长短桩复合地基中的土拱效应及分析

Analysis of soil arching of composite foundations with long and short piles

路堤填土在桩与桩间土间发生了不等的沉降变形,导致路堤土拱效应的产生。土压力的测试结果表明,填土荷载在向管桩桩帽与搅拌桩桩顶集中,桩帽平台上的平均土压力是桩间土土压力均值的4.5倍,搅拌桩顶的是桩间土土压力均值的1.7倍。桩帽平台上承担的土重为总承担荷载的25%,而桩间土承担的占69%,搅拌桩承担的仅占6%。桩与桩间土的承载能力都未充分发挥,管桩承担的荷载仅是其能力的40%,桩间土的承载能力也只发挥25%,尚有潜力可挖。置换率是桩体承担荷载比例大小的主要因素,提高桩体承载比例的主要途径是提高桩的置换率,增大桩帽面积。

Unequal settlements between the piles and the soil will result in soil arching of embankments.Pressure test results（or monitoring in situ） show that the fill load concentrates toward the pipe pile cap and the mixed piles,the earth pressure on the pile cap platform is 4.5 times the average one on the soil-area between piles,and that on the mixed pile top is 1.7 times that on the soil-area between piles.The pile cap platform,the soil-area between piles and the mixed piles share 25%,69% and 6% of the total fill load.The bearing capacity of the piles and the soil-area between piles do not give full play,that is,the bearing load on the pipe piles is only 40 % of their capacity,and the soil-area between piles is only 25 %,indicating that there is still potential to be tapped.The replacement ratio is the main factor for the increase of proportion of pile bearing load,and the main way is to raise the replacement ratio of piles and the size of the pile cap.