Method Of Identification Mechanical Parameters Of Loess With Interface Based On Micro Variable Angle Cone Penetration In Hole

The natural interface and artificial interface in loess are often prone to form potential failure surfaces due to strong permeability and insufficient compaction,which control the mechanical properties of loess.Accurately obtaining the in-situ interface mechanical parameters of soil is the key to ensuring the smooth development of engineering activities in loess areas.This article studies the influence of interface on soil mechanical parameters by developing an adaptive micro variable angle cone penetration test device in the hole,combined with on-site investigation,indoor experiments,numerical simulation,and other means,and innovates the technical method for identifying in-situ mechanical parameters of deep soil interface.The specific research content and conclusions are as follows:(1)A set of hole adaptive micro variable angle cone penetration device was developed.This device mainly consists of a fixed system unit,a rotating system unit,a penetration system unit,and a control and acquisition system unit.The four units work together to complete the penetration process.The rapid acquisition of shear strength parameters of loess with interface is realized,and the testing function of static sounding technology is enriched.(2)The manifestation of interface effect in loess has been explored.Based on the field investigation and laboratory test of loess with interface,the influence law of interface on shear failure form and process of soil is clarified,the influence degree of interface on shear strength parameters of soil is quantified,and the change law of mechanical properties of loess with interface under different test conditions is clarified.(3)A method for identifying mechanical parameters of loess with interface by a micro variable angle cone penetration test device is proposed.A large number of model tests have been carried out through the self-developed multifunctional ground pressure simulation model box and in-hole cone penetration test device.The changing process of tip resistance is explored,the peak tip resistance is extracted,and its changing trend with dry density and moisture content is analyzed.The empirical relationship between the shear strength parameters of soil with and without interface and the factors such as peak cone resistance,water content and normal stress is established.(4)The penetration mechanism of micro cone penetration in loess with interface is revealed.Based on finite element software ABAQUS,coupled Euler-Lagrange analysis(CEL)is used to clarify the response of stress field in loess with interface during cone penetration,and the correlation and unity between cone penetration process and shear process of soil are found.