夯扩挤密桩处理湿陷性黄土地基挤密效果和水平应力变化规律研究

Study on compaction effect and horizontal stress of collapsible loess foundation treated by rammed-expanded compaction pile

摘要

为研究灰土夯扩挤密桩处理湿陷性黄土公路路基时挤密效果和水平应力沿深度的变化规律，选用不同桩径、桩间距的灰土夯扩挤密桩处理湿陷性黄土地基，分析处理前后深度范围内桩周土挤密系数、水平应力、超固结比、锥尖阻力和侧壁阻力变化规律。研究结果表明：灰土夯扩挤密桩可显著增大处理深度范围内桩间土平均挤密系数、湿陷系数、水平应力、固结度、锥尖阻力和侧壁阻力，进而提高地基承载力。桩间距从1.0 m增大为1.2 m和1.5 m时，桩间土平均挤密系数分别增大了1.37%和4.11%,平均湿陷系数分别增大了1.75倍和2.79倍；桩间距为1.0 m、1.2 m和1.5 m时，400 mm桩径对应的平均水平应力比分别为3.23、2.47和1.92,超固结比分别为11.58、6.64和3.94,平均桩尖阻力分别增大了2.54倍、1.92倍、1.31倍，侧壁阻力分别增大了3.07倍、2.35倍、1.47倍。450 mm桩径对应的平均水平应力比分别为3.52、2.74和2.21,超固结比分别为13.80、8.26和5.27,平均桩尖阻力分别增大了2.77倍、2.03倍和1.39倍，侧壁阻力分别增大了3.40倍、2.59倍和1.66倍，且桩间距对上述桩间土参数的影响程度均大于桩径。实际工程中建议采用桩间距≤1.2 m的灰土夯扩挤密桩处理湿陷性黄土地基。

Abstract

In order to study the change of compaction effect and horizontal stress along the depth of collapsibility loess highway subgrade treated by rammed-expanded lime-soil compaction piles with different pile diameters and pile spacing, the compaction coefficient, horizontal stress, over-consolidation ratio, cone tip resistance and side-wall resistance around the pile were analyzed. The results show that the compaction coefficient, collapsibility coefficient, horizontal stress, consolidation degree, cone tip resistance and side-wall resistance of soil between piles can be significantly increased in the range of treatment depth, and then the bearing capacity of the foundation is mentioned. When the pile spacing increases from 1.0 m to 1.2 m and 1.5 m, the average soil compaction coefficient between piles increases by 1.37% and 4.11%, and the average collapsibility coefficient increases by 1.75 and 2.79 times, respectively. When the pile spacing is 1.0 m, 1.2 m and 1.5 m, the average horizontal stress ratio corresponding to the 400 mm pile diameter is 3.23, 2.47 and 1.92, the over-consolidation ratio is 11.58, 6.64 and 3.94, respectively, the average cone tip resistance increases by 2.54 times, 1.92 times and 1.31 times, respectively, and the side-wall resistance increases 3.07 times, 2.35 times and 1.47 times, respectively. The average horizontal stress ratio corresponding to the pile diameter of 450 mm is 3.52, 2.74 and 2.21, the over-consolidation ratio is 13.80, 8.26 and 5.27, respectively, the average cone tip resistance increases by 2.77 times, 2.03 times and 1.39 times, and the side-wall resistance increases by 3.40 times, 2.59 times and 1.66 times, respectively. The influence of pile spacing on the soil parameters above is greater than that of pile diameter. In practical engineering, it is recommended to treat collapsible loess foundation with rammed-expanded lime-soil compaction pile with pile spacing≤1.2 m.

关键词

湿陷性黄土地基 / 灰土夯扩挤密桩 / 桩间土 / 挤密系数 / 水平应力

Key words

collapsible loess foundation / rammed-expanded lime-soil compaction pile / soil between piles / compaction coefficient / horizontal stress

Author summay

周勤帮(1982—), 男, 高级工程师, 学士, 主要从事公路施工及养护技术研究。E-mail: [e-mail]

基金资助

国家重点研发计划“十四五” 交通基础设施专项(2023YFB2604804)

国家自然科学基金项目(42362033)

国家自然科学基金项目(52268058)

甘肃省产业支撑计划项目(2023CYZC-34)

甘肃省教育厅青年博士支持项目(2024QB-053)

兰州交通大学专利转化引导基金项目(ZH2023008)