沙地柏根系径级对根土复合体抗剪强度的影响

采用应变控制式直剪仪,通过对含不同沙地柏根系径级的扰动土进行室内直剪试验,分析研究根土复合体的抗剪性能。结果表明沙地柏根系的加入,增强了土体的抗剪强度,且根土复合体的抗剪强度符合库伦定律;当所含根系径级小于某个极限值时,根土复合体的抗剪强度随着径级的增大而增大,当超过这一极限值,则随着所含根系径级的增大,其抗剪强度逐渐减小,随着根系径级的逐步增大,由于根自身抵抗土体剪切变形能力增强,使得根土复合体的抗剪强度值开始回升;一定竖向荷载下,根土截面比△过小,对复合体抗剪性能影响微弱;根土截面比过大,根系与土壤胶结力降低,对抗剪强度产生负影响,因此,存在一个最佳根土截面比,在此比值附近,根土复合体的抗剪强度达到最大。本研究可为沙地柏在作为水土保持树种栽植方面提供理论依据。

The Effect of Root Diameter of Sabinavulugaris on the Shear Strength in Root-Soil Composites

In this paper,using the direct shear apparatus,the shear strength of soil-root composites containing different diameter roots of Sabinavulugaris was researched.The results showed that the colonization of Sabinavulugaris roots increased soil shear strength and shear strength of soil-root composites accorded with Coulomb’s law.As the diameter of root contained was lower than a threshold,the shear strength of soil-root composites increased as the diameter increased.When over the limit,the shear strength of soil-root composites decreased as the diameter increased.With the gradual increase of root diameter,the resistance capacity of root to the shear increased and made the shear strength values of soil-root composites begin to rise.Under certain vertical load,if the root soil cross-section ratio is too small,the root influenced Shear strength of composites weakly;if the root soil section ratio was too large,the cement between root and soil was reduced,and roots had a negative influence on the shear strength.Therefore,there was an optimum soil root cross-section ratio,and when the root soil cross-section ratio was near to the optimum value,the shear strength of the root soil composite reached to the maximum.This study could provide a theoretical basis for Sabinavulugaris plantation in the soil and water conservation areas.