Study On Detection And Treatment Technology And Mechanical Behavior Of Voids Beneath Cement Concrete Pavement

The study on the detection and treatment technology and mechanical state of voids beneath cement concrete pavement are the key content. However, there still has been no comprehensive and systematic study on them, and the content and degree of some studies can not meet the requirements of engineering. It restricts the development and application of study on voids beneath cement concrete pavement to a certain extent. Hence, based on the study at home and abroad and Yantai-Weihai highway testing part as attaching project, this study analyzes the detection methods, evaluation criteria, mechanical state and treatment technology of voids beneath cement concrete pavement.(1) Analysis of the evaluation system and criteria of voidsBased on the analysis for cause and existing detection methods of voids beneath cement concrete pavement, the detection methods by the dynamic deflection and static deflection difference among the centre point, the midpoint of edge and the corner of the same slab, the pumping height and the road radar are studied synthetically. The evaluation criteria for the mild, moderate and serious degree of voids beneath cement concrete pavement by the indexes of the dynamic deflection and static deflection difference of the same slab and the pumping height are established. The evaluation criteria are expected to detect voids beneath cement concrete pavement in the simple, accurate and practical way, as the supplement and perfection for the related specifications.(2) Analysis of the mechanical behaviors of cement concrete slabs above voidsThe effect of factors such as the position and area of voids, the thickness of slabs, the load-transfer capacity of joints and the thickness of base on the stress and deflection of cement concrete slabs under traffic load and temperature are analyzed comprehensively. The maximum stress and deflection of cement concrete slabs are analyzed systematically, and the variation rule of the maximum stress and deflection value are summarized. The mechanical behaviors of cement concrete slabs above voids are determined, and the fatigue life is calculated, providing the mechanical basis for the detection methods. (3) Analysis of the technology and evaluation criteria for voids treatmentThe impacting and compacting technology such as of Landpac compaction, Guillotine break and MHB rubblization for voids treatment and the self-compensation grouting material of the organic type, the cement type and the sand type for different degree of voids treatment are analyzed systematically. Then the evaluation criteria are recommended to evaluate the effect of different treatment technology on different degree of voids, providing the theoretical basis for the technology and material design of voids treatment.(4) Analysis of the mechanical properties of grouting slabsAccording to the analysis of the mechanical behaviors of cement concrete slabs above voids and the treatment technology of voids grouting, the effect of factors such as the position and area of voids grouting, the modulus of grouting materials, the thickness of slabs and base on the stress and deflection of cement concrete slabs under traffic load are analyzed further. The mechanical condition of grouting slabs and the effective area of grouting material are determined.(5) Analysis of the mechanical behaviors of PCC-AC above voidsThe effect of factors such as the modulus and thickness of AC overlay and thickness of slabs on the stress and deflection of AC overlay under the coupling function of the traffic and temperature load are analyzed systematically, and the mechanical behaviors of PCC-AC above voids are studied. The evaluation criteria for the voids beneath PCC-AC by the indexes of the dynamic deflection and static deflection are recommended, providing the theoretical basis for the structural combination, material design and effect evaluation of AC overlay.