Experimental Research On Fracture Characteristics Of Compacted Clay

The fracture toughness of soil is often too small to be measured easily,and it has little effect on the actual engineering,therefore,it is often neglected.However,with the increasing engineering scales and complexity,it is necessary to study the characteristics of soil fracture because of the more and more fracture-related problems such as dam accidents,slope instability,and ground cracks.The study will not only improve the soil strength theory,but also has important values for actual engineering.There has been no uniform instrument and operating procedure for the measurement of soil fracture toughness yet.A new piece of apparatus has been developed to measure the soil fracture toughness in this thesis,with which a lot of soil samples with various dry densities,water contents,and coarse particle contents were tested.Based on the experiment results,the following can be concluded.(1)The new strain-controlled apparatus can be effectively used to measure the soil fracture toughness,and the corresponding mold can be used to prepare reliable samples.The experimental results have good stability.(2)When the dry density is constant,the fracture toughness of unsaturated cohesive soil does not change with the various water contents linearly.When the dry density is relatively small,the fracture toughness of soil first increases and then decreases with the increasing water content,and there exists an optimum moisture content at which the maximum fracture toughness is reached.When the dry density is relatively great,however,the soil fracture toughness decreases with the increasing water content.(3)When the moisture content is constant,the fracture toughness increases with the increasing dry density,and there is an approximate linear correlation between them.(4)In the experimental design,the greater the coarse grain content,the smaller the fracture toughness.