灌区渠基土改良下力学试验及冻胀特征研究

Mechanical Testing and Freeze-thaw Characteristics of Canal Bed Soil Modification in Irrigation Districts

为评估分布黄土改良治理效果,以黄土渠基为试验对象,设计了木质素改良下黄土力学试验,并基于此开展黄土干渠衬砌结构冻胀仿真计算。由试验结果得知,木质素成分含量高或低,均不会改变改良土试样应变破坏特点,但木质素含量提高,改良土应力水平会增大,但在掺量3%后提高效果会减弱。相比之下,含水率因素会改变改良土试样应力应变曲线特征,在含水率14%~18%与20%~22%下分别为应变软化、应变硬化特点;含水率提高,峰值应力降低,而围压增大,可减弱含水率对改良土承载应力的负面作用。基于冻胀仿真计算,获得了原状渠基土与改良黄土衬砌结构冻胀位移在断面上均为对称分布,峰值冻胀位移处于断面1 m处,且改良黄土衬砌结构冻胀位移值低于原状渠基土,经改良后渠基土受含水率影响冻胀危害弱于后者。本研究可为输水灌渠土体物化治理设计及冻胀仿真计算提供参考。

In order to evaluate the effectiveness of distributed loess improvement measures,taking loess canal foundation as the test object,the mechanical test analysis of loess under lignin modification is designed,and based on this,the frost heaving simulation of loess trunk canal lining structure is carried out.The test results show that varying lignin content did not change the strain failure characteristics of the modified soil sample.However,an increase in lignin content led to an increase in stress level in the modified soil,although this effect diminished after a 3%dosage.On the other hand,moisture content influenced the stress-strain behavior of the modified soil specimens,exhibiting strain softening characteristics at moisture contents of 14%to 18%and strain hardening characteristics at moisture contents of 20%to 22%.Increasing moisture content reduced peak stress while increasing confining pressure,thereby mitigating the negative impact of moisture content on the bearing stress of the modified soil.Freeze-thaw simulations revealed that both the original canal bed soil and the modified loess lining exhibited symmetric distribution of freeze-thaw displacements along the cross-section.The peak freeze-thaw displacement occurred at a distance of 1 meter from the cross-section,with the modified loess lining experiencing lower displacements compared to the original canal bed soil.Furthermore,the modified canal bed soil demonstrated a lower vulnerability to freeze-thaw damage influenced by moisture content compared to the original soil.This research provides valuable insights for the design of physical and chemical treatments for irrigation canal soils and for freeze-thaw simulation calculations.