Experimental Study On Engineering Properties Of Limestone Stone Mixture And Gravel Mixture

The Technical Specification for High Filling Engineering for Civil Airports?MHT5035-2017?proposes a new classification scheme for fillers.In this classification,particles of>60 mm are not more than 50%,and fillers of<2 mm of particles not exceeding 50%are defined as"earth stone mix",further divided by two P5 content limits?30%and 70%?.There are three sub-categories of“earth mixture”,“gravel mixture”and“stone mixture”.At present,little research has been done on the engineering properties of earth and stone mixtures in this classification system.In view of this,relying on the three-level sub-topic of the National Key Basic Research and Development Program?973 Program?under the tutor's responsibility,the“gravel mixture”and“stone mixture”are selected as the research objects,and the limestone blasting slag is selected.According to the principle of continuity and transition,a series of graded packings were prepared,and a systematic test was carried out under95 compaction(including 12 sets of heavy compaction,12 sets of penetration,16 sets of confined compression,6 sets of large Three-axis and six-group large ring shears were analyzed.The engineering properties and influencing factors of the two types of fillers were analyzed and the classification limits of the two types of fillers were discussed.The main conclusions obtained are as follows:?1?The P₅ content has control significance on the engineering properties of the two types of earth and stone mixture.Under certain P₅ content,the P_2-5 content change has certain influence on the engineering characteristics.When P₅=80%,the maximum dry density,permeability coefficient,lateral compression modulus,and internal friction angle all change or turn.The P₅ content at the transition or the turning point of the filler engineering property is higher than that of Guo Qingguo?P₅=70%?.In the preliminary analysis,the reason for the difference may be that when P₅ is higher?75-80%?,an increase in P_2-5 content will increase the skeleton effect.?2?The granularity characteristics of the fillers were expressed by the fractal dimension D.The results show that the fractal dimension of the particles before compaction has a good correlation with the fracture rate.The maximum dry density characteristics of the two types of fillers are analyzed by Alfred compact packing theory.The two types of fillers are considered together.According to the factor analysis,the maximum dry density of the two types of earth-rock mixtures is mainly related to P₅ content,uneven coefficient C_u,particle size fractal dimension D,characteristic particle size,etc.?3?By considering the two types of fillers in a unified way,the main influencing factors of the permeability,compressibility and shear strength characteristics of the two types of earth-rock mixtures under 95 compaction were obtained.After multiple regression analysis,a unified expression was established.Empirical relationship of engineering properties of filler-like materials.?4?The relationship between the mechanical properties and porosity of the two types of earth-rock mixtures has obvious differences:the gravel mixture increases with the initial dry density?_d?the porosity n decreases?,the internal friction angle?and the lateral compression modulus E_s Increase;the stone mixture,as the dry density increases?the porosity n decreases?,the internal friction angle?does not change significantly,and the confining compression modulus E_s decreases slightly.?5?According to the research results of this paper and previous studies,combined with the actual changes of P_2-5 content in airport fillers,the preliminary proposal for adjusting the P₅ limit content of two kinds of earth and rock mixture is proposed,which is adjusted from the original P₅=70%to P₅=75%.?6?According to the test results of this paper,according to the classification of civil aviation?P₅=70%?,the suggested values of the parameters?range?of the two types of limestone soil and stone mixture under 95 compactness are given.At the same time,according to the limit content recommended in this paper?P₅=75%?,the corresponding?range?parameter suggested values are given.