Analysis of Pavement Inter-layer Failure and Research of a New Cement Concrete Pavement Structure with Separation Layer
|Keywords||Cement Concrete Pavement Theoretical Model Pavement Slab Base Course Separation Membrane|
Cement concrete pavement constitutes one of the main pavement structures for both highway and urban road.Aiming at the frequent occurrence of cement concrete pavement failure, the authors have for the first time raised queries about the three idealized prerequisites for the related traditional theoretical model of cement concrete pavement and carried out research.Theoretically, the existence of the transition layer between the slab and base is discovered and the three basic inter-layer failure types are firstly exposed with related mechnisms clarified in the paper. In detail, the drastic differences between the real slab-base condition and the ideal pavement boundary state caused by the three basic inter-layer failure types are analyzed, the grave influence of the transition layer upon the pavement failure revealed, and the intrinsic relation between the transition layer and the three basic inter-layer failure types expounded. Research work of the paper indicates that, the existence of the transition layer and the consequential occurrence of the three basic inter-layer failure types will inevitably invalidate the ideal smooth contact between the pavement slab and the base, deprive the base course of its initial integrity, bring forward damages around the separation interface between the slab and base, and make sharp inconsistency between the real slab-base condition and the three idealized prerequisites behind the classical pavement model.In field investigation, the three basic inter-layer failure types exist widely in pavement slabs, the evolution of which brings about harmful debris layer and dangerous cantilever slab. These facts confirm a sharp inconsistency between the field inter-layer situations and the three idealized prerequisites, which accounts for the continuous aggravation of the slab-base condition, and in turn proves that the ideal inter-layer situations can hardly be realized in the case of pavement slabs directly cast on base course.Lab experiments indicate that, carrying capacity of the pavement slab directly cast on the base, after the slab-base separation occurs upon destruction of the initial inter-layer bonding, is by times lower than that of the pavement slab kept in initial close smooth contact with the base course. The results prove that the inter-layer situation, which imposes crucial influences on the pavement carrying capacity, should be treated with care in theoretic pavement modelling as well as practical pavement construction.To eliminate the sharp inconsistency between the real slab-base condition and the three idealized prerequisites behind the classical pavement model, a new pavement structure with a separation layer between the slab and base is put forward in the paper. Theoretical analyses, experimental verifications and application evidences indicate that a waterproof separation membrane can eliminate the three basic inter-layer failure types as well as the transition layer and help the actual pavement condition satisfy the three idealized prerequisites.Long-term comparisons between the ordinary pavement and that with waterproof separation membrane prove that the membrane, by keeping the in-service slab-base contact in an ideal state required by the three idealized prerequisites, can sustantially guarantee the carrying capacity of the cement concrete pavement and effectively prevent it from failing ahead of schedule.Therefore, this paper makes a self-consistent logic loop of 7 links: query raising, theoretical analysis, field investigation, experimental verification, trial solution, application proof and query settlement. Should any single link lack tenability, the loop would break and the argumentation of the paper fail.Fortunately, the queries get settled in the end. If the cement concrete pavement is directly cast onto the stabilized base course as usual, the sharp inconsistency between the ideal pavement model and its actual situation is bound to emerge, and the pavement performance obtained is far below expectation. If the cement concrete pavement is cast with underlying waterproof separation membrane, the pavement performance attained comes desirably, and the sharp inconsistency existing between the actual pavement situation and the ideal pavement model is thus eliminated.