Katsuhiko Arai

Dynamic and Static Combination Analysis Method of Slope Stability Analysis during Earthquake

The results of laboratory model tests for simulating the slope failure due to vibration, including unreinforced slope and the slope reinforced by using geotextile, show that the slope failure occurs when a cumulative plastic displacement exceeds a certain critical value. To overcome the defects of conventional stability analysis, which evaluates the slope characteristics only by its strength parameters, a numerical procedure considering the stiffness and deformation of materials and geosynthetics is proposed to evaluate the seismic slope stability. In the proposed procedure, the failure of slope is defined when the cumulative plastic displacement calculated by a dynamic response analysis using actual seismic wave exceeds the critical value of displacement estimated by a static stability analysis considering seismic coefficient. The proposed procedure is applied to the laboratory model tests and an actual failure of slope in earthquake. The case study shows the possibility that the proposed procedure gives the realistic evaluation of seismic slope stability.

Analysis of Long-Term Deformation of Reinforced Retaining Wall Using Optical Fiber Sensor Geotextile

Geotextile have been widely used in the reinforced retaining wall, but it is not easy to measure the deformation of the wall during and after construction. To assess the deformation stability of the reinforced retaining wall, an optical fiber sensor was used in geotextile. Based on the measurement accuracy of strain for the sensor geotextile, an actual geotextile-reinforced retaining wall was studied using the fiber sensor geotextile. The experimental results were compared with the results from a numerical procedure, which employs the Mohr-Coulomb yield criterion and an initial stress method and determines the plastic displacement at collapse represented by the distribution of yield elements. The comparison shows that the numerical results have a good agreement with the corresponding measurement values. The result shows the possibility that the procedure gives the realistic evaluation of long-term deformation of reinforced retaining wall.

Quality Control Index for Recycled Paraffin Used as a Modifier Agent in Asphalt

電線被覆などに使用された架橋ポリエチレンの廃材を熱分解することにより，再生パラフィンが得られる。再生パラフィンを道路舗装に使用するアスファルトに添加することにより，舗装表面のわだち掘れ (車両走行の繰返し荷重による道路の凹み) 軽減などの大きな改良効果がある。材料となる架橋ポリエチレンの種類や再生方法によって再生パラフィンの物性が異なるため，再生パラフィンを添加したアスファルト (改質アスファルト) の物性もその影響を受けるので，再生パラフィンの品質管理が重要になる。わだち掘れ対策の改質アスファルト混合物 (アスファルトと骨材を混合した舗装材料) は耐流動性が要求され，耐流動性は動的安定度試験で評価される。動的安定度試験は多大の時間と費用を要するので，改質剤としての再生パラフィンの広範な普及には，再生パラフィンの品質を評価するための，改質アスファルト混合物の耐流動性への影響を評価する簡便な評価指標が必要である。本論文では，種々の試験項目と動的安定度との相関を多数の実験で検討し，計測が容易で信頼性の高い耐流動性の評価指標を得ることを試みた。その結果，改質アスファルトの針入度と軟化点を評価することで，材料の架橋ポリエチレンの種類が既知の場合に，再生パラフィンの品質管理が可能であることを示した。再生パラフィンの材料が未知の場合には，上述の品質管理方法を適用できないので，再生パラフィンの圧裂強度と粘度の2つの物性と，改質アスファルト混合物の動的安定度の関係を示し，未知の材料から製造される再生パラフィンの圧裂強度と粘度を求めることで，改質アスファルトに使用可能な材料かどうかを判定する方法を示した。

A Test Construction of Vertical Retaining Wall Reinforced with Geogrid

The authors carried out a large scale of test embankment where a vertical retaining wall of concrete blocks was used and the backfill was reinforced with geogrid. The height of retaining wall is 5m. This paper reports the results of monitoring the lateral displacements of the retaining wall, strains produced on the geogrid, and so on.Without any trouble, 40 days have passed since the embankment was completed. At the present stage, the lateral displacement of retaining wall measured is about 10cm (including the displacement during construction) at the very outside and the strain on geogrid is about 1%. These results show that our construction method proposed can be successfully applied to actual structures.