Study On Interlayer Design Of Road Structure With Lime-fly Soil Subbase In Yellow River Alluvial Plain

Under the integrated effect of various factors such as overload, water, interlayer pollution and different properties of each structure layer, the interlayer contact state between each layer of pavement structure is usually not completely continuous. In fact, as the interlayer combination state gradually decays, the real interlayer contact state is between completely continuous and completely sliding condition, whichl leads to the difference of the pavement structure actual working conditon and its design theory. Because the poor interlayer condition is a important cause of semi-rigid grade road early damage, it is necessary to conduct an investigation in the structural system and design method of grade road considering interlayer contact state.Lime-fly soil is widely used as highway subbase in the Yellow River alluvial plain. Because the unique engineering properties of silty soil in this region, the mix proportion design of lime-fly soil is different from the general soil. As lime-fly soil in the area has lower early strength and its late strength is mainly provided by the pozzolanic reaction, so it is not appropriate to use 7-day compressive strength as the mix design strength standard. Therefore, making study on the mix design strength standard of lime-fly soil in the Yellow River alluvial area has important engineering significance.In view of the above two problems, applying ABAQUS finite element software, based on the types of the interlayer damage, the contact nonlinear mechanics characteristics of typical grade road structure were analyzed considering interlayer contact condition. This paper studied the influence to highway structure and fatigue life caused by the change of interlayer contact state, and discussed the structure design method considering interlayer contact condition. In addition, using the lime-fly soil experimental data in the Yellow River alluvial area of Shandong University, combined with the work of compiling Guidelines for Construction of Subgrade and Lime-fly Soil Subbase in the Yellow River Alluvial Plain, this paper conducted research on the mix design strength standard of lime-fly soil in the Yellow River alluvial area.Studies suggest that the maximum tensile stress in the layer above adverse contact surface is more sensitive to the change of interlayer contact state. When the position of adverse interface between two layers is different, the amount of tensile stress mutation generated at interface has large difference, especially when interlayer contact state between undersurface layer and base is poor. The interlayer contact state between bases has greatest influence on the road structure overall strength, and the largest pavement deflection cannot reflect the specific changes of interface condition well. With the poor interface position moving down, the fatigue life controlled by pavement deflection decreases. The interface between underface layer and base is the critical interlayer which influences the fatigue life controlled by the maximum tensile stress of each structure layer. When carrying out lime-fly soil mix design in the Yellow River alluvial area, this paper suggests using 21-day average compressive strength of 1.02Mpa as strength standard value, which is obtained by the lime-fly stabilized soil with<0.005mm soil particles content of 15%.