contrasting the intact expansive soil to lime-treated soil, the value of in-taking area decreases from 210kPa to 67kPa, but the residual water content increases from 13.5% to 16.5%.Secondly, triaxial strength of unsaturated lime-treated expansive soil was researched by using unsaturated triaxial test. The type of stress-strain curve of lime-treated soil is the specific stress softening type, which shows the brittle character of lime-treated soil. However, the curve type of saturated remoulded expansive soil is stress stable or hardening type, showing the plastic character instead. Furthermore, the cohesion of both the lime-treated and remoulded expansive soil increases with water content declining. The friction angle also changes, when the water content is different, instead of a stable value for all time.Thirdly, through the experiment of dynamic triaxial test of lime-treated expansive soil, main experiment curves between the relation of dynamic modulus and dynamic strain, water content or cell pressure were achieved. The damping ratio of whole strain is calculated, according to the equation of equivalent damping ratio, founded by Hardin-Drnevich. The impact of consolidation ratio and cyclic frequency is analyzed as well. The dynamic modulus increases, as long as the consolidation ratio raises. On the contrary, the frequency affection to dynamic modulus is subtle. The influence of water content and cell pressure to damping ratio is also small. Instead, the damping ratio is influenced remarkably by frequency and consolidation ratio, between which the influence of frequency is outstanding. With the increasing frequency and the decreasing consolidation ratio, the damping ratio raises.Finally, the characteristics of critical dynamic stress of lime-treated expansive soil was analyzed based on the research of dynamic behavior. The critical dynamic stress stays stably between the range of 190kPa and 200kPa, no mater the condition of samples is different or not. Although the influence of water content and frequency is limited, the critical dynamic stress is still showing the trend of declining depending on the increasing water content and frequency, which is more closer to 190kPa.