不同潮差作用下近海深大基坑围护结构力学响应规律研究

Study on the Mechanical Response Law of Offshore Deep and Large Foundation Pit Retaining Structure under Different Tidal Ranges

为更好探明近海潮汐对基坑围护结构力学响应的影响问题,本文采用以实测墙边地下水位数据为基础的模型边界潮汐地下水位振幅反演分析方法,反演得到适宜的不同潮差分析工况,研究了各振幅潮汐地下水作用下基坑围护结构的力学响应规律及响应机理。研究结果表明:(1)潮汐作用下,背海侧围护墙体侧移振幅沿深度增大逐渐降低,但靠海侧围护墙体侧移振幅分布与地层透水性密切相关,表现为与强透水层接触区域侧移振幅往往明显更大,故而基坑设计时应尽量避免静力工况最大侧移位置与强透水层位置重合;(2)若围护墙体弯矩峰值出现在强透水层区域,潮汐作用下的弯矩增量会远大于其他区域,加剧受力不均情况,但该现象随潮汐振幅增大而减弱;(3)同型内撑轴力振幅随竖向位置远离强透水层逐渐减小,并且由于结构形式和所处位置不同,各钢管撑轴力振幅随潮汐振幅增大平缓增长,而各砼撑轴力振幅随潮汐振幅增大呈突变式增长。

In order to better explore the influence of offshore tide on the mechanical response of foundation pit retaining structure,the model boundary tidal groundwater level amplitude inversion analysis method based on the measured groundwater level data near the wall is adopted to obtain suitable different tidal range analysis conditions,and the mechanical response law and response mechanism of foundation pit retaining structure under the action of tidal groundwater with different amplitudes are studied.The results show that:(1)Under the action of tide,the lateral displacement amplitude of the retaining wall at the sea side decreases gradually with the increase of depth,but the distribution of the lateral displacement amplitude of the retaining wall at the sea side is closely related to the permeability of the stratum,which shows that the lateral displacement amplitude of the contact area with the strong permeable layer is often significantly larger,so the maximum lateral displacement position of the static working condition should be avoided to coincide with the position of the strong permeable layer when designing the foundation pit;(2)If the peak value of the bending moment of the retaining wall occurs in the area of strong permeable layer,the increment of the bending moment under the action of tide will be much greater than that in other areas,which will aggravate the poor stress situation,but this phenomenon will weaken with the increase of the amplitude of tide;(3)The axial force amplitude of the same type of internal brace decreases gradually with the vertical position away from the strong permeable layer,and due to the different structural form and location,the axial force amplitude of each steel pipe brace increases slowly with the increase of the tidal amplitude,while the axial force amplitude of each concrete brace increases abruptly with the increase of the tidal amplitude.