井口导管水平承载力循环退化机理研究

Investigation on the cyclic degradation mechanism of lateral bearing capacity of wellhead conductor

针对黏土强度的扰动退化机理,采用累积位移建立p-y曲线的循环退化效应,并在ANSYS中建立循环p-y曲线用户单元进行循环荷载作用下井口导管水平承载力退化机理研究,分析循环幅值、循环次数以及风暴海况对导管承载性能的影响。研究结果表明,循环p-y曲线用户单元的土反力随累积位移逐渐衰减至稳定值,循环位移幅值越大,土反力衰减越快;在循环位移荷载作用下,导管最大弯矩、水平承载力随循环次数不断减小至稳定值,且循环位移幅值越大衰减越显著;风暴海况会加剧管周土体强度的退化,风暴下导管水平承载力降低19.2%,风暴海况后导管水平承载力明显小于正常海况情况。本文研究成果对井口导管的安全受力分析具有指导意义。

According to the disturbance degradation mechanism of clay strength,the cumulative displacement was used to establish the cyclic degradation effect of p-y curve,and the client unit of p-y curve was established in ANSYS to investigate the lateral bearing capacity degradation mechanism of wellhead conductor under cyclic loading,which analyzed the impacts of the amplitude and number of cycles,as well as storm sea conditions on the bearing capacity of conductor. The study results show that the soil resistance of such p-y curve gradually decays with the cumulative displacement towards a stable value. The larger the cyclic displacement amplitude,the faster the decline of soil resistance;under the cyclic displacement load,the maximum bending moment and the lateral bearing capacity of the conductor attenuate with the number of cycles towards a stable value,and the larger the amplitude of cyclic displacement,the more significant the attenuation will be. Storm sea conditions will aggravate the degradation of soil strength around the pipe,and the lateral bearing capacity of the conductor can be reduced by 19.2 % under those conditions. The capacity will be significantly smaller than that of the normal sea conditions. The study results in this paper are of great guiding significance for the safety analysis of wellhead conductors.