受限緊砂回填土對擋土牆主動土壓力之影響

Abstract

本論文以試驗方法探討作用於垂直剛性擋土牆的側向土壓力，此擋土牆逐漸遠離受限之緊砂回填土。模型擋土牆設備試驗以渥太華砂為回填土材料，回填土高0.5公尺，岩石介面與水平線夾角β為0°，60°，70°，80°和90°。本研究使用震動夯實法製做緊砂回填土，以一座鋼製傾斜界面板模擬束制背填土的岩石介面。試驗結果顯示，震動夯實造成的額外水平應力隨擋土牆主動位移而消散。隨著逐漸減小的水平距離b，和逐漸增大的介面板傾斜角度β，介面板逐漸侵入主動土楔，造成位於接近擋土牆底部的側向土壓力減少。於不同的b與β值，試驗獲得的主動土壓合力比Coulomb解大25.1%至比Coulomb解小24.2%。主動土壓合力作用點位置隨β角的增加而上升。於不同的b與β值，試驗得到的主動土壓合力作用點(h/H)a值分布為0.475至0.333。 無因次化的主動土壓力矩介於0.0801至0.0599之間，大於Coulomb主動土壓力矩33.5%至0%。鄰近傾斜岩石介面的存在略為降低檔土牆抗傾倒之安全係數，依據Coulomb主動土壓力理論預估求出之抗傾倒安全係數將不安全。

This paper presents the experimental data of lateral earth pressure acting on a vertical rigid wall, which moved away from a limited backfill of dry sand. A model retaining-wall facility was used and dense Ottawa sand was used as backfill material. The thickness of backfill was 500 mm and rock face inclination angles of 0, 60, 70, 80 and 90 degrees were investigated. The dense backfill was prepared by vibratory compaction method. To simulate an inclined rock face, a steel interface plate was used. Test results showed that the extra lateral earth pressure due to vibratory compaction dissipated with the active wall movement. As the interface angle β increased or spacing b decreased, the inclined rock face intruded the active soil wedge, the earth pressure decreased near the base of the wall. The experimental active soil thrust for different b and β varied from 25.1% greater to 24.2% less than Coulomb’s solution. The point of application of the active soil thrust ascended with increasing □ angle. For tests with different b and β, the experimental (h/H)a varied from 0.475 to 0.333. The experimental normalized driving moment varied from 0.0801 to 0.0599, which was about 33.5% to 0% greater than Coulomb’s theoretical solution. The existence of a nearby inclined rock face would slightly decrease the factor of safety against overturning. The estimation of the factor of safety against overturning with Coulomb’s theory would be unsafe.