The Research On The Law Of Soil Nails & Soil Anchors Of Deep Excavtion Engineerings

With the high-speed development of the urban construction,alarge number of high and extra-high buildings and municipal engineering are beeing built,and the scale of the building is expanding constantly too. The deep foundation pit of the skyscraper is usually built in the intensive buildings of the city. Narrow in its place , it is unprecedented that the degree of difficulty of construction technology is great.The deep foundation pit is a highly difficult geotechnical engineering subject. The status quo of deep excavation in our country lies in:the depth is deeper and deeper,the engineering geological condition worse and worse,the adjacent building nearer and nearer.and the bracing cost higer and higer.As two methods of Active Bracing,soil-nailed bracing and soil-anchored bracing are becoming popular because of their higer efficiency and low cost.In this paper,history and development of the soil nail and soil anchor support is simply described,the action mechanism and stability analysis method of soil nail support as well as its problem is summed up.Soil nailing system is a soil support system,composed of reinforcing steel bars approximately horizontally placed in slope and faceplate,and it is a kind of in situation reinforcement techniques.By stress sharing,stress transmission and diffcusion,and displacement restriction, compoiste soil nailing system can improve the strength and rigidity of soil and decrease the deformation and failure state by enhancing the whole stability of slope.Soil-nailed and soil-anchored model tests in six groups are carried out to simulate the real excavating and bracing process.Through these tests,the follwing topics are disscussedrunder different condition of the stratum,the resonable arrangement way of the soil nail and soil anchor;the force law of soil nail,and the field of displacement under the changes of surcharge position in the soil-nailed struction;the rule of vertical soil nail;the force law and the field of displacement,stain and stress of nail-anchored bracing struction which contains two conditions: upper-nailed and lower-anchored bracing,and middle-anchored and upper and lower nailed bracing.