不同型式主動牆位移引致之土壓力

Abstract

本論文探討不同形式主動牆位移引致之土壓力變化情形。本研究利用國立交通大學模型擋土牆進行各項試驗。試驗結果經過分析整理之後得到下列各項結論: 1. 牆為平移狀態(T mode)而言: 在回填土內部不同深度所得之土壓力，會隨著牆移動量的增加而降低。而後，逐漸趨於一定值。Coulomb主動土壓力理論對於主動土壓力係數Ka,h具有相當準確的估算。 2. 牆體繞著牆頂旋轉狀況(RT mode)而言: 隨著牆位移的增加，上半部土壓力會出現增加的趨勢，當位移量達到0.001之後，土壓力才有明顯下降的情狀。由試驗所得之主動土壓力係數Ka,h高於由Coulomb主動土壓力理論所估算之結果，合力作用點會隨著牆位移量的增加逐漸上升至牆抵大約0.47 H ~ 0.50 H 的位置 (H = 牆高)。 3. 牆體繞著牆底旋轉狀況(RB mode)而言: 牆底沒有足夠的位移讓土體達到完全主動狀態，會出現土壓力較高的情況，由實驗所得之主動土壓力係數Ka,h高於Coulomb主動土壓力理論所估算之結果，而合力作用點會隨牆位移的增加而下降至牆抵大約0.27 H ~ 0.30 H 的位置。 4. 隨著n值的增加，不論是上述任何一種旋轉模式，其土壤的行為將會收斂至牆平移的行為之下。

This study investigates the lateral earth pressure due to various active wall movement. In order to study the lateral earth pressure under various wall movement modes, a unique model retaining wall was constructed in the National Chiao Tung University. The model wall is capable of making both translational and rotational movements. Based on this study, the following conclusions can be drawn. Experimental results indicated that, for a wall under translation movement, the earth pressure distribution remained approximately a linear distribution with the active wall movement. The point of application of the resultant thrust is located at about H/3 above the wall base. For a wall under RTT Mode (n = 0.01), the earth pressure measured at the lower portion decreases rapidly with the active wall movement. On the other hand, the soil pressures of upper portion behind the wall increase initially with increases wall movement. The experimental active earth pressure coefficient is obviously higher than that obtained from the Coulomb’s active earth pressure theory. The points of application of active thrust were located at about 0.49H ~ 0.50H above the wall base. For a wall under RBT Mode (n = 0.01), the backfill near the top of wall yield rapidly with the wall displacement, the soils near the base of wall was not enough displacement to reach the active state. As the result, earth pressure coefficient, Kh is obviously higher than that obtained from the Coulomb’s active earth pressure theories. However, as n increases to a large number, the behavior of backfill would converge to that due to a wall under translational movement.