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<p>Self-compensating steel struts (SCSS) are extensively employed in sensitive urban areas to control excavation-induced deformation. However, the deformation mechanisms of excavations supported by SCSS are not fully understood, and the initial axial forces for servo-struts during installation remain unclear. This study presents a field test conducted at a foundation pit in Zhengzhou to investigate the effects of active axial force adjustments in steel struts on the horizontal displacement of diaphragm walls, strut axial forces, and ground settlement. By leveraging the operational principles of servo steel struts, an innovative “axial force threshold method” is proposed to elucidate the dynamic response of excavation behaviour to variations in the preset axial force thresholds. The results indicate that the initial application of servo struts effectively counteracts the adverse effects of excavation unloading, with excessive axial force thresholds leading to soil heave outside the pit. Compared with conventional noncompensating struts, SCSS demonstrated significantly smaller fluctuations in axial force during excavation and completely avoided the loss of preload. Upon reaching the final excavation level, the maximum wall horizontal displacement and surface settlement were measured at 21&#xa0;mm and 7&#xa0;mm, respectively, representing reductions of 19.2% and 72% compared with those of a pit supported by noncompensating struts. The proposed axial force threshold method substantially enhanced deformation control. With the axial force thresholds for the second and third strut levels set within ranges of 1254–2940 kN and 2242–5256 kN, respectively, the maximum wall displacement and surface settlement were controlled to 33.3&#xa0;mm and 22.5&#xa0;mm, respectively, while the bending moments in the diaphragm wall remained below the design value of 1248 kN·m. The optimal performance was achieved with thresholds of 2940 kN (second level) and 5256 kN (third level), resulting in minimum displacements of 12.1&#xa0;mm (wall) and 10&#xa0;mm (settlement), respectively. This research provides both theoretical underpinnings and practical guidance for optimizing the design parameters of servo steel strut systems.</p>

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Displacement and Force Analysis of Self-compensating Steel Supports in the Deep Excavation Process via In Situ Testing and 3D FEM

  • 期刊论文

  • 发表日期：

    2026年2月20日

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  • Mingyu Li,
  • Yunpeng Cai,
  • Ping Jin,
  • Junwei Jin,
  • Pei Huang,
  • Yingbin You

摘要

Self-compensating steel struts (SCSS) are extensively employed in sensitive urban areas to control excavation-induced deformation. However, the deformation mechanisms of excavations supported by SCSS are not fully understood, and the initial axial forces for servo-struts during installation remain unclear. This study presents a field test conducted at a foundation pit in Zhengzhou to investigate the effects of active axial force adjustments in steel struts on the horizontal displacement of diaphragm walls, strut axial forces, and ground settlement. By leveraging the operational principles of servo steel struts, an innovative “axial force threshold method” is proposed to elucidate the dynamic response of excavation behaviour to variations in the preset axial force thresholds. The results indicate that the initial application of servo struts effectively counteracts the adverse effects of excavation unloading, with excessive axial force thresholds leading to soil heave outside the pit. Compared with conventional noncompensating struts, SCSS demonstrated significantly smaller fluctuations in axial force during excavation and completely avoided the loss of preload. Upon reaching the final excavation level, the maximum wall horizontal displacement and surface settlement were measured at 21 mm and 7 mm, respectively, representing reductions of 19.2% and 72% compared with those of a pit supported by noncompensating struts. The proposed axial force threshold method substantially enhanced deformation control. With the axial force thresholds for the second and third strut levels set within ranges of 1254–2940 kN and 2242–5256 kN, respectively, the maximum wall displacement and surface settlement were controlled to 33.3 mm and 22.5 mm, respectively, while the bending moments in the diaphragm wall remained below the design value of 1248 kN·m. The optimal performance was achieved with thresholds of 2940 kN (second level) and 5256 kN (third level), resulting in minimum displacements of 12.1 mm (wall) and 10 mm (settlement), respectively. This research provides both theoretical underpinnings and practical guidance for optimizing the design parameters of servo steel strut systems.