Study on the Plant Roots to Improve Shear Characteristics in Coal Mining Subsidence Area

In this paper, we investigate the influence on shear strength of the roots of four typical plants which can fix the soil in coal mining subsidence area by direct shear tests ,and the shear strength of the root soil composite .The results indicate that with the same root diameter (1.25 mm) , Sabina valgsris Ant., Salix psammophila, Caragannmicrophylla Lam. Artemisia sphaerocephala Krasch are more intensive than pure soil within the buried depth of 1.5 m(25 kPa),and the order of shear strengths of these composites at the depth of 0.8 m(12.5 kpa) from the earth´s surface is Salix ossammophilia > Sabina valgaris Ant. > Caragana mierophylla Lam. > Artemisia sphaerocephala Krasch .Within the range of one level away from the representative standard root diameter, the shear strengths of the four types of root soil composites increase differently with the increase of the root diameter. When its cross-sectional area of the roots in the sample is fixed, the shear strength of the root-soil composite of Caragana microphylla Lam increase with the increase of the number of the roots. When the roots have different directions, the difference between the shear strengths of different Caragana microphylla composites is 45degreverse root distribution>90degvertical root distribution> 45deglateral root distribution> 45degforward root distribution.