Experimental Researches On Size Effect Of Raw-soil Based Materials Compressive Strength

Raw soil base material has many advantages such as green,environmental protection,low energy,low cost and so on.Raw soil base material still has a wide range of applications.But the research of the materials still stay in traditional craftsmen experience stage.Construction materials testing is short of a system specification.Therefore establishing standard test method for raw soil base material is extremely urgent.Material compressive strength is an important mechanics index.Material mechanical properties of the specimens can indirectly reflect the actual mechanical properties of raw soil buildings.After extensive research,we selected typical loess as the basic material.Based on the raw soil base cube compressive strength test specimens,we studied different sizes of raw soil base material failure pattern,load-displacement curve,compressive strength,the discreteness of data,etc,which provided the reference standard test method for raw soil base material standard size research,established data basis of the raw soil material constitutive theory and material strength design value and standard value research,maked contributions to perfect our raw soil building materials industry standards and promote the diversified development of raw soil technology in China.The study found that the size,the greater the specimen making more cumbersome,specimen of finished product is higher,the breakage exfoliation fall off,such as initial defects,the more obvious.By observing the specimen failure pattern,we found thatThis paper took xi ’an changan district of loess for the production of raw materials raw soil base cube block.According to《Soil test method standard》(GB/T50123-1999),the optimal moisture content was 18.12%,the maximum dry density of 2.04 g/cm3.Under the moisture content,we maked 70.7 mm,100 mm,150 mm and 200 mm group a total of 190 specimens with different dimensions,and carried on the uniaxial compressive strength tests.The failure pattern,failure process of the specimens,paths of the load-displacement curve were obtained by the axial compression test,analysised the main factors of raw soil base material mechanical performance.Through the observation we found that raw soil specimen failure pattern is eventually waist shape.By observing the normalized load-displacement curve of the specimens,we found that raw soil load-displacement curve of the specimens is roughly consistsed by 4 segments which include concave section,linear growth period,nonlinear segments,descending branch and so on.Though univariate analysis of variance,we we found that raw soil specimen size of raw soil base has significant effects on the compressive strength of the specimens.Through the analysis of different size specimen size effect degree of the compressive strength of worth,as the specimen size bigger,specimen size effect value of compressive strength,the compressive strength,the more obvious size effect phenomena.Considering compressive strength of the specimens,discreteness,size effect and specimen made numerous easy degree and the influence of specimen factors such as initial defects,this paper suggested to choose the standard size 100 mm as standard test specimens.By comparing the same size under different loading rate on compressive strength of the specimens,the influence of the discreteness,this paper recommended 1 mm/min-3 mm/min loading rate as a standard test of loading rate.