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<p>To investigate the impact of distributed post-grouting technology on the bearing performance of drilled shafts in clay, a model shaft test involving post-grouting and subsequent excavation was conducted to visually analyze the grout diffusion mechanism and soil reinforcement effect. Based on bidirectional O-cell tests on two large diameter drilled shafts from the Shandong Xiaoqing River Navigation Restoration Project, the differences in the axial load-bearing behavior of individual shafts before and after distributed grouting were analyzed. Furthermore, the mobilization mechanism of shaft side resistance before and after grouting was elucidated through direct shear model tests, including an in-depth analysis of its depth-dependent behavior. The results indicated that distributed post-grouting enabled small spacing, high-frequency, multi-section grouting, effectively addressing issues such as side mud cake and soil disturbance commonly encountered in drilled shaft construction. Both distributed post-grouting and combined post-grouting significantly increased the ultimate bearing capacity compared to ungrouted shafts, with a 52.2% increase for distributed post-grouting and a 39.6% increase for combined tip-and-side post-grouting. Under similar conditions, distributed post-grouted shafts exhibited slightly higher enhancement coefficients for side resistance compared to combined tip-and-side post-grouted shafts. Moreover, depth effects were observed in the mobilization of side resistance and enhancement coefficients after grouting, a conclusion further confirmed by shear model tests. Distributed post-grouting not only filled and reinforced the shaft–soil interface but also transformed the mobilization mechanism of side resistance: from one dominated by the development of cohesion dependent on displacement accumulation to a regime dominated by friction enhancement governed by composite material mechanics. The depth effect was pronounced, necessitating the adoption of the lower-bound values, or values further reduced below these lower bounds, for the side resistance enhancement factors recommended by design codes when the depth was less than approximately <i>L</i>/3.</p>

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Experimental study on axial response and side resistance mobilization mechanism of large diameter distributed post-grouted drilled shafts in cohesive soil

  • 期刊论文

  • 发表日期：

    2025年11月22日

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  • Zhihui Wan,
  • Zilong Guo,
  • Jiale Jin,
  • Xiaonan Qian,
  • Guoliang Dai,
  • Hao Liu

摘要

To investigate the impact of distributed post-grouting technology on the bearing performance of drilled shafts in clay, a model shaft test involving post-grouting and subsequent excavation was conducted to visually analyze the grout diffusion mechanism and soil reinforcement effect. Based on bidirectional O-cell tests on two large diameter drilled shafts from the Shandong Xiaoqing River Navigation Restoration Project, the differences in the axial load-bearing behavior of individual shafts before and after distributed grouting were analyzed. Furthermore, the mobilization mechanism of shaft side resistance before and after grouting was elucidated through direct shear model tests, including an in-depth analysis of its depth-dependent behavior. The results indicated that distributed post-grouting enabled small spacing, high-frequency, multi-section grouting, effectively addressing issues such as side mud cake and soil disturbance commonly encountered in drilled shaft construction. Both distributed post-grouting and combined post-grouting significantly increased the ultimate bearing capacity compared to ungrouted shafts, with a 52.2% increase for distributed post-grouting and a 39.6% increase for combined tip-and-side post-grouting. Under similar conditions, distributed post-grouted shafts exhibited slightly higher enhancement coefficients for side resistance compared to combined tip-and-side post-grouted shafts. Moreover, depth effects were observed in the mobilization of side resistance and enhancement coefficients after grouting, a conclusion further confirmed by shear model tests. Distributed post-grouting not only filled and reinforced the shaft–soil interface but also transformed the mobilization mechanism of side resistance: from one dominated by the development of cohesion dependent on displacement accumulation to a regime dominated by friction enhancement governed by composite material mechanics. The depth effect was pronounced, necessitating the adoption of the lower-bound values, or values further reduced below these lower bounds, for the side resistance enhancement factors recommended by design codes when the depth was less than approximately L/3.