复合加载下软基上半圆堤结构稳定性分析

半圆堤是适用于软土地基的一种轻型重力式的新型防波堤结构，复合加载模式下软基上半圆堤的稳定性计算和结构破坏模式尚需建立合理的分析和计算方法。将加载模式与软基上大型海岸结构稳定性分析的有限元模拟方法相结合，同时考虑半圆堤在不同荷载组合时可能发生沿底板或抛石基床底部的滑动破坏及地基竖向承载力破坏，建立了复合加载模式下软基上半圆堤的稳定性分析方法，得出了结构的稳定性破坏模式和破坏包络线（面），并分析了箱内填砂量、抛石基床宽度及地基加固深度对半圆堤稳定性的影响。计算结果表明：半圆堤结构在复合荷载作用的破坏包络线（面）均由一定区域的结构滑移破坏面和地基承载力破坏线（面）组成，并将整个荷载组合区分成4个区域：稳定区、只发生滑移破坏区、只发生地基承载力破坏区和同时发生滑移和地基承载力破坏区；荷载与位移组合加载模式得到的地基承载力破坏包络线位于Swipe加载方式得到的破坏包络线之外，但对每种加载方式得到的地基承载力破坏包络线变化趋势基本一致；随着箱内填砂高度的增加沿沉箱底部和抛石基床底部的抗滑安全系数均增加，但地基承载力安全系数减小；随着抛石基床宽度或地基加固深度的增加，地基承载力安全系数明显增大。

Stability analysis of semi-circular breakwater on soft foundation under combined loading

The semi-circular breakwater is a new light gravity type of structure suitable for soft foundation. It is necessary to establish a reasonable calculation and analysis method for stability and failure mode of the semi-circular breakwater under combined loads. Stability analysis method of the semi-circular breakwater under combined loads is developed by combining load mode with finite element method of the large coastal structures on soft foundation. Meanwhile, sliding failure along the bottom of the base plate and rubble-mound foundation, and vertical bearing capacity failure of the soil foundation are considered. Furthermore, stability failure mode and failure envelopes of structural bearing capacity are obtained. Finally, the effects of amount of filling sand in caisson, the width of rubble-mound foundation, and the reinforcement depth of soil foundation on stability of the semi-circular breakwater are analyzed. The calculating results show that the sliding surface and foundation bearing capacity failure lines of the semi-circular breakwater under combined loading divide the whole V-H loads space into four regions, namely stable region, slide-only failure region, region where only foundation bearing capacity failure happens and region where both sliding failure and foundation bearing capacity failure happen. The foundation bearing capacity failure line obtained by load and displacement composite load mode is outside the failure line obtained by Swipe load mode. But for each load mode, change trends of foundation bearing capacity failure lines are almost consistent. It can be seen that safety factors of stability against sliding along the bottom of caisson or rubble-mound foundation both increase with the height of filling sand in caisson, but safety factors of foundation bearing capacity decrease. Meanwhile, safety factors of foundation bearing capacity obviously increase with the increase of width of rubble-mound foundation or reinforcement depth of foundation.