Researches On The Key Excavation And Retaining Techniques For Field Model Experiment Of Hollow Foundation Pits

Model test method is an important way to research and solve the problem of foundation pit engineering.It has been applied comprehensively at home and aboard,which also exerts important effect in scientific research,design and argumentation of engineering.There are still some problems at home and abroad: the study on deep slender typed foundation pits which of smaller size in plane but deep excavation depth has been very little;most of the model tests are completed under quasi two dimensional plane conditions,which cannot fully reflect the pressure and deformation of the foundation pit in three-dimensional space.Field model test have the advantages of indoor model test and field measurement,conclusions are more realistic,which are significant for practical engineering and have more reference value.Field model test was done to study the behaviors of hollow foundation pits.The retaining structure was formed by the construction method of static pressure pile.This paper mainly completed following work:1.The static pressure equipment and its supporting device for foundation pit model pile were designed.The strength and rigidity stability checking of the equipment was carried out.The single pile and row pile pressing technology and operation procedure were verified in the model test.The advantages of device are: good working performance,high safety,easy disassembly and installation,conveniently moved,high efficiency and so on.2.Considering the sectional shape,size,material and cost factors of model pile,PVC pipe was chosen as model pile.Considering the definition of hollow slender foundation pit,operating space and pile spacing,the plane size of foundation pit of outdoor model test was designed.The manufacture and installation method of the waist beam were designed.3.A set of experimental setting was designed to measure earth pressure,horizontal displacement and strain,which feasibility was verified in the test.The test results showed that the test techniques were effective.4.The Construction method of foundation pit dewatering well and observation well was designed.The method of foundation pit dewatering and drainage was designed.The drainage mode was optimized.The foundation pit could be constructed normally.The model test was carried out smoothly by the above research results,good effects were obtained in the process of testing.These research results have a certain reference value for similar model test research.