边坡地震动力响应特性及失稳临界加速度研究

The problem studied in this propsal is about slope stability owing to earthquake actions, a hot research point in engineering gelology and engineering seismology. In this proposal, traditional concept of slope stability based on the judgement of inner force of slopes is exceeded by the concept of dynamic overloading earthquake stability of slopes, and loading increasing method to search the critical earthquake action of a slope is put forward. According to the new concept, a systematic evaluation method for slope earthquake stability based on the comparison between the critical earthquake intensity which causes slope failure and the regional seismic precautionary criterion of earthquake intensity is to be developed. The main research contents in this project include: (1) natural vibration characteristics of a slope; (2) characteristics of dynamic response of the slope to earthquake actions and critical state of slope earthquake failure; (3) criterion of earthquake action for slope earthquake stability; (4) Probability of earthquake failure hazard of the slope and its evaluation method. The key problems in the study are as follows: (1) dynamic constitutive relationship of rock or soil mass in a slope and its matching with the intensity of earthquake action; (2) the influence of variation in characteristics of earthquake loadings such as incident direction of seismic waves, acting direction, frequency and duration of seismic forces on the dynamic response of a certain slope; (3) relationship between dynamic failure of rock or soil mass and the slope failure as a whole. Typical loess slopes in high seismic intensity area of Tianshui City in Gansu Province will be taken as study objects in this proposal with methods of multiple scientific fields: the characteristics of earthquake action is going to be studied by the method of focal mechanism (fault-plane solution) and the probabilistic analysis of seismic hazard; regional engineering geological conditions and properties of slopes can be investigated with engineering geology analyses and investigation of geotechnical engineering; the characteristics of natural vibration, dynamic respose and dynamic failure of a slope are to be researched with combination method of ground tremor measurement in titu and numerical simulation; the reliability of the analytical methods is going to be verified by comparison between actual slope failure events and the analytical outcomes. As the result, a set of analytical methods for seismic stability of slope with the criterion of seismic parameters will be put forward so as to realize the assessment of seismic failure modes of slopes and their occurrence probabilities.

本项目拟围绕当前工程地质和工程地震学研究的热点之一-地震作用下的边坡稳定性问题展开研究，突破传统边坡稳定性观念，提出边坡地震动力超载稳定性的概念和以边坡失稳临界地震峰值加速度搜索为核心的动力荷载增强法，并以此为基础展开边坡地震动力超载稳定评价方法研究，将传统的内部抗力与地震动力的比较外化为边坡地震失稳临界加速度与区域设防地震加速度的比较。项目研究内容主要包括：（1）边坡自振特性研究；（2）边坡地震动力响应特性及地震失稳临界状态研究；（3）边坡地震稳定性地震强度判据研究；（4）边坡地震破坏失稳危险概率分析及估算方法研究。项目拟结合甘肃天水市高地震烈度区的典型黄土斜坡实例展开研究，揭示边坡自振特性与边坡地震动力破坏失稳方式的联系，建立以地震参数为准则的边坡地震动力稳定性分析评价体系，实现边坡地震动力失稳破坏方式及其发生概率的分析评价。

本项目围绕当前工程地质和工程地震学研究的热点之——地震作用下的边坡稳定性问题展开研究，针对“未来一定时期内，特定边坡发生一定方式地震破坏的危险性有多大”这一科学问题，突破着眼于边坡体抗力与内力平衡的传统边坡稳定性观念，提出边坡地震动力超载稳定性和临界地震加速度的概念以及以边坡失稳临界地震峰值加速度搜索为核心的动力荷载增强法，并以此为基础展开边坡地震动力超载稳定评价方法研究，将传统的内部抗力与地震动应力的比较外化为边坡地震失稳临界加速度与区域设防地震加速度的比较。项目研究内容主要包括：（1）岩土边坡地震稳定性地震强度判据；（2）地震动力作用方式对岩土边坡地震动力响应的影响；（3）坡体物性参数变化对边坡地震响应影响的敏感性；（4）考虑潜在震源方位的地震危险性分析方法；（5）边坡对弱震和强震作用的动力响应特征的对比；（6）边坡地震失稳危险概率评价模型；（7）震源辐射场与边坡受到的地震动力作用。其中，前5个方面的研究成果揭示了地震动力作用方式变化和边坡自身条件对边坡地震动力响应的影响,形成了以边坡地震破坏失稳临界地震峰值加速度与区域设防地震峰值加速度比较为基础的岩土边坡地震动力稳定性评价标准和方法。在前5项研究的基础上，按照概率论和不确定度分析的相关理论，考虑潜在地震作用和边坡性状两方面不确定性的影响，构建了边坡地震失稳危险概率评价模型，并结合陕西省宝鸡市蟠龙塬边坡进行了实例研究，得出了该边坡各方向上的地震失稳危险概率和场地50年超越概率10%的边坡地震稳定性系数（含不确定度）。.上述研究成果实现了本项目的各项计划研究目标，定量回答了本课题提出的 “未来一定时期内，特定边坡发生一定方式地震失稳破坏的危险性有多大”这一科学问题，为边坡地震灾害概率评价提供了关键理论方法，同时，也可以为其他类型的地质灾害危险性的定量评价提供借鉴和参考。