波致液化粉质土中管线受力规律试验研究

发布时间：2018-04-13 16:04

本文选题：液化 + 粉质土　；参考：《中国海洋大学》2015年硕士论文

【摘要】：在海洋油气资源开发过程中,保障油气输运管线安全是非常重要的。铺设于浅海环境的海底管线,受复杂的波浪、海流等海洋动力联合作用,管线损坏事件时有发生。海底管线主要有埋置和裸置两种布置方式,一般认为在实际工程中裸置管线更易发生失效破坏,因此,目前研究人员更多关注于裸置管线的运营安全。在波浪作用下,由于压力的循环荷载,粉质土底床容易发生液化失稳。处于液化底床中的管线受力可能会远大于底床未液化时的管线受力,从而引起埋置管线的失效破坏。本文基于海底土体液化条件,开展埋置其中的管线受力状况的研究工作。本文采用室内波浪水槽试验方法,由于管线受力的复杂性,本文仅对垂向布设的压力传感器受力进行分析。试验以黄河三角洲粉质土制备的泥浆为试验底床,分别使用PVC管和钢制管模拟海底管线。在管线上、下两点布置压力传感器,测量管线所受的垂直向上、垂直向下以及垂向合力的压力大小。另外在压力传感器上方布设了小型波高仪,以记录该点波浪的实时变化对比传感器受力曲线与水位高度变化曲线的变化关系,并研究上、下两压力传感器的受力是否存在相位差。试验分为底床未液化与底床液化两个阶段。在底床未液化阶段,对底床施加四种不同的波浪,在加波的同时使用采集仪收集相关的管线受力数据。在人为扰动使底床液化后,施加与底床未液化阶段完全相同的波浪,收集压力数据的同时记录传感器所处各点的液化深度。本文利用相关数据研究了同一点管线上、下两压力传感器的实时受力以及管线在各阶段所受的垂直向上、垂直向下以及垂向合力的大小,重点对管线同一点上、下两传感器受力在某种情况下是否存在相位差,以及土体液化对管线受力相位差、土体垂向所受合力大小的影响进行研究。研究显示,在底床未液化阶段,管线同一点上、下两压力传感器受力完不存在相位差。在底床液化阶段,一般情况下两受力也不存在相位差,只有当波浪高度较大、液化深度较深时两受力才出现相位差,在某些工况下相位差大小可达波浪周期的0.4倍。两传感器所测力的方向完全相反,两力的和值即为管线垂向所受合力的大小。随着两受力从无到有出现相位差时,管线垂向受力将有一定幅度的增大。数据显示,同一波高作用下底床液化而没有出现相位差时,其管线垂向受力为底床未液化时的1-2倍。而当底床液化且出现一定相位差时,管线垂向受力达到底床未液化时的4-6倍。由于土体压力测量存在困难,试验结果与实际情况可能存在一定程度上的数值误差,但多次实验结果显示这种变化趋势真实可信。考虑到小模型试验与实际工况存在一定差距,因此下一步需要对概化模型条件下,液化粉质土中埋置管线的受力大小进行研究。
[Abstract]:In the process of exploitation of offshore oil and gas resources, it is very important to ensure the safety of oil and gas transportation pipeline.Submarine pipelines laid in shallow sea environment are often damaged by complex waves and currents.There are two kinds of layout modes of submarine pipeline: buried pipeline and bare pipeline. It is generally considered that bare pipeline is more prone to failure and failure in actual engineering. Therefore, researchers pay more attention to the operational safety of bare pipeline at present.Under the action of wave, the silty soil bed is prone to liquefaction instability due to the cyclic load of pressure.The pipeline in the bed of liquefaction may be much larger than the pipeline in the case of non-liquefaction of the bed, resulting in the failure of the buried pipeline.Based on the liquefaction condition of undersea soil, this paper studies the stress condition of buried pipeline.In this paper, the method of indoor wave flume test is used. Due to the complexity of pipeline force, this paper only analyzes the force of vertical pressure sensor.The mud prepared by silty soil in the Yellow River Delta was used as the test bed and the PVC pipe and steel pipe were used to simulate the submarine pipeline respectively.On the pipeline, pressure sensors are arranged at the next two points to measure the pressure of vertical upward, vertical downward and vertical forces on the pipeline.In addition, a small wave altimeter is arranged on the top of the pressure sensor to record the real time variation of the wave at this point and to compare the relationship between the stress curve of the sensor and the change curve of the water level and height.Whether there is a phase difference between the next two pressure sensors.The test is divided into two stages: non-liquefaction and non-liquefaction of bottom bed.In the non-liquefaction stage of the bottom bed, four different waves are applied to the bottom bed, and the data of the pipeline force are collected by using the collector while adding the wave.After the bottom bed is liquefied by artificial disturbance, the wave is applied exactly as in the non-liquefaction stage of the bottom bed, and the pressure data are collected and the liquefaction depth of the sensor is recorded at the same time.In this paper, the real time force of the next two pressure sensors on the same point pipeline and the magnitude of vertical upward, vertical downward and vertical forces on the pipeline at each stage are studied, with emphasis on the same point of the pipeline.Whether there is phase difference between the next two sensors and whether there is a phase difference between the two sensors and whether the soil is liquefaction has influence on the stress phase difference of pipeline and the vertical force of soil.The results show that there is no phase difference between the two pressure sensors at the same point of the pipeline in the non-liquefaction stage of the bottom bed.In the stage of bed liquefaction, there is no phase difference between the two forces in general. Only when the wave height is high and the liquefaction depth is deep, the phase difference between the two forces appears, and in some cases the phase difference can reach 0.4 times of the wave period.The two sensors measure the force in the opposite direction, and the sum of the two forces is the magnitude of the vertical force of the pipeline.With the phase difference between the two forces from scratch, the vertical force of the pipeline will increase to a certain extent.The data show that when the bed liquefies without phase difference under the same wave height, the vertical force of the pipeline is 1-2 times as high as that of the bed without liquefaction.When the bed is liquefied and there is a certain phase difference, the vertical force of the pipeline is 4-6 times as high as that of the bed without liquefaction.Because of the difficulty in measuring the soil pressure, there may be some numerical error between the test results and the actual conditions, but the experimental results show that the variation trend is true and reliable.Considering that there is a certain gap between the small model test and the actual working condition, the next step is to study the force of buried pipeline in liquefaction silty soil under the condition of generalizable model.
【学位授予单位】：中国海洋大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE95

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