水中沉井下沉期间刃脚空间受力试验

以沪通大桥沉井为背景，设计完成了深水大截面沉井下沉模拟试验。模拟了沉井在水中不排水吸泥下沉的过程，并分析了沉井在下沉过程中刃脚踏面和斜面应力在空间上的分布规律，得出沉井角点处应力最大，长边中点处最小，短边平均应力大于长边的结论。以长边中点为基准应力，确定了长宽比为1.33时刃脚全截面的应力系数。刃脚斜面上应力除受空间位置影响外还与泥面高度相关，且变化规律与踏面应力相反。当泥面高度确定后，用三次函数确定其应力分布。讨论了倾斜、翻砂突沉对刃脚受力的影响，得出两者均会引起刃脚空间受力分布的改变。发现沉井翻砂和突沉前后刃脚踏面应力、斜面应力、刃脚处水力梯度均会发生明显的变化，且变化趋势均早于沉井翻砂和突沉的发生，对沉井翻砂和突沉的预警有重要意义。

Experiments on spatial stress of foot blade during caisson sinking in water

A sinking simulation test of deep and large caisson is designed based on the caisson of Hutong Bridge. The undrained sucking sediment sinking of the caisson in the water is simulated and spatial distribution of the stress at the tread and oblique planes of the foot blade during the sinking process of the caisson. It concludes that the maximum stress occurs in corners of the caisson, the minimum stress occurs in the middle of long side, and the average stress at the short side is larger than that of the long side. Applying the reference stress at the midpoint of the long side, the total cross-section stress coefficient of the foot blade with the aspect ratio of 1.33 is calculated. In addition to be affected by spatial position, the stress on the incline plane of the foot blade is also greatly related with the mud surface height, and it changes contrary to the stresses at the tread. When the mud surface height is determined, the cubic function is used to determine its stress distribution. The influences of inclination, sand-casting and sudden sinking on the stress of the foot blade are also discussed and it is found that both can cause changes in spatial distribution of the stress of blade foot. Stresses at the tread and incline planes hydraulic gradient of the foot blade change significantly before and after the sand-casting and sudden sinking of caisson. They occur earlier than the sand-casting and sudden sinking of caisson and it is of great significance to early warning of sand-casting and sudden sinking.