Study On The Dynamic Properties Of Lime Soil Roadbed Filling And Its Applications

Limited by geographic conditions, Soft clay often has to be used for roadbed fillings. Adding lime to soil is a simple and economic way which has been widely applied to improve roadbed fillings in the field of engineering. But the mechanical properties of soil treated with lime under traffic load have not been exhaustively studied. In a sense, the theoretical study on lime soil lags far behind its application in engineering. Therefore, it is of theoretical importance and practical use to study the dynamic properties of lime soil as well as its deformation under traffic load.Based on lots of indoor tests, the mechanical properties, especially the dynamic properties of lime soils were studied experimentally. Analysed by the dynamic elastic-plastic FEM program, the road deformation under traffic load was studied from laboratory data. Main achievements are concluded as follows:1. Adding lime to soil can reduce effectively the plastic index of soft soil. With increment of added lime dosage, lime soil's maximum dry density will reduce, but the optimum moisture will increase. There exists a wider optimum moisture interval on the compaction curves of lime soils than on that of plain soils, which make it easier to control moisture of fillings during construction. Percentage for lime to add in soil should be controlled from 5% to 8% during construction.2. The structure and components of fillings are microscopically analyzed by electron microscopy (SEM) and energy spectrum (EDS), and reticular ettringite crystals were discovered at the first time. Based on the further analysis of the reinforcement mechanism of the improved fillings microcosmically, the cementing materials in fillings are proved to improve the static cohesion c of lime soils.3. DDS-70 digital controlled dynamic tri-axial test was used to study the mechanical properties of lime soil under dynamic loading. It is further verified that adding lime to soft soil is an effective way to improve its dynamic strength. The higher the frequency is, the faster the dynamic strength decays with increasing of vibration number to induce destruction.4. Among many factors affecting dynamic modulus Ed and damping ratio X, Dynamic strain ed is the most important one. Dynamic modulus Ed decreases and Damping ratio X increases very rapidly with the increase of Dynamic strain^. Both dynamic modulus Ed and damping ratio X increase with the increase of vibration frequency and lime ratio. The dynamic modulus increases while damping ratio decreases as the confining pressure