堅硬土層侵入回填土對擋土牆主動土壓力之影響

Abstract

本論文探討堅硬土層入侵回填土對擋土牆主動土壓力之影響。本研究以氣乾之渥太華砂作為回填土，回填土高0.5公尺。量測於鬆砂(Dr = 35%)狀態下作用於剛性榜土牆的側向土壓力。本研究利用國立交通大學模型擋土牆設備來探討堅硬以不同界面傾角□侵入回填土對擋土牆主動土壓力影響。為了模擬堅硬的土層界面，本研究設計並建造一片鋼製傾斜界面板，及其支撐系統。本研究共執行五種堅硬界面傾角beta= 0o、50o、60o、70o與80o五種實驗。依擋土牆砂實驗結果，本研究獲得以下幾項結論。 1.當岩石界面傾角beta= 0o時，其主動土壓力係數Ka,h 與Coulomb解相吻合，其主動合力約作用於距擋土牆底部0.33H處。 2.在岩石界面傾角45o、60o、70o與80o狀況下，側向土壓力隨深度的增加而呈非線性分布，所獲得的側向土壓力低於Jaky解，側向土壓力隨界面傾角的增加而減少。 3.當界面傾角beta為50o至80o，主動土壓力係數K,a,h數隨岩石界面傾角的增加而逐漸減小。其合力作用點的位置會稍高於理論值0.333H。 4.當傾斜岩石面入侵主動土楔時，造成擋土牆抗滑動之安全係數增加，因此根據Coulomb理論所求解之安全係數會偏向安全。 5.當傾斜岩石面入侵土楔時，使得擋土牆抗傾覆之安全係數增加，所以依據Coulomb理論所求得之安全係數會趨於安全。

In this paper, the active earth pressure on retaining walls with the intrusion of an inclination rock into backfill for loose sand is studied. The instrumented model retaining-wall facilities at National Chiao Tung University was used to investigate the active earth pressure induced by different interface inclination angles□ The loose Ottawa silica sand was used as backfill material. To simulate an inclined rock face, a steel interface plate and its supporting system were designed and constructed. Base on the test results, the following conclusions can be drawn. 1.Without the Stiff interface (beta = 0o), the active earth pressure coefficient Ka,h is in good agreement with Coulomb’s equation. The point of application h/H of the active soil thrust is located at about 0.33 H above the base of the wall. 2.For the interface inclination angle beta = 50o, 60o, 70o and 80o, the distributions of active earth pressure are not linearly with depth. on the lower part of the model wall the measured horizontal pressure is lower than Coulomb’s solution 3.For beta = 50o ~ 80o, the active earth pressure coefficient Ka,h decreases with increasing interface inclination angle. The point of application of the active total thrust move a location slight higher than h/H = 0.333. 4.For beta = 50o ~ 80o, the nearby inclined rock face would actually increase the FS against sliding of the wall. The evaluation of FS against sliding with Coulomb’s theory would be on the safe side. 5.For beta□= 50o ~ 80o, the intrusion of an inclined rock face into the active soil wedge would increase the FS against overturning of the retaining wall. The evaluation of FS against overturning with Coulomb’s theory would also be on the safe side.