多因素下滨海软黏土循环后强度弱化研究及应用

Research and application on strength weakening character of littoral soft clay affected by cyclic loading under different influencing factors

随着近海工程向深水化、大型化发展,波浪循环荷载作用下软黏土地基弱化问题越来越受到关注。文章以烟台港原状淤泥质黏土为研究对象,通过动三轴试验,研究了不同围压、动应力和静偏应力影响下循环后不排水抗剪强度弱化规律和应力路径发展规律。在此基础上考虑实际工程中的土体状况,增加了固结度这一新的影响因素。试验结果表明存在固结度临界动应力比0.2,当动应力比小于等于0.2时,固结度对于土体强度弱化的影响基本一致;当动应力比大于0.2时,固结度对于强度弱化的影响突然加速。根据试验规律建立了综合考虑围压、动应力、静偏应力和固结度的多因素影响下不排水抗剪强度弱化公式,并采用拟静力方法将公式应用于烟台港防波堤数值模型的计算中,结果表明考虑强度弱化效应的计算方法更加接近工程实际。

With the development of offshore engineering,strength reduction of soft clay foundation under cy-clic loading is attracting more attention. By means of performing cyclic triaxial test on muddy clay taken from Yan-tai littoral zone, undrained shear strength weakening and stress path of clay has been studied in different confiningstress, deviator stress and dynamic stress. Given the actual soil condition in the engineering, the effect of consolida-tion degree has also been studied. Critical dynamic stress ratio has been found in the test. When the dynamic stressratio is less than or equal to 0.2, strength reduction is affected by consolidation degree identically. On the contrary,when the dynamic stress ratio is greater than 0.2, consolidation degree has great influence on strength reduction. Ac-cording to the test, a strength weakening formula which contains different influencing factors was put forward. Thenthe formula was applied to the numerical model of breakwater in Yantai Port by using pseudo-static method. The re-sults show that the calculation method with strength weakening is more close to the engineering practice.