Summary:

Results of mechanical parameters of hornbeam (Carpinus betulus L.) originated from slope near Ciężkowice (Pogórze Ciężkowickie Mts.) are presented in the paper. In the frame of research were performed tensile force tests, were determined root area ratio within soil profile and shear strength tests of soil and reinforced soil were done. Tensile strength tests were carried out in the tensile testing machine manufactured by Hounsfield H50KS on samples with a length of 0.1 m using a strain speed of 10 mm per minute. Shear strength tests were performed in a direct shear box with measurements 120 x 120 mm for soil samples and soil reinforced by 6 and 10 roots of hornbeam. Results of tensile tests and their analysis revealed that hornbeam roots are very strong in comparison to some species of plants. Root area ration measurements show that the highest density of roots was observed in the upper superficial layer of soil profile (at the depth of 0,3 m below terrain level) and at the depth 1,0 m below terrain level were observed individual roots. Maximum value of root area ratio was equal to 0,6% and it was smaller in comparison to tests results obtained for this species cited in literature. Results of shear strength tests revealed that the increase of root area ratio within soil influenced on the increase of shear strength of soil, which was related mainly to the change of cohesion. The shear strength tests showed that at the root area ratio in the range 0,11-0,26% the increase of shear strength of soil due to root reinforcement was from 2,7 to 8,6 kPa.