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许多学者基于圆孔扩张理论,采用挤土应力不变的假设给出了黏性土中挤土桩承载力时效性的解析解答,但是原位试验表明:作用在桩壁上的挤土应力是不断衰减的。通过利用应力路径三轴仪进行应变保持试验,模拟沉桩及随后的桩周土体的应力状态和物理性质的改变。试验结果表明:沉桩后作用在桩壁上的作用力近似呈对数衰减,桩周土体有效应力先减小后增大,固结完成后有效应力增量仅为(0.2～0.27)倍的超静孔隙水压力。因而,采用挤土应力不变的假设将导致过高估计桩基承载力的时效性。
Many scholars based on the theory of circular hole expansion, using the assumption of constant soil squeezing stress gives the analytical solution of the time-dependent bearing capacity of the compacted soil pile in cohesive soil. However, in situ tests show that the soil compaction stress acting on the pile wall is Decaying. Strain retention experiments were carried out using a stress path triaxial apparatus to simulate the changes in the stress state and physical properties of the sinking and subsequent soil around the pile. The experimental results show that the acting force acting on the pile wall is approximately logarithmically decayed after piling, the effective stress of the soil around the pile first decreases and then increases, and the effective stress increment after the consolidation is only (0.2-0.77) times Excess pore water pressure. Therefore, the assumption of constant soil squeezing stress will lead to overestimation of the timeliness of pile bearing capacity.