Study On 3D Modeling And Unconfined Compressive Strength Characteristics Of Air-foam Treated Lightweight Soil

Air-foam treated lightweight soil is a new type of lightweight geotechnical material formed by fully mixing and mixing raw material soil,cement,water and air bubbles in a certain proportion.It is light and flowable in terms of pipeline backfilling and abutment backfilling.It has been used in pipeline backfilling and abutment backfilling due to its light weight,flowability and self-supporting advantages.Existing studies on the physical and mechanical properties of air-foam treated lightweight soil mostly use experimental methods.Due to the characteristics of high porosity,small pore size and randomness,it is still difficult to carry out three-dimensional numerical simulation analysis for porous materials such as air-foam treated lightweight soil.This paper first studied the pore characteristics of air-foam treated lightweight soil through experiments,and then researched and proposed a three-dimensional modeling method suitable for air-foam treated lightweight soil.Finally,the unconfined compressive strength characteristics of air-foam treated lightweight soil were analyzed with ABAQUS.The main work and results are as follows:(1)The pore characteristics and unconfined compressive strength characteristics of air-foam treated lightweight soil were studied through laboratory experiments.The result shows:when the density of air-foam treated lightweight soil is between 0.6g/cm~3～1.0g/cm~3,its porosity is between 60%and 80%;under the same density,the greater the ratio of water to solid mass used in the mixing ratio,the greater the porosity of the air-foam treated lightweight soil.The pore size of the air-foam treated lightweight soil is distributed in the range of 0.1mm～0.5mm,of which the pore size of 0.1mm～0.2mm accounts for 43%.The stress-strain relationship of the air-foam treated lightweight soil is related to the cement content and the compactness of the sample,showing three forms of hardening,softening and brittle failure.(2)Research on the three-dimensional modeling method for porous materials with high porosity and small pore size is carried out,and the"fill-in type","layered type"and"layered continuous type"that meet the characteristics of strong random pore distribution,high porosity and small pore size are proposed.It solves the problem of Boolean operations reporting errors due to too many model points,lines and surface features in the process of porous material modeling,and improves the maximum porosity that can be achieved by the model.For porous materials with a porosity of less than 60%and a relatively concentrated pore size distribution,the use of a"fill-in"model for modeling can reduce the amount of calculation and effectively improve the modeling efficiency;for porous materials with a porosity greater than 60%,the pore size with a wide range of distribution can be modeled using"layered"and"layered continuous"models.(3)Based on the"layered continuous"modeling method,the unconfined compressive strength characteristics of the air-foam treated lightweight soil were numerically simulated and analyzed using ABAQUS software.The result shows:the unconfined compressive strength of air-foam treated lightweight soil has a negative correlation with porosity.Under the same porosity,the“uniform”distribution of the internal pores of the air-foam treated lightweight soil has higher unconfined compressive strength than the“random”distribution of the pores,but as the porosity increases,the difference between the two is getting smaller and smaller.Under the same porosity,the larger the pore size,the lower the strength of the air-foam treated lightweight soil,and the decrease in strength with the increase of the pore size is more obvious under high porosity.The air-foam treated lightweight soil will undergo shear failure along the surface where the thickness of the pores is small and the number of large pores is large.