Macroscopic Properties And Microstructure Of Compacted Weathering Granite Soils In Southeastern Of Guangxi And Analysis Based On Fractal

Granite residual soil and fully weathered granite is abundant in the humid Tropics of southern China.It has been used extensively as fill materials in various application s,such as back-filling materials for pavements.Some subgrade diseases relate to the compaction degree and the moisture content of compacted granite residual soil.On the basis of analyzing the characteristic of granite residual soil of Southeast Guangxi Pro-vince,a series of direct shear tests are carried out on compacted samples with three moisture contents?optimum moisture content of the standard compaction test,on the wet side of the optimum moisture content,and on the dry side?.Then,the microstruc-ture of and fabric characteristics of these compacted samples were analyzed by scanni-ng electron microscope and mercury intrusion pore size distribution measurements.The experimental results show that:?1?The experimental results show that the there sam-ples have same stress-strain curve shapes with no pronounced peaks.The optimum sa-mple has the highest shear strength,the three samples have nearly equal internal frict-ion angle,the optimum sample has the highest cohesion,Cohesion of the wet sample and the dry sample decrease by 66.4%and 43.1%,respectively;?2?The wet sample h-as aggregate structure and open structure and exhibits a doublet pore-size distribution with highest cumulative pore volumes;while the optimum sample has a matrix struct-ure with parallel alignment of mineral grains;The dry sample has a piece frame stru-cture with the smallest cumulative pore volumes.?3?The whole weathered granite in the three kinds of compaction state has obvious peak and strain softening;And strain softening phenomenon is gradually obvious with the decrease of the moisture content;For shear strength,the largest is in the optimum moisture content,and the dry side s-tate is slightly greater than the wet side state;Besides,?_optimal>?_stem>?_wet,c_optimal>c_stem>c_wet;The change of c value is more sensitive than?values with various dry and wet state relatively;?4?The whole weathered granite universally forms a complex body i n the wet side,and its fabric is turbulent.In the fabric and the optimum moisture con-tent condition,due to breakage of fine particles and pores more,in the condition of dry side fabric homogeneously loose,the porosity of the lateral side of wet and dry s t-ate assumes the bimodal distribution characteristics is best;?5?The microscopic featur-es of the three compacted samples are explained the difference of the shear strength accurately.In addition,the mechanical properties and microstructure properties of each comp-action state are studied in this paper.Finally,fractal theory is introduced to fractal the grain size and pore distribution of weathered granite in different compaction states,an-d the fractal dimension of particle size and pore distribution is obtained.The mathemat-ical relationship between fractal dimension and macroscopic properties is established,and its correlation is analyzed,and the mechanical properties and permeability of wea-thered granite are described quantitatively.