【摘要】 通过汶川8.0级地震液化震害调查以及对工程地质条件和土层剖面的分析,给出此次地震砂砾土液化的分布和规模,并通过典型液化场地现场测试和室内试验,获取了地表喷出物与实际液化土类的关系以及液化砂砾土土性特征。分析结果表明,此次地震砂砾土液化真实存在且占主导地位,为此次地震全部液化点的80%～85%。成都地区和德阳地区的液化土层基本上均为砂砾土,分布在5个条形区域,约占此次地震液化总数的75%。绵阳地区地层不均匀性较强,液化土类为砂土、砂砾土混合型,其中砂砾土液化占到该地区液化点的1/3～2/3,约占此次地震液化总数的5%～10%。此次地震中粉砂、细砂占地表喷出物半数以上的现象只是一种表象,地表喷出物与地下实际液化土层的成分差异显著。典型液化场地勘察测试表明,液化场地地层总体较为简单,层序结构基本一致。液化土层中颗粒级配曲线总体平缓,光滑程度差,不均匀系数较大,曲率系数较小,粒径跨度大且存在粒组缺失现象,各场地级配形态差别显著。现有标准贯入试验在砂砾场地上不可行,建议采用超重型动力触探试验,同时现有基于砂土的剪切波速液化判别方法对砂砾土不适用,需另行考虑。更多还原

【Abstract】 A distribution map is compiled of gravelly soils that liquefied during the 2008 Wenchuan,China Earthquake(Ms=8.0).The map is based on detailed field investigations and analysis of geological soil profiles.The geology is summarized on geological cross sections and borehole logs.Four typical liquefied sites were selected for drilling to collect soil samples,sounding to determine dynamic penetration(DPT)resistance,and measurement of shear wave velocities with SASW tests.From the field investigation,118 liquefied sites were identified and surface effects documented shortly after the earthquake.This investigation showed:①that sandboils indicative of liquefaction occurred extensively across hundreds of square kilometers of farmland,in 120 villages,and beneath 8 schools and 5 factories;②that ground fissures and ground displacements damaged some rural houses,school buildings,and manufacturing plants.In addition several wells malfunctioned primarily due to clogging with boiled up sand and gravel;③that the Chengdu plain is underlain by gravelly soils with thicknesses ranging from 0m to 541m and that looser layers within these gravel beds are the materials that liquefied;④that the observed liquefaction features developed in five long narrow zones across the plain which vary from 20km to 40km in length;⑤that these zones are underlain by fluvial and alluvial gravelly sediments deposited by ancient rivers;⑥that mean grain sizes of soil samples taken from the gravels that liquefied range from 1 mm to 30 mm;⑦that grain sizes of the sampled soils were generally larger than those from samples of overlying ejected in sand boil deposits;⑧thus subsurface layers of liquefied soil could not be directly correlated with the ejected soils.The compiled information enrichs the global database for gravelly soils that have liquefied and provides a database for development of improved methods for evaluating liquefaction resistance of gravelly soils.更多还原