題目題目 REINFORCEMENT EFFECT EVALUATION FOR THE GEOSYNTHETICE CLAY BANKING NAGASAKI UNIVERSITY K. TSUJI Y.TANABASHI Y.JIANG

Technology. Background of study ① Development of urban and underground space Security of the right spot is the difficult Increase of the cost Low quality soft clay from construction Society ＆ environment Geosynetics reinforcement The reuse of low quality soil is promoted.

Background of study ②  Drainage capability  Tension strength Development of geocomposite. The geocomposite is feasible and more economic. The design of geocomposite is in a study phase. +

Purpose of the study. Kanto loam (The low quality soil) The steep slope is assumed. ・ Change of the consolidation of the every layer of the banking. ・ Reinforcement function of geoconposite. The reinforcement effect of geocomposite is evaluated by finite difference analysis. Behavior prediction Suggestion for the design of geocomposite reinforced embankment

Analysis method and outline. The difference between the construction period.  Friction angle of GC-soil.  Strength constant of the soil. Mohr-Coulomb model  The membrane element is selected to simulate. The behavior of the banking was evaluated. Set at each layer.

Analysis case. The difference between construction period and drainage distance by the laying interval.  Strength constant of the soil.  Friction angle of GC-soil Height of the banking. (m) Reinforcement laying space. (cm) Non-reinforced. (N),45(GC45),90(GC90) Slope gradient 1:0.6 Construction period. 240,480,720480,720720,960

The physical property in analysis. Physical properti values of banking material (Kanto lome ) ItemParameter Volumetric elastic coefficient bulk modulus K(kPa) 500 Cohesion c (kPa) 19.6 Density ρ (g/cm 3 ) Angel of internal friction φ cu (deg) Expression (1) Dilatancy angular ψ(deg) 0 Limit of tensile stress σ’ (kPa) 1.96 Physical properties value of geocomposite Cohesion of interface (kPa) 4.41 Angel of internal friction of interface φ cus (deg) Expression (2) Rotation of elastic modulus (kPa) Calculated from direct shear test.

Result of direct shear test. Choesion ： It is almost constant regardless of the progress of the consolidation. Angle of internal friction ： After the primary consolidation end, it approaches in the constant value. （1）（1） （2）（2） Kanto lome The friction angle of GC- soil interface Choesion ： It is almost constant regardless of the progress of the consolidation. Angle of internal friction ： After the primary consolidation end, it approaches in the constant value. GC-soil interface ： kanto lome ： The friction angle of Consolidation time (min) c cus = 4.41 (kPa) c cu =19.6 (kPa)

Banking consolidation period Introduction of banking consolidation period. From layer ①, the subsequent layers were heaped step by step, and actual consolidation period for every layer was calculated. ⑤ ④ ② ③ ① ⑥ 〔 Reference literature. 〕 Y.Tnahashi and H.Nagashima (2002): Geocomposite design method tentative plan. In this study Different consolidation coefficient and consolidation period were set at every 90cm/layer Determination of the physical property.

Consideration of construction period. The consolidation period for each layer is assumed to be the same, as illustrated The construction process. Erea Construction period ① ② ③ ④ ⑤ ⑥ （m）（m） Time Banking height

The analytical model A footing loading is loaded at every 5-10 kPa step to the crown surface of the embankment ： The membrane element Crown width B=2H H (m) Banking height

Loading –settlement curve (8m) GC90_30day GC90_10day Displaced linearly. The control of settlement. GC45_10day GC45_30day Strength of load (kPa) Settlement (m) Increases with the consolidation degree N_10day N_30day A limit in the strengthning

Loading –settlement curve (12m) The rapid settlement. 12m seem to be the limit N_20 日 N_30 日 Displaced linearly The control of settlement. GC90_20day GC90_30 日 day GC45_20day GC45_30day The effect of consolidation period is not remarkable Settlement (m) Strength of load (kPa)

Limit of embankment height Banking height (m) Evaluation of limit of banking height. Safety factor A height of 11.3m The limit of embankment height is 14.4 ｍ

The crown settlements of different height cases with GC45cm H=16m_GC45_40 day H=12m_GC45_30 day H=8m_GC45_30 day Strength of load (kPa) Settlement (m) The difference between the settlement. The settlement of the higher embankment is large

Load strength-deformation slope (8m) 100 ｃｍ The embankment collapses A large deformation occurred under a surface load of 50kPa N_50kPa The embankment is stable. GC90_50kPa No large deformation GC45_50kPa Initial slope

Load strength-deformation slope (12m) 100 ｃｍ Deformation is restrained Deformation strength is small GC90_50kPa GC45_50kPa Initial slope

Shear failure region (N) Load strength Destruction ： 10kPa 20kPa 30kPa 40kPa50kPa 55kPa The embankment collapses The destruction area develops. 8m Case N

10kPa Load strength Displacement vector(N) 20kPa 30kPa 40kPa 10kPa 50kPa 55kPa The displacement is large. The destruction area Case N 8m

Displacement vector ( GC45cm) 10kPa 20kPa 40kPa60kPa Load strength Displacement control. Case GC45 The embankment is stable. 8m

Shear failure region ( GC45cm) Load strength 10kPa 20kPa 40kPa 60kPa 80kPa 8m No progress of breakdown region to banking upper part. ： ケース GC45 The embankment is stable. Destruction

Tensile stress the reinforcement material The effect of the stress concentration on the toe slope. Distance from slope (m) Geocomposite tensile stress (kPa) The stress is also concentrating each GC near 4 ～ 6m from the slope The displacement control by the reinforcement maternal. Tensile stress of the reinforcement material The dispersion of the stress. Geocomposite tensile stress (kPa) Distance from slope (m) The embankment is stable.

Conclusion  Loading –settlement curve,Deformation of slope & Displacement vector. The strengthening by consolidation. The effect of restraining the displacement of the slope.  Considering the construction period.  Tensile stress of the reinforcement material Design of geocomposite reinforced embankment.

圧密時間の算出 検証実験結果 応力履歴がある最終段階の圧密沈下経 路 ：ある層の排水距 離 ：供試体の排水距 離 ：実験における時 間 ：実地盤における時 間 テルツァギの二乗 則 応力履歴のない圧密沈下経路 ＝ ほぼ同一

換算圧密時間の算出 実際の圧密経路 P n ～ P n+3 ：圧密圧 力 （盛土の自 重） ①②③④ 層番号 ① ③ ② ④ 様々な応力履歴を唯一の応力履歴に変換 t * n+1 ～ t * n+3 ：換算圧密時 間

n 層目盛土の換算圧密時間 圧密時間の算出 (2) 時間係数 T V ≧ 0.5 の時 (1) 時間係数 T V <0.5 の時 テルツァギの圧密理論を基 本 各層について施工期間 毎に算出 解析物性値 の決定 沈下経路の傾き

メンブレン要素 接点ごとの引張応力を算出