Study On The Selection Of Similar Materials And Physical Model Experiment In The Model Experiment Of Karst Pile Foundation

Karst is one of the common unfavorable geology in pile foundation engineering construction.The implementation of pile foundation engineering in the complex karst area greatly increases the design difficulty of pile foundation.When designing pile foundation,the existence of karst cave in the foundation will also affect the quality and safety of engineering construction.Therefore,in this paper,the karst pile foundation model test method is used to study the karst pile foundation,in order to provide a high credibility reference for the actual project.The specific research contents are as follows:First of all,the similarity ratio of physical quantities between the model and the prototype is obtained from the similarity theory.The geometric similarity ratio is 30 and the density similarity ratio is 1.5.Then the similarity coefficients of other physical quantities are deduced according to the relation of main physical quantities.At the same time,the target value of each parameter of the model is converted according to each parameter of the prototype,which provides a theoretical basis for the selection of similar materials in the next step.Secondly,on the basis of previous research,sand,gypsum,cement,diatomite,red clay,limestone powder and other materials are used,and experimental schemes for selecting similar materials are formulated,45 groups of mix ratios are designed,uniaxial compression test and direct shear test are carried out,with saturated uniaxial compressive strength and density as control index,elastic modulus,cohesion and internal friction angle as reference indexes.Three groups of best mix ratios are determined to simulate three different degrees of weathering limestone.Then,the exploration data of a project are collected and sorted out to extract the basic physical quantity information of each rock stratum.Based on the analysis of the experimental results,the change characteristics of karst foundation under the action of pile load are obtained.Finally,Midas GTS finite element software is used to analyze and verify the simulation conditions,the model experimental parameters are transformed into prototype parameters by similarity coefficient,and the prototype calculation results are obtained.Through the conversion of similarity coefficient,it is concluded that the similarity ratio of displacement and strain is 1.The settlement data of pile foundation and the strain data of karst cave surrounding rock are extracted,and the experimental data of model experiment are compared intuitively,and the effect of model experiment is verified,which provides reference for the next experimental improvement.