條形載重於不同密度回填土上造成之靜止土壓力

Abstract

本論文探討於擋土牆後之回填土上施加均勻條形載重對作用於擋土牆靜止土壓力之影響。實驗中將氣乾渥太華砂以空中霣降法，沈積至模型土槽中，得到需要的疏鬆（Dr = 35%）、中等緊密（Dr = 60%）及緊密狀態（Dr = 80%）。利用交通大學模型擋土牆模型以實驗方法研究因地表荷重所引致的土壓力變化。為了在背填土上方施加一均勻的地表載重，本研究發展出一套地表荷重加載系統。根據實驗結果，獲得以下各項結論。 1. 以空中霣降法備置之試體，靜止土壓力分別小於由Jaky及Hendron所建議的理論值。 2. 土壤密度對側向土壓力增量的影響並不顯著。側向土壓力增量之合力□Ph和彈性解相吻合。土壤密度對 □Ph 之作用點影響並不明顯。 3. 當地表荷重距牆面水平距離0.2H以上時，側向土壓力增量之合力□Ph可以用彈性解成功的預測。 4. 當條形基礎移至靠近牆面（m < 0.2）時，將會引致超乎預期的高側向壓力。所有的理論解都低估了靠近牆頂地表荷重引致之的側向土壓力。

This paper studies lateral earth pressure due to a uniform strip loading. Dry Ottawa sand was used as backfill material. Ottawa sand was deposited by air-pluviation method into the soil bin to achieve the desired loose, medium, and dense states. The instrumented model retaining-wall at National Chiao Tung University was used to investigate the variation of earth pressure induced by surcharge loading. To apply a uniform surcharge loading on the surface of backfill, a surcharge loading system was developed. Based on the experimental work, the following conclusions are made. 1. The measured earth pressure at-rest was slightly less than that calculated with Jaky’s and Hendron’s solution. 2. The influence of soil density on □□h is not obvious. The soil thrust increment □Ph/qB in very good agreement with elastic solution. The influence of soil density on the point of application of □Ph is not obvious. 3. As the surcharge is at least 0.2H from the wall, the lateral soil thrust □Ph due to the surcharge can be successfully predicts with the elastic solution. 4. As the strip footing moves near the wall (m<0.2), the elastic theory can no longer predict the lateral pressure induced by the strip loading. The surcharge loading would induces unexpected high lateral pressure near the top of the wall. All theoretical solutions underestimated the horizontal pressure due to the stress concentration at the edge of the footing.