This paper examines factors controlling the ultimate shaft friction developed on buried piles in normally consolidated clay–sand mixtures and explores the relationship between this friction and the cone penetration test (CPT) end resistance. Results from tension load tests on buried piles in a laboratory pressure chamber and geotechnical centrifuge are presented. Variable rate CPTs combined with Rowe cell, undrained simple shear and interface direct shear tests are used to characterise the mixtures. It is shown that the measured drained CPT end resistances could be predicted using parameters assessed from the laboratory tests and a simple expression derived from cavity expansion theory in an elastic Mohr–Coulomb soil. The tension pile tests indicate how changes in radial effective stresses during loading can be inferred from interface shear tests and these combined with the cavity expansion analysis allow derivation of a relationship between shaft friction (τ_f) and CPT end resistance (q_t). This expression reveals the significant effects on the q_t/τ_f (= β_c) ratio of soil stiffness, stress level, dilation and drainage during cone penetration and is shown to be consistent with a recently proposed empirical formula for bored piles.

中文翻译：

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黏性砂土中埋桩的竖向摩擦与CPT阻力的关系

本文研究了控制正常固结粘土-砂混合物中埋桩上产生的最终竖井摩擦力的因素，并探讨了该摩擦力与圆锥渗透试验（CPT）端部阻力之间的关系。给出了在实验室压力室和岩土离心机中对地下桩进行拉伸载荷测试的结果。可变速率的CPT与Rowe池，不排水的简单剪切和界面直接剪切测试相结合来表征混合物。结果表明，可以使用实验室测试评估的参数以及由弹性莫尔-库仑土壤中的腔体扩张理论得出的简单表达式来预测测得的CPT排空端电阻。τ _˚F）和CPT端电阻（q_吨）。此表达揭示了在所述显著效果q_吨/ τ _˚F（=  β _{c ^}）锥入过程中的土壤的硬度，应力水平，扩张和排水的比，被示出为具有用于钻孔桩最近提出的经验式是一致的。