鄰近岩石界面傾角對靜止土壓力之影響

Abstract

本論文探討鄰近岩石界面傾角對靜止土壓力之影響。 在實驗中，本研究以氣乾之渥太華砂作為回填土，回填土高1.5公尺。量測於鬆砂(Dr = 35%)與緊砂(Dr = 72%)狀態下的側向土壓力值。本研究利用國立交通大學模型擋土牆設備來探討不同岩石界面傾角α與擋土牆間對側向土壓力造成的影響。為了模擬堅硬的岩石界面，本研究設計並建造一塊表面鋪上防滑材料的傾斜界面板，以及其支撐系統。本研究共包含岩石界面傾角α= 0o、45o、60o、70o與80o五種實驗。依據鬆砂實驗結果，獲得以下幾項結論。 1. 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。 2. 當岩石界面傾角α=0o時，側向土壓力稍微低於Jaky解，其合力約作用於距擋土牆底部0.33H處。當岩石界面傾斜α角增加，其側向土壓力係數Ko隨之減少，然而合力作用點則隨α角之增加而向上提升。 3. 側向土壓力係數Ko,h與岩石界面傾斜間α可建立一關係式為 Ko,h,α = Ko,h,Jaky – 0.00462 × α，其中α值適用於岩石界面傾角介於0o至80o間。 依據夯實緊砂的試驗結果，獲得以下幾項結論。 1. 當岩石界面傾角α=0o時，於上側牆面測得之側向土壓力值趨近於Rankine被動土壓力。在夯實影響區以下的側向土壓力分布與Jaky靜止土壓力低於Jaky土壓力，且此區域之σh隨著岩石界面傾角α的增加而逐漸減小。 2. 側向土壓力係數隨岩石界面傾角的增加而逐漸減小。合力作用點的位置會隨著岩石界面角α的增加而上升。

This paper studies the effects of adjacent inclined rock face on earth pressure at-rest. Dry Ottawa sand was used as backfill material. Horizontal earth pressures in loose (Dr = 35%) and compacted (Dr = 72%) soil mass were measured. The height of backfill is 1.5 m. The instrumented model retaining-wall at National Chiao Tung University was used to investigate the lateral earth pressure at different rock face inclination angles α. To simulate an inclined hard rock face, an interface plate covered with Safety-Walk (anti-slip material) and its supporting system were designed and constructed. The interface inclination anglesα= 0o, 45o, 60o, 70o, and 80o. Base on the test results for loose sand, the following conclusions can be drawn. 1. The distributions of lateral earth pressure are not linearly with depth for the interface inclined atα= 0o, 45o, 60o, 700 and 80o. The measured horizontal pressureσh is lower than Jaky’s solution, andσh decreased with increasingαangle. 2. Without the interface plate (α= 0o), the coefficient Ko,h is slightly less than Jaky solution. The point of application h/H of the at-rest earth pressure is located at about 0.33 H above the base of the wall. The coefficient Ko,h decreases with the increase of the rock face inclination. The total soil thrust rises to higher locations with increasing interface inclination angleα. 3. An empirical relationship between the coefficient Ko,h and the interface inclination angleα can be established: . This equation is applicable for loose sand for . Base on the test results for dense sand, the following conclusions can be drawn. 1. After compaction, the lateral stress measured near the top of backfill is almost identical to passive earth pressure. Below the compaction-influenced zone forα = 0o, the lateral stresses converge to the earth pressure at-rest based on Jaky’s equation. 2. The coefficient Ko,h decreases with the increasing of the rock face inclination. The point of application h/H of the total thrust rises to a higher location with increasing interface angle.