柔性及剛性載重對靜止擋土牆造成之側向土壓力

Abstract

本論文探討於靜止擋土牆後方之回填土上施加柔性及剛性條形地表荷重所造成之水平土壓力之影響。在實驗中將氣乾渥太華砂以空中霣降法，沈積至模型土槽中形成疏鬆回填土( )。本研究自行研發之地表荷重加載系統，以1.45 公尺長, 0.1公尺寬之柔性及剛性條形載重作用於回填土表面。條形載重之中心線分別距離擋土牆面0.15公尺、0.3公尺、及0.6公尺。根據實驗結果，獲得以下各項結論。

1.當施加之地表載重靠近擋土牆面，將會在牆面上方引致超乎預期的高側向壓力。這可能是由於基礎下方應力集中現象，造成牆面上方側向土壓增量隨著地表加載位置接近擋土牆面而增大。 2.土壓合力的作用位置將會高於或等於Method of Image建議的位置。DM-7.2設計手冊建議的公式會低估側向合力的作用高程。 3.當施加之地表載重靠近擋土牆面（m = 0.1 或 m = 0.2），Terzaghi所建議的計算公式明顯低估地表載重所引致的側向合力。 4.柔性與剛性條型地表載重所造成之側向土壓力合力增量及增量作用位置相類似。

This paper studies lateral earth pressure on an unyielding wall due to flexible and rigid surcharge strip loadings. Dry Ottawa sand is used as backfill material. The instrumented model retaining-wall at National Chiao Tung University is used to investigate the horizontal earth pressure induced by flexible and rigid surcharge loading. The centerline of footing are applied at 0.15 m, 0.30 m, and 0.60 m from the surface of the wall. Based on the experimental work, the following conclusions are made. 1.As the strip loading approaches the wall, the stress concentration zone under the footing moves closer to the unyielding wall, causing the Dsh acting near the top of the wall to increase. 2.The experimental R/H values are equal to or greater than the R/H values calculated with the method of image. The DM-7.2 method underestimates the point of application of the induced horizontal pressure increment. 3.Terzaghi (1954) suggested that for a value of m less than 0.4, the pressure on the wall due to the line load should be determined as m = 0.4. Test results indicate that Terzaghi’s suggestion fails to predict the horizontal pressure increase due to a strip surcharge loading. 4.The test results of DPh and R/H due to the application of flexible and rigid footings are quite similar.