DDC法复合黄土地基的原位浸水试验研究  

In-situ soaking test on composite loess foundation with down-hole dynamic compaction( DDC)

作　　者：孔洋[1,2] 阮怀宁[1,2] 黄雪峰[3,4] 

机构地区：[1]河海大学岩土力学与堤坝工程教育部重点实验室,江苏南京210098 [2]河海大学江苏省岩土工程技术工程研究中心,江苏南京210098 [3]兰州理工大学,甘肃兰州730050 [4]解放军后勤工程学院,重庆401331

出　　处：《土木工程学报》2017年第11期125-132,共8页China Civil Engineering Journal

基　　金：国家自然科学基金(51379065;51579081);中央高校基本科研业务费专项资金(2016B43414)

摘　　要：针对黄土地区浸水载荷试验研究较少,在湿陷土层厚度为36.5m的兰州和平镇马兰黄土场地进行了持续时间为137d的DDC法复合地基的原位浸水试验研究,涵盖平整后场地的原位增湿、不同工况DDC桩处理地基及布设承台加荷浸水等阶段。试验结果表明:(1)桩长恒定,三桩间平均挤密系数λac随桩间距L的变化曲线可由Holliday公式表示。(2)承台总沉降量时变曲线呈现明显的"台阶"状,其陡增状态与水分的向下入渗引起桩侧及底部土体发生多次湿陷有关。(3)承台总沉降量时变曲线主要包括四个阶段,即陡增阶段、平稳阶段、缓增阶段与趋于稳定阶段;各阶段的拐点,可作为水分竖向运移规律研究的特征点位;各阶段沉降量增长形式差异与剩余湿陷量的发生方式有关。(4)承台周围地表隆起现象显著于地表沉降,可由地表隆起量的突变点位置及时间研究水分的水平运移规律。(5)DDC工法桩的建议合理间距为1.1m,桩长为20m。Due to the fact that less research is focused on the soaking load test in loess area, a 137-day large-scale insitu soaking test on the composite foundation treated by the down-hole dynamic compaction （DDC） method was carried out in loess area with 36.5m collapsible thickness in Peace Town, Lanzhou City. Several essential testing stages, such as ground humidification on leveled foundation, foundation treatment by the DDC method under different working conditions and field soaking below the cap were carried out in the test. Given the constant pile length, the relation of average compacting coefficient λac and pile spacing L of points between three piles can be represented by the Holliday formula. The time-varying curve of total settlement of concrete tap shows a clear ＂stair＂ shape, and the sharply increasing state is related to several collapses of the loess around and under the pile caused by water infiltration. The time-varying curve of total settlement for the concrete tap can be divided into 4 parts, i. e. , the rapidly increasing stage, the constant stage, the gradually increasing stage and the tending to steady stage. The inflection point of each stage can be regarded as the characteristic point of the vertical movement study of water. The difference of the growth curve of the settlement at each stage is related to the occurrence of the remnant collapsible settlement. The surface swell around the cap is more obvious than the surface settlement, so, the position and time of the sharply increasing of surface swell point can be used to study the lateral movement of water. The reasonable pile spacing of the DDC method and pile length are suggested as 1.1 m and 20m, respectively.

关 键 词：孔内深层强夯法 湿陷性黄土 地基处理 浸水载荷试验 沉降 

分 类 号：TU444[建筑科学—岩土工程]