Kazuyuki Kubo

Study on the Recycling Method for Drainage Asphalt Pavement and Evaluation for its Durability

In Japan, drainage asphalt pavement (DAP) is widely used especially on the highway and the express way. However, because of the existing porous asphalt materials consist of DAP use polymer modified bitumen, and the aggregate gradation of DAP is differ from conventional mixture, it is difficult to use those porous asphalt materials as the recycled aggregate for reclaimed asphalt pavement. Therefore, the recycling method for recycled DAP which were consisted of recycled porous asphalt materials and virgin aggregates has not been established yet. This paper describes that the recycling method for recycled DAP was considered, and the workability and five years durability was also verified by trial construction of the recycle DAP and new DAP which were consisted of virgin aggregate on the national highway.

Thermal Stress Calculation Method for Concrete Pavement Based on Temperature Prediction and Finite Element Method Analysis

A method to predict thermal stress of a concrete slab was developed in this study. In this method, temperatures and thermal stresses in a concrete slab are predicted by solving a one-dimensional heat transfer equation with the control volume method and three-dimensional finite element method (3DFEM). Predicted temperatures were compared with those measured in various regions in Japan to validate the method. The thermal strains calculated with 3DFEM were also compared with those measured in test concrete pavement slabs to confirm the method’s validity. The relative frequencies of thermal stress for one year were obtained from the calculated stresses. In thin slabs (20 and 23 cm), tensile thermal stress at the bottom was greater than those estimated with the current thermal stress equation, which considers internal stress due to the nonlinearity of the temperature profile in the slab. In thick slabs (25 and 30 cm), by contrast, the current thermal stress equation gave almost the same thermal stress as the finite element method did, although the peak time for the maximum tensile stress was delayed in the thick slabs. The proposed method can be applied to a variety of concrete pavement structures under various temperature conditions.

Evaluation method of pavement surface characteristics for rolling resistance

Pavement technology intended to reduce tyre-pavement rolling resistance is a new technology for establishing the future low-carbon society. Reduction of rolling resistance leads to reduce vehicle CO2 emission and to improve fuel efficiency. However, the relation between rolling resistance and pavement surface characteristics is complex and there are some issues to be solved including clarifying the evaluation methods. The evaluation method for rolling resistance generally involves measuring the rolling resistance coefficient directly; however this direct measurement requires special measurement devices. Indirect evaluation methods will make measurements easier and help put low-rolling resistance pavement technologies to practical use. This paper reports the results on determining the contact pressure distribution between tyre and pavement surfaces using a pressure measurement film to evaluate the rolling resistance indirectly. The results of analyses the relations between the rolling resistance and pavement surface characteristics, it were revealed that the contour map of contact pressure distribution were fully different depending on the pavement surface texture and it would be useful to evaluate the negative texture that lead to the low-rolling resistance pavement surface.

Theoretical Solution Based on Volumetric Strain of Elastic Multi Layered Structures under Axisymmetrically Distributed Load

The analysis software for elastic multilayered structure is essential for theoretical design and structural evaluation of pavement. In general load applied at multilayered system is assumed to be uniform. In addition to the uniform loading, parabolic distribution and inverse parabolic distribution are also considered in this study. Instead of stress function or displacement function, which is obscure in physical meaning but is often used in solution development, the stress and strain responses are obtained in terms of a volumetric strain. After Hankel transforms are applied to the responses and integral constants are determined by using boundary conditions, the inverse Hankel transforms are employed to recover all responses. Verification of solutions is confirmed by comparing the responses with the results from BISAR and GAMES when uniform load is applied. In case of nonuniform loading, verification is made by confirming that the applied distributed load coincides with computed vertical stress at the surface.

Confidence Interval of Pavement Layer Parameters Estimated from FWD Time Series Data

A falling weight deflectometer (FWD) is a well recognized tool for evaluating the structural capacity of road and airfield pavements. Because a FWD test is dynamic, a dynamic backcalculation program called Wave BALM is used in this paper. The dynamic backcalculation utilizes the time history data of load and deflections measured by FWD. Pavement is assumed as a multilayered system composed of viscoelastic layers. The dynamic backcalculation program can estimate pavement layer moduli and the corresponding damping coefficients by point-wise matching technique coupled with the Gauss Newton method. Because the number of unknowns for dynamic backcalculation is twice as many as static backcalculation, the iterative process tends to be more unstable. Thus backcalculated results are expected to be greatly affected by seed values. Fifty sets of seed values are generated within the assigned ranges by Monte Carlo method, and backcalculation is performed. The means and the confidence intervals of layer modulus, layer damping coefficient, and dynamic modulus are computed.

CONSIDERATION OF EXTENT OF RESILIENT MODULUS OF BITUMINOUS MIXTURES

In this research, the authors confirm maximum and minimum of resilient modulus of bituminous mixtures with various binder and aggregate when a repeated loading time is 0.1s. About mix portion, there is no difference between dense-graded asphalt mixture, course-graded asphalt and asphalt stabilization in average. About binder, resilient modulus of bituminous mixtures with modified asphalt mixture is bigger than that with straight asphalt in about 10 degrees centigrade. And resilient modulus of bituminous mixtures is influenced by aggregate and binder company in about 10 degrees centigrade. 本研究では，舗装設計便覧に掲載されている，アスファルト混合物の弾性係数の一般的な範囲について確認することを目的とした．文献調査によりレジリエントモデュラスの値を確認し，載荷時間が0.1秒の場合は便覧に掲載されている範囲内に収まっていることを確認した．配合別の比較では，密粒度，粗粒度，アスファルト安定処理では差がほとんど見られなかった．バインダー別の比較では，ポリマー改質アスファルトII型はストレートアスファルトよりも温度上昇に伴うレジリエントモデュラスの低下が抑制されることを確認した．次に，骨材とバインダーメーカーの違いがレジリエントモデュラスに与える影響の有無について確認した．その結果，10℃程度の低い温度の場合，影響が見られることがわかった．

A STUDY ON REPAIR TARGET OF EVENESS AND BUMP HEIGHTS FOR SIDEWALK PAVEMENT

In Japan, the peoples concerns to comfortable sidewalk are becoming higher year by year. Therefore the sidewalk pavement that is considered of comfortable and scenery are developed a lot. The objectives of this study are to identify the required function of sidewalk pavement and to propose its repair target of the evenness and the bump heights. Therefore, the questionnaire was done by the road administrators about functions and management factors these are considered as important. And also the questionnaire that was answered by ordinary person (younger and elder) and wheel chair users, baby carriage users by walking on some kind of sidewalk pavement were done. As the results, the road administrator considered the bump and evenness as important factor to manage the sidewalk pavement. And the drafts of repair target for elderly person, wheel-chair user and baby carriage user and for ordinary person were proposed. 近年，歩きやすい歩道に対する意識が高くなってきており，歩行者系舗装においても歩きやすさや景観性等を重視した舗装が多種開発されている．本研究は，歩行者系舗装の利用主体別の路面要求性状を明らかにすること，路面の平たん性・段差の補修目標に関する提案等を行うことを目的とした．そこで，道路管理者に歩行者系舗装に求める性能および管理項目についてアンケート調査を行うとともに，健常者（60歳未満および60歳以上），車椅子，ベビーカーを被験者として，多様な路面を歩行することによる体感評価等を行った．その結果，歩行者系舗装の性能評価項目として，段差および平たん性が重要であることが分かった．また，健常者（60歳以上），車椅子，ベビーカーと健常者（60歳未満）を含めた路面補修の目標値を提案することができた．