Functional Anaylses Of Geofabric And Its Applied Technology In Flood Control Construction Of Yongding River

Through the tests and experiences on the Yongding river,the paper infers following conclusions:The National Standards and Design Code issued by the Ministry of Water Resources are widely used under the condition of static load and mono-direction flow. However,followings should be paid more attention:First,while clay grains is more than 50%,O95 or Oe < 0.21 mm;while d85<0.074 mm,geotechnical fabric is not appropriate for filter.Second,while infiltration,the piping is normally happened in non-clay or less-clay soil when Cu<2 or Cu>6,esp. uniformed fine sand. If appropriate geotechnical fabric is difficult to be used,a layer of sand may be laid between the fabric and protected soil in order to solve the uneven soil and to improve the filtration effects. Sometimes,sand is laid on the geotechnical fabric from the moving of stone blocks and puncturing of the fabric. The above measurements must be adopted on the realsituations.Third according to the practice,over 300 g/m2 of the staple nonwoven geotechnical fabric is used in the bank project of the large rivers,its tensile strength is 600 N/5cm.Forth the filtration under the traffic load,normally,the traffic load is repeated load and fast movement. In this case,thick filtration is applied,such as sand and/or thick fabric,of which weight is over 700 g/m2. If porosity of the geotechnical fabric is 90%,the thickness of PP must over 8 mm,of polyester must 5 mm..The paper has analysed the function of geotechnical fabric.