Horizontal Pressures on an Unyielding Wall Due to Strip Loading on Compacted Backfill
Dr. Yung-Show Fang
|關鍵字:||側向土壓力;條形載重;夯實回填土;靜止擋土牆;Horizontal Pressures;Strip Loading;Compacted Backfill;Non-yielding Wall|
2. 當地表載重施加於靠近檔土牆面（m≦0.1），會降低作用於靜止擋土牆之土壓力。這可能是由於夯實載重造成靠近地表土體之側向壓縮，趨近被動狀態。靠近牆面之地表荷重造成土體之軸向壓縮，同時引致側向伸張變形，改變夯實土之被動狀態而趨於較不被動的狀態(less passive)，因而降低側向土壓力及側向合力□Ph。這個現象會隨著地表加載位置遠離擋土牆面而消失。
Dry Ottawa sand was used as backfill material. The horizontal pressure acting on a non-yielding wall due to a strip loading is studied in this paper. The Ottawa sand was placed and compacted the soil bin to achieve the required relative density of 75%. A surcharge loading system was developed at National Chiao Tung University to apply a 0.1m-wide strip surcharge of compacted backfill. The centerline of footing was applied at 0.15 m, 0.30 m, 0.60 m, and 0.9 m from the surface of the wall. Experiments were conducted to determine the ultimate bearing capacity qult of the compacted backfill. From a practical point of view, the intensity of the surcharge applied is controlled to less than qult/3. Based on the experimental results, the following conclusions are made. 1. To provide a uniform normal stress on the footing, the use of an air cushion sandwiched between the lid and steel footing appears to be a practical method. 1. If the surcharge is near the face of the wall (m ≦ 0.1), the surcharge loading will induced a decrease of lateral pressure in the upper part of the compacted backfill. It may be deduced that the surcharge applied on the top of the soil element near the wall (m = 0.1) will compress the soil element vertically. The induced lateral deformation will make the compacted soil “less passive” and the lateral soil thrust □Ph to decrease. This phenomenon would disappear as the surcharge loading move away from the wall. 2. The experimental lateral soil thrust induced by surcharge loading ΔPh is apparently smaller than the theoretical predictions for all surcharge loading positions. All theoretical estimations provide a safe but uneconomical design for the horizontal pressure increasing due to surcharge on the compacted backfill.