Experimental Research On The Influence Of Particle Shape On Penetration Resistance Of Cone Penetration Test

With the in-depth implementation of my country's"Marine Power"strategy and steady progress in the construction of South China Sea Islands and reefs,a series of theoretical and engineering technical issues in the construction of islands and reefs urgently need to be answered.The determination of the foundation bearing capacity of coral sediments and the foundation of coral sediments Scientific and technological issues such as the evaluation criteria of the reinforcement effect and the evaluation of the resistance to liquefaction of the coral sediment foundation are all major core issues related to the stability of island reefs.The static cone penetration test(CPT)is an in-situ test technology with high test accuracy,good applicability and high repeatability.The test results have almost established a correlation with various engineering properties of terrestrial soil,so it has been more and more widely used in geotechnical engineering practice.The penetration resistance of static cone penetration will be affected by the relative density of the soil,the buried depth,the lateral pressure coefficient and the friction coefficient between the soil and the probe,and it is also related to the compressibility and shear strength of the soil.As an important attribute parameter of soil,the influence of particle shape on its macroscopic physical and mechanical properties has attracted more and more attention.Coral sand is the only type of foundation soil for island and reef buildings.It has the essential characteristics of irregular particle shape,brittle texture,and low density,which are different from conventional land-source sand.It is widely distributed in the South my country Sea.The existing research results on CPT are mostly for terrigenous sediments(quartz sand,etc.)^[14-15],while the CPT research results on coral sand are very limited.Up to now,it is not clear whether the penetration resistance of coral sand follows the similar regularity as that of terrestrial sand,and whether the research results on land origin can be directly applied to the evaluation of coral sand site foundation.The answer to this question is whether it is for marine engineering.The abundance and perfection of geological theory is a major scientific question that needs to be answered urgently for the construction of island and reef engineering.It is based on this that this article has carried out research on the influence of particle shape on the penetration resistance of static penetration.This research work uses a combination of indoor microscopic analysis,physical and mechanical tests,indoor model tests and theoretical analysis,and follows a step-by-step research route to reveal the influence of particle shape and stress state on static penetration resistance.First,select six sand samples with different particle shapes,including terrigenous siliceous quartz sand and calcareous coral sand,and use dynamic image scanning technology to obtain the three-dimensional morphological characteristics of uniform-grained sands of different shapes,and The statistical law of three-dimensional morphology parameters of sand particles is used to select a suitable morphology index system.The research results show that the use of particle shape parameters such as sphericity,roundness and aspect ratio to classify sand particles can obtain a more ideal result.Secondly,microscopic tests(CT Scan)and laboratory mechanical tests(dry density test,compression test,triaxial shear test)are used to study the influence of particle shape parameters on the physical and mechanical properties of soil.Studies have shown that the smaller the particle shape coefficient(p)of the established particle shape system,the smaller the pore radius,roar radius,and coordination number formed,the smaller the particle shape coefficient(p),and the smaller the shear strength parameters(friction and stickiness)the larger.Finally,a static cone penetration model test was carried out to study the influence of particle shape and stress state on the penetration resistance of static cone penetration.The research results show that the penetration resistance of the sample with the same particle shape increases with the increase in compactness.Increase,in the form of a linear function as a whole.Under the same density,the cone tip resistance of coral sand is greater than that of river sand,and the difference between the two tends to increase with the increase in density.