Study On Compaction Characteristics And Resilience Modulus Of Loess

The subgrade is the foundation of supporting pavement structure.Improving the strength and deformation resistance of compacted roadbed is the premise to ensure the smoothness,strength and stiffness of pavement.In the compaction of highway subgrade,the compaction quality of subgrade is usually controlled by the compactness which reflects the ratio of dry density on site to the maximum dry density obtained by standard heavy compaction test.For loess high embankment,heavy hammer compaction and dynamic compaction are sometimes used after layered rolling.At this time,the compaction work applied to the soil is different from the heavy compaction.The change of compaction work results in the change of dense state of soil,which shows different compaction characteristics and engineering properties.In order to master the engineering characteristics of loess subgrade under different dense state,this paper studies the compaction characteristics of loess and the engineering properties of loess subgrade after compaction,taking the complete compaction curve and resilience modulus of loess in a wide range of moisture content as the research object.The main results obtained are as follows:1.Based on the complete compaction curve of loess,the applicability of the four-parameter equation of the complete compaction curve in loess region is verified on the basis of summarizing the four-parameter equation of the complete compaction curve proposed by predecessors.The influence of the parameters of the four-parameter equation on the complete compaction curve of loess is analyzed.The relationship between the shape,size and location of the complete compaction curve and the physical properties of loess is studied,and the influence of the physical properties of loess on the compaction sensitive threshold is analyzed.The prediction of the complete compaction curve of loess is realized by using the complete compaction curve under a certain compaction work and the initial dry density of soil sample under other compaction work.2.Based on the study of loess compaction characteristics,the resilient modulus when the moisture content changes along the curve of complete compaction is analyzed;The effects of moisture content,compaction work,dry density and compaction sensitive threshold on the resilient modulus were discussed.The relationship between the moisture content when the resilient modulus decreases and the moisture content of the compaction sensitive threshold is determined.3.The relationship curve between resilient modulus and moisture content is divided into regions,and the prediction model of resilient modulus is established,and the value and significance of the model parameters are determined.The prediction model of resilient modulus is validated.Based on the curve of the resilience modulus with moisture content under a certain compaction work and the initial resilience modulus under other compaction work,the prediction of resilience modulus after the change of compaction work is realized.4.Based on the analysis of the complete compaction curve and the curve of resilience modulus varying with moisture content,and by using the two boundary conditions of initial dry density and initial resilience modulus,the relationship model between the complete compaction curve and the curve of resilience modulus varying with moisture content is established,and the correctness and applicability of the relational model are verified by engineering examples.Using the relational model,the prediction of the curve cluster of resilience modulus varying with moisture content is realized.