Strengthening range of super down-hole dynamic consolidation technology in collapsible loess foundation

doi:10.3785/j.issn.1008-973X.2025.04.010

Journal of ZheJiang University (Engineering Science)

2025, Vol. 59

Issue (4): 750-758 DOI: 10.3785/j.issn.1008-973X.2025.04.010

Strengthening range of super down-hole dynamic consolidation technology in collapsible loess foundation

Zhengzhen WANG1(

),Lei HUANG1,Guoliang DAI2,Yong ZHOU1,3,Tiantao SU1,4,*(

)

1. School of Civil Engineering, Lanzhou University of Technology, Lanzhou 730050, China
2. School of Civil Engineering, Southeast University, Nanjing 211189, China
3. School of Civil Engineering, Hexi University, Zhangye 734000, China
4. School of Civil Engineering, Lanzhou Institute of Technology, Lanzhou 730050, China

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Abstract

The plane strain problem of cylindrical hole expansion was solved based on the Mohr-Coulomb yield criterion, and the calculation formulas of effective reinforcement zone radius and final reaming pressure of super down-hole dynamic consolidation (SDDC) pile were derived. The theoretical solution correctness of the soil radial displacement around the pile was verified by field tests, and the influence of initial pore diameter and pile diameter on the soil squeezing effect was discussed. Results showed that the effective reinforcement zone radius of the SDDC pile in a collapsible loss foundation reaches more than 2 times the designed pile diameter. Both the radial stress and displacement of soil around the pile decrease logarithmically with the increase of the radial distance. The radial stress tends to the initial stress of the soil, and the radial displacement tends to 0. The attenuation amplitude of the stress field and displacement field is inversely proportional to the initial pore diameter and proportional to the pile diameter. The horizontal displacement of soil around the SDDC pile based on the cylindrical hole expansion theory under plane strain conditions is in good agreement with the measured values in the field, and the reinforcement range of SDDC pile can be calculated by using the theory.

Key words： collapsible loess foundation treatment super down-hole dynamic consolidation (SDDC) cavity expansion theory reinforcement range

Received: 14 February 2024 Published: 25 April 2025

CLC:

TU 472.3+2

Fund: 国家自然科学基金资助项目（52068048）；甘肃省青年科技基金计划资助项目（22JR5RA286）；甘肃省住房和城乡建设厅建设科技项目（JK2023-08）；兰州理工大学红柳优秀青年人才支持计划.

Corresponding Authors: Tiantao SU E-mail: wangzz@lut.edu.cn;sutt5008@163.com

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Cite this article:

Zhengzhen WANG,Lei HUANG,Guoliang DAI,Yong ZHOU,Tiantao SU. Strengthening range of super down-hole dynamic consolidation technology in collapsible loess foundation. Journal of ZheJiang University (Engineering Science), 2025, 59(4): 750-758.

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https://www.zjujournals.com/eng/10.3785/j.issn.1008-973X.2025.04.010 OR https://www.zjujournals.com/eng/Y2025/V59/I4/750

湿陷性黄土地基孔内深层超强夯技术的加固范围

基于Mohr-Coulomb屈服准则求解圆柱形孔扩张的平面应变问题，推导孔内深层超强夯（SDDC）桩有效加固区半径和最终扩孔压力的计算公式. 通过现场试验验证桩周土体径向位移理论解的正确性，探讨初始孔径与成桩直径对挤土效应的影响. 结果表明：湿陷性黄土地基中SDDC桩的有效加固区半径超过设计桩径的2倍；桩周土体的径向应力和位移均随着径向距离的增大呈对数衰减，径向应力趋于土体的初始应力，径向位移趋于0；应力场和位移场的衰减幅度与初始孔径成反比，与成桩直径成正比. 基于平面应变条件下圆柱形孔扩张理论得到的SDDC桩桩周土体水平位移与现场实测值吻合度较高，可以利用该理论计算SDDC桩的有效加固范围.

关键词： 湿陷性黄土, 地基处理, 孔内深层超强夯(SDDC), 圆孔扩张理论, 加固范围

Fig.1 Calculation model of cavity expansion theory

Fig.2 Test piles and deep horizontal displacement holes layout

Tab.1 Physical and mechanical indexes of soil

Fig.3 Photos of field deep horizontal displacement test

Fig.4 Variation of radial stress and radial displacement with radial distance

Fig.5 Development of deep horizontal displacements of measurement holes

Fig.6 Tapered rammer

Fig.7 Diagram of stress diffusion effect

Tab.2 Calculated and measured soil displacements

Tab.3 Influence of different pore diameters on reinforcement range of super down-hole dynamic consolidation (R_u=1.5 m)

Fig.8 Distribution of stress field and displacement field with different pore diameters (R_u=1.5 m)

Tab.4 Influence of different pile diameters on reinforcement range of super down-hole dynamic consolidation (R_i=1.2 m)

Fig.9 Distribution of stress field and displacement field with different pile diameters (R_i=1.2 m)


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