A Novel Experimental Method Designed for Direct Measurement of the Critical Buckling Load of Piles in Liquefied Ground

Accurately measuring the critical buckling load (Pcr) of piles in fully liquefied ground remains a significant challenge, as existing dynamic tests can only observe the buckling phenomenon rather than provide a direct and quantitative load threshold. This study proposes a novel experimental method for the direct measurement of critical buckling load under coupled axial and lateral loading. A non-Newtonian fluid is developed to physically simulate the shear-thinning rheological behavior of fully liquefied sands, validated against the rheological curve of liquefied Nanjing sands.Based on this, a series of buckling tests on slender model piles are conducted, with the critical buckling load identified as the peak of the measured axial load-displacement curve. The experimental results demonstrate that lateral load significantly reduces the critical buckling load, with a reduction of up to 50.55% observed. Furthermore, the distribution of axial force along the pile and its bending-buckling interaction are analyzed. The reliability of proposed method is confirmed through pile-soil interaction analysis based on numerical simulations. This study provides a controlled, repeatable method for direct Pcr measurement, offering benchmark data for validating analytical and numerical models for pile buckling assessment in potentially liquefiable ground.