Evaluation Of The Chinese Dynamic Penetration Test Based Method For Liquefaction Assessment Of Gravelly Soils

Gravel soil has the advantages of good drainage and high strength.It is widely used as building materials for harbor reclamation,expressway,railway,earth-rock dam and slope.During the 2008 Wenchuan M8.0 earthquake,Yuan Xiaoming's team found and identified 118 liquefaction sites,of which about 70% were gravel soil liquefaction,the largest in the world.Since the Greek earthquake in 2014,the Ecuador earthquake in 2016 and the New Zealand earthquake in 2016,serious liquefaction of gravel soil has occurred continuously,which further indicates that gravel soil treatment as non-liquefied soil will have huge potential safety hazards.Therefore,the establishment,development and testing of gravel soil liquefaction assessment methods are of great significance to the seismic design and fortification of construction projects in various countries around the world.There are more than 10 cases of gravel soil liquefaction in other earthquakes around the world,so it is not realistic to establish corresponding evaluation methods.However,a large number of gravel soil liquefaction in Wenchuan earthquake provides a good test site for the establishment of evaluation methods of gravel soil liquefaction based on field test indicators.Dynamic penetration testing is a field testing technology for evaluating the general mechanical properties of gravel soil.It has the advantages of simple equipment,convenient operation and continuous testing.The cost under the same conditions is 1/20~1/30 of the BPT of Beck penetration test in North America.It is the first time that Cao Zhenzhong(2013)established an evaluation method based on the dynamic penetration test results of gravel soil site in Wenchuan earthquake.However,many problems of this method need to be solved urgently:(1)Limited by test conditions and funds,the evaluation method is based on limited basic test data(19 liquefaction sites and 28 non-liquefaction sites).There are still a large number of gravel soil liquefaction sites in Wenchuan earthquake that deserve further study.(2)The evaluation method of liquefaction of gravel soil was established,using China dynamic penetration as the core field test index.Other countries do not have similar hammering system,probe diameter,probe size.The established method of gravel soil liquefaction assessment can not be used directly in other countries,nor can it be tested by using global gravel soil liquefaction data.In view of the above two problems,19 gravel soil sites(14 liquefied sites and 5 non-liquefied sites)in Chengdu Plain of China were selected to carry out field drilling,sampling,dynamic penetration test and hammering energy test,all of which are new test points.The reliability,accuracy and practicability of the evaluation method of gravel soil liquefaction based on dynamic penetration test were tested.The results show that the test of 19 points is successful,which shows that the method has high reliability.After the hammer number of dynamic penetration is corrected by the hammer energy,the Chinese standard dynamic penetration probe and different hammer system are adopted.This method can be applied in different countries or regions,and has the feasibility of international application.