Study On The Permeability Characteristics Of Gravel Soil And Its Influence On Liquefaction

Before the Wenchuan earthquake in 2008,there were few examples of gravelly soils liquefaction reported at home and abroad.It is usually considered that the permeability of gravelly soils is so better that the excess pore pressure produced in the earthquake is easily dissipate Therefore,the gravelly soils are directly divided into the non-liquefied soil of the engineering discipline.However,in the Wen chuan earthquake,a large gravelly soils liquefaction occurred in the Chengdu plain,and it may be a record that the world's largest gravelly soils liquefaction has been recorded.Overturned the fact that gravel soil non-liquefied of people traditional understanding,In recent years,with the increasing use of artificial gravelly soils.Field investigation shows that most of the gravelly soils field drainage are clogged or the permeability is low.However,gravelly soils permeability characteristics is one of the important factors of gravel soil field drainage conditions.on the other hand,there is no uniform understanding of the influencing factors of gravelly soils permeability characteristics,The results are vary,However,The Study on the influence of gravel soil permeability and establish the gravel soil permeability model,It is important to find out the liquefaction condition and mechanism of gravel soilIn this paper,the typical liquefaction gravel soil in Cheng du plain was used as experimental material.A series of large indoor penetration tests were carried out,Combined with the previous research foundation,establish the gravel soil permeability model.After that,APOLLO calculation program is used to research the influence law of liquefaction of gravel soil under different drainage conditionsThe main contents of this paper are:1.The buried conditions and drainage condition of the gravelly soils liquefaction and non-liquefaction site layer in the Wen chuan earthquake of Cheng du was analyse,including the groundwater level,the depth of the buried gravelly soils layer,the thickness of the overburden cohesive layer,the drainage distance and the drainage thickness of gravelly soils.Qualitative analysis of these factors on the influence of gravel soil liquefaction2.A series of large indoor penetration tests were carried out,Analysis of different grain size distribution,grain size and Void ratio etc factors on the influence law of permeability coefficient,establish the gravel soil permeability calculation model.The calculation model can be expressed as:k=0.125d10 2.3k=1.3(d10e)2.3k=4.34(d102e2Cc/Cu)1.623.Using APOLLO calculation program,Basic calculation parameters obtained on the basis of 1 and 2,The regularity of the drainage condition(the permeability coefficient)and burial conditions(The ratio of Drainage distance)influence on gravelly soils liquefaction was preliminarily studied.draw a conclusion as:1)When the permeability coefficient of gravel soil layer is less than 0.01cm/s,the permeability is low,it is possible for the gravel soil to liquefy.2)When the Drainage distance ratio is less than 0.25,it is possible for the gravel soil to liquefy.