Abstract

To clarify the poorly understood soil-structure interactions flanking the pile cap, this study systematically investigates the sensitivity of the New Type Concrete Expanded-Plate (NT-CEP) pile system to variations in sub-cap silt profiles, specifically moisture content (12%~16%) and dry density (80%~90% compaction degree). Mechanical results indicate that the pile cap and expanded bearing plates operate via a robust synergistic load-sharing mechanism, with plastic failure zones localized beneath these components. Within conventional physical limits, fluctuations in moisture and density trigger less than a 4% variance in the ultimate compressive capacity, demonstrating the remarkable structural resilience of the internal compensatory load-transfer path. Based on the evaluated boundary conditions, a site-specific operational envelope featuring a minimum compaction degree of 80% and a critical moisture threshold below 14% is recommended as a preliminary reference. Nevertheless, explicit mechanical limitations must be rigorously addressed: these quantitative thresholds are strictly benchmarked against the scaled model testing utilizing a specific silt thickness and pile geometric stiffness ratio. Significant deviations in these parameters are expected under three distinct boundary constraints: (1) altered multi-axial stress paths inherent to complex interbedded geologies; (2) catastrophic matric suction loss and pore pressure accumulation driven by elevated groundwater tables; and (3) severe skin friction degradation common in thixotropic soft clays. Consequently, these indicators constitute a context-specific design envelope rather than a rigid universal standard, providing a mechanics-driven baseline for the gradient optimization of advanced NT-CEP foundations while delineating required calibration paths for future full-scale field instrumentation.

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