Research On The Physical And Mechanical Poperties Of Alluvial And Lacustrine High Liquid Limit Clay Used As Subgrade Filling

High liquid limit clay is widely distributed in the Yellow River alluvial plain as lacustrine sediments or silt interlayer. For its high plasticity, high viscosity and bad water stability, it is very difficult to compaction. Recently, high liquid limit clay is generally replaced or modified in accordance with the specification when building roads in such areas. The traditional method will cause the waste of land resources and increase the project cost. Therefore, research on the method of the directly using and economy modification of the high liquid limit clay is of great theoretical significance and engineering application value.This study selected the typical alluvial and lacustrine high liquid limit clay along Jining-Xuzhou Expressway to reveal its physical properties, compaction properties, and mechanical properties under different moisture content and compaction state through laboratory test. In view of the strength requirement of road bed, study on the modification of the high liquid limit clay is proceed. FLAC3D is used to analysis the deformation and stability of the subgrade in order to put forward the critical control index such as moisture content and compaction while the subgrade compaction. The laboratory test and numerical simulation results show that:(1) The particles is given priority to silt and clay particles, and it has high clay mineral content. Its plasticity index is very high, while the plastic limit is low. Therefore, this kind of soil has high viscidity, hydroscopicity and water retention, which showed the properties of both silt and high liquid limit clay. The compaction is sensitive to moisture content, and prone to spring when the moisture content is higher than 4% above the optimum moisture content.(2) The mechanical properties such as CBR value, shear strength, modulus of resilience and compression modulus showed the same regularity that the properties increase with the increase of the degree of compaction and decrease with the increase of moisture content. The moisture content is the main factor that influence the mechanical properties. While the moisture content is no more than 4% above the optimum moisture content and the compaction degree is higher than 90%, its strength is higher, no soaked CBR value meet the minimum requirements of embankment filling of specification.(3) The effect of lime modification and small dosage of fly ash and lime modification is remarkable, and the appropriate processing time is 3 to 4 days. The CBR value of modified soil in more than 10% when the compaction degree can reach 90% that meet the minimum requirements of roadbed filling of specification.(4) When the alluvial and lacustrine high liquid limit clay is used as embankment filling, the control moisture content can increase by 4% on the basis of the optimum moisture content and the compaction degree can decrease by 3% on the basis of the requirements of specification, the deformation and stability of the subgrade is sufficient.