Effect Of Dry Density And Water Content On The Stregth And Strength Parameters Of Remolded Loess In Taiyuan

With the development of the cities in the loess area of China,more and more shallow soil layers have become the object of engineering activities.However,the large area of Shanxi is distributed with a deep loess layer,which has naturally become the main resource of engineering construction.Because of the special nature of the loess,it is easy to cause the hidden danger of the quality of the project if it can not make a thorough understanding of its engineering characteristics.Therefore,it is very important to study the strength and strength parameters of the loess.In view of this,this paper takes the disturbed soil of foundation ditch in a construction site in Taiyuan,Shanxi as the research object.The indoor compaction test is carried out after the basic physical characteristics are understood.The change of dry density value of loess samples under different water content and different compaction work is studied,and the maximum dry density and optimum water content of the specimen are determined.Then,the Taiyuan remolded loess samples with different dry density and different water content obtained by pre wet method and air drying method were subjected to fast shear tests under 4 vertical pressures respectively.The shear strength and strength parameters c and?value of the sample are obtained,and the study is further carried out.Finally,the Unconsolidated undrained triaxial tests of Taiyuan remolded loess samples with different dry density and different water content are carried out under 3 kinds of confining pressure.The influence of dry density,water content and confining pressure on the stress-strain relationship of loess specimens and its reasons are analyzed.The factors affecting the shear strength,strength parameters and extreme partial stress of the remolded loess are studied.According to the data obtained from laboratory compaction test,the dry density of loess samples under the same compaction power always increases with the increase of water content and then decreases,and in the same water content,dry density increased with the increase of loess compaction increases.The dry density of the Loess specimen under low water content is more significant with the increase of compaction work.It is obtained from the direct shear test that the moisture has a weakening effect on the strength of the loess.Under the same water content,the slope and intercept of the strength cladding always become larger with the increase of dry density.The c and?values of the strength parameters of the loess samples gradually decrease with the increase of water content,and the greater the dry density,the stronger the sensitivity to water.There is a relationship between the cohesive force and the water content of the loess samples with exponential functions,and there is a linear function between the internal friction angle and the water content.The c and?values of the strength parameters always increase approximately linearly with the increase of dry density.And for cohesive force,the range of the sample with small water content is more significant with the increase of dry density.And through the function relation between value of c,?and water content and dry density of specimen,Mohr-Coulom shear strength formula is expressed as an expression containing the parameters of direct stress???,water content???and dry density??_d?.According to the triaxial test,the??₃-₁^??^?₁curves of loess samples gradually change from weak hardening to strong hardening,with the increase of water content,the increase of confining pressure and the decrease of density.The c and?values of loess samples are obtained by linear fitting through the relationship of the Loess specimens at the limit equilibrium??₃-₁^??^?₁.It is concluded that the ultimate stress of loess increases with the increase of confining pressure and dry density in the loess sample.The increase of water content makes the ultimate stress of the Loess specimen decrease.The shear strength??_f?and normal stress???of the triaxial test are compared with the obtained values of the fitting function to verify that the data obtained from the fitting function is in the acceptance range.By comparing the strength parameters c??obtained from triaxial tests with those obtained from direct shear tests.It is found that whether cohesive force c or internal friction angle?,the value obtained from triaxial test is always greater than that of direct shear test.