Study On Dynamic Characteristics Of Residual Laterite In Basalt ?P₂e? And Sand Shale ????₂d? Of Kunming Changshui International Airport

As a special type of clay,the complex engineering characteristics of laterite has attached more and more attentions.Kunming Changshui International Airport is located in a typical laterite karst area,with various types of laterites distributed widely within the airport site and surrounding mountainous area.It has a significant impact on the safety and stability of various types of buildings at the airport,and especially leads to frequent seismic activities within the Xiaojiang seismic active fault zone and the Pudu River seismic active fault zone,making the research area remain a unstable state.Therefore,it is of significant necessity to study the engineering geoloical properties and dynamic characteristics of laterite.This paper uses TAJ-20 microcomputer controlled electro-hydraulic servo soil dynamic triaxial testing machine to test the dynamic characteristics of basalt residual laterite?P₂e?and sandy shale residual laterite????₂d?in Kunming Changshui International Airport,to explore their dynamic characteristics of two kinds of residual laterites under cyclic loading,mainly concerning impacts of confining pressure,consolidated ratio and moisture content on the dynamic deformation characteristics and dynamic strength characteristics of the two types of residual laterites.Additionally,the comparative analysis on the dynamics characteristics of these two types of laterites and the analysis on the failure mechanism of laterite samples are also conducted.Finally,through the dynamic triaxial test,the dynamic characteristics of the residual laterite in Kunming Changshui International Airport were simulated by MIDAS GTS geotechnical numerical analysis software for the aseismatic simulation of the typical underground structures under two kinds of residual laterite layers.The obtained research results are of a great significance and practical value for evaluating the aseismic safety ans stability of housing construction foundations and underground structures in urban cities and rural towns distributed with laterites.Research on Dynamic Deformation Characteristics:Under dynamic loading,the impacts of consolidation stress,consolidation ratio and moisture content on dynamic stress-strain curve,dynamic shear modulus and damping ratio of basalt residual laterites?P₂e?and sandy shale residual????₂d?laterites are explored.It is concluded that the dynamic stress-strain curves,the G_d^?_d relationship curves and the?-?_d relationships of the basalt residual?P₂e?laterite and the sandy shale residual????₂d?laterite are basically the same.The main difference is that under the same dynamic strain,the sandy shale residual????₂d?laterite requires more dynamic stress than the basalt residual?P₂e?laterite and produce larger dynamic shear modulus while the damping ratio stays similar.Research on dynamic strength characteristics:The effects of consolidation stress,consolidation ratio and moisture content on the dynamic law of dynamic strength characteristics of basalt residual?P₂e?laterite and sandy shale????₂d?laterite in Kunming Changshui International Airport were investigated.The test shows that the dynamic cohesive force of both residual laterites is significantly smaller than the static cohesive force,and the internal friction angle is slightly larger than the static internal friction angle.With the same destructive vibration for both the basalt residual?P₂e?laterite and the sandy shale residual????₂d?laterite,the dynamic stress decreases with the increase of the consolidation ratio.When the moisture content is appropriately reduced relative to the optimum condition,the dynamic cohesive force of the basalt residual?P₂e?laterite will also decrease,and the dynamic friction angle will increase.However,when the moisture content is too high relative to the optimum moisture content,the basalt residual?P₂e?laterite will become soft and close to the nature of the soft clay.When the moisture content is appropriately reduced relative to the optimum condition,the dynamic cohesion of the sandy shale residual????₂d?laterite will also increase,and the dynamic friction angle will decrease slightly.However,when the moisture content is too low,the sample of sandy shale residual????₂d?laterite is too loose,similar to the nature of sand,and the ideal dynamic strength test results cannot be obtained.Aseismic simulation study of the underground structure of laterite layer:Through the previous research results on the dynamic characteristics of two kinds of residual laterites in Kunming Changshui International Airport,using MIDAS GTS finite element software and the reaction acceleration method,the deformations of the underground structure of the laterite layer under seismic wave vibration of level 8 is simulated to evaluate the safety and stability of the underground structure with the residual laterites at the Kunming Changshui Internatonal Aiport.The analysis shows that under the earthquake load,the relative displacements at the peak levels of basalt residual?P₂e?laterite and sandy shale residual????₂d?laterite in the airport increase as the buried depth of the clay layer decreasing,reaching their maximums of 11.2cm and 33.8cm,respectively,at the earth surface.And the relative movements between the underground structure and the surrounding soil is consistent,as well the underground structure has occurred.