Abstract: The strength of loess soils has always been the key aspect of the loess laboratory tests. The moisture content, dry density, soil pressure and other tests are the basic testing closely related to the loess strength values. To quantify the contribution of potential influencing factors to the loess strength, Taguchi method is used to estimate the signaltonoise ratio (SNR) and analyze the variance of each influencing factor on the basis of the direct shear test. The results show that the normal pressure and the dry density are positively correlated with signaltonoise ratio, while the moisture content is negatively correlated. Through the analysis of variance, the maximum effect of the normal pressure is 77.55%, the moisture content is the second, and the lowest dry density is 7.80. Considering the interaction of influence factors, the maximum effect of the moisture content and the normal pressure on shear strength is 55.7%. On the unsaturated loess, the pressure on the soil and the moisture content of the soil are the main influencing factors of the strength of the saturated soil. In the prevention of the loess landslide, although the surcharge load at the foot of the slope and the pressure relief at the top of the slope are the effective measures to prevent the occurrence of the landslide, the drainage of the soil cannot be ignored. 

Key words: Shear Strength, Taguchi method, Analysis of Variance, Contribution Rate