| Reflection crack of asphalt surface not only make the road widening subgrade pavement performance aged, affect the comfortableness of driving, but also make road surface water leaching, affect the roadbed strength and stability, under the driving repeatedly load function and the periodic change of environment temperature, the cracks expand quickly, and they short the service life of the coat.For the reason of the emergence and development of widening roadbed reflection crack, it is generally believed due to concrete shrinkage caused by temperature change and traffic load through seams (crack), make the seam near the end of the asphalt concrete material to produce stress concentration, lead to the emergence and development of reflective crack, subgrade length changes while temperature is changing, tensile stress would appears at cracks and seams, cracks arise if tensile strength of asphalt layer is low. the anti-cracking effect and mechanism of the effect is not the same at home and abroad of various types, and all kinds of measures to crack effect is limited. Therefore, how to adopt measures to less or delay the reflective crack of pavement should also according to the actual situation of the widening embankment structure, control from widening subgrade soil and related auxiliary materials and other aspects of asphalt pavement, comprehensive utilization of various measures and methods to achieve the best of crack prevention effect.Depending on the widening project of Lalin-Wuchang-ShengJie highway, through on-site survey and experimental research, the change rules for the foundation properties of new and aged subgrade are compared and analyzed, the control standards of compaction degree are suggested and reliable calculation parameters are provided for numerical analysis. For the properties of deformation and stability of widened embankment, elastic-plastic finite element analysis is used, the rules of related factors which influenced them are studied and then the corresponding suggestions and recommended schemes are provided. Sum up the displacement rules of subgrade in widening project, develop the appropriate technology and methods of construction, propose control measures of embankment settlement and develop the appropriate technical standards.For the aged and new combining department of subgrade easy to have two kinds of cracks form, with geogrid reflective crack prevention and control as the main research object, the numerical simulation of roadbed fringe produce different crack width and differences of the settlement to the structure stress distribution, and concludes that the best distribution of the geogrid, the applicable conditions for preventing cracks; Through the geogrid and its effect of preventing cracks experimental research, discusses the changing rule of geogrid’s strength and its effect of preventing cracks; Through the different temperature between layers of shear performance analysis, nail down the best asphalt content of asphalt and paving way for different test the best construction plan recommended. The research conclusions have great theoretical and practical significance for improving the engineering quality and service life of highway widening project. |
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