Study On Deformation Characteristics Of Expansive Soil Foundation Improved By Gravel

Expansive soil is widely distributed in China,which is featured by some special engineering properties such as water swelling,water loss shrinkage,repeated expand-shrink deformation,over consolidation,and multiple fissures.Under the repeated expansion and shrinkage and load,the deformation of expansive soil foundation is very obvious,which will adversely affect the safety,stability and function of the project.Therefore,it is very important to study the improvement of expansive soil and its deformation characteristics.Combining macroscopic and mesoscopic,this thesis studies characteristics of the foundation deformation of expansive soil improved by gravel by means of indoor experiment and numerical simulation based on the improvement of the foundation of a power plant in southern Shaanxi.The major procedures and conclusions of this thesis are as follow:(1)Analysis about deformation characteristics and numerical simulation of expansive soil both at home and abroad are explored.Based on relative theories about the application of PFC2D software of discrete element numerical simulation,simulate mesoscopic parameters are determined according to the data of indoor test and materials about engineering,meanwhile,numerical simulation model is established about the foundation deformation of expansive soil improved by gravel.(2)The optimal water content of the expansive soil is reduced and the maximum dry density of the expansive soil is increased after adding the gravel in the expansive soil.The change of swell capacity with different gravel concentration is regular in different periods of time in the experiment of free expansion rate of the improved gravel expansive soil.According to the effect of expansibility of the foundation deformation of expansive soil improved by gravel,with the increase rate of the gravel,the reduction of both free expansion rate and linear swelling rate of the foundation deformation of expansive soil improved by gravel appeared a certain regularity.(3)Simulation verification of the indoor test is conducted about the expansive soil improved by gravel based on the PFC2D software,which proved the consistency between the numerical simulation results of the expansive soil foundation and the trend of the experimental results.Meanwhile,the foundation deformation of expansive soil improved by gravel under different gravel content was simulated and analyzed.It was found that with the increase of the gravel content,the decrease of the deformation of expansion and settlement deformation of expansive soil improved by gravel appeared a certain regularity.Also,the optimum mixture rate and the effect of improvement is determined about the foundation deformation of expansive soil improved by gravel.(4)Parameters of the numerical simulation of different gravel friction coefficient,gravel grain stiffness and gravel maximum particle size are used to simulate the expansion deformation and settlement deformation of the expansive soil improved by gravel in virtue of PFC2D software.The effect rule and the effect of the improvement of different numerical simulation parameters on the foundation deformation of expansive soil improved by gravel is explored,which proved that the deformation of expansion and settlement deformation of expansive soil improved by gravel in inverse proportion to the friction coefficient and the grain stiffness of the gravel particles.Furthermore,the characteristics of the foundation deformation of expansive soil improved by gravel under different numerical simulation parameters is determined.(5)The settlement data are obtained by field monitoring,and the simulation results are compared with the simulation results.