The Attenuation Law Of The Strength Of Red Clay During Dry And Wet Cycles Under The Action Of The Overburden

Red clay is widely distributed in China.With the development of traffic construction,many roads will pass through the red clay area.During the alternation of the rainy and dry seasons,the red clay undergoes an infinite number of dry-wet cycles of water absorption and dehydration.When used as embankment filler and slope,under the effect of seasonal dry-wet cycles,cracks are prone to dry-wet cycles.,Causing the roadbed to crack,slope instability,etc.,have caused certain harm to the project operation,affecting the economic and social benefits of the project.The main soil involved in engineering construction in Guizhou is red clay,which is often used in engineering fields such as foundations,highways,slopes,buildings,water conservancy,and railways.On the basis of previous studies on red clay,this paper studies red clay with a certain depth or overburden load in Guizhou.Taking the red clay of Guizhou University Phase II as the research object,and taking the soil mechanics as the theoretical foundation,the field research,laboratory tests,and theoretical analysis were conducted to study the wet and dry cycle attenuation laws of red clay under the overburden load.The research results are as follows:(1)The soil sample taken in this test is red clay,its natural density is 1.82 g / cm3? 1.94 g / cm3,its natural moisture content is 33.37% ? 37.49%,and its natural dry density is 1.35 g / cm3 ? 1.42 g / cm3.The liquid limit is 54%,greater than 50%,the plastic limit is 24.2%,the plasticity index is 29.8,and it is greater than 17,which belongs to clayey soil.It has the characteristics of high liquid limit,high plastic limit,high water content,and dispersibility.The optimal moisture content of the sample soil sample is 17.8%,the maximum dry density is 1.765 g / cm3,the non-uniformity coefficient is 31.58,and the curvature coefficient is 3.17.The red clay is poorly graded but has no effect on the test results;(2)The direct shear test without superimposed load and the direct shear test with superimposed load,their cohesion and internal friction angle gradually decrease with the increase of water content,and with the increase of compaction Gradually increase,and gradually decrease with the increase of the number of dry and wet cycles;(3)The cohesive force is significantly greater than the internal friction angle by the water content and compaction;(4)The shear strength index(cohesion C,internal friction angle ?)under the overburden load is greater than the shear under no overburden load under any same moisture content,compaction degree and number of dry and wet cycles Strength index,the shear strength index under the effect of overlying load is smaller than the shear strength index under the effect of no moisture load,compaction degree,and number of wet and dry cycles;(5)Under the same water content and same compaction degree,under the same external load,the shear strength index obtained in the triaxial test is greater than that obtained by the direct shear test;(6)Under the same water content,as the degree of compaction increases,the failure mode of the sample changes from a drum-like failure to an apparent failure surface;at the same compaction degree,as the water content increases,the sample failure form changes from the drum.The shape of the failure changes to the obvious failure surface.When the water content exceeds the optimal water content of 8%,the failure form is mainly bulging failure;The research results can provide more reliable technical support for road engineering construction in red clay areas.Accurate shear strength measurement indicators are conducive to reducing road hazards and extending the service life of roads to achieve improved economic benefits,which has certain engineering practical significance.