Study On Settlement Mechanism And Regularity Of Silty Soil Subgrade

According to the data of the physical mechanical test and dynamical test of silty soil property, all kinds of mechanical properties are systematically analyzed. The settlement mechanism of silty soil subgrade is emphatically discussed according to the mechanical properties. A method of settlement calculation of silty soil subgrade has been put forward . The measured data of silty soil subgrade settlement has been collected based on a field settlement observation scheme of a freeway designed in Puyang City. Compared with these observed data, calculated result fits well.The following main achievements are obtained by study in this dissertationA series of tests have been carried out, such as standard indoor compaction test, static compaction test, direct shear test, permeability test, axial compression test, dynamic tri-axial test in great strain state. Static and dynamic mechanics characteristics of silty soil have been systemicly realized. The relationships have been obtained of static pressure versus permeability coefficient (k), static pressure versus void ratio, dynamic modulus of elasticity versus dynamic strain, dynamic shearing strength versus dynamic shearing strain and degree of compaction, vibration frequency versus water content, critical dynamic strain and critical dynamic strength, modulus of compressibility versus compaction degree and water content, the difficulties of compaction versus gradation of grain and liquid limit, and so on. Also a convenient new sample making method has been put forward, which is able to make high-quality samples. Furthermore, certain measures have been taken to prevent effectively the influence to test result by the fact of silty soil loosening when encountering water.According closely to the engineering characteristics of silty soil, settlement mechanism is analyzed in detail for silty soil subgrade. An advanced by-layer summation method and modified Duncan-Chang model have been put forward to calculate the final settlement for silty soil subgrade. And according to the disadvantages existing in the one-dimension consolidation theory and the test result of silty soil permeability test, one-dimension consolidation theory has been improved to explain the developing regularity of settlement for silty soil subgrade. As a result, the applied calculation method and theory basic to calculate the settlement for silty soil subgrade has been provided.