Study On Lateritic Clay Test In Subgrade Of Highway Subgrade

China has made remarkable achievements for its expressway,which has rapidly grown for nearly 30 years.I once built expressway in Hunan and lateritic clay often appear in engineer.Due to a high water content,lateritic clay is of high liquid limit,plastic limit and expansion and contration.When a large amount of lateritic clay is directly used to fill embankment,it is highly possible to make embankment cracked and unstable at the same time as a result.In consideration of low costs and environmental protection,road workers shall take full advantage of lateritic clay on the premise that security of works is ensured.Thus,we need to have a further understanding of charaters of lateritic clay at first and then evaluate improved lateritic clay so as to get requirements for road design and construction.In this thesis,lateritic clay is sampled from Changde-Jishou Expressway and Changde-Zhangjiajie Expressway.Compression index test for lateritic clay of different depth.lateritic clay,of which compression index is 0.35,is tested.Compaction performances of lateritic clay are studied by means of dry and wet compaction test to analyze reasonableness of wet compaction.On account of a relatively low price for common lime improvement in Hunan,the relation between dry densities is acquired at different amount of blended lime and different water content of lateritic clay on the basis of study on lime improvement.Strength of subgrade is subject to filling materials.Only when CBR of lateritic clay is characterized,filled earth is equipped with the capacity to resist external load.Since CBR test is performed when lateritic clay in subgrade retains water,it means the subgrade is in the most unfavorable state.In this thesis,different CBR is studied for lateritic clay of different water content at different times of compaction.And the relation between compactness and water content,and CBR is analyzed at the maximum dry density.Besides,by study on change of CBR of improved lateritic clay along with different water content and compactness,it is found that lateritic clay improved with lime reaches a relatively high CBR despite a relatively low compactness.Modes of failure,such as landslide and cracking,often occur in embankment.A large number of researchers believe the reason is attributable to insufficient shearing strength of filled earth.Thus,in this thesis,tri-axial test is performed to study on shearing strength at different water content.And parameters in response to shearing strength theory are calculated by the simplified method proposed by academician Chen Zuyu.Besides,impacts of matrix suction on shearing strength of lateritic clay is studied.Shearing strength test is performed for improved lateritic clay of different water content and different lime materials at different ambient pressures so as to analyze relation between parameters of lateritic clay.To analyze difference on dry density of compacted lateritic clay from a micro perspective,distribution of particle diameter of performance is analyzed by mercury intrusion method.In addition,expansibility of compacted lateritic clay is analyzed in combination with characteristics of pore distribution of lateritic clay.Compression characteristics of lateritic clay directly impact compaction of filled earth in subgrade.Thus,compression test is performed respectively for lateritic clay,lateritic clay improved with lime and lateritic clay improved with cement from Dongkou-Xinning Expressway to analyze difference among them.