沿深度强度增加软土中吸力锚循环承载力模型试验

Model tests on the cyclic bearing capacity of suction anchors in the soft clay with the increase of strength along the depth

采用分层底部真空预压技术,在模型试验箱内制备了强度沿深度增加的模型试验土层。进而利用自行开发的电动伺服加载装置,在荷载控制方式下,针对水平破坏模式,进行了2种直径的吸力锚在最佳系泊点受倾斜方向静荷载与循环荷载共同作用下的承载力模型试验。试验结果表明,循环荷载作用过程中,锚的循环变形没有明显增加,导致锚破坏的是循环累积变形。强度沿深度增加软土中吸力锚循环承载力的相对变化规律和均一强度软土中吸力锚循环承载力的相对变化规律一致,当循环破坏次数为100时,循环承载力是静承载力的90%左右;当循环破坏次数增加至2 000时,循环承载力减小至静承载力的70%左右。锚径的变化只影响循环承载力的大小,不影响循环承载力的相对变化。对强度沿深度增加土层中的吸力锚,循环荷载导致的吸力锚竖向阻力弱化程度大于水平阻力弱化程度,这也与均一强度土层中吸力锚受循环荷载作用时的性态一致。

The model test stratum with the increase of strength along the depth was prepared in a tank us-ing multilayer vacuum preloading method at the bottom. Bearing capacity model tests were conducted forsuction anchors with two diameters and subjected to inclined static and cyclic loads at the optimal loadingpoint using an electric servo loading apparatus developed by the authors for the lateral failure mode. Modeltest results show that the cyclic displacement of anchor is not obviously increase with the increase of thenumber of load cycles and the failure of anchors is due to the cyclic cumulative displacements. The rela-tive variation of cyclic bearing capacity for suction anchors in the soft clay with the increase of strengthalong the depth is consistent with that for suction anchors in the soft clay with uniform strength along thedepth. The cyclic bearing capacity is about 90 % of the static bearing capacity when the number of load cy-cles is 100 and the cyclic bearing capacity decreases about 70 % of the static bearing capacity when thenumber of load cycles increases to 2 000. The variation of anchor diameter only change the absolute cyclicbearing capacity,does not affect relative variation of the cyclic bearing capacity. The degradation of the ver-tical resistance is larger than that of the lateral resistance for suction anchors in soft clay with the increaseof strength along the depth under cyclic loads,which is the same as that for suction anchors in soft claywith uniform strength along the depth.