轴向荷载作用下管与软土相互作用模型试验

Model tests on interaction between pipeline and soft clay under axial loading

开展室内模型试验研究了PE涂层足尺管道在软弱黏土中发生纵向位移时静置时间、加载速率以及土层不排水抗剪强度3个因素对轴向摩擦特性的影响。研究表明,管与软黏土纵向相互作用的抗力-位移曲线存在硬化型和软化型两种形式,前者的峰值摩擦阻力一般出现在加载过程的最后阶段,而后者的峰值摩擦阻力则出现在相对位移为(0.005~0.02)D(D为管直径)范围内;试验测得的峰值摩擦系数取值介于0.12~0.23之间,且该值比美国API规范推荐值偏小;管土纵向峰值摩擦系数与加载速率成正相关关系,且加载速率对抗力-位移曲线类型无显著影响;常见的不排水抗剪强度范围内,土层的不排水抗剪强度值越低,纵向摩擦系数越大。上述结论可为海底埋设管线与软黏土纵向相互作用摩擦系数的确定提供参考依据。

The effect of three influential factors including the pause period, the loading rate and the undrained shear strength of soft clay on the axial friction property is investigated using the laboratory model test, when the relative axial displacement of the full-scaled PE-coated pipe and the soft clay take place. The research revealed that there are two forms of force-displacement curves of pipe-clay axial interaction: hardening type and softening type. The peak resistance mobilization distance ranges of 0.005 D to 0.02D(D: the diameter of the pipe) for softening type while appears in the last stage of the loading process for hardening type. The peak measured friction coefficients ranged from 0.12 to 0.23 are less than the API recommended values. The peak fiction coefficients are positively related to the loading rates; but the loading rates have no significant effect on the forms of force-displacement curves. The fiction coefficients of clay with high shear strength are lower than the fiction coefficients of clay with low shear strength within the scope of common undrained shear strengths. The conclusion provides references for determining the friction coefficient of axial interaction between buried marine pipeline and clay.