Newmark模型的修正以及地震触发崩塌滑坡危险性区划方法研究

Improvement of Newmark Model and Method Study of Risk Zoning for Earthquake Triggered Landslide

大量实震资料表明,地震触发崩塌滑坡是造成道路工程损毁的主要原因。以Newmark滑块模型为理论基础的Jibson边坡永久位移预测公式,是目前唯一可以从坡体变形损伤微观指标和坡体整体破坏概率来评价地震触发崩塌滑坡危险性的方法。经"5·12"汶川地震实震资料检验,Jibson方法计算值小于坡体实测位移值,理论分析发现,滑块模型未考虑滑动面抗剪强度在地震作用过程中的衰减效应,是导致计算值偏小的主要原因。鉴于此,通过对滑动面岩土体的有效内摩擦角和有效黏聚力添加衰减系数的方法,修正Newmark滑块模型;在此基础上,参考Jibson边坡失稳概率模型的方法框架,利用汶川地震实震资料,建立了以面密度为区划指标的地震触发崩塌滑坡危险性区划判据;并利用"4·20"芦山地震实震资料对区划方法的正确性进行了检验。该方法不仅可预测同震崩塌滑坡的严重程度,而且还包含了反映震后山地灾害孕灾环境变化的信息,可为高烈度地震山区道路选线设计提供科学依据。

A large number of real seismic data show that the earthquake triggered landslides are the main cause of road engineering damage.The permanent displacement prediction formula based on Newmark block model for Jibson slope is currently the only method to evaluate the risk of earthquake triggered landslide from the perspectives of deformation damage and overall failure probability of slope.Verified by seismic data of the'5·12'Wenchuan earthquake,the calculated value of Jibson method was smaller than the field measured displacement.Theoretical analysis showed that this slide model does not consider the shear strength attenuation effect of the sliding surface during the earthquake,leading to a small predicted displacement.In view of this,the Newmark slide model was modified by adding attenuation coefficients to the effective internal friction angle and effective cohesion of the rock mass on the sliding surface.Based on the modification and the method framework of Jibson slope failure probability model,the risk zoning criterion with the surface density as the main indicator was established for earthquake triggered landslide assessment using real earthquake data of Wenchuan earthquake.The modified method was verified by the real earthquake data of the'4·20'Lushan earthquake.The presented method can not only predict the severity of coseismic collapse and landslide,but also contain the development information about the hazard-inducing environment after the earthquake.It can provide a scientific basis for road route selection in high intensity earthquake mountain area.