边坡地震稳定性分析的荷载增强分析方法

LOAD INCREASING METHOD FOR EARTHQUAKE STABILITY ANALYSIS OF SLOPES

岩土边坡地震稳定性分析是岩土工程和地震工程研究的重要课题之一,本文明确区别了两种不同意义的边坡地震稳定性概念:一是按一定的抗震设防地震作用考虑,边坡现状强度与边坡强度退化到发生地震破坏时的临界强度相比较而言的储备强度稳定性;二是对于一定的边坡强度状态,使边坡发生动力破坏的地震作用与设防地震作用相比较而言的地震动力超载稳定性。考虑边坡强度退化的边坡稳定性概念已经得到普遍采用,分析方法较为熟知;而按动力超载考虑的边坡地震稳定性概念以往几乎没有提及,边坡稳定性判别标准和分析方法尚有待探讨。本文主要针对第二种边坡地震稳定性——地震动力超载稳定性的衡量标准和分析方法进行了研究,提出了边坡地震动力超载稳定性评判的临界地震峰值加速度准则,并提出了边坡地震动力超载稳定性分析的荷载增强法:针对边坡的现状强度状态,由小到大逐渐增加地震作用的强度,搜索导致边坡失稳的临界地震峰值加速度,最后根据边坡临界地震峰值加速度与边坡所在区域的设防地震峰值加速度比较情况确定边坡的地震稳定性。论文采用荷载增强法对中国陕西宝鸡蟠龙塬黄土边坡地震动力超载稳定性进行了分析。结果表明,针对宝鸡地区未来50a超越概率为10%的地震动作用,该边坡具有较高的地震动力超载稳定性。

The analysis of earthquake stability of slopes is one of the most important research subjects in geotechni cal engineering and earthquake engineering. Two different concepts of slope earthquake stability are put forward in this paper. One concept is the socalled strength reserve stability which can be figured out by comparison of present strength of a slope to its. critical strength that is degenerated from its present strength till to the dynamic failure of the slope under the earthquake action of a certain intensity. The other is named as the dynamic overloading stability which can be evaluated by contrast between the actual earthquake action that just makes a slope damaged and the earthquake action as the local antiseismic precautionary standard. The first concept of slope earthquake stability has been widely accepted. Its relative analysis methods are also well developed. The second one, however, is seldom mentioned till now. Its failure criterion and analysis method are yet to be explored. This paper investigates the fail ure criterion and the analysis method of dynamic overloading earthquake stability. The criteria of the critical earthquake peak acceleration for the dynamic overloading stability of a slope and its analysis method, and the load in creasing method are put forward. During the analysis process, the action of earthquake force begins from a lower level and gradually increases to the critical intensity that just makes the current strength slope reach the state of dy namic failure. The earthquake stability of the slope is determined by the comparison of the critical earthquake peak acceleration and the antiseismic precautionary earthquake peak acceleration on the field of the slope. The dynamic overloading earthquake stability of a loess slope at Panlongyuan in Baoji, Shaanxi Province, China is analyzed with the load increasing method proposed in this paper. The analysis result reveals that the dynamic overloading earth quake stability of the slope is quite high to the action of the earthquake ground motion with exceeding probability 10% in coming 50 years.