Mechanical Response And Microstructure Analysis Of Structural Clay Under Impact Loading

Zhanjiang clay is famous for its strong structure.With the increase of engineering construction projects in Zhanjiang area,it is necessary to further study the physical and mechanical properties of zhanjiang structural clay.In this thesis,the physical and mechanical indexes and distribution characteristics of structural clays in Zhanjiang were obtained by laboratory tests and microscopic tests.The internal relationship between dynamic response characteristics and physical and mechanical properties of structural clays in Zhanjiang is analyzed,which can provide some reference for engineering construction in Zhanjiang area.The main research work is as follows:（1）Study on the statistical relationship between conventional geotechnical tests and physical and mechanical indexes of zhanjiang structural clay.First,conventional geotechnical tests were carried out on zhanjiang remolded clay and undisturbed clay to analyze the effect of structure on its physical and mechanical properties,and to compare and analyze the differences of physical and mechanical properties between zhanjiang special structural clay and other clay regions.The relationship between physical and mechanical indexes of zhanjiang clay is obtained through mathematical statistics analysis.The results show that under the same water content,the mechanical properties of zhanjiang clay are obviously better than those of other regions,and the dimensionless ratio of mechanical indexes to physical parameters of zhanjiang clay is 1.2～2 times that of normal soil.The strength of soil structure and pore ratio are not the main factors affecting the permeability of zhanjiang clay,but the main factor leading to the low permeability of zhanjiang structural clay is the large proportion of clay minerals such as montmorillonite and illite in the soil.（2）Dynamic response characteristics of Zhanjiang structural clay under impact load.Spax-2000 improved static and dynamic true triaxial test system was used to simulate static and dynamic drainage and consolidation,and the dynamic mechanical response characteristics and deformation characteristics of zhanjiang special structural clay under impact load were analyzed.The results of triaxial shear test were used to analyze the drainage consolidation effect under different medium principal stress,consolidation confining pressure and impact load frequency,which is a reference for the application of static and dynamic drainage consolidation method in Zhanjiang area.The results show that the shear strength increases more than that under different shear rates.At the moment of each impact load,the sample will produce different sizes of negative pressure,and with the increase of impact load,the negative pore water pressure is more and more large,and the increase amplitude is smaller and smaller.（3）Microstructure evolution characteristics of zhanjiang structural clay under impact loading.The samples before and after the true triaxial shear test were tested by scanning electron microscopy（SEM）,and the SEM images of zhanjiang structural clay were obtained.The SEM images were preprocessed by Matlab software to obtain the microstructure parameters and analyze the microstructure characteristics of structural clay before and after the triaxial shear test.At the same time,the strong structural causes of soil in Zhanjiang area are analyzed from the aspects of mineral composition,geological evolution and microstructure.The results show that the internal pores of the sample without impact load are less after shearing,the flake structure is almost completely extruded,and the internal particle contact is basically surface to surface contact,and the internal layer of the sample after shearing is obvious after impact load.Zhanjiang clay exhibits good mechanical properties due to fewer overhead pores,more contact points and lamellar structure of basic units.