循环荷载作用下软土地基强度弱化模型研究

Research on the strength degradation model of soft foundation under cyclic loading

随着大规模港口建设的发展,港工结构物大多处在波流荷载和软弱地基等复杂的环境条件下,而循环荷载作用下软黏土地基强度弱化将影响到上部结构物的安全性。采用双曲线型孔压模型对软土动三轴试验数据进行拟合,将拟合得到的孔压模型与等效超固结理论相结合,建立能够反映围压、静偏应力、动应力和循环周次影响的软黏土不排水抗剪强度弱化模型,并确定循环荷载作用下软黏土不排水剪切强度折减系数β。基于FISH语言对有限差分程序FLAC;进行二次开发,数值实现考虑循环荷载作用下软黏土强度弱化效应的动力分析模型,并与动三轴试验结果进行对比,验证了采用该模型描述循环荷载作用下软土地基弱化的可行性。研究成果可为近海工程结构物的设计和安全评估提供科学依据。

With the development of the large-scale port construction, the structures in Port Engineering faces the complex environment conditions such as wave, current load and weak foundation. However, under the cyclic loading, the strength of soft clay foundation degradation thus threatens the stability of superstructure. In this study, a hyperbolic pore pressure model was adopted to fit the cyclic triaxial test results, based on which the undrained strength degradation model of soft clay was established with the equivalent over-consolidation theory.The proposed undrained strength degradation model includes the effect of confining pressure, static deviator stress, dynamic stress and cycle numbers on the development of pore pressure, which calculated cyclic degradation coefficients β. By virtue of secondary development of FLAC;based on FISH language, the undrained strength degradation model was numerically implemented. The reasonably good match between the numerical results and the test data verifies the applicability of the model in describing the characteristics of the soft foundation under cyclic loading. The achievement can provide scientific basis for the design and security assessment of the offshore structures.