摘要
地震发生时,尤其是直下型地震发生时,P波对场地土体的作用不可忽略。通过变围压动三轴设备施加的特殊应力路径,模拟了P波和S波耦合对饱和软黏土动力特性的影响,即循环剪应力和循环正应力耦合对饱和软黏土动力特性的影响。试验结果表明:变围压动三轴试验得到的包括循环剪应力和循环正应力的应力路径可以较好地模拟P波和S波的耦合作用;循环剪应力和循环正应力的相位差对饱和软黏土的动强度有较大的影响,当相位差为180°时,土体的动强度最低,当相位差为0°时,动强度最高;随着循环正应力幅值的增大,土体的动应变发展速度与常规恒定围压动三轴试验下的动应变发展速度相比,差距逐渐增大。这些发现一方面表明强震过程中P波的作用不可忽略,另一方面表明,在某些情况下,常规恒定围压动三轴试验高估了饱和软黏土的动强度,对抗震设计不利。
In the earthquakes with high intensities, the effects of P-waves on the soil layers cannot be ignored. The coupling effects of S-waves and P-waves are simulated by the specific stress paths in the cyclic triaxial tests with cyclic confining pressure. The influences of the phase differences and ratios between cyclic shear stress and cyclic normal stress on the behavior of cyclic strain are studied. It is found that the specific stress paths which are composed of both cyclic shear stresses and cyclic normal stresses are appropriate to simulate the coupling effects of S-waves and P-waves. The phase difference strongly influences the cyclic strength of saturated clays, i.e., when the phase angle is 180°, the cyclic strength is the lowest, and when the phase angle is 0% the cyclic strength is the highest. With the increasing ratios, the development speeds of cyclic strain are becoming more different from the results of conventional cyclic triaxial tests. These findings indicate that the effects of P-waves are significant, and in some cases the conventional cyclic triaxiai tests may overestimate the cyclic strength of saturated clays, which is adverse for aseismatic design.
出处
《岩土工程学报》
EI
CAS
CSCD
北大核心
2012年第10期1903-1909,共7页
Chinese Journal of Geotechnical Engineering
基金
国家杰出青年基金项目(51025827)
国家自然科学基金项目(50979096
50808145)
973项目(2011CB411907)
浙江省自然科学基金项目(R1080819
Y1090105)
浙江省科技计划项目(2010C33182)
关键词
地震
动三轴
变围压
循环荷载
earthquake
cyclic triaxial test
cyclic confining pressure
cyclic loading
