利用循环强度分析张紧式吸力锚循环承载力的方法

按照在最佳系泊点受倾斜荷载作用的张紧式吸力锚的破坏机制，建议了利用软土不排水循环剪切强度计算软土中吸力锚循环承载力的极限平衡分析方法。该方法考虑了平均系泊荷载在土中引起的平均剪应力对土体循环剪切强度、进而对锚循环承载力的影响。为了说明该方法的可行性，进行了大量张紧式吸力锚在平均系泊荷载与循环荷载共同作用下的承载力模型试验。依据试验结果确定了锚被竖向拔出土层时系泊点的位移破坏标准，并据此确定了与不同模型试验条件对应的循环承载力。进而利用循环三轴试验确定的土层不排水循环强度随平均应力的变化关系和实测的土层剪切强度，通过极限平衡分析计算了与模型试验对应的循环承载力。计算与模型试验结果比较表明，对于张紧式吸力锚被竖向拔出土层的破坏模式，计算结果比模型试验结果偏大，平均偏大1.9%，绝大多数偏差在10%以内。因此，对于软土中的张紧式吸力锚，如果采用该方法计算与竖向拔出土层破坏模式相应的循环承载力时，将结果减小10%是恰当的。

Method for analyzing cyclic bearing capacity of suction anchor with taut mooring system using cyclic strengths

A limiting equilibrium method for calculating cyclic bearing capacities of suction anchors in soft clays using undrained cyclic shear strength of soft clays was developed based on the failure mode of suction anchors with inclined loads at the optimal loading point. Effects of average shear stresses due to average mooring loads on cyclic shear strengths of soft clays and cyclic bearing capacities of suction anchors were considered for the method. In order to verify its feasibility, a large number of model tests of suction anchors with combined average and cyclic mooring loads were conducted associated with different test parameters. The displacement criterion to failure at the loading point associated with the vertical pullout failure mode was determined based on test results. Cyclic bearing capacities of model tests with different parameters were determined based on the criterion. Cyclic bearing capacities associated with different model tests were further calculated by limiting equilibrium analyses using the relationship determined by undrained cyclic triaxial tests between normalized cyclic strengths and normalized average stresses and measuring shear strengths of model test strata. Comparison between calculating and testing results show that calculating results larger than testing results for the vertical pullout failure mode of suction anchors with taut mooring system. The average difference between them is 1.9%. Most of differences are not more than 10%. Therefore, it is appropriate that the calculating result is decreased 10% if the cyclic bearing capacity associated with the vertical pullout failure mode is calculated using the method for suction caissons with taut mooring system in soft clays.