Study On The Application Of Improved High Liquid Limit Soil In The Widening Of Fill Road Base

As a special soil with wide distribution in the region,high liquid limit soil needs to be improved to meet the relevant specifications before it can be used as roadbed filler because of its low strength,high liquid limit and poor stability.Based on a road widening project,this paper takes the widely distributed high liquid limit soil in the region as the research object and studies the application of improved high liquid limit soil in the widened fill roadbed through indoor test,numerical simulation and field application,and the main work is as follows:（1）Particle analysis,specific gravity and boundary moisture content tests were conducted on the current soil samples,and the content of soil particles with particle size less than 0.075mm was about 61.65%,the specific gravity of soil particles was 2.73,the liquid limit was 51.32%,the plastic limit was 25.24%,and the plasticity index was26.08.The current soil was determined to be a fine-grained clay with high liquid limit according to the specification.compaction test,bearing ratio test and direct shear test are conducted on the current soil,and the maximum dry density of the current soil is1.67g/cm³,the optimum moisture content is 18.20%,the bearing ratio CBR_2.5is 2.91%,CBR₅ is 2.84%,the cohesive force is 26k Pa,the internal friction angle is 9°,the current high liquid limit soil,the bearing capacity and shear strength is low,does not meet the minimum road base filler strength requirements..（2）Based on the site construction conditions,project cost and other factors,the lime improvement scheme for high liquid limit soil was determined.The engineering characteristics of the improved high liquid limit soil with different lime dose（4%,6%,8%,10%）were studied through the boundary moisture content test,compaction test and bearing ratio test,and the best lime dose ratio was finally selected as 8%.After the direct shear test,the cohesive force of the improved high liquid limit soil is 43k Pa and the internal friction angle is 14°,and the bearing capacity and shear strength of the high liquid limit soil are improved after the lime improvement to meet the construction requirements of road base.（3）The numerical model of widened roadbed filling was established to compare and analyze the construction settlement,maximum principal stress,slope stability and seismic performance of roadbed during the filling of high liquid-limited soil before and after the improvement.The construction settlement of high liquid-limited soil after improvement was effectively controlled,and the construction settlement was reduced by 46.21%;the maximum principal stress of high liquid-limited soil after improvement was reduced by 3.44%;the slope safety factor of high liquid-limited soil after improvement reached 2.38,which was improved by 59.73%;under the action of earthquake,the damage occurred in 0.75s after the earthquake in the high liquid limit soil roadbed before the improvement,and the damage did not occur in the high liquid limit soil roadbed after the improvement,and the seismic performance was greatly improved.（4）In order to reduce the uneven settlement between the old and new roads in the process of widening road filling,low-energy strong ramming is used to strengthen the filled roadbed for the characteristics of the improved high liquid limit soil.A numerical model of the dynamic action of strong ramming was established to determine the optimal ramming parameters by analyzing the settlement,peak stress,reinforcement quality and effective reinforcement depth of the soil after ramming.The actual project shows that the application of improved high liquid limit soil in the widening of the fill roadbed has achieved better results,reducing the project cost and construction period,avoiding damage to the environment and achieving a win-win situation for both economic and environmental benefits.