汶川8.0级地震液化震害及特征

通过现场详细地调查,归纳总结了汶川地震液化导致的工程震害的现象、分布、规律和特征。结果表明,此次地震液化震害现象显著,位于德阳地区的3个液化区域震害严重,都江堰地区、绵阳游仙区以及江油市区的3个液化区域震害中等,其他地区轻微,液化震害分布与液化分布有一定关系,但二者有所不同;液化场地上房屋均不同程度受损,其中结构性差的房屋会直接倒塌,设有圈梁、构造柱的房屋,液化也会导致其整体倾斜、下沉、开裂;学校液化震害具有典型性,部分校区大面积液化,地裂缝纵横,地基不均匀沉降严重,主体结构开裂、倾斜,功能丧失。这次液化震害具有3个显著特征:(1)只要液化出现的地方,震害均比周围重,没有减震现象;(2)Ⅵ度区不仅有液化现象,而且有明显的液化震害;(3)液化伴随地裂缝,是构成此次地震液化震害的主因。

Characteristics of liquefaction-induced damages during Wenchuan Ms 8.0 earthquake

The distribution and characteristics of liquefaction-induced damages during Wenchuan Ms8.0 Earthquake in China were summarized in detail according to the wide and detailed field investigation. The analytical results are as follows. (1) The liquefaction phenomena are evident, involving thousands of Hundreds thousands square meter of farmland. (2) The liquefied sites distribution and the liquefaction-induced damage distribution are correlated but not the same. Comparison of the liquefaction phenomena, the 3 liquefaction-induced damage areas in Deyang are the most serious; Dujiangyan, Mianyang and Jiangyou districts are the secondly serious; and other areas are relatively light. (3) In the liquefied sites, the poor houses without any consideration of seismic resistant design collapsed, even the houses/buildings with collar beams and constructional columns subsided or tilted. (4) The liquefaction phenomena are typically severe in schools, generating ground fissures and causing buildings tilting, subsiding and cracking. Three obvious characteristics of the liquefaction-induced damage are: (i.) The liquefaction aggravates the structural damage and no shock absorption phenomenon has been observed. (ii.) In the regions of seismic intensity of VI (PGA less than 0.05g), liquefaction phenomena and liquefaction-induced damage were observed and quite remarkable. (iii.) The liquefaction generated ground fissures are the significant cause of liquefaction-induced damage.