夯扩挤密水泥土桩在黄土地基中的应用

The Application of Rammed Soil-Cement Compaction Pile in Loess Foundation

为研究湿陷性黄土地区水泥土夯扩桩的复合地基作用机理和承载能力,在湿陷性黄土场地上施做了4种不同桩间距和桩长的水泥土夯扩桩.开展桩间土压实度、桩体压实度和单桩复合地基静载试验,探讨桩间距和桩长对桩间土挤密效果、桩体压实效果和复合地基承载力的影响.结果表明:在重锤冲击和水泥土挤密作用下,桩周土压实度增大、湿陷性消除、承载力增大;桩间土挤密效果主要取决于桩间距,因桩体强度限制,桩长对承载力的贡献较低;等边三角形布桩,桩间距为2.7d时,挤密作用能够消除桩周土体的湿陷性,但压实度达不到规范要求;桩间距小至2.2d时,挤密效果显著提高,桩间土压实度满足规范要求,单桩复合地基承载力特征值达到300kPa.

In order to study the mechanism and bearing capacity of rammed soil-cement compaction pile composite foundation in collapsible loess area.4 types of rammed soil-cement compaction piles with different pile distance and pile length were applied on collapsible loess site.The compaction degree of soil between piles and pile body,the static load test of single pile composite foundation were carried out to discuss the influence of pile distance and pile length on soil compaction effect,pile compaction effect and bearing capacity of composite foundation.The test results show that under the action of heavy hammer impact and cement-soil compaction,the soil compactness around the pile increases,the collapsibility decreases and the bearing capacity increases.Soil compaction effect between piles mainly depends on the distance between piles.Due to the limitation of pile strength,the contribution of pile length to bearing capacity is low.When the pile distance is 2.7 d in equilateral triangle arrangement,the compaction can eliminate the collapsibility of soil around the pile,but the compaction degree cannot meet the requirements of the specification.When the pile distance is reduced to 2.2 d,the compaction effect is significantly improved which meets the requirements of the code,and the bearing capacity characteristic value of single pile composite foundation reaches 300 kPa.