Characteristics of engineering geology and liquified soil layer of the Bianqiao School liquefaction zone

Liquefaction is one of the most popular secondary geological disasters in an earthquake. Phenomenon of sand liquefaction was found in the Deyang area in the Wenchuan earthquake. The liquefactioninduced disaster investigation and geotechnical engineering drilling and tests were conducted for the Banqiao School liquefaction zone in order to understand the characteristics of engineering geology. The results indicate that (1) Characteristics of liquefactioninduced disaster was typical, including sand boiling, ground fissure and sidesway, foundation settlement. (2) Gravelly sand, which was divided into the Holocene sediment and the Pleistocene sediment, was the only cohesionless soil which had potential to liquefy in liquefaction size. (3) Real liquefaction soil is gravelly sand layer which is the unconsolidated Holocene sediment. Its graduation is poor. (4) The thicker nonliquefaction cover coat has filtering effect so that the small particles such as sand grains is easy to eject out of ground from fissures and, by comparison, the coarse particles such as gravel particles is difficult to spray.