根土复合体抗剪特性变化特征及强度预估研究

Study on the Change Characteristics of Shear Resistance and Strength Prediction of Root Soil Composite

根土复合体剪切特性受含根量与压实度的影响,为探究二者对根土复合体抗剪特性的影响程度,以黑麦草根土复合体重塑试样为研究对象,进行了不同含根量(0%、0.15%、0.3%、0.45%、0.6%)与不同压实度(85%、90%、95%)的根土复合体三轴压缩试验,分析了15%应变对应的极限主应力差与抗剪强度指标的变化规律,建立了抗剪强度计算公式。结果发现:①在相同围压下,根土复合体的极限主应力差相比于素土增加了6~79.9kPa,增幅为6.8%~65.5%。②压实度相同时,随着含根量的增加,根土复合体极限主应力差先增加后减小,压实度为85%、90%、95%时在含根量为0.3%、0.3%、0.45%时极限主应力差最大,即为最优含根量。③基于试验结果,建立了同时考虑含根量、压实度和围压的根土复合体抗剪强度计算公式,公式的拟合精度(R2)为0.943。采用原状土根土复合体试样对公式进行验证,发现公式的预测精度(R2)为0.96。研究结果为黑麦草根系固土提供理论依据。

The shear properties of root soil complex are affected by root content and compactness.In order to explore the extent of their impact on the shear properties of root soil complex,the triaxial compression tests of root soil complex with different root content(0%,0.15%,0.3%,0.45%,0.6%)and different compactness(85%,90%,95%)are carried out with the ryegrass root soil composite body weight plastic sample as the research object,The variation rule of ultimate principal stress difference and shear strength index corresponding to 15%strain is analyzed,and the shear strength calculation formula is established.The results show that:①under the same confining pressure,the ultimate principal stress difference of root soil composite increases by 6~79.9kPa,6.8%~65.5%,compared with that of plain soil.②At the same compactness,with the increase of root content,the ultimate principal stress difference of the root soil composite increases first and then decreases.When the compactness is 85%,90%and 95%,the ultimate principal stress difference is the largest when the root content is 0.3%,0.3%and 0.45%,which is the optimal root content.③Based on the test results,a formula for calculating the shear strength of root soil composite considering root content,compactness and confining pressure is established,and the fitting accuracy(R2)of the formula is 0.943.The formula was verified with undisturbed soil root soil composite sample,and it was found that the prediction accuracy(R2)of the formula was 0.96.The results provide a theoretical basis for ryegrass root system soil fixation.