论岩土材料屈服准则的基本特性和创新

从岩土材料的基本力学性能出发,讨论岩土材料屈服准则的基本特性和屈服准则的创新。根据国内外学者的大量实验结果,岩土材料屈服准则的基本特性为:拉压异性(SD)效应、正应力效应、静水应力效应、中间主应力效应、中间主剪应力效应、双剪应力正应力效应、双剪应力围压效应、应力角效应(应力偏张量第三不变量效应)和屈服面的外凸性。屈服准则应该满足这些基本特性,Tresca准则不符合这些条件,Mohr-Coulomb理论只能够满足部分条件,Drucker-Prager准则不能满足应力角效应。屈服准则的创新应该满足科学创新的3个要素:(1)新,前所未有;(2)比原来的准则更好;(3)能够实施、便于实际应用。总结各种力学单元体模型的发展,并以一个新的力学模型为依据,对统一强度理论补充一个拉伸破坏条件,它类似于Mohr-Coulomb准则的拉伸截断。从而将统一强度理论扩展到三向拉伸区,更能适用于岩土材料和岩土工程,也使统一强度理论在理论上更趋完整。

Study on the applicability of frequency spectrum of micro-tremor and dynamic characteristics of surface ground in Asia area

The dynamic characteristics of ground soil using micro-tremor observation in Asia (Zushi and Ogasawara (Japan), Xi’an (China), Manila (Philippines), and Gujarat (India)) are studied. Ground micro-tremor signals were observed and analyzed by fast Fourier transform method (FFT). The response of ground soil to frequency of ground micro-tremor is revealed, and func- tions with frequency-dependence and frequency-selection of micro-tremor for different foundation soil strata are also researched. The horizontal to vertical spectral ratio (H/V, Nakamura technique) of micro-tremor observed at the surface ground was used to evaluate the site’s predominant period. This paper also discusses the application of micro-tremor on site safety evaluation, and gives the observed calculation results obtained at multiple points. The experimental foundation and the deduction process of the method are described in detail. Some problems of the method are pointed out. Potential use of the technique’s good expandable nature makes it a useable means for preventing and reducing disaster’s harmful effects.