Exploration for Quaternary shallow biogenic gas by sealed core drilling and modified CPT

Quaternary shallow biogenic gas has been found in the course of metro project exploration in the Yangtze River Delta cities(such as Shanghai、Hangzhou、Ningbo、Suzhou).In view of the damage of Quaternary shallow gas for metro construction,appropriate means should be selected in order to get pure core and find out the characters of Quaternary shallow biogenic gas,such as distribution range,composition,source layer and storage layer,burial depth,occurrence regularity and pressure value,so as to provide detailed information of Quaternary shallow gas for the metro construction.In this thesis the author analyzes and compares the methods of earthquake,sealed core drilling,modified CPT for exploration of Quaternary shallow biogenic gas.And the application results in Hangzhou metro project were given.(1)S-wave seismic method was used to determine the distribution of the harmful gas;(2)Sealed core drilling was used to identify occurrence regularity of the harmful gas;(3)Modified-CPT was used to identify composition,source layer and storage layer,burial depth,and pressure value of the harmful gas.The integrated application of three methods not only reach the purpose of investigation of harmful gas in Hangzhou metro project,but also reduce costs and achieve better engineering effect.