Study On Dynamic Cone Penetration Test And Particle Breakage On Carbonate Granular Soils

Dynamic cone penetration test(DCPT)is a conventional in-situ testing method and especially suitable for the distribution site of carbonate granular soil.However,there is little research on the relationship between the dynamic penetration index(DPI)and the properties of carbonate granular soil.Moreover,there are many kinds of DCPT equipment with different characteristic parameter,which puts forward a challenge for establishing the general expressions of relationship between the DPI and soil properties.Others,the hammering energy of DCPT equipment would lead to the particle breakage of the soil around the cone,which can affect the test result.To study these issues,in this thesis:Taking the basic soil physical property-relative density,as the pointcut.A relationship between the DPI of light dynamic penetrometer(LDP)and the relative density was proposed for the carbonate granular soil,by conducting a series of dynamic cone penetration model and field test.At the same time,a calibration system that can convert the DPI of different DCPT equipment was deduced by dimensional analysis method.Based on this system and the above relationship for LDP,a general relationship between the DPI and relative density of carbonate granular soil was established.Moreover,a series of impact load tests were conducted,for investigating the particle breakage evolution under impact load such as hammering.A formula reflecting the relationship between the relative breakage and the void ratio for carbonate granular soil under impact load was proposed.And a relative breakage index was put forward to quantify the particle breakage by the relative proximity between the current and ultimate fractal dimension.This index takes the ultimate fractal dimension to reflect the ultimate state of particle breakage,thus,it is physical meaning and easy to determine.Furtherly,based on the fractal theory,a PSD "evolution function" for the carbonate uniformly graded sample in breakage state was derived.The non-uniformly graded sample was regarded as the assembly of a series of independent uniformly graded groups.Then the "assembly matrix method" was proposed to calculate the PSD in breakage state of non-uniformly graded sample based on the PSD evolution functions of uniformly graded groups composing it.Others,the discrete element method(DEM)was used to study the distribution of particle breakage,the bond fracture form and the anisotropy in fracture orientation.Based on the simulated results,the relationship between the input energy,average contact force and breakage anisotropy magnitude was obtained by statistical method,which provides reference for studying the correlation of external load with respect to the microscopic characteristics of particle breakage.