Study On Interface Transition Zone Mechanical Properties And Damage Mechanisms Of Silt Lightweight Soil

Silt lightweight soil(SLS)is a new type of environmentally friendly soil,which has been widely used in foundation treatment,slope engineering and other fields.At the meso-scale,SLS can be regarded as a three-phase heterogeneous composite material composed of silt solidified soil,EPS particles,and interface transition zone(ITZ).The macroscopic failure mechanisms of SLS mainly depends on the mechanical properties of the mesoscopic threephase materials and their mutual coupling.Therefore,revealing the macroscopic damage laws based on the meso-scale has become an important research method.However,due to the complexity of the meso-structure and the special spatial location of ITZ,its mechanical properties are difficult to directly determine,which leads to the incompleteness of the material parameters of the meso-structure of SLS.And the uncertainty of the mechanical properties of ITZ will also significantly affect the research process of using the meso-model to reveal the macroscopic damage mechanisms of SLS.Therefore,determining the mechanical properties of ITZ is the basis for analyzing the macroscopic damage problem of SLS from a meso-scale scale,and revealing the damage mechanisms is also the key to ensuring the safe application of SLS in actual engineering.This paper conducts an in-depth study on ITZ mechanical properties and macro-micro damage mechanism of SLS based on Henan Province Natural Science Foundation(182300410100)"Study on the Multiphase Coupling Effect and Deformation Mechanism of Silt Lightweight Soil under Traffic Loading" and Henan Province Key Scientific and Technological Project(152102310082)"Study on Application of Sludge Recycled Materials Based on Lightweight Technology ".The main research contents and conclusions are as follows:(1)Based on the engineering application perspective,the influences of different mix ratios on the flow performance of SLS mixture were analyzed,the reasonable fluidity range was explored,and the fluidity prediction function was proposed.Then,in order to provide experimental basis for the mesoscopic studies of SLS in this paper,the physical and mechanical parameters of each phase material of the SLS were measured by indoor triaxial tests and uniaxial compression tests.Based on the test results,the factors influencing the strength of SLS and the macroscopic damage modes were analyzed.(2)Combining the actual meso-structure characteristics of SLS and particles interference theory,an improved three-phase meso-model of SLS was established.Compared with previous models,the established model not only has better accuracy,but also achieves a higher EPS delivery rate.The three-phase model algorithm and the creation process of the ABAQUS model were integrated into a secondary development program,and the GUI was created for the program.By entering the corresponding parameters of the model in the GUI,the batch calculation of the meso-models can be realized.The research provides a rapid solution for a large number of numerical simulation works carried out in this paper.(3)Based on the meso-three-phase model and the laboratory test data,the mechanical parameters of ITZ were derived by using the parameter inversion and numerical simulation method,and the meso-deformation mechanism of ITZ and its influence on the macroscopic strength were also quantitatively analyzed.The results are as follows: In terms of strength,the strength of ITZ is about 60%-70% of that of the silt solidified soil.Affected by the weak mechanical properties of ITZ,the strength of SLS will lose about 15%-30%.In terms of deformation,the strain response speed of ITZ to external loads is faster than that of EPS particle.In the same sample,the strain of ITZ at the lower part of the soil was obviously lagged behind the upper part.(4)Based on the complete meso-structural parameters,the three-phase meso-model and numerical simulation method were used to systematically study the meso-damage laws and damage mechanisms of SLS.And an improved damage constitutive model which is more in line with the failure law of SLS was proposed.The results are as follows: the cracks initiation position of SLS are random,but they all occure on both sides of SLS.After the cracks initiation,the propagation paths are different under different confining pressure and EPS content.The crack development rate is also different between different materials.Considering that the previous damage constitutive models cannot describe the characteristic that SLS has residual stress after complete damage,an improved whole-process damage constitutive model is proposed.This model has fewer parameters and is more suitable for practical engineering applications than similar models.