黄土震陷研究及相关问题探讨

Review and discussion on seismic subsidence of loess

回顾了30多年来关于黄土震陷的研究工作和成果。黄土震陷已为微结构特征、动三轴和现场爆破试验所证实,成为黄土地震工程研究领域的一项重要课题,但仍缺少典型震例,且停留在饱和土理论研究阶段。应用微结构形态学方法表征土体结构性变得困难,土力学方法将是微结构应用于震陷性研究的有效途径。震陷性判定仅是在多个参变量值区间内的确定性判定,概率性震陷预测应得到开展。震陷系数估算多是基于室内试验数据的经验公式或半经验半理论公式,并未完全解决其物理过程和力学机制问题,比如参变量多、计算繁琐和实用性差等,故应从黄土震陷的物理力学机制出发,厘清影响黄土震陷的主导因素及其表征参变量,建立具有物理力学意义的数学理论估算模型。抗震陷处理技术的关键是消除土体的震陷性,并减缓震陷时土与土工结构物的相互作用。

The research works and achievements of seismic subsidence of loess, obtained over the past 30 years, were reviewed. Seismic subsidence of loess has been verified by microstructure characteristics, dynamic triaxial experiments, and in-site explosion test, and has been an important project in the research field of seismic loess engineering. However, the research remains on saturated soil theory, and there are no typical case studies of seismic subsidence of loess in historical earthquakes. It is difficult to express structure characteristic using microstructure morphology, therefore, soil mechanics is an available method for this. The seismic subsidence judgment is just absolute in some certain value ranges for several parameters, therefore, probability judgment should be developed. Seismic subsidence ratio is estimated to empirical formulas or semiempirical and semitheoretical formulas, which are on the basis of laboratory test data. These formulas are not established on the physical process and mechanics of seismic subsidence, leading to much more variables, complicated computation, and bad application. To solve these problems, it needs to distinguish main factors and corresponding variables firstly, and to establish mechanic model of seismic subsidence estimation, which can reflect physics and mechanic. The key of anti-seismic subsidence technology is to relieve seismic subsidence of soil body, and to lower the interreaction between soil body and underground structures.