冰对码头桩结构作用力的物理试验和模拟研究

PHYSICAL EXPERIMENTS AND SIMULATION OF SEA ICE FORCE ON PILE STRUCTURES IN PORTS

为了解决码头中大直径圆筒结构、小直径群桩结构的冰力问题,开展系列物理模拟试验研究。针对直径较大的圆筒或圆沉箱结构,通过物理模拟试验将Afanasev公式适合小直径直立圆柱桩(D/h≤6)的范围拓展到大直径直立圆柱结构(D/h≤50)。由于渤海多数时间的海冰厚度<20cm,新的试验统计关系适用渤海直径<25m直立圆柱结构上的冰力评估。当为了获得大型码头结构中倾斜和多排群桩各桩冰力分配,但又受模型比尺和水槽尺度的限制时,采用将整体结构分解成多个测试单元,分别测试各个单元上的冰力并同时测量同直径单直立圆柱桩上的冰力,建立复杂群桩结构上各个单桩同单直立圆柱桩之间的冰力等效关系,然后利用单直立圆柱桩的冰力计算公式和原型冰压缩强度、冰厚度、桩直径、等效系数来复原复杂结构物上的原型冰力和各桩上的的原型冰力。这种做法回避原型冰力复原时用简单相似理论解决复杂结构问题的难题。应用这些原则,物理模拟试验得到三种不同类型群桩结构各桩冰力分配;前后桩之间的遮蔽系数以及与单直立圆柱桩的等效系数。这些结果在渤海海冰工程中具有一定普适性。

A series of physical simulation experiments of ice forces on different kind of piles in ports were performed in order to resolve the ice forces on the vertical piles of large diameters and inclined multi-piles of small diameters in ice-infested port engineering. For expressing the ice forces on lager piles and caissons, Afanasev equation, suitable for small piles with D/h≤6, is extended to larger cylinders with D/h≤50 on the basis of a series of physical simulation experiment results. Because the thickness of Bohai sea ice is less than 20 cm in most time of a winter, the new statistical formula can be used to calculate ice forces on piles or columnar caissons with 25m diameter in Bohai. For obtaining the ice force distribution on each pile in inclined piles and pile arrays, the whole structure is divided into several smaller elements which are tested individually and are compared with the ice forces on the vertical pile with the same diameter while the structure is lager and can not follow the requirement of designed model scale and flume dimensions. Therefore, the relations between ice forces on each pile and each element and their effective factors are set up by the ratio of measured ice forces on them and the vertical pile. The full scale ice force on the vertical pile can be calculated by Afanasev equation and full scale ice compressive strength, the thickness and pile diameter, and the full scale ice forces on inclined pile and pile arrays can be recovered by the full scale ice force on the vertical pile and the effective factors. This way slides over the difficulties of ice forces on complex structures from model scale to full scale by simple similarity theory. Following this principle, the physical simulation experiments obtain the ice force distribution on each pile of three types of pile arrays, their shielding factors between fore and after piles and effective factors to the vertical pile. These results are universality in Bohai ice engineering.